A posteriori” modification of carbosilane dendrimers and dendrons: their activation in core and branch positions

Arno Tuchbreiter ab, Helmut Werner b and Lutz H. Gade *a
aAnorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany. E-mail: lutz.gade@uni-hd.de
bInstitut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany

Received 31st January 2005 , Accepted 3rd March 2005

First published on 15th March 2005


The introduction of phenyl groups at different points on carbosilane dendrimers allows their acidolytic conversion to highly reactive triflato groups which in turn are readily substituted by anionic nucleophiles. Core phenylated first–fourth generation dendrimers were synthesized from tri(allyl)phenylsilane by an alternating sequence of hydrosilylation and allylation steps. Similarly, carbosilane dendrimers containing phenyl-Si groups at the branching points and in the periphery were prepared from tetraallylsilane which was hydrosilylated with PhHSiCl2. Reaction of the phenylated dendrimers with triflic acid in toluene cleanly gave the silyl triflate derivatives, provided that the correct stoichiometry of the reagents was used. In the presence of a large excess of triflic acid the SiMe3-end groups are slowly converted to SiMe2(OTf)-units. The proof of concept was provided by the fixation of a {Ph2PCH2} group using the lithiated diphenylphosphinomethanide Ph2PCH2Li, obtained by cleavage of Ph3SnCH2PPh2 with PhLi, as well as a lithiated ether-alcohol functionalized triphos derivative to the core of a third generation carbosilane dendrimer.


Introduction

Among the many known classes of dendrimers which have been developed during the past 2.5 decades,1 dendritic carbosilanes were found to be particularly suited as platforms for further functionalization.2 This is due to their high kinetic and thermodynamic stability and the low polarity of the Si–C bond. This inertness has even enabled the selective oxygenation of the end groups in carbosilane dendrimers with H2O2 and wide diversity of types of functionalization even under harsh reaction conditions.3

The first carbosilane dendrimer was reported as early as 1978 by Fetters and co-workers,4 however, the field really opened up in the 1990s after the seminal contributions by van der Made and van Leeuwen et al.,5 Roovers et al.,6 Muzafarov et al.7 as well as from Seyferth's group.8

The aim of this work was the possibility of selectively functionalizing carbosilane dendrimers in the core, the branching units and at end groups subsequent to their divergent synthesis. The key step in the growth sequence is the hydrosilylation of olefinic end groups, a catalytic reaction which is not very tolerant towards functional groups. It was thus desirable to convert relatively inert molecular fragments to highly reactive functionalities within the dendrimer structure. A well established method of functionalization in carbosilane chemistry is the cleavage of Si-phenyl units by strong mineral acids, in particular trifluoromethansulfonic acid.9 While frequently employed in the synthesis of “simple” silicon compounds this method has not been used in dendrimer chemistry.

ugraphic, filename = b501069a-u1.gif

The strategy is thus straightforward: introducing phenyl groups at different points of a carbosilane dendrimer as “dummy” functions which can be selectively converted to highly reactive triflato groups which in turn are readily substituted by anionic nucleophiles. To which degree dummy functions in topologically different environments are completely convertible to triflates was a practical question to be resolved in this study. Finally, we were interested in establishing the possibility of using these activated dendrimers for the immobilization of phosphine ligands, which may be employed in catalytic applications of these systems.

Results and discussion

Synthesis of G1–G4 carbosilane dendrimers containing a PhSiR3 core

The syntheses of the core phenylated first–fourth generation dendrimers 110 were carried out according to the method established for carbosilane dendrimers by Roovers, van Leeuwen and Seyferth.5,6,8 As the core molecule we chose tri(allyl)phenylsilane from which the dendrimer growth was achieved by an alternating sequence of hydrosilylation and allylation steps (Scheme 1).
Synthesis of the G0–G3 carbosilane dendrimers 1–7, 8, 9 containing a PhSiR3 core.
Scheme 1 Synthesis of the G0–G3 carbosilane dendrimers 17, 8, 9 containing a PhSiR3 core.

The hydrosilylations were carried out in benzene using Karsted's catalyst which avoided the formation of possible regioisomers. The chloroterminated carbosilanes were then reacted with (allyl)MgBr giving the next-generation dendrimers containing allyl end groups. While compounds 36, which were employed as branching elements in composite polymers with polyolefins, have been reported previously,10 they remained incompletely characterized. The final step in the dendrimer synthesis was the methylation of the end groups using MeMgCl (Scheme 2).


Methylation of the SiMeCl2 end groups of the G2 and G3 carbosilane dendrimers 6 and 9.
Scheme 2 Methylation of the SiMeCl2 end groups of the G2 and G3 carbosilane dendrimers 6 and 9.

The third- and fourth-generation core-phenylated dendritic carbosilanes 7 and 10 were the objects of study in the subsequent acidolytic activation and functionalization steps.

Synthesis of carbosilane dendrimers containing phenyl-Si groups at the branching points and at the periphery

With the aim of synthesizing a carbosilane dendrimer which is phenylated both at the branching points as well as the end groups, tetraallylsilane11 was hydrosilylated with PhHSiCl2 giving compound 11 (Scheme 3). In the 1H NMR spectrum of the compound the outer methylene groups of the propylene units resonate as triplets at δ 0.58 and 1.35 ppm, the latter being assigned to the protons adjacent to the SiPhCl2 groups, while signal of the CH2-group in the middle is observed as a multiplet at δ 1.46–1.77. The 13C NMR signals are observed at δ 15.8, 17.3 and 24.9 ppm. The 29Si nucleus at the core position resonates at δ 1.5 ppm whereas the peripheral SiPhCl2 groups give rise to a 29Si NMR signal at δ 18.3 ppm.
Synthesis of the carbosilane dendrimers 11–14 containing phenyl-Si groups at the branching points and in the periphery.
Scheme 3 Synthesis of the carbosilane dendrimers 1114 containing phenyl-Si groups at the branching points and in the periphery.

Reacting 11 with allylmagnesium bromide in thf giving compound 12 and a subsequent further hydrosilylation step with PhHSiCl2 yielded the first-generation dendrimer 13 which was subsequently methylated with MeMgCl in THF to give Si[CH2CH2CH2Si(Ph)[CH2CH2CH2Si(Ph)Me2]2]4 (14) (Scheme 3) which was characterized, similar to the other compounds, by elemental analysis, 1H, 13C, 29Si NMR and IR spectroscopy, as well as FAB mass spectrometry.

Acidolytic cleavage of the phenyl-Si groups in dendrimers with triflic acid giving triflato-Si core units

The acidolytic cleavage of the core-phenylated carbosilane dendrimers was carried out using compounds 2, 7 and 10 (Scheme 4). Reaction of carbosilane 2 with three molar equivalents of triflic acid in toluene cleanly gave the silyl triflate derivative (a complete cleavage of the Si-phenyl unit could also be achieved with one molar equivalent of triflic acid albeit at a much slower conversion rate). The quantitative conversion could be readily followed by 1H NMR spectroscopy which showed the absence of the phenyl resonances at the end of the reaction. The chemical shift of the other resonances of the reaction product 15 differed only slightly from those of 2. In the 13C{1H} NMR spectrum a quartet resonance at δ 118.4 ppm is observed which is due to the CF3-group of the triflate.
Acidolytic cleavage of the core phenyl-Si groups in PhSiR3 dendrimers with triflic acid giving triflato-Si core units.
Scheme 4 Acidolytic cleavage of the core phenyl-Si groups in PhSiR3 dendrimers with triflic acid giving triflato-Si core units.

As for the first-generation dendrons 2 and 15, the 1H, 13C and 29Si NMR spectra of the third- and fourth-generation products 16 and 17 closely resemble those of the phenylated starting materials 7 and 10, with only the signals of the phenyl groups being absent. The shift of the resonances in the 29Si{1H} NMR spectrum of δ −3.8 ppm for 7 to δ 39.7 ppm for 16 and from δ −3.8 ppm for 10 to δ 39.8 ppm for 17 indicates the substitution of the core phenyl unit by a triflato function.

In order to obtain high selectivities in the acidolytic cleavage it is important to closely observe the correct stoichiometry of the reagents. In the presence of an excess of triflic acid the SiMe3-end groups are slowly converted to SiMe2(OTf)-units. To study this side reaction we exposed compound 2 to a tenfold excess of the acid, which not only led to the cleavage of the core-phenyl group but a complete and clean conversion of all three SiMe3 termini to dimethylsilyltriflato units giving compound 18 (Scheme 5). Following the reaction by 1H NMR spectroscopy showed that the phenyl group is very rapidly eliminated with a subsequent slower cleavage of the Si–CH3 bonds.


Acidolytic cleavage of the core phenyl-Si group in 2 and conversion of the SiMe3 end groups into SiMe2(OTf) groups in the presence of a large excess of triflic acid.
Scheme 5 Acidolytic cleavage of the core phenyl-Si group in 2 and conversion of the SiMe3 end groups into SiMe2(OTf) groups in the presence of a large excess of triflic acid.

The selectivity of this reaction is remarkable in that only one methyl group per SiMe3 unit is cleaved in spite of the large excess of the acid. This is due to a significant decrease of electron density at the silicon atom upon replacement of a CH3 group by the triflate thus deactivating this position with respect to further acidolytic transformations, a behaviour which has been previously noted in silicon chemistry.9b The subsequent reaction step therefore occurs at a different SiMe3 unit in the periphery.

A controlled and rapid acidolytic transformation both at the branching points and the end groups was achieved by reaction of the phenylated first generation dendrimer 14 with 12 equivalents of triflic acid, cleanly giving the dodecatriflate 19 (Scheme 6). In the 1H NMR spectrum of compound 19 all signals are shifted to lower field due to the introduction of twelve electronegative triflato groups, while there is a complete absence of phenyl resonances. The same general trend is observed in the 13C{1H} NMR spectrum of the compound. The synthesis of 19 clearly demonstrates the versatility of the acidolytic modification of phenylated dendrimers which is feasible in the core, branching and endgroup positions of a dendritic carbosilane.


Acidolytic cleavage of the phenyl-Si groups at the branching points and in the periphery of 14 giving the highly reactive triflato-Si derivative 19.
Scheme 6 Acidolytic cleavage of the phenyl-Si groups at the branching points and in the periphery of 14 giving the highly reactive triflato-Si derivative 19.

Fixation of a monodentate and a tripodal phosphine to the core of a G3–R3Si(OTf) carbosilane dendrimer

The acidolysis of the phenyl groups provided a means of activation of a relatively inert carbosilane dendrimer. In order to demonstrate the possibility of “a posteriori” functionalization we attached two different ligand systems via different linker functions to the silyltriflato units of the third generation dendrimer 16.

The first such modification concerned the introduction of a {Ph2PCH2} group using the lithiated diphenylphosphinomethanide Ph2PCH2Li. The latter may be synthesized by direct lithiation of R2PCH3 with lithium alkyls,12 however, this method generally leads to variable degrees of metallation of the methyl phosphine and consequently to product mixtures. In order to avoid this complication we chose a different synthetic route for Ph2PCH2Li by nucleophilic cleavage of Ph3SnCH2PPh2 with PhLi. This method is based on previous work by Kauffmann et al.13 as well as the group of one of us,14 and produced the desired lithium methanide very cleanly. Upon addition of a stoichiometric amount of dendrimer 16 and subsequent work up the target compound 21 was isolated as a colourless oil in good yield (Scheme 7).


Fixation of a monodentate and a tripodal phosphine to the core of the G3–R3Si(OTf) carbosilane dendrimer 16.
Scheme 7 Fixation of a monodentate and a tripodal phosphine to the core of the G3–R3Si(OTf) carbosilane dendrimer 16.

As a second target for ligand fixation we employed an ether-alcohol functionalized triphos derivative which we had previously attached to the periphery of carbosilane dendrimers employed in hydrogenation catalysis.15 Reaction of 16 with the in situ lithiated tripodal phosphine readily gave the dendritic derivative 22. As for compound 21 the main difference in the NMR spectra of this functionalized system with respect to those of 16 concerns the methylene protons adjacent to the Si-core (δ 0.86 ppm) as well as the protons in the ethylene bridge of the linker at the triphos ligand.

Conclusion

In this work we have presented a convenient strategy to introduce “masked” functionality into carbosilane dendrimers. The dendrimer synthesis is performed with the chemically relatively inert phenylsilane derivatives which do not interfere negatively with hydrosilylation catalysis. Acidolytic cleavage of the phenyl-Si units using stoichiometric amounts of triflic acid then generates highly reactive triflatosilyl units at the core, branching points or the periphery of carbosilane dendrimers which allow a facile subsequent nucleophilic substitution at these points. This method allows the introduction of functional groups, catalytic sites etc. into carbosilane dendrimers “a posteriori” to their synthesis.

Experimental

All manipulations were performed under nitrogen. Solvents were dried according to standard methods and saturated with nitrogen. The deuterated solvents used for the NMR spectroscopic measurements were degassed by three successive “freeze–pump–thaw” cycles and stored over 4-Å molecular sieves. Solids were separated from suspensions by filtration through dried Celite or by centrifugation. The 1H, 19F and 13C Si NMR spectra were recorded on Bruker AC 200, Bruker Avance 250 and Bruker AMX 400 FT NMR spectrometers (reference: tetramethylsilane), using the residual protonated solvent peak (1H) or the carbon resonance (13C). IR spectra were recorded on a Nicolet Magna IRTM 750 spectrometer. Elemental analyses were carried out by the microanalytical service at the chemistry department at Strasbourg. Triallylphenylsilane,16 tetraallylsilane,11 HO(CH2)2OCH2C(CH2PPh2)315 and iodomethyltriphenylstannane17 were prepared according to published procedures. All other chemicals used as starting materials were obtained commercially and used without further purification.

Preparation of the compounds

PhSi[CH2CH2CH2Si(Me)Cl2]3 (1). Phenyltriallylsilane (1.84 g, 8.07 mmol), MeHSiCl2 (4.18 g, 36.3 mmol) and 50 µl of Karstedt's catalyst were slowly heated in 5 ml of benzene until a weakly exothermic reaction set in and the colourless solution turned pale yellow. The reaction mixture was stirred at 55 °C for 16 h. After cooling to room temperature, the volatiles were removed in vacuo and compound 1 was obtained as an analytically pure, pale yellow oil. Yield: 4.63 g (8.07 mmol, 100%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ 0.76 (s, 9 H, H-10), 0.98 (t, 6 H, 3JHH = 8.5 Hz, H-6), 1.22 (t, 6 H, 3JHH = 7.9 Hz, H-8), 1.56–1.63 (m, 6 H, H-7), 7.38–7.50 (m, 5 H, H-2,H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ 5.4 (C-10), 15.8 (C-6/7/8), 17.2 (C-6/7/8), 25.7 (C-6/7/8), 128.0 (C-3), 129.2 (C-4), 133.9 (C-2), 136.0 (C-1). 29Si{1H} NMR (59.6 MHz, CDCl3, 295 K): δ −3.4 (Si-5), 32.3 (Si-9). IR (neat): ν 3069vw, 2925m, 1451vw, 1427w, 1403w, 1339w, 1261s, 1148m, 1109m, 1021w, 943w, 906m, 815s, 787s, 738m, 700m, 536s cm−1. C18H32Si4Cl6 (573.51 g mol−1): calc.: C 37.70, H 5.63; found: C 37.76, H 5.68%.
ugraphic, filename = b501069a-u2.gif
PhSi[CH2CH2CH2SiMe3]3 (2). To a solution of compound 1 (2.29 g, 4.00 mmol) in 40 ml of thf, which was cooled to −5 °C, were added 11.2 ml (33.6 mmol) of a 3.00 molar solution of methylmagnesium chloride in thf over a period of 1.5 h. The reaction mixture was refluxed for 23 h, cooled to room temperature and then added slowly to 50 ml of a cooled aqueous solution of NH4Cl. After separation of the organic layer, the aqueous phase was twice extracted with 30 ml of hexane, the combined organic phases were washed with 30 ml of brine and then dried over Na2SO4. After removal of the solvent and volatiles in vacuo, the residual viscous yellow oil was purified by column chromatography (SiO2, 15 cm, hexane–ethyl acetate 6 ∶ 1). Compound 2 was obtained as a colourless viscous oil. Yield: 1.25 g (2.77 mmol, 69%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.05 (s, 27 H, H-10), 0.57 (t, 6 H, 3JHH = 8.2 Hz, H-8), 0.83 (t, 6 H, 3JHH = 8.2 Hz, H-6), 1.33–1.41 (m, 6 H, H-7), 7.31–7.48 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −1.5 (C-10), 17.3 (C-6/7/8), 18.5 (C-6/7/8), 21.6 (C-6/7/8), 127.6 (C-3), 128.5 (C-4), 134.1 (C-2), 138.3 (C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −3.9 (Si-5), 0.7 (Si-9). IR (neat): ν 3068vw, 3050vw, 2952s, 2913s, 2874m, 1449vw, 1427w, 1412w, 1334w, 1259m, 1247s, 1141m, 1108m, 1022w, 943w, 907m, 862s, 834s, 734m, 698s cm−1. C24H50Si4 (451.00 g mol−1): calc.: C 63.92, H 11.17; found: C 64.03, H 10.84%.
ugraphic, filename = b501069a-u3.gif
PhSi[CH2CH2CH2Si(Me)(allyl)2]3 (3). To a solution of 1 (4.63 g, 8.07 mmol) in 5 ml of thf, which was cooled to −5 °C, 84 ml (67.8 mmol) of a 0.81 molar solution of allylmagnesium bromide were slowly added over a period of 1.5 h. The reaction mixture was heated under reflux for 24 h, then cooled to room temperature and slowly poured into 100 ml of a cooled aqueous solution of NH4Cl. After separation of the organic layer, the aqueous phase was twice extracted with 50 ml of hexane, the combined organic phases washed with 50 ml of brine and then dried over Na2SO4. After the removal of the solvent and volatiles in vacuo, the residual viscous yellow oil was purified by column chromatography (SiO2, 15 cm, hexane). Compound 3 was obtained as a viscous colourless liquid. Yield: 3.92 g (6.46 mmol, 80%).1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.05 (s, 9 H, H-10), 0.63 (t, 6 H, 3JHH = 8.2 Hz, H-8), 0.84 (t, 6 H, 3JHH = 8.2 Hz, H-6), 1.32–1.40 (m, 6 H, H-7), 1.51 (dt, 12 H,3JHH = 8.2 Hz, 5JHH = 1.2 Hz, H-11), 4.80 (t, 6 H, 3JHH = 1.2 Hz, H(cis)-13), 4.81–4.83 (m, 6 H, H(trans)-13), 5.68–5.79 (m, 6 H, H-12), 7.32–7.45 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −7.8 (C-10), 17.3 (C-6/7/8), 18.0 (C-6/7/8), 18.2 (C-6/7/8), 21.4 (C-11), 113.1 (C-13), 127.7 (C-3), 128.7 (C-4), 134.0 (C-2), 134.8 (C-12), 137.7 (C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −3.9 (Si-5), 0.3 (Si-9). IR (neat): ν 3075m, 2994w, 2970m, 2955m, 2914s, 2876m, 1629s, 1427m, 1418m, 1393m, 1335vw, 1252m, 1192w, 1155m, 1108w, 1032m, 990m, 931m, 893s, 825m, 735vw, 699m, 653vw, 591m, 549vw cm−1. C36H62Si4 (607.23 g mol−1): calc.: C 71.15, H 10.28; found: C 70.74, H 10.08%.
ugraphic, filename = b501069a-u4.gif
PhSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)Cl)2]2]3 (4). Same procedure as for compound 1, using 3.34 g (5.50 mmol) of 3 and 6.45 g (56.1 mmol) of MeHSiCl2. Compound 4 was obtained as a pale yellow liquid. Yield: 7.14 g (5.50 mmol, 100%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.08 (s, 9 H, H-10), 0.58 (t, 18 H, 3JHH = 8.0 Hz, H-8, H-11), 0.74 (s, 18 H, H-15), 0.83 (t, 6 H,3JHH = 8.4 Hz, H-6), 1.13 (t, 12 H, 3JHH = 7.9 Hz, H-13), 1.28–1.36 (m, 6 H, H-7), 1.44–1.52 (m, 12 H, H-12), 7.31–7.44 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −5.2 (C-10), 5.5 (C-15), 17.2 (C-11/12/13), 17.4 (C-6/7/8), 17.5 (C-11/12/13), 18.4 (C-6/7/8), 18.6 (C-6/7/8), 25.9 (C-11/12/13), 127.8 (C-3), 128.4 (C-4), 134.0 (C-2), 137.7 (C-1). 29Si{1H} NMR (39.8 MHz, CDCl3, 295 K): δ −4.0 (Si-5), 1.5 (Si-9), 32.2 (Si-14). IR (neat): ν 3069vw, 2925m, 2878m, 1451vw, 1427m, 1403w, 1339vw, 1261s, 1148m, 1109m, 1021w, 1021w, 943w, 906m, 815s, 787s, 738m, 700m, 536s cm−1. C42H86Si10Cl12 (1297.43 g mol−1): calc.: C 38.88, H 6.68; found: C 38.67, H 6.49%.
ugraphic, filename = b501069a-u5.gif
PhSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)(allyl)2]2]3 (5). Same procedure as for compound 3 using 7.11 g (5.48 mmol) of compound 4 and 114 ml (92.1 mmol) of a 0.81 molar solution of allylmagnesium bromide. The reaction product, compound 5 was isolated after chromatography as a colourless viscous oil. Yield: 5.00 g (3.66 mmol, 67%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.12 (s, 9 H, H-10), −0.04 (s, 18 H, H-15), 0.48–0.60 (m, 30 H, H-8, H-11, H-13), 0.83 (t, 6 H, 3JHH = 8.4 Hz, H-6), 1.26–1.36 (m, 18 H, H-7, H-12), 1.52 (d, 24 H, 3JHH = 8.2 Hz, H-16), 4.80–4.86 (m, 24 H, H-18),5.70–5.80 (m, 12 H, H-17), 7.30–7.42 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −7.7 (C-15), −5.0 (C-10), 17.6 (C-6/7/8), 17.9 (C-11/12/13), 18.2 (C-11/12/13), 18.5 (C-6/7/8), 18.8 (C-11/12/13), 19.0 (C-6/7/8), 21.5 (C-16), 113.1 (C-18), 127.7 (C-3), 128.6 (C-4), 134.0 (C-2), 135.2 (C-17), 138.0 (C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −4.0 (Si-5), 0.3 (Si-14), 1.1 (Si-9). IR (neat): ν 3075w, 2994vw, 2970w, 2954w, 2912m, 2876m, 1629s, 1419m, 1333vw, 1252s, 1192vw, 1153s, 1108vw, 1031m, 990m, 931m, 893s, 814br m, 699m, 591m cm−1. C78H146Si10 (1364.87 g mol−1): calc.: C 68.64, H 10.77; found: C 68.90, H 10.45%.
ugraphic, filename = b501069a-u6.gif
PhSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)Cl2]2]2]3 (6). Same general procedure as for compound 4, using 2.52 g (1.85 mmol) of 5 and 4.34 g (37.7 mmol) of MeHSiCl2. The reaction product, compound 6 was obtained as a pale yellow liquid. Yield: 5.08 g (1.85 mmol, 100%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.12 (s, 9 H, H-10), −0.05 (s, 18 H, H-15), 0.48–0.63 (m, 54 H, H-8, H-11, H-13, H-16), 0.75 (s, 36 H, H-20), 0.82 (t, 6 H, 3JHH = 8.2 Hz, H-6), 1.16 (t, 24 H, 3JHH = 7.9 Hz, H-18), 1.24–1.31 (m, 18 H, H-7, H-12), 1.47–1.53 (m, 24 H, H-17), 7.29–7.46 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −5.1 (C-15), −5.0 (C-10), 5.5 (C-20), 17.3 (C-16), 17.5 (C-17), 17.6 (C-6/7/8), 18.4 (C-11/12/13), 18.5 (C-6/7/8), 18.6 (C-11/12/13), 18.9 (C-11/12/13), 19.0 (C-6/7/8), 25.9 (C-18), 127.6 (C-3), 128.7 (C-4), 134.1 (C-2), 138.0 (C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −4.0 (Si-5), 1.0 (Si-9), 1.5 (Si-14), 32.2 (Si-19). IR (neat): ν 3065vw, 2918s, 2875s, 1451vw, 1409w, 1336w, 1260s, 1145m, 1083w, 1021m, 943w, 909m, 787s, 745m, 701m, 676m, 538s. C90H194Si22Cl24 (2745.28 g mol−1): calc.: C 39.38, H 7.12; found: C 39.36, H 7.15%.
ugraphic, filename = b501069a-u7.gif
PhSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2SiMe3]2]2]3 (7). Same general procedure as for compound 2, using 1.92 g (0.70 mmol) of 5 and 7.84 ml (23.5 mmol) of a 3.00 molar solution of methylmagnesium chloride. After work up and purification by column chomatography compound 7 was obtained as a viscous colourless oil. Yield: 1.14 g (0.50 mmol, 71%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.12 (s, 9 H, H-10), −0.10 (s, 18 H, H-15), −0.04 (s, 108 H, H-20), 0.48–0.56 (m, 78 H, H-8, H-11, H-13, H-16, H-18), 0.82 (t, 6 H, 3JHH = 8.2 Hz, H-6), 1.23–1.36 (m, 42 H, H-7, H-12, H-17), 7.29–7.43 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −4.9 (C-10), −4.8 (C-15), −1.5 (C-20), 18.5 (C-16/17/18, C-11/12/13), 18.7 (C-16/17/18), 18.8 (C-6/7/8, C-16/17/18), 18.9 (C-11/12/13), 19.0 (C-11/12/13), 19.1 (C-6/7/8), 19.2 (C-6/7/8), 127.6 (C-3), 128.6 (C-4), 134.1 (C-2), 138.2 (C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −3.8 (Si-5), 0.8 (Si-9, Si-14), 1.3 (Si-19). IR (neat): ν 2959s, 2910s, 2873m, 1447vw, 1412w, 1333vw, 1256s, 1138vw, 1102s, 1082s, 944vw, 909m, 862s, 827s, 800s, 694s, 690m cm−1. MS (FAB): m/z (relative intensity) 2276.8 (59), [M + Na+]. C114H266Si22 (2255.25 g mol−1): calc.: C 60.76, H 11.89; found: C 60.85, H 11.98%.
ugraphic, filename = b501069a-u8.gif
PhSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)(allyl)2]2]2]3 (8). Same procedure as for compound 5, using 5.02 g (1.83 mmol) of 6 and 92 ml (61.5 mmol) of a 0.67 molar solution of allylmagnesium bromide. After work up and purification by column chromatography the reaction product 8 was isolated as a viscous colourless oil. Yield: 3.64 g (1.26 mmol, 69%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.11 (s, 9 H, H-10), −0.09 (s, 18 H, H-15), −0.02 (s, 36 H, H-20), 0.49–0.63 (m, 78 H, H-8, H-11, H-13, H-16, H-18), 0.82 (t, 6 H, 3JHH = 8.1 Hz, H-6), 1.20–1.37 (m, 42 H, H-7, H-12, H-17), 1.54 (d, 48 H, 3JHH = 8.2 Hz, H-21), 4.81–4.86 (m, 48 H, H-23), 5.71–5.82 (m, 24 H, H-22), 7.30–7.45 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −5.7 (C-20), −5.02 (C-10), −5.0 (C-15), 17.6 (C-6/7/8), 18.0 (C-11/12/13), 18.2 (C-11/12/13), 18.3 (C-16/17/18), 18.5 (C-6/7/8), 18.5 (C-11/12/13), 18.8 (C-16/17/18), 19.0 (C-16/17/18), 19.1 (C-6/7/8), 21.5 (C-21), 113.1 (C-23), 127.6 (C-3), 128.6 (C-4), 134.1 (C-2), 134.8 (C-22), 138.0 (C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −4.1 (Si-5), 0.3 (Si-19), 1.0 (Si-9, Si-14). IR (neat): ν 3076m, 2994w, 2970m, 2954m, 2913s, 2876m, 2793vw, 1630s, 1449vw, 1419m, 1333w, 1252s, 1193w, 1153m, 1081vw, 1031m, 990m, 931m, 893s, 814br s, 699m, 654vw, 591m cm−1. C162H314Si22 (2880.16 g mol−1): calc.: C 67.56, H 10.99; found: C 66.87, H 9.89%.
ugraphic, filename = b501069a-u9.gif
PhSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)Cl2]2]2]2]3 (9). Same general procedure as for compound 4, using 1.58 g (0.55 mmol) of 8 and 49 g (21.7 mmol) of MeHSiCl2. After work-up compound 9 was isolated as a pale yellow liquid. Yield: 3.10 g (0.55 mmol, 100%). 1H NMR (400.13 MHz, CDCl3, 295 K): δ −0.12 (s, 9 H, H-10), −0.09 (s, 18 H, H-15), −0.04 (s, 36 H, H-20), 0.51–0.64 (m, 126 H, H-8, H-11, H-13, H-16, H-18, H-21), 0.75 (s, 72 H, H-25), 0.81 (t, 6 H, 3JHH = 8.1 Hz, H-6), 1.16 (t, 48 H, 3JHH = 8.0 Hz, H-23), 1.23–1.33 (m, 42 H, H-7, H-12, H-17), 1.48–1.56 (m, 48 H, H-22), 7.29–7.43 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −5.1 (C-10), −5.0 (C-15), −4.9 (C-20), 5.5 (C-25), 17.3 (C-21/22/23), 17.5 (C-21/22/23), 18.0 (C-6/7/8), 18.2 (C-6/7/8), 18.3 (C-6/7/8), 18.5 (C-16/17/18), 18.6 (C-16/17/18), 18.9 (C-16/17/18), 19.0 (C-11/12/12), 19.1 (C-11/12/12), 19.2 (C-11/12/12), 25.9 (C-21/22/23), 127.6 (C-3), 128.6 (C-4), 134.1 (C-2), 138.0 (C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −4.3 (Si-5), 0.7 (Si-9), 0.8 (Si-14), 1.3 (Si-19), 31.9 (Si-24). IR (neat): ν 2957m, 2917s, 2875s, 2792w, 1451m, 1409m, 1336m, 1260s, 1217m, 1145s, 1084m, 1021m, 979w, 943m, 909s, 817s, 787s, 746s, 700m, 677m, 539s cm−1.
ugraphic, filename = b501069a-u10.gif
PhSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2SiMe3]2]2]2]3 (10). Same general procedure as for compounds 2 and 7, using 2.99 g (0.53 mmol) of 9 and 11.9 ml (35.6 mmol) of a 3.0 molar solution of methylmagnesium chloride. After work-up and purification by column chromatography, compound 10 was obtained as a viscous, colourless liquid. Yield: 1.72 g (0.37 mmol, 69%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.11 (s, 9 H, H-10), −0.10 (s, 18 H, H-15), −0.09 (s, 36 H, H-20), −0.04 (s, 216 H, H-25), 0.54 (t, 3JHH = 8.3 Hz, 174 H, H-8, H-11, H-13, H-16, H-18, H-21, H-23), 0.82 (t, 6 H, 3JHH = 8.2 Hz, H-6), 1.24–1.36 (m, 90 H, H-7, H-12, H-17, H-22), 7.27–7.44 (m, 5 H, H-2, H-3, H-4). 13C{1H} NMR (125.8 MHz, C6D6, 295 K): δ −4.5 (C-25, C-20), −4.4 (C-15, C-10), 19.1 (C-21/22/23), 9.2 (C-21/22/23, C-16/17/18), 19.3 (C-6/7/8), 19.4 (C-6/7/8), 19.5 (C-6/7/8, C-16/17/18), 19.6 (C-16/17/18, C-11/12/13), 19.7 (C-11/12/13, C-11/12/13), 21.9 (C-21/22/23), 127.9 (C-2/3), 128.0 (C-1), 128.1 (C-2/3), 128.3 (C-4). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −3.8 (Si-5), 0.8 (Si-9, Si-14), 1.2 (Si-19), 1.3 (Si-24). IR (neat): ν 2952s, 2930s, 2873s, 2790vw, 1449w, 1412m, 1333m, 1247s, 1215w, 1141s, 1080m, 1022m, 979w, 944m, 909s, 862s, 834s, 796s, 756m, 690m, 664w cm−1. MS (FAB): m/z (relative intensity) 4680.5 (98), [M + Na+]. C234H554Si46 (4660.91 g mol−1): calc.: C 60.25, H 11.98; found: C 60.22, H 11.94%.
ugraphic, filename = b501069a-u11.gif
Si[CH2CH2CH2Si(Ph)Cl2]4 (11). Tetraallylsilane (934 mg, 4.85 mmol), PhHSiCl2 (5.85 g, 33.0 mmol) and 60 µl of Karstedt's catalyst were slowly warmed in 15 ml of benzene until an exothermic reaction set in and the colourless solution turned bright yellow. The reaction mixture was stirred at 60 °C for 48 h. After cooling to room temperature, the solution was filtered through 5 cm of silica and the solvent and volatiles were then removed in vacuo. After leaving under high vacuum for 1.5 h, compound 11 was obtained as a pure pale yellow liquid.

Yield: 4.37 g (4.85 mmol, 100%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ 0.58 (t, 8 H, 3JHH = 5.9 Hz, H-2), 1.35 (t, 8 H, 3JHH = 7.6 Hz, H-4), 1.46–1.77 (m, 8 H, H-3), 7.41–7.71 (m, 20 H, H-7, H-8, H-9). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ 15.8 (C-2/3/4), 17.3 (C-2/3/4), 24.9 (C-2/3/4), 128.3 (C-8), 131.6 (C-9), 131.7 (C-6), 132.2 (C-7). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ 1.5 (Si-1), 18.3 (Si-5). IR (neat): ν 3073w, 3058vw, 2963m, 2924m, 2876m, 2209w, 1590w, 1429s, 1337 w; 1262m, 1117s, 1020m, 797s, 737m, 694s, 565m, 510m cm−1. C36H44Si5Cl8 (900.80 g mol−1): calc.: C 47.96, H 4.92; found: C 47.05, H 4.91%.

ugraphic, filename = b501069a-u12.gif

Si[CH2CH2CH2Si(Ph)(allyl)2]4 (12). To a solution of compound 11 (4.36 g, 4.85 mmol) in 10 ml of thf, which was cooled to –5 °C, 116 ml (54.5 mmol) of a 0.47 molar solution of allylmagnesium bromide were added over a period of 1.5 h. The reaction mixture was heated under reflux for 48 h, then cooled to room temperature and slowly poured into a cooled aqueous solution (100 ml) of NH4Cl. After separation of the organic layer the aqueous phase was twice extracted with 50 ml of hexane, the combined organic phases were washed with brine and then dried over Na2SO4. After removal of the volatiles the residue was purified by column chromatography (SiO2, 15 cm, hexane–ethyl acetate 6 ∶ 1) giving compound 12 as a viscous colourless oil. Yield: 3.21 g (3.40 mmol, 70%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ 0.50 (t, 8 H, 3JHH = 8.2 Hz, H-2), 0.87 (t, 8 H, 3JHH = 8.2 Hz, H-4), 1.28–1.39 (m, 8 H, H-3), 1.83 (d, 16 H, 3JHH = 7.6 Hz, H-10), 4.85–4.93 (m, 16 H, H-12), 5.73–5.85 (m, 8 H, H-11), 7.34–7.51 (m, 20 H, H-7, H-8, H-9). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ 16.7 (C-2/3/4), 17.4 (C-2/3/4), 18.2 (C-2/3/4), 20.1 (C-10), 113.9 (C-12), 127.7 (C-8), 129.1 (C-9), 134.1 (C-7/11), 134.2 (C-7/11), 136.1 (C-6). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −6.5 (Si-5), 0.9 (Si-1). IR (neat): ν 3075s, 3053m, 3021m, 2998m, 2972m, 2918m, 2883m, 2125s, 1812w, 1630s, 1486w, 1427s, 1416m, 1399m, 1300w, 1261w, 1191m, 1156m, 1114m, 1038m, 990m, 929m, 896s, 848s, 824m, 786m, 738m, 699s, 660w, 600m, 571w cm−1. C60H84Si5 (945.75 g mol−1): calc.: C 76.14, H 8.95; found: C 76.12, H 8.80%.
ugraphic, filename = b501069a-u13.gif
Si[CH2CH2CH2Si(Ph)[CH2CH2CH2Si(Ph)Cl2]2]4 (13). Same procedure as in the preparation of 11, using 361 mg (0.38 mmol) of compound 12 and 757 mg (4.28 mmol) of PhHSiCl2. After work-up, compound 13 was obtained as a pale yellow oil. Yield: 897 mg (0.38 mmol, 100%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ 0.92–1.01 (m, 24 H, H-2, H-10), 1.41–1.46 (m, 24 H, H-4, H-12), 1.60–1.70 (m, 24 H, H-3, H-11), 7.45–7.73 (m, 60 H, H-7, H-8, H-9, H-15, H-16, H-17). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ 15.8 (C-10/11/12), 16.0 (C-2/3/4), 16.3 (C-2/3/4), 17.3 (C-10/11/12), 24.7 (C-2/3/4, C-10/11/12), 127.9 (C-8), 128.3 (C-16), 129.2 (C-9), 131.6 (C-17), 132.7 (C-6, C-14), 133.3 (C-15), 133.9 (C-7). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −12.1 (Si-1), −4.0 (Si-5), 18.1 (Si-13). IR (neat): ν 3072w, 3051vw, 2956m, 2925s, 2878m, 1618w, 1590m, 1487w, 1429s, 1337w, 1259w, 1145m, 1117s, 1028m, 998m, 901m, 793m, 738m, 695s, 564s, 549m, 510s cm−1. C108H132Si13Cl16 (2362.59 g mol−1): calc.: C 54.86, H 5.63; found: C 54.55, H 5.74%.
ugraphic, filename = b501069a-u14.gif
Si[CH2CH2CH2Si(Ph)[CH2CH2CH2Si(Ph)Me2]2]4 (14). To a solution of compound 13 (874 mg, 0.37 mmol) in 40 ml of thf, which was cooled to −5 °C, 2.84 ml (8.51 mmol) of a 3.0 molar solution of methylmagnesium chloride were slowly added. After refluxing for 48 h, the reaction mixture was cooled to room temperature and then poured into a cooled aqueous solution (50 ml) of NH4Cl. After separation of the organic layer, the aqueous phase was twice extracted with 30 ml of hexane, the combined organic phases were washed with 30 ml of brine and then dried over Na2SO4. After removal of the volatiles in vacuo, the residual yellow oil was purified by column chromatography (SiO2, 15 cm, hexane–ethyl acetate 6 ∶ 1). Compound 14 was obtained as a viscous colourless liquid. Yield: 482 mg (0.24 mmol, 65%). 1H NMR (400.13 MHz, CDCl3, 295 K): δ 0.22 (s, 48 H, H-18), 0.80 (t, 48 H, 3JHH = 8.0 Hz, H-2, H-4, H-10, H-12), 1.30–1.39 (m, 24 H, H-3, H-11), 7.33–7.48 (m, 60 H, H-7, H-8, H-9, H-15, H-16, H-17). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −2.9 (C-18), 17.2 (C-10/11/12), 17.4 (C-2/3/4), 18.3 (C-2/3/4), 18.4 (C-10/11/12), 20.3 (C-2/3/4), 20.4 (C-10/11/12), 127.6 (C-8), 127.3 (C-16), 128.6 (C-9), 128.7 (C-17), 133.5 (C-15), 134.0 (C-7), 137.9 (C-6), 139.7 (C-14). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ −22.1 (Si-1), −4.1 (Si-5/13), −4.0 (Si-5/13). IR (neat): ν 3068w, 3046vw, 2961s, 2908m, 2873w, 2851w, 2790vw, 1447w, 1426m, 1412m, 1258s, 1110s, 1023s, 863m, 819s, 728m, 699m, 661m cm−1. MS (FAB): m/z (relative intensity) 2058.1 (25), [M + Na+].
ugraphic, filename = b501069a-u15.gif

General procedure for the preparation of the dendritic silyl triflates

To a solution of the dendritic phenylcarbosilane (0.6 mmol) in 10 ml of toluene, which was cooled to −40 °C, 91.5 mg (0.61 mmol) of trifluoromethanesulfonic acid were added dropwise. The reaction mixture was then warmed to −20 °C and stirred for 30 min at that temperature. After stirring for another 45 min while warming the solution to room temperature, the acid was completely dissolved. After removal of the volatiles in vacuo, the reaction product was left in a high vacuum (10−5 mbar) for 2.5 h. The yield of the silyltriflates, which are pale yellow oils was quantitative in all cases.
F3CSO3Si[CH2CH2CH2SiMe3]3 (15). 1H NMR (400.14 MHz, CDCl3, 295 K): δ −0.03 (s, 27 H, H-8), 0.58 (t, 6 H, 3JHH = 8.2 Hz, H-6), 0.95 (t, 6 H, 3JHH = 8.2 Hz, H-4), 1.39–1.47 (m, 6 H, H-5). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −1.7 (C-8), 17.0 (C-4/5/6), 18.3 (C-4/5/6), 21.0 (C-4/5/6), 118.4 (q, C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ 1.3 (Si-7), 37.1 (Si-3). 19F NMR (376.4 MHz, CDCl3, 295 K): δ −76.8 (F-2). IR (neat): ν 2953m, 2916m, 2874m, 2205br w, 1394w, 1248s, 1209s,1027s, 946vw, 909m, 862s, 835s, 770vw, 693m, 638m, 577vw, 513w cm−1.
ugraphic, filename = b501069a-u16.gif
F3CSO3Si[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2SiMe3]2]2]3 (16). 1H NMR (300.17 MHz, CDCl3, 295 K): δ −0.11 (s, 9 H, H-8), −0.10 (s, 18 H, H-13), −0.05 (s, 108 H, H-18), 0.53 (t, 84 H, 3JHH = 7.9 Hz, H-4, H-6, H-9, H-11, H-14, H-16), 1.24–1.43 (m, 42 H, H-5, H-10, H-15). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −5.1 (C-8), −4.8 (C-13), −1.4 (C-18), 18.5 (C-14/15/16), 18.6 (C-9/10/11), 18.8 (C-14/15/16, C-4/5/6), 19.0 (C-9/10/11), 19.1 (C-9/10/11), 19.2 (C-4/5/6), 19.3 (C-4/5/6), 21.6 (C-14/15/16), 128.6 (q, C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ 0.3 (Si-12), 0.9 (Si-17), 3.2 (Si-7), 39.7 (Si-3). 19F NMR (376.4 MHz, CDCl3, 295 K): δ −77.2 (F-2). IR (neat): ν 2952s, 2911s, 2873m, 2791vw, 1448vw, 1411w, 1333vw, 1258s,1248s, 1215vw, 1141m, 1081m, 1081m, 1026m, 981vw, 944w, 910m, 862s, 834s, 807m,750m, 691m cm−1.
ugraphic, filename = b501069a-u17.gif
F3CSO3Si[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2SiMe3]2]2]2]3 (17). 1H NMR (300.17 MHz, CDCl3, 295 K): δ −0.12 (s, 9 H, H-8), −0.11 (s, 18 H, H-13), −0.10 (s, 36 H, H-18), −0.05 (s, 216 H, H-23), 0.53 (t, 180 H, 3JHH = 7.9 Hz, H-4, H-6, H-9, H-11, H-14, H-16, H-19, H-21), 1.24–1.34 (m, 90 H, H-5, H-10, H-15, H-20). 13C{1H} NMR (125.7 MHz, CDCl3, 295 K): δ −5.1 (C-8), −5.0 (C-13), −4.9 (C-18), −1.4 (C-23), 18.5 (C-19/20/21), 18.6 (C-14/15/16), 18.7 (C-19/20/21, C-9/10/11), 18.8 (C-4/5/6, C-4/5/6), 18.9 (C-4/5/6), 19.0 (C-14/15/16, C-14/15/16), 19.1 (C-9/10/11), 19.2 (C-9/10/11), 21.5 (C-19/20/21), 128.7 (q, C-1). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ 0.3 (Si-12, Si-17), 0.8 (Si-22), 3.2 (Si-7), 39.8 (Si-3). 19F NMR (376.5 MHz, CDCl3, 295 K): δ −76.7 (F-2). IR (neat): ν 2952s, 2911s, 2872m, 2793vw, 1453vw, 1411w, 1333vw, 1248s, 1217vw, 1141m, 1080m, 1025m, 978vw, 943w, 909m, 862s, 834s, 809m, 751m, 691m cm−1.
ugraphic, filename = b501069a-u18.gif
F3CSO3Si[CH2CH2CH2Si(Me)2OSO2CF3]3 (18). To a solution of compound 2 (242 mg, 0.54 mmol) in 10 ml of toluene, which was cooled at −40 °C, were added dropwise 810 mg (5.40 mmol) of trifluoromethanesulfonic acid over a period of 10 min. The reaction mixture was warmed to −20 °C and stirred for another 30 min at that temperature. After subsequent stirring at room temperature for 45 min, all the volatiles were removed in vacuo yielding compound 19 as a light yellow oil. Yield: 497 mg (0.54 mmol, 100%). 1H NMR (400.14 MHz, CDCl3, 295 K): δ 0.47 (s, 18 H, H-8), 0.98–1.05 (m, 12 H, H-4, H-6), 1.53–1.62 (m, 6 H, H-5). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −1.4 (C-8), 15.4 (C-4/5/6), 17.4 (C-4/5/6), 20.3 (C-4/5/6), 118.3 (q, C-1, C-9). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ 38.7 (Si-3), 43.1 (Si-7). 19F NMR (376.4 MHz, CDCl3, 295 K): δ −76.9 (F-10), −76.6 (F-2). IR (neat): ν 2952m, 2927m, 2875m, 2204br w, 1388s, 1343m, 1247s, 1200 br s, 1156s, 1030s, 967m, 909m, 860m, 807m, 717w, 629s, 550w, 530w, 515w cm−1.
ugraphic, filename = b501069a-u19.gif
Si[CH2CH2CH2Si(OSO2CF3)[CH2CH2CH2Si(OSO2CF3)Me2]2]4 (19). To a solution of compound 14 (143 mg, 0.07 mmol) in 5 ml of toluene, which was cooled at −40 °C, were added dropwise 127 mg (0.84 mmol) of trifluoromethanesulfonic acid. After stirring at −20 °C for 30 min and at room temperature for another 50 min, the solvent and volatiles were removed. After leaving the reaction product under high vacuum (10−5 mbar) for 5 h, compound 19 was obtained as a pale yellow oil. Yield: 84.1 mg (0.07 mmol, 100%). 1H NMR (300.17 MHz, CDCl3, 295 K): δ 0.47 (s, 48 H, H-12), 0.98–1.06 (m, 48 H, H-2, H-4, H-8, H-10), 1.52–1.63 (m, 24 H, H-3, H-9). 13C{1H} NMR (75.4 MHz, CDCl3, 295 K): δ −1.4 (C-12), 15.4 (C-8/9/10), 17.4 (C-8/9/10, C-2/3/4), 17.9 (C-2/3/4), 19.9 (C-2/3/4), 20.2 (C-8/9/10), 116.2 (q, C-6, C-13). IR (neat): ν 2861s, 2925s, 2874s, 2217 br w, 1512vw, 1450m, 1394s, 1260s, 1205s, 1160s, 1107s, 1030s, 976s, 911s, 865s, 822s, 712w, 633s, 570vw, 514m cm−1.
ugraphic, filename = b501069a-u20.gif
Ph3SnCH2PPh2 (20). To a stirred solution of iodomethyltriphenylstannane17 (2.01 g, 4.09 mmol) in 60 ml of toluene, which was cooled to −55 °C, were added 2.57 ml (4.09 mmol) of a 1.59 molar solution of n-BuLi in hexane. After stirring for 30 min at that temperature 951 mg (8.19 mmol) of TMEDA were added and the clear solution further cooled to −90 °C. At this temperature 902 mg (4.09 mmol) of Ph2PCl were added dropwise over a period of 10 min. The yellow solution was then warmed to −80 °C and stirred for another 45 min. After slowly warming to room temperature, the reaction mixture was hydrolyzed with 15 ml of degassed water, the organic layer was then separated, twice extracted with 10 ml of degassed water and then dried over Na2SO4. After removal of all the volatiles in vacuo, the oily residue was taken up in 3 ml of pentane and subjected to column chromatography on Al2O3 (basic, activity III) with pentane as eluent. After collection of the product fraction, all volatiles were removed in vacuo and the colourless solid residue dried in high vacuum to give pure 20. Yield: 1.95 g (3.56 mmol, 87%). 1H NMR (300.17 MHz, C6D6, 295 K): δ 1.96 (d, 2 H, 2JHP = 2.2 Hz, H-6), 6.96–7.05 (m, 10 H, H-3, H-4, H-5), 7.32–7.46 (m, 15 H, H-8, H-9, H-10). 13C{1H} NMR (75.4 MHz, CDCl3, 295 K): δ 8.7 (d, JPC = 34.2 Hz, C-6), 128.2 (d, JPC = 6.1 Hz, C-4), 128.4 (C-10), 128.9 (C-9), 132.3 (d, JPC = 19.5 Hz, C-2), 136.8 (C-5), 136.9 (C-8), 138.3 (d, JPC = 2.4 Hz, C-7), 141.1 (d, JPC = 14.7 Hz, C-3). 31P{1H} NMR (121.5 MHz, C6D6, 295 K): δ −20.2 (J(119/117SnP) = 50.9 Hz, P-1). C31H27SnP (549.24 g mol−1) calc.: C 67.85, H 4.96; found: C 68.02, H 5.14%.
ugraphic, filename = b501069a-u21.gif
Ph2PCH2Si[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2SiMe3]2]2]3 (21). To a solution of Ph3SnCH2PPh2 (65.9 mg, 0.12 mmol) in 2 ml of diethyl ether, which was stirred at room temperature, were added 64 µl (0.12 mmol) of a 1.8 molar solution of PhLi in cyclohexaneether with the aid of a Hamilton syringe. After stirring for 16 h, a colourless solid had precipitated. The suspension was cooled to −78 °C and 13.9 mg (0.12 mmol) of TMEDA and then 279 mg (0.12 mmol) of compound 16 (dissolved in 2 ml of diethyl ether) were added. After stirring at that temperature for 30 min, the reaction mixture was warmed to room temperature and stirred for another 30 min. After removal of the volatiles in vacuo, the residue was extracted with 20 ml of hexane. The solvent of the extract was again removed leaving an oily residue which was taken up in 1 ml of pentane and subjected to column chromatography (Al2O3 basic, activity I, eluent: pentane) giving the reaction product 21 as a colourless oil. Yield: 214 mg (0.09 mmol, 74%). 1H NMR (300.17 MHz, CDCl3, 295 K): δ −0.09 (s, 9 H, H-12), −0.08 (s, 18 H, H-17), −0.03 (s, 108 H, H-22), 0.55 (t, 78 H, 2JHH = 7.5 Hz, H-10, H-13, H-15, H-18, H-20), 0.87 (t, 2 H, 3JHH = 6.6 Hz, H-8), 1.25–1.41 (m, 42 H, H-9, H-14, H-19), 1.61 (d, 2 H, 3JHP = 3.5 Hz, H-2), 7.30–7.41 (m, 10 H, H-5, H-6, H-7). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ −5.0 (C-12), −4.9 (C-17), −1.5 (C-22), 12.5 (d, JPC = 13.2 Hz, C-2), 18.5 (C-18/19/20, C-13/14/15), 18.7 (C-18/19/20, C-8/9/10), 18.9 (C-13/14/15), 19.0 (C-13/14/15), 19.1 (C-8/9/10), 19.2 (C-8/9/10), 21.5 (C-18/19/20), 128.3 (d, JPC = 3.0 Hz, C-6), 132.1 (d, JPC = 18.3 Hz, C-4), 137.2 (C-7), 140.2 (d, JPC = 11.2 Hz, C-5). 31P{1H} NMR (121.5 MHz, CDCl3, 295 K): δ −26.9 (P-3). IR (neat): ν 3060vw, 2952s, 2910s, 2875s, 2795vw, 1480vw, 1451vw, 1432w, 1412w, 1383vw, 1332w, 1247s, 1215vw, 1141m, 1063w, 1141m, 944vw, 909m, 861s, 833s, 737m, 694m cm−1. C121H273Si22P (2377.35 g mol−1): calc.: C 61.07, H 11.58; found: C 61.08, H 11.75%.
ugraphic, filename = b501069a-u22.gif
[Ph2PCH2]3CCH2OCH2CH2OSi[CH2CH2CH2Si(Me)[CH2CH2CH2Si(Me)[CH2CH2CH2SiMe3]2]2]3 (22). To a solution of [Ph2PCH2]3CCH2OCH2CH2OH (47.9 mg, 0.07 mmol) in 1 ml of thf, which was cooled to −60 °C, 44 µl (0.07 mmol) of a 1.59 molar solution of n-BuLi in hexane were added with the aid of a Hamilton syringe. The resulting yellow solution was warmed to room temperature and stirred for 30 min. After re-cooling the reaction mixture to −90 °C, compound 16 (163 mg, 0.07 mmol) dissolved in 1 ml of thf was added. After stirring for another 15 min at that temperature, the solution was warmed to room temperature and stirred for 16 h. After removal of the volatiles in vacuo, the residue was taken up in 10 ml of toluene and the colourless precipitate separated by centrifugation. The solvent of the centrifugate was removed in vacuo and the reaction product left under high vacuum (10−5 mbar) for another 5 h to afford compound 22 as a colourless oil. Yield: 190 mg (0.07 mmol, 95%). 1H NMR (300.17 MHz, CDCl3, 295 K): δ −0.09 (s, 9 H, H-6), −0.08 (s, 18 H, H-11), −0.03 (s, 108 H, H-16), 0.55 (t, 78 H, 3JHH = 7.8 Hz, H-4, H-7, H-9, H-12, H-14), 0.86 (t, 6 H, 3JHH = 8.3 Hz, H-2), 1.25–1.38 (m, 42 H, H-3, H-8, H-13), 2.44 (d, 6 H, 2JHP = 1.7 Hz, H-21), 2.87 (t, 2 H, 3JHH = 4.2 Hz, H-17/18), 3.30–3.34 (m, 4 H, H-17/18, H-19), 7.15–7.31 (m, 30 H, H-aromat.). 13C{1H} NMR (75.5 MHz, CDCl3, 295 K): δ −5.0 (C-6), −4.9 (C-11), −1.4 (C-16), 18.5 (C-12/13/14), 18.6 (C-7/8/9), 18.7 (C-12/13/14), 18.8 (C-2/3/4), 18.9 (C-7/8/9), 19.0 (C-7/8/9), 19.1 (C-2/3/4), 19.2 (C-2/3/4), 21.5 (C-12/13/14), 38.3–39.0 (m, C-21), 42.4–42.9 (m, C-20), 61.1 (C-17/18), 71.4 (C-17/18), 76.9 (C-19), 128.3 (d, JPC = 7.3 Hz, C-aromat.), 132.9 (d, JPC = 20.7 Hz, C-aromat.), 133.0 (C-aromat.), 139.5 (d, JPC = 11.3 Hz, Cquartär-aromat.). 31P{1H} NMR (121.5 MHz, CDCl3, 295 K): δ −26.6 (P-22). 29Si{1H} NMR (79.5 MHz, CDCl3, 295 K): δ 0.4 (Si-15), 0.9 (Si-10), 3.2 (Si-5), 15.3 (Si-1). IR (neat): ν 2952s, 2910s, 2873s, 2792vw, 1450vw, 1233w, 1247s, 1215w, 1141m, 1082m, 1024m, 978w, 943w, 909m, 862s, 834s, 822s, 802m, 691m cm−1. C151H303Si22O2P3 (2861.87 g mol−1): calc.: C 63.37, H 10.67; found: C 62.54, H 11.23%.
ugraphic, filename = b501069a-u23.gif

Acknowledgements

We thank the Deutsche Forschungsgemeinschaft for funding and Wacker Chemie AG for generous gifts of basic chemicals.

References

  1. Selected overviews: (a) G. R. Newkome, C. N. Moorefield and F. Vögtle, Dendritic Molecules: Concepts, Syntheses, Perspectives, VCH, Weinheim, 1996 Search PubMed; (b) D. A. Tomalia, A. M. Naylor and W. A. Goddard III, Angew. Chem., 1990, 102, 119 CrossRef CAS; (c) D. A. Tomalia and H. D. Durst, Top. Curr. Chem., 1993, 165, 193 CAS; (d) J. Issberner, R. Moers and F. Vögtle, Angew. Chem., 1994, 106, 2507 CrossRef CAS; (e) N. Ardoin and D. Astruc, Bull. Soc. Chim. Fr., 1995, 132, 875 CAS; (f) J. M. J. Fréchet, Science, 1994, 263, 1710 CrossRef CAS; (g) F. Vögtle and A. de Meijere, Top. Curr. Chem., 1998, 197, 1 CAS; (h) H. Frey, C. Lach and K. Lorenz, Adv. Mater., 1998, 10, 279 CrossRef CAS; (i) F. Zeng and S. C. Zimmerman, Chem. Rev., 1997, 97, 1681 CrossRef CAS; (j) J.-P. Majoral and A.-M. Caminade, Chem. Rev., 1999, 99, 845 CrossRef CAS; (k) D. Astruc (ed.), C. R. Chim., 2003, 6(8–10) Search PubMed.
  2. General review: (a) H. Frey and C. Schlenk, Top. Curr. Chem., 2000, 210, 69 CAS; recent reviews on transition metal containing carbosilane dendrimers: (b) O. Rossell, M. Seco and I. Angurell, C. R. Chim., 2003, 6, 803 Search PubMed; (c) J. N. H. Reek, D. de Groot, G. E. Oosteroom, P. C. J. Kamer and P. W. N. M. van Leeuwen, C. R. Chim., 2003, 6, 1061 Search PubMed.
  3. K. Lorenz, R. Mühlhaupt, H. Frey, U. Rapp and F. J. Mayer-Posner, Macromolecules, 1995, 28, 6657 CrossRef CAS.
  4. N. Hadjichritidis, A. Guyot and L. J. Fetters, Macromolecules, 1978, 11, 668 CrossRef.
  5. (a) A. W. van der Made and P. W. N. M. van Leeuwen, J. Chem. Soc., Chem. Commun., 1992, 1400 RSC; (b) A. W. van der Made, P. W. N. M. van Leeuwen, J. C. de Wilde and R. A. C. Brandes, Adv. Mater., 1993, 5, 466 CrossRef CAS.
  6. (a) L.-L. Zhan and J. Roovers, Macromolecules, 1993, 26, 963 CrossRef CAS; (b) J. Roovers, P. M. Toporowski and L.-L. Zhan, Polym. Prepr. (Am. Chem. Sci. Div. Polym. Chem.), 1992, 23, 182 Search PubMed.
  7. A. M. Muzafarov, O. B. Gorbatsevich, E. A. Rebrov, G. M. Ignat'eva, T. B. Myakushev, A. F. Bulkin and V. S. Papkov, Polym. Sci. Ser. A, 1993, 35, 1575 Search PubMed.
  8. D. Seyferth, D. Y. Son, A. L. Rheingold and R. L. Ostrander, Organometallics, 1994, 13, 2682 CrossRef CAS.
  9. (a) K. Matyjaszewski and Y. L. Chen, J. Organomet. Chem., 1988, 340, 7 CrossRef CAS; (b) W. Uhlig, Chem. Ber., 1992, 125, 47 CrossRef CAS.
  10. D. K. Polyakov, G. M. Ignat'eva, E. A. Rebrov, N. G. Vasilenko, S. S. Sheiko, M. Möller and A. M. Muzafarov, Vysokomolekul. Soedin., Ser. A, Ser. B, 1998, 40, 1421 Search PubMed.
  11. A. Boudin, C. Chuit, C. Genevieve, J. P. Corriu and C. Reye, Angew. Chem., 1986, 98, 474 CrossRef.
  12. (a) D. P. Craig, A. Maccol, R. S. Nyholm, L. E. Orgel and L. E. Sutton, J. Chem. Soc., 1954, 332 RSC; (b) D. P. Craig, A. Maccol, R. S. Nyholm, L. E. Orgel and L. E. Sutton, J. Chem. Soc., 1954, 354 RSC; (c) D. J. Peterson, J. Organomet. Chem., 1977, 16, 1770; (d) S. O. Grim, P. H. Smith, I. J. Colquhonn and W. McFarlane, Inorg. Chem., 1980, 19, 3195 CrossRef CAS; (e) H. R. Hays and D. J. Peterson, J. Org. Chem., 1965, 30, 1939 CAS; (f) P. Hofmann and H. Heiß, Ger. Pat. Appl., p. 4, 034 604, 1992 (Chem. Abstr., 1992, 117, 171685r) Search PubMed; (g) H. H. Karsch and H. Schmidbaur, Z. Naturforsch., Teil B, 1977, 32, 762; (h) S. O. Grim and J. D. Mitchell, Inorg. Chem., 1977, 16, 1770 CrossRef CAS.
  13. T. Kauffmann, B. Altepeter, N. Klas and R. Kriegesmann, Chem. Ber., 1985, 118, 2353 CrossRef CAS.
  14. (a) H. Werner, M. Manger, M. Laubender, M. Teichert and D. Stalke, J. Organomet. Chem., 1998, 569, 189 CrossRef; (b) M. Manger, J. Wolf, M. Teichert, D. Stalke and H. Werner, Organometallics, 1998, 17, 3210 CrossRef CAS; (c) H. Werner, M. Manger, U. Schmidt, M. Laubender and B. Weberndörfer, Organometallics, 1998, 17, 2619 CrossRef CAS.
  15. R. A. Findeis and L. H. Gade, Eur. J. Inorg. Chem., 2003, 99 CrossRef CAS.
  16. R. H. Meen and H. Gilman, J. Org. Chem., 1957, 22, 684 CrossRef CAS.
  17. (a) D. Seyferth and S. B. Andrews, J. Organomet. Chem., 1969, 18, 21 CrossRef CAS; (b) D. Seyferth and S. B. Andrews, J. Organomet. Chem., 1971, 30, 151 CrossRef CAS; (c) D. Seyferth, S. B. Andrews and R. S. Lambert, J. Organomet. Chem., 1972, 37, 69 CrossRef CAS; (d) D. Seyferth and R. S. Lambert, J. Organomet. Chem., 1973, 54, 123 CrossRef CAS; (e) P. G. Harrison and K. Molloy, J. Organomet. Chem., 1978, 152, 53 CrossRef CAS.

This journal is © The Royal Society of Chemistry 2005