Karel
Škoch
a,
Ivana
Císařová
a,
Jiří
Schulz
a,
Ulrich
Siemeling
b and
Petr
Štěpnička
*a
aDepartment of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic. E-mail: petr.stepnicka@natur.cuni.cz
bInstitute of Chemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
First published on 18th July 2017
The development of a practical synthesis of 1′-(diphenylphosphino)-1-aminoferrocene (2) and its P-borane adduct (2B) allowed the facile preparation of 1′-(diphenylphosphino)-1-isocyanoferrocene (1). This compound combining two specific soft-donor moieties was studied as a ligand for univalent Group 11 metal ions. The reactions of 1 with AgCl at 1:
1 and 2
:
1 molar ratios only led to the coordination polymer [Ag2(μ-Cl)2(μ(P,C)-1)]n (6), while those with Ag[SbF6] provided the dimer [Ag2(Me2CO-κO)2(μ(P,C)-1)2][SbF6]2 and the quadruply-bridged disilver complex [Ag2(μ(P,C)-1)4][SbF6]2 (8), respectively. Addition of 1 to [AuCl(tht)] (tht = tetrahydrothiophene) afforded the mono- and the digold complex, [AuCl(1-κP)] (9) and [(μ(P,C)-1)(AuCl)2] (10), depending on the reaction stoichiometry. Finally, the reaction of 1 with [Au(tht)2][SbF6] or halogenide removal from 9 with AgNTf2 led to cationic dimers [Au2(μ(P,C)-1)2]X2 (11, X = SbF6 (a) or NTf2 (b)). Catalytic tests in the Au-mediated isomerization of (Z)-3-methylpent-2-en-4-yn-1-ol to 2,3-dimethylfuran revealed that 11a and 11b are substantially less catalytically active than their analogues containing 1′-(diphenylphosphino)-1-cyanoferrocene as the ligand, most likely due to a stronger coordination of the isonitrile moiety, which prevents dissociation of the dimeric complexes into catalytically active monomeric species.
Recently we reported the synthesis of 1′-(diphenylphosphino)-1-cyanoferrocene (D) and the coordination properties of this soft–soft hybrid donor toward Group 11 metals.12 The often unusual structures of the isolated complexes as well as excellent catalytic properties of the Au(I)-D complexes12b led us to expand our studies toward the closest isomeric compound, 1′-(diphenylphosphino)-1-isocyanoferrocene (1 in Scheme 1), which formally falls between diisocyanide B and the widely studied 1,1′-bis(diphenylphosphino)ferrocene (dppf).13
Although the transposition of the nitrogen and carbon atoms in the structures of D and 1 might appear marginal in terms of chemical constitution, it can be expected to dramatically alter the reactivity and coordination properties of these compounds. It is also noteworthy that similar ligands combining isocyanide and phosphine donor moieties remain limited to only a handful of compounds including Ph2P(CH2)nNC (n = 2,14 315) and the recently reported compound E (Scheme 1).16
This contribution describes the preparation and structural characterization of the new phosphino-isonitrile ligand 1 and its complexes with Ag(I) and Au(I) ions. Also reported are the results of preliminary catalytic tests with Au(I)-1 complexes aimed at a comparison with their Au(I)-D counterparts.
Considering the generally low stability of aminoferrocene derivatives, the often harsh reaction conditions required to obtain them,22 an also the sensitivity of phosphine groups to oxidation, the synthetic routes toward 1 were redesigned to include phosphine-protected intermediates that allow the introduction of the azide moiety (without an unwanted Staudinger reaction) and its subsequent reduction to amine group (Scheme 3).
Because some of us have successfully employed the protection of a phosphine group by thionation during the synthesis of Ph2PfcNHCH2t-Bu21a (fc = ferrocene-1,1′-diyl), a similar approach was adopted also for the synthesis of 1 (Scheme 3, left branch) with the prospect that removal of the P-bound sulfur atom and reduction of the azide group (–N3 → –NH2) can be effected in a single step by reacting intermediate 4S with Raney nickel. The starting phosphine bromide 3 was smoothly thionated with elemental sulfur and the stable P-sulfide 3S was lithiated and treated with 4-toluenesulfonyl azide (TsN3) to afford azide 4S in a good yield. A small amount of TsN3 present in the reaction product did not interfere during the following step, after which it could be easily removed. The subsequent reaction of 4S with Raney nickel and then with acetic formic anhydride provided the desired formamide 5 as a ca. 4:
5 mixture of (E) and (Z) isomers (N.B. the acylation was performed directly to prevent a possible decomposition of intermediate amine 2). However, the transformation of 4S into 5 typically suffered from low yields (below 30%) and the product was contaminated by the dephosphorylated amide, FcNHCHO (Fc = ferrocenyl).23
In the last step, which was the dehydration of formamide 5 to isonitrile 1, the standard reagents (POCl3/NEt3, COCl2/iPr2NH)24 failed, typically resulting in extensive darkening of the reaction mixture and oxidation of the phosphine moiety (confirmed by 31P NMR analysis). This led us to utilize the method previously used to convert oxime Ph2PfcCHNOH into nitrile D.25 Gratifyingly, addition of Castro's reagent (i.e., (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate, BOP) and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) to amide 5 ensued in a clean formation of isonitrile 1, which was isolated in a 71% yield following chromatographic purification.
Although the synthesis of 1 was successful, we sought for a more efficient synthetic procedure, utilizing borane as the protecting group (Scheme 3, right branch). The necessary starting material 3B was prepared by the reaction of phosphine-bromide 3 with BH3·SMe2 or, alternatively, via a practical one-pot procedure (lithiation, phosphinylation, borylation) from 1,1′-dibromoferrocene.18 Lithiation of 3B followed by quenching with TsN3 afforded azide 4B in a 89% yield. Compound 4B was found to be stable when stored at low temperatures in the dark but gradually decomposed upon exposure to direct day light. The subsequent reduction with Li[AlH4] in THF smoothly converted azide 4B into the protected amine 2B. This compound was in turn formylated to give 5B or isolated and converted the free phosphinoamine 2. Deprotection of 5B with 1,4-diazabicyclo[2.2.2]octane (dabco) or, alternatively, acylation of 2 with HCOOAc afforded formamide 5, which was in turn used to prepare the target isocyanide 1 as outlined above (see Scheme 3).
Although longer by one step, the synthesis of 1via borane-protected intermediates proved to be much more efficient in terms of the overall yield (compare the 70% yield of 1 from bromide 3 with ca. 25% yield for the 3 → 1 conversion via the PS intermediates) and selectivity. Besides, it provided a reliable access to amine 2 and its P-protected form 2B that are both attractive for further syntheses. Compound 2B appears to be particularly stable in both the solid state and solution. For instance, this adduct did not undergo any detectable decomposition or BH3 migration between the Lewis basic amine and phosphine groups when its solutions in CDCl3, CD3CN and C6D6 were stored at room temperature for 2 days. Accordingly, the reaction of 2 with 1 equiv. of BH3·SMe2 (in CDCl3) produced adduct 2B as the sole product (N.B. adduct 2·2BH3 was detected only when larger amounts of the borane source were employed).
Isocyanide 1 and all intermediates occurring en route to this compound were characterized by multinuclear NMR and IR spectroscopy, mass spectrometry and elemental analysis or HR MS measurements. In addition, the solid state structures of 1, 2, 4S, 4B, and 5 were determined by single-crystal X-ray diffraction analysis. The 1H and 13C NMR spectra confirmed the presence of an unsymmetrically 1,1′-disubstituted ferrocene moiety and the attached phosphorus groups in all cases. The manipulations at the phosphorus substituent were manifested in the 31P NMR spectra, showing broad signals at δP ≈ 16 for the BH3 adducts, and sharp singlets at δP ≈ −17 and 42 for the free phosphines and phosphine sulfides, respectively. In addition to characteristic B–H stretching bands of the borane adducts at 2340–2400 cm−1,26 the IR spectra showed distinct features due to the polar substituents, namely intense azide ν(N3) bands (4S: 2109 cm−1, 4B: 2108 cm−1) and amide ν(CO) vibrations (5 and 5B: 1663 cm−1). The band attributable to the ν(N
C) vibration of 1 was seen at 2126 cm−1 (cf. 2125 cm−1 for PhNC).27
Parameter | 4S (Y = S) | 4B (Y = B) | |
---|---|---|---|
mol 1 | mol 2 | ||
a Definitions: Cp1 and Cp2 are the nitrogen- and phosphorus-substituted cyclopentadienyl rings, respectively. Cg1 and Cg2 denote their centroids. τ = torsion angle C1–Cg1–Cg2–C6. 4S: n = void/5 for molecules 1/2, 4B: n = void. | |||
Fe–Cg1 | 1.652(1) | 1.649(2) | 1.654(1) |
Fe–Cg2 | 1.646(1) | 1.632 (1) | 1.6464(9) |
∠Cp1,Cp2 | 1.4(1) | 1.3(2) | 2.6(1) |
τ | −122.8(2) | 154.9(2) | 108.1(2) |
P–Cn6 | 1.790(2) | 1.790(3) | 1.790(2) |
P–Y | 1.9567(8) | 1.950(1) | 1.926(2) |
Cn1–Nα | 1.415(4) | 1.417(5) | 1.422(3) |
Nα–Nβ | 1.235(4) | 1.251(4) | 1.262(3) |
Nβ–Nγ | 1.130(4) | 1.143(5) | 1.123(4) |
Cn1–Nα–Nβ | 115.6(2) | 114.9(3) | 115.4(2) |
Nα–Nβ–Nγ | 173.3(3) | 171.3(4) | 172.1(3) |
The structures of 1 and 2 are displayed in Fig. 2. Relevant structural data are given in Table 2. The ferrocene unit in the structure of 1 has a synclinal eclipsed conformation (compare the τ angle in Table 2 with the ideal value of 72°)13a and is negligibly tilted. Its phosphine substituent is oriented so that one phenyl group points above the ferrocene scaffold while the other as well as the lone pair of electrons are directed to the sides. The length of the NC bond of 1.157(3) is identical to that in FcNC (1.157(5) Å)33 and the C1–N
C11 moiety is linear (177.3(2)°).
Parameter | 1 | 2 | 5 |
---|---|---|---|
a Definitions: Cp1 and Cp2 are the cyclopentadienyl rings C(1–5) and C(6–10), respectively. Cg1 and Cg2 denote their centroids. τ = torsion angle C1–Cg1–Cg2–C6. b Further data: C11–N = 1.157(3), C1–N–C11 = 177.3(2). c Further data: N–C24 = 1.338(2), C1–N–C24 = 126.5(1), C24–O = 1.227(2), N–C24–O = 125.1(2). | |||
Fe–Cg1 | 1.6438(8) | 1.6585(7) | 1.6482(7) |
Fe–Cg2 | 1.6431(8) | 1.6467(7) | 1.6408(6) |
∠Cp1,Cp2 | 1.4(1) | 1.09(9) | 2.79(9) |
τ | −70.0(1) | 69.0(1) | −86.3(1) |
P–C6 | 1.814(2) | 1.810(1) | 1.813 (1) |
C1–N | 1.391(2) | 1.410(2) | 1.407(2) |
The arrangement of the phosphinoferrocene moiety in the structure of amine 2 is practically the same as in 1, including the orientation of the cyclopentadienyl rings, and the C1–N bond in 2 has the same length as that in aminoferrocene (1.405(5) Å).34 Notably, the crystal structure of amine 2 lacks classical N–H⋯N hydrogen bonds. However, one of the amine hydrogen atoms (H1N) appears to be involved in an intramolecular N–H⋯π interaction, being directed towards the phenyl ring C(18–23) with an H⋯Cg distance (Cg is the ring centroid) of 2.93 Å.
Recrystallization of formamide 5 from chloroform/hexane furnished crystals of the major (Z) isomer, which were used for the structure determination. In the crystal, compound 5 forms infinite chains via N–H1N⋯O hydrogen bridges (N⋯O = 2.808(2) Å) between molecules distributed around crystallographic glide planes (Fig. 3 and Table 2). The individual molecules show a minor tilting at their ferrocene units (ca. 3°) and an intermediate conformation between synclinal eclipsed and anticlinal staggered. The amide moiety is coplanar with its parent cyclopentadienyl ring (dihedral angle: 0.8(2)°), which suggests conjugation of these molecular parts.
![]() | ||
Fig. 3 Section of the hydrogen-bonded chain in the structure of 5 as viewed along the crystallographic a axis. For clarity, the CHn hydrogen atoms are omitted. |
A defined, though also practically insoluble, product (N.B the compound did not dissolve even in MeCN or DMSO) resulted upon reacting ligand 1 (1 or 2 equiv.) with freshly prepared AgCl (Scheme 4). X-ray diffraction analysis on crystalline 6 obtained by reaction of AgCl with 2 equiv. of 1 in chloroform and crystallization by addition of hexane revealed that the structure of 6 is built up from diamond-shaped {Ag2(μ-Cl)2} fragments that are interconnected by four P,C-bridging ligands 1 into an infinite one-dimensional chain (Fig. 4). Although central Ag2Cl2 motifs were found in the structures of, e.g., [(Ph3P)2Ag(μ-Cl)]235 and [(dppf-κ2P,P′)Ag(μ-Cl)]2,36 the only related compound featuring two different donors whose structure has been reported to date is the dinuclear complex [(Ph3P)(MeNC)Ag(μ-Br)]2.37 Indeed, the structures of 6 and the latter compound are similar except that in 6 the two donor moieties are tethered by the ferrocene unit, which in turn results in the formation of a polymeric assembly. It is also noteworthy that ligand D comprising the relatively harder cyano group reacted with AgCl to give heterocubane [Ag(μ3-Cl)(D-κP)]4 (Ag
:
D = 1
:
1) or the dimers [Ag(D-κP)2(μ-Cl)]2 and [AgCl(D-κP)(μ(P,N)-D)]2 (Ag
:
D = 1
:
2).12c
The structure of 6 is presented in Fig. 4 along with selected distances and angles. Although the silver atoms appear disordered over two positions differently positioned between the phosphine and isonitrile donors (refined ratios: ≈97:
3), the overall structure is rather symmetrical. The central Ag2Cl2 units are practically regular squares and lie on crystallographic inversion centers. Each silver(I) ion is further coordinated by two phosphino-isonitrile ligands 1, once via the phosphorus atom and once through the isonitrile moiety. Both Ag–P and Ag–C bonds are shorter than the sum of the respective covalent radii (∑rcov(Ag,P) = 2.52 Å, ∑rcov(Ag,Csp) = 2.14 Å)38 and the observed Ag–C distance (2.164(3) Å) is close to the average Ag–C distances in Ag–isonitrile complexes [2.14(8) Å (ref. 39)]. The coordination environment of the silver ions is distorted tetrahedral. Among the interligand angles, the Cl–Ag1–Cl′ angle is the most acute (90°) and the C11′′–Ag1–Cl (120°) and P–Ag1–C11′′ (118°) angles are the most opened.
The ferrocene moiety in the structure of 6 is roughly perpendicular to the Ag2Cl2 ring (cf. the dihedral angle of the C(1–5) ring and the Ag2Cl2 plane of 82.6(1)°) and has an intermediate conformation with τ of −52.5(2)°. Notably, the length of the coordinated CN bond (1.163(4) Å) is indistinguishable within experimental error from that in free 1.
Addition of ligand 1 (1 equiv.) to Ag[SbF6] containing a weakly coordinating anion in acetone led to the dimeric complex [Ag2{μ(P,C)-1}2(Me2CO-κO)2][SbF6]2 (7 in Scheme 5). This compound is structurally similar to [Ag2{μ(P,N)-D}2(AcOEt-κO)2][SbF6]2 obtained from Ag[SbF6] and ligand D.12c Unlike the latter compound, however, complex 7 appears to be stable in solution, which was manifested by a sharp 31P NMR signal at δP 6.8 split into a pair of concentric doublets by interactions with 109Ag and 107Ag (1JAg,P = 709 and 615 Hz). Coordination of the isonitrile moiety was indicated by a shift of the ν(NC) band in the IR spectrum to 2210 cm−1 (by 84 cm−1 to higher energies with respect to 1). The IR spectrum further confirmed the presence of coordinated acetone through a sharp band of the ν(C
O) vibration at 1695 cm−1, which is 20 cm−1 less than for neat acetone due to coordination.40
Upon increasing the amount of the phosphino-isonitrile ligand to 2 molar equiv., Ag[SbF6] was smoothly converted to the quadruply-bridged disilver(I) complex [Ag2{μ(P,C)-1}4][SbF6]2 (8), which resembles an analogous Cu(I) complex obtained from ligand D, [Cu2{μ(P,N)-D}4][SbF6]2.12a In its 31P NMR spectrum, complex 8 gave rise to a broad doublet at δP −1.2 (1JAg,P = 207 Hz).41 The IR band due to coordinated isonitrile groups was observed at 2167 cm−1, i.e. shifted by ca. 40 cm−1 to higher energies compared to uncoordinated ligand 1.
Compounds 7 and 8 have been structurally authenticated by X-ray diffraction analysis. The complex cations in the crystal structure of 7 (Fig. 5) lie around crystallographic inversion centers, which makes only their halves structurally independent. Their tricoordinate silver ions exhibit an almost linear arrangement of the ligating P and C atoms, with a minor distortion due to the coordinated acetone (P–Ag–C ≈ 166°). The Ag–P and Ag–C bonds in 7 are shorter than those in 6 (by 0.07 and 0.05 Å), suggesting stronger dative bonds in the former cationic complex. In contrast, the Ag–O distance is substantially elongated (compare Ag–O1S ≈ 2.63 Å with ∑rcov(Ag,O) = 2.11 Å), presumably due to a relatively weaker coordination and steric reasons.
The cyclopentadienyl rings in 7 are tilted by 2.4(2)° and adopt a conformation near to synclinal eclipsed (τ = 83.8(1)°), which brings the phosphine moiety to the side of the fc-NC moiety (cf. the angle subtended by the P–C6 and C1–N bonds of 79.7(2)°). Consequently, the P–Ag bond points to the same direction as the NC moiety, which in turn allows the formation of dimeric units Ag2(μ(P,C)-1)2 consisting of two equivalent parts arranged in a side-by-side manner that laterally coordinate the acetone molecules.
The structure determination on 8·3Me2CO (Fig. 6) revealed a compact and symmetrical complex molecule located around a crystallographic two-fold axis (space group C2/c; the silver atoms reside on this axis). Each silver(I) ion has a distorted tetrahedral P2C2 donor set being coordinated by four P,C-bridging ligands 1. The lengths of the two structurally independent Ag–P bonds differ by ca. 0.036 Å. A more significant asymmetry observed for the Ag–CN bonds (0.059 Å) is not relayed further as the CN bonds are similar in length and the Ag–C
N and Cp–N
C moieties remain linear. Despite the very different steric demands of the donor moieties, the interligand angles around the silver(I) ions do not depart much from the tetrahedral value, spanning a relatively narrow range of 103.35(9)–115.88(3)°.
The reactions of 1 with [AuCl(tht)] (tht = tetrahydrothiophene) paralleled the chemistry noted in the Au(I)-D system only partly (Scheme 6). Depending on the ligand-to-metal ratio, the reaction of 1 with [AuCl(tht)] afforded either the phosphine complex [AuCl(1-κP)] (9) or the trinuclear Au2Fe complex 10. Both these products are poorly soluble (especially when crystallized), which makes their full characterization by solution techniques (e.g., NMR) impossible. Nevertheless, the coordination of the phosphine moiety in 9 could be inferred from a shift of the 31P NMR signal to a lower field (δP 29.0). The IR spectrum recorded with a solid sample (Nujol mull) displayed two bands attributable to the free (2126 cm−1) and coordinated (2220 cm−1, weak band; cf. νNC 2223 cm−1 for 10) isonitrile moieties. Although unexpected, this observation is in line with the result of the structure determination revealing that a small fraction of the gold centers in the structure of 9 is displaced towards the isonitrile group of an adjacent molecule (vide infra). This phenomenon appears to be limited to the solid state as an NMR study ruled out the formation of isomeric monogold complexes (with P- and NC-bound ligand) and other species (e.g., 1 and 10 formed by redistribution).
The structures of 9 and 10 are shown in Fig. 7 along with selected geometric data. As stated above, the gold(I) ions in the structure of 9 are disordered over two positions (refined occupancies: Au1 ≈ 0.98, Au2 ≈ 0.02; the ligand is considered invariant). In the dominant position, the gold(I) ion has the usual linear coordination whilst in the other it is approximately trigonal with the isonitrile moiety located at a bonding distance (Au2–C11 ≈ 2.09 Å, ∑rcov(Au,Csp) = 2.05 Å). The ferrocene unit in 9 has a synclinal eclipsed conformation (τ = 70.3(2)°) which, together with the spatial orientation of the phenyl rings, allows for a compact arrangement of the linear assembly interlinked via the incidental P–Au2–NC interactions.
In the structure of 10, both gold centers are linearly coordinated and averted from each other because the central ferrocene unit has an opened conformation with τ = −157.0(3)° (N.B. the angle subtended by the Au1–Cl1 and Au2–Cl2 bonds is 139.26(6)°). Whereas the entire C1–NC11–Au2–Cl2 moiety is essentially linear, the Au1–Cl1 bond diverts from the plane of the parent cyclopentadinyl ring at an angle of 23.1(2)°. On the other hand, the coordination geometry parameters are not unexpected in view of the data reported for [Au2Cl2(μ(P,P′)-dppf)]42 and [AuCl(D-κP)].12c In the crystal, the molecules of 10 assemble into head-to-tail dimers via weak Au1⋯Au2 aurophilic interactions (3.21 Å; see the ESI, Fig. S12†).43
Finally, the reaction of [Au(tht)2][SbF6] with 1 (1 equiv.) or removal of the chloride ligand from 9 with AgNTf2 resulted in the formation of the respective dimeric complexes 11 (Scheme 6), which are the structural isomers of the recently reported compounds [Au2(μ(P,N)-D)2]X2 (X = SbF6 and NTf2).12b The dimeric structure of 11a and 11b was corroborated by X-ray diffraction analysis (N.B. the structure of 11b could not be adequately refined because of a severe disorder of the NTf2− anion). The coordination of both donor moieties available in ligand 1 is indicated by a shift of the 31P NMR signals to low fields (δP 32–33) and through a shift of the νNC bands in the IR spectra to higher energies (2231–2233 cm−1). Notably, both shifts are more pronounced than for the neutral complexes 9 and 10, very likely owing to a stronger interaction of the donor moieties with the electron-poor cationic Au(I) centers.
The solid-state structure of 11a·2Me2CO shown in Fig. 8 resembles that of 7, except that the coordination of the Au centers is practically undistorted linear (P–Au–C = 175.8(1)°). The ferrocene cyclopentadienyl rings adopt a conformation similar to that in 7 with τ of −80.0(3)°, which brings the linear P–Au–NC subunits side-by-side (N.B. the angle subtended by the P–Au and C11–Au′ bonds is only 4.17(1)°), though without any supporting intramoleculars aurophilic interaction (Au⋯Au′ = 5.4400(4) Å).
Compound 1 (Fig. 9) was oxidized in a single irreversible step at 0.38 V vs. the ferrocene/ferrocenium reference couple (anodic peak potential, Epa, is given at a scan rate of 100 mV s−1), which corresponds with an electron-withdrawing nature of the substituents at the ferrocene unit (cf. the Hammett σp constant: 0.46 for –NC, and 0.19 for –PPh2).44 This primary redox change attributable to the oxidation of the ferrocene moiety is followed by another irreversible redox event at a more positive potential (Epa ≈ 0.75 V).
In contrast, the oxidation of amines 2 and 2B was reversible (Fig. 9). However, the waves were shifted to less positive potentials (E°′ = −0.24 V and −0.13 V for 2 and 2B, respectively) due to the electron-donating nature of the amine substituent (σp = −0.66). Even in this case, the first oxidations were followed by irreversible processes at higher potentials.
The cyclic voltammogram of the monogold complex 9 showed two redox events in the anodic region, namely an irreversible oxidation at Epa ≈ 0.61 V and a reversible redox process at E°′ = 0.78 V (Fig. 10). Since the digold complex 10 displayed a single reversible redox change at E°′ = 0.76 V, it appears likely that the redox response of 9 can be affected by adsorption phenomena. A single reversible redox event was observed also for the dinuclear complexes 11a and 11b, whose behavior was expectedly identical (E°′ = 0.79 V; see Fig. 10).
Unfortunately, the collected results (Table 3) indicate a generally very low (if any at all) catalytic activity of the prepared Au-1 complexes. For instance, compound 10 achieved a 82% yield of the cyclization product 13 after 30 min and a nearly 90% yield after 3 h at 1 mol% Au loading. These yields decreased substantially upon lowering the catalyst amount to 0.1 mol%. The monogold complex 9 and, surprisingly, also the dimers 11 proved to be catalytically inactive, which markedly contrasts with the very high catalytic activity of [Au2(μ(P,N)-D)2]X2 (X = SbF6, NTf2).12b
Complex | Au loading [mol.%] | Yield of 13 after 30 min [%] | Yield of 13 after 3 h [%] |
---|---|---|---|
a Compound 12 (1 mmol) and 1,2-dichloroethane (internal standard; 1 mmol) were dissolved in CDCl3 (2 mL). The respective catalyst was added and the reaction mixture was stirred at room temperature for a given time (the amount of the starting materials was doubled for reactions with 0.1 mol% Au). The yields were determined by integration of 1H NMR spectra. | |||
9 | 1.0 | 0 | 0 |
10 | 1.0 | 82 | 89 |
10 | 0.1 | 64 | 75 |
11a | 1.0 | 0 | 0 |
11b | 1.0 | 0 | 0 |
Tentatively, we ascribed the observed low catalytic activity of the Au-1 complexes (particularly the dimers 11) to a relatively stronger coordination of the isonitrile moiety, which prevents the formation of coordinatively unsaturated Au(I) species by dissociation of the Au–CN bonds. This assumption was supported by the results of DFT computations performed on the isolated cations [Au2(μ(P,N)-L)2]2+, where L = D or 1 (Table 4), which indeed revealed that the dissociation of the phosphinonitrile-bridged dimers (L = D) to the monomeric species [Au(D)]+ is by approximately 12 kcal mol−1less endergonic than for the corresponding dimeric cation containing the isomeric ligand 1 (27.2 vs. 39.4 kcal mol−1).45
[Au2(μ(P,N)-D)2]2+ | [Au2(μ(P,N)-1)2]2+ | ||||
---|---|---|---|---|---|
Parameter | X-rayb | DFT | Parameter | X-Rayc | DFT |
a The calculations were performed at the PBE0/cc-pVDZ![]() ![]() |
|||||
Au–N | 2.035(4) | 2.054 | Au–C | 2.008(4) | 1.996 |
C![]() |
1.139(8) | 1.160 | N![]() |
1.135(5) | 1.164 |
Au–P | 2.225(2) | 2.281 | Au–P | 2.282(1) | 2.333 |
N–Au–P | 175.1(2) | 175.7 | C–Au–P | 175.8(1) | 175.3 |
Au–N–C | 168.2(5) | 170.6 | Au–C–N | 174.3(4) | 175.4 |
The NMR spectra were recorded at 25 °C on a Varian UNITY Inova 400 or a Bruker Avance III 400 spectrometer. Chemical shifts (δ in ppm) are given relative to an internal tetramethylsilane (1H and 13C) and an external 85% H3PO4 standard (31P), all set to 0 ppm. In addition to the usual notation of signal multiplicity, vt and vq are used to distinguish virtual triplets and quartets due to ferrocene protons constituting the AA′BB′ and AA′BB′X spin systems in the nitrogen- and PPh2-substituted cyclopentadienyl rings, respectively (fc = ferrocene-1,1′-diyl). FTIR spectra were measured with a Nicolet 6700 spectrometer in a range of 400–4000 cm−1. Electrospray ionization (ESI) mass spectra were obtained on an Esquire 3000 (Bruker) spectrometer using samples dissolved in HPLC-grade methanol. High resolution (HR) measurements were performed with an LTQ Orbitrap XL spectrometer (Thermo Fisher Scientific). The assignment of the observed ions was based on a comparison of the theoretical and experimental isotopic patterns. Elemental analyses were determined with a PerkinElmer PE 2400 CHN analyzer.
The cyclic voltammograms were recorded with a μAUTOLAB III instrument (Eco Chemie, The Netherlands) at ambient temperature using samples dissolved in dry dichloromethane (sample concentration 0.5 mM or a saturated solution in the case of poorly soluble complexes) and Bu4N[PF6] as the supporting electrolyte (0.1 M). A glassy carbon disc (2 mm diameter) was employed as a working electrode, Ag/AgCl (3 M LiCl/EtOH) as a reference electrode and platinum sheet as a counter electrode. Decamethylferrocene was added as an internal reference for the final scans but the potentials were converted to the ferrocene/ferrocenium scale by subtracting by 0.548 V.50
1H NMR (CDCl3): δ 4.07 (vt, J′ = 2.0 Hz, 2 H, fc), 4.23 (vt, J′ = 2.0 Hz, 2 H, fc), 4.54 (vq, J′ = 2.1 Hz, 2 H, fc), 4.63 (vq, J′ = 2.1 Hz, 2 H, fc), 7.40–7.51 (m, 6 H, P(S)Ph2), 7.69–7.75 (m, 4 H, P(S)Ph2). 13C{1H} NMR (CDCl3): δ 62.07 (CH of fc), 67.82 (CH of fc), 73.19 (d, J = 10 Hz, CH of fc), 73.84 (d, J = 12 Hz, CH of fc), 100.51 (Cipso–N3 of fc), 128.26 (d, 2JPC = 12 Hz, CHortho of Ph), 131.31 (d, 4JPC = 2 Hz, CHpara of Ph), 131.59 (d, 3JPC = 10 Hz, CHmeta of Ph), 134.36 (d, 1JPC = 87 Hz, Cipso of Ph). The signals due to Cipso–P of fc was not found. 31P{1H} NMR (CDCl3): δ 41.7 (s). IR (Nujol): νmax 3049 w, 2109 s (N3), 1308 w, 1287 m, 1193 w, 1170 m, 1102 s, 1069 w, 1026 m, 998 w, 917 w, 837 m, 828 m, 754 m, 716 s, 695 s, 656 s, 629 w, 615 w, 541 m, 523 m, 496 m, 448 w cm−1. ESI+ MS: m/z 438 ([M − N2 + Na]+), 466 ([M + Na]+). HRMS calc. for C22H1856FeN3PS (M+): 443.0308, found 443.0309.
Notably, when the reaction was performed in dry acetonitrile, the unwanted dephosphorylation leading to FcNHCHO was suppressed but the yield of 5 was only 13%. Practically no desulfurization (only conversion of the azide to formamide) was observed in 1,2-dimethoxyethane under similar conditions (room temperature, 3 days), while in anhydrous ethanol the starting azide was converted to the N-alkylated products FcN(Et)CHO and Ph2PfcN(Et)CHO in ca. 1:
1 ratio (ESI+ MS data for Ph2PfcN(Et)CHO: m/z 442 ([M + H]+), 464 ([M + Na]+), 480 ([M + K]+)).
1H NMR (CDCl3): δ 0.8–1.7 (very br m, 3 H, BH3), 4.08 (vt, J′ = 1.9 Hz, 2 H, fc), 4.33 (vt, J′ = 1.9 Hz, 2 H, fc), 4.46 (vq, J′ = 1.8 Hz, 2 H, fc), 4.55 (vdt, J′ = 1.8 Hz, 1.2 Hz, 2 H, fc), 7.39–7.50 (m, 6 H, PPh2), 7.55–7.61 (m, 4 H, PPh2). 13C{1H} NMR (CDCl3): δ 69.44 (CH of fc), 70.49 (d, 1JPC = 68 Hz, Cipso–P of fc), 71.67 (CH of fc), 74.87 (d, JPC = 9 Hz, CH of fc), 75.47 (d, JPC = 7 Hz, CH of fc), 77.72 (Cipso–Br of fc), 128.50 (d, 2JPC = 10 Hz, CHortho of Ph), 130.96 (d, 1JPC = 60 Hz, Cipso of Ph), 131.01 (d, 4JPC = 2 Hz, CHpara of Ph), 132.61 (d, 3JPC = 9 Hz, CHmeta of Ph). 31P{1H} NMR (CDCl3): δ 16.2 (br d, J ≈ 75 Hz). IR (Nujol): νmax 3102 w, 3073 w, 3056 w, 2398 s (BH3), 2373 s (BH3), 2344 m (BH3), 1350 m, 1309 m, 1195 m, 1181 m, 1172 s, 1157 w, 1132 w, 1108 s, 1063 s, 1026 s, 1000 m, 978 w, 930 w, 895 w, 872 s, 838 s, 828 w, 818 m, 766 w, 743 s, 703 s, 696 s, 643 s, 622 w, 610 m, 568 w, 527 m, 506 s, 496 s, 476 s, 461 s, 440 m (cm−1). ESI+ MS: m/z 448 ([M − BH3 + H]+), 485 ([M + Na]+). Anal. calc. for C22H21BBrFeP (462.9): C 57.08, H 4.57. Found: C 57.32, H 4.55%.
Note: TsN3 must be dried by stirring with CaH2 freshly prior to the use (preferably overnight). Only if such carefully dried TsN3 is used, the reaction product is contaminated by less than 5 mol% of FcPPh2·BH3. Otherwise, the amount of FcPPh2·BH3 and unreacted TsN3 are higher. Azide 4B does not decompose when stored in the dark at 4 °C for weeks. If appropriate, however, it can be purified by column chromatography as specified above.
1H NMR (CDCl3): δ 0.8–1.6 (very br m, 3 H, BH3), 4.00 (vt, J′ = 2.0 Hz, 2 H, fc), 4.16 (vt, J′ = 2.0 Hz, 2 H, fc), 4.52 (vq, J′ = 1.8 Hz, 2 H, fc), 4.65 (vdt, J′ = 1.8 Hz, 1.1 Hz, 2 H, fc), 7.38–7.50 (m, 6 H, PPh2), 7.56–7.62 (m, 4 H, PPh2). 13C{1H} NMR (CDCl3): δ 61.85 (CH of fc), 67.50 (CH of fc), 70.12 (d, 1JPC = 68 Hz, Cipso–P of fc), 73.33 (d, JPC = 8 Hz, CH of fc), 73.70 (d, JPC = 10 Hz, CH of fc), 100.41 (Cipso–N3 of fc), 128.49 (d, 2JPC = 10 Hz, CHortho of Ph), 131.00 (d, 4JPC = 2 Hz, CHpara of Ph), 131.01 (d, 1JPC = 60 Hz, Cipso of Ph), 132.58 (d, 3JPC = 9 Hz, CHmeta of Ph). 31P{1H} NMR (CDCl3): δ 16.2 (br d). IR (Nujol): νmax 3077 w, 3054 w, 2382 s (BH3), 2338 m (BH3), 2108 s (N3), 1314 w, 1285 s, 1223 w, 1176 s, 1161 m, 1134 m, 1107 s, 1061 s, 1036 m, 1028 s, 999 w, 920 w, 832 s, 820 m, 760 m, 741 s, 703 s, 692 m, 635 m, 625 m, 611 m, 595 w, 528 s, 489 s, 463 m, 446 w, 409 w cm−1. ESI+ MS: m/z 420 ([M – N2 + Na]+), 448 ([M + Na]+). HRMS calc. for C22H21B56FeN3P (M+): 425.0916, found 425.0921.
1H NMR (CDCl3): major – δ 0.8–1.7 (very br m, 3 H, BH3), 3.90 (vt, J′ = 2.0 Hz, 2 H, fc), 4.29 (vq, J′ = 1.8 Hz, 2 H, fc), 4.59 (vdt, J′ = 1.8 Hz, 1.2 Hz, 2 H, fc), 4.69 (vt, J′ = 2.0 Hz, 2 H, fc), 6.71 (br s, 1 H, NH), 7.39–7.52 (m, 6 H, PPh2), 7.56–7.63 (m, 4 H, PPh2), 8.06 (d, 3JHH = 1.1 Hz, 1 H, CHO); minor – δ 0.8–1.7 (very br m, 3 H, BH3), 4.01 (vt, J′ = 1.9 Hz, 2 H, fc), 4.25 (vt, J′ = 2.0 Hz, 2 H, fc), 4.41 (vq, J′ = 1.8 Hz, 2 H, fc), 4.58 (vdt, J′ = 1.9 Hz, 1.2 Hz, 2 H, fc), 6.74 (br s, 1 H, NH), 7.39–7.52 (m, 6 H, PPh2), 7.56–7.63 (m, 4 H, PPh2), 8.14 (d, 3JHH = 11.6 Hz, 1 H, CHO). 13C{1H} NMR (CDCl3): major – δ 63.90 (CH of fc), 66.15 (CH of fc), 69.22 (d, 1JPC = 69 Hz, Cipso–P of fc), 73.15 (d, JPC = 8 Hz, CH of fc), 74.22 (d, JPC = 10 Hz, CH of fc), 93.59 (Cipso–N of fc), 128.54 (d, 2JPC = 10 Hz, CHortho of Ph), 130.95 (d, 1JPC = 60 Hz, Cipso of Ph), 131.04 (d, 4JPC = 2 Hz, CHpara of Ph), 132.65 (d, 3JPC = 9 Hz, CHmeta of Ph), 159.12 (CHO); minor – δ 62.56 (CH of fc), 67.17 (CH of fc), 70.18 (d, 1JPC = 68 Hz, Cipso–P of fc), 73.28 (d, JPC = 8 Hz, CH of fc), 74.21 (d, JPC = 10 Hz, CH of fc), 95.04 (Cipso–N of fc), 128.59 (d, 2JPC = 10 Hz, CHortho of Ph), 130.82 (d, 1JPC = 60 Hz, Cipso of Ph), 131.19 (d, 4JPC = 2 Hz, CHpara of Ph), 132.57 (d, 3JPC = 10 Hz, CHmeta of Ph), 162.39 (CHO). 31P{1H} NMR (CDCl3): 16.1 (br d, both isomers). IR (Nujol): νmax 3275 br m, 3230 br m, 3082 m, 3054 m, 2374 s (BH3), 2343 m (BH3), 1687 m, 1663 s (CHO), 1582 m, 1564 s, 1353 w, 1310 w, 1267 w, 1258 w, 1173 s, 1133 w, 1107 m, 1057 s, 1029 s, 999 w, 927 w, 837 w, 830 w, 813 w, 759 w,, 744 s, 701 s, 636 m, 623 w, 612 w, 528 m, 500 s, 475 s, 463 w, 447 w cm−1. ESI+ MS: m/z 450 ([M + Na]+), 466 ([M + K]+). HRMS calc. for C23H23B56FeNOP (M+): 427.0960, found 427.0965. Anal. calc. for C23H23BFeNOP (427.0): C 64.68, H 5.43, N 3.28%. Found: C 64.50, H 5.08, N 3.23%.
1H NMR (CDCl3): δ 0.8–1.7 (very br m, 3 H, BH3), 2.51 (br s, 2 H, NH2), 3.71 (vt, J′ = 1.9 Hz, 2 H, fc), 3.97 (vt, J′ = 1.9 Hz, 2 H, fc), 4.25 (vq, 2 H, J′ = 1.8 Hz, 2 H, fc), 4.48 (v dt, J′ = 1.8 Hz, 1.1 Hz, 2 H, fc), 7.38–7.48 (m, 6 H, PPh2), 7.58–7.64 (m, 4 H, PPh2). 13C{1H} NMR (CDCl3): δ 59.76 (CH of fc), 64.76 (CH of fc), 68.42 (d, 1JPC = 70 Hz, Cipso–P of fc), 72.48 (d, 3JPC = 8 Hz, CH of fc), 73.78 (d, 2JPC = 10 Hz, CH of fc), 107.37 (Cipso–N of fc), 128.39 (d, 2JPC = 10 Hz, CHortho of Ph), 130.82 (d, 4JPC = 2 Hz, CHpara of Ph), 131.54 (d, 1JPC = 59 Hz, Cipso–P of Ph), 132.62 (d, 3JPC = 9 Hz, CHmeta of Ph). 31P{1H} NMR (CDCl3): δ 16.4 (br d). IR (Nujol): νmax 3416 m, 3385 m, 3332 m, 3076 m, 3058 w, 2380 s (BH3), 2255 w (BH3), 1503 s (NH2), 1305 w, 1252 w, 1194 w, 1173 s, 1134 m, 1106 s, 1060 s, 1041 m, 1026 s, 998 w, 934 w, 850 m, 817 s, 796 m, 767 m, 744 s, 735 s, 700 s, 689 s, 637 s, 621 m, 613 m, 529 m, 502 s, 471 s, 460 m, 442 w, 417 w, 411 w cm−1. ESI+ MS: m/z 398 ([M − H]+). HRMS calc. for C22H23B56FeNP (M+): 399.1011, found 399.1018. Anal. calc. for C22H23BFeNP (399.0): C 66.21, H 5.81, N 3.51%. Found: C 66.10, H 5.93, N 3.50%.
1H NMR (CDCl3): δ 2.25 (br s, 2 H, NH2), 3.78 (vt, J′ = 1.8 Hz, 2 H, fc), 3.90 (vt, J′ = 1.7 Hz, 2 H, fc), 4.00 (vt, J′ = 1.8 Hz, 2 H, fc), 4.33 (vt, J′ = 1.6 Hz, 2 H, fc), 7.28–7.34 (m, 6 H, PPh2), 7.36–7.43 (m, 4 H, PPh2). 13C{1H} NMR (CDCl3): δ 59.47 (CH of fc), 64.42 (CH of fc), 71.57 (d, 3JPC = 3 Hz, CH of fc), 73.78 (d, 2JPC = 15 Hz, CH of fc), 75.41 (d, 1JPC = 4 Hz, Cipso–P of fc), 106.05 (Cipso–N of fc), 128.13 (d, 3JPC = 6 Hz, CHmeta of Ph), 128.46 (CHpara of Ph), 133.54 (d, 2JPC = 19 Hz, CHortho of Ph), 139.47 (d, 1JPC = 9 Hz, Cipso of Ph). 31P{1H} NMR (CDCl3): δ −16.7 (s). The NMR data are in accordance with the literature.19
1H NMR (CDCl3): δ 4.02 (vt, J′ = 1.9 Hz, 2 H, fc), 4.22 (vq, J′ = 1.9 Hz, 2 H, fc), 4.43 (vt, J′ = 2.0 Hz, 2 H, fc), 4.51 (vt, J′ = 1.9 Hz, 2 H, fc), 7.31–7.38 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): δ 67.61 (CH of fc), 68.19 (CH of fc), 73.92 (d, JPC = 4 Hz, CH of fc), 74.96 (d, JPC = 14 Hz, CH of fc), 78.78 (d, JPC = 9 Hz, Cipso–P), 128.31 (d, 3JPC = 7 Hz, CHmeta of Ph), 128.79 (CHpara of Ph), 133.42 (d, 2JPC = 20 Hz, CHortho of Ph), 138.27 (d, 1JPC = 10 Hz, Cipso of Ph), 164.30 (NC). The resonance due to ferrocene Cipso–NC is probably obscured by the solvent signal. 31P{1H} NMR (CDCl3): δ −17.8 (s). 1H NMR (acetone-d6): δ 4.10 (vt, J′ = 2.0 Hz, 2 H, fc), 4.23 (vq, J′ = 1.8 Hz, 2 H, fc), 4.57 (vt, J′ = 2.1 Hz, 2 H, fc), 4.59 (vt, J′ = 1.8 Hz, 2 H, fc), 7.37–7.41 (m, 10 H, PPh2). 31P{1H} NMR (acetone-d6): δ −17.3 (s). IR (Nujol): νmax 3114 w, 3054 w, 2126 s (NC), 1231 w, 1193 w, 1160 m, 1089 w, 1028 s, 999 w, 916 w, 836 m, 819 s, 747 s, 698 s, 639 w, 596 w, 531 w, 510 s, 502 m, 488 m, 458 w, 432 w, 414 w cm−1. ESI+ MS: m/z 396 ([M + H]+). Anal. calc. for C23H18FeNP (395.2): C 69.90, H 4.59, N 3.54%. Found: C 69.79, H 4.63, N 3.35%.
IR (Nujol): νmax 3114 w, 3081 w, 3052 w, 2160 s (NC), 2140 m (N
C), 1311 w, 1233 w, 1194 m, 1168 m, 1100 s, 1070 w, 1036 m, 1025 m, 910 m, 832 m, 824 m, 751 m, 741 vs, 696 vs, 631 w, 613 w, 594 w, 535 m, 515 s, 503 s, 489 s, 470 s, 459 m, 442 w, 427 m cm−1. ESI+ MS: m/z 502 ([Ag(1)]+), 704 ([Ag2(1)Cl2 + Na]+). Anal. calc. for C23H18AgClFeNP·0.2CHCl3 (562.4): C 49.54, H 3.26, N 2.49%. Found: C 49.36, H 3.19, N 2.40%.
1H NMR (in situ, acetone-d6): δ 4.26 (br s, 2 H, fc), 4.60 (br s, 2 H, fc), 5.01 (vt, J′ = 1.7 Hz, 2 H, fc), 5.14 (br s, 2 H, fc), 7.54–7.71 (m, 10 H, PPh2). 31P{1H} NMR (in situ, acetone-d6): δ 6.8 (pair of d, 1JAgP = 709 (109Ag), 615 (107Ag) Hz). IR (Nujol): νmax IR (Nujol): νmax 3119 w, 3050 w, 2210 m (NC), 1695 s (acetone, C
O), 1316 w, 1230 m, 1198 w, 1173 m, 1101 m, 1059 w, 1034 m, 1001 w, 920 m, 848 w, 821 w, 750 s, 699 s, 664 vs, 653 vs, 542 w, 513 s, 472 m, 445 w, 430 m cm−1. ESI+ MS: m/z 395 (1+), 502 ([Ag(1)]+), 646 ([Ag2(1) + Cl]+), 897 ([Ag(1)2]+). Anal. calc. for C23H18AgF6FeNPSb·(CH3)2CO (796.9): C 39.18, H 3.04, N 1.76%; found C 39.49, H 3.07, N 1.72%.
1H NMR (in situ, acetone-d6): δ 4.20 (br s, 2 H, fc), 4.71 (br s, 2 H, fc), 5.02 (br s, 2 H, fc), 5.10 (br s, 2 H, fc), 7.31–7.37 (m, 4 H, PPh2), 7.42–7.50 (m, 6 H, PPh2). 31P{1H} NMR (in situ, acetone-d6): δ −1.2 (br d, 1JAgP = 207 Hz). IR (Nujol): νmax 3054 w, 2167 m (NC), 1309 m, 1261 w, 1233 w, 1195 m, 1166 s, 1098 s, 1030 s, 999 m, 917 s, 890 w, 829 s, 743 s, 696 s, 658 vs, 584 w, 519 m, 508 s, 494 s, 476 m, 464 m, 426 w cm−1. ESI+ MS: m/z 395 (1+), 897 ([Ag(1)2]+), 1688 ([Ag(1)4]+). Anal. calc. for C46H36AgF6Fe2N2P2Sb (1134.0): C 48.72, H 3.20, N 2.47%. Found: C 48.34, H 3.12, N 2.37%.
1H NMR (acetone-d6): δ 4.31 (vt, J′ = 2.0 Hz, 2 H, fc), 4.63 (d vt, 3JPH = 3.1 Hz, J′ = 2.0 Hz, 2 H, fc), 4.73 (vt, J′ = 2.0 Hz, 2 H, fc), 4.88 (d vt, 4JPH = 1.1 Hz, J′ = 2.0 Hz, 2 H, fc), 7.57–7.74 (m, 10 H, PPh2). 31P{1H} NMR (acetone-d6): δ 29.0 (s). IR (Nujol): νmax 3087 w, 3052 w, 2220 w, 2125 s (NC), 1686 w, 1560 w, 1310 m, 1231 w, 1198 w, 1176 m, 1102 s, 1070 w, 1028 s, 998 m, 919 m, 893 w, 834 m, 823 m, 758 s, 743 s, 694 s, 637 w, 558 s, 532 s, 514 s, 494 m, 482 s, 453 w, 436 w cm−1. ESI+ MS: m/z 592 ([M − Cl]+). Anal. calc. for C23H18AuClFeNP (627.6): C 44.01, H 2.89, N 2.23%. Found: C 43.76, H 2.96, N 1.99%.
IR (Nujol): νmax 3128 w, 3082 w, 2223 s (NC), 1311 m, 1242 w, 1198 m, 1178 m, 1173 m, 1105 s, 1070 w, 1054 w, 1036 m, 1030 m, 997 w, 925 m, 841 m, 822 s, 756 s, 747 s, 705 s, 696 s, 635 w, 559 s, 534 s, 514 s, 495 s, 479 s, 470 m cm−1. ESI+ MS: m/z 824 ([M − Cl]+). Anal. calc. for C23H18Au2Cl2FeNP (860.0): C 32.12, H 2.11, N 1.63%. Found: C 32.08, H 2.11, N 1.48%.
1H NMR (acetone-d6): δ 4.40 (vt, J′ = 2.1 Hz, 2 H, fc), 4.74 (d vt, J = 3.1, 1.9 Hz, 2 H, fc), 5.16 (d vt, J = 1.2, 1.9 Hz, 2 H, fc), 5.42 (vt, J′ = 2.1 Hz, 2 H, fc), 7.65–7.71 (m, 4 H, PPh2), 7.72–7.57 (m, 2 H, PPh2), 7.80–7.87 (m, 4 H, PPh2). 31P {1H} NMR (acetone-d6): δ 33.0 (s). IR (Nujol): νmax 3118 w, 3056 w, 2231 s (NC), 1704 s, 1314 w, 1226 m, 1200 w, 1184 m, 1176 m, 1105 s, 1060 w, 1034 m, 999 w, 921 w, 848 m, 834 m, 823 m, 755 s, 749 s, 715 w, 696 m, 660 vs, 553 m, 531 m, 519 s, 493 m, 476 m, 435 w cm−1. ESI+ MS: m/z 592 ([Au(1)]+). Anal. calc. for C23H18AuF6FeNPSb (827.9): C 33.36, H 2.19, N 1.69%. Found: C 33.18, H 2.20, N 1.55%.
1H NMR (CDCl3): δ 4.01 (vt, J′ = 2.0 Hz, 2 H, fc), 4.76 (v dt, J′ = 3.2 Hz, 2.0 Hz, 2 H, fc), 4.97 (v dt, J′ = 1.9 Hz, 1.2 Hz, 2 H, fc), 5.12 (vt, J′ = 2.0 Hz, 2 H, fc), 7.52–7.60 (m, 6 H, PPh2), 7.63–7.70 (m, 4 H, PPh2). 31P{1H} NMR (CDCl3): δ 32.1 (s). 19F NMR (CDCl3): δ −78.6 (s). IR (Nujol): νmax 3113 m, 3056 m, 2233 m (NC), 1351 s, 1227 s, 1193 s, 1134 s, 1104 m, 1056 s, 999 w, 922 w, 828 w, 788 m, 748 m, 694 m, 652 m, 615 m, 600 m, 570 m, 555 w, 530 m, 517 s, 476 m, 435 w cm−1. ESI+ MS: m/z 592 ([Au(1)]+). Anal. calc. for C25H18AuF6FeN2O4PS2 (871.9): C 34.42, H 2.08, N 3.21%. Found: C 34.33, H 2.29, N 3.18%.
The structures were solved by direct methods (SHELXS-97) and refined by a full-matrix least squares procedure based on F2 using SHELXL-97.51 The non-hydrogen atoms were refined with anisotropic thermal motion parameters. The NH hydrogen atoms in the structure of 2 and 5 were located on the difference Fourier maps, and their positions were freely refined with Uiso(H) set to 1.2 Ueq(N). All other hydrogen atoms were included in their calculated positions and refined using the “riding model”.
Selected crystallographic data, data collection and structure refinement parameters are presented in the ESI (Table S1†). All geometric calculations were performed with a recent version of the PLATON program,52 which was also used to prepare the structural diagrams.
Footnote |
† Electronic supplementary information (ESI) available: Selected crystallographic data, additional structural drawings and copies of the NMR spectra. CCDC 1558580–1558590. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7dt02336g |
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