Some unusual reactions of metal carbonyls with (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne

Abstract

The photolytic reaction of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne with iron pentacarbonyl in hexane gives the tellurium coordinated carbonyl vinylallyl dinuclear iron complex 1, tellurium coordinated vinylallyl trinuclear iron complex 2, a lactone fused ferracyclopentadiene complex 3, and a butterfly complex 4. On reaction with PPh₃, 1 undergoes fragmentation to yield a cyclopentadienone (7) and the starting material (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne. In addition, reactions of the tellurium ene-yne ligand with [M(CO)₅(THF)] or [M(CO)₆] give the M(CO)₅ adducts 8–10. All compounds have been characterized by IR, ¹H NMR and ¹³C NMR spectroscopy and structures of 1–4 and 7 have been established by single crystal X-ray diffraction.

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Introduction

In the realm of organotellurium chemistry, (Z)-vinylic tellurides constitute an important class and their usefulness has been recently reviewed.^1,2 (Z)-vinylic tellurides are of synthetic interest since the tellurium moiety is transmetalated by many organometallic reagents to generate vinyl organometallics with total retention of configuration, and which can react further with electrophiles like carbonyl compounds,^3,4 enones⁵ and epoxides.⁶ (Z)-tellurobutenynes are important in synthesizing tellurium free enynes and endiynes, and these have been used in the preparation of several natural products extracted from natural sources. For example, brasilenyne, obtusenyne, cis-dihydrorhodophytin and others were isolated from Laurencia red algae⁷ or from a green variety of the Hawaiian algae Laurencia nidifica.⁸ However, to the best of our knowledge there is no report on the chemistry of metal carbonyls with (Z)-tellurobutenynes.

We have been interested, in recent times, in the use of the ferrocenylacetylene building block with metal carbonyls due to its redox chemistry and general robustness under most reaction conditions. Our work in this area has resulted in the synthesis of several new ferrocenyl containing metal carbonyl cluster compounds.^9–18

Previously, we have also reported that the reaction of an ene-yne system (isopropenyl acetylene) with [Fe(CO)₅] in the presence of CO, yields the products 2,6- and 2,5-divinyl-substituted 1,4-benzoquinone.¹⁹ In continuation of our work in the chemistry of ene-yne and ferrocenyl groups as substituents, our main goal has been to explore the reactivity of the multifunctional organotellurium (tellurium ene-yne) ligand bearing ferrocenyl groups, (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne, with metal carbonyls for the formation and expansion of metallic clusters. This tellurium ene-yne is important as it may interact directly with the metal system through the tellurium lone pair and through the ene-yne π-system. The facile cleavage of the Te–C bond also renders this ligand as a convenient reagent for the formation of new clusters by coordinating within the system. Herein, we report the photolysis and reactions of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne with iron pentacarbonyl and [M(CO)₅(THF)] (M = Cr, Mo, W).

2. Results and discussion

2.1. Photolytic reaction of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne and [Fe(CO)₅]

When a hexane solution containing (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne and [Fe(CO)₅] was photolysed under continuous bubbling of nitrogen at 0 °C for 30 minutes, three new compounds, 1–3, and a butterfly complex 4, were obtained along with known compounds, [Fe(CO)₂{η²:η²-2,5-Fc₂C₄H₂Fe(CO)₃}-μ-CO)] and [Fe(CO)₃(η⁴-C₅H₂OFc₂)]⁹ (Scheme 1). Compounds 1–4 were found to be stable in solution and in the solid state. All compounds were characterized using FT-IR, ¹H and ¹³C NMR spectroscopy, and mass spectrometry. Suitable single crystals of 1–4 were grown from dichloromethane/hexane solvent mixtures and their structures were established crystallographically.

Scheme 1

The IR spectra of compounds 1–4 show characteristic absorptions of terminal carbonyl ligands in the regions of 1943 cm⁻¹ to 2050 cm⁻¹. Compounds 1 and 3 show a band characteristic of a ketonic carbonyl at 1754 cm⁻¹ and 1769 cm⁻¹, respectively, whereas compound 2 shows a band due to a semibridging carbonyl group at 1898 cm⁻¹. ¹H NMR spectra of 1 and 2 show signals at δ 6.86 ppm and δ 5.95 ppm for the allylic protons, respectively, while compound 3 shows a signal at δ 5.95 ppm for a metallacyclic proton. ¹H and ¹³C NMR spectra of compounds 1–4 confirm the presence of Cp rings of ferrocenyl groups. Mass spectra of these compounds show the molecular ion peaks.

The molecular structure of 1, shown in Fig. 1, is essentially an adduct of the starting material with an Fe₂(CO)₆ fragment. As a result of the adduct formation the ene-yne unsaturated system becomes a vinylallyl system coordinated to the Fe₂(CO)₆ unit. The introduction of bubbling CO into the reaction medium does not lead to any increase in the yield of compound 1. The iron atoms, Fe(1) and Fe(2), are unsymmetrically coordinated with tellurium substituted vinylallyl carbonyl ligand bearing ferrocenyl groups, FcTeC(Fc)CC(H)C(Fc)CO, in a η¹:η²:η¹:η³ fashion; giving 8e⁻ as a donor ligand to give a total of 34 e⁻. To satisfy the 18 electron count on each iron atom, the Fe(2) atom coordinates with the η³ allylic carbon atoms (Fe(2)–C(7) = 2.178(4) Å, Fe(2)–C(8) = 2.083(4) Å, Fe(2)–C(9) = 1.984(8) Å), whereas the Fe(1) atom is bound with the CC(Fc)CO portion which formally gives 3 electrons [Fe(1)–C(1) = 1.906(1) Å, Fe(1)–C(9) = 2.012(8) Å, Fe(1)–C(10) = 2.143(8) Å] and is also coordinated with the Te atom along with the Fe(1)–Fe(2) single bond. The Fe(1) and Fe(2) atoms contain two and three terminal carbonyl ligands, respectively. Such a type of coordination mode of five atoms (including hetero atom tellurium) along with carbonyl insertion is, heretofore, unprecedented to the best of our knowledge.

Fig. 1 Molecular structure of 1. Selected bond lengths (Å) and bond angles (deg): Fe(1)–C(2) = 1.776(8), Fe(1)–C(3) = 1.775(5), Fe(1)–Te(1) = 2.585(1), Te(1)–C(31) = 2.107(8), Te(1)–C(7) = 2.139(2), Fe(1)–Fe(2) = 2.690(4), C(1)–C(10) = 1.476(8), C(10)–C(21) = 1.466(5), O(1)–C(1)–Fe(1) = 145.2(9), O(2)–C(2)–Fe(1) = 172.5(5), C(7)–C(1)–Fe(1) = 77.5(1), O(1)–C(1)–C(7) = 136.6(1).

Ferrocenyl groups also show some variation within the complex. The ferrocenyl group attached to Te shows the complete eclipsed confirmation and other ferrocenyl groups show little deviation from the eclipsed confirmation, however, all the Cp ring planes show common Cp–Fe bond distances in the range of 1.64–1.65 Å.

The carbon–carbon bond distances of 1 in the vinylallyl unit (C(7)–C(8) = 1.423(5), C(8)–C(9) = 1.393(1), C(9)–C(10) = 1.384(5), indicate a substantial lengthening of the acetylenic and olefinic bonds of the uncomplex telluroenyne, [(CH₃O)C₆H₄TeC(C₆H₅) =C(H)C≡CC₆H₅], (C≡C distances = 1.214(3) Å, C=C =1.322(6) Å).²⁰ The carbon–carbon bond distances of 1 are similar to the related allyl complexes reported earlier: [Fe₂(CO)₅{S(C₂H₅)C₂(CH₃)C(C₆H₅)₂C(O)}],²¹ [Fe₂(CO)₆{η¹:η³-FcCHC₂C(Fc)(COOMe)}],²² [(C₉H₁₄CO)Fe₂(CO)₆],²³ [Fe₃C(O)₁₀(H₂CC(CH₃)CC(H)CC(H)C(CO)C(CH₃)CH₂],²⁴ [Fe₂(CO)₆{μ-C(CNBu^t)C(CF₃)SMe}],²⁵ [Fe₂(CO)₆{μ-η²:η³-C(O)C(H)C(S)CH₃}]²⁶ and the C4-chain adopts a zigzag configuration with bond angles of 114.1° (bond angle between C(7)–C(8)–C(9)) and 145.3° (bond angle between C(8)–C(9)–C(10)).

As shown in Fig. 2, the molecular structure of 2 consists of three iron atoms which form a scalene triangle [Fe(1)–Fe(2) = 2.526(1) Å, Fe(2)–Fe(3) = 2.671(8) Å, Fe(1)–Fe(3) = 2.876(1) Å] and is attached to tellurium substituted vinylallyl ligand bearing ferrocenyl groups in a η¹:η²:η³:η¹- fashion; giving 8e⁻ to reach the required 48 electron count of the EAN rule. Because of the unsymmetry of the iron triangle the Fe–Fe bond angles range from 54° to 67.1°. The carbon–carbon bond distances (C(9)–C(10) = 1.363(2) Å and C(10)–C(11) = 1.393(6) Å) of 2 are within the range of an allylic bond, as found in [Fe₃(CO)₈{η⁴-(CHCHCH₃)(CH₂CHCH₂)(NEt₂)₂}],²⁷ [Fe₃(CO)₆{μ₃-η⁴-(EtC₂CCH₃(=CH₂))}],²⁸ [Fe₃(CO)₉{μ₃-η³-C(OC₂H₅)CCHC(O)CH₃}],²⁹ [Et₄N][(μ₃-Te)Fe₃(CO)₉{μ₃-η¹:η¹:η³-C(O)C(H)CCH₂}]³⁰ and [Et₄N][(μ₃-Se)Fe₃(CO)₉{μ₃-η¹:η¹:η³-C(O)C(H)CCH₂}].³¹ The C4-chain also adopts a zigzag configuration in the complex 2 with bond angles of 115° (bond angle between C(10)–C(11)–C(12)) and 146.1° (bond angle between C(9)–C(10)–C(11)).

Fig. 2 Molecular structure of 2. Selected bond lengths (Å) and bond angles (deg): Fe(1)–C(9) = 1.914(1), Fe(2)–C(9) = 2.231(7), Fe(2)–C(10) = 1.939(8), Fe(3)–C(10) = 2.068(7), Fe(3)–C(11) = 2.109(2), Fe(3)–C(12) = 2.254(2), Fe(2)–Te(1) = 2.505(2), C(9)–C(13) = 1.463(4), C(11)–C(12) = 1.426(7), O(1)–C(1)–Fe(1) = 176.3(8), O(2)–C(2)–Fe(1) = 178.3(8), O(3)–C(3)–Fe(1) = 176.7(9), O(4)–C(4)–Fe(2) = 177.9(5), O(5)–C(5)–Fe(2) = 178.2(4), O(7)–C(7)–Fe(3) = 169.9(9), O(8)–C(8)–Fe(3) = 176.3(3).

Compound 2 shows a C(6)–O(6) semibridging carbonyl since Fe(1)–C(6) = 2.792(4) Å, Fe(3)–C(6) = 1.808(9) Å, and Fe(3)–C(6)–O(6) = 167.2°. This peculiar CO group is identified in the IR spectrum by a characteristic absorption band at 1898 cm⁻¹.

All the ferrocenyl groups show an almost complete eclipsed confirmation with an average Fe–Cp plane distance of 1.64 Å and ferrocenyl C–C bond distances are within the normal range of 1.33–1.44 Å.

As shown in Fig. 3, the molecular structure of 3 comprises of a lactone ring fused with a ferracyclopentadiene ring, formed by carbon atoms of the ene-yne chain and atoms of the two inserted CO. The ferracyclopentadiene ring is η⁴-bonded to Fe(CO)₂, which in turn is attached to the ring Fe through a direct Fe–Fe bond (Fe(1)–Fe(2) = 2.557(3) Å). The ferracyclopentadiene ring is in an eclipsed conformation which is fairly uncommon compared to the common staggered conformation, found in most of the complexes.³² Position 5 of the ferracyclopentadiene ring is occupied by the ferrocenyl group, whereas positions 2 and 3 are used in a five membered-lactone ring formation. One of the carbon atoms of the lactone ring, present adjacent to position 3 of the ferracyclopentadiene unit, is substituted by the ferrocenyl group and is coordinated with another Fe(CO)₃ unit, which in turn is attached to the diene bonded Fe(CO)₂ unit through a direct Fe–Fe bond (Fe(2)–Fe(3) = 2.753(8) Å). The Fe(2) and Fe(3) atoms are also bonded to the FcTe unit, which is cleaved from the tellurium ene-yne chain. The ferrocenyl units of the ene-yne chain are opposite to the tellurium attached ferrocenyl group and Fe(2) and Fe(3) metal carbonyl fragment. The Fe(1) fragment is within the plane of the butadiene unit. The distances of the C₄Fe ring compare well with the related metallacyclopentadiene complexes reported earlier: [Fe(CO)₃{η⁴-(CO)₃FeC₄H₄}],³³ [Fe(CO)₃{η⁴- (CO)₃FeC₄(OSiMe₃)₄}],³⁴ [Fe(CO)₂{η²:η²- 2,5-(CO)₃FeC₄H₂Fc₂}-μ-CO],⁹ [Fe(CO)₂{η²:η²-PhC≡CCC(Fc)C(C≡CPh)C(Fc) (CO)₃Fe}-μ-CO].³⁵

Fig. 3 Molecular structure of 3. Selected bond lengths (Å) and bond angles (deg): Fe(1)–C(11) = 2.000(5), Fe(1)–C(2) = 1.901(4), Fe(2)–C(2) = 2.131(5), Fe(2)–C(11) = 2.167(7), Fe(2)–C(12) = 2.110(8), Fe(2)–C(13) = 2.136(1), Fe(3)–C(14) = 2.171(6), Fe(2)–Te(1) = 2.532(9), Fe(3)–Te(1) = 2.552(9), C(11)–C(12) = 1.422(2), C(12)–C(13) = 1.411(1), C(13)–C(14) = 1.454(9), C(14)–C(1) = 1.486(2), C(13)–C(2) = 1.419(1), C(1)–O(1) = 1.204(3), C(2)–O(2) = 1.390(6), C(1)–O(2) = 1.417(0), O(4)–C(4)–Fe(1) = 174.2(6), O(5)–C(5)–Fe(1) = 178.1(9), O(6)–C(6)–Fe(2) = 174.0(2), O(7)–C(7)–Fe(2) = 171.3(5), O(8)–C(8)–Fe(3) = 175.2(5), O(9)–C(9)–Fe(3) = 178.2(6), O(10)–C(10)–Fe(3) = 174.2(3).

The molecular structure of 4 (Fig. 4) shows a butterfly Fe₂Te₂ core with the wing tips of the Te atoms bonded to two ferrocenyl groups in the axial and equatorial positions which is the preferred orientation of the C₃ ligand causing minimum steric repulsion and effective crystal packing. The ferrocenyl groups are also in an eclipsed confirmation with an average Fe–C bond length of 2.040 Å and average Cp–Fe bond length of 1.64 Å.

Fig. 4 Molecular structure of 4. Selected bond lengths (Å) and bond angles (deg): Fe(1)–Fe(2) = 2.637(3), Fe1–Te1 = 2.537(1), Fe(1)–Te(2) = 2.547(4), Fe(2)–Te(1) = 2.536(4), Fe(2)–Te(2) = 2.549(6), Te(1)–Fe(1)–Te(2) = 83.6(5), Te(1)–Fe(2)-Te(2) = 83.6(1), Fe(1)–Te(2)–Fe(2) = 62.3(2), Fe(2)–Te(1)–Fe(1) = 62.6(4), O(1)–C(1)–Fe(1) = 175.5(5), O(2)–C(2)–Fe(1) = 176.6(6), O(3)–C(3)–Fe(1) = 177.7(7), O(4)–C(4)–Fe(2) = 176.6(5), O(5)–C(5)–Fe(2) = 178.6(5), O(6)–C(6)–Fe(2) = 177.8(6).

The average Fe–Te and Fe–Fe distances of compound 4, 2.542 Å and 2.637 Å, respectively, are in good agreement with similar butterfly complexes reported earlier: [Fe₂(CO)₆(μ-TeMe)₂] [Te–Fe = 2.549 Å, Fe–Fe = 2.634 Å],³⁶ [Fe₂(CO)₆(μ-TeCH(CH₃)Te)₂] [Te–Fe = 2.533 Å, Fe–Fe = 2.606 Å],³⁷ [Fe₂(CO)₆(μ-CH₃Te)]₂(μ-Te(CH₂)₂Te-μ] [Te–Fe = 2.553 Å, Fe–Fe = 2.613 Å],³⁸ [Fe₂(CO)₆ (μ-TeCH₂CH₂Te)] [Te–Fe = 2.524 Å, Fe–Fe = 2.626 Å],³⁹ [Fe₂(CO)₆(μ-TeCH = C=CH₂)₂] [Te–Fe = 2.540 Å, Fe–Fe = 2.620 Å],³⁰ [Fe₂(CO)₆(μ-TeCHCl₂)₂] [Te–Fe = 2.530 Å, Fe–Fe = 2.656 Å].⁴⁰

2.2. Reaction of complex 1 with triphenylphosphine (PPh₃)

To further explore the reactivity of complex 1, we performed the reaction of 1 with triphenylphosphine (Scheme 2).

When 1 was treated with an excess of triphenylphosphine in refluxing toluene under continuous bubbling of nitrogen, the PPh₃ substituted complex 7, [Fe(CO)₂(PPh₃){η⁴-C₅H₂OFc₂}] was obtained with a small amount of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne. Compound 7 was characterized using FT-IR, ¹H NMR and ³¹P NMR spectroscopy, and mass spectrometry. The structure of complex 7 (Fig. 5) was established by crystallography.

Fig. 5 Molecular structure of 7. Selected bond lengths (Å) and bond angles (deg): Fe(1)–C(4) = 2.195(3), Fe(1)–C(5) = 2.078(9), Fe(1)–C(6) = 2.547(4), Fe(1)–C(7) = 2.055(7), Fe(1)–P(1) = 2.243(5), C(3)–O(3) = 1.237(1), O(1)–C(1)–Fe(1) = 176.2(9), O(2)–C(2)–Fe(1) = 175(8).

The IR spectrum of compound 7 shows the presence of only terminal carbonyls. The ¹H NMR spectrum confirms the presence of ferrocenyl and phenyl groups. The mass spectrum of compound 7 shows a molecular ion peak. ³¹P confirms the presence of a phosphorus atom. The X-ray crystal structure of 7 shows that it comprises of an Fe(CO)₂(PPh₃) unit coordinated to an η⁴-(2,5-diferrocenyl) cyclopentadieneone which may be a substituted product of [Fe(CO)₃{η⁴-C₅H₂OFc₂}].⁹ In complex 7, the ferrocenyl groups attached to the ring are “syn”, opposite the Fe(CO)₂(PPh₃) unit. As was previously observed in a related substituted PPh₃ cyclopentadieneone complex, [dicarbonyl(triphenylphosphine) (2,4-diphenylbicyclo-[3.3.0]octa-1,4-dien-3-one) iron]⁴¹ and other cyclopentadieneone complexes reported earlier,^9,32 the cyclopentadiene is not planar, and the =CO unit is out of plane with an angle of ∼12°, indicating the anti-aromatic character of cyclopentadieneone. The overall mechanism from 1 to 7 can be shown as in Scheme 2.

Scheme 2

As part of our recent studies in the demetalation of iron carbonyl fragments from complexes by molecular iodine to prepare organic compounds,⁴² the demetalation of complexes 5 and 7 did not occur perhaps because of the stability of these complexes.

2.3. Reactions of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne with [M(CO)₅THF] (M = Cr, Mo, W)

A solution of [M(CO)₅(THF)] (M = Cr, Mo, W) was prepared by the photo-irradiation of [M(CO)₆] in THF. The interaction between (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne and [M(CO)₅(THF)] solution at room temperature produced the dark red complexes [M(CO)₅((Fc)TeC(Fc)=C(H)C≡CFc)] 8 (M = Cr), 9 (M = Mo) and 10 (M = W) (Scheme 3). Complexes 8–10 could also be prepared by the direct photolysis of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne and [M(CO)₆] at 0 °C. Compounds 8–10 were found to be stable in the solid state for a few hours.

Scheme 3

All compounds were confirmed by using FT-IR, ¹H, ¹³C and ¹²⁵Te-NMR spectroscopy, mass spectrometry and elemental analysis.

The IR spectra of complexes 8–10 exhibit three absorption bands of appropriate intensity for the M(CO)₅ fragment of the C_4v symmetry ranging from 1925–2070 cm⁻¹ and the presence of an absorption band at 2188–2192 cm⁻¹ confirms the presence of a C≡C bond. ¹H and ¹³C NMR spectra confirm the presence of a ferrocenyl group.

The ¹²⁵Te chemical shift of complexes 8–10 confirms the involvement of the Te atom in coordination and is in a similar pattern to that found in group 6 metal carbonyl complexes which generally decrease in the sequence Cr > Mo > W for the same ligand.^43,44 The ¹²⁵Te NMR chemical shift of complexes 8–10 decreases from 647.9 ppm for 8 [Cr(CO)₅((Fc)TeC(Fc) =C(H)C≡CFc)], to 523.2 ppm for 9 [Mo(CO)₅((Fc)TeC(Fc)=C(H)C≡CFc)], to 488.5 ppm for 10 [W(CO)₅((Fc)TeC(Fc)=C(H)C≡CFc)]. The ¹²⁵Te NMR chemical shift of the free ligand [FcTeC(Fc)=C(H)C≡CFc] is 476 ppm.

The mass spectra show a molecular ion peak of complexes 8–10. The results of elemental analysis are in good agreement with the experimental values for complexes 8–10.

3. Conclusion

In conclusion, we have investigated the reaction of a multifunctional tellurium ene-yne ligand and metal carbonyls, showing different coordination modes. The reaction of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne and [Fe(CO)₅] gives complexes 1–4 in which compounds 1 and 2 are directly interacted with the metal system through the tellurium lone pair and ene-yne π-system, while compounds 3 and 4 are formed by the ready cleavage of the Te–C bond that accompanies coordination within the system. The formation of the PPh₃ substituted product is also obtained by C–C cleavage of the ligand which is stabilised by the PPh₃ substituted iron carbonyl fragment. The coordination involving only tellurium is also shown by this ligand when it is treated with [M(CO)₅(THF)], or irradiation with [M(CO)₆] in hexane.

4. Experimental details

4.1. General procedures

All reactions and manipulations were performed using standard Schlenk line techniques under an inert atmosphere of pre-purified argon or nitrogen. Solvents were purified, dried, and distilled under an argon atmosphere prior to use. Infrared spectra were recorded on a Perkin Elmer FTIR spectrometer. NMR spectra were recorded on a Bruker AVANCE III/400 spectrometer with TMS and Ph₂Te₂ as internal standards. Iron pentacarbonyl was purchased from Fluka and was used without further purification. Photochemical reactions were carried out in a water cooled double-walled quartz vessel with a 125 W mercury lamp manufactured by SAIC, India. TLC plates were purchased from Merck (20 × 20 cm silica gel 60 F₂₅₄. [FcTeC(Fc)=C(H)C≡CFc] was prepared following reported procedures.^45–47

4.2. Photolysis of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne with [Fe(CO)₅]

To a solution of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne (92 mg, 0.125 mmol) in hexane (70 mL), [Fe(CO)₅] (0.5 ml, 3.65 mmol) was added and the solution was photolysed at 0 °C for 30 minutes under a nitrogen atmosphere. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates by using a 30 : 70 v/v dichloromethane/hexane solvent mixture as eluent, which afforded 7 mg of unreacted (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne along with compounds, 1 (22 mg, 16% yield), 2 (10 mg, 7%), 3 (12 mg, 8% yield) and 4 (20 mg, 18% yield).

4.3. Reaction of [Fe₂(CO)₅{η¹:η²:η¹:η³- FcTeC(Fc)=C(H)C=C(Fc)C(O)}] with PPh₃

To a solution of [Fe₂(CO)₅{η¹:η²:η¹:η³-FcTeC(Fc)=C(H)C=C(Fc)C(O)}], 1 (22 mg, 0.020 mmol), in toluene (20 mL), triphenylphosphine, (PPh₃) (14 mg, 0.054 mmol) was added and the mixture was refluxed at 110–120 °C for 2–3 h under a nitrogen atmosphere. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates by using a 50 : 50 v/v dichlromethane/hexane solvent mixture as eluent, giving compound 7 in an 18% (3 mg) yield.

4.4. Reactions of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne with [M(CO)₅(THF)] (M = Cr, Mo, W)

A solution of [M(CO)₅(THF)] was prepared by the irradiation of [M(CO)₆] in THF. After addition of (Z)-1-ferrocenyltelluro-1-ferrocenyl-4-ferrocenyl-1-buten-3-yne, [Fc₃TeC₄], the solution turned from red to deep red coordinated complexes (1 : 1 ratio ligand (91.33 mg, 0.125 mmol) : [M(CO)₆] (0.125 mmol), 8 (M = Cr, 27.5 mg), 9 (M = Mo, 33 mg) and 10 (M = W, 44 mg) (Scheme 3). After stirring at room temperature for 2 hours, the solvent was removed by evaporation under reduced pressure. The residue was subjected to a chromatographic workup on silica gel TLC plates by using a 30 : 70 v/v dichlromethane/hexane solvent mixture as eluent, which afforded compounds, 8, 9 and 10 in 37% (43 mg), 29% (35 mg) and 32% (42 mg) yields, respectively.

4.5. Spectroscopy of compounds 1–4 and 7–10

1: IR (υCO), cm⁻¹ 2042 (m), 1988 (vs), 1943 (s), 1754 (m); ¹H-NMR (δ, CDCl₃): 6.86 (s, FcTeC(Fc)CH), 3.89–4.45 (m, 27H, η⁵-C₅H₅, η⁵-C₅H ₄); ¹³C{¹H}-NMR (δ, CDCl₃): 68.35–72.19 (η⁵-C₅H₅, η⁵-C₅H₄), 66.21, 74.84 (C(Fc)CC(H) C(Fc)COFe), 78.87, 88.50 (CC(Fc)COFe), 209–216, (Fe–CO), 229 (Fe(CO)C); ¹²⁵Te{¹H}-NMR (δ, CDCl₃): 755.3; anal. calcd (%): C, 44.91, H, 2.76. Found (%): C, 45.57, H, 2.45; MS (m/z, ES⁺): 1097.

2: IR (υCO), cm⁻¹ 2044 (m), 2000 (vs), 1979 (s), 1898 (m); ¹H-NMR (δ, CDCl₃): 5.95 (s, FcTeC(Fc)CH), 3.86–4.41 (m, 27H, η⁵-C₅H₅, η⁵-C₅H₄); ¹³C{¹H}-NMR (δ, CDCl₃): 67.27–70.64 (η⁵-C₅H₅, η⁵-C₅H₄), 78.87, 88.50 (C(Fc)CC(H) C(Fc)COFe), 78.87, 88.50 (CC(Fc)COFe), 209–216, (Fe–CO), 229 (Fe(CO)C); ¹²⁵Te{¹H}-NMR (δ, CDCl₃): 820.1; anal. calcd (%): C, 42.85, H, 2.26. Found (%): C, 43.22, H, 2.11; MS (m/z, ES⁺): 1205.

3: IR (υCO), cm⁻¹ 2065 (w), 2044 (s), 2000 (s), 1982 (w); ¹H-NMR (δ, CDCl₃): 5.52 (s, Fe=C(Fc)CH), 4.41-4.42 (m, 27H, η⁵-C₅H₅, η⁵-C₅H ₄); MS (m/z, ES⁺): 2359.

4: IR (υCO), cm⁻¹ 2048 (w), 2008 (vs), 1974 (s); ¹H-NMR (δ, CDCl₃): 3.70–4.38 (m, 18H, η⁵-C₅H₅, η⁵-C₅H₄), ¹³C{¹H}-NMR (δ, CDCl₃): 70.26–75.72 (η⁵-C₅H₅, η⁵-C₅H₄), 211.51–211.58 (Fe–CO); ¹²⁵Te{¹H}-NMR (δ, CDCl₃): 426.6; anal. calcd (%): C, 34.50, H, 2.00. Found (%): C, 34.04, H, 1.91; MS (m/z, ES⁺): 906.

7: IR (υCO), cm⁻¹ 1998 (s), 1950 (s); ¹H-NMR (δ, CDCl₃): 3.70–4.38 (m, 18H, η⁵-C₅H₅, η⁵-C₅H₄); ³¹P{¹H}-NMR (δ, CDCl₃): 29.4; MS (m/z, ES⁺): 821.

8: IR (υCO), cm⁻¹ 2054 (m), 1978 (w), 1925 (vs); ¹H-NMR (δ, CDCl₃): 6.58 (s, FcTe(Cr(CO)₅)C(Fc)CH), 3.98–4.58 (m, 27H, η⁵-C₅H₅,η⁵-C₅H ₄); ¹³C{¹H}-NMR (δ, CDCl₃): 68.64-72.81 (η⁵-C₅H₅, η⁵-C₅H₄), 84.17, 97.67 (FcTe(Cr(CO)₅C(Fc)C(H)CCFc), 117.35131.33 (FcTe(Cr(CO)₅C(Fc)C(H)CCFc)), 216.94–222.72 (Cr–CO); ¹²⁵Te{¹H}-NMR (δ, CDCl₃): 647.9; anal. calcd (%): C, 50.71, H, 3.05. Found (%): C, 49.34, H, 3.09; MS (m/z, ES⁺): 924.

9: IR (υCO), cm⁻¹ 2070 (m), 1988 (w), 1939 (vs); ¹H-NMR (δ, CDCl₃): 6.55 (s, FcTe(Mo(CO)₅)C(Fc)CH), 3.70–4.61 (m, 27H, η⁵-C₅H₅,η⁵-C₅H ₄); ¹³C{¹H}-NMR (δ, CDCl₃): 68.64–72.81 (η⁵-C₅H₅, η⁵-C₅H₄), 84.92, 97.80 (FcTe(Mo(CO)₅C(Fc)C(H)CCFc)), 116.55131.82 (FcTe(Mo(CO)₅C(Fc)C(H)CCFc)), 201.48–205.76 (Mo–CO); ¹²⁵Te{¹H}-NMR (δ, CDCl₃): 523.2; anal. calcd (%): C, 48.40, H, 2.92. Found (%): C, 49.52, H, 2.76; MS (m/z, ES⁺): 969.

10: IR (υCO), cm⁻¹ 2068 (m), 1982 (w), 1930 (vs); ¹H-NMR (δ, CDCl₃): 6.54 (s, FcTe(W(CO)₅)C(Fc)CH), 3.70–4.60 (m, 27H, η⁵-C₅H₅,η⁵-C₅H ₄); ¹³C{¹H}-NMR (δ, CDCl₃): 68.64–72.81 (η⁵-C₅H₅, η⁵-C₅H₄), 84.92, 97.80 (FcTeW(CO)₅C(Fc)C(H)CCFc), 116.55, 131.82 (FcTe(W(CO)₅C(Fc)C(H)CCFc)), 196.48–198.76 (W–CO); ¹²⁵Te{¹H}-NMR (δ, CDCl₃): 488.5; anal. calcd (%): C, 44.37, H, 2.67. Found (%): 44.93, H, 2.39; MS (m/z, ES⁺): 1056.

4.6. Crystal structure determination of 1–4 and 7

Relevant crystallographic data and details of measurements are given in Table 1. Suitable X-ray quality crystals of compounds 1–4 and 7 were grown by the slow evaporation of n-hexane and dichloromethane. An Oxford Diffraction X caliber-S/SUPERNOVA diffractometer was used for the cell determination and intensity data collection. Monochromatic Mo Kα radiation (0.71359 Å) was used for the measurements. Absorption corrections using multi φ scans were applied. The structures were solved by direct methods (SHELXS) and refined by full-matrix least squares against F_o² using SHELXL-97 software.⁴⁸ Non-hydrogen atoms were refined with anisotropic thermal parameters. All hydrogen atoms were geometrically fixed and allowed to refine using a riding model. The crystallographic details are summarized in Table 1.

Table 1 Crystal data and structure refinement for compounds 1–4 and 7

Compound	(1) CH2Cl2	(2) CH2Cl2	3	4	7
Empirical form	C40H28Fe5O6Te	C42H25Fe6O8Te	C88H56Fe12O20Te2	C26H18Fe4O6Te2	C45H33Fe3O3P
Formula wt	1096.40	1205.25	2358.73	905.00	820.23
Crystal system	Monoclinic	Triclinic	Monoclinic	Triclinic	Monoclinic
Space group	P 21/n	P 1̄	P 21/c	P 1̄	P 21/n
a, Å	12.28110(10)	12.2394 (4)	22.3039 (3)	7.7353 (5)	15.4026 (4)
b, Å	16.53880 (10	13.0672 (5	22.5704 (3)	13.4490 (11)	11.2473 (3)
c, Å	19.07710 (10)	14.1262 (6)	16.4850 (2)	13.933 (2)	22.2283 (5)
α, deg.	90	97.954 (3)	90	75.851 (9)	90
β, deg.	89.8220 (10)	97.076 (3)	102.9210 (10)	80.947 (9)	108.394 (2)
ϒ, deg.	90	97.639 (3)	90	80.713 (7)	90
Volume, A^3	3874.82 (4)	2194.49 (14)	8088.55	1376.6 (3)	3654.04 (16)
Z, Dcalcd, mg m^−3	4, 1.879	2, 1.824	4, 1.937	2, 2.183	4, 1.491
Abs. coeff., mm^−1	2.751	2.755	2.863	4.182	1.261
F(000)	2160	1182	4640	860	1680
Crystal size, mm	0.28 × 0.23 × 0.18	0.34 × 0.28 × 0.24	0.32 × 0.29 × 0.27	0.31 × 0.26 × 0.21	0.35 × 0.32 × 0.29
θ range, deg	2.97 to 25.00	3.12 to 25.00	2.94 to 25.00	2.94 to 25.00	3.21 to 25.00
Index ranges	14 ≤ h ≤ 14, −18 ≤ k≤ 19, −21 ≤ l ≤ 22	−14 ≤ h ≤ 14, −14 ≤ k≤ 15, −16 ≤ l ≤ 12	−26 ≤ h ≤ 26, −26 ≤ k≤ 26, −19 ≤ l ≤ 19	−8≤ h≤ 9, −14 ≤ k≤ 15, −16 ≤ l ≤ 16	−18 ≤ h ≤ 18, −13 ≤ k≤ 13, −24 ≤ l≤ 26
Reflections collected per unique	34571/6805 [R(int) = 0.0311	17319/7724 [R(int) = 0.0490	69043/14222 [R(int) = 0.0577	9602/4836 [R(int) = 0.0432	28099/6439 [R(int) = 0.0427
Data/restraints/parameters	6805/0/496	7724/0/526	14222/0/1099	836/0/343	6439/0/469
Goodness of fit on F^2	1.054	1.101	1.033	1.054	1.068
Final R indices [l > 2σ(I)	R1 = 0.0216, wR2 = 0.491	R1 = 0.0629, wR2 = 0.1748	R1 = 0.0323, R2 = 0.0605	R1 = 0.0371, wR2 = 0.0945	R1 = 0.0453, wR2 = 0.1133
R indices (all data	R1 = 0.0266, wR2 = 0.0515	R1 = 0.0708, wR2 = 0.1828	R1 = 0.0518, wR2 = 0.0678	R1 = 0.0404, wR2 = 0.0980	R1 = 0.0619, wR2 = 0.1263
Largest diff. peak and hole, e A^−3	0.455 and −0.466	1.834 and −1.126	0.815 and −0.642	1.541 and −1.258	0.676 and −0.266

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Acknowledgements

P.M. is grateful to the Department of Science and Technology, Government of India for support. M.T. and R.S.J. are grateful to UGC and CSIR, Government of India for research fellowships.

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Footnote

† CCDC 963172, 903097, 963171, 963170 and 963173. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c3ra45580g

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