Hydrosilylation of Ferrocenylalkyne−Dicobalthexacarbonyl Complexes

ARTICLE pubs.acs.org/Organometallics

Hydrosilylation of Ferrocenylalkyne-Dicobalthexacarbonyl Complexes. Model Reactions for the Synthesis of Organometallic Dendrimers  ngel Nievas,† Jorge J. Gonzalez,† Elisa Hernandez,† Esther Delgado,*,† Avelino Martín,‡ Carmen A M. Casado,† and Beatriz Alonso*,† † ‡

Departamento de Química Inorganica, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco 28049-Madrid, Spain Departamento de Química Inorganica, Edificio de Farmacia, Universidad de Alcala de Henares, 28871-Madrid, Spain

bS Supporting Information







ABSTRACT: Regio- and stereoselective hydrosilylation reactions of ferrocenylalkyne-dicobalthexacarbonyl complexes with HSiEt3 or dendrimer Si[CH2CH2CH2Si(CH3)2H]4 have afforded the ferrocenylvinylsilanes [FcC(SiEt3)dCH2] (1), [FcCtCC(SiEt3)dC(H)R] [R = Fc (E-4), H (13), SiMe3 (Z-15)], and [(E)FcC(H)dC(SiEt3)CtCSiMe3] (14) and the ferrocenylvinyl-functionalized carbosilane dendrimers Si[CH2CH2CH2Si(CH3)2C(Fc)dCH2]4 (3) and (Z)-Si[CH2CH2 CH2Si(CH3)2C{CtCFc}dC(H)Fc]4 (6). Characterization of all compounds by 1H, 13 C{1H}, and 29Si{1H} NMR and IR spectroscopy, as well as mass spectrometry, supports their assigned structures. The molecular structures of compounds [{Co3(CO)9}(μ3-CCH2Fc)] (2), [ C(O)C(Fc)dC(SiEt3) CdC(H)Fc] (5), [{Co2 (CO)6}(μ,η2-FcCtCCCH)] (8), and [{Co2(CO)6}2(μ,η2,η2-FcCCCCSiMe3)] (9) have been determined by single-crystal X-ray diffraction. The redox activity of the model diferrocenylalkynyl complex 4 and the corresponding octaferrocenyl dendrimer 6 has been examined by cyclic voltammetry.

’ INTRODUCTION Addition of HX (X = SR, OR, SiR3, or BR2) across carboncarbon multiple bonds promotes the formation of new C-X bonds. This fact has allowed us to recently prepare the multifunctional ligands [(Z)-FcCtCSC(H)dC(H)(OMe)], [(Z)-FcCtCSC(H)dC(H)(OEt)], [(Z)-FcCtCSC(H)dC(H)SPh], [(Z)FcCtCSC(H)dC(H)SC6F5], and [(Z,Z)-Fc(SR)CC(H)SC(H)dC(H)SR] [R = Ph, C6F5] by hydroalkoxylation and hydrothiolation of the thioether FcCtCSCtCH.1 On the other hand, due to the increasing interest in the ferrocenyl carbosilane dendrimers as molecules with possibilities as functional materials with promising electrochemical, catalytic, photo-optical, and magnetic properties, in the last years we have been interested in finding new synthetic routes to prepare this type of compound.2-7 Thus, we have recently described the preparation of new dendrimers containing ferrocenyl acetylide terminal groups coordinated to the cluster Os3(CO)10.8 Hydrosilylation of alkynes whose regio- and stereoselectivity depend on the reaction conditions affords vinylsilanes, which are not only very useful intermediates in organic synthesis9-15 but also functional groups widely used in different synthetic strategies toward dendrimers.16-20 In this field, we have previously r 2011 American Chemical Society

reported several families of organometallic carbosilane dendritic macromolecules obtained by hydrosilylation reactions.2-7,21,22 As an extension of our previous studies on this subject, we have tried to find model reactions with a double goal: initially, to prepare dendrimers with ferrocenylalkyne or alkene functionalities using as precursors alkynes coordinated to one Co2(CO)6 fragment and, second, to synthesize new heteronuclear dendrimers containing ferrocenylcobalt alkyne groups in the periphery. Cobaltcarbonyl compounds are among the transition metal complexes that favor hydrosilylation, and although it is known that the Co2(CO)6 fragment may act as a protecting group of the CtC bond, decomplexation of the alkynes may also generate vinylsilanes in the presence of HSiR3.23 Herein we wish to report the synthesis of new organometallic vinylsilanes including some carbosilane dendrimers obtained by hydrosilylation reactions of ferrocenylalkyne-dicobalthexacarbonyl complexes.

Received: December 21, 2010 Published: March 09, 2011 1920

dx.doi.org/10.1021/om1011903 | Organometallics 2011, 30, 1920–1929

Organometallics

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Scheme 1. Synthesis of Compounds 1-6

’ RESULTS AND DISCUSSION Unsuccessful results have been obtained from the reaction between the compound [{Co2(CO)6}(μ,η2-FcCCSiMe3)] and HSiEt3. Thinking that steric reasons might be responsible for this failure, we carried out an analogous reaction using the cobaltcarbonyl complex containing the terminal acetylene ligand FcCtCH. Thus, a mixture of [{Co2(CO)6}(μ,η2-FcCCH)] and HSiEt3 was stirred in dry 1,2-dichloroethane in the absence of light at 50 °C for 4 h. After a TLC purification, the formation of the R-isomer [FcC(SiEt3)dCH2] (1) in a 63% yield was confirmed by 1H and 13C NMR spectroscopy and mass spectrometry (Scheme 1). The presence in its 1H NMR spectrum of two doublet resonances at 6.21 and 5.50 ppm with a coupling constant value of 3.9 Hz indicates that a Markovnikov addition has taken place. It had been previously reported24 that the R-isomer [FcC(SiEt3) dCH2] (1) together with the β-isomer [FcC(H)dC(SiEt3)H] had been obtained in a 20:80 ratio, respectively, by a hydrosilylation reaction of FcCtCH in the presence of Speier's catalyst, but only 1H NMR characterization had been described. Contrarily, the isolation of only one isomer following the method here described confirms the regioselectivity of the reaction. Additionally, a second product that results from the reaction between [{Co2(CO)6}(μ,η2-FcCCH)] and HSiEt3 in a 5% yield was proposed to be the alkylidyne-capped compound [{Co3 (CO)9}(μ3-CCH2Fc)] (2) (Scheme 1) on the basis of its microanalysis as well as the IR and 1H and 13C{1H} NMR spectroscopic data. In addition, the molecular ion (m/z 639) and peaks corresponding to the successive loss of nine carbonyls were observed in its FABþ mass spectrum. The IR spectrum in the carbonyl region shows a pattern similar to that observed in analogous compounds,25 and also a characteristic resonance of the μ3-alkylidyne ligand appears at 304 ppm in the 13C{1H}

Figure 1. ORTEP view of compound 2 (thermal ellipsoids at the 50% probability level). Ferrocenyl hydrogen atoms were omitted for clarity. Selected bond distances (Å) and angles (deg): C(1)-C(2) 1.500(3), C(1)-Co(1) 1.903(3), C(1)-Co(2) 1.897(2), Co(1)-Co(2) 2.463(1), Co(2)-Co(20 ) 2.477(1), Co(20 )-Co(1)-Co(2) 60.4(1). Symmetry transformations used to generate equivalent atoms: x, -yþ1/2, z.

NMR spectrum. Although many alkylidyne tricobaltnonacarbonyl derivatives have been prepared by reactions of Co2(CO)8 and RCX3 (R = organic group, X = halogen),26 their formation from thermal treatment of terminal acetylenic cobalt compounds [{Co2(CO)6}(μ,η2-RCtCH)] is also known.27 In order to know if the presence of water in the solvent might favor the formation of compound 2, we carried out the same reaction using wet 1,2-dichloroethane. In this case, an increase of the yield of compound 2 was observed (12%), while that corresponding to 1 1921

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Organometallics

Scheme 2. Proposed Mechanism for the Formation of 5













olephinic carbon and the silicon atom of the SiEt3 group seems to indicate that the E-isomer has been prepared (see Supporting Information). The cyclobutenone [C(O)C(Fc)dC(SiEt3) CdC(H)Fc] (5) was also obtained from this reaction in a 10% yield (Scheme 1). Cyclization reactions can be promoted by transition metal complexes,35,36 and among them, the carbenes [(CO)5M dC(Fc)OMe] (M = Cr, Mo, W) react with PhCtCPh to yield




the cyclobutenone [FcC(OMe)C(O)C(Ph)d C(Ph)],37 while [(CO)5ModC(C3H5)OMe] reacts with FcCtCR (R = Me,


was reduced (47%). Some cobalt clusters containing alkylidyne ligands have shown catalytic activity in organic synthesis.28,29 Thus, it has been recently reported that the cluster [{Co3(CO)9}(μ3-CH)] catalyzes the Pauson-Khand reaction between the PhCtCH and norbonene30,31 as well as the cyclotrimerization of alkynes.32 The molecular structure of compound [{Co3 (CO)9 } (μ3-CCH2Fc)] (2) was determined by a single-crystal X-ray analysis, and it is shown in Figure 1. Selected bond lengths and angles are collected in the figure caption. Compound 2 is made up of a triangular arrangement of cobalt atoms capped by the alkylidyne ligand μ3-CCH2Fc with very similar cobalt-cobalt distances [2.463(1) and 2.477(1) Å]. The Co-C (carbyne atom) lengths [mean 1.899(3) Å] compare well with analogous alkylidyne cobalt trinuclear cluster.25,33,34 Each cobalt atom carries two equatorial and one axial carbonyl ligand, and the Co-C (carbonyl) and C-O distances are in the expected range for this type of compound. The cyclopentadienyl rings in the ferrocenyl group adopt an eclipsed configuration. Since alkynes are considered tautomers of vinylidenes, we might think that, initially, the alkyne HCtCFc ligand in the derivative [{Co2(CO)6}(μ,η2-FcCtCH)] undergoes a rearrangement to form the vinylidene compound [{Co2(CO)6}(μ,η2CdC(H)Fc]. Further protonation of the CdC(H)Fc group, probably as a consequence of the presence of residual water in the solvent, yields the carbyne ligand μ3-CCH2Fc. Finally, addition of a Co(CO)3 fragment to the molecule affords the trinuclear cluster [{Co3(CO)9}(μ3-CCH2Fc)] (2). Following the synthetic method used before for the model compound [FcC(SiEt3)dCH2] (1), the reaction between [{Co2(CO)6}(μ,η2-FcCCH)] and the carbosilane dendrimer Si[CH2CH2CH2Si(CH3)2H]4 was carried out, yielding compound Si[CH2CH2CH2Si(CH3)2C(Fc)dCH2]4 (3) (Scheme 1). The structure of 3 was determined on the basis of 1H, 13C{1H}, and 29Si{1H} NMR spectroscopy and mass spectrometry. The Markovnikov addition of the carbosilane dendrimer to the CC triple bond was inferred from the two doublet signals observed in the 1H NMR spectrum at 6.10 and 5.46 ppm with a coupling constant of 2.7 Hz. Evidence for the complete functionalization of the four reactive sites in the organosilicon dendritic core with ferrocenyl moieties is provided by the expected integration of protons corresponding to the peripheral ferrocenyl groups as well as those corresponding to the CH2 and CH3 fragments which appear in the expected range. A HMBC 1H-29Si NMR experiment was also carried out, and resonances observed at 0.6 and -4.4 ppm were assigned to the silicon atoms [Si(CH2)4] and [Si(CH3)2], respectively. Additionally, the molecular ion m/z 1273 that appears in its MALDI mass spectrum indicates that the dendrimer has been completely functionalized. In order to extend the hydrosilylation study, we explored the role of the butadiynyl derivatives [{Co2(CO)6}(μ,η2FcCtCCtCR)] (R = Fc, H, or SiMe3), which contain only one of the two CtC bonds coordinated to dicobalthexacarbonyl. Compound [(E)-FcCtCC(SiEt3)dC(H)Fc] (4) has been obtained in a 46% yield by reaction of [{Co2(CO)6}(μ,η2FcCCCtCFc] with the silane HSiEt3 in 1:1.25 stoichiometry (Scheme 1). The addition of the hydrogen to the carbon atom that is carrying the Fc substituent was confirmed by 1H and 13 C{1H} NMR data, while the assignment of the SiEt3 group has been inferred from a HMBC 1H-29Si NMR experiment. Additionally, the absence of correlation between the proton on the

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CH2Ph, Ph, Fc) to give [FcCdC(R)C(OMe)(C3H5) CdO].38 It has also been reported that cyclopentenones are formed by decomplexation of alkyne-dicobalthexacarbonyls in the presence of alkenes, following a Pauson-Khand reaction.35 Compound 5 was fully characterized by 1H and 13C{1H} NMR spectroscopy as well as mass spectrometry. The NMR data agree with those observed for other cyclobutenones reported before.38 A stretching band at 1746 cm-1 observed in the IR spectrum (KBr disk) corresponds to the ketone group. A possible mechanism for the formation of compound 5 is outlined in Scheme 2. It has been previously proposed that Co2(CO)8 in the presence of silanes HSiR3 affords the HCo(CO)4 and R3SiCo(CO)4 species. On this basis, an initial coordination of a molecule of FcCtCCtCFc to Et3SiCo(CO)3 followed by insertion into the Si-Co bond affords the species A. An oxidative addition of the silane HSiEt3 to the cobalt in A yields compound B. Migration of the hydrogen atom from the metal to the alkyne carbon atom and formation of the new C(O)-C bond generates the metallacycle C. Finally, the cyclobutenone 5 might be formed by elimination of the cobaltcarbonyl fragment. Suitable crystals for an X-ray diffraction study of compound 5 were obtained from a hexane/CH2Cl2 solution at -20 °C, and its 1922

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Organometallics molecular structure is shown in Figure 2. The four-membered ring is a planar scalene quadrangle. The C-C double bond [C(2)-C(3) 1.375(9) and C(4)-C(5) 1.343(8) Å], C-C single bond [C(3)-C(4) 1.486(8) Å], and C-O double bond [1.184(8) Å] lengths lie in the range observed in other cyclobutenones.36 One of the ferrocenyl groups shows eclipsed cyclopentadienyl rings, but these are staggered in the other. The functionalized dendrimer (Z)-Si[CH2CH2CH2Si(CH3)2C{CtCFc}dC(H)Fc]4 (6) was prepared according to the synthetic method used for [(E)-FcCtCC(SiEt3)dC(H)Fc] (4) (Scheme 1). It is noteworthy that the reaction of

Figure 2. ORTEP view of compound 5 (thermal ellipsoids at the 50% probability level). Hydrogen atoms (except H5) have been omitted for clarity. Selected bond distances (Å) and angles (deg): C(1)-C(2) 1.513(9), C(2)-C(3) 1.375(9), C(3)-C(4) 1.486(8), C(4)-C(1) 1.544(9), C(1)-O(1) 1.184(8), C(4)-C(5) 1.343(8), C(2)-C(3)C(4) 93.6(5), C(1)-C(2)-C(3) 92.8(5).

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[{Co2(CO)6}(μ,η2-FcCCCtCFc)] with HSiEt3 yields the E-isomer of 4, as mentioned before, while the analogous reaction using Si[CH2CH2CH2Si(CH3)2H]4 generates the Z-isomer of 6 (Figure 3a). The HMBC 1H-29Si NMR spectrum shows a correlation between the silicon atom in the SiMe2 group (-1.8 ppm) and the olefinic hydrogen (6.53 ppm), suggesting a trans configuration (Figure 3b). Additionally, in the HMBC 1H-13C NMR spectrum, the same olefinic hydrogen shows correlation with the carbon atoms C2 (116.9 ppm) and CR (82.8 ppm) but not with C3, which is in agreement with the proposed configuration (Figure 3c). The electrochemical behavior of the model diferrocenylalkynyl complex 4 and the corresponding dendrimer 6 has been examined by cyclic voltammetry (CV) in dichloromethane solution. As expected, both ferrocenylalkynyl compounds show two one-electron reversible oxidation processes (see for example Figure 4). The first reversible anodic wave, at 1E1/2 = 0.47 V and

Figure 4. Cyclic voltammograms of dendrimer 6 (5  10-4 M in ferrocene centers) in CH2Cl2 with 0.1 M TBAH as supporting electrolyte, measured at a Pt electrode with 100 mV s-1 scan rate.

Figure 3. (a) Proposed configuration with labeled atoms, (b) HMBC 1H-29Si NMR, and (c) HMBC 1H-13C NMR for compound 6. 1923

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Scheme 3. Synthesis of Compounds 7-15

1

E1/2 = 0.46 V (vs SCE), for 4 and 6, respectively, corresponds to the oxidation of the ferrocenyl vinyl subunits, resulting in the formation of monocationic 4þ and tetracationic species 64þ, respectively. At a higher potential (2E1/2 = 0.62 V and 2E1/2 = 0.58 V), the ferrocenyl ethynyl subunits are oxidized, giving the dicationic and octacationic compounds 42þ and 68þ, respectively. For both redox couples, the peak current ratio ipc/ipa is approximately 1, and the peak currents scale with the square root of the scan rate, indicating that the redox processes are diffusion controlled. The potential value of the second process is considerably more positive than that of the first one. This is due to the ability of the triple bonds to accept electron density from the iron(II) metal center, making the oxidation of the ferrocene unit thermodynamically more difficult than that of the ferrocenyl group linked to the CdC bond. It is known that the asymmetric butadiynes RCtCCtCR0 react with Co2(CO)8 in 1:1 stoichiometry to yield a mixture of two possible isomers, [{Co2(CO)6}(μ,η2-RCCCtCR0 )] and [{Co2(CO)6}(μ,η2-RCtCCCR0 )], although in some cases a coordinative preference toward one of the two CtC bonds has been observed and also small amounts of compounds [{Co2(CO)6}2(μ,η2,η2-RCCCCR0 )] have been obtained as a result of the double addition.39 We report here the coordinative preference of FcCtCCtCH in its 1:1 stoichiometric reaction with Co2(CO)8 to generate compound [{Co2(CO)6}(μ,η2FcCtCCCH)] (8), while a mixture of the two isomers [{Co2(CO)6}(μ,η2-FcCtCCCSiMe3)] (10) and [{Co2(CO)6} (μ,η2-FcCCCtCSiMe3)] (11), in a 20:80 ratio, is obtained using FcCtCCtCSiMe3 as precursor. Additionally, small amounts

of [{Co2(CO)6}2(μ,η2,η2-FcCCCCH)] (7) or [{Co2(CO)6}2 (μ,η2,η2-FcCCCCSiMe3)] (9) have been obtained in the respective reactions (Scheme 3). We found some difficulties in separating pure samples of the isomers 10 and 11 from the mixture by chromatography using different solvents. Although a sole green band is observed in the column, the fact that the minor compound 10 goes down at the beginning of the band together with compound 11 allowed us to isolate milligram quantities of a pure sample of 11 by collecting the end of the band. In this way, these two isomers were identified by IR and 1H NMR spectroscopy. Compounds 7-11 have been characterized by IR and 1H and 13C{1H} NMR spectroscopy as well as mass spectrometry (see Experimental Section). Their IR spectra show a pattern in the carbonyl region similar to those reported for analogous compounds [{Co2(CO)6}n(FcCt CCtCFc)] (n = 1 or 2),40 [{Co2(CO)6}n(Cp(CO)2FeCtCCCH)] (n = 1 or 2),41 and [{Co2(CO)6}n{HCtC(C5H5FeC5H3)C(CH3)2(C5H4FeC5H4)CtCH}] (n = 1 or 2).42 Additionally, the different stretching band corresponding to the free CtC observed in the IR spectra of 10 (2180 cm-1) and 11 (2121 cm-1) seems to indicate that the Co2(CO)6 fragment is located at a different position in both isomers. In the 1H and 13 C{1H} NMR spectra resonances corresponding to the organic groups as well as to the hydrogen of the terminal alkyne in compounds 7 and 8 are observed. Suitable crystals for an X-ray analysis of [{Co2(CO)6}(μ,η2FcCtCCCH)] (8) and [{Co2(CO)6}2(μ,η2:η2-FcCCCCSiMe3)] (9) have been obtained from a hexane/dichloromethane or hexane solution at -20 °C, respectively. The molecular structures 1924

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Organometallics

Figure 5. ORTEP view of compound 8 (thermal ellipsoids at the 50% probability level). Hydrogen atoms (except H1) have been omitted for clarity. Selected bond distances (Å) and angles (deg): C(1)-C(2) 1.333(5), C(2)-C(3) 1.386(5), C(3)-C(4) 1.193(5), Co(1)-Co(2) 2.464 (1), C(1)-Co(1) 1.935(4), C(1)-Co(2) 1.937(4), C(2)-Co(1) 1.953(4), C(2)-Co(2) 1.960(4), C(1)-C(2)-C(3) 145.0(4), C(3)-C(2)-Co(1) 130.8(3).

Figure 6. ORTEP view of compound 9 (thermal ellipsoids at the 50% probability level). Hydrogen atoms have been omitted for clarity. Selected bond distances (Å) and angles (deg): C(1)-C(2) 1.34(2), C(3)-C(4) 1.35(2), Co(1)-Co(2) 2.486(3), Co(3)-Co(4) 2.492(3), C(1)-Co(1) 1.97(1), C(1)-Co(2) 1.95(1), C(2)-Co(1) 1.98(1), C(2)-Co(2) 1.99(2), C(3)-Co(3) 2.00(1), C(3)-Co(4) 1.99(1), C(4)-Co(3) 2.00(1), Si(1)-C(4)-C(3) 153.2(1), Si(1)C(4)-Co(3) 128.9(7), Si(1)-C(4)-Co(4) 128.2(8).

are depicted in Figures 5 and 6, respectively, and selected lengths and angles are collected in the figure captions. Compound 9 shows two crystallographically independent molecules in the asymmetric unit. Discussion will therefore be limited to only one of these molecules. The molecules are made up of one (compound 8) or two (compound 9) dicobalt tetrahedrane units linked to a C-C bond. The Co-Co, C-C, and Co-C (alkyne) distances are within the ranges found in compounds [{Co2(CO)6}2(μ,η2,η2PhCCCCPh)],43 [{Co2(CO)6}2(μ,η2,η2-FcCCCCFc)],44 [{Co2 (CO)6}2(μ,η2,η2-PhCCCCFc)],39 [{Co2(CO)6}((Me3Si)3SiCt CR)] (R = H, Ph),45 [{Co2(CO)6}(PhCtC-C7H2(OH)

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(2,3-Ph)2],46 and [{Co2(CO)6}(FcC(CH3)2(C5H4FeC5H4)Ct CH)].47 As expected, the C-C(Alkyne) bond distances in 9 [C(1)C(2) 1.34(2), C(3)-C(4) 1.35(2) Å] and 8 [C(1)-C(2) 1.333(5) Å] are elongated as a consequence of the coordination to the cobalt carbonyl fragment. In fact, distances of 1.192(5) and 1.107(5) Å were observed in FcCtC-CtCH for the uncoordinated CtC bonds.48 Vinylsilanes [FcCtCC(SiEt3)dCH(R)] [R = H (13); SiMe3 (15)] and [FcC(H)dC(SiEt3)CtCSiMe3] (14) are formed selectively from the precursors [{Co2(CO)6}(μ,η2FcCtCCCR)] [R = H (8), SiMe3 (10)] and [{Co2(CO)6} (μ,η2-FcCCCtCSiMe3)] (11), respectively (Scheme 3). In addition, the new green complex [{Co2(CO)6}μ,η2-FcCCC(SiEt3)dCH2] (12) has been obtained in a 7% yield from the reaction of [{Co2(CO)6}(μ,η2-FcCtCCCH)] (8) with HSiEt3. Its IR pattern in the carbonyl region as well as the presence in the FABþ mass spectrum of peaks corresponding to the loss of 2-6 CO ligands and resonances observed in its 1H NMR spectrum support this formulation. It is remarkable that the formation of 12 implies decomplexation of the Co2(CO)6 fragment from the CtC bond in which the HSiEt3 was added followed by migration of the cobaltcarbonyl to the free CtC bond. Characterization of compounds 12-15 has been undertaken by 1H, 13C{1H}, and 29Si{1H} NMR spectroscopy as well as mass spectrometry. Useful information was provided by 29Si{1H} NMR data for 14 and 15, whose different shifting clearly indicate in which CtC bond the hydrosilylation has taken place. Thus, the resonance assigned to the SiMe3 group appears at -9.3 ppm in compound 14, while this signal is widely shifted upfield (-19.2 ppm) in 15, being in accordance with the data reported.49 A few examples of carbosilane dendrimers containing peripheral alkynyl-dicobalthexacarbonyl complexes have been prepared by coordination of the alkynyl groups50-52 at the end of each arm of the dendrimer to Co2(CO)6. However, to the best of our knowledge, no heterometallic dendrimer functionalized with ferrocenylalkynyl-dicobalthexacarbonyl complexes has been reported so far. We have carried out studies to check if the tetracobaltdodecacarbonyl diynes [{Co2(CO)6}2(μ,η2,η2FcCCCCR)] (R = Fc or SiMe3) could act as precursors for this goal in the case where they could undergo hydrosilylation by decomplexation of only one of the two dicobalthexacarbonyl fragments. However, the results indicated that a total decomplexation takes place even using a lower amount of HSiEt3 than the corresponding 1:1 ratio, affording compounds 4 and 14 but in a lower yield than those obtained from the starting materials [{Co2(CO)6}(μ,η2-FcCCCtCR)] (R = Fc or SiMe3).

’ EXPERIMENTAL SECTION Materials and Equipment. All reactions were performed under an inert atmosphere using standard Schlenk techniques. Solvents were dried by standard procedures over the appropriate drying agents and distilled immediately prior to use. The starting materials [{Co2(CO)6}(μ,η2FcCCH)],44 [{Co2(CO)6}(μ,η2-FcCCCtCFc)],40 Si[CH2CH2CH2Si(CH3)2H]4,53 [FcCtCCtCSiMe3],54 and [FcCtCCtCH]55 were prepared as previously described. Infrared spectra were recorded on a Perkin-Elmer Spectrum BX FT-IR spectrophotometer using NaCl cells. NMR spectra were recorded on Bruker AMX-300 and Bruker DRX-500 spectrometers. Chemical shifts are reported in parts per million (δ) with reference to residual solvent resonances for 1H and 13C{1H} NMR (CDCl3, 1H, δ 7.26 ppm; 13C, δ 77.0 ppm). 29Si NMR spectra were recorded with inverse-gated proton decoupling in order to minimize 1925

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Table 1. Crystallographic Data for Complexes 2, 5, 8, and 9 2

5

8

9

empirical formula

C21H11Co3FeO9

C31H34Fe2OSi

C20H10Co2FeO6

C29H18Co4FeO12Si

fw

639.94

562.37

519.99

878.09

temp [K]

200

200

200

200

λ(Mo KR) [Å]

0.71073

0.71073

0.71073

0.71073

cryst syst

monoclinic

orthorhombic

monoclinic

monoclinic

space group

P21/m

P212121

P21/a

Cc

a [Å]; R [deg]

10.130(2)

14.644(2)

13.911(2)

15.988(2)

b [Å]; β [deg] c [Å]; γ [deg]

10.779(2); 112.49(1) 11.293(1)

7.444(1) 24.675(8)

9.287(2); 109.05(1) 15.615(3)

9.212(3); 93.41(4) 46.330(15)

volume [Å3]; Z

1139.3(3); 2

2690.0(9); 4

1906.8(5); 4

6811(3); 8

Fcalcd [g cm-3]

1.865

1.389

1.811

1.713

μ [mm-1]

2.819

1.145

2.505

2.416

F(000)

632

1176

1032

3488

cryst size [mm]

0.35  0.32  0.20

0.40  0.40  0.16

0.37  0.30  0.10

0.22  0.18  0.17

3.07 to 27.9°

3.1 to 27.5°

3.01 to 27.5°

θ range

3.44 to 27.5°

index ranges collected reflns

-13 to 12, -13 to 14, 0 to 14 -19 to 18, -9 to 9, 0 to 32 -18 to 17, -12 to 12, 0 to 20 -16 to 19, -11 to 11, -60 to 60 21 770 48 801 43 633 27 876

indep reflns

2749

6258

4383

11 635

reflections [F > 4σ(F)]

2148

3530

2854

7234

goodness-of-fit on F2

0.986

1.013

0.847

1.016

final R indices

R1 = 0.023; wR2 = 0.050

R1 = 0.075; wR2 = 0.120

R1 = 0.039; wR2 = 0.082

R1 = 0.074; wR2 = 0.164

R indices (all data)

R1 = 0.040; wR2 = 0.054

R1 = 0.152; wR2 = 0.144

R1 = 0.082; wR2 = 0.101

R1 = 0.142; wR2 = 0.213

0.492/-0.812

0.487/-0.814

0.820/-0.854

largest diff peak/hole [e Å-3] 0.300/-0.463

nuclear Overhauser effects. Carbon and silicon NMR assignments were routinely confirmed by 1H-13C and 1H-29Si HMBC experiments. FAB mass spectra analyses were conducted on a VG Auto Spec mass spectrometer equipped with a cesium ion gun. The matrix was nitrobenzyl alcohol (m-NBA). The MALDI-TOF mass spectra were obtained using a Reflex III (Bruker) mass spectrometer equipped with a nitrogen laser emitting at 337 nm. The matrix used in this technique was trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB). Elemental analyses were performed on a LECO CHNS-932. Electrochemical Measurements. Cyclic voltammetric experiments were performed on a BAS CV-50W potentiostat. CH2Cl2 (spectrograde) for electrochemical measurements was freshly distilled from calcium hydride under nitrogen. The supporting electrolyte tetran-butylammonium hexafluorophosphate (TBAH, Fluka) was purified by recrystallization from ethanol, dried under vacuum at 60 °C, and used in a concentration of 0.1 M in all measurements. A conventional sample cell operating under an atmosphere of prepurified nitrogen was used for cyclic voltammetry. All cyclic voltammetric experiments were performed using a platinum-disk working electrode (A = 0.020 cm2) polished prior to use with either 0.05 μm alumina/water slurry or 1 μm diamond paste (Buehler) and rinsed thoroughly with purified water and acetone. All potentials are referenced to the saturated calomel electrode (SCE). A large area-coiled platinum wire was used as a counter electrode. Solutions for cyclic voltammetry were typically 0.5 mM in the redoxactive species and were deoxygenated by purging with prepurified nitrogen. No iR compensation was used. X-ray Structure Determination. X-ray crystals of 2, 5, 8, and 9 were grown as described in the Experimental Section. Crystals were covered with a layer of a viscous perfluoropolyether (Fomblin Y). A suitable crystal was selected with the aid of a microscope, attached to a glass fiber, and immediately placed in the low-temperature nitrogen stream (200 K) of the Bruker-Nonius KappaCCD diffractometer equipped with an Oxford Cryostream 700 unit. Crystallographic data for all the complexes are presented in Table 1. The structures were

solved, using the WINGX package,56 by direct methods (SHELXS-97) and refined by least-squares against F2 (SHELXL-97).57 Absorption correction procedures were carried out using the multiscan SORTAV program.58 All the non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included, positioned geometrically, and refined by using a riding model except H5 in complex 5 and all of complex 8, which were directly located in the Fourier difference map and isotropically refined. Hydrosilylation of [{Co2(CO)6}(μ,η2-FcCCH)]. HSiEt3 (52 μL, 0.32 mmol), dissolved in 2 mL of 1,2-dichloroethane, was added dropwise to a solution of [{Co2(CO)6}(μ,η2-FcCCH)] (200 mg, 0.40 mmol) in 25 mL of the same solvent under an argon atmosphere and in the absence of light. The mixture was left stirring and heating at 50 °C for 4 h. During this time the color of the reaction changed from dark green to brown. The solvent was then removed under vacuum, and the residue was purified by TLC using hexane as eluent. The first yelloworange band afforded compound [FcC(SiEt3)dCH2] (1) (64 mg, 0.20 mmol, 63%) as the main product followed by a small amount of unreacted [{Co2(CO)6}(μ,η2-FcCCH)]. The second red band yielded compound [{Co3(CO)9}(μ3-CCH2Fc)] (2) (10 mg, 0.016 mmol, 5%). Crystals of 2 suitable for a single-crystal diffraction study were grown from a concentrated hexane solution at -20 °C. Characterization Data for 1. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.21, 5.50 (d, 2  1H, J = 3.0 Hz, dCH2), 4.30, 4.17 (t, 2  2H, J = 1.8 Hz, C5H4), 4.06 (s, 5H, C5H5), 0.95 (t, 9H, J = 8.0 Hz, CH3), 0.70 (q, 6H, J = 8.0 Hz, CH2). 13C{1H} NMR (CDCl3, 75.46 MHz, 22 °C) δ: 144.9 (CdCH2), 125.9 (CdCH2), 69.4 (C5H5), 68.9, 67.7, 67.5 (C5H4), 7.4 (CH2), 3.6 (CH3). Anal. Calcd for C18H26FeSi (Found): C, 66.25 (65.53); H, 8.03 (8.12). MS-FABþ (m/z): 326 [Mþ]. Characterization Data for 2. IR (hexane) cm-1 νCO: 2101 w, 2052 vs, 2037 m, 2019 w. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 4.54 (s, 2H, CH2), 4.24, 4.15 (t, 2  2H, J = 1.8 Hz, C5H4), 4.19 (s, 5H, C5H5). 13 C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 304.0 (μ3-C), 200.0 (CO's), 70.4, 69.9, 68.0 (C5H4), 68.8 (C5H5), 57.7 (CH2). MS-FABþ 1926

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(m/z): 639 [Mþ], 611 - 387 [Mþ - nCO, n = 1-9]. Anal. Calcd for C21H11Co3FeO9 (Found): C, 39.44 (39.63); H, 1.72 (1.90).

Reaction of [{Co2(CO)6}(μ,η2-FcCCH)] with Si[CH2CH2CH2Si(CH3)2H]4. To a solution of [{Co2(CO)6}(μ,η2-







FcCCH)] (422 mg, 0.86 mmol) in 35 mL of 1,2-dichloroethane was added Si[CH2CH2CH2Si(CH3)2H]4 (74 mg, 0.17 mmol) dissolved in 5 mL of the same solvent. The reaction mixture was stirred in the dark at 50 °C for 24 h. After removal of the solvent in vacuo, the residue was purified by TLC using hexane/CH2Cl2 (4:3) as eluent. The major band corresponds to the orange compound Si[CH2CH2CH2Si(CH3)2C(Fc)dCH2]4 (3) (40 mg, 0.03 mmol, 19%). Several bands of unidentified compounds in trace amounts were also obtained from the column. Characterization Data for 3. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.10, 5.46 (d, 4  2H, J = 2.7 Hz, dCH2), 4.35, 4.20 (t, 4  4H, J = 1.9 Hz, C5H4), 4.07 (s, 4  5H, C5H5), 1.30, 0.76, 0.54 (m, 4  6H, CH2CH2CH2), 0.20 (s, 4  6H, CH3). 13C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 147.1 (CdCH2), 123.7 (CdCH2), 87.4, 68.0, 67.1 (C5H4), 69.4 (C5H5), 20.8, 18.7, 17.5 (CH2CH2CH2), -2.03 (CH3). 29 Si{1H} NMR (CDCl3, 59.62 MHz, 22 °C) δ: 0.6 (Si(CH2)4), -4.4 (Si(CH3)2). MS-MALDI (m/z): 1273 [Mþ], 1213 [Mþ - 4CH3], 1078 [Mþ - 3Fc]. Hydrosilylation of [{Co2(CO)6}(μ,η2-FcCCCtCFc)]. To a solution of [{Co2(CO)6}(μ,η2-FcCCCtCFc)] (150 mg, 0.2 mmol) in 30 mL of 1,2-dichloroethane was added dropwise HSiEt3 (25 μL, 0.16 mmol) dissolved in 2 mL of the same solvent. The mixture was stirred in the absence of light and heated at 50 °C for 4 h. The solvent was then removed in vacuo, and the residue was purified by TLC using a mixture of hexane/THF (16:1) as eluent. Compound [(E)-FcCtCC(SiEt3)dC(H)Fc] (4) was obtain as an orange band (40 mg, 0.07 mmol, 47%) followed by a red band corresponding to compound [C(O)C(Fc)dC(SiEt3) CdC(H)Fc] (5) (9 mg, 0.016 mmol, 10%), which crystallized from a solution of hexane/dichloromethane at -20 °C, giving red crystals suitable for a single-crystal X-ray diffraction study. Characterization Data for 4. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.56 (s, 1H, dCH), 4.94, 4.48, 4.31, 4.25 (t, 4  2H, J = 1.8 Hz, 2  C5H4), 4.26, 4.15 (s, 2  5H, C5H5), 1.06 (t, 9H, J = 7.6 Hz, CH3), 0.77 (q, 6H, J = 7.6 Hz, CH2). 13C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 144.1 (dCH), 116.9 (CdCH), 88.4, 82.8 (CtC), 70.8, 69.3, 69.2, 66.8, 67.4, 69.1 (C5H4), 69.7, 69.4 (C5H5), 7.5 (CH2), 3.1 (CH3). 29 Si{1H} NMR (CDCl3, 59.62 MHz, 22 °C) δ: 3.7 (SiEt3). MS-FABþ (m/z): 534 [Mþ]. Anal. Calcd for C30H34Fe2Si 3 1.5CH2Cl2 (Found): C, 57.17 (56.89); H, 5.64 (5.58). Characterization Data for 5. IR (KBr disk, cm-1): νCO 1746. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 5.79 (s, 1H, dCH), 4.83, 4.28 (m, 2  2H, C5H4), 4.76, 4.44 (t, 2  2H, J = 1.7 Hz, C5H4), 4.16, 4.11 (s, 2  5H, C5H5), 1.08 (t, 9H, J = 6.8 Hz, CH3), 0.90 (q, 6H, J = 6.8 Hz, CH2). 13 C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 195.7 (CdO), 161.1 (dC(Fc)), 141.2 (dC(SiEt3)), 130.9 (CdCH), 128.8 (dCH), 71.4, 70.2, 68.2 (C5H4), 70.0 (C5H5), 8.1 (CH2), 3.8 (CH3). 29Si{1H} NMR (CDCl3, 59.62 MHz, 22 °C) δ: not observed. MS-FABþ (m/z): 562 [Mþ].

Reaction of [{Co2(CO)6}(μ,η2-FcCCCtCFc)] with Si[CH2CH2CH2Si(CH3)2H]4. To a solution of [{Co2(CO)6}(μ,η2-

FcCCCtCFc)] (600 mg, 0.85 mmol) in 35 mL of 1,2-dichloroethane was added dropwise Si[CH2CH2CH2Si(CH3)2H]4 (74 mg, 0.17 mmol) dissolved in 5 mL of the same solvent. The reaction mixture was stirred in the dark at 50 °C for 24 h. The solvent was then removed under reduced pressure, and the crude product was purified by TLC using a mixture of hexane/CH2Cl2 (4:3), giving a band that corresponded to the orange compound (Z)-Si[CH2CH2CH2Si(CH3)2C{CtCFc}dC(H)Fc]4 (6) (80 mg, 0.04 mmol, 23%). Characterization Data for 6. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.53 (s, 4  1H, dCH), 5.02, 4.47, 4.39 (m, 4  6H, C5H4), 4.26 (br s, 28H, C5H4 þ C5H5), 4.20 (m, 4  5H, C5H5), 1.44, 0.79, 0.67 (m, 24H,

CH2CH2CH2), 0.20 (s, 4  6H, CH3). 13C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 143.2 (dCH), 119.5 (CdCH), 98.1, 88.1 (CtCFc), 82.8, 71.0, 69.4, 68.6, 67.4 (C5H4), 69.8, 69.6 (C5H5), 20.0, 18.7, 17.6 (CH2CH2CH2), -3.2 (CH3). 29Si{1H} NMR (CDCl3, 59.62 MHz, 22 °C) δ: 0.6 (Si(CH2)4), -1.8 (Si(CH3)2). MS-MALDI (m/z): 2105 [Mþ]. Reaction of FcCtCCtCH with Co2(CO)8. To a solution of FcCtCCtCH (360 mg, 1.5 mmol) in 30 mL of THF was added Co2(CO)8 (479 mg, 1.4 mmol), and the mixture was stirred at room temperature for 1 h. The color of the reaction turned immediately from orange to dark brown. The solvent was then removed under reduced pressure, and the residue was taken up in the minimal amount of hexane and purified by column chromatography on silica gel. Elution with hexane/toluene (10:1) afforded a first, brown band corresponding to compound [{Co2(CO)6}2(μ,η2,η2-FcCCCCH)] (7) (200 mg, 0.25 mmol, 16%) followed by a second, dark purple band corresponding to compound [{Co2(CO)6}(μ,η2-FcCtCCCH)] (8) (350 mg, 0.67 mmol, 45%). Suitable crystals for an X-ray diffraction study of compound 8 were grown from a hexane/CH2Cl2 solution at -20 °C. Characterization Data for 7. IR (hexane, cm-1): νCO 2101 m, 2080 s, 2061 vs, 2034 s, 2026 s, 1983 w. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.55 (s, 1H, CH), 4.46, 4.37 (m, 2  2H, C5H4), 4.26 (s, 5H, C5H5). MS-FABþ (m/z): 806 [Mþ], 750 - 470 [Mþ - nCO; n = 2, 4-12]. Characterization Data for 8. IR (hexane, cm-1): νCtC 2180 w; νCO 2096 m, 2060 vs, 2035 vs, 2020 sh, 1987 w. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.22 (s, 1H, CH), 4.50, 4.28 (m, 2  2H, C5H4), 4.22 (s, 5H, C5H5). 13C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 198.9 (CO0 s), 99.1, 82.5 (CtC), 70.0 (C5H5), 71.7, 70.7, 69.4 (C5H4), 74.3 (CCH), 65.1 (CCH). MS-FABþ (m/z): 520 [Mþ], 464-352 [Mþ - nCO, n = 2-6], 234 [Mþ - Co2(CO)6]. Anal. Calcd for C20H10O6FeCo2 3 1/5 CH2Cl2 (Found): C, 45.14 (45.20); H, 1.94 (1.97). Reaction of FcCtCCtCSiMe3 with Co2(CO)8. To a stirring solution of FcCtCCtCSiMe3 (312 mg, 1.02 mmol) in 30 mL of tetrahydrofuran was added Co2(CO)8 (342 mg, 1 mmol) in small portions, and the mixture was stirred for 1 h at room temperature. The solvent was removed in vacuo, and the products were separated by column chromatography. Elution with a mixture of hexane/toluene (10:1) gave two major bands. The first one corresponds to the black compound [{Co2(CO)6}2(μ,η2,η2-FcCCCCSiMe3)] (9) (38.7 mg, 0.045 mmol, 4%), and the second, green band is a mixture of the two isomers [{Co2(CO)6}(μ,η2-FcCtCCCSiMe3)] (10) and [{Co2(CO)6}(μ,η2-FcCCCtCSiMe3)] (11). Collection of the end of the green band gave a pure sample of 11 (at least 234 mg, 0.40 mmol, 39%). Single crystals of compound 9, suitable for X-ray crystallography, were grown from a saturated solution in hexane at -20 °C. Characterization Data for 9. IR (hexane, cm-1): νCO 2097 m, 2077 s, 2057 vs, 2032 s, 2022 s, 2011 sh, 1978 w. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 4.45, 4.34 (m, 2  2H, C5H4), 4.28 (s, 5H, C5H5), 0.35 (s, 9H, SiMe3). 13C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 199.5 (CO's), 118.6, 102.3, 96.2, 84.2 (CtC), 70.9, 70.0, 68.7 (C5H4), 69.5 (C5H5), 1.0 (SiMe3). MS-FABþ (m/z): 787 [Mþ], 822 - 542 [Mþ - nCO; n = 2, 5-12]. Anal. Calcd for C29H18FeSiO12Co4 3 1/2CH2Cl2 (Found): C, 38.49 (38.50); H, 2.08 (2.13). Characterization Data for 10. IR (hexane, cm-1): νCtC 2180 vw; νCO 2091 m, 2056 vs, 2030 br s, 2020 sh, 1984 w. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 4.49 (m, 2H, C5H4), 4.21 (br s, 7H, C5H4 þ C5H5), 0.37 (s, 9H, SiMe3). MS-FABþ (m/z): 536 - 424 [Mþ - nCO; n = 2-6]. Characterization Data for 11. IR (hexane, cm-1): νCtC 2121 vw; νCO 2092 m, 2058 vs, 2035 s, 2028 m, 2018 sh, 1986 w. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 4.45, 4.36 (m, 2  2H, C5H4), 4.30 (s, 5H, C5H5), 0.29 (s, 9H, SiMe3). MS-FABþ (m/z): 536 - 424 [Mþ - nCO; n = 2-6]. Hydrosilylation of [{Co2(CO)6}(μ,η2-FcCtCCCH)]. HSiEt3 (37 μL, 0.23 mmol), dissolved in 2 mL of 1,2-dichloroethane, was 1927

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added dropwise to a solution of [{Co2(CO)6}(μ,η2-FcCtCCCH)] (8) (150 mg, 0.29 mmol) in 20 mL of the same solvent. The mixture was left stirring in the dark and heating at 50 °C for 4 h. During this time the color of the reaction changed from dark purple to brown. The solvent was then removed under vacuum, and the residue was purified by TLC using a mixture of hexane/toluene (20:1) as eluent. The first, yellow band corresponds to an unidentified compound in trace amounts. The second, green band yielded [{Co2(CO)6}(μ,η2-FcCCC(SiEt3)dCH2)] (12) (10 mg, 0.015 mmol, 7%) followed by a third, yellow-orange band corresponding to compound [FcCtCC(SiEt3)dCH2] (13) (20 mg, 0.06 mmol, 25%). Characterization Data for 12. IR (hexane, cm-1): νCO 2084 m, 2048 vs, 2023 s, 2017 sh, 1974 vw. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.39, 5.85 (m, 2  1H, CH2), 4.39, 4.32 (m, 2  2H, C5H4), 4.22 (s, 5H, C5H5), 0.93 (m, 9H, CH3), 0.70 (m, 6H, CH2). MS-FABþ (m/z): 580 - 468 [Mþ - nCO, n = 2-6]. Characterization Data for 13. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.14, 5.65 (d, 2  1H, J = 1.2 Hz, CH2), 4.40 (m, 2H, C5H4), 4.20 (s br, 7H, C5H4 þ C5H5), 1.03 (t, 9H, J = 7 Hz, CH3), 0.73 (q, 6H, J = 7 Hz, CH2). 29Si{1H} NMR (CDCl3, 59.62 MHz, 22 °C) δ: 3.2 (SiEt3). 13 C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 133.6 (dCH2), 131.8 (CdCH2), 92.1, 87.8 (CtC), 71.2, 68.6, 66.2 (C5H4), 69.8 (C5H5), 7.4 (CH2), 2.9 (CH3). MS-FABþ (m/z): 350 [Mþ].

Hydrosilylation

of

[{Co2(CO)6}(μ,η2-FcCCCtCSiMe3)].

HSiEt3 (23 μL, 0.14 mmol), dissolved in 2 mL of 1,2-dichloroethane, was added dropwise to a solution of [{Co2(CO)6}(μ,η2-FcCCCt CSiMe3)] (11) (100 mg, 0.17 mmol) in 15 mL of the same solvent. The mixture was left stirring in the dark at 50 °C for 4 h. The solvent was then removed in vacuo, and the residue was purified by column chromatography. Elution with hexane/toluene (20:1) gave a first band of traces of unreacted starting material followed by a second, brown band that afforded compound [(E)-FcC(H)dC(SiEt3)CtCSiMe3] (14) (32.5 mg, 0.06 mmol, 42%). Characterization Data for 14. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.58 (s, 1H, dCH), 4.92, 4.29 (m, 2  2H, C5H4), 4.12 (s, 5H, C5H5), 1.02 (t, 9H, J = 8 Hz, CH3), 0.73 (q, 6H, J = 8 Hz, CH2), 0.25 (s, 9H, SiMe3). 13C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 146.8 (dCH), 116.4 (CdCH), 107.6, 82.3 (CtC), 70.0, 69.6 (C5H4), 69.5 (C5H5), 7.4 (CH2), 3.0 (CH3), 0.1 (SiMe3). 29Si{1H} NMR (CDCl3, 59.62 MHz, 22 °C) δ: 4.0 (SiEt3), -19.2 (SiMe3). MS-FABþ (m/z): 422 [Mþ].

Hydrosilylation of the Mixture of Compounds 10 and 11. The procedure is analogous to that mentioned above but using a mixture of compounds 10 and 11 (100 mg, 0.17 mmol). After 4 h of reaction, the solvent was removed in vacuo, and the residue was purified by column chromatography. Elution with hexane gave a yellow band corresponding to compound [(Z)-FcCtCC(SiEt3)dC(H)SiMe3] (15) (8 mg, 0.016 mmol, 14%). Traces of unreacted starting material were obtained using hexane/toluene (20:1) as eluent followed by a brown band that corresponded to compound [(E)-FcC(H)dC(SiEt3)CtCSiMe3] (14) (21 mg, 0.04 mmol, 27%). Characterization Data for 15. 1H NMR (CDCl3, 300 MHz, 22 °C) δ: 6.46 (s, 1H, dCH), 4.43, 4.21 (m, 2  2H, C5H4), 4.20 (s, 5H, C5H5), 1.00 (t, 9H, J = 8 Hz, CH3), 0.72 (q, 6H, J = 8 Hz, CH2), 0.23 (s, 9H, SiMe3). 13C{1H} NMR (CDCl3, 125.77 MHz, 22 °C) δ: 153.4 (dCH), 142.4 (CdCH), 97.4, 89.0 (CtC), 71.0, 68.8, 66.8 (C5H4), 69.8 (C5H5), 7.4 (CH2), 2.9 (CH3), -0.7 (SiMe3). 29Si{1H} NMR (CDCl3, 59.62 MHz, 22 °C) δ: 2.6 (SiEt3), -9.3 (SiMe3). MS-FABþ (m/z): 422 [Mþ].

’ ASSOCIATED CONTENT

bS

Supporting Information. Complete crystallographic data for compounds 2, 5, 8, and 9 (CIF files) and 29Si-1H HMBC

spectra for compounds 4, 6, 14, and 15 are available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]; [email protected].

’ ACKNOWLEDGMENT We thank the Consejería de Educacion, Comunidad de Madrid (S-0505/PPQ-0328) and Factoría de Cristalizacion (CONSOLIDER-INGENIO 2010) for the financial support of this research. Also, A.N. thanks the Comunidad de Madrid for his “PIA” contract. ’ REFERENCES

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Organometallics

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dx.doi.org/10.1021/om1011903 |Organometallics 2011, 30, 1920–1929