Transition-metal silacyclohexyl derivatives. Crystal and molecular structure of carbonyl(η-cyclopentadienyl)(1 -phenyl-1 -silacyclohex-1 -yl)-(triphenylphosphine)iron(II)

Abstract

Synthesis of transition-metal silacyclohexyl complexes (1-metallo-1-silacyclohexanes) is reported via two established preparative routes: (a) reaction of 1-chloro-1 -silacyclohexanes with [Fe(η⁵-C₅H₅)(CO)₂]^– to give Si–Fe compounds [Fe(η⁵-C₅H₅)(CO)₂{[graphic omitted]H₂}] R²= H, (8); R²= Me, (9); R²= Ph (10)] followed by photochemical substitution with PPh₃ to give the corresponding complexes [Fe(η⁵-C₅H₅)(CO)(PPh₃){[graphic omitted]H₂}][R²= H, (11); R²= Me, (12); R²= Ph (13)] which are chiral at Fe; (b) hydrosilylation at the metal to give mononuclear complexes [Co(CO)₄{[graphic omitted]H₂}][ R²= Me, (14) R²= Ph, (15), R²= Cl (16)] and [Mn(CO)₅{[graphic omitted]H₂}][R²= Me, (17); R²= Ph (18)] from [Co₂(CO)₈] or [Mn₂(CO)₁₀], binuclear complexes [{M(CO)₄[[graphic omitted]H₂]}₂][M = Ru, R²= Me, (19), or Ph, (20); M = Os, R²= Me, (21)] with linear Si–M–M–Si skeletons from [Ru₃(CO)₁₂] or [Os₃(CO)₁₂], or [Os(CO)₄{[graphic omitted]H₂}₂](22). Infrared and ¹H, ¹³C, and ³¹P n.m.r. spectral data are reported, including resolution of diastereotopic shifts in ¹³C n.m.r spectra for compounds (12) and (13) arising from asymmetry at the iron centre. The crystal and molecular structure of the title compound (13) has been determined using single-crystal X-ray diffraction; the silacyclohexyl substituent adopts a flattened chair conformation with Si–Fe = 2.366(2)Å. Angles at Fe between the three different unidentate ligands are markedly distorted from 90°[97.2(2), 98.43(6), and 83.2(2)°]; this is interpreted in terms of steric congestion about the asymmetric metal centre and accordingly moderated reactivity of complex (15) towards a variety of reagents is observed compared with [Co(CO)₄(SiMe₃)].