New Investigations in Silanediyl Complex Chemistry:  Synthesis, Structure, and Bonding of 1-Metalla-2-sila-1,3-dienes

The synthesis and chemical behavior of the intra- and intermolecular donor-stabilized silanediyl complexes (C₆H₄CH₂NMe₂-2)(Cl)SiML_n (4, ML_n = Cr(CO)₅ 5, ML_n = Fe(CO)₄), (C₆H₅HCCH)(Cl)Si=ML_n·OP(NMe₂)₃ (21, ML_n = Cr(CO)₅; 22, ML_n = Fe(CO)₄), and (C₆H₅HCCH)(C₆H₅)SiFe(CO)₄·OP(NMe₂)₃ (23) is discussed. Nucleophilic substitution of the chloro atom in compounds 4 and 5 by different nucleophiles leads to a great variety of further functionalized silanediyl complexes of the type (C₆H₄CH₂NMe₂-2)(R)SiML_n (ML_n = Cr(CO)₅:  7, R = CH₃; 9, R = C₆H₅; 11, R = P(C₆H₅)₂; 13, R = CHCH₂. ML_n = Fe(CO)₄:  14, R = CHCH₂; 15, R = CH₃). Moreover, the 1-metalla-2-sila-1,3-dienes (C₆H₄CH₂NMe₂-2)(H₂CCH)Si=ML_n (13, ML_n = Cr(CO)₅; 14, ML_n = Fe(CO)₄) can be prepared by treatment of the hypervalent dichlorosilane (C₆H₄CH₂NMe₂-2)(H₂CCH)SiCl₂ (19) with the carbonylate dianions ML_n^2- (2, ML_n = Cr(CO)₅; 3, ML_n = Fe(CO)₄). Additionally, compounds of the latter type are accessible by photochemical coupling reactions of the pentavalent silane (C₆H₄CH₂NMe₂-2)(CH₃)SiH₂ (16) with the transition-metal carbonyls Cr(CO)₆ (17a), Fe(CO)₅ (17b), and (η5-C₅H₅)Mn(CO)₃ (17c), respectively. The intermolecular donor-stabilized 1-metalla-2-sila-1,3-dienes 21−23 can be prepared by the reaction of tetravalent dichlorosilanes [(R)(H)CCH](R‘)SiCl₂ (20a, R = H, R‘ = Cl; 20b, R = R‘ = C₆H₅) with the carbonylmetalates 2 and 3 and in the presence of OP(NMe₂)₃.