TRANSITION-METAL SILYL COMPLEXES .42. INFLUENCE OF PHOSPHANE LIGANDS ON FORMATION, STRUCTURE AND STABILITY OF HETERO BINUCLEAR COMPLEXES (CO)3(R'3P)(R3SI)FEMLN (M=CU, AG, AU, HG)

The anionic silyl complexes Na[Fe(CO)3(PR3')SiR3] (PR3' = PMe3: SiR3 = SiMePh2, SiMe3; PR3' = PnBu3: SiR3 = SiMePh2; PR3' = PPh2H: SiR3 = SiPh3, SiMe2Ph) were prepared by deprotonation of the corresponding hydrido silyl complexes. They react with CH3I or Me3SnCl to give mer-(CO)3(R3'P)(R3Si)Fe-ER3 (PR3' = PMe3 and PPh2H; ER3 = CH3, SnMe3), while with metal complex halides X-ML(n) (ML(n) = AuPR3, AgPPh2Tol, CuPR3 Cudppe, HgPh) the hetero-binuclear complexes mer-(CO)3(R3'P)(R3Si) Fe-ML(n) are obtained, which contain unbridged metal-metal bonds. Upon reaction of [Fe(CO)3(PR3')SiR3]- with HgBr2 in THF the trinuclear complexes [fac-(CO)3(R3'P)(R3Si)Fe]2Hg are obtained, from which the binuclear complexes mer-(CO)3(R3'P)-(R3Si)Fe-HgX are formed in toluene with a second equivalent of HgX2. X-Ray structure analyses of the octahedral complexes mer-(CO)3(Me3P)(Ph2MeSi)Fe-AuPPh2Tol (Fe-Au 252.7(3) pm), mer-(CO)3(Me3P)(Ph2MeSi)Fe-AgPh2Tol (Fe-Ag 258.1(1) pm) and mer-(CO)3(Me3P)-(Ph2MeSi)Fe-HgBr) (Fe-Hg 251.5(3) pm) show that the Fe-metal bond is cis to both the PMe3 and the SiMePh2 ligand. The comparison of the Fe-Si, Fe-P and Fe-M bond distances indicates that the polarity of the Fe-M bond increases from M = Hg and M = Au to M = Ag. The Fe-Hg compound is loosely dimerized via unsymmetrical Br bridges (Hg-Br 253.5(3) and 306.3(1) pm).