SYNTHESIS AND REACTIVITY OF EARLY-LATE HETERODINUCLEAR COMPLEXES STABILIZED BY A TRISILYLSILANE-BASED TRIPODAL AMIDO LIGAND

The reaction of the complexes [MeSi{SiMe2N(R)}3MX] (R ) p-tolyl, 2-FC6H4; M ) Ti, Zr, Hf; X ) Cl, Br) with K[CpM′(CO)2] afforded the metal-metal bonded heterodinuclear complexes [MeSi{SiMe2N(R)}3MM′(CO)2Cp] (M ) Ti, Zr, Hf; M′ ) Fe, Ru; R ) p-tolyl, 2-C6H4), all of which are thermally stable in the solid state and in solution. X-ray crystal structure analyses of the complexes [MeSi{SiMe2N(p-tol)}3M-M′(CO)2Cp] (M, M′: Ti, Fe (3); Ti, Ru (4); Zr, Fe (5)) and [MeSi{SiMe2N(2-FC6H4)}3Ti-Fe(CO)2Cp] (9) established the presence of unsupported metal-metal bonds [3, Ti-Fe 2.460(1); 4, Ti-Ru 2.5609(8); 5, Zr-Fe 2.605(2); 9, Ti-Fe 2.433(4) A]. Reaction of the dinuclear complexes with isonitriles led to insertion of the substrate into the polar metal-metal bond and the formation of the metallaiminoacyl complexes [MeSi{SiMe2N(R)}3M{η(CdNR′)M′(CO)2Cp}] (M ) Ti, Zr, Hf; M′ ) Fe, Ru; R ) p-tolyl, 2-C6H4; R′ ) Me, p-tolyl). The 13C NMR resonances of the isonitrile-derived carbon nuclei linking the two metal centers are observed at remarkably low field (δ 267.8-303.8). The structural proposal for the insertion products was confirmed by an X-ray crystallographic study of [MeSi{SiMe2N(p-tol)}3Ti{η-(CdNMe)Ru(CO)2Cp]. When the heterobimetallic complex [MeSi{SiMe2N(p-tol)}3Zr-Ru(CO)2Cp] was reacted with sulfoxides [Me2SO, Me(Ph)SO, (PhCH2)2SO, (CH2)4SO], immediate oxygen transfer to a carbonyl ligand occurred, generating the dinuclear complexes [MeSi(SiMe2NTol)3Zr(μ-O2C)RuCp(CO){S(R)R′}] (R ) R′ ) Me (23a); R ) Me, R′ ) Ph (23b); R, R′ ) (CH2)4 (23c); R, R′ ) PhCH2 (23d)), in which the two metal centers are linked by a CO2 ligand derived from a carbonyl ligand in the starting material. In the presence of a second equivalent of sulfoxide, the Lewis acid-base adducts [MeSi(SiMe2NTol)3Zr{OS(R)R′-κO}(μ-O2C)RuCp(CO){S(R)R′}] (R ) R′ ) Me (24a); R ) Me, R′ ) Ph (24b); R, R′ ) (CH2)4 (24c)) were formed. An X-ray crystal structure analysis of 24a established the conversion of the carbonyl ligand to the bridging matallacarboxylate unit and the coordination of the thioether, formed in the oxygen transfer, to the Ru atom. The oxygen transfer from the sulfoxide to a carbonyl ligand was confirmed by an NMR study of the reaction using 13C-labeled carbonyl derivatives and 17O-labeled Me(Ph)SO.