Synthesis and reactivity of tris(imido)rhenium complexes containing rhenium-main group element bonds.: Silicon-carbon bond activations of PhSiH3 by silyl complexes

The synthesis and reactivity of a series of complexes of the (DippN=)(3)Re (Dipp = 2,6-(Pr2C6H3)-Pr-i) fragment are reported, The anionic, Re(V) complex (THF)(2)Li(mu,mu-NDiPP)(2)Re( NDipp) (1), prepared by the reaction of (DippN=)(3)ReCl with (THF)(3)LiSi(SiMe3)(3) or 'BuLi (2 equiv) in the presence of THF (4 equiv), served as an important starting material for the synthesis of rhenium-element-bonded complexes. For example, treatment of 1 with ClSiR3 gave the corresponding silyl complexes (DippN=)(3)ReSiR3 (SiR3 = SiMe3 (2a), SiHPh2 (2b), SiH2Ph (2c)). Complexes 2a-c are thought to exist in equilibrium between the Re(VII) (DippN=)(3)ReSiR3 and Re(V) (DippN=)(2)ReN(SiR3)-Dipp isomers. Complexes 2a,b reacted with PhSiH3 to give reaction mixtures that included 2c, Ph2SiH2, SiH4, and C6H6. The silane and organic products arise from Si-C bond formation and cleavage. Treatment of 2a with CO gave (DippN=)(2)Re[N(SiMe3)Dipp](CO) (3), which appears to result from trapping of the reactive Re(V) isomer of 2a by CO. Complex 1 reacted with the main group halides Mel, Ph3GeCl, Me3SnCl, Ph2PCl, and PhSeCl to give the corresponding rhenium complexes (DippN=)(3)ReERn (ERn = Me (4), GePh3 (5), SnMe3 (6), PPh2 (7), SePh (8)) in high yields. X-ray diffraction data for 5 indicate that the germyl ligand is bonded to rhenium, but positional disorder of the phenyl and Dipp groups prevented refinement of accurate metric parameters.