Ditantalum Hydride Complexes with Bridging (2,6-iPr2C6H3)NSiHPh Silanimine Ligands Resulting from PhSiH3−Imido Ligand Coupling. A Combined Spectroscopic and Theoretical Investigation

Abstract

The preparation and characterization of two novel dinuclear tantalum hydride complexes featuring bridging silanimine ligands are reported. The reaction of Cp*(ArN)Ta[Si(SiMe3)3]H (Cp* = η5-C5Me5; Ar = 2,6-iPr2C6H3) with PhSiH3 resulted in formation of [Cp*(ArN)TaH(μ-H)]2 (4% yield), yellow, paramagnetic Cp*2(ArN)Ta2H2(μ-ArNSiHPh) (1, 18% yield), and dark green, diamagnetic Cp*2Ta2H2(μ-ArNSiHPh)2 (2, 71% yield). For 1 and 2, X-ray structure determinations characterize the ArNSiHPh silanimine ligand as possessing a Si−N single bond. This is confirmed by molecular orbital calculations that provide an average bond order of 0.7 for the Si−N bond. The ArNSiHPh fragment is therefore best viewed as a bifunctional silyl−amido ligand. For diamagnetic complex 2, the X-ray analysis revealed a molecular structure possessing nearly exact 2-fold symmetry (the hydride ligands were not located), while NMR spectroscopy indicates that the two Cp*Ta(μ-ArNSiHPh) fragments in the molecule are chemically inequivalent. To analyz...