Probing Structural Diversity in a Series of Perhydrocarbyl Heterobimetallic Complexes Associating Tantalum and 3d (Cr, Mn, Fe, Co, Ni) Transition Metals.

Salt metathesis between an alkali-stabilized tantalate complex, [Li(thf)2][Ta(CtBu)(CH2tBu)3] (1), and a series of alkylcyclopentadienyl 3d transition metal halide dimers, [Cp'M(μ-X)]2 (2-MX, Cp' = 1,2,4-tBu3C5H2, X = Cl, Br or I), provides a set of perhydrocarbyl-stabilized heterobimetallic complexes [Ta(CH2tBu)2(μ-CHtBu)2MCp']/[Ta(CH2tBu)3(μ-CtBu)MCp'] (3-M, M = Cr, Mn, Fe, Co, Ni). A combination of single-crystal X-ray diffraction, spectroscopic studies and computational investigations reveals that the species 3-M make up a series of nearly isostructural molecules, some of which exhibit unusual coordination geometries and an atypical α-hydrogen tautomerism. Most of these Ta-M pairs are rare or unprecedented in bimetallic molecular compounds and were designed as potential alternatives to analogous compounds in which tantalum is combined with more costly, heavy transition metals such as iridium or osmium, recently reported to be suitable precursors for Surface OrganoMetallic Chemistry (SOMC) and catalytic H/D exchange reactions.