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.