Molecular Mimics of Intermetallic Phases: Selective Alkylamide-Ligand Deprotection Drives Co/Ga Cluster Formation.

The heterobimetallic M14 cluster [Co3Ga2]H(μ2-GaTMP)9 (1, TMP = 2,2,6,6-tetramethylpiperidinyl) was obtained by treating CoCl2 with GaTMP in the presence of Mg and H2 as reduction additives. 1 features a trigonal bipyramidal Co3Ga2 kernel with one substituent-free Ga atom and one exposed GaH moiety inside a metallo-environment of nine edge-bridging GaTMP ligands. The resulting Co3Ga11 cluster core mimics a packing motif of the structurally related intermetallic phase Co2Al5. The GaTMP ligands not only donate their lone pairs to the Co, but also to the exposed, bare Ga of the Co3Ga2 kernel, thus contributing to the increase in delocalization over the M14 core, according to bonding analysis. The synthesis of 1 represents proof-of-concept to steer the coordination of GaTMP to transition metal centers toward a kernel-alloyed Co/Ga cluster formation. This is rationalized by Mg/H2-induced Ga deprotection and TMP-trapping in the Hauser-base complex [Mg(TMP)(THF)μ2Cl]2. The method bears potential for generalization, and first results were obtained for related Fe/Ga clusters.