Inorganic Chemistry, Vol.53, No.19, 10403-10411, 2014
Hume-Rothery Phase-Inspired Metal-Rich Molecules: Cluster Expansion of [Ni(ZnMe)(6)(ZnCp*)(2)] by Face Capping with Ni-0(eta(6)-toluene) and Ni-I(eta(5)-Cp*)
The novel all-hydrocarbon ligand-stabilized binuclear clusters of metal-core composition Ni2Zn7E, [(eta(5)-Cp*)-Ni-2(ZnMe)(6)(ZnCp*)(ECp*)] (1-Zn, E = Zn; 1-Ga, E = Ga) and [(eta(6)-toluene)Ni-2(ZnCp*)(2)(ZnMe)(6)] (2; Cp* = pentamethylcyclopentadienyl), were obtained via Ga/Zn and Al/Zn exchange reactions using the starting compounds [Ni-2(ECp*)(3)(eta(2)-C2H4)(2)] (E = Al/Ga) and an excess of ZnMe2 (Me = CH3). Compounds 1-Zn and 1-Ga are very closely related and differ only by one Zn or Ga atom in the group 12/13 metal shell (Zn/Ga) around the two Ni centers. Accordingly, 1-Zn is EPR-active and 1-Ga is EPR-silent. The compounds were derived as a crystalline product mixture. All new compounds were characterized by H-1 and C-13 NMR and electron paramagnetic resonance (EPR) spectroscopy, mass spectrometric analysis using liquid-injection field desorption ionization, and elemental analysis, and their molecular structures were determined by single-crystal X-ray diffraction studies. In addition, the electronic structure has been investigated by DFT and QTAIM calculations, which suggest that there is a Ni1-Ni2 binding interaction. Similar to Zn-rich intermetallic phases of the Hume-Rothery type, the transition metals (here Ni) are distributed in a matrix of Zn atoms to yield highly Zn-coordinated environments. The organic residues, ancillary ligands (Me, Cp*, and toluene), can be viewed as the "protecting" shell of the 10-metal-atom core structures. The soft and flexible binding properties of Cp* and transferability of Me substituents between groups 12 and 13 are essential for the success of this precedence-less type of cluster formation reaction.