Nature of M–Ge Bonds in the Metallogermylene Complexes of Chromium, Molybdenum, and Tungsten [(η⁵‑C₅H₅)(CO)₃M{GeN(SiMe₃)R}] and [(η⁵‑C₅H₅)(CO)₃M{GeN(Ph)R}] (R = Ph, Mesityl (Mes)): A Theoretical Study

Abstract

Geometry and bond energy analysis of M–Ge bonds in the terminal metallogermylenes of chromium, molybdenum, and tungsten [(η5-C5H5)­(CO)3M­{GeN­(SiMe3)­R}] and [(η5-C5H5)­(CO)3M­{GeN­(Ph)­R}] (R = Ph, mesityl (Mes)) were investigated by DFT methods (BP86, PBE, and PW91) and the DFT-D3_BJ level of theory. The calculated geometric parameters of the molybdenum–aminogermylene complexes are in excellent agreement with the available experimental values. The M–Ge bonds in these complexes are essentially M–Ge single bonds. The optimized Ge–N bond distances are slightly smaller than those expected for a single bond on the basis of covalent radii predictions. The bent coordination geometries at germanium (M–Ge–N bond angles in the range 115.3–118.5°) in these complexes are consistent with the presence of a divalent Ge­(II) atom, which is singly bonded to a transition metal and the nitrogen of the NRR′ groups. In all studied complexes, the π-bonding contributions to the total M–Ge bonds are significantly smaller (∼17–18%) than the corresponding σ-bonding contributions and they decrease upon going from M = Cr to M = W. The contributions of the electrostatic interaction ΔEelstat to the M–Ge bonds are larger than the covalent bonding components, ΔEorb. The DFT-D3 dispersion corrections to the BDEs between the metal fragments [(η5-C5H5)­(CO)3M]− and ligand fragments [GeN­(SiMe3)­R]+ for the PBE functional are in the range 5.9–8.4 kcal/mol, which are smaller than the corresponding DFT-D3­(BJ) dispersion corrections (8.1–9.9 kcal/mol)