Germylene and stannylene (Me2NCH2CH2O)2E as strong σ-donor ligands for transition metal complexes [ML(CO)n] (E = Ge, Sn; M = Cr, Mo, W, n = 4 or 5; M = Fe, n = 4). Synthesis, spectroscopic and theoretical study

A series of germylene and stannylene (Me2NCH2CH2O)2E (E = Ge, 1; E = Sn, 2) complexes of group 6 metals and iron carbonyls L·M(CO)n (M = Cr, Mo, W, n = 5 (3–8), n = 4 (9, 10); M = Fe, n = 4 (11, 12)) were prepared. These complexes were characterized by 1H, 13C NMR, FTIR and elemental analysis. Ligand properties of 1 and 2 were compared to PPh3 and dmiy (N,N′-dimethylimidazolin-2-ylidene) using theoretical calculations (PBE/TZ2P) and FTIR. Ligand dissociation energies increase in the order Ph3P < 2∼1 < dmiy, while donor strength rise in the order PPh3 < dmiy < 2 < 1.

Graphical abstractIt was shown using experimental and calculation data that germylene and stannylene (Me2NCH2CH2O)2E (E = Ge, Sn) are promising ligands for preparation of metal complexes. They (i) exhibit relatively high binding energies to transition metals, (ii) are very strong donors, stronger than imidazolium-based NHCs, and (iii) possess tunable steric properties.Figure optionsDownload full-size imageDownload as PowerPoint slide