1st Row Transition Metal Aluminylene Complexes: Preparation, Properties and Bonding Analysis

Abstract

<i>The synthesis and spectroscopic characterisation of eight new first-row transition metal (M = Cr, Mn, Fe, Co, Cu) aluminylene complexes is reported. DFT and ab<b> </b>initio calculations have been used to provide detailed insight into the metal–metal bond. The σ-donation and π-backdonation properties of the aluminylene ligand are evaluated via NBO and ETS-NOCV calculations. These calculations reveal that these ligands are strong σ-donors but also competent π-acceptors. These properties are not fixed but vary in response to the nature of the transition metal centre, suggesting that aluminylene fragments can modulate their bonding to accommodate both electron-rich and electron-poor transition metals. Ab initio<b> </b>DLPNO-CCSD(T) calculations show that dispersion plays an important role in stabilising these complexes. Both short-range and long-range dispersion interactions are identified. These results will likely inform the design of next-generation catalysts based on aluminium metalloligands. </i>

Cooperative C–H Bond Activation by a Low-Spin d6 Iron–Aluminium Complex

“…Such short Fe---Al bond lengths appear to be diagnostic for an aluminylene 27 metalloligand covalently bound to iron. 28 Based on the experimental data it is evident that 2a-b and 3a-b are low-spin and diamagnetic 18 valence electron complexes. While 2a-b can be confidently described as σ-alane 29 complexes, three extreme bonding scenarios 16 More insight into the structure and bonding in these complexes was gained by DFT calculations and the optimised structure of 3b is depicted in Figure 2c.…”