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Chemical Bonding in Transition Metal Complexes with Beryllium Ligands [(PMe3)2M−BeCl2], [(PMe3)2M−BeClMe], and [(PMe3)2M−BeMe2] (M = Ni, Pd, Pt)

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journal contribution
posted on 26.08.2010, 00:00 by Pattiyil Parameswaran, Gernot Frenking
The equilibrium geometries and bond dissociation energies of the 14 valence electron (VE) complexes [(PMe3)2M−BeCl2], [(PMe3)2M−BeClMe], and [(PMe3)2M−BeMe2] with M = Ni, Pd, and Pt have been calculated using density functional theory at the BP86/TZ2P level. The nature of the M−Be bond was analyzed with the NBO charge decomposition analysis and the EDA energy decomposition analysis. The theoretical results predict the equilibrium structures with a T-shaped geometry at the transition metal where the PMe3 ligands are in the axial positions. The calculated bond dissociation energies show that the M−E bond strengths are in the range of donor−acceptor complexes of divalent beryllium compounds with ammonia. The bond strength decreases when the substituent at beryllium changes from Cl to CH3. The NBO analysis shows a negative charge at the BeX2 fragment, which indicates a net charge flow from the transition metal fragment to the beryllium fragment. The energy decomposition analysis of the M−Be bonds suggests two donor−acceptor bonds with σ and π symmetry where the transition metal fragment is a double donor with respect to the beryllium ligand. The π component of the [Ni]→BeXX′ donation is much smaller than the σ component.