Synthesis and structural characterisation of germanium(II) halide complexes with neutral N-donor ligands

Cheng, Fei, Dyke, John M., Ferrante, Francesco, Hector, Andrew L., Levason, William, Reid, Gillian, Webster, Michael and Zhang, Wenjian (2010) Synthesis and structural characterisation of germanium(II) halide complexes with neutral N-donor ligands. Dalton Transactions, 39 (3), 847-856. (doi:10.1039/b911016j).

Abstract

The Ge(II) complexes [GeX2(L–L)] (L–L = 1,10-phen (X = Cl, Br); L–L = Me2N(CH2)2NMe2, 2,2-bipy (X = Cl)), [GeX(L–L)][GeX3] (L–L = 2,2-bipy (X = Br); L–L = pmdta (MeN(CH2CH2NMe2)2) (X = Cl, Br)) have been prepared and their crystal structures determined. The crystal structure of [GeCl2{Me2N(CH2)2NMe2}] shows a weakly associated centrosymmetric dimer based upon distorted square-pyramidal coordination at Ge(II) and containing asymmetrically chelating diamine ligands. The structure of [GeCl2(2,2-bipy)] contains a chelating 2,2-bipy ligand and forms a zig-zag chain polymer via long-range intermolecular GeCl bridging interactions, leading to a very distorted six-coordinate environment at Ge. [GeCl2(1,10-phen)] adopts a weakly associated dimeric structure similar to that in [GeCl2{Me2N(CH2)2NMe2}], whereas [GeBr2(1,10-phen)] is again a zig-zag polymer similar to [GeCl2(2,2-bipy)]. [GeBr(2,2-bipy)][GeBr3] contains a pyramidal cation with a chelating 2,2-bipy and a terminal Br ligand and with long-range contacts involving the three Br atoms in the anion. [GeX(pmdta)][GeX3] (X = Cl or Br) show discrete cations and anions, with no significant long-range interactions. The bonding in these systems can be described as covalent, with longer range interactions to other ligands involving the 4p orbitals of Ge. DFT calculations performed on [GeCl2(2,2-bipy)] show that the geometry of the monomer unit in the experimental crystal structure does not correspond to the global minimum of the isolated molecule, but to a higher energy minimum. In contrast, the calculated structure of the tetramer shows some of the main structural characteristics observed in the crystal structure.

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Contributors

Author: John M. Dyke

Author: Andrew L. Hector

Author: William Levason

Author: Gillian Reid

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