"Nickel(II) Complexes with an Open Chain Tetradentate Nitrogen Arsenic Ligand"

The open-chain tetradentate ligand N,N′-bis(2-diphenyl-arsinoethyl)-N,N′-dimethylethylenediamine, (AsNNAs), forms four-coordinate nickel(II) complexes with the formulae [Ni(AsNNAs)]Y 2 (Y=ClO4, BPh4, BF4) and [Ni(AsNNAs)I]Y (Y=BPh4, I). Octahedral complexes of the general formula Ni(AsNNAs)Y2 are formed in the presence the more strongly coordinating anions, Y=Br, I, NCS, CH3COO/2, NO3/2. The octahedral complexes may dissociate in solution to give an equilibrium mixture containing also tetrahedral species. The coordinating behaviour of the ligand is compared with that of a ligand which has the same donor-atom set but a tripod structure, and with that of its phosphorous analogue PNNP.