Ligand dependent topology and spontaneous resolution in high-spin cyano-bridged Ni3W2 clusters

Abstract

Two high-spin pentanuclear Ni^II₃W^V₂ clusters with diimine blocking ligands have been obtained: {[Ni(4,4′-MeObpy)₂]₃[W(CN)₈]₂}·12H₂O (1) and {[Ni(phen)₂(H₂O)][Ni(phen)₂]₂[W(CN)₈]₂}·7H₂O (2) (4,4′-MeObpy = 4,4′-dimethoxy-2,2′-bipyridine, phen = 1,10-phenanthroline). Despite the similarity of the building blocks and synthetic conditions the compounds show different topologies of the cluster core: 1 is a trigonal bipyramid while 2 is a decorated square. Both cluster structures are chiral with either ΔΔΔ or ΛΛΛ configuration around all three Ni centres. In 1 spontaneous resolution occurs and it crystallises in the P2₁2₁2₁ space group forming a conglomerate containing both types of enantiomorphic crystals. 1Δ and 1Λ are the first pair of enantiomorphic structures of cyano-bridged clusters of trigonal bipyramidal topology obtained with achiral bidentate blocking ligands. 2 crystallises as a racemic compound in a centrosymmetric space group P with both enantiomers present in the structure. 2 is an exceptional square-motif containing structure with an identical stereoconfiguration of all complex cations within one cluster. Ferromagnetic interactions are present in both clusters resulting in the ground spin state S = 4.