Synthesis and characterization of a new nonanuclear Ni(ii) cluster from a pyridyl-alcohol ligand

Abstract

The reaction of one equivalent of 2-methyl-1-(pyridin-2-yl)propan-2-ol (HL) with two equivalents of [Ni(OAc)₂·4H₂O] in methanol afforded the nonanuclear coordination cluster [Ni₉(HL-κ²N,O)₄(OAc-κ²O)₂(μ₂-OAc-κ¹O)₂(μ₂-OAc-κ²O,O′)₄(μ₃-OAc-κ²O;κ²O,O′)₂(μ₃-OMe)₈] (1). All nickel ions are hexacoordinated and show a slightly distorted octahedral coordination geometry. This unusual centrosymmetric coordination cluster can be described as constituted by two cubane moieties connected by a linker comprising a nickel atom, situated on the inversion centre, four bridging acetates and two triply-bridging acetates. Each cubane contains four Ni(II) centres and four triply-bridging methoxide anions, two of the Ni(II) centres are N,O-chelated by the ligand HL, another Ni(II) is chelated by an acetate ligand and the fourth Ni(II) centre is connected to the exo-cubane Ni(II) through three acetate ligands which each have a different bonding mode: μ₂-κ²O,O′, μ₂-κ¹O, and μ₃-κ¹O;κ²O,O′. The magnetic and catalytic properties for ethylene oligomerization of the unusual complex 1 have been investigated.