SYNTHESES AND STRUCTURES OF NICKEL(O) COMPLEXES CONTAINING THE METHYL-METHACRYLATE MONOMER AS LIGAND

The reaction of [Ni(eta(4)-C8H12)(2)] with the industrially important monomer methyl methacrylate. CH2=C(Me)CO(2)Me, in the presence of 1 or 2 mol equivalents of tricyclohexylphosphine leads to the formation of [Ni{eta(2)-CH2=C(Me)CO(2)Me}{P(C6H11)(3)}(2)] 1 and [Ni{eta(2)-CH2=C(Me)CO(2)Me}(2){P(C6H11)3}] 2, respectively. The crystal structures of 1 and 2 have been determined and reveal an eta(2)-CC mode of co-ordination of the methyl methacrylate ligands. with the CO(2)Me groups pendant and outside the nickel co-ordination sphere. Complexes 1 and 2 represent the first structurally characterised methyl methacrylate complexes; ? is formed as a mixture of meso and DL diastereomers in the ratio 2.34:1. Solution NMR studies indicate that the diastereomers interconvert rapidly. via an intramolecular mechanism, which is proposed to proceed via an 0-co-ordinated intermediate. Reaction of 1 with an excess of tert-butyl acrylate CH2=CHCO(2)Bu(t) yields [Ni(eta(2)-CH2=CHCO(2)Bu(t))(2){P(C6H11)(3)}] 4, which maybe prepared independently from [Ni(eta(4)-C8H12)(2)], P(C6H11)(3) and tert-butyl acrylate