Homoleptic molybdenum complexes of α,β-unsaturated amides and esters: preparation and crystal structures

Abstract

Bis(η⁶-toluene)molybdenum reacted with N,N-dimethylacrylamide and methyl methacrylate under mild conditions with exchange of both arene ligands to yield the new homoleptic tris(1-oxa-1,3-diene)molybdenum complexes [Mo{H₂CCHC(O)NMe₂}₃] and [Mo{H₂CC(Me)C(O)OMe}₃] in 84 and 50% yield, respectively. The yellow, crystalline compounds exhibit three-fold symmetry in solution (¹H and ¹³C NMR spectra) and also in the solid state (crystal structure analyses). The ligand bonding is best described as intermediate between η⁴ and κ²,η² co-ordination. For the first time in the tris(oxadiene) complex series, a non-symmetrical isomer can be isolated in low yield from the crude product mixture of the ester complexation reaction and has been characterised spectroscopically.