Dimolybdenum complexes containing bridging acetate ligands and anions of N, N′-di(2-methoxyphenyl)formamidine

Abstract

The syntheses, structures and NMR spectra of quadruply bonded complexes containing three, two or one bridging acetate ligands and anions of N, N′-di(2-methoxyphenyl)formamidine ( o-HDMophF), of the types Mo 2(O 2CCH 3) 3( o-DMophF) ( 1), trans-Mo 2(O 2CR) 2( o-DMophF) 2 (R=CH 3, 2; CF 3, 3; Pr n, 4) and Mo 2(O 2CCH 3)( o-DMophF)Cl 2(PMe 3) 2 ( 5), are discussed. Complex 1 was prepared by reaction of Mo 2(O 2CCH 3) 4 with excess o-HDMophF in THF. The reactions of Mo 2(O 2CCH 3) 4 and Mo 2(O 2CPr n) 4 with excess lithiated formamidine afforded complexes 2 and 4, respectively. Complex 3 was prepared by reaction of Mo 2(O 2CCF 3) 4 with o-HDMophF in THF and complex 5 was prepared by reaction of 1 with (CH 3) 3SiCl and PMe 3 in THF/CH 2Cl 2. Their UV–Vis and NMR spectra have been recorded and their structures have been determined by X-ray crystallography. The o-DMophF − ligands show two different conformations, s- trans, s- trans and s- cis, s- trans, in compounds 1– 5. The study on 31P{ 1H} NMR spectrum of 5 concluded that the through metal–metal quadruple bonding coupling | 3 J PMoMoP| is about 16±1 Hz. The position of the monodentate phosphine ligand, i.e. cis or trans to the acetate or similar ligands, can be determined by evaluating the | 3 J CP| coupling constant.