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

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 Mo2(O2CCH3)3(o-DMophF) (1), trans-Mo2(O2CR)2(o-DMophF)2 (R=CH3, 2; CF3, 3; Prn, 4) and Mo2(O2CCH3)(o-DMophF)Cl2(PMe3)2 (5), are discussed. Complex 1 was prepared by reaction of Mo2(O2CCH3)4 with excess o-HDMophF in THF. The reactions of Mo2(O2CCH3)4 and Mo2(O2CPrn)4 with excess lithiated formamidine afforded complexes 2 and 4, respectively. Complex 3 was prepared by reaction of Mo2(O2CCF3)4 with o-HDMophF in THF and complex 5 was prepared by reaction of 1 with (CH3)3SiCl and PMe3 in THF/CH2Cl2. 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 |3JP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 |3JCP| coupling constant.