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 Mo-2(O2CCH3)(3)(o-DMophF) (1), trans-Mo-2(O2CR)(2)(o-DMophF)(2)(R=CH3,2; CF3, 3; Pr-n, 4) and Mo-2(O2CCH3)(o-DMophF)Cl-2(PMe3)(2) (5), are discussed. Complex 1 was prepared by reaction of Mo-2(O2CCH3)(4) with excess o-HDMophF in THF. The reactions of Mo-2(O2CCH3)(4) and MO2(O2CPrn)(4) with excess lithiated formamidine afforded complexes 2 and 4, respectively. Complex 3 was prepared by reaction of Mo-2(O2CCF3)(4) with o-HDMophF in THF and complex 5 was prepared by reaction of 1 with (CH3)(3)SiCl 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 P-31{H-1} 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. (C) 2002 Elsevier Science B.V. All rights reserved.