We report the synthesis of 17 molybdenum and tungsten
complexes
supported by the ubiquitous BDI ligand framework (BDI = β-diketiminate).
The focal entry point is the synthesis of four molybdenum and tungsten(V)
BDI complexes of the general formula [MO(BDIR)Cl2] [M = Mo, R = Dipp (1); M = W, R = Dipp (2); M = Mo, R = Mes (3); M = W, R = Mes (4)] synthesized by the reaction between MoOCl3(THF)2or WOCl3(THF)2and LiBDIR. Reactivity studies show that the BDIDippcomplexes are
excellent precursors toward adduct formation, reacting smoothly with
dimethylaminopyridine (DMAP) and triethylphosphine oxide (OPEt3). No reaction with small phosphines has been observed, strongly
contrasting the chemistry of previously reported rhenium(V) complexes.
Additionally, the complexes1and2are
good precursors for salt metathesis reactions. While1can be chemically reduced to the first stable example of a Mo(IV)
BDI complex15, reduction of2resulted
in degradation of the BDI ligand via a nitrene transfer reaction,
leading to MAD (4-((2,6-diisopropylphenyl)imino)pent-2-enide) supported
tungsten(V) and tungsten(VI) complexes16and17. All reported complexes have been thoroughly studied by VT-NMR and
(heteronuclear) NMR spectroscopy, as well as UV–vis and EPR
spectroscopy, IR spectroscopy, and X-ray diffraction analysis.