Molybdenum(VI) bis(imidoaryl) complexes containing the bis(aminomethyl)aryl "Pincer" ligand [C6H3(CH2NMe2)2-2,6]- (NCN):: Structures of [MoCl(η2-C,N-NCN)(NAr)2], [Mo(η2-C,N-NCN)(Me)(NAr)2], and [MoCl2{η2-C,N-NC(NH)}(NAr)2]

The synthesis and characterization of new, five-coordinate molybdenum bis(imido) chloride complexes [MoCl(NCN)(N-t-Bu)(2)] (2) and [MoCl(eta(2)-C,N-NCN)(NAr)] (3) and the methylated derivative [Mo(eta(2)-G,N-NCN)(Me)(NAr)(2)] (5) (NCN = [C6H3(CH2NMe2)(2)-2,6](-), Ar = C6H3-i Pr-2-2,6) are reported. Compounds 3 and 5 react with HCl to yield the corresponding airstable salts [MoCl2{C6H3(CH2NMe2)-2-(CH2NHMe2)-6}(NAr (4) and [MoCl{C6H3(CH2NMe2)-2-(CH2NHMe2)-6}(Me)(NAr)(2)] (6), respectively,of which 3-5 have been characterized by X-ray analysis. X-ray structure determination of 4 shows an additional chloride anion bonded to the molybdenum metal center while one of the ortho-(dimethylamino;)methyl substituents of the NCN ligand has been selectively protonated. This proton is hydrogen bonded to one of the chloride ligands (N-H...CL 16612 degrees; H...Cl 1.94 Angstrom). Because the spectroscopic data (NMR, IR) of 6 are very similar to those found for 4, complex 6 is believed to have structural characteristics (both in solution and in the solid state) similar to 4. The proton bn the ortho-(dimethylamino)methyl group of the NCN ligand in 4 and 6 reacts immediately with an alkyl-Grignard or lithium reagents with formation of the corresponding alkane, the magnesium or lithium salt, and 3 and. 5, respectively. Further reactions of 2,4, and 6 with an excess of HCl, aimed at cleaving one of the imido groups, yielded unidentifiable reaction mixtures instead.