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Molybdenum (VI) Bis(imidoaryl) Complexes Containing the Bis (amonimethyl)aryl 'Pincer' Ligand

By G. van Koten, J.A.M. Brandts, R.A. Gossage, J. Boersma and A.L. Spek

Abstract

The synthesis and characterization of new, five-coordinate molybdenum bis(imido) chloride complexes [MoCl(NCN)(N-t-Bu)2] (2) and [MoCl(2-C,N-NCN)(NAr)2] (3) and the methylated derivative [Mo(2-C,N-NCN)(Me)(NAr)2] (5) (NCN = [C6H3(CH2NMe2)2-2,6]-, Ar = C6H3-i-Pr2-2,6) are reported. Compounds 3 and 5 react with HCl to yield the corresponding air-stable salts [MoCl2{C6H3(CH2NMe2)-2-(CH2NHMe2)-6}(NAr)2] (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 166.2; H···Cl 1.94 Å). 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 on 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

Topics: Scheikunde
Year: 1999
OAI identifier: oai:dspace.library.uu.nl:1874/6328
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