title: 'Pincer' dicarbene complexes of some early transition metals and uranium.
abstract: The complexes [(C-N-C)MX(n)(thf)(m)] with the 'pincer' 2,6-bis(imidazolylidene)pyridine, (C-N-C) = 2,6-bis(arylimidazol-2-ylidene)pyridine, aryl = 2,6-Pr(i)2C6H3, M = V, X = Cl, n = 2, m = 1 1a; M = Cr, X = Cl, n = 2, m = 0, 2a, X = Br, 2b; M = Mn, X = Br, n = 2, m = 0, 3; M = Nb, X = Cl, n = 3, m = 0, 4; and M = U, X = Cl, n = 4, m = 0, 5, were synthesised by (a) substitution of labile tmed (1a), thf (2a, 3, 5) or dme (4) by free (C-N-C) or by (b) reaction of the bisimidazolium salt (CH-N-CH)Br2 with {Cr[N(SiMe3)2]2(thf)2} followed by amine elimination (2b). Attempted alkylation of 1a, 2, 3a and 4 with Grignard or alkyl lithiums gave intractable mixtures, and in one case [reaction of 1a with (mesityl)MgBr] resulted in exchange of Cl by Br (1b). Oxidation of 1a or [(C-N-C)VCl3] with 4-methylmorpholine N-oxide afforded the trans-V(C-N-C)(=O)Cl2, 6, which by reaction with AgBF4 in MeCN gave trans-[V(C-N-C)(=O)(MeCN)2][BF4]2, 7. Reaction of 1a with p-tolyl azide gave trans-V(C-N-C)(=N-p-tolyl)Cl2 8. The complex trans-Ti(C-N-C)(=NBu(t))Cl2, 9, was prepared by substitution of the pyridine ligands in Ti(NBu(t))Cl2(py)3 by C-N-C.
authors.affiliation: School of Chemistry, University of Southampton, Highfield, Southampton, UK SO17 1BJ.
authors.forename: David
authors.initials: D
authors.lastname: Pugh
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Wright
authors.forename: Sandra
authors.initials: S
authors.lastname: Freeman
authors.forename: Andreas A
authors.initials: AA
authors.lastname: Danopoulos
mesh_terms: D002621:Chemistry / Q000379:methods*; D018360:Crystallography, X-Ray; D006859:Hydrogen / Q000737:chemistry; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry; D028561:Transition Elements / Q000737:chemistry*; D014501:Uranium / Q000737:chemistry*
chemical_list: D008024:Ligands; D008670:Metals; D028561:Transition Elements; D014501:Uranium; D006859:Hydrogen; D010100:Oxygen