THERMALLY STABLE ARYLTUNGSTEN(VI) OXO AND PHENYLIMIDO COMPLEXES CONTAINING PHENYL LIGANDS WITH ORTHO-CHELATING TERTIARY AMINE SUBSTITUENTS - MOLECULAR-STRUCTURES OF W[(R)-C6H4CH(ME)NME2-2]CL3(=O) AND W(C6H4CH2NME2-2)CL2(=NPH)(OCME3)

Thermally stable aryltungsten(VI) oxo and phenylimido complexes have been synthesized using phenyl ligands with ortho-chelating CH2NMe2, CH(Me)NMe2, and CH2OMe substituents. By a combination of the stabilizing features of the ortho-chelating phenyl ligands with those of tert-butoxide ligands, aryltungsten(VI) phenylimido complexes have been obtained which are not only surprisingly thermally stable (up to at least 140-degrees-C) but also stable toward air and water. The solid-state structures of two of these complexes, W[(R)-C6H4CH(Me)NMe2-2]Cl3(=O) (1b) and W(C6H4CH2NMe2-2)Cl2(=NPh)(OCMe3) (5) have been investigated. Crystals of 1b are monoclinic, space group P2(1), with unit-cell dimensions a = 8.182(1) angstrom, b = 12.100(1) angstrom, c = 13.885(1) angstrom, beta = 90.04(1)-degrees, V = 1374.6(2) angstrom3, Z = 4, final R = 0.033, and R(w) = 0.041 for 4561 reflections with I > 2.5sigma(I) and 308 parameters. Crystals of 5 are monoclinic, space group P2(1)/n, with unit-cell dimensions a = 9.0035(5) angstrom, b = 25.182(1) angstrom, c = 9.3131(5) angstrom, beta = 97.621(4)-degrees, V = 2092.9(2) angstrom3, Z = 4, final R = 0.047, and R(w) = 0.040 for 2785 reflections with I > 2.5sigma(I) and 228 parameters. Both complexes are monomeric, octahedral species which are six-coordinated as a result of intramolecular amine coordination (in a trans position relative to the oxo group in 1b and the phenylimido group in 5). These aryltungsten(VI) complexes are six-coordinate in solution both at ambient and at elevated temperatures.