Organoimido complexes of tungsten and rhenium: Oxo-imido and bis-imido complexes of tungsten(VI), and phenylimido complexes of rhenium(VI) and (V). The X-ray crystal structures of [W(NCMe3)(NPh)Cl2(bipy)] and [Re(NPh)Cl3(NH2CMe3)2

Abstract

Reaction of Me3CNH2 or Me3SiNHCMe3 with WOCl4 gives a mixture containing [W(O)(NCMe3)Cl2(NH2CMe3)]x which on further reaction with 2,2′-bipyridyl (bipy) gives [W(NCMe3)2Cl2(bipy)] and insoluble oxo complexes. Reaction of WOCl4 with p-MeC6H4N(SiMe3)2 and then bipy gives [W(NC6H4Me-p)2Cl2(bipy)] and [W(O)(NC6H4Me-p)Cl2(bipy)]; [W(NPh)Cl4]2 reacts with p-MeC6H4N(SiMe3)2 and then bipy to give [W(NPh)(NC6H4Me-p)Cl2(bipy)]. [W(NCMe3)(μ-NPh)Cl2(NH2CMe3)]2 and bipy give [W(NCMe3)(NPh)Cl2(bipy)] (6). ReOCl4 reacts with PhNCO to give [Re(NPh)Cl4]x which in tetrahydrofuran (THF) or MeCN give the adducts [Re(NPh)Cl4(THF)] and [Re(NPh)Cl4(MeCN)]. [Re(NPh)Cl4]x reacts with Me4NCl to give [Me4N][Re(NPh)Cl5], with PPh3 to give [Re(NPh)Cl3(PPh3)2] and with Me3 SiNHCMe3 gives [Re(NPh)Cl3(NH2CMe3)2] (12). The complexes were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. The structures of [W(NCMe3)(NPh)Cl2(bipy)] (6) and [Re(NPh)Cl3(NH2CMe3)2] (12) were determined by single-crystal X-ray diffraction methods. Crystals of (6) are orthorhombic, space group P212121, with a = 8.879(3) Å, b = 13.036(3) Å, c = 18.837(4) Å; crystals of (12) are orthorhombic, space group Pbcn with a = 14.140(1) Å, b = 11.806(1), Å, c = 11.936(3) Å. Both structures were solved by Patterson and Fourier methods and refined to R values of 0.053 for the 2138 observed data for (6) and 0.035 for the 1108 observed data for (12). In complex (6) the tungsten atom is in a distorted octahedral environment comprising cis-t-butylimido and phenylimido groups, trans chlorides and bidentate bipy. The bipy nitrogens lie trans to the imid o functions. Observed distances are: WNphenylimido 1.774(8) Å, WNt-butylimido 1.754(10) Å, WCl 2.412(3) and 2.390(3) Å and WNbipy 2.312(10) Å and 2.333(9) Å. Interaction between the t-butylimido methyl groups and bipy is relieved by lengthening of one WNbipy bond. In complex (12) the rhenium atom is in a distorted octahedral environment comprising three chloride ligands, two trans-t-butylamine ligands and a phenylimido ligand. Observed distances are: ReNphenylimido 1.709(11) Å, ReNt-butylamine 2.187(7) Å, and ReCl 2.404(2) and 2.411(5) Å. The complex attains an 18-electron count without π-bonding from the chloro ligands.