Übergangsmetall-carbin-komplexe XCVII. Carbonylhaltige und carbonylfreie diethylaminocarbin-komplexe von wolfram in einer höheren oxidationszahl mit trimethylphosphit- und isonitril-liganden

Abstract

I(CO) 2(py) 2WCNEt 2 ( 1) contains two substitutionally labile pyridine ligands and is, therefore, a useful precursor for the synthesis of substituted diethylaminocarbyne complexes. Thus, its reaction with P(OMe) 3 leads to an isomeric mixture of cis and trans I(CO) 2[P(OMe) 3] 2WCNEt 2 ( 2a, 2b). The complexes 2a and 2b can be separated by column chromatography on silica at low temperature. An isomerization of 2a and 2b occurs at room temperature in CH 2Cl 2 or Et 2O leading to a thermodynamic equilibrium, which favours the trans complex. 2a and 2b can be oxidatively decarbonylated by iodine to give the seven-coordinated, carbonyl containing, high-valent tungsten carbyne complex (I) 3(CO)[P(OMe) 3] 2WCNEt 2 ( 3). In comparison, the tri-isonitrile substituted carbyne complexes I(CO)(RNC) 3WCNEt 2 ( 4: R = Me; 5: R = t-Bu), which can be obtained from I(CO) 2(RNC) 2WCNEt 2 and RNC by thermal decarbonylation, react with iodine to give the seven-coordinated, carbonyl-free, high-valent tungsten carbyne complexes (I) 3(RNC) 3WCNEt 2 ( 6: R = Me; 7: R = t-Bu). 6 and 7 react with RNC by displacement of one iodide ligand from the coordination sphere to yield the cationic compounds [(I) 2(RNC) 4WCNEt 2] +I − ( 8: R = Me; 9: R = t-Bu). The composition and structure of the complexes have been determined by elemental analyses, IR, 1H NMR, 13C NMR, 31P NMR and mass spectroscopy.