Cyclopentadienyl substituted diethylaminocarbyne complexes of tungsten in a higher oxidation state

Abstract

The reaction of an equimolar mixture of (η 5-C 5H 5)(I) 2(CO)WCNEt 2 ( 1) and t-C 4H 9NC in THF at 50°C, results in the replacement of the CO ligand by isocyanide and formation of (η 5-C 5H 5)(I) 2( t-C 4H 9NC)WCNEt 2 ( 2). Complex 2 reacts further with t-C 4H 9NC in refluxing THF with displacement of the iodide ligand from the coordination sphere to give the cationic carbyne complex [(η 5-C 5H 5)(I)( t-C 4H 9NC) 2WCNEt 2] +I − ( 3). A new route to 2 in three steps has also been developed. The starting material, mer-I( t-C 4H 9NC) 3WCNEt 2 ( 4), is transformed with KC 5H 5 in refluxing THF to (η 5-C 5H 5)( t-C 4H 9NC)(CO)WECNEt 2 ( 5). Complex 5 is then oxidized with elemental iodine in CH 2Cl 2 to give [(η 5-C 5H 5)(I)( t-C 4H 9NC)(CO)WCNEt 2] +I − ( 6), the first cationic, carbonyl-containing carbyne complex of tungsten in a higher oxidation state. Finally, 6 is decarbonylated thermally in boiling THF to 20. The composition and structure of the new complexes 2, 3, 5 and 6 have been determined by total elemental analyses and IR, 1H NMR, 13C NMR spectroscopies, as well as by mass spectrometry. The non-ionic nature of 2 and ionic nature of 6 in solution, have been confirmed by conductivity measurements.