CHEMISTRY OF THE ETA-1-RHENIUM-COORDINATE D TRIPHENYLCYCLOPROPENYL LIGAND

The sigma-coordinated pentacarbonyl(eta1-1,2,3-triphenylcyclopropenyl) rhenium complex 1 is transformed into the green acarbonyl(eta2-1,2,3- triphenylpropenetriyl)rhenium compound 2 with loss of CO by heating or irradiation. In addition, nyl(eta3-4-oxo-1,2,3-triphenylcyclobutenyl) rhenium (3a) and eta5-1,2,3,4,5,6-hexaphenylcyclohexadienyl)rhenium (4 ) were obtained from this reaction. Treatment of 1 with trimethylamine N-oxide leads under oxygen transfer to onyl(eta2-3-oxo-1,2,3-tripheny l-1-propenyl)rhenium (5) and ine)(eta2-3-oxo-1,2,3-triphenyl-1-propeny l)rhenium ( 6). The NMe3 ligand in 6 can be substituted either by CO o r trimethyl phosphite to yield 5 or tricarbonyl(trimethyl ite)(eta2-3- oxo-1,2,3-triphenyl-1-propenyl)rhenium (7), respectively. Complex 1 re acts with trimethylphoshane or trimethyl phosphite to give tetracarbon yl(phosphorus a1-4-oxo-1,2,3-triphenyl-2-cyclobuten-1-yl)rhenium 8b [L = PMe3] or 8c [L = P(OMe)3]. The derivatives Re(CO)3L2-eta1-C3Ph3CO [ L = CO, 8a; L = PMe3, 8d; L = P(OMe)3 8e] were obtained by treatment o f 3a with CO or two equivalents of PMe3 or P(OMe)3. The formation of 8 d and Be proceeded via the tricarbonyl(phosphorus or)(eta3-4-oxo-1,2,3 -triphenylcyclobutenyl)rhenium compounds 3b and 3c. The unusual eta1-c oordination of the cyclobutenone system in 8 was established by an X-r ay structure analysis of 8c. Furthermore, 4 and 5 were characterized b y single-crystal X-ray diffraction. Reactions of 2 with alkynes led to substituted tricarbonyl(cyclopentadienyl)rhenium derivatives Re(eta5- C5Ph3RR')(CO)3 9 (R = R' = Ph, 9a; R = R' = CO2Me, 9b; R = R' = CO2Et, 9c; R = Ph, R' = H, 9d).