Chemie des η 1 ‐Rhenium‐koordinierten Triphenylcyclopropenyl‐Liganden

Chemistry of the η 1 ‐Rhenium‐Coordinated Triphenylcyclopropenyl Ligand The s̀‐coordinated pentacarbonyl[η 1 ‐1,2,3‐triphenylcyclopropenyl)rhenium complex 1 is transformed into the green tetracarbonyl(η 2 ‐1,2,3‐triphenylpropenetriyl)rhenium compound 2 with loss of CO by heating or irradiation. In addition, tetracarbonyl(η 3 ‐4‐oxo‐1,2,3‐triphenylcyclobutenyl)rhenium ( 3a ) and Tricarbonyl(η 5 ‐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 tetracarbonyl(η 2 ‐3‐oxo‐1,2,3‐triphenyl‐1‐propenyl)rhenium ( 5 ) and tricarbonyl(trimethylamine)(η 2 ‐3‐oxo‐1,2,3‐triphenyl‐1‐propenyl)rhenium ( 6 ). The NMe 3 ligand in 6 can be substituted either by CO or trimethyl phosphite to yield 5 or tricarbonyl‐(trimethyl phosphite)(η 2 ‐oxo‐1,2,3‐triphenyl‐1‐propenyl)‐rhenium ( 7 ), respectively. Complex 1 reacts with trimethyl‐phosphane or trimethyl phosphite to give tetracarbonyl(phosphorus donor)(η 1 ‐4‐oxo‐1,2,3‐triphenyl‐2‐cyclobuten‐1‐yl)rhenium 8b [L = PMe 3 ] or 8c [L = P(OMe) 3 ]. The derivatives Re(CO) 3 L 2 ‐η 1 ‐C 3 Ph 3 CO [L = CO, 8a ; L = PMe 3 , 8d ; L = P(O‐Me) 3 8e ] were obtained by treatment of 3a with CO or two equivalents of PMe 3 or P(OMe) 3 . The formation of 8d and 8e proceeded via the tricarbonyl(phosphorus donor)(η 3 ‐4‐oxo‐1,2,3‐triphenylcyclobutenyl)rhenium compounds 3b and 3c . The unusual η 1 ‐coordination of the cyclobutenone system in 8 was established by an X‐ray structure analysis of 8c . Furthermore, 4 and 5 were characterized by single‐crystal X‐ray diffraction. Reactions of 2 with alkynes led to substituted tricarbonyl(cyclopentadienyl)rhenium derivatives Re(η 5 ‐C 5 Ph 3 RR')(CO) 3 9 (R = R' = Ph, 9a ; R = R' = CO 2 Me, 9b ; R = R' = CO 2 Et, 9c ; R = Ph, R' = H, 9d ).