Substitution and Oxidative Addition Reactions of the Monoolefin Complex Rh(acac)(cyclooctene)(PCy3) Including the X-ray Structure Analyses of Rh(acac)(PCy3)2 and [Rh(acac){(E)-CHCHCy}(PCy3)2]BF4

The olefin complex Rh(acac)(cyclooctene)(PCy 3 ) ( 2 ), which is formed from Rh(acac)(cyclooctene) 2 ( 1 ) and PCy 3 in nearly quantitative yield, reacts with CO and alkynes RC⋮CR by ligand displacement to give Rh(acac)(CO)(PCy 3 ) ( 3 ) and Rh(acac)(η 2 -RC⋮CR)(PCy 3 ) [R = CO 2 Me ( 4 ), Ph ( 5 )], respectively. The bis(phosphine) compound Rh(acac)(PCy 3 ) 2 ( 6 ) cannot be prepared directly from 2 and excess PCy 3 but via Rh(acac)(η 2 -HC⋮CCO 2 Me)(PCy 3 ) ( 7 ) as intermediate. The X-ray crystal structure analysis of 6 reveals that the rhodium is coordinated in a distorted square-planar manner with O−Rh−O and P−Rh−P bond angles of 85.9(1) and 105.63(4)°. Compound 2 reacts with H 2 in the presence of PCy 3 to yield Rh(acac)H 2 (PCy 3 ) 2 ( 8 ) and with HC⋮CR/PCy 3 to give Rh(acac)H(C⋮CR)(PCy 3 ) 2 [R = Ph ( 9 ), Cy ( 10 ), SiMe 3 ( 11 )]. On treatment of 10 and 11 with HBF 4 ·OEt 2, the cationic alkenylrhodium(III) derivatives [Rh(acac){( E )-CH CHCy}(PCy 3 ) 2 ]BF 4 ( 12 ) and [Rh(acac)(CH CH 2 )(PCy 3 ) 2 ]BF 4 ( 13 ) are obtained. Labeling experiments using DBF 4 ·OEt 2 illustrate that the deuterium is found at the β-C carbon atom of the alkenyl ligand. Both 12 and [Rh(acac){( E )-CH CDCy}(PCy 3 ) 2 ]BF 4 ( 12 - d 1 ) react with NEt 3 to regenerate 10 . The structure of 12 was determined by X-ray analysis. The coordination geometry around the metal center can be rationalized as a square pyramid with the alkenyl group in the apical position.