SUBSTITUTION AND OXIDATIVE ADDITION-REACTIONS OF THE MONOOLEFIN COMPLEX RH(ACAC)(CYCLOOCTENE)(PCY(3)) INCLUDING THE X-RAY STRUCTURE ANALYSES OF RH(ACAC)(PCY(3))(2) AND [RH(ACAC)((E)-CH=CHCY)(PCY(3))(2)]BF4

The olefin complex Rh(acac)(cyclooctene)(PCy(3)) (2), which is formed from Rh(acac)(cyclooctene)(2) (1) PCy(3) in nearly quantitative yield, reacts with CO and alkynes RC=CR by ligand displacement to give Rh(ac ac)(CO)(PCy(3)) (3) and Rh(acac)(eta(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)(eta(2)-HC=CCO(2)Me)(PCy(3)) (7) as intermediate. The X-ray cryst al 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)degrees. Compound 2 reacts with H-2 in the prese nce 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 HBF4 . OEt(2), the cationic alkenylrh odium(III) derivatives [Rh(acac){(E)-CH=CHCy}(PCy(3))(2)]BF4 (12) and [Rh(acac)(CH=CH2)(PCy(3))(2)]BF4 (13) are obtained. Labeling experimen ts using DBF4 . OEt(2) illustrate that the deuterium is found at the b eta-C carbon atom of the alkenyl ligand. Both 12 and [Rh(acac){(E)-CH= CDCy}(PCy(3))(2)]BF4 (12-d(1)) react with NEt(3) to regenerate 10. The structure of 12 was determined by X-ray analysis. The coordination ge ometry around the metal center can be rationalized as a square pyramid with the alkenyl group in the apical position.