SYNTHESIS AND REACTIONS OF (PI-ALLYL)BROMO-[HYDROTRIS(3, 5-DIMETHYLPYRAZOLYL)BORATO]RHODIUM(III)

Tp(Me2)Rh(coe)(MeCN) (1) (Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)bo rato, coe cyclooctene) has been found to readily undergo oxidative add ition of allyl bromide at room temperature to give Tp(Me2)Rh(sigma-all yl)Br(MeCN) (4). On prolonged reaction time or heating, complex 4 is c onverted to the pi-allyl complex Tp(Me2)Rh(pi-allyl)Br (5) with libera tion of MeCN. Complex 5 exhibits high reactivity toward MeMgBr and Li[ BHEt3], giving Tp(Me2)Rh(pi-allyl)Me (8) and Tp(Me2)Rh(pi-allyl)H (9), respectively. Deuterium-labeling experiments using Li[BDEt3] indicate that complex 9 is formed mainly by nucleophilic addition of H- to the central carbon of the pi-allyl Ligand, followed by beta-hydrogen elim ination of the resultant rhodacyclobutane intermediate. Complex 9 reac ts with a variety of alkyl bromides by a radical process to afford 5 a nd alkanes.