Step-by-step uncoordination of the pyrazolyl rings of hydrotris(pyrazolyl)borate ligands in complexes of Rh-I and Rh-III

Compounds of rhodium(r) and rhodium(III) that contain ancillary hydrotris ( pyrazolyl) borate ligands (Tp') react with monodentate and bidentate tertia ry phosphanes in a step-wise manner, with incorporation of P-donor atoms an d concomitant replacement of the Tp' pyrazolyl rings. Accordingly, [Rh(kapp a (3)-Tp(Me2))(C2H4) (PMe3)] (1b), converts initially into [Rh(kappa (2)-Tp (Me2))(PMe3)(2)] (3), and then into [Rh(kappa (1)-Tp(Me2))(PMe3)(3)] (2) up on interaction with PMe3 at room temperature, in a process which can be rea dily reversed under appropriate experimental conditions. Full disengagement of the Tp' ligand is feasible to give Tp' salts of rhodium(I) complex cati ons, for example, [Rh(CO)(dppp)(2)][Tp(Me24-Cl)] (5; dppp = Ph2P(CH2)(3)PPh 2), or [Rh(dppp)(2)][Tp(Me2,4-Cl)] (6). Bis(hydride) derivatives of rhodium (iii) exhibit similar substitution chemistry, for instance, the neutral com plex [Rh(Tp)(H)(2)(PMe3)] reacts at 20 degreesC with an excess Of PMe3 to g ive [Rh(H)(2)(PMe3)(4)][Tp] (9b). Single-crystal X-ray studies of 9b, condu cted at 143 K, demonstrate the absence of bonding interactions between the [Rh(H)(2)(PMe3)(4)](+) and Tp ions, the closest Rh...N contact being at 4.6 27 Angstrom.