Syntheses, Structures, and Reactivity of new Pentamethylcyclopentadienyl-Rhodium(III) and –Iridium(III) 4-Acyl-5-Pyrazolonate Complexes

New [Cp*M(Q)Cl] complexes (M = Rh or Ir, Cp* = pentamethylcyclopentadienyl, HQ = 1-phenyl-3-methyl-4R(CO)-pyrazol-5-one in general, in detail HQMe, R = CH3; HQEt, R = CH2CH3; HQPiv, R = CH2−C(CH3)3; HQBn, R = CH2−(C6H5); HQS, R = CH−(C6H5)2) have been synthesized from the reaction of [Cp*MCl2]2 with the sodium salt, NaQ, of the appropriate HQ proligand. Crystal structure determinations for a representative selection of these [Cp*M(Q)Cl] compounds show a pseudo-octahedral metal environment with the Q ligand bonded in the O,O‘-chelating form. In each case, two enantiomers (SM) and (RM) arise, differing only in the metal chirality. The reaction of [Cp*Rh(QBn)Cl] with MgCH3Br produces only halide exchange with the formation of [Cp*Rh(QBn)Br]. The [Cp*Rh(Q)Cl] complexes react with PPh3 in dichloromethane yielding the adducts Cp*Rh(Q)Cl/PPh3 (1:1) which exist in solution in two different isomeric forms. The interaction of [Cp*Rh(QMe)Cl] with AgNO3 in MeCN allows generation of [Cp*Rh(QMe)(MeCN)]NO3·3H2O, whereas the reaction of [Cp*Rh(QMe)Cl] with AgClO4 in the same solvent yields both [Cp*Rh(QMe)(H2O)]ClO4 and [Cp*Rh(Cl)(H2O)2]ClO4; the H2O molecules derive from the not-rigorously anhydrous solvents or silver salts.