A Series of monohapto pyrazolates of iridium(I) and iridium(III)

The reaction of trans-IrCl(CO)L2 with pz-1 1 Throughout this paper, 1-unsubstituted pyrazole (C3H4N2) is indicated by PzH, while pzH indicates a generic pyrazole on which ring substituents may be present (e.g.3,5-Me2-4-NO2pzH is 3,5-dimethyl-4-nitropyrazole). gives trans-Ir(pz-N)(CO)L2, where pzH is 3,5-dimethyl-, 3,5-dimethyl-4-nitro- or 3,5-bis(trifluoromethyl)-pyrazole, and L = PPh3. The nitrogen atom not involved in coordination can be protonated with HBF4 to give the corresponding [Ir(CO)L2(pzH-N]+ cation. The iridium(I) pyrazolates undergo oxidative addition, yielding Ir(H)2(pz-N)(CO)L2 species, while gaseous HCl cleaves the IrN bond, affording IrH(Cl)2(CO)L2. The iridium(I) derivatives can be obtained in several solid-state forms, each characterized by a slightly different CO stretching frequency. The presence of a monodentate pyrazolato ligand in trans-Ir(3,5-(CF3)2pz-N)(CO)L2, in the form with \u3bd(CO) at 1975 cm-1, is supported also by an X-ray crystal structure determination. The compound crystallizes in the monoclinic system, space group P21/n, with cell dimensions a = 21.106(6), b = 19.700(5), c = 9.437(2) \uc5, and \u3b2 = 94.34(2)\ub0 and Z = 4. \ua9 1984