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

Abstract

The reaction of trans-IrCl(CO)L 2 with pz − 1 1 Throughout this paper, 1-unsubstituted pyrazole (C 3H 4N 2) is indicated by PzH, while pzH indicates a generic pyrazole on which ring substituents may be present (e.g.3,5-Me 2-4-NO 2pzH is 3,5-dimethyl-4-nitropyrazole). gives trans-Ir(pz- N)(CO)L 2, where pzH is 3,5-dimethyl-, 3,5-dimethyl-4-nitro- or 3,5-bis(trifluoromethyl)-pyrazole, and L = PPh 3. The nitrogen atom not involved in coordination can be protonated with HBF 4 to give the corresponding [Ir(CO)L 2(pzH- N] + cation. The iridium(I) pyrazolates undergo oxidative addition, yielding Ir(H) 2(pz- N)(CO)L 2 species, while gaseous HCl cleaves the IrN bond, affording IrH(Cl) 2(CO)L 2. 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-(CF 3) 2pz- N)(CO)L 2, in the form with ν(CO) at 1975 cm −1, is supported also by an X-ray crystal structure determination. The compound crystallizes in the monoclinic system, space group P2 1/ n, with cell dimensions a = 21.106(6), b = 19.700(5), c = 9.437(2) Å, and β = 94.34(2)° and Z = 4.