(PENTAMETHYLCYCLOPENTADIENYL)BIS(PYRAZOLATO)(PYRAZOLE) - IRIDIUM(III) AS A METAL-COMPLEX LIGAND - SYNTHESIS, CHARACTERIZATION, AND REACTIVITY OF HETERODINUCLEAR IRM [M = CU(I), AG(I), AU(I), RH(I)] AND HETEROTRINUCLEAR IRAG2 AND IRRHAG DERIVATIVES

Heterodinuclear complexes of formula [(eta-5-C5Me5)Ir(pz)3M(PPh3)] [M = Cu (2), Ag (3), Au (4)] have been prepared by treating the mononuclear iridium pentamethylcyclopentadienyl pyrazolate complex [(eta-5-C5Me5)Ir(pz)2(Hpz)] (1) with the corresponding halide triphenylphosphine complex [MCl(PPh3]x (x = 4, M = Cu, Ag: x = 1, M = Au) and KOH. Complexes 2-4 are fluxional: at room temperature the MPPh3 fragment exchanges fast among the three free nitrogen atoms of the pyrazolate ligands. The molecular structure of complex 3 has been determined. Crystals are monoclinic, space group P2(1)/n, with cell parameters a = 9.6171 (4) angstrom, b = 14.2115 (7) angstrom, c = 26.229 (2) angstrom, beta = 91.90 (1)-degrees, and Z = 4. The structure was solved and refined to R and R(w) values of 0.0269 and 0.0289, respectively, with the use of 5498 reflections. In the solid state, this molecule exhibits two bridging pyrazolate groups between both metals; the iridium atom coordinates an additional terminal pyrazolate ligand and an eta-5-pentamethylcyclopentadiene ring; the silver metal completes its trigonal-planar coordination by being bonded to a PPh3 group. No direct intermetallic interaction is observed, the Ir...Ag distance being 3.8601 (2) angstrom. Complex 3 reacts with AgBF4 and PPh3, rendering [(eta-5-C5Me5)Ir(mu-pz)3{Ag(PPh3)}2]BF4 (5), in which both AgPPh3 exchange rapidly at room temperature. Complex 1 reacts with [Rh(acac)(COD)] to yield the complex [(eta-5-C5Me5)(pz)Ir(mu-pz)2Rh(COD)] (6) in 80% yield. Carbonylation of 6 gives [(eta-5-C5Me5)(pz)Ir(mu-pz)2Rh(CO)2] (7), which in turn reacts with mono or diphosphines rendering [(eta-5-C5Me5)(pz)Ir(mu-pz)2Rh(CO)(PR3)] [PR3 = PPh3 (8), P(OMe)3 (9)] or [(eta-5-C5Me5(pz)Ir(mu-pz)2Rh(PP)] [PP = dppe (10), R-prophos (11a,b)]. Compounds 6-8 can be protonated by HBF4 at one pyrazolate group, yielding the corresponding cationic complexes [(eta-5-C5Me5)(Hpz)Ir(mu-pz)2RhL2] (12-14). The heterotrinuclear IrRhAg derivatives [(eta-5-C5Me5)Ir{(mu-pz)Ag(PPh3)}{(mu-pz)2RhL2}]BF4 [L2 = COD (15); CO, PPh3 (16)] have been prepared by adding equimolar amounts of AgBF4 and PPh3 to complexes 6 and 8.