Heterobinuclear IrRh, RuRh and Rulr complexes with pyrazolate bridging ligands: reactivity towards chelating diphosphines; crystal structure of [(C5Me5)Ir(µ-pz)2(µ-CO)-Ir(CO)(dppen)]BPh4·0.5MeOH [pz = pyrazolate, dppen =cis-1,2-bis(diphenylphosphino)ethylene]

Abstract

Complexes of general formula [LClM(µ-pz)₂M′(cod)]1–5[L = C₅Me₅, M = Rh or Ir; L =p-cymene, Me = Ru; M′= Rh or Ir; pz = pyrazolate; cod = cycloocta-T,5-diene (not all possible combinations)] and [(MeC₆H₄Prⁱ-p)Ru(µ-pz)(µ-Cl)₂Rh(cod)]7 were prepared starting from mononuclear acetylacetonate and pyrazole or pyrazolate-containing moieties. Complexes 1–5 react with CO yielding derivatives [LClM(µ-pz)₂M′(CO)₂]8–12. Complexes [(C₅Me₅)ClRh(µ-pz)₂Rh(CO)₂]13 and [(MeC₆H₄Prⁱ-p)CIRu(µ-pz)₂Ir(CO)₂]12 react with NaX to give [(C₅Me₅)XRh(µ-pz)₂Rh(CO)₂](X = I, 14; or N₃, 15) and [(MeC₆H₄Prⁱ-p)[graphic omitted]rX(CO)₂](X = Br, 16; or I, 17. The dicarbonyl compound 10 and [(MeC₆H₄Prⁱ-p)CIRu(µ-pz)₂M′(CO)₂](M′= Rh, 11; or Ir, 12) react with diphosphines (L–L) or 1,2-bis(diphenylarsino)ethane (dpae) and NaBPh₄ or AgBF₄ affording cationic complexes [LM(µ-pz)₂(µ-CO)M′(L–L)]A 23–31[L–L = bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, cis-1,2-bis-(diphenylphosphino)ethylene (dppen) or dpae; A = BPh₄ or BF₄(not all possible combinations)]. In this reaction intermediates [LM(µ-pz)₂(µ-CO)M′(CO)(L–L)]A have been isolated in some cases. The crystal structure of one of these [(C₅Me₅)Ir(µ-pz)₂(µ-CO)Ir(CO)(dppen)] BPh₄·0.5MeOH 19 has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P2₁/c, a= 15.996(2), b= 22.199(4), c= 18.874(3)Å, β= 115.04(1)° and Z= 4. The complex cation consists of two iridium atoms bridged by two pyrazolates and one ketonic carbonyl group. An η⁵-C₅Me₅ ligand, a chelate dppen and a terminal CO group complete the co-ordination spheres of the iridium atoms, which are separated by 3.440(5)Å.