Syntheses and characterization of binuclear Rh2, Ir2 and RhIr complexes containing dimethyl phosphonate and pyrazolate bridging ligands

The reaction of [Ir(η5-C5Me5)I{PO(OMe)2}{P(OH)(OMe)2}] with pyrazole (Hpz) in the presence of AgPF6 gave [Ir(η5-C5Me5){PO(OMe)2}{P(OH)(OMe)2}(Hpz)]PF61. Deprotonation of 1 with sodium carbonate afforded the neutral compound [Ir(η5-C5Me5){PO(OMe)2}2(Hpz)]2 which, in turn, can be deprotonated to [(η5-C5Me5)Ir{PO(OMe)2}2(pz)M′](M′= Tl 3 or Na 4) by Tl(acac)(acac = acetylacetonate) or NaH, respectively. The complex [Ir(η5-C5Me5)I2{P(OH)(OMe)2}]5, prepared by cleaving the iodide bridges in [{Ir(η5-C5Me5)I}2(µ-I)2] with HPO(OMe)2, reacted with Hpz in the presence of AgPF6 to give [Ir(η5-C5Me5){PO(OMe)2}(Hpz)2]PF66. Complexes of formulae [(η5-C5Me5)Ir{PO(OMe)2}2(pz)M″L2][M″L2= Rh(CO)27, Rh(cod)8 or Ir(cod)9] were prepared from 2 and [Rh(acac)(CO)2] or from 3′ and the appropriate [{M″(cod)}2(µ-Cl)2] dimer (cod = cycloocta-1,5-diene). Complex 6 reacted with [{Rh(cod)}2(µ-Cl)2] in basic medium to give [(η5-C5Me5)Ir{PO(OMe)2}(pz)2Rh(cod)]10. The rhodium–thallium compound [(η5-C5Me5)Rh{PO(OMe)2(pz)Tl] or the in situ prepared sodium derivative [(η5-C5Me5)Rh{PO(OMe)2}(pz)2Na] reacted with the dimers [{M″(diolefin)}2(µ-Cl)2] affording [(η5-C5Me5)Rh{PO(OMe)2}2(pz)M″(diolefin)][M″(diolefin)= Ir(cod)11 or Rh(nbd)12] or [(η5-C5Me5){PO(OMe)2}Rh(pz)2M″(diolefin)][M″(diolefin)= Rh(cod)13, Ir(cod)14 or Rh(nbd)15], respectively (nbd = bicyclo[2.2.1]hepta-2,5-diene). Related heterovalent complexes of general formula [I(η5-C5Me5)M{PO(OMe)2}2M″(diolefin)][M = Ir, M′(diolefin)= Rh(cod)16 or Ir(cod)17; M = Rh, M″(diolefin)= Rh(cod)18, Ir(cod)19, or Rh(nbd)20] have been prepared starting from the mononuclear complexes [M(η5-C5Me5I{PO(OMe)2}{P(OH)(OMe)2}](M = Ir or Rh). All the complexes have been characterized by spectroscopic means and the fluxional behaviour of 7–9, 11 and 12, in solution, has been studied. The protonation of 8 by toluene-p-sulfonic acid is reported. The structures of 8 and 16 have been determined by X-ray diffraction methods. Both complexes consist of doubly bridged binuclear (C5Me5)Ir–Rh(cod) species, where the Ir atoms exhibit pseudo-octahedral coordination and the rhodium square planar. The bridging system in 16 is formed by two identical P,O-bonded phosphonate groups, while in 8 a pyrazolate and a phosphonate ligand are bridging the metals. The intermetallic separations are 4.0445(9)(8) and 4.0928(9)Å(16).