SYNTHESES AND CHARACTERIZATION OF BINUCLEAR RH-2, IR-2 AND RHIR COMPLEXES CONTAINING DIMETHYL PHOSPHONATE AND PYRAZOLATE BRIDGING LIGANDS

The reaction of [Ir(eta(5)-C(5)Me(5))I{PO(OMe)(2)}{P(OH)OMe)(2)}] with pyrazole (Hpz) in the presence of AgPF6 gave (5)-C(5)Me(5)){PO(OMe)(2 )}{P(OH)(OMe)(2)}(Hpz)]PF6 1. Deprotonation of 1 with sodium carbonate afforded the neutral compound [Ir(eta(5)-C(5)Me(5)){PO(OMe)(2)}(2)(Hp z)] 2 which, in turn, can be deprotonated to [(eta(5)-C(5)Me(5))Ir{PO( OMe)(2)}(2)(pz)M'] (M' = Tl 3 or Na 4) by Tl(acac) (acac = acetylaceto nate) or NaH, respectively. The complex [Ir(eta(5)-C(5)Me(5))I-2{P(OH) (OMe)(2)}] 5, prepared by cleaving the iodide bridges in [{Ir(eta(5)-C (5)Me(5))I}(2)(mu-I)(2)] with HPO(OMe)(2), reacted with Hpz in the pre sence of AgPF6 to give [Ir(eta(5)-C(5)Me(5)){PO(OMe)(2)}(Hpz)(2)]PF6 6 . Complexes of formulae [(eta(5)-C(5)Me(5))Ir{PO(OMe)(2)(pz)M '' L(2)] [M '' L(2) = Rh(CO)(2) 7, Rh(cod) 8 or Ir(cod) 9] were prepared from 2 [Rh(acac)(CO)(2)] or from 3 and the appropriate [{M ''(cod)}(2)(mu-Cl )(2) dimer (cod = cycloocta-1,5-diene). Complex 6 reacted with [{Rh(co d)}(2)(mu-Cl)(2)] in basic medium to give [(eta(5)-C(5)Me(5))Ir{PO(OMe )(2)}(pz)(2)Rh(cod)] 10. The rhodium-thallium compound [(eta(5)-C(5)Me (5))Rh{PO(OMe)(2)}(2)(pz)Tl] or the in situ prepared sodium derivative [(eta(5)-C(5)Me(5))Rh{PO(OMe)(2)}(pz)(2)Na] reacted with the dimers [ {M ''(diolefin)}(2)(mu-Cl)(2)] affording [(eta(5)-C(5)Me(5))Rh{PO(OMe) (2)}(2)(pz)M ''(diolefin) = [M ''(diolefin) = Ir(cod) 11 or Rh(nbd) 12 ] or (eta(5)-C(5)Me(5)){PO(OMe)(2)}Rh(pz)(2)}Rh(pz)(2)M ''(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 o f general formula [I(eta(5)-C(5)Me(5))M{PO(OMe(2)}(2)M ''(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(eta(5)-C(5)Me(5))I{PO(OMe)(2)}{P(OH) (OMe)(2)}] (M = Ir or Rh). All the complexes have been characterized b y spectroscopic of 8 by toluene-p-sulfonic acid is reported. The struc tures of 8 and 16 have been determined by X-ray diffraction methods. B oth complexes consist of doubly bridged binuclear (C(5)Me(5))Ir-Rh(cod ) species, where the Ir atoms exhibit pseudo-octahedral co-ordination 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 a nd a phosphonate ligand are bridging the metals. The intermetallic sep arations are 4.0445(9) (8) and 4.0928(9) Angstrom (16).