Synthesis and characterization of the alkoxycarbonyl complexes [(C5Me5)M(µ-pz)(µ-I)2Rhl(CO2R)(CO)](M = Rh, R = Me or Et; M = Ir, R = Me; pz = pyrazolate). Molecular structure of [(C5Me5)Ir(µ-pz)(µ-I)2Rhl(CO2Me)(CO)]

Abstract

The alkoxycarbonyl complexes [(C₅Me₅)M(µ-pz)(µ-I)₂Rhl(CO₂R)(CO)][M = Rh, R = Me, (4), or Et, (5); M = Ir, R = Me, (6); pz = pyrazolate] were prepared by treating the corresponding dicarbonyl complex [(C₅Me₅)ClM(µ-pz)₂Rh(CO)₂][M = Rh, (1), or Ir, (3)] with molecular iodine in methanol [(4), (6)] or ethanol [(5)] and in the presence of sodium salts (i.e. NaBPh₄, NaI·2H₂O). The molecular structure of compound (6) was determined by X-ray diffraction: monoclinic space group C2/c with a= 28.574(3), b= 8.688(1), c= 19.321 (2)Å, β= 96.44(1)°, and Z= 8. The structure was refined to R= 0.037 for 2 789 observed reflections [F 5.0σ(F)] and 236 parameters. The complex is dinuclear with the two metals, bridged by two iodides and a pyrazolate ligand. The rhodium exhibits distorted-octahedral co-ordination involving three terminal ligands: an iodide, a carbonyl, and a methoxycarbonyl group formed during the preparative reaction.