(1-Phenyl-3-methyl-4-acetylpyrazolon-5-ato)rhodium(I) complexes, synthesis, structural and spectroscopical characterization: Reactivity of diolefin- and dicarbonyl-rhodium complexes toward N-, P- and O-donors

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Novel complexes of rhodium(I) [Rh(diolefin)(Q″)] (where HQ″=1-phenyl-3-methyl-4-acetylpyrazol-5-one and diolefin=cycloocta-1,5-diene (COD), bicyclo[2.2.1]hepta-2,5-diene (NBD) or 1,5-hexadiene (HEX)) were synthesized and characterized by analytical and spectral data. [Rh(COD)(Q″)] interacts with 4,5-dimethyl-1,10-phenanthroline (Me 2Phen) and 2,2′-bipyridil (Bipy) yielding the cationic derivatives [Rh(COD)(Me 2Phen)](Q″)(H 2O), [Rh(COD)(Bipy)](Q″)(H 2O) upon displacement of the (Q″) − donor from the coordination sphere of the metal center. Whereas [Rh(COD)(Q″)] interacts with 2-benzoylpyridine (Bzpy) yielding the 1:1 adduct [Rh(COD)(Bzpy)(Q″)] in which Bzpy acts as N-monodentate donor. On the other hand the monodentate P-donors triphenylphosphine, triphenylphosphite, tricyclohexylphosphine and the bidentate bis(diphenylphosphino)ethane (DPPE) displace the COD ligand from [Rh(COD)(Q″)] giving the neutral derivatives [Rh(PR 3) 2(Q″)] (PR 3=PPh 3, or P(OPh) 3) and [Rh(DPPE)(Q″)](H 2O). HQ″ reacts with the dinuclear [Rh(CO) 2Cl] 2. The tetradentate cycloocto-tetraene (COT) reacts with [Rh(CO) 2(Q″)] yielding the derivative [Rh(CO) 2(HQ″)Cl] in which HQ″ acts as neutral monodentate O-donor ligand. Whereas in presence of NEt 3 HQ″ reacts with [Rh(CO) 2Cl] 2 yielding [Rh(CO) 2(Q″)]. In this complex, one molecule of CO can be replaced by one mole of Phen and Bipy or by two moles of PPh 3 and AsPh 3 yielding the derivatives [Rh(CO)(L) n (Q″)]·x(H 2O) (L=Me 2Phen or Bipy, n=1; L=PPh 3 or AsPh 3, n=2) whereas one mole of DPPE displaces both the molecules of CO, yielding [Rh(DPPE)(Q″)] yielding the derivative [Rh(COT)(Q″)]. The X-ray crystal structure determination of [Rh(COD)(Q″)] establishes that the rhodium atom is in a square planar configuration with two adjacent sites occupied by the (Q″) − ligand in the O 2-bidentate form (Rh–O distances=2.054(2) and 2.061(2) Å). The COD ring has a twisted boat conformation with Rh–C distances in the range 2.101(3)–2.110(3) Å. Comparison was made with structural data reported for several related tetracoordinated (COD)Rh(I) adducts.