The reactivity of new (1,5-cyclooctadiene)rhodium acylpyrazolonates towards N- and P-donor ligands: X-ray structures of [Rh(1,5-COD)QS], [Rh(1,5-COD)(phen)]QS.0.5H2O (HQS = 1-phenyl-3-methyl-4-(2-thienoyl)-pyrazol-5-one) and [Rh(1,5-COD)Br]2

Complexes [Rh(1,5-COD)(Q)] have been prepared by the reaction between [Rh(1,5-COD)Cl](2) (1,5-COD = 1,5-cyclooetadiene) and HQ (where HQ = 1-phenyl-3-methyl-4-R-pyrazol-5-one: R = 2-thenoyl (HQ(s)), 2-furanoyl (HQ(o)) or tert-butylacetyl (HQ(T)). [Rh(1,5-COD)(Q)] react with N-2-donor ligands such as 1,10-phenanthroline (phen) or 2,2-bipyridyl (bipy) yielding ionic compounds [Rh(1,5-COD)(N-2-donor)]Q. The substitutional lability of 1,5-COD in [Rh(1,5-COD)(Q)] versus mono- and di-organophosphine ligands was also investigated. In all cases 1,5-COD has been displaced. Reaction with two equivalents of PPh3 gave, upon oxidation of the Rh(l) centre, [Rh(PPh3)1(01)(Q)l species containing a eta(2)-peroxo-group. Reaction of [Rh(1,5-COD)(Q)] with the chelating P-2-donor 1,2-bis(diphenylphosphino)ethane (dppe) or 4,4'-bis(diphenylphosphino)ferrocene (dppf) yields the peroxo Rh(III) compounds [Rh(dppe)(2)O-2]Q(T) and [Rh(dppf)O-2(Q(T))] or Rh(I) species [Rh(dppf-O-2)(Q(T))] containing the diphosphine in the oxidised form. Finally the reaction between [Rh(1,5-COD)(Q)] and allylbromide yields the well-known [Rh(1,5-COD)Br](2). All complexes have been characterised by analytical and spectral data (IR, H-1 and P-31 ((1)HJ-NMR spectra). The crystal structures of [Rh(1,5-COD)(Q(5))], [Rh(1,5-COD)(phen)]Q(5) and [Rh(1,5-COD)Br](2), all containing a Rh(l) atom in a square coordinate environment, are also reported. (C) 2002 Elsevier Science B.V. All rights reserved.