Reaction of [RhCl(CO)2]2 or [RhCl(COD)]2 with o-(diphenylphosphino)benzaldehyde.: Formation of hemiaminals in the subsequent reaction with dihydrazones

[RhCl(CO)(2)](2) reacts with o-(diphenylphosphino)benzaldehyde (PCHO) to afford a monocarbonylated rhodium(l) complex containing P-monodentate PCHO, trans-[RhCl(CO)(PCHO)(2)] (1) while [RhCl(COD)]2 undergoes the oxidative addition of one PCHO, with displacement of 1,5-cyclooctadiene, and coordination of the second PCHO molecule as P-(sigma-aldehyde) chelate to give [RhH(PCO)Cl(PCHO)] (2) which contains trans P-atoms. Compound 2 reacts with H,NN-CHCH=NNH2 (gdh) to give selectively a complex [RhH(PCO)(Pgdh)](+) containing a stable hemiaminal in a new tridentate ligand, Pgdh, coordinated via the imino nitrogens and the phosphorus and the atom. The reaction of Rh(COD)(gdh)CI with PCHO gives a mixture of the hemiaminal containing compound and the hydroxyalkyl complex [Rh(PCO)(PCHOH)(gdh)](+) which contains trans P-atoms and is formed from precursors containing cis P-atoms. The transformation of the hemiaminal group in [RhH(PCO)(PNN)](+) (PNN = Pgdh or Ppvdh (pvdh. H,NN=CHC(CH3) NNH2)) into imine to give new tridentate PaNN ligands in complexes [RhH(PCO)(PaNN)]has also been studied. (C) 2002 Elsevier Science B.V. All rights reserved.