Uni-, bi- and ter-dentate complexes formed from PPh2CH2C(R)NNHC(O)Ph (R = But or Ph) and Pd or Pt: crystal structures of [PdCl{PPh2CH2C(But)NNC(Ph)O}], [Pt{PPh2CHC(Ph)NNC(Ph)O}{PPh2CH2C(Ph)NNHC(O)Ph}] and [Pd{PPh2CHC(But)NHNC(O)Ph}2]

Abstract

Treatment of the phosphino-N-benzoyl hydrazones PPh₂CH₂C(R)NNHC(O)Ph (R = Bu^t, I; R = Ph, II) with [MCl₂(NCPh)₂] (M = Pd or Pt) gave complexes of type [MCl{PPh₂CH₂C(Bu^t)NNC(Ph)O}] (M = Pd, 1; M = Pt, 2) containing two fused five-membered chelate rings. Metathesis with LiBr or NaI gave [MX{PPh₂CH₂C(Bu^t)NNC(Ph)O}] (X = Br or I; M = Pd or Pt). The complex [PtMe{PPh₂CH₂C(Bu^t)NNC(Ph)O}] (8) was obtained by treating [PtMe₂(cod)] (cod = cycloocta-1,5-diene) with one equivalent of I in hot benzene. Treatment of [PtMe₂(cod)] with two equivalents of the phosphine II gave [PtMe{PPh₂CH₂C(Ph)NNC(O)Ph}{PPh₂CH₂C(Ph)NNHC(O)Ph] (11), containing a six-membered chelate ring and a unidentate coordinated ligand II. Treatment of [PtCl₂(NCMe)₂] with two equivalents of II in the presence of triethylamine gave [Pt{PPh₂CHC(Ph)N–NC(Ph)O}{PPh₂CH₂C(Ph)NNHC(O)Ph] (12), containing a terdentate (P,N,O-bonded) doubly deprotonated ene-hydrazone ligand and a unidentate ligand II. Prolonged treatment of [PdCl₂(NCPh)₂] with two equivalents of I in the presence of triethylamine gave [Pd{PPh₂CHC(Bu^t)NHNC(O)Ph}₂] (13), containing two chelated phosphino ene-hydrazide ligands forming six-membered rings. A similar platinum complex, [Pt{PPh₂CHC(Bu^t)NHNC(O)Ph}₂] (14), was synthesised. The terdentate complexes of [MX{PPh₂CH₂C(Bu^t)NNC(Ph)O}] (M = Pd, Pt; X = Cl, Me) underwent base-promoted (NEt₃) Michael-type reactions with MeO₂CCCCO₂Me to give terdentate complexes of the type [MX{PPh₂CH[C(CO₂Me)CH(CO₂Me)]C(Bu^t)NNC(Ph)O}] (M = Pd, Pt; X = Cl, Me). The corresponding bromides and iodides were made by metathesis. The crystal structures of 1, 12 and 13 have been determined.