Complexes of platinum, palladium, and rhodium with tertiary phosphine carboxylic esters and carboxylic acids

Abstract

The new tertiary phosphine esters Bu^t₂P(CH₂)_nCO₂Et [L¹(n= 1), L²(n= 2), and L³(n= 3)] are described. Treatment of trans-[PtCl₂L¹₂] with NaI in refluxing ethanol gives the O-metallated species [[graphic omitted]Bu^t₂)L¹], which on heating with Na[O₂CMe] in 2-methoxyethanol give trans-[[graphic omitted]Bu^t₂)₂]. The ¹H and ³¹P n.m.r. spectra of [[graphic omitted]Bu^t₂)L¹] vary with temperature due to the presence of two rotamers, and the complex is reduced by Na[BH₄] to [PtH(OCOCH₂PBu^t₂)(Bu^t₂PCH₂CH₂OH)]. With hydrazine, trans-[PtCl₂L¹₂] gives the very stable [[graphic omitted]Bu^t₂)] containing a tridentate ligand. The complex [PtCl₂(NCBu^t)₂] with L²(1 mol proportion) gives the binuclear [Pt₂Cl₄L²₂]; similarly with L³[Pt₂Cl₄L³₂] is formed which when heated in toluene undergoes C-metallation to give [[graphic omitted]HCO₂Et)₂](mixtures of isomers) which in turn with PPh₃ gives [[graphic omitted]HCO₂Et)(PPh₃](single isomer). Attempts to effect O-metallation with [PdCl₂L¹₂] lead to decomposition, but with ammonia the bischelate [[graphic omitted]Bu^t₂)₂] isfor med. Binuclear species [Pd₂X₄L²₂](X = Cl or I) have been prepared, and also cis-[PtCl₂Q₂] and trans-[PdCl₂Q₂](Q = Ph₂PCH₂CO₂Et). These Ph₂PCH₂CO₂Et complexes do not undergo O-metallation when heated with Nal, the complexes trans-[MI₂Q₂] being formed. However, treatment of [PdCl₂(NCPh)₂] with Ph₂PCH₂CO₂H gives [[graphic omitted]Ph₂)(Ph₂PCH₂CO₂H)] which with Na[O₂CMe] gives [[graphic omitted]Ph₂)₂]; similarly for platinum. The compound RhCl₃·3H₂O reacts with L¹ to give the six-co-ordinate rhodium(III) species [[graphic omitted]OEt)₂]⁺ isolated as its tetraphenylborate salt. This cation is converted by Na[BH₄] to [RhH₂(BH₄)(Bu^t₂PCH₂CO₂Et)₂]. The compound RhCl₃·3H₂O reacts with L² or L³ to give the rhodium(II) species trans-[RhCl₂L²₂] or trans-[RhCl₂L³₂], respectively.