Bis(phosphine)bis(tellurocarboxylato)-palladium(II) and -platinum(II) complexes: synthesis and crystal structure

Bis(phosphine)bis(tellurocarboxylato)-palladium(II) and -platinum(II), [M(RCOTe)2(PR′3)2] (M = Pd or Pt; R = But, Ph, 4-MeC6H4, etc.; R′ = Et or Ph), were synthesized in moderate to good yields by treating sodium tellurocarboxylates or O-trimethylsilyl telluroesters with [MCl2(PR′3)2]. The platinum complexes with 2-methoxybenzenecarbotelluroato ligands also were synthesized from [Pt(PR′3)4] with the corresponding diacyl ditelluride. The tellurocarboxylato complexes are yellow to orange or red crystals, and labile thermally and toward oxygen. The nickel analogues [Ni(RCOTe)2(PR′3)2] (R′ = Et or Ph) were obtained by similar fashion, but were too labile to isolate. X-Ray diffraction analysis of trans-[Pt(4-MeC6H4COTe)2(PEt3)2] was carried out, and compared with those of the corresponding thio- and seleno-carboxylato complexes. These complexes crystallized in the same space group (P21/c) and are isostructural having a square-planar co-ordination geometry with thio- or telluro-carboxylato ligands which are unidentate.