Synthesis of Pt(ii) phosphinocarboxylate complexes with auxiliary arylcarbene ligands and factors that control their stereochemistry

Abstract

Orthoplatinated complexes [Pt(C^C*)(acac)] (1^R), in which C^C* is orthoplatinated 3-R-1-phenyl-1H-benzo[d]imidazol-2-ylidene and R = Me and Ph, reacted with 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) under protonation of the acetylacetonate ligand (acac) to produce the corresponding phosphinocarboxylate bischelate complexes [Pt(C^C*)(dpf-κ²O,P)] (2^R) as single isomers with trans-P,C(carbene) geometry. The compounds were fully characterized by elemental analysis, spectroscopic methods, single-crystal X-ray diffraction analysis, and cyclic voltammetry. In addition, DFT calculations were used to determine differences in energy and the bonding situation between 2^R and the hypothetical geometric isomers 3^R with a trans-P,C(phenyl) arrangement. The experimental and theoretical results are consistent with the antisymbiosis effect observed in complexes of soft metal ions, namely with weakening of Pt–C bonds by strongly trans-influencing ligands.