Crystalline O, O′-di- sec-butyl and O, O′-diethyl dithiophosphate platinum(II) complexes: Synthesis, 13C and 31P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour

Abstract

Crystalline bis( O, O′-di- sec-butyldithiophosphato)platinum(II) was prepared and studied by means of 13C, 31P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S 2P(O- sec-C 4H 9) 2} 2], in which the dithiophosphate groups display structural equivalence in both 31P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S, S′-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS 2P], in this molecule. The planar configuration of the [PtS 4] chromophore in structure 1 is governed by the dsp 2-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from ethanol and the other one precipitated from an aqueous solution) are all characterised by almost rhombic 31P chemical shift tensors. The observed essential dispersion of the 31P NMR chemical shift is caused by a coexistence of six optical isomers of molecule 1. The thermal behaviour of this compound was studied by means of simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour shows that the mass of 1 is lost in three steps, involving successive thermal decompositions of the organic and inorganic parts of this compound with platinum(II) dithio- meta-phosphate and reduced metallic platinum as the intermediate and the final products, respectively.