The unique alternation of conformationally different (‘chair’-‘saddle’) eight-membered metallocycles [Cd2S4P2] in the chains of cadmium dialkyldithiophosphates: 13C, 31P, 113Cd CP/MAS NMR and single-crystal X-ray diffraction studies

O,O′-Dipropyldithiophosphate and O,O′-dibutyldithiophosphate (Dtph) cadmium(II) complexes were prepared and studied by means of heteronuclear 31P, 113Cd, 31C CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Linear-chain polynuclear structures have been established for both cadmium(II) complexes, in which each pair of equivalent dithiophosphate groups, playing the same bridging structural function, asymmetrically links the neighbouring cadmium atoms. One remarkable structural feature of the synthesised cadmium(II) compounds is defined by the alternation of two types of conformationally different (‘chair’–‘saddle’) eight-membered rings [Cd2S4P2] in the polymeric chains. Therefore, in both 31P NMR and XRD data, the bridging dithiophosphate ligands exhibit structural inequivalence in pairs. The structural states of both Dtph ligands and cadmium atoms have been characterised by the 31P and 113Cd chemical shift tensors, which display a profound axially symmetric and mainly rhombic characters, respectively. All experimental 31P resonances were assigned to the phosphorus structural sites in both resolved structures.

Graphical abstractPolynuclear cadmium(II) complexes, [Cd{S2P(OR)2}2]n, with two symmetric O,O′-dialkyldithiophosphate-ions, (RO)2P(S)S− (R = C3H7, C4H9), have been prepared and studied by heteronuclear 13C, 31P, 113Cd CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. A remarkable structural feature of these compounds is defined by the alternation of conformationally different (‘chair’–‘saddle’) eight-membered rings [Cd2S4P2] in polymeric zigzag chains. To characterise the structural states of the bridging non-equivalent Dtph ligands and the central atoms, 31P and 113Cd chemical shift anisotropy parameters (δaniso and η) were calculated from spinning sideband manifolds in NMR spectra.Figure optionsDownload full-size imageDownload as PowerPoint slide