Insights into the intramolecular donor stabilisation of organostannylene palladium and platinum complexes: syntheses, structures and DFT calculations.

The syntheses of the transition metal complexes cis-[(4-tBu-2,6-{P(O)(OiPr)2}2C6H2SnCl)2MX2] (1, M=Pd, X=Cl; 2, M=Pd, X=Br; 3, M=Pd, X=I; 4, M=Pt, X=Cl), cis-[{2,6-(Me2NCH2)2C6H3SnCl}2MX2] (5, M=Pd, X=I; 6, M=Pt, X=Cl), trans-[{2,6-(Me2NCH2)2C6H3SnI}2PtI2] (7) and trans-[(4-tBu-2,6-{P(O)(OiPr)2}2 C6H2SnCl)PdI2]2 (8) are reported. Also reported is the serendipitous formation of the unprecedented complexes trans-[(4-tBu-2,6-{P(O)(OiPr)2}2C6H2SnCl)2 Pt(SnCl3)2] (10) and [(4-tBu-2,6-{P(O) (OiPr)2}2C6H2SnCl)3Pt(SnCl3)2] (11). The compounds were characterised by elemental analyses, 1H, 13C, 31P, 119Sn and 195Pt NMR spectroscopy, single-crystal X-ray diffraction analysis, UV/Vis spectroscopy and, in the cases of compounds 1, 3 and 4, also by Mossbauer spectroscopy. All the compounds show the tin atoms in a distorted trigonal-bipyramidal environment. The Mossbauer spectra suggest the tin atoms to be present in the oxidation state III. The kinetic lability of the complexes was studied by redistribution reactions between compounds 1 and 3 as well as between 1 and cis-[{2,6-(Me2NCH2)2C6H3SnCl}2PdCl2]. DFT calculations provided insights into both the bonding situation of the compounds and the energy difference between the cis and trans isomers. The latter is influenced by the donor strength of the pincer-type ligands.