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}2C6H2SnCl)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)2Pt(SnCl3)2] (10) and [(4-tBu-2,6-{P(O)(OiPr)2}2C6H2SnCl)3Pt(SnCl3)2] (11). The compounds were characterised by elemental analyses, (1)H, (13)C, (31)P, (119)Sn and (195)Pt NMR spectroscopy, single-crystal X-ray diffraction analysis, UV/Vis spectroscopy and, in the cases of compounds 1, 3 and 4, also by Mössbauer spectroscopy. All the compounds show the tin atoms in a distorted trigonal-bipyramidal environment. The Mössbauer 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-(Me2 NCH2)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.

Synthesis and characterization of Sn(IV) complexes of lower rim 1,3-diacid derivative of calix[4]arene and their protective effects on tissue oxidative stress and essential metal concentration in lead exposed male Wistar rats.

The two Sn(IV) complexes synthesized using calix[4]arene-1,3-di-acid derivative were characterized by analytical, (1)H, (13)C and (119)Sn NMR, matrix assisted laser desorption ionization mass, and (119)Sn Mossbauer techniques and found that the complexes are tetranuclear possessing structurally two different types of tin centers. These complexes were evaluated for their protective value against blood and tissue oxidative stress in lead exposed male albino rats of Wistar strain. The results suggest that the two tin complexes significantly protect changes in lead induced biochemical variables indicative of heme synthesis pathway and exhibit only moderate effect on tissue oxidative stress. The beneficial effects could be attributed mainly to the ability of Sn(IV) complexes in preventing absorption of lead to the target sites/tissues.