Di-n-octyltin(IV) complexes with 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acid: Syntheses and assessment of solid state structures by 119Sn Mössbauer and X-ray diffraction and further insight into the solution structures using electrospray ionization

Reactions of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L1HH′: X = H; L2HH′: X=2′-OCH3; L3HH′: X = 3′-CH3; L4HH′: X = 4′-CH3; L5HH′:X = 4′-Cl) with nOct2SnO in 2:1 and 1:1 molar ratios have been investigated. Two types of complexes, nOct2Sn(LH)2 and {[nOct2Sn(LH)]2O}2, were isolated and they have been characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of nOct2Sn(L1H)2 (1), {[nOct2Sn(L2H)]2O}2 (3) and {[nOct2Sn(L3H)]2O}2(4) were determined. The mononuclear complex 1 was found to adopt a skew-trapezoidal bipyramidal arrangement around the tin atom while 3 and 4 are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn4O2 core in which two μ3-oxo O-atoms connect an Sn2O2 ring to two exocyclic Sn-atoms. The solution structures were confirmed by 119Sn NMR spectroscopy by observing one tin resonance in compound 1 and two tin resonances in {[nOct2Sn(L5H)]2O}2 (5). {[nOct2Sn(L2H)]2O}2 (3) and {[nOct2Sn(L3H)]2O}2 (4) undergo very complex exchange processes in deuteriochloroform solution, which has been confirmed by variable temperature 1H NMR spectroscopy. The cleavage of the most labile bond in the molecule was studied by ESI mass spectrometry.