X-ray Diffraction and 2D Gradient-Assisted ¹H−¹¹⁹Sn HMQC NMR Studies of Structures Obtained from Nucleophilic Substitutions on Dimethyltin(IV) Salicylaldoximates

Abstract

The reactivity of the trinuclear tin cluster [(Me2Sn)2(Me2SnO)(OCH3)(HONZO)(ONZO)] (3a; HONZOH = o-HONCH-C6H4-OH, salicylaldoxime) toward proton-donating nucleophiles is investigated with the purpose of studying the influence of the nature and acidity of the entering nucleophile on the reactivity of 3a and the stability of its cluster network. Reactions of 3a with benzaldoxime, HONCH-C6H5, and phenols HO-C6H5-n X n (pK a > 8) preserve the cluster network and give rise to smooth substitution of the μ2-OCH3 moiety for, respectively, a μ2-bridging benzaldoximate, generating [(Me2Sn)2(Me2SnO)(ONCHC6H5)(HONZO)(ONZO)] (4), and μ2-bridging phenolates, generating [(Me2Sn)2(Me2SnO)(OC6H5-n X n )(HONZO)(ONZO)] (n = 1, X = 4-Me (5a), 4-Br (5b), 3-Cl (5c), 3-NO2 (5d); n = 2, 3,5-Me2 (5e)). More acidic or sterically hindered ortho-disubstituted phenols lead to decomposition of the trinuclear cluster or to mixtures from which no pure trinuclear cluster can be isolated. Reactions of 3a with carboxylic acids, acetic and p-toluic acids, and acetylacetone lead to clean decomposition of the trinuclear cluster, yielding the respective bis[dicarboxylatotetramethyldistannoxanes], 6a and 6b, and dimethyltin bis(acetylacetonate), Me2Sn(acac)2, 7. Reaction of 3a with ethylene glycol generates a mixture of trinuclear clusters, from which 1,3-dioxa-2,2-dimethyl-2-stannacyclopentane (8a) precipitates. Crystal structure determinations by X-ray diffraction for 4, 5a, and 5b reveal essentially the same trinuclear clusters as in 3a and related compounds, with a seven-coordinate pentagonal-bipyramidal tin atom linked to two five-coordinate trigonal-bipyramidal tin atoms via a network of oxygen atoms. All new trinuclear tin clusters have been characterized in solution by gradient-assisted 2D NMR.

Heptacoordinate Tin(IV) Compounds Derived from Pyridine Schiff Bases: Synthesis, Characterization, in Vitro Cytotoxicity, Anti-inflammatory and Antioxidant Activity

“…In the first stage the loss of alkyl group attached to the tin atom (fragments ions C 5 NMR Spectroscopy The proton NMR spectroscopy of dibutyltin derivatives compounds 2a-g (Table 2) showed signals for the iminic proton in the range of 8.4 to 8.94, in the case of complexes 2b, 2f and 2g this signal is slightly shifted to lower frequencies with respect to the free ligand, however, for complexes whit butyl substituents bonded to the tin atom only multiple signals were observed. The proton NMR spectra of dimethyltin derivative compounds 2e-g and 2o, p showed single signals for the methyl groups in the range of Ϫ0.31 to 0.2 ppm as well as the corresponding satellites as a result of the spin-spin coupling 1 H- [58][59][60] The 13 C-NMR signals for the aromatic rings C-10 and C-1 of 2a-i showed a slight shift to low frequencies (Ddϭca. 10 and 7) respectively, with respect to free ligand.…”

“…[58][59][60] Combination of the information obtained from the Mass spectrometry and Multinuclear NMR led us to assume that all compounds are monomeric species possessing heptacoordinated geometry in solution. The solution-NMR spectral data for compounds 2h, 2i and 2q were not recorded due to their lack of solubility in most common solvents.…”

Gradient-Enhanced 2D Multinuclear NMR and X-ray Diffraction Studies of Reaction Products of Dimethyltin(IV) Salicylaldoximate with Chiral Alcohols

“…contrast, ligand B is dramatically twisted since the atom N18 is 0.3 Å away from the mean plane of the aromatic Reaction of salicylaldoxime, o-(HONϭCHϪC 6 H 4 ϪOH), ring with which it is associated [1a] [1b] [2] . As a consequence, and diorganotin(IV) oxide, R 2 SnO (R ϭ Me, n-Bu), yields these derivatives have a chiral skeleton in the solid state.…”

“…As a consequence, and diorganotin(IV) oxide, R 2 SnO (R ϭ Me, n-Bu), yields these derivatives have a chiral skeleton in the solid state. small clusters represented as [(R 2 Sn) 2 (R 2 SnO)(ONIn order to assess whether this skeleton chirality could be ZOH)(HONZO)(ONZO)] (1b: R ϭ n-Bu; 2b: R ϭ Me), detected in solution, we prepared dimethyltin salicylaldoxiwhere ONZOH is the oximate residue o-(ϪONϭ mate derivatives containing a ligand with a chiral center CHϪC 6 H 4 ϪOH), HONZO is the phenolate o-(HONϭ bridging the Sn (2) and Sn(3) tin atoms. Provided the chiral-CHϪC 6 H 4 ϪOϪ), and ONZO is the dibasic species oity of the cluster skeleton would be maintained in solution, (ϪONϭCHϪC 6 H 4 ϪOϪ), associated with salicylaldoxit should indeed be observable through the formation of the ime [1] .…”

“…Results and Discussion X-ray data on several such compounds reveal that ligand A is planar, with Sn(1), Sn (2) and Sn (3) Reaction of 3 with an excess of racemic (d,l)-2-methyl-1- Figure 1. General structure, with atom labelling, of compounds cohol than from a secondary one, probably due to steric from several condensation reactions between di-n-butyl or dimehindrance of the latter.…”