Organometallic complexes with biological molecules. XVIII. Alkyltin(IV) cephalexinate complexes: synthesis, solid state and solution phase investigations

Dialkyltin(IV) and trialkyltin(IV) complexes of the deacetoxycephalo-sporin-antibiotic cephalexin [7-(d-2-amino-2-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid] (Hceph) have been synthesized and investigated both in solid and solution phase. Analytical and thermogravimetric data supported the general formula Alk(2)SnOHceph(.)H(2)O and Alk(3)Snceph(.)H(2)O (Alk=Me, n-Bu), while structural information has been gained by FT-IR, (119)Sn M?ssbauer and (1)H, (13)C, (119)Sn NMR data. In particular, IR results suggested polymeric structures both for Alk(2)SnOHceph(.)H(2)O and Alk(3)Snceph(.)H(2)O. Moreover, cephalexin appears to behave as monoanionic tridentate ligand coordinating the tin(IV) atom through ester-type carboxylate, as well as through beta-lactam carbonyl oxygen atoms and the amino nitrogen donor atoms in Alk(2)SnOHceph(.)H(2)O complexes. On the basis of (119)Sn M?ssbauer spectroscopy it could be inferred that tin(IV) was hexacoordinated in such complexes in the solid state, showing skew trapezoidal configuration. As far as Alk(3)Sn(IV)ceph(.)H(2)O derivatives are concerned, cephalexin coordinated the Alk(3)Sn moiety through the carboxylate acting as a bridging bidentate monoanionic group. Again, (119)Sn M?ssbauer spectroscopy led us to propose a trigonal configuration around the tin(IV) atom, with R(3)Sn equatorial disposition and bridging carboxylate oxygen atoms in the axial positions. The nature of the complexes in solution state was investigated by using (1)H, (13)C and (119)Sn NMR spectroscopy. Finally, the cytotoxic activity of organotin(IV) cephalexinate derivatives has been tested using two different chromosome-staining techniques Giemsa and CMA(3), towards spermatocyte chromosomes of the mussel Brachidontes pharaonis (Mollusca: Bivalvia). Colchicinized-like mitoses (c-mitoses) on slides obtained from animals exposed to organotin(IV) cephalexinate compounds, demonstrated the high mitotic spindle-inhibiting potentiality of these chemicals. Moreover, structural damages such as "chromosome achromatic lesions", "chromosome breakages" and "chromosome fragments" have been identified through a comparative analysis of spermatocyte chromosomes from untreated specimens (negative controls) and specimens treated with the organotin(IV) complexes.     

Synthesis, structural investigations on organotin(IV) chlorin-e6 complexes, their effect on sea urchin embryonic development and induced apoptosis

Four new organotin(IV) chlorin derivatives, [chlorin=chlorin-e(6)=21H,23H-porphine-2-propanoic acid, 18-carboxy-20-(carboxymethyl)-8-ethenyl-13-ethyl-2,3-di-hydro-3,7,12,17-tetramethyl-(2S-trans)-], with formula (R(2)Sn)(3)(chlorin)(2).2H(2)O (R=Me, n-Bu) and (R(3)Sn)(3)chlorin.2H(2)O (R=Me, Ph) have been synthesized. The solid state and solution phase structures have been investigated by FT-IR, (119)Sn M?ssbauer, (1)H and (13)C NMR spectroscopy. In the solid state, (R(2)Sn)(3)(chlorin)(2).2H(2)O complexes contain six coordinated Sn(IV), in a skew trapezoidal environment by forming trans-R(2)SnO(4) polymeric units. As far as (R(3)Sn)(3)chlorin.2H(2)O complexes are concerned, Sn(IV) is five coordinated in a polymeric (oligomeric) trigonal bipyramidal environment and eq-R(3)SnO(2) units, in the solid state. In saturated solutions, a polymeric structure comparable to the solid phase, with carboxylate groups of the ligand behaving in monoanionic bidentate fashion bridging Sn(IV) atoms, was detected for the (Me(3)Sn)(3)chlorin.2H(2)O complex, while in more diluted ones a tetrahedral configuration for the trimethyltin(IV) moieties was observed. Cytotoxic activity of the novel organotin(IV) chlorin was investigated in order to assay the effect on sea urchin embryonic development. The results obtained demonstrated that (n-Bu(2)Sn)(3)(chlorin)(2).2H(2)O and (Ph(3)Sn)(3)chlorin.2H(2)O exerted the antimitotic effect on the early stages of sea urchin development. In addition, the cytotoxic effect exerted by (n-Bu(2)Sn)(3)(chlorin)(2).2H(2)O appeared with necrosis of the blastomeres, which were clearly destroyed. After treatment with (Ph(3)Sn)(3)chlorin.2H(2)O, a programmed cell death was triggered, as shown by light microscope observations through morphological assays. The apoptotic events in 2-cell stage embryos revealed: (i) DNA fragmentation, with the TUNEL reaction (terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling); (ii) phosphatidylserine translocation in the membrane, with Annexin-V assay and (iii) cytoplasm blebbing, with the TUNEL reaction. The results demonstrated that the novel compound (Ph(3)Sn)(3)chlorin.2H(2)O was the most toxic derivative, by exerting antimitotic effect very early and by triggering apoptosis in the 2-cell stage of sea urchin embryonic development.     

Spectral analysis and in vitro cytotoxicity profiles of novel organotin(IV) esters of 2-maleimidopropanoic acid

Six novel triorganotin(IV) 2-maleimidopropanoato complexes: R3SnOCOCH3(CH)(COCH)2, (R: Me(l), Et(2), n-Pr(3), n-Bu(4), Ph(5), Bz(6) have been synthesized. Their solid-state configuration has been determined by FT IR and lI9mSn M?ssbauer spectroscopy. The tin(IV) atom is five-coordinated in all the complexes with 2-maleimidopropanoic acid behaving as a monoanionic bidentate ligand coordinating the tin(IV) atom through a chelating or bridging carboxylate group. The solution-state configuration has been elucidated by means of 1H-, 13C- and 119Sn-NMR spectroscopy which assigned a tetrahedron. Elemental analysis and FAB MS data also supported a 1:1 metal to ligand stoichiometry. The title complexes have been screened in vitro for anti-tumour, anti-fungal, anti-leishmanial and urease inhibition activities and displayed promising results.     

Spectral analysis and in vitro cytotoxicity profiles of novel organotin(IV) esters of 2-maleimidopropanoic acid

Six novel triorganotin(IV) 2-maleimidopropanoato complexes: R₃SnOCOCH₃(CH)(COCH)₂, (R: Me(1), Et(2), n-Pr(3), n-Bu(4), Ph(5), Bz(6) have been synthesized. Their solid-state configuration has been determined by FT IR and ^119mSn Mössbauer spectroscopy. The tin(IV) atom is five-coordinated in all the complexes with 2-maleimidopropanoic acid behaving as a monoanionic bidentate ligand coordinating the tin(IV) atom through a chelating or bridging carboxylate group. The solution-state configuration has been elucidated by means of ¹H-, ¹³C- and ¹¹⁹Sn-NMR spectroscopy which assigned a tetrahedron. Elemental analysis and FAB MS data also supported a 1:1 metal to ligand stoichiometry. The title complexes have been screened in vitro for anti-tumour, anti-fungal, anti-leishmanial and urease inhibition activities and displayed promising results.     

Characterization of diorganotin(IV) complexes with captopril. The first crystallographically authenticated metal complex of this anti-hypertensive agent

Diorganotin(IV) complexes R(2)Sn(cap) (capH(2)=N-[(S)-3-mercapto-2-methylpropionyl]-L-proline; R=Me, Et, n-Bu and t-Bu) were prepared and characterised. The FTIR and Raman spectra demonstrated that the organotin(IV) moieties interact with the [S] atom of the ligand, while the other coordination sites are the carboxylate and the amide -CO groups. M?ssbauer Delta data showed that the diorganotin(IV) compounds adopt slightly distorted trigonal-bipyramidal (tbp) geometry. A single-crystal X-ray study was performed on the compound Me(2)Sn(cap): the Sn atom is five-coordinated in a distorted tbp environment, with two [O] atoms in the axial positions and the [S] and two [C] atoms in the equatorial (eq) plane. Each cap ligand coordinates to two different Sn atoms, and infinite zigzag chains are formed, directed parallel to each other and to the b axis of the unit cell. NMR (CDCl(3)) of the Me(2)Sn(IV) and n-Bu(2)Sn(IV) complexes indicated the presence of different oligomeric species.     

Self-assembled pentagonal bipyramidal and skew trapezoidal organotin(IV) complexes of substituted benzoic acids: Their antibacterial, antifungal, cytotoxic, insecticidal and urease inhibition activities

Fourteen di- and triorganotin(IV) derivatives with pentagonal bipyramidal and skew trapezoidal geometries have been synthesized and characterized. Dimethylstannyl bis[3-amino-4-chlorophenylcarboxylate] (1), bis[3-amino-4-chlorophenylcarboxylato] tetraethyldistannoxane] (2) and bis[3,5-dinitro-4-chlorophenylcarboxylato] tetra-n-butyldistannoxane (10) are dinuclear and tetranuclear complexes of bidentate ligands. The crystal structure of (1) is dimeric in which each Sn atom is seven coordinated. Study of weak intramolecular Sn?O interactions is very important to decide geometry around tin. Furthermore, it has been investigated that these compounds exhibit fairly good antibacterial, antifungal, cytotoxic, insecticidal and antiurease activities.     

Polynuclear diorganotin(IV) complexes with arylhydroxamates: Syntheses, structures and in vitro cytotoxic activities

Series of polynuclear diorganotin(IV) complexes with di-halogenbenzohydroxamate ligands (substituents=2,4-Cl(2), 2,4-F(2), 3,4-F(2), 2,5-F(2), 2,6-F(2)), formulated as the polymeric [R(2)SnL](n)a (1:1) and the tetranuclear [R(4)Sn(2)(HL)(2)(L)](2)b (2:3) (HL=arylhydroxamate), were prepared and characterized by FT-IR, (1)H, (13)C, (119)Sn NMR spectroscopies, elemental analyses and melting point measurements. X-ray diffraction analyses were also carried out for the representative complexes [Me(2)Sn{2,4- F(2)C(6)H(3)C(O)NO}](n)2a and [n-Bu(4)Sn(2){2,4- F(2)C(6)H(3)C(O)NHO}(2) {2,4-F(2)C(6)H(3)C(O)NO}] (2)1b and show that the ligated mono- and di-basic forms, HL and L, of the arylhydroxamic acid (H(2)L) display the oxamic and oximic tautomeric forms, respectively. These compounds exhibit in vitro cytotoxicities toward human leukemic promyelocites HL-60, BGC-823, BEL-7402 and KB cell lines which, in some cases, are identical to, or even higher than, that of "cisplatin". The polymeric diorganotin/hydroxamato complexes a containing the long carbon chain butyl ligands are the most active ones, and the dependence of the antitumor activity of the complexes on various factors, namely the nuclearity, the organic ligand, the type, position and number of the X ring substituents, is also discussed.     

Synthesis, structural characterization and biological study of new organotin(IV), silver(I) and antimony(III) complexes with thioamides

An overview of our work on the synthesis and biological activity of a series of tin(IV), silver(I) and antimony(III) complexes with thioamides is reported. Organotin(IV) complexes of formulae (n-Bu)2Sn(MBZT)2 (1), Me2Sn(CMBZT)(2) (2), {(Ph3Sn)2(MNA) (Me2CO)} (3), Ph3Sn(MBZT) (4), Ph3Sn(MBZO) (5), Ph3Sn(CMBZT) (6), Ph2Sn(CMBZT)2 (7) and (n-Bu)2Sn(CMBZT)2 (8), Me2Sn(PMT)2 (9), (n-Bu)2Sn(PMT)2 (10), Ph2Sn(PMT)2 (11), Ph3Sn(PMT) (12) {where MBZT=2-mercapto-benzothiazole, CMBZT=5-chloro-2-mercapto-benzothiazole, H2MNA=2-mercapto-nicotinic acid, MBZO=2-mercapto-benzoxazole and PMTH=2-mercapto-pyrimidine} were characterized by spectroscopic (NMR, IR, Mossbauer, etc.) and X-ray diffraction techniques and their influence on the peroxidation of oleic acid was studied. They were found to inhibit strongly the peroxidation of linoleic acid by the enzyme lipoxygenase. In addition, organotin(IV) complexes were found to exhibit stronger cytotoxic activity in vitro, against leiomyosarcoma cells, than cisplatin. The antiproliferative activity of the organotin complexes studied, against leiomyosarcoma cells follow the same order of LOX activity inhibition. This is, 3>12>7>6 approximately 8 approximately 10>5 approximately 4>2>9. Thus, among organotin(IV)-CMBZT complexes, 7 exhibits higher activity than the others and this is explained by a free radical mechanism, as it is revealed by an EPR study. The results are compared with the corresponding ones found for the silver(I) complexes of formulae complexes {[Ag6(mu3-HMNA)4(mu3-MNA)2](2-).[(Et(3)NH)+]2.(DMSO)2.(H2O)} (13), {[Ag4Cl4(mu3-STHPMH2)4]n} (14), {[Ag6(mu2-Br)6(mu2-STHPMH2)4(mu3-STHPMH2)2]n} (15), {[Ag4(mu2STHPMH2)6](NO3)4}(n) (16), {[AgCl(TPTP)]4} (17), [AgX(TPTP)3] with X=Cl (18), Br (19), I (20) (where STHPMH2=2-mercapto-3,4,5,6-tetrahydro-pyrimidine, TPTP=tri(p-toly)phosphine) and those of antimony(III) complexes {[SbCl2(MBZIM)4](+).Cl(-).2H2O.(CH3OH)} (21), {[SbCl2(MBZIM)4]+.Cl(-).3H2O.(CH3CN)} (22), [SbCl3(MBZIM)2] (23), [SbCl3(EMBZIM)2] (24), [SbCl3(MTZD)2] (25), {[SbCl3(THPMT)2]} (26) and {[Sb(PMT)3].0.5(CH3OH)} (27) (where MBZIM is 2-mercapto-benzimidazole, EMBZIM=5-ethoxy-2-mercapto-benzimidazole and MTZD is 2-mercapto-thiazolidine), which they have characterized with similar techniques as in case of organotin(IV) complexes. Silver(I) and antimony(III) complexes were found to be cytotoxic against various cancer cell lines.     

Synthesis,characterization and in vitro cytotoxicity of new organotin(IV) derivatives of N-methylglycine

The synthesis and characterization of new coordination compounds of some diorganotins(IV) with N-methylglycine (sarcosine) are reported; all these derivatives mainly tend to assume a chelate structure. As single crystals were not obtained, a large number of experimental techniques were used to accomplish a definitive characterization and determination of their structure. Results obtained by (1)H/(119)Sn NMR, FT-IR and (119)mSn-M?ssbauer spectroscopy and thermogravimetric analysis allow us to deduce the pentacoordination for 1:1 (Sn/sarcosine) derivatives [R(2)SnCl(2)(Sar)](+)Cl(-) (R=Me, n-Bu) in a trigonal-bipyramidal structure, and the hexacoordination for 1:2 complexes [R'(2)Sn(Sar)(2)](2+)2Cl(-) (R'=Me, n-Bu, Ph) in an octahedral structure; however, the probability of partially or totally non-chelate structures for some adducts increases with the steric hindrance of the R/R' groups and the number of the sarcosine molecules bound to the tin atom, so that they give rise to fluxional equilibria in solution. Finally, the synthesized compounds have been tested for in vitro cytotoxic activity against human adenocarcinoma HeLa cells showing, in some cases, strong activity even at low concentration.     

Synthesis, characterization and biological activity of triorganotin 2-phenyl-1,2,3-triazole-4-carboxylates

The triorganotin 2-phenyl-1,2,3-triazole-4-carboxylates, 2-PhC2N3CO2SnR3 (R=C6H5, 1; c-C6H11, 2; C6H5C(CH3)2CH2, 3), have been prepared and characterized by means of elemental analysis, IR and NMR (1H, 13C and 119Sn) spectroscopy. The crystal structures of 1 and 3 have been determined. Compound 1 is polymeric in nature with a trigonal bipyramidal configuration, and compound 3 shows a tetrahedral geometry. Bioassay results have shown that these compounds have good antibacterial and antitumor activity. The activity against three human tumor cell lines (HeLa, CoLo205 and MCF-7) decreased in the order 1>2>3.     

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.     

Potentiometric and spectroscopic studies on the dimethyltin(IV) complexes of 2-hydroxyhippuric acid

Equilibrium and spectroscopic (1H, 13C NMR and 119Sn M?ssbauer) studies in aqueous solution are reported for dimethyltin(IV) complexes of 2-hydroxyhippuric acid (Sal-Gly). Below pH 4, oxygen-coordinated complexes MLH and ML are formed. In the pH range 5-8.5, the species MLH(-1), predominates at any metal-to-ligand ratio. The ligand exchange of this species is slow on the NMR time scale, which allows its structural characterization by NMR spectroscopy: the coordination polyhedron around the tin atom is distorted trigonal bipyramidal, with tridentate [O-,N-,COO-] coordination of Sal-Gly, involving two equatorial methyl groups. The NMR results reveal that the main cause of the distortion of the polyhedron is the large CH3-Sn-CH3 angle of 136+/-4 degrees. The presented results supplement the data available on the dimethyltin(IV)-promoted amide deprotonation of peptides, and provide further arguments for the fundamental role of the carboxylate as an anchoring group in this process.     

Diorganotin(IV) N-acetyl-l-cysteinate complexes: Synthesis, solid state, solution phase, DFT and biological investigations

Diorganotin(IV) complexes of N-acetyl-l-cysteine (H₂NAC; (R)-2-acetamido-3-sulfanylpropanoic acid) have been synthesized and their solid and solution-phase structural configurations investigated by FTIR, Mössbauer, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. FTIR results suggested that in R₂Sn(IV)NAC (R = Me, Bu, Ph) complexes NAC²⁻ behaves as dianionic tridentate ligand coordinating the tin(IV) atom, through ester-type carboxylate, acetate carbonyl oxygen atom and the deprotonated thiolate group. From ¹¹⁹Sn Mössbauer spectroscopy it could be inferred that the tin atom is pentacoordinated, with equatorial R₂Sn(IV) trigonal bipyramidal configuration. In DMSO-d₆ solution, NMR spectroscopic data showed the coordination of one solvent molecule to tin atom, while the coordination mode of the ligand through the ester-type carboxylate and the deprotonated thiolate group was retained in solution. DFT (Density Functional Theory) study confirmed the proposed structures in solution phase as well as the determination of the most probable stable ring conformation. Biological investigations showed that Bu₂SnCl₂ and NAC2 induce loss of viability in HCC cells and only moderate effects in non-tumor Chang liver cells. NAC2 showed lower cytotoxic activity than Bu₂SnCl₂, suggesting that the binding with NAC²⁻ modulates the marked cytotoxic activity exerted by Bu₂SnCl₂. Therefore, these novel butyl derivatives could represent a new class of anticancer drugs.     

Structural investigations on diorganotin and triorganotin(IV) phosphomycin derivatives

Four new diorganotin(IV), (R = Me, Bu), and triorganotin(IV), (R = Me, Ph), derivatives of the phosphomycin disodium salt antibiotic[(1R,2S)-1,2-epoxypropylphosphonate]Na₂ have been synthesized and their solid state configuration studied by X-ray crystallography, FT-IR, Mössbauer, UV-Vis spectroscopies. The X-ray diffraction investigation, performed on the bis[trimethyltin(IV)]phosphomycin, showed that the coordination geometry at all the Sn atoms is trigonal bipyramidal. The structure of the complex forms an unusual polymeric zig-zag planar network. The FT-IR and the ¹¹⁹Sn Mössbauer studies supported the formation of trigonal bipyramidal (Tbp) molecular structures, both in the diorganotin(IV) and triorganotin(IV) derivatives, even if, in the case of diorganotin(IV) derivatives, the tetrahedral structure cannot be a priori excluded. The group of phosphomycin coordinates the organotin(IV) centers originating a monodimensional polymeric network, as inferred by variable temperature ¹¹⁹Sn Mössbauer spectroscopy, used to investigate lattice dynamics of the bis-[trimethyltin(IV)]phosphomycin complex.     

Interaction of Et2SnCl2 with 5'-IMP and 5'-GMP

The interactions of Et2SnCl2 with 5'-IMP and 5'-GMP have been studied in aqueous solutions by 1H- and 31P-NMR spectroscopy as a function of pH. At low pH values (< 4.0) Sn(IV) interacts with the pyrophosphate oxygens of these nucleotides. At intermediate pH values (4-9.5) no interaction of the metal with the nucleotides take place, while at pH > 9.5 the sugar O'2 and O'3 atoms are the preferred coordination sites. In addition, the solid adducts obtained from aqueous solutions at pH = 3-4 of the above interactions correspond to formulae; (Et2Sn)2(5'-IMP)2(H2O) and (Et2Sn)3(5'-GMP)2(OH)2(H2O)2 as their elemental analysis show. IR spectra and solid state 13C, 31P-NMR spectra 119Sn M?ssbauer and solution 119Sn-NMR spectra once more confirm the pyrophosphate involvement in bonding with Sn(IV) in oligomeric or polymeric structures and trigonal bipyramidal or octahedral geometries.     

New mononuclear organotin(IV) 4-benzhydrylpiperazine-1-carbodithioates: Synthesis, spectroscopic characterization, X-ray structures and in vitro antimicrobial activities

A new series of organotin(IV) complexes with 4-benzhydrylpiperazine-1-carbodithioate (L) were synthesised by the metathesis reactions of the ligand-salt with triorganotin(IV) chlorides and diorganotin(IV) dichlorides in the appropriate molar ratio. All the complexes were characterized by elemental analysis, Raman, IR, and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy. Solid-state studies (Raman, IR and X-ray analysis) confirmed the bidentate coordination of the ligand in all cases. Multinuclear NMR spectroscopy suggested that some tri- and diorganotin complexes reduce their geometry by one unit in solution. The τ values, 0.6 and 0.24 for chlorodibutyl- and chlorodiethyltin(IV) derivatives, respectively, authenticated the trigonal bipyramidal geometry for the first complex and distorted square-pyramidal geometry for the latter. The low τ value for the chlorodiethyltin(IV) complex is attributed to the additional Sn···Cl and Sn···S intermolecular interactions. The antimicrobial results indicated the compounds are active biologically.     

Di- and triorganotin(IV) carboxylates derived from triorganotin(IV) iodide with mixed organic groups on tin: Cyclic, hexameric triorganotin(IV) carboxylates

The reaction of ethyldiphenyltin(IV) iodide with silver benzoate in ethanol results in the formation of bis(benzoato)ethylphenyltin(IV), EtPhSn[OC(O)C₆H₅]₂ (1), by the cleavage of a phenyl group bound to tin. The reaction of ethyldiphenyltin(IV) iodide with silver acetate provides acetatoethyldiphenyltin(IV), EtPh₂SnOC(O)CH₃ (2). Similarly, the reaction of diphenylpropyltin(IV) iodide with silver acetate affords acetatodiphenyl-n-propyltin(IV), Ph₂PrSnOC(O)CH₃ (3). These three complexes were characterized by elemental analysis, mass spectrometry, and infrared spectroscopy (IR), as well as ¹H, ¹³C, and ¹¹⁹Sn NMR. The molecular structures of three complexes were also verified by single-crystal X-ray analyses. The X-ray structures show that 1 adopts a skew-trapezoidal bipyramidal structure, while 2 and 3 are rare, cyclic hexameric structures.     

Synthesis, characterizations, and crystal structures of triorganotin(IV) derivatives with areneseleninic acids

Six new triorganotin(IV) complexes, [R₃Sn(O₂SeC₆H₄Cl)]_n (R = Me 1; Ph 2), [R₃Sn(O₂SeC₆H₄Me)]_n (R = Me 3; Ph 4), [R₃Sn(O₂SeC₆H₄Bu)]_n (R = Me 5; Ph 6) have been synthesized by the reaction of 4-chlorobenzeneseleninic acid, p-Tolueneseleninic acid, and 4-tert-butylbenzeneseleninic acid with triorganotin(IV) chloride in the presence of sodium ethoxide. All of the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy, and X-ray crystallography. Crystal structures show that all of the complexes exhibit 1D infinite chain structures which are generated by the bidentate oxygen atoms and the five-coordinated tin centers.     

The local structure of solid diorganotin(IV) complexes formed with carbohydrates by X-ray absorption spectroscopy

Diethyltin(IV) complexes formed with carbohydrate ligands (aldoses, polyalcohols, sugar acids and disaccharides) containing the diethyltin(IV) moiety and the carbohydrate ligand in a 1:1 ratio were prepared. Their local structures were determined by extended X-ray absorption fine structure (EXAFS) in the solid state. The results showed that the dioxastannolane units are associated into an infinite chain polymer, in which tin(IV) is bound by two carbon atoms and three or four oxygen atoms either in highly distorted octahedral and trigonal bipyramidal arrangements or in a purely trigonal bipyramidal arrangement. The present structure models are consistent with the results of previous Mössbauer studies, proving the advantages of the use of the partial quadrupole splitting concept for the determination of the symmetry of the coordination sphere in tin(IV) organic complexes.     

Synthesis, characterization and crystal structures of homo- and hetero-substituents containing trans six-coordinate tin(IV) complexes of H2tmtaa (5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine), and the solid state NMR spectra study of Sn

The reaction of Sn(tmtaa)Cl₂ (H₂tmtaa=5,14-dihydro-6,8,15,17-tetramethyldi-benzo[b,i][1,4,8,11]tetraazacyclotetradecine) and ammonium thiocyanate or sodium azide under a mild condition resulted in trans six-coordinate tmtaa tin(IV) complexes, Sn(tmtaa)X₂ (X=NCS, 1; X=N₃, 2). However, the treatment of Sn(tmtaa)Cl₂ and sodium picrate produced Sn(tmtaa)(Cl)(OC₆H₂ (2,4,6-3NO₂)) (3). Only one chloro atom of Sn(tmtaa)Cl₂ was substituted because of low nucleophilicity of the 2,4,6-trinitrophenolic anion in 3. Furthermore, because of the steric hindrance between the 2,4,6-trinitrophenolic group and the tmtaa ligand, which has a non-planar, saddle-shaped conformation, two chloro atoms cannot be substituted by two 2,4,6-trinitrophenolic groups simultaneously. All complexes were characterized by IR spectra, UV spectra, mass spectra, NMR spectra and elemental analyses, as well as DSC measurements. X-ray crystal structures of 1 and 3 reveal that the complexes retain the characteristic saddle-shaped configuration of H₂tmtaa but have adopted the trans geometry. Solid state ¹¹⁹Sn NMR spectroscopy was used to study the bonding environment in the series of six-coordinate trans Sn(IV) tmtaa complexes. It can be found that the ¹¹⁹Sn chemical shifts of the Sn(IV) tmtaa complexes are almost not influenced by the substituents.