V. G. Kumar Das

Additive model for 119Sn Mössbauer quadrupole splitting in five-co-ordinate organotin(IV) compounds

Mossbauer parameters are reported for ten cationic organotin(IV) complexes of type [R3SnL2][BPh4](R = alkyl or phenyl, L = electrongegative ligand). Details are given of a regression method which is used to distinguish structural isomers of trigonal-bipyramidal [R3SnL2] species by their 119Sn quadrupole splittings. By use of new and literature data, partial quadrupole splitting (p.q.s.) parameters are calculated for a variety of ligands in trigonal-bipyramidal structures. Comparison of theory with experiment indicates that the additive model gives a consistent account of the relationship between quadrupole splitting and stereochemistry in trigonal-bipyramidal organotin(IV) compounds. The 119Sn parameters are used to calculate p.q.s. parameters for 121SbV, thus extending recent work on application of the additive model to five-co-ordinate organoantimony(V) compounds.

Crystal structure of tribenzyl(2-pyridinethiolato-N-oxide)tin(IV): a rare example of a square pyramidal organotin(IV) compound

Abstract Tribenzyl(2-pyridinethiolato-N-oxide)tin(IV), [(C6H5CH2)3Sn(2-SC5H4NO)], crystallizes in space group P ,with a 9.169(2), b 10.498(3), c 13.511(4) A, α 91.54(2), β 104.61(2), γ 112.49(2)° and Z = 2. The structure has been refined to R = 0.028 using 4593 observed Mo-Kα reflections. The molecule adopts a configuration displaced 91% from a trigonal bipyramid to a square pyramid along the Berry pseudorotation pathway. The basal plane is composed of the oxygen and sulfur atoms of the chelating 2-pyridinethiolato ligand and the carbon atoms of two benzyl groups [SnO 2.261(2), SnS 2.577(1), SnC 2.189(3), 2.196(3) A]. The apical tincarbon bond [SnC 2.167(3) A] is shorter than the other two tincarbon bonds. The tin atom is displaced 0.64(1) A from the basal plane in the direction of the apical carbon [sum of the basal angles = 341.7(4)°] and the CapicalSn Lbasal angles are in the range 100.1(1)–110.1(1)°. The unusual geometry of tribenzyl(2-pyridinethiolato-N-oxide)tin(IV) provides the first example of polytopal dominance of the square-pyramidal configuration in pentacoordinated organotin compounds.

Preparation and spectroscopic studies of tri(p-tolyl)tin(IV) compounds. X-Ray crystal structure of the quinoline-N-oxide adduct of tri(p-tolyl)tin(IV) bromide

Syntheses and spectroscopic data are presented for R3SnIV compounds, where R is predominantly p-tolyl, of the following types: R3SnX·L (X = Cl, Br or NCS; L = neutral, monodentate oxygen donor), R3SnY (YH = 1,2,4-triazole, N-phenyl-N-benzoylhydroxamic, succinanilic, levulinic and hippuric acids) and [R3SnL2]+ [Ph4B]− (L = neutral, monodentate or 1/2 bidentate oxygen donor). The spectroscopic data (IR and Mossbauer) are interpreted in terms of discrete or weakly polymeric trigonal bipyramidal structures, with the R3Sn skeleton forming the equatorial plane for most of the compounds. A cis-geometry is inferred for the case where the anionic residue is the chelating N-phenyl-N-benzoylhydroxamate ligand, while a meridional geometry is predicted for the cationic complexes involving the chelating ligans, 2,2′-bipyridine N,N′-dioxide and ethylenebis(diphenylphosphine oxide). Both the 13C NMR and the IR data suggest that the Lewis acceptor strength falls in the order (p-ClC6H4)3Sn > (C6H5Sn> (p-MeC6H4)3Sn. Crystals of (p-tolyl)3SnBr· quinoline-N-oxide are triclinic, space group P1, with a 10.245(4), b 10.862(2), c 13.153(5) A, α 84.10(2), β 68.39(3), γ 80.88(3)°. The structure was refined to R = 0.070 for 4548 observed Mo-Kα reflections and comprises independent, non-interacting molecules which are pentacoordinate at tin. The quinoline-N-oxide ligand is coordinated apically to tin in the trigonal-bipyramidal unit; the three tolyl rings occupy the trigonal plane but the tin atom is displaced by 0.17(1) A towards the other apical bromide ligand.

Organostannate derivatives of dicyclohexylammonium hydrogen 2,6-pyridinedicarboxylate: solution/solid-state 13C,119Sn NMR and in vitro antitumour activity of bis(dicyclohexylammonium) bis(2,6-pyridinedicarboxylato)dibutylstannate, and the crystal structure of its monohydrate

Bis(dicyclohexylammonium) bis(2,6-pyridine-dicarboxylato)dibutylstannate is assigned seven-fold coordination at tin on the basis of its ll9 Sn CP/MAS NMR chemical shift (δ=-424.9 ppm). The assignment has been corroborated by a crystal structure determination of its monohydrate, whose tin atom has the trans-C 2 SnNO 4 pentagonal bipyramidal [Sn-C=2.040(9), 2.067(8) A; C-Sn-C =168.9(5)°] geometry. One 2,6-pyridine-dicarboxylato group chelates to the tin atom (Sn-O=2.234(4), 2.260(4); Sn-N = 2.279(5) A) whereas the other binds through only one carboxyl -C0 2 end (Sn-O=2.416(5), 2.441(5)A). Hydrogen bonds link the cation and the stannate into a linear chain parallel to the b-axis. The lattice water molecule is hydrogen-bonded to the free carboxyl end. The anhydrous compound showed higher in vitro antitumor activity than those of carboplatin and cisplatin when screened against breast (MCF-7, EVSAT), colonic (WiDr), ovarian (IGROV) and renal (A498) carcinoma, and melanoma (M19 MEL) cell lines.

Six-coordinate tin in a dialkylchlorooxinatotin(IV) complex: skew-trapezoidal bipyramidal bis(2-carbomethoxyethyl)chloro(quinolin-8-olato)tin(IV)

Bis(2-carbomethoxyethyl)chloro(quinolin-8-olato)tin(IV), C17H20ClNO5Sn, crystallizes in the triclinic space group P1, with a 7.9001(7), b 10.2636(7), c 12.8287(9) A; α 108.575(7), β 98.564(6), γ 96.469(7)°; V 960.69 A3, Z = 2. The coordination geometry around the tin atom approximates to a skew-trapezoidal bipyramid, with the carbonyl oxygen of one of the 2-carbomethoxyethyl groups intramolecularly bonded to the tin (SnO 2.847(4) A). This oxygen atom, the nitrogen and oxygen atoms of the chelating quinolin-8-olato ligand (SnN 2.370(4), SnO 2.040(4) A; NSnO 74.4(1)°), and the chlorine atom (SnCl 2.454(2) A), occupy the four corners of a trapezoid around the metal atom. The two apical tincarbon bonds (SnC 2.122(6), 2.143(7) A), which are skewed towards the long edge (defined by the carbonyl oxygen and nitrogen atoms) of the trapezoidal plane, subtend an angle of 135.4(3)° at tin.

Group IV organometallic compounds. : IX. Preparation and spectroscopic studies of complexes of bis(β-carbomethoxyethyl)tin dichloride

Abstract Bis(β-carbomethoxyethyl)tin dichloride forms coordination complexes of formula R 2 SnCl 2 L 2 , R 2 SnL′ 2 and R 2 SnCl(oxin) where L 2 = 2Ph 3 AsO, phen, bipy and L′ = oxin, . However, it exhibits weaker acceptor properties towards other ligands including phosphine oxides. Structural features of the isolated complexes both in the solid state and in solution are discussed based on spectral (IR, UV, NMR, Mossbauer) evidence.

Preparation and characterization of triorganotin(IV) derivatives of mercaptocarboxylic acids. Crystal structure of [O,S-bis(triphenyltin(IV))-2-mercaptobenzoate]

Abstract The syntheses and tin-119m Mossbauer spectroscopic data are reported for the tri-n-butyl-, tricyclohexyl- and triphenyltin(IV) derivatives of mercaptoacetic and 2-mercaptobenzoic acids. A four-coordinate tetrahedral geometry at tin is assigned for (cyclo-C 6 H 11 ) 3 SnSCH 2 C(O)OH and for the (C 6 H 5 ) 3 SnSCH 2 C(O)O − and (C 6 H 5 ) 3 SnSC 6 H 4 C(O)O − anions, isolated as the dicyclohexylammonium and iso- S -benzylthiuronium salts, respectively. The sulfidotin in R 3 SnSCH 2 C(O)OSnR 3 and R 3 SnSC 6 H 4 C(O)OSnR 3 is also four-coordinate, but the carboxylatotin is four-coordinate for R = C 6 H 5 and five-coordinate for R = n-C 4 H 9 . The Mossbauer quadrupole splitting in the butyltin case indicates a trans -C 3 SnO 2 trigonal bipyramidal configuration. The coordination assignment for the two tin atoms in bis(triphenyltin)-2-mercaptobenzoate is confirmed by X-ray crystallography. The compound crystallizes in space group P 2 1 / c with a 14.293(4), b 17.456(2), c 15.624(1) A, β 107.40(1)°; Z = 4. The structure was refined to an R factor of 0.035 for 5837 observed reflections. The carbonyl oxygen of the molecule is positioned roughly halfway between the carboxylatotin (Sn ⋯ O 2.765(3) A and sulfidotin (Sn ⋯ S 3.016(1) A, disorting somewhat the tetrahedral geometries at both tin sites.

Mössbauer and NMR studies of intramolecular coordination in thienyltetraorganotin(IV) compounds, and the x-ray crystal structure of {C,N-[3-(2-pyridyl)-2-thienyl]} tri(p-tolyl)tin(IV)

Abstract Tetraorganotin(IV) compounds containing the [3-(2-pyridyl)-2-thienyl] group (L), of formula R 3 SnL ( 1 : R = p -tolyl; 2 : R = Ph; 3 : R = p -ClC 6 H 4 ; 4 : R = cyclo-C 5 H 9 ; 5 ; R = cyclo-C 6 H 11 ) have been synthesized and their structures examined by 119m Sn Mossbauer and NMR ( 119 Sn and 13 C modes) spectroscopic techniques, and in the case of compound 1 by X-ray analysis. Compound 1 crystallises in the space group C 2/ c with a 20.85(1), b 9.521(1), c 26.69(1) A; β 95.37(3)°; V 5274(3) A 3 ; Z = 8. Its structure was solved by the heavy-atom method from 4251 observed MO- K α data and refined to R = 0.068. The coordination environment at tin in the compound is best described as a pseudo-trigonal bipyramid, involving a waek intramolecular SnN bond of distance 2.841(7) A. This view is supported by the observation of partially-resolved Mossbauer spectra for compounds 1–5 (QS 0.57–0.96 mm s −1 ) which is not evidenced, on the other hand, for (2-thienyl)SnR 3 compounds ( 7 : R = p -tolyl; 8 : R = Ph), as well as by similar comparisons of data on 119 Sn chemical shifts (−176.3 ppm for 1 relative to −135.5 ppm fr 8 ) and one-bond coupling constants, 1 J ( 119 Sn- 13 C(1)), where C(1) = ipso -carbon of the aryl group or α-carbon of the cycloalkyl group (647.5 Hz for 1 , 726.6 Hz for 2 and 786.2 Hz for 3 relative to 536.9 Hz for 7 ).

Structural studies on octahedral diorganotin (IV) complexes: the influence of substituents in carbon- and heteroatom-donor ligands on [SnR2] skeletal geometry

The synthesis and spectroscopic characterization are described of six-coordinated diorganotin(IV) complexes of the type RR′SnX2·L2 and RR′SnL′2 where RR′ = diphenyl, bis(p-tolyl), bis(m-chlorophenyl), bis(p-chlorophenyl), MeEt, Et(n-Pr); X  Cl or NCS; L = neutral monodentate oxygen donor (containing , , or grouping) or 12 bidentate donor (2,2′-bipyridyl, 4,4′-dimethyl-2,2′-bipyridyl, 1,10-phenanthroline or 3,4,7,8-tetramethyl-1,10-phenanthroline); L′ = 8-quinolinolato or 2-methyl-8-quinolinolato. The spectroscopic (in particular, the 119mSn Mossbauer) data have been used to infer the stereochemistry of the [SnR2] skeleton in these complexes, with confirmation from recent X-ray studies in a few cases. The results indicate that substituents in the carbon- and heteroatom-donor ligands attached to tin have a strong influence on the stereochemical preference for trans- or cis-[SnR2] configurations in the six-coordinated octahedral complexes.

Synthesis of triorganostannate esters of dicarboxylic acids. Crystal structure of bis(dicyclohexylammonium) trisoxalatotetrakis(tri-n-butylstannate) · 2 ethanol

Abstract Triphenyltin hydroxide has been shown to react with dicyclohexylammonium oxalate to give [(cyclo-C6H11)2NH2]+ [(C6H5)3SnOC(O)C(O)O]−, and to give with dicyclohexylammonium malonate [(cyclo-C6H11)2NH2]+ &{;[(C6H5)3SnOC(O)CH2C(O)O]2H&0;−. Bis(tri-n-butyltin) oxide afforded 2[(cyclo-C6H11)2NH2]+ &{;[(n-C4H9)3Sn]4[OC(O)CH2C(O)O]3{2− on treatment with dicyclohexylammonium malonate, but with dicyclohexylammonium oxalate it yielded a stannate which crystallized with two molecules of ethanol. A low-temperature X-ray diffraction study of this ethanol-containing stannate, 2[(cyclo-C6H11)2NH2]+ [C2H5OH · (n-C4H9)3SnOC(CO2)(O)(n-C4H9)3SnOC(O)]22− revealed the presence of centrosymmetric chains, each consisting of four [(n-C4H9)3Sn]+ cations linked by three [OC(O)C(O)]2− anions. The chains are hydrogen bonded by [(cyclo-C6H11)2NH2]+ cations and ethanol molecules into a three-dimensional lattice. The geometry around the ethanol-coordinated (SnO 2.465(4) A) terminal tin atom is essentially a trans-C3SnO2 trigonal bipyramid, but is distorted towards a C3SnO3 skew-trapezoidal bipyramid; the tin atom is part of a five-membered SnOCCO ring in which the OSnO angle is 63.4(1)° and SnO distances are 2.191(3) and 2.890(3) A. The geometry around the inner tin atom is a less distorted trans-C3SnO2 trigonal bipyramid; the four SnOCO (Sn ··· O 3.043(3) A) atoms do not form a ring owing to the small chelate bite.