Influence of the transannular interaction in spiro-heterocycles containing Ge(IV) and Sn(IV). A comparative study

[D(CH₂CH₂S)₂]M(XCH₂CH₂Y) 1-8 (M = Ge, Sn; D = O, S; X = Y = S, O and X = S, Y = O) spirocycles were synthesized to analyze the influence of the metal center replacement and the donor atom hardness on the strength of the transannular bond and the hypercoordination phenomena. The compounds were characterized by IR, Raman and NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy, E.I. mass spectrometry and elemental analysis. The molecular and crystal structures of compounds 3, 4, 6-8 and Ge(SCH₂CH₂S)₂ (9) were obtained by X-ray diffraction analyses. They all exhibit five-coordinate central atoms due to transannular metal coordination (M?D) except 4, which displays a dimeric structure formed by the fusion of two five-membered rings resulting in a cyclic-distannoxane unit, {[O(CH₂CH₂S)₂]Sn(SCH₂CH₂O)}₂. The relationship between the nature of the metal center and the differences found between the two germanium and tin series are discussed.     

Studies of the reaction of dimethyltin dichloride with mercaptoacetic acid in the presence of amines and crystal structure of [(n-Pr)3NH][Me2Sn(μ-SCH2COO)Cl]

A series of new five-coordinated ionic organotin(IV) complexes with general formula [Q][Me₂Sn(μ²-SCH₂COO)Cl](Q = diethylammonium, triethylammonium, di-i-propylammonium, tripropylammonium, tri-n-butylammonium, pyrimidium, 3-picolinium, methylphenylammonium, dimethylphenylammonium) were synthesized by the reaction of mercaptoacetic acid with dimethyltin dichloride in the presence of an organic base. These complexes have been characterized by elemental analyses, IR and ¹H NMR spectroscopies. The crystal structure of [(n-Pr)₃NH][Me₂Sn(μ²-SCH₂COO)Cl] was determined by X-ray crystallography. The structure consists of an anion part, and a tri-n-propylammonium cation part as a counterion. The tin atom has a distorted cis-tbp geometry with two carbon and one sulfur atoms occupying the equatorial positions and the O atom and Cl atom occupying the axial positions. The organotin anion and its counterion are connected through a hydrogen bond between the N atom in the ammonium and the O atom of the carbonyl group with a N-O length of 2.766 Å.     

Pentacoordination at antimony in dibenzostibocines via D–Sb transannular interactions (D = O,S): A structural study

Addition of M₂SCN(CH₂R)₂ to D(C₆H₄S)₂SbCl in methylene chloride solution leaded to the formation of the stable compounds D(C₆H₄S)₂SbS₂CN(CH₂R)₂ (D = O, R = Me, 1; D = S, R = Me, 2; R = Ph, 3). The new dibenzostibocines derivatives containing two different types of dithioligands were characterized by elemental analysis and spectroscopic studies (IR, ¹H and ¹³C NMR). Single crystal X-ray diffraction determinations of complexes 1–3 revealed that the antimony atom acts as an acceptor atom exhibiting an intramolecular transannular interaction with the donor D atom, expanding its coordination from three to five and displaying a skew trapezoidal local geometry.     

Synthesis and spectral characterization of stannocanes of the type [O(CH2CH2S)2SnR2](R=Me1,Bun2,Ph3)

The stannocanes of the type [O(CH₂CH₂S)₂SnR₂](R=Me1,Buⁿ 2,Ph3) have been synthesized in an improved method by the reaction of R₂SnCl₂ with 2, 2′-oxydiethanethiol O(CH₂CH₂SH)₂ in molar ratio of 1:1 at the presence of sodium ethoxide in anhydrous ethanol. The reactions are carried out under inert atmosphere. These compounds have been extensively characterized by FT-IR, UV-Vis spectrophotometry, multi-nuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, elemental analysis and mass spectrometry. The obtained data clearly indicates that, there is a strong interaction between oxygen atom of the ligand as a donor and Sn atom of the organotin species as a Lewis acid acceptor. Therefore, the resulted dithiostannocanes possess a transannular secondary bonding and hypervalency at the central Sn atom which leads to an increase in the coordination number of tin from four to five-coordinated tin.      

Syntheses and characterizations of diorganotin(IV) complexes with L‐cysteine: Crystal structure of [(CH3)2Sn(L‐C3H5NO2S)· H2O]

Five diorganotin(IV) derivatives of L‐cysteine have been synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, and IR spectroscopies along with elemental analyses. The diorganotin(IV) complexes were readily obtained from the reactions of diorganotin(IV) dichlorides and L ‐cysteine. The crystal structure of [(CH₃)₂Sn(L ‐C₃H₅NO₂S)·H₂O] contains a one dimensional infinite “S” conformation polymeric chain, with the L ‐cysteine acting as a bridged tridentate ligand. The tin(IV) atom, bonding to two methyl carbons, amino nitrogen atom, thiol sulfur atom, and carboxylate oxygen atom, has a five‐coordinated trigonal bipyramid environment. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:636–641, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10218     

Structure and spectroscopy of diorganotin(IV) complexes derived from N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide

Three new diorganotin(IV) complexes of the general formula R₂Sn[3-(OMe)-2-OC₆H₃CHN-NC(O)Ph] (R = Ph, Ia; R = Me, Ib; R = n-Bu, Ic) have been synthesised from the corresponding diorganotin(IV) dichlorides and the ligand, N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide in methanol at room temperature in the presence of trimethylamine. All the complexes have been characterized by elemental analysis, IR and ¹H, ¹³C, ¹⁵N, ¹¹⁹Sn NMR spectra, and their structures have been confirmed by single crystal X-ray diffraction analysis of one representative compound Ia. Complex Ia crystallises in the orthorhombic system, space group Pna2₁ with a = 12.424(5), b = 9.911(5), c = 18.872(5) Å; Z = 4. The ligand N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide (H₂L) coordinates to the metal centre in the enolate form via the phenolic O, imino N and enolic O atoms. In Ia, the central tin atom adopts a distorted trigonal bipyramidal coordination geometry with the oxygen atoms in axial positions, while the imino nitrogen atom of the Schiff base and the two phenyl groups occupy the equatorial sites. The δ(¹¹⁹Sn) values for the complexes Ia, Ib and Ic are −327.3, −151.7 and −187.2 ppm, respectively, thus indicating penta-coordinated Sn centres in solution.     

Structural and spectral studies of 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one and its diorganotin(IV) complexes

Two diorganotin(IV) complexes of the general formula R₂Sn[Ph(O)CCH-C(Me)N-C₆H₄(O)] (R = Ph, 1a; R = Me, 1b) have been synthesized from the corresponding diorganotin(IV) dichlorides and the ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (1) in methanol at room temperature in presence of triethylamine. Both compounds have been characterized by elemental analyses, IR and ¹H, ¹³C, ¹⁵N, ¹¹⁹Sn NMR spectra. The structures of the free ligand and the complexes have been confirmed by single crystal X-ray diffraction. There are three independent molecules in the crystal structure of the ligand 1 and in all three the O-bound proton is transferred to the imine nitrogen and makes an intramolecular N-H?O hydrogen bond with the carbonyl oxygen. In turn this makes an intermolecular hydrogen bond with the phenolic H atom. The crystal structure of 1 is trigonal and a new polymorph; triclinic and monoclinic forms have already been published. In 1a, the central tin atom adopts distorted trigonal-bipyramidal coordination geometry whereas in dimeric 1b it is distorted octahedral when including the intermolecular Sn-O(phenolic) bond [2.7998(20) Å]. The δ (¹¹⁹Sn) values for the complexes 1a and 1b are −306.6 and −127.9 ppm, respectively, thus indicating penta-coordinated Sn centres in solution.     

1-Aza-5-stanna-5,5-dimethylbicyclo[3.3.01,5] octan und 1-aza-5-stanna-5-methyltricyclo[3.3.3.01,5] undecan,pentakoordinierte tetraorganozinnverbindungen

The synthesis of Me₂Sn(CH₂CH₂CH₂)₂NMe and MeSn(CH₂CH₂CH₂)₃N is reported. The transannular SnN interaction is confirmed by ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy.     

Diorganotin(IV) complexes of dideprotonated pyridoxine (PN, vitamin B6). The crystal structures of [SnEt2(PN-2H)] · CH3OH, [SnEt2(PN-2H)(DMSO)] and [SnBu2(PN-2H)]

The reactions of dimethyl-, diethyl- and dibutyltin(IV) oxides with pyridoxine (PN) in toluene/ethanol led to the formation of compounds [SnR₂(PN-2H)] which were characterized by EI and FAB mass spectrometry and by IR, Raman, Mössbauer and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. The structures of [SnEt₂(PN-2H)] · CH₃OH, [SnBu₂(PN-2H)] and [SnEt₂(PN-2H)(DMSO)] were determined by X-ray diffractometry. The first two contain dimeric [SnR₂(PN-2H)]₂ units in which two bridging-chelating pyridoxinate anions link the Sn atoms, while in [SnEt₂(PN-2H)(DMSO)] the DMSO coordinates to the tin atom via its O atom in a similar dimeric unit.     

Ethylene addition to OsO3(CH2) - A theoretical study

Quantum chemical calculations at the B3LYP/TZVP level of theory have been carried out for the initial steps of the addition reaction of ethylene to OsO₃(CH₂). The calculations predict that there are two reaction channels with low activation barriers. The kinetically and thermodynamically most favored reaction is the [3+2]_O, C addition which has a barrier of only 2.3 kcal mol⁻¹. The [3+2]_O, O addition has a slightly higher barrier of 6.5 kcal mol⁻¹. Four other reactions of OsO₃(CH₂) with C₂H₄ have significantly larger activation barriers. The addition of ethylene to one oxo group with concomitant migration of one hydrogen atom from ethylene to the methylene ligand yields thermodynamically stable products but the activation energies for the reactions are 16.7 and 20.9 kcal mol⁻¹. Even higher barriers are calculated for the [2+2] addition to the OsO bond (32.6 kcal mol⁻¹) and for the addition to the oxygen atom yielding an oxiran complex (41.2 kcal mol⁻¹). The activation barriers for the rearrangement to the bisoxoosmaoxirane isomer (36.3 kcal mol⁻¹) and for the addition reactions of the latter with C₂H₄ are also quite high. The most favorable reactions of the cyclic isomer are the slightly exothermic [2+2] addition across the OsO bond which has an activation barrier of 46.6 kcal mol⁻¹ and the [3+2]_O, O addition which is an endothermic process with an activation barrier of 44.3 kcal mol⁻¹.     

Synthesis,molecular structure and stereoisomerization of 2-phosphinyl and 2-phosphonylethyl diorganotin halides

Functionally substituted triorganotin halides V–IX of type R₂Sn(X)(CH₂)₂P(O)PhR′ (R = Me, t-Bu; Rt? = OEt, t-Bu; X = Cl, Br) have been synthesized by halogen cleavage of the corresponding tetraorganotin compounds R₂R²Sn(CH₂)₂P(O)PhR′ (R² = Me or Ph), I–IV. The solid state structure of Me₂Sn (Br) (CH₂)₂P(O)PhBu-t (IX), determined by X-ray diffraction, shows a distorted trigonal-bipyramidal structure at the tin atom, with intramolecular coordination of the PO group. Spectroscopic data are in agreement with such a structure in solution for compounds V–IX. Upon varying the temperature, concentration or solvent in solutions of compounds V–IX a stereoisomerization is observed. On the basis of NMR ¹H, ¹³C, ³¹P, ¹¹⁹Sn), IR and conductivity studies, it is suggested that this stereoisomerization involves a hexacoordinated transition state at the tin atom.     

New stable germylenes, stannylenes, and related compounds: 6. Heteroleptic germanium(II) and tin(II) compounds [(SiMe3)2N-E-OCH2CH2NMe2]n (E = Ge, n = 1; Sn, n = 2): synthesis and structure

New stable heteroleptic germanium(II) and tin(II) compounds [(SiMe₃)₂N-E¹⁴-OCH₂CH₂NMe₂]_n (E¹⁴ = Ge, n = 1 (1), Sn, n = 2 (2)) have been synthesized and their crystal structures have been determined by X-ray diffraction analysis. While compound 1 is monomer stabilized by intramolecular Ge ← N coordination, compound 2 is associated to dimer via intermolecular dative Sn ← O interactions.     

Diphenyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and multinuclear NMR, Sn Mössbauer, electrospray ionization MS, X-ray characterization and assessment of in vitro cytotoxicity

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}diphenyltin(IV) complexes have been synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analysis. The structures of a ligand L⁶H (i.e., 5-[(E)-2-(4-ethoxyphenyl)-1-diazenyl]quinolin-8-ol) and three diphenyltin(IV) complexes, viz., Ph₂Sn(L¹)₂ · (CH₃)₂CO (1), Ph₂Sn(L⁴)₂ (4) and Ph₂Sn(L⁵)₂ (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = phenyl - (L¹H); 4′-methylphenyl - (L⁴H) and 4′-bromophenyl - (L⁵H)) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom. These complexes retain their solid-state structure in non-coordinating solvent as evidenced by ¹¹⁹Sn NMR spectroscopic results. The in vitro cytotoxicity of 1 is reported and compared with Ph₂Sn(Ox)₂ (Ox = deprotonated quinolin-8-ol) against seven well characterized human tumor cell lines.     

New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine as models for metal-protein interactions: Synthesis and structural characterization. Crystal structure of Me2Sn(Tyr-Phe) · MeOH

New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine (H₂Tyr-Phe) with general formulae R₂Sn(Tyr-Phe) where R = Me,n-Bu, n-Oct and Ph, and R₃^′Sn(HTyr-Phe) where R^′ = Me and Ph have been synthesized. The bonding and coordination behaviour in these derivatives are discussed on the basis of FT-IR, multinuclear ¹H, ¹³C and ¹¹⁹Sn NMR and ¹¹⁹Sn Mössbauer spectroscopic studies. These investigations suggest that dipeptide in R₂Sn(Tyr-Phe) acts as dianionic tridentate coordinating through −C(O)O⁻, -NH₂ and (-CO)N⁻_peptide groups while in case of R^′₃Sn(HTyr-Phe) the ligand acts as monoanionic bidentate coordinating through -C(O)O⁻ and -NH₂, and the polyhedron around tin in R₂Sn(Tyr-Phe) and R^′₃Sn(HTyr-Phe) is a distorted trigonal-bipyramidal. It is further confirmed by the single crystal X-ray structure of Me₂Sn(Tyr-Phe) · MeOH which shows two methyl groups and peptide nitrogen (N⁻_peptide) in the equatorial positions, while the two axial positions are occupied by the carboxylic oxygen (O⁻_carboxyl) and the amino nitrogen (N_amino) atom from the same ligand molecule. One methanol molecule is also present in the asymmetric unit.     

Synthesis and crystal structures of new complexes of di- and tribenzyltin 2-amino-1-cyclopentene-1-carbodithioates

Treatment of dibenzyltin dichloride with 1 equiv. of 2-amino-1-cyclopentene-1-carbodithioic acid (ACDA) gave Bz₂SnCl(ACDA) (1) that contains five coordinate tin. Reaction of 2 equiv. of ammonium 2-amino-1-cyclopentene-1-carbodithioic acid (AACD) with Bz₂SnCl₂ and then recrystallization from THF produced Bz₂Sn(ACDA)₂ · THF 2 in which the coordination geometry around the Sn is highly distorted from octahedral. Bz₃Sn(ACDA) (3) was obtained from reaction of Bz₃SnCl with 1 equiv. of AACD. The crystal structure of 3 indicates a Sn-S′ interaction [3.0823(5) Å] that distorts the tin coordination geometry from that of an ideal tetrahedron. In 1-3 the tin atom is also coordinated to one carbon atom of each benzyl group. The products were characterized by IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and elemental analysis.     

Triorganotin(IV) derivatives of umbelliferone (7-hydroxycoumarin) and their adducts with 1,10-phenanthroline: synthesis, structural and biological studies

New triorganotin(IV) derivatives of the general formula R₃Sn(Umb) (where, R = Me, n-Bu and Ph; Umb = umbelliferone anion) have been synthesized using sodium salt method. Further, the adducts of the general formula R₃Sn(Umb) · phen (where R = Me and Ph; phen = 1,10-phenanthroline) have also been synthesized by the interaction of the triorganotin(IV) derivatives of umbelliferone with 1,10-phenanthroline. The bonding and coordination behavior of these derivatives are discussed on the basis of IR, NMR (¹H, ¹³C and ¹¹⁹Sn), and ¹¹⁹Sn Mössbauer spectroscopic studies. These investigations indicate that umbelliferone acts as a monoanionic bidentate ligand in R₃Sn(Umb) coordinating through O(7) and O(1) in the solid-state. These polymeric R₃Sn(Umb) derivatives (where R = Me and n-Bu) have been proposed to have a trans-trigonal bipyramidal geometry with the three R groups in equatorial positions, while the axial positions are occupied by a phenolic oxygen and the O(1) atom from the adjacent molecule. A pseudotetrahedral geometry has been suggested for Ph₃Sn(Umb). A distorted octahedral geometry around tin has been proposed for R₃Sn(Umb) · phen, in which umbelliferone anion acts as a monodentate ligand coordinating through phenolic oxygen O(7). The newly synthesized derivatives have been assayed for their anti-inflammatory, cardiovascular and anti-microbial activities. The average LD₅₀ values >1000 mg kg⁻¹ of these derivatives indicate their safety margin. Among all the compounds tested, Ph₃Sn(Umb) · phen has been found to show potent anti-inflammatory activity with low mammalian toxicity and mild hypotensive activity.     

Preparation and structures of [2‐(dimethylamino)phenyl]diorganotin(IV) acetates substituted with organophosphorus groups in the α‐position of the acetate ligand

Organotin(IV) carboxylates R₂L^NCSnOC(O)CH₂P(E)Ph₂, where L^NC is an N‐chelating 2‐(dimethylamino)phenyl group, and R/E = Ph/void (1a), Ph/O (1b), Ph/S (1c), Me/void (2a), Me/O (2b) and Me/S (2c), were synthesized, characterized by ¹H, ¹³C, ³¹P and ¹¹⁹Sn NMR, IR and MS spectra, and the solid‐state structures of 1b, 1c, 2b and 2c were determined by single‐crystal X‐ray diffraction. Spectral and structural data showed that the compounds are monomeric in CDCl₃ solution and the solid state, with the organophosphorus groups in the α‐position of the monodentate carboxylate ligands not interacting with the tin atom. Copyright © 2005 John Wiley & Sons, Ltd.     

Organotin(IV) triazolates: Synthesis and their spectral characterization

Some organotin(IV) triazolates of general formula R_nSn(L)_4 − n (where R = Me, n-Bu and Ph for n = 2; R = Me, n-Pr and n-Bu for n = 3 and HL = 3-amino-5-mercapto-1,2,4-triazole) have been synthesized by the reaction of R₂SnCl₂/R₃SnCl with NaL in 1:2/1:1 molar ratio. Whereas, Oct₂SnL₂ has been synthesized azeotropically by the reaction of Oct₂SnO and HL in 1:2 molar ratio. As good single crystals were not obtained, a large number of experimental techniques, viz. UV/Vis, IR, far-IR, multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR and ¹¹⁹Sn Mössbauer spectroscopic studies, were used to accomplish a definitive characterization and determination of their most probable structures. In these compounds triazole acts as a monoanionic bidentate ligand, coordinating through S_exo and N(4). The IR and ¹¹⁹Sn Mössbauer spectroscopic studies allow us to deduce a highly distorted cis-trigonal-bipyramidal structure for R₃SnL and a distorted skew trapezoidal-bipyramidal structure for R₂SnL₂, in the solid state. However, ¹H, ¹³C and ¹¹⁹Sn NMR spectral studies revealed that weak bonding between tin and N(4) is further weakened in the solution leading to pseudo-tetrahedral/tetrahedral structure.     

Structural features of some organotin(IV) complexes of semi- and thio-semicarbazones

Some five- and six-coordinated di and tri-n-butyl tin(IV) semi- and thio-semi carbazates have been synthesized. The characterization of these complexes, by IR, NMR (¹H, ¹³C, ¹¹⁹Sn), ¹¹⁹Sn), ¹¹⁹Sn Mössbauer and Mass spectroscopies along with X-ray diffraction, reveals that complexes of biionic ligands of the type Bu₂Sn L″ are five-coordinated having trigonal bipyramidal geometry. However, complexes of monoionic ligands of the type Bu₂SnL′₂ are six-coordinated in a distorted cis-octahedral geometry and Bu₃SnL′ are five-coordinated with a trigonal bipyramidal structure. X-ray structural studies on the compound Bu₂Sn(O.C₆H₄.CH:N.N.CS.NH₂), show that it crystallizes in a monoclinic lattice with a = 16.90 Å, b = 9.71 Å, c = 8.60 Å, and β = 103°45′.     

Hypervalence in germanium compounds containing the tetracylic moiety {S(C6H3S)2O}Ge via O···Ge transannular interactions: A structural study

Treatment of R_nGeCl_4−n with {S(C₆H₃SH)₂O} (1) afforded the stable phenoxathiin-4,6-dithiolate compounds [{S(C₆H₃S)₂O}GeR₂] [n = 2; R = Et (2), Ph (3)] and [{S(C₆H₃S)₂O}GeRCl] [n = 1; R = Et (4), Ph (5)]. Treatment of GeCl₄ with 1 in benzene afforded the dichloro compound [{S(C₆H₃S)₂O}GeCl₂] (8) at 7 °C. Bromo compounds [{S(C₆H₃S)₂O}GeRBr] [R = Et (6), Ph (7)] and [{S(C₆H₃S)₂O}GeBr₂] (9) were synthesized by halogen exchange from the appropriate chloro derivative using KBr/HBr. X-ray structure determinations of diorganyl dithiolate compounds 2 and 3 revealed that germanium atom is contained in a boat–chair-shaped eight-membered central ring and displays a tetrahedral geometry. In contrast, compounds 4–6 display a boat–boat-shaped central ring with a significant intramolecular transannular O···Ge interaction. The geometry of the pentacoordinate Ge atom in these last complexes may be described as distorted trigonal bipyramidal with a 62–65% distortion displacement.