Encapsulation of organotin compounds in metal acetate glasses

Triorganotin halides, oxides and sulphides can be dissolved in molten, mixed-metal acetates at ca 140–160°C without decomposition; quenching provides glasses into which are encapsulated the organotin species. Halide/acetate and oxide/acetate, but not sulphide/acetate, exchanges occur in the melt. Only partial exchange was found for hindered trineophyl tin chloride [(PhCMe₂CH₂)₃SnCl], in contrast to the complete exchanges observed for the butyl (Bu), phenyl (Ph) and cyclohexyl (Cy) analogues. Complete oxide/acetate exchange was found for (Bu₃Sn)₂O, partial exchange occurred for (Cy₃Sn)₂O, whilst no exchange resulted with bis(trineophyltin) oxide or (Ph₃Sn)₂O. Tin–tin bonds (e.g. as in Ph₃SnSnPh₃) and carbon–tin bonds (even the allyl–Sn bond in Bu₃SnCH₂CH?CH₂) are not affected. The acetate glasses dissolve in aqueous media with release of the organotin species and they have potential as slow-release systems which is currently being investigated.     

Synthesis,Structure–Activity Relationship of Some New Triorganotin(IV) Derivatives of Dipeptides as Anti-Inflammatory Agents

Abstract

New triorganotin(IV) derivatives of dipeptides with general formulae, R₃Sn(HL), where R = Me and Ph, and HL is the monoanion of histidinylalanine and histidinylleucine, have been synthesized and characterized on the basis of infrared (IR), multinuclear NMR (¹H, ¹³C, and ¹¹⁹Sn), and ¹¹⁹Sn Mössbauer spectroscopic studies. These derivatives exhibit distorted trigonal-bipyramidal geometry around tin in which dipeptide anion acts as bidentate ligand coordinating through carboxyl oxygen and amino nitrogen. Ph₃Sn(HHis-Ala),

Ph₃Sn(HHis-Leu), and previously reported Ph₂Sn(His-Ala), Me₂Sn(His-Ala), n-Oct₂Sn(His-Ala), Me₂Sn(His-Leu), n-Oct₂Sn(His-Leu), Ph₃Sn(HTyr-Phe), Ph₂Sn(Tyr-Phe), Bu₂Sn-(Tyr-Phe), and n-Oct₂Sn(Tyr-Phe) along with standard drugs, viz. phenyl butazone and indomethacin were screened for in vivo anti-inflammatory activity and acute toxicity (LD₅₀). Diorganotin(IV) derivatives are more active than triorganotin(IV) derivatives. Me₂Sn(His-Leu) shows the highest activity.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Stannylierungsexperimente mit NH-funktionellen Aminoiminophosphoranen. Synthese und Struktur der tricyclischen Stannaphosphazene [Me2Sn(tBu2PN)NH]2 und [nBu2Sn(Ph2PN)2NH]2

Stannylation Experiments with NH-functional Aminoiminophosphoranes. Synthesis and Structure of the Tricyclic Stannaphosphazenes [Me₂Sn(^tBu₂PN)NH]₂ and [ⁿBu₂Sn(Ph₂PN)₂NH]₂ Aminoiminophosphoranes ^tBu₂P(NH)NH₂ ( 1 ) and (H₂NPPh₂)N(Ph₂PNH) ( 2 ) react with diaminostannanes R₂Sn(NEt₂)₂ by cyclocondensation to give cyclostannaphosphazenes [Me₂Sn(^tBu₂PN)NH]₂ ( 3 ) and [R₂Sn(Ph₂PN)₂NH]₂ ( 4 a , b ) ( a : R = Me, b : R = ⁿBu). With 2 and Me₃SnNEt₂ the ring compound Me₂Sn(Ph₂PN)₂NSnMe₃ ( 5 ) besides Me₄Sn is formed by per-N-stannylation and Sn-methyl group transfer. The crystal structures of 3 and 4 b were determined by X-ray structure analysis. 3 forms a planar heterotricyclus containing three four-membered rings with two pentacoordinated tin atoms (space group P 1 (No. 2); Z = 1). 4 b consists of a tricyclic molecule with two puckered six-membered rings and one planar four membered tin-nitrogen ring with two pentacoordinated tin atoms (space group P 1 (No. 2); Z = 1).     

Organotin(IV) complexes of NSAID,ibuprofen, X-ray structure of Ph3Sn(IBF), binding and cleavage interaction with DNA and in vitro cytotoxic studies of several organotin complexes of drugs

This study encompasses the synthesis and characterization of organotin(IV) derivatives of non-steroidal anti-inflammatory drug ibuprofen (IBF), viz. [(Me₃Sn)(IBF)] ( 1 ), [(Bu₃Sn)(IBF)] ( 2 ), [Ph₃Sn(IBF)] ( 3 ), {[Me₂Sn(IBF)]₂O}₂ ( 4 ) and [Bu₂Sn(IBF)₂] ( 5 ). The crystal structure of complex 3 , [Ph₃Sn(IBF)], indicates a highly distorted tetrahedral (td) geometry with anisobidentate mode of coordination of the carboxylate group with tin atom, and a similar structure has been proposed for other two triorganotin(IV) derivatives. Moreover, the DFT (density functional theory) calculation and other studies have verified a dimer distannoxane type of structure for complex 4 , {[Me₂Sn(IBF)]₂O}₂. Complex 5 has been found to exhibit a highly distorted octahedral geometry around the tin atom. To investigate the DNA binding profile of the synthesized complexes, viscosity measurement, UV–vis and fluorescence titrations were performed, which revealed an intercalative type of binding with DNA for IBF and complex 5 and external binding in case of the complexes 1 and 2 ; complexes 3 and 4 could not be studied owing to their insufficient solubility in tris buffer. Plasmid DNA fragmentation studies of IBF and complexes 1 , 2 and 5 indicate that they cleaved the pBR322 plasmid potentially. Further, the drugs IBF {2-[4-(2-methylpropyl)phenyl]propanoic acid}, MESNA (sodium 2-mercaptoethane-sulfonate), warfarin [2H-1-benzopyran-2-one,4-hydroxy-3-(3-oxo-1-phenylbutyl)], sulindac (2-{5-fluoro-1-[(4-methanesulfinylphenyl) methylidene]-2-methyl-1H-inden-3-yl}acetic acid) and their corresponding organotin(IV) complexes 1–19 (complexes 6–19 were synthesized/reported previously) were screened in vitro for cytotoxicity against human cancer cell lines viz. DU145 (prostate cancer), HCT-15 (colon adenocarcinoma), Caco-2 (colorectal adenocarcinoma), MCF-7 (mammary cancer), LNCaP (androgen-sensitive prostate adenocarcinoma) and HeLa (cervical cancer), through MTT reduction assay and the cause of cell death was investigated through acridine orange/ethidium bromide staining of cells and DNA fragmentation assay. The probable structure–cytotoxicity relationship is also discussed. The major role of apoptosis along with small necrosis was also validated by flow cytometry assay using annexin V–fluorescein isothiocyanate and propidium iodide analysis.     

A study of trialkyltin β-aryl-β-triphenylgermyl propionates

Twenty new compounds of the form Ph₃GeCHArCH₂COOSnR₃ (R = n-Bu, cyclohexyl; Ar = substituted phenyl) have been synthesized. Their structures were characterized by IR and ¹¹⁹Sn and ¹H NMR spectroscopy. The compounds are five-coordinated carboxylate bridged polymers when R = n– Bu; when R = cyclohexyl (Cy) they are four-coordinate. ¹¹⁹Sn NMR measurements of chemical shift for the two series of compounds have shown that there is a good linear relationship for the chemical shift of ¹¹⁹Sn NMR between the tributyltin and tricyclohexyltin propionates, viz. δ¹¹⁹Sn(Bu₃Sn) = 1.0474 δ ¹¹⁹Sn(Cy₃Sn) + 95.8076, n = 5, r = 0.993. The structure of one compound was determined by X-ray diffraction. It exists as a monomeric four-coordinated species in a distorted tetrahedronal geometry.     

Chlorodiphenyltin(IV) and triphenyltin(IV) complexes of N-alkylated 2-amino-1-cyclopentene-1-carbodithioic acids: synthesis, spectroscopic characterization and X-ray studies

Four new complexes, [Ph₃Sn(isopropylACDA)] (1), [Ph₂SnCl(isopropylACDA)] (2), [Ph₃Sn(secbutylACDA)] (3), and [Ph₂SnCl(secbutylACDA)] (4), have been prepared from reaction between N-alkylated 2-amino-1-cyclopentene-1-carbodithioic acids (ACDA) with Ph₂SnCl₂ and Ph₃SnCl in 1:1 ratio. All complexes are characterized by FTIR, multinuclear NMR (¹H, ¹³C, and ¹¹⁹Sn) and mass spectrometry. In all complexes, the S–H proton has been removed and coordination takes place through the carbodithioate moiety. The ¹¹⁹Sn NMR data are consistent with five coordination of tin atom in solution. Complexes 2, 3, and 4 have also been confirmed by single X-ray crystallography. All three crystals are triclinic with space group P − 1. In complexes 2 and 4, the geometry around tin atom is distorted trigonal bipyramidal while in 3 the geometry is in between distorted tetrahedral and trigonal bipyramid. In all three structures, ligands are asymmetrically coordinated to tin atom. In addition, crystal structures are further stabilized by N–H···S hydrogen bonding.     

Synthesis,characterization, and antibacterial activity of triorganotin(IV) complexes of 2-methylphenol

The triorganotin(IV) complex Ph₃Sn(OPhMe-2) (1) has been synthesized by the reaction of Ph₃SnCl with NaOPhMe-2, while complexes of composition n-Bu₃Sn(OPhMe-2) (2) and Me₃Sn(OPhMe-2) (3) (where ?OPhMe-2 = ?OC₆H₄CH₃-2) have been obtained from the reaction of n-Bu₃SnCl and Me₃SnCl with 2-methylphenol in the presence of triethylamine in carbon tetrachloride. The complexes have been characterized by elemental analyses, molar conductance measurements, molecular weight determination, and IR, ¹H NMR, ¹³C NMR, and mass spectral studies. Thermal behavior of the complexes has been studied by TG and DTA techniques. The organotin(IV) complexes have also been screened for antibacterial activity and exhibit appreciable activity. The reactions of the complexes with 3- and 4-cyanopyridines yielded 1 : 1 adducts authenticated by physicochemical and IR and ¹H NMR spectral data.     

Synthesis,characterization and in vitro antitumour activity of diorganotin bisxanthates [R2Sn(S2COR′)2] (R=Me,Et, nBu,Ph; R′=Et,iPr, Hex) and crystal structure of bis(O-ethyldithiocarbonato)diphenyltin(IV)

A series of diorganotin bisxanthate compounds, [R₂Sn(S₂COR′)₂] (R=Me, Et, nBu, tBu, and Ph; R′?Et, iPr and cHex) have been prepared and characterized by spectroscopic methods (IR, NMR and FAB MS). The xanthate ligands chelate the R₂Sn moieties forming disparate Sn–S bonds leading to skew-trapezoidal biypramidal tin atom geometries. The crystal structure of a representative compound, [Ph₂Sn(S₂COEt)₂], confirms the spectroscopic results and shows the tin atom to be coordinated by two asymmetrically chelating xanthate ligands [Sn–S(1) 2.486(1), Sn–S(2) 3.052(1) Å and Sn–S(3) 2.484(1), Sn–S(4) 3.220(1) Å] with the two phenyl substituents lying over the weaker Sn–S interactions so that C–Sn–C is 126.5(1)°. Crystal data for [Ph₂Sn(S₂COEt)₂]: monoclinic space group P2₁/n: a=9.645(1), b=23.723(3), c=9.798(2) Å, ß=100.23(1)°, V=2206.2 ų, Z=4; 2708 data refined to final R 0.023. A selection of these compounds has been evaluated for activity against the L1210 mouse leukaemia cell line.     

Synthesis,spectroscopic characterization,and biological activity studies of organotin(IV) derivatives of (E)‐3‐(3‐fluorophenyl)‐2‐phenyl‐2‐propenoic acid. Crystal and molecular structure of Et2Sn[OCOC(C6H5)CH(3‐FC6H4)]

The complexes Me₂SnL₂ ( I ), Me₃SnL ( II ), Et₂SnL₂ ( III ), n‐Bu₂SnL₂ ( IV ), n‐Bu₃SnL ( V ), n‐Oct₂SnL₂ ( VI ), Bz₂SnL₂ ( VII ), and Ph₃SnL ( VIII ), where “L” is ( E )‐3‐(3‐fluorophenyl)‐2‐phenyl‐2‐propenoate, have been prepared and structurally characterized by means of elemental analysis, infrared, mass, and multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR spectral techniques. The spectroscopic results showed that the geometry around the Sn atom in triorganotin(IV) derivatives is four‐coordinated in noncoordinating solvent and behaves as five‐coordinated linear polymers with bridging carboxylate groups or five‐coordinated monomers, both acquiring trans‐R₃SnO₂ geometry for Sn in the solid state. While all the diorganotin(IV) derivatives may acquire trigonal bipyramidal structures in solution due to collapse of the Sn←OCO interaction and octahedral geometries in the solid state, which have been confirmed by the X‐ray crystallographic data of the compound III . The crystal structure of Et₂SnL₂ ( III ) has been determined by X‐ray crystallography and is found skew‐trapezoidal bipyramidal, which substantiates that the ligand acts as an anisobidentate chelating agent, thus rendering the Sn atom six coordinated. The crystal is monoclinic with space group C2₁/n. All the investigated compounds have also been screened for biocidal and cytotoxicity data. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:420–432, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20243     

Reactions of organotin chlorides R2SnCl2 (R = Et, But, or Ph) with lithium 4,6-di( tert -butyl)- N -(2,6-diisopropylphenyl)- o -amidophenolate. Synthesis and structures of tin( IV ) o -iminoquinone complexes

The exchange reactions of tin diorganohalides R₂SnCl₂ (R = Et, Bu^t, or Ph) with lithium amidophenolate APLi₂ (AP is the 4,6-di(tert-butyl)-N-(2,6-diisopropylphenyl)-o-iminobenzo-quinone dianion) in tetrahydrofuran produced the new five-coordinate (Et₂SnAP(THF) (3)) and four-coordinate (R₂SnAP (R = Bu^t, Ph)) tin(IV) complexes. The reaction of Ph₂SnCl₂ with APLi₂ in a nonpolar solvent (hexane or toluene) is accompanied by the additional redox process giving rise to the paramagnetic complex Ph₂Sn(ImSQ)Cl (6) (ImSQ is the 4,6-di(tert-butyl)-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone radical anion). The molecular structures of complexes 3 and 6 were established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 253–258, February, 2007.     

The in vitro antifungal activity of some dithiocarbamate organotin(IV) compounds on Candida albicans— a model for biological interaction of organotin complexes

The in vitro antifungal activity of the dithiocarbamate organotin complexes [Sn{S₂CN(CH₂)₄}₂Cl₂] ( 1 ), [Sn{S₂CN(CH₂)₄}₂Ph₂] ( 2 ), [Sn{S₂CN(CH₂)₄}Ph₃] ( 3 ), [Sn{S₂CN(CH₂)₄}₂n‐Bu₂] ( 4 ), [Sn{S₂CN(CH₂)₄}Cy₃] {Cy = cyclohexyl} ( 5 ), [Sn{S₂CN(C₂H₅)₂}₂Cl₂] ( 6 ), [Sn{S₂CN(C₂H₅)₂}₂Ph₂] ( 7 ), [Sn{S₂CN(C₂H₅)₂}Ph₃] ( 8 ), [Sn{S₂CN(C₂H₅)₂}₃Ph] ( 9 ) and [Sn{S₂CN(C₂H₅)₂}Cy₃] ( 10 ) has been screened against Candida albicans (ATCC 18804), Candida tropicalis (ATCC 750) and resistant Candida albicans collected from HIV‐positive Brazilian patients with oral candidiasis. All compounds exhibited antifungal activities and complexes 3 and 8 displayed the best results. We have investigated the effect of compounds 1–10 on the cellular activity of the yeast cultures. Changes in mitochondrial function have not been detected. However, all drugs reduced ergosterol biosynthesis. Preliminary studies on DNA integrity indicated that the compounds do not cause gross damage to yeast DNA. The data suggest that these compounds share some mechanisms of action on cell membranes similar to that of polyene but not with azole drugs, normally used in Candida infections. Copyright © 2008 John Wiley & Sons, Ltd.     

Organotin Complexes of Alizarin and Purpurin

Five novel organotin complexes with the anthraquinone dyes alizarin (1,2‐dihydroxyanthraquinone) and purpurin (1,2,4‐trihydroxyanthraquinone) were synthesized and characterized by elemental analyses, FTIR and NMR spectroscopy (¹H, ¹³C and ¹¹⁹Sn). The crystal and molecular structures of four complexes were determined by X‐ray diffraction on single crystals: [Bu₂Sn(aliz)(H₂O)]·C₂H₅OH ( A1 ·EtOH), [Bu₂Sn(aliz)(dmso)]₂ ( A3 ), [(Bu₂Sn)₃O(Hpurp)₂] ( P1 ) and [Bu₂Sn(Hpurp)(dmso)]₂ ( P2 ), where H₂aliz = alizarin and H₃purp = purpurin. The coordination mode of the ligands is identical to that found in their Al/Ca complexes, where they act as dianionic tridentate ligands forming five and six‐membered fused chelate rings. The coordination to the tin atoms occurs exclusively via the 1,2‐ phenolate oxygen and the adjacent quinoid oxygen atoms. The complexes A1 , A3 and P1 are dimers with hepta‐coordinated tin atoms in form of a slightly distorted pentagonal bipyramid. The trinuclear complex P2 contains two pentacoordinated and one heptacoordinated tin atoms.     

On the Hydrostannylation of Aryl Propargylic Alcohols and Their Derivatives: Remarkable Differences in Both Regio‐ and Stereoselectivity in Radical‐ and Nonradical‐Mediated Transformations

Herein, we describe a highly regio‐ and stereoselective radical‐mediated and molecular‐oxygen (O₂)‐dependent hydrostannylation of phenyl propargylic alcohols and their derivatives. There is a significant steric effect on the stereoselectivity of the tin‐radical addition. Further, the uncatalyzed regio‐ and stereoselective hydrostannylation of aryl propargylic alcohols with nBu₃SnH and Ph₃SnH is also described and occurs with near titration kinetics. Although the uncatalyzed addition with nBu₃SnH gave a remarkable γ‐regioselectivity irrespective of the electronic nature of the aryl moiety, addition with Ph₃SnH appears to be driven by the electronic nature of the aryl alkynes.     

Preparation and biocidal properties of mixed butyl/cyclohexyl trialkyltin carboxylates

Two series of trialkyltin carboxylates containing butyl and cyclohexyl groups on tin, Bu_nCy_3-nSnO₂CR (n = 1, 2; R = n-Pr, Ph, 4-CIC₆H₄, 4-NO₂C₆H₄) have been synthesized and their structures characterized by IR, and ¹¹⁹Sn and ¹³C NMR spectroscopies. The compounds are five-coordinate, carboxylate-bridged polymers when R = n-Pr, while the other aromatic carboxylates are four coordinate. The compounds were also tested for their fungicidal, insecticidal and acaricidal activities.     

Crystal Structures and Spectral Studies of [Ph3Sn(O2AsMe2)], [Bu2ClSn(O2AsMe2)] and [PhClSn(O2AsMe2)(μ‐OMe)]2

[Ph₃Sn(O₂AsMe₂)] ( 1 ) and [PhClSn(O₂AsMe₂)(μ‐OMe)]₂ ( 3 ) have been synthesized by treatment of Ph₃SnCl and Ph₂SnCl₂ with Na(O₂AsMe₂) in methanol, respectively. [Bu₂ClSn(O₂AsMe₂)] ( 2 ) has been prepared by the reaction of Bu₂SnCl₂ with HO₂AsMe₂ in methanol. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/n with a = 699.8(1), b = 1961.4(2), c = 1433.6(2) pm, β = 95.17(1)°, and Z = 4. 2 also crystallizes monoclinic in the space group P2₁/m, the cell parameters being a = 480.6(1), b = 1992.7(2), c = 808.8(1) pm, β = 103.726(5)°, and Z = 2. Both compounds form infinite chains with alternating (Me₂AsO₂)^? and (R₃Sn)⁺ or (R₂ClSn)⁺ units. The dimer 3 consists of 8‐membered (OSnOAs)₂ rings in which the tin atoms are bridged by methanolate bridges. It crystallizes triclinic in the space group with a = 822.8(2), b = 910.4(2), c = 929.2(2) pm, α = 77.04(3)°, β = 82.35(3)°, γ = 68.69(3)°, and Z = 1 for the dimer. The vibrational and mass spectra of 1 , 2 and 3 are given and discussed.     

Syntheses and crystal structures of four new organotin complexes with Schiff bases containing triazole

Four new organotin complexes, namely [(Bu₂Sn)₂O(EtO)(L1)]₂ (1), [(Bu₂Sn)₂O(EtO)(L2)]₂ (2), [(Bu₂Sn)₂O(EtO)(L3)]₂ (3) and [Ph₃Sn(L4)] · 0.5H₂O (4), were obtained by reactions of Bu₂SnO and Ph₃SnOH with 4-phenylideneamino-3-methyl-1,2,4-triazole-5-thione (HL1), 4-furfuralideneamino-3-methyl-1,2,4-triazole-5-thione (HL2), 4-(2-thienylideneamino)-3-ethyl-1,2,4 -triazole-5-thione (HL3) and 4-(3,5-di-t-butylsalicylideneamino)-3-ethyl-1,2,4-triazole-5-thione (HL4). Compounds 1-4 were characterized by elemental analysis, IR spectra and their structures were determined by single-crystal X-ray diffraction methods. Complexes 1-3 show similar structures containing a Sn₄O₄ ladder skeleton in which each of the exo tin atoms is bonded to the N atom of a corresponding thione-form deprotonated ligand. Complex 4 shows a mononuclear structure in which the tin atom of triphenyltin group is coordinated by the S atom of a thiol-form L4⁻ anion.     

Organotin Dyes: Synthesis and Structural Characterization of Dibutyltin and Dimethyltin Complexes with 2, 2′‐Dihydroxyazobenzene

The preparation and structures of 2, 2′‐dihydroxyazobenzenato‐dibutyl‐tin [Bu₂SnL] and 2, 2′‐dihydroxyazobenzenato‐dimethyl‐tin [Me₂SnL] are described. The complexes were characterized by IR, NMR (¹H, ¹³C, ¹¹⁹Sn) and UV/VIS spectra. The crystal structures were determined by X‐ray diffraction on single crystals. [Bu₂SnL]: monoclinic, space group P2₁/c, cell constants at 208 K: a = 860.73(5), b = 973, 51(18), c = 2340.0(3) pm, β = 93.615(11)°; R₁ = 0.0546. [Me₂SnL]: orthorhombic, space group Pbcn, cell constants at 208 K: a = 1914.6(4), b = 1041.3(3), c = 1323.27(14) pm; R₁ = 0.0529.     

Biocidal Organotin Compounds. Part 2. Synthesis,Characterization and Biocidal Properties of Triorganotin(IV) Hydantoic Acid Derivatives and the Crystal Structures of Triphenyltin and Tricyclohexyltin Hydantoates

The preparation and spectroscopic (¹H NMR, UV and IR) characterization of three R₃Sn(O₂CCH₂N(H)C(O)NH₂) [R=Ph, c-Hex (cyclohexyl) or n-Bu] compounds are reported. A different mode of coordination is indicated for the hydantoate ligand in the R=Ph compound compared with the R=c-Hex and R=n-Bu compounds, as confirmed by a crystallographic analysis. The structure of [Ph₃Sn(O₂CCH₂N(H)C(O)NH₂)] is polymeric owing to the presence of bridging hydantoate ligands such that each ligand coordinates one tin atom, via one of the carboxylate oxygen atoms, and a symmetry-related tin atom via the carbonyl group at the other end of the molecule. The structure features distorted trigonal-bipyramidal tin atom geometries with a trans -R₃SnO₂ motif. The structure of [c-Hex₃Sn(O₂CCH₂N(H)- C(O)NH₂)], by contrast, is monomeric, distorted tetrahedral, as the carboxylate group is monodentate and there are no additional tin–ligand interactions. The structures are each stabilized by a number of intermolecular hydrogen bonds. Fungitoxicity and phytotoxicity studies indicate that the R=n-Bu derivative is the more active compound.     

New Strategies to Phosphino–Phosphonium Cations and Zwitterions

By employing strategies based on frustrated Lewis pair chemistry, new routes to phosphino‐phosphonium cations and zwitterions have been developed. B(C₆F₅)₃ is shown to react with H₂ and P₂tBu₄ to effect heterolytic hydrogen activation yielding the phosphino‐phosphonium borate salt [(tBu₂P)PHtBu₂] [HB(C₆F₅)₃] ( 1 ). Alternatively, alkenylphosphino‐phosphonium borate zwitterions are accessible by reaction of B(C₆F₅)₃ and PhC?CH with P₂Ph₄, P₄Cy₄, or P₅Ph₅ affording the species [(Ph₂P)P(Ph)₂C(Ph)?C(H)B(C₆F₅)₃] ( 2 ), [(P₃Cy₃)P(Cy)C(Ph)?C(H)B(C₆F₅)₃] ( 3 ), and [(P₄Ph₄)P(Ph)C(Ph)?C(H)B(C₆F₅)₃] ( 4 ). A related phosphino‐phosphonium borate species—[(Ph₄P₄)P(Ph)C₆F₄B(F)(C₆F₅)₂] ( 5 ) is also isolated from the thermolysis of B(C₆F₅)₃ and P₅Ph₅.