Iridium nitrosyl complexes of 2-aminophenol derivatives

Summary The synthesis and characterisation of products obtained by the interaction between [Ir(NO)(MeCN)₂(PPh₃)₂]²⁺ and 2-aminophenol derivatives are reported. Tetracoordinate d⁸complexes of the type Ir(NO)(2-ap)(PPh₃) and pentacoordinate d complexes₆of the type [Ir(2-ap)(PPh₃)₃]⁺ where 2-ap=2-aminophenol, 2-amino-4-nitrophenol, 2-amino-5-methylphenol, 2-3-aminonaphthol and 2-amino-4-methylphenol are obtained. The Ir(NO)(PPh₃)₃ complex is always present as a byproduct. Physical properties, i.r. spectra and conductivity data of the complexes are tabulated. Reaction schemes for the formation of the three complexes are proposed and discussed.     

Synthesis, 119Sn Mössbauer spectroscopic studies and X-ray crystal structure determination of new seven-coordinate diorganotin(IV) complexes with S,N,N,N,S-pentadentate Schiff bases derived from 2,6-diacetylpyridine of S-methyl- and S-benzyldithiocarbazates

The reactions of the ligands 2,6-diacetylpyridine bis(S-methyldithiocarbazate)] (H₂dapmdtc) and 2,6-diacetylpyridine bis(S-benzyldithiocarbazate)] (H₂dapbdtc) with R_4-m SnCl _m (R = Me, ⁿ Bu, Ph; and m = 2) led to the formation of six seven-coordinate diorganotin(IV) complexes, which were studied by microanalysis, i.r., n.m.r (¹H, ¹¹⁹Sn) and Mössbauer spectroscopies. The X-ray structures determination of complexes [Me₂Sn(dapmdtc)], [Me₂Sn(dapbdtc)] and [Ph₂Sn(dapbdtc)] revealed the presence of neutral seven-coordinated complexes. The structures consist of monomeric units in which the Sn(IV) atom exhibits distorted pentagonal bipyramidal (PBP) geometry, with the S,N,N,N,S-donor systems of the ligands lying in the equatorial plane and organic groups in the apical positions. A correlation between Mössbauer and X-ray data based on the point-charge model is discussed.     

Triorganotin(IV) derivatives of 7-amino-2-(methylthio)[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylic acid. Synthesis, spectroscopic characterization, in vitro antimicrobial activity and X-ray crystallography

Triorganotin(IV) complexes of the 7-amino-2-(methylthio)[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylic acid (HL), Me₃SnL(H₂O), (1), [n-Bu₃SnL]₂(H₂O), (2), Ph₃SnL(MeOH), (3), were synthesized by reacting the amino acid with organotin(IV) hydroxides or oxides in refluxing methanol. The complexes have been characterized by elemental analysis, ¹H, ¹³C and ¹¹⁹Sn NMR, IR, Raman and ¹¹⁹Sn Mössbauer spectroscopic techniques. Single crystal X-ray diffraction data were obtained for compounds (2) and (3). Ph₃SnL(MeOH) presents a trigonal bipyramidal structure with the organic groups on the equatorial plane and the axial positions occupied by a ligand molecule, coordinated to tin through the carboxylate, and a solvent molecule, MeOH. A similar structure is proposed for Me₃SnL(H₂O) on the basis of analytical and spectroscopic data. The tributyltin(IV) derivative, [n-Bu₃SnL]₂(H₂O), is characterized by two different tin sites with similar tbp geometry featured by butyl groups on the equatorial plane. Sn(1) and Sn(2) atoms are axially bridged by a ligand molecule binding through the N(4) and the carboxylate group; the two coordination spheres are saturated by another ligand molecule, binding the metal through the carboxylate group, and a water molecule, respectively. Antimicrobial tests on compounds 1 and 2 showed in vitro activity against Gram-positive bacteria.     

New organotin(IV) complexes with l-Arginine, Nα-t-Boc-l-Arginine and l-Alanyl-l-Arginine: Synthesis, structural investigations and cytotoxic activity

Novel diorganotin(IV) derivatives of l-Arginine (HArg), N_α-(tert-Butoxycarbonyl)-l-Arginine (Boc-Arg-OH) and l-Ala-l-Arg (H₂Ala-Arg), H₂NC(NH)NH(CH₂)₃CH(NHR′)CO₂H, where R′ = H in HArg, R′ = C(O)OC(CH₃)₃ in Boc-Arg-OH, R′ = H₂NCH(CH₃)CO in H₂Ala-Arg and triorganotin(IV) derivatives of Boc-Arg-OH have been synthesized and structurally characterized. The complexes were investigated by FT-IR and ¹¹⁹Sn Mössbauer in the solid state and by ¹H, ¹³C, ¹¹⁹Sn and ¹H-¹H COSY NMR spectroscopy, in solution. The spectroscopic characterization leading to the proposed molecular structures was accomplished on the basis of these experiments. l-Arginine appears to behave as a chelating ligand through carboxylate and -NH₂ groups in Me₂Sn(Arg)₂, while in N_α-t-Boc-l-Arginine complex, the N_α-protected amino group being exempted from coordination, only the carboxylate groups are effectors of bonding to the organometallic moieties. FT-IR spectra give a clear indication that guanidino groups in all the complexes are not involved in coordination, since ν(CN-H) frequency of the terminal guanidino group is fairly constant and unshifted relative to the free ligand. The biological activity of organotin(IV)-complexes was also investigated by use of human HT29 colorectal carcinoma cells. The cytotoxic activity of the compounds was determined by the MTT quantitative colorimetric assay, capable of detecting viable cells in comparison with that exerted by cisplatin. A marked cytotoxic activity for nearly all complexes, is evident being higher than that exerted by cisplatin, while no significant improvement of activity was observed for Me₂Sn(Arg)₂ and Me₂Sn(Ala-Arg), which was confirmed by IC₅₀ values. Then, we assessed whether the cytotoxicity induced by organotin(IV) complexes was associated with the induction of apoptosis. Light microscopy analysis, performed to study the morphological changes induced in HT29 cells, confirmed the results obtained with MTT test. No significant morphological alterations were observed in HT29 cells after treatment with Me₂Sn(Ala-Arg) and Me₂Sn(l-Arg)₂. Cells treated with ⁿBu₂Sn(Boc-Arg)₂, ⁿBu₂Sn(Ala-Arg), ⁿBu₃Sn(Boc-Arg) and Me₃Sn(Boc-Arg), appeared rounded, isolated and detached from culture substrate, indicating the commitment to apoptotic cell death.     

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.     

Tin(IV), Monomethyltin(IV), and Dimethyltin(IV) Complexes with thiol sulfur and heterocyclic nitrogen donors: Molecular dynamics and structure by 119Sn mössbauer spectroscopy

The molecular dynamics of the complexes Sn(SPyN)₄ ( 1 ), SnCl₂(SPyN)₂ ( 2 ), MeSn(SPy)₃ ( 3 ), MeSnCl(SPyN)₂ ( 4 ), Me₂Sn(TCy)₂ ( 5 ), Me₂SnCl(TOx) ( 6 ), and Me₂Sn(TUr) ( 7 ) [HSPy = 2-mercaptopyridine; HSPyN = 2-mercaptopyrimidine; HTCy = 2-thiocytosine; HTOx = 8-thioquinoline; H₂TUr = 2-thiouracil] has been investigated by variable temperature ¹¹⁹Sn Mössbauer spectroscopy. The area under the resonant peaks has been determined as function of temperature, from which Debye temperatures and cut-off frequencies, as well as recoil-free fractions (Lamb Mössbauer factor) and mean square displacements of ¹¹⁹Sn, have been calculated. By fingerprint procedures on the basis of literature data, monomeric structures are attributed to complexes ( 1 )–( 4 ) and ( 6 ), while ( 5 ) and ( 7 ) lie in the borderline monomersmonodimensional polymers. The results are discussed on the basis of known crystal and molecular structures. The nature of the environment of tin atoms has been simulated by point-charge model calculations of nuclear quadrupole splitting parameters; molecular structures are proposed for complexes ( 5 )–( 7 ), where no X-ray diffractometric data are available.     

Synthesis and characterization of the first diorganotin(IV) complexes containing mixed arylazobenzoic acids and having skew trapezoidal bipyramidal geometry

Three diorganotin(IV) complexes of the type, [R₂Sn(L^aH)(L^bH)] (R = ⁿBu or Me and, L^aH and L^bH are two different 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoate residues; a: aryl = 4′-Cl-(held constant) and b: aryl = 4′-Me or 4′-Br) have been prepared either by reacting ⁿBu₂SnO, L^aHH′ and L^bHH′ (1:1:1) in anhydrous toluene or by reacting Me₂SnCl₂, L^aHNa and L^bHNa (1:1:1) in anhydrous methanol. The products were characterized by microanalysis, IR, NMR (¹H, ¹³C, ¹¹⁹Sn) and ^119mSn Mössbauer spectroscopy. A full characterization of the structures of the complexes [ⁿBu₂Sn(L^aH)(L^bH)] (1 and 2) and [Me₂Sn(L^aH)(L^bH)] (3) in the solid state were accomplished by single crystal X-ray crystallography. These complexes were found to adopt the usual dicarboxylato structural type with a skew-trapezoidal bipyramidal arrangement around the tin atom.     

Chiral self-assembly of methyltin(IV)-naproxenates: Combining dative Sn-O bonds, secondary Sn?O interactions and C-H?O hydrogen bonding to make an inter-helical meander-shaped network and a cross-linked Z-shaped ribbon

Three new chiral organotin(IV) carboxylates, Me₂Sn(nap)₂ (1), {[Me₂Sn(nap)]₂O}₂ (2) and Me₃Sn(nap) (3) (nap = (S)-(+)-6-methoxy-α-methyl-2-naphthaleneaceto anion) have been synthesized. All of them have been characterized by elemental analysis, multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR and IR spectroscopy. The crystal structures of 1 and 2 have been determined by X-ray diffraction analysis. The bicapped tetrahedral molecules of 1 are linked by C-H?O hydrogen bonds into homochiral helices, which are also interconnected by C-H?O interactions to form an inter-helical meander-shaped network. The molecule of 2 is a parallel double helix incorporating four chiral tin centers in a Sn₄O₁₀C₄ ladder type molecular skeleton. The C-H?O interactions translate the molecular chirality of 2 throughout the crystal via formation of infinite ribbons. These ribbons in their turn are further cross-linked by C-H?O hydrogen bonds. The structural characterization of the complexes 1-3 in solution has been performed by routine multinuclear ¹H, ¹³C and ¹¹⁹Sn NMR as well as specialized multidimensional (¹H-¹¹⁹Sn-gHMQC and ¹H-DOSY) experiments. The relevant ²J_{¹H-¹¹⁹Sn} and ¹J_{¹³C-¹¹⁹Sn} coupling constants have been extracted and related to molecular geometries on the basis of the literature data. The measurement of the translational diffusion constants using diffusion ordered spectroscopy allowed the estimation of the spherical hydrodynamic radii of the newly prepared structures.     

On the occurrence of 119Sn-CIDNP during some reactions of trimethylstannyl radicals

The ¹¹⁹Sn nuclei of hexamethylditin, formed during the photochemical reaction of trimethyltin hydride with d₁-t-butyl peroxide or dibenzyl ketone, or during the thermal decomposition of azodusobutyronitrile with trimethyltin hydride, exhibit CIDNP. The nuclear polarisation is built up in radical pairs $\text{Me}{}_3\text{Sn··SnMe}{}_3$¹. The full CKO theory has to be used for explaining the net effect in the main ¹¹⁹Sn signals of the hexamethylditin. The high field approximation is not valid because of the high value of the ¹¹⁹Sn hyperfine splitting in trimethylstannyl radicals. The multiplet effect in the ¹¹⁷Sn satellites is interpreted in terms of the high field treatment. A negative sign is found for a_117Sn(Me₃Sn) and a_119Sn(Me₃Sn). ¹¹⁹Sn-CIDNP also appears in benzyltrimethyltin during photolysis of dibenzylketone with trumethyltin hydride. It is concluded from ¹H-CIDNP investigations that nuclear polarisations built up in radical pairs containing both stannyl radicals and others are not observed in hexamethylditin. A positive sign is found for

.     

The effect of the solvent upon the rates and mechanisms of organometallic reactions : V. PMR spectra and structure of molecular complexes of methyltin halides in solutions

The complexation of methyltin halides in electron-donating solvents such as acetone, dioxane, dimethoxyethane, pyridine, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoric triamide, and tetramethylethylenediamine has been studied by means of PMR spectroscopy. Equilibrium constants have been evaluated for Me₃SnHal·D (D = donor) complexes. The concentration and temperature dependences of J(¹¹⁹SnC¹H) in methyltin halides suggest some conclusions on the electron and spatial structures of complexes in solutions.     

Fourier transform NMR investigations of organotin compounds : VIII. Propenyl- and isopropenyl-tin compounds; detection and identification of isomers using 119Sn and 13c NMR

Starting from the equilibrium mixture of cis- and trans-1-bromo-1-propene, isomeric mixtures of compounds Me_n Sn(CH=GHMe)_4-n (n = 0–3) have been prepared and studied. While proton NMR only allows distinction between the methyltin signals of the various isomers (except where n = 3), the ¹³C spectra show separate signals for almost all isomeric carbons even when n = 0. In the ¹¹⁹Sn spectra the signals due to the various isomers are separated by ca. 20 ppm for a given value of n; the peak areas can be used to estimate the proportions of cis- and trans-propenyl residues present in the mixtures. Addition of 2-bromo-propene to the starting 1-bromo-1-propenes leads to the formation of further isomers, which can in all cases be observed and identified in the ¹¹⁹Sn spectra; ¹¹⁹Sn shifts can be calculated using the shifts for the Me₃SnC₃H₅ isomers as increments.     

Neutral penta-coordinated diorganotin(IV) complexes derived from ortho-aminophenol Schiff bases: Synthesis, characterization and molecular structures

The one pot reactions carried among ortho-aminophenol, R₂SnO (R = Me or Ph) and acetyl acetone, 2-hydroxyacetophenone and 2-hydroxy-3-methylacetophenone led to six new diorganotin(IV) compounds Me₂SnL1 (1), Ph₂SnL1 (2), Me₂SnL2 (3) Ph₂SnL2 (4), Me₂SnL3 (5) and Ph₂SnL3 (6) (H2L1 = 2-(3-hydroxy-1-methyl-but-2-enylideneamino)-phenol, H2L2 and H2L3 = 2-[1-(2-hydroxyaryl)alkylideneamino]-phenol) in good yields. Combination of IR, ¹H, ¹³C and ¹¹⁹Sn NMR and X-ray diffraction techniques along with elemental analyses evidenced the formation of penta-coordinated monomeric species. The crystal structures of ligand H2L1 and complexes 1, 3 and 4 were determined by single crystal X-ray diffraction study. In the solid state, the ligand H2L1 exists as keto-enamine tautomeric form. There are N-H…O intra-molecular hydrogen bonds between amine and carbonyl groups. Diorganotin(IV) complexes 1, 3 and 4 are monomers with TBP (trigonal bipyramidal) geometry surrounding the tin atom. The O, N, O- tridentate ligand places its two oxygen donating atoms in the axial positions, and the nitrogen atom occupies one equatorial position. The two R groups attached to tin occupy the other two equatorial positions. The solution structures were predicted by ¹¹⁹Sn NMR spectroscopy.     

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′.     

Synthesis, 119Sn, 13C and 195Pt NMR studies of five-coordinate rhodium(I), iridium(I) and platinum(II) complexes containing three trichlorostannate ligands

The synthesis and ¹¹⁹Sn NMR characteristics of new five-coordinate tris(trichlorostannato) complexes of Rh^I, Ir^I and Pt^II are reported. The Rh^I and Ir^I complexes are complex dianions of the form (PPN)₂[M(SnCl₃)₃L₂] where L can be CO, CN (cyclohexyl) or L₂, a diolefin such as 1,5-COD or NBD (norbornadiene). The anionic platinum complexes (PPN)[Pt(SnCl₃)₃L₂] contain similar L ligands. A number of neutral monotrichlorostannato complexes of type [M(SnCl₃)L₄] including [Ir(SnCl₃)(NBD)(1,5-COD)] have been prepared and characterized. Their δ(¹¹⁹Sn), δ(¹³C), δ(¹⁹⁵Pt) as well as ¹J(¹⁰³Rh, ¹¹⁹Sn), ¹J(¹⁹⁵Pt, ¹¹⁹Sn), ²J(¹¹⁹Sn, ¹¹⁷Sn) and ²J(¹¹⁹Sn, ¹³C) data are given. A trans influence series, based on ¹J(¹⁹⁵Pt, ¹¹⁹Sn), reveals the following sequence: H^? > PR₃ > AsR₃ > SnCl₃^? > olefin > Cl^?.     

Metallorganische diazoalkane : XVI. Synthese von silyldiazoalkanen Me3Si(LnM)CN2

Silyldiazoalkanes Me₃Si(L_nM)CN₂ (L_nM = Me₃Si, Me₃Ge, Me₃Sn, Me₃Pb; Me₃As, Me₃Sb, Me₃Bi) have been synthesized by three different routes: (a) reactions of the Me₃SiCHN₂ with metal amides L_nMNR¹R² of Group IVB and VB elements, using Me₃SnCl as catalyst; (b) reactions of the in situ prepared organolithium compound Me₃SiC(Li)N₂ with organometallic chlorides Me₃MCl (M = Si, Ge); (c) tincarbon bond cleavage reaction of (Me₃Sn)₂CN₂ with Me₃SiN₃, affording Me₃SnN₃, traces of bis(trimethylsilyl)diazomethane (Me₃Si)CN₂, trimethylsilyl(trimethylstannyl)diazomethane Me₃Si(Me₃Sn)CN₂ and bis(trimethylsilyl)aminoisocyanide (Me₃Si)₂NNC as the major reaction products. IR and NMR data (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ²⁰⁷Pb) of the new heterometal-diazoalkanes are reported and discussed in comparison to relevant compounds of the organometallic diazoalkane series.     

Infrared and mössbauer investigations on dimethyltin(IV) complexes with potentially tridentate dianionic ligands

Dimethyltin(IV) complexes with formulae Me₂Sn(IMDA)·H₂O, Me₂Sn(ODA)· H₂O and [Me₂Sn(OH)]₂(TDA) [IMDA²⁻ = iminodiacetate²⁻ (NOO); ODA²⁻ = oxydiacetate²⁻ (OOO); and TDA²⁻ = thiodiacetate²⁻ (SOO donor atoms)] have been obtained and their solid state coordination investigated. Infrared and Mössbauer spectroscopic evidence would suggest tridentate behaviour of the ligands in polymeric trans-dimethyl structures for Me₂Sn(IMDA)·H₂O and Me₂Sn(ODA)·H₂O with bridging carboxylate groups; polymeric tetrahedral environments around the two tin(IV) atoms could be inferred with TDA acting as bidentate dianionic ligand through ester type carboxylate groups in [Me₂Sn(OH)]₂(TDA), without involvement of the sulfur atom in coordination.     

Speciation and NMR Spectrometric Studies of Interaction of Di- and Tri-organotin(IV) Moieties with 5′-Guanosine Monophosphate and Guanosine in Aqueous Solution

Potentiometric studies of the interaction of (Me₂Sn)²⁺ and (Me₃Sn)⁺ with 5′-guanosine monophosphate [(5′-HGMP)^2?, abbreviated as (HL-1)^2?] and guanosine [(HGUO), abbreviated as (HL-2)] in aqueous solution (I = 0.1 mol·dm^?3 KNO₃, 298.15 ± 0.1 K) were performed, and the speciation of various complex species was evaluated as a function of pH. The species that exist at physiological pH ~7.0 are Me₂Sn(HL-1)/[Me₂Sn(HL-2)]²⁺ (87.0/88.8 %), [Me₂Sn(HL-1)(OH)]^?/[Me₂Sn(HL-2)(OH)]⁺ (3.0/0 %) and [Me₂Sn(HL-1H_?1)]/[Me₂Sn(HL-2H_?1)]²⁺ (9.4/6.6 %) for 1:1 dimethyltin(IV):5′-guanosine monophosphate/dimethyltin(IV): guanosine systems, whereas for the corresponding 1:2 systems, the species are Me₂Sn(HL-1)/[Me₂Sn(HL-2)]²⁺ (44.0/92.0 %), [Me₂Sn(HL-1H_?1)]/[Me₂Sn(HL-2H_?1)]²⁺ (5.0/6.0 %), Me₂Sn(OH)₂ (49.0/0 %), [Me₂Sn(HL-1)(OH)]^?/[Me₂Sn(HL-2)(OH)]⁺ (1.5/2.0 %), and [Me₂Sn(OH)]⁺ (1.0/0 %). For 1:1 trimethyltin(IV):5′-guanosine monophosphate/trimethyltin(IV):guanosine systems, only [Me₃Sn(HL-1)]^?/[Me₃Sn(HL-2)]⁺ (99.9 %) are found at pH = 7.0, whereas for 1:2 systems, [Me₃Sn(HL-1)]^?/[Me₃Sn(HL-2)]⁺ (49.8/100 %), Me₃Sn(OH) (15.0/0 %) and [Me₃Sn(HL-1)(OH)]^2?/Me₃Sn(HL-2)(OH) (0.2/0 %) are the species found. No polymeric species were detected. Beyond pH = 8.0, significant amounts of [Me₂Sn(OH)]⁺, Me₂Sn(OH)₂, [Me₂Sn(OH)₃]^? and Me₃Sn(OH) are formed. Multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR studies at different pHs indicated a distorted octahedral geometry for the species Me₂Sn(HL-1)/[Me₂Sn(HL-2)]²⁺ in dimethyltin(IV)-(HL-1)^2?/(HL-2) systems and a distorted trigonal bipyramidal/distorted tetrahedral geometry for the species [Me₃Sn(HL-1)]^?/[Me₃Sn(HL-2)]⁺ in trimethyltin(IV)-(HL-1)^2?/(HL-2) systems.     

Synthesis, spectroscopic characterization and in vitro antimicrobial activity of diorganotin(IV) dichloride adducts with [1,2,4]triazolo-[1,5-a]pyrimidine and 5,7-dimethyl-[1,2,4]triazolo-[1,5-a]pyrimidine

The heterocyclic ligands [1,2,4]triazolo-[1,5-a]pyrimidine (tp) and 5,7-dimethyl-[1,2,4]triazolo-[1,5-a]pyrimidine (dmtp), react with diorganotin dichlorides giving the addition compounds Me₂SnCl₂(tp)₂, Et₂SnCl₂(tp)₂, Me₂SnCl₂(dmtp)₂, Et₂SnCl₂(dmtp)₂, Bu₂SnCl₂(dmtp), Ph₂SnCl₂(dmtp). The organotin:ligand stoichiometry goes from 1:2 to 1:1 by increasing the steric hindrance of the organic groups bound to tin. The compounds have been characterized by means of infrared, ¹¹⁹Sn Mössbauer and ¹H AND ¹³C NMR spectroscopy.The ligands presumably coordinate to tin classically through the nitrogen atom at the position 3. The 1:1 complexes adopt trigonal bipyramidal structures, with the organic groups on the equatorial plane and the ligand in the apical position. All-trans octahedral structures are inferred for the 1:2 complexes, except for Et₂SnCl₂(tp)₂, characterized by a skew-trapezoidal structure.¹¹⁹Sn Mössbauer measurements, at room temperature, in concomitance with DFT calculations, performed on isomeric structures of R₂SnCl₂(tp)₂ (R = Me, Et), allowed us to conclude that the all-trans octahedral coordination induces self-assembly in the solid state, possibly accomplished through π-π stacking interactions among the planar ligands coordinated to the organotin(IV) compound, while the skew-trapezoidal structure attributed to Et₂SnCl₂(tp)₂, induces the formation of monomeric adducts in the solid state.In vitro antimicrobial tests showed that [n-Bu₂SnCl₂(dmtp)] has interesting properties as anti Gram-positive and antibiofilm agent.     

1,10-Phenanthrolinium hydrogensquarate monohydrate—A non-centrosymmetric structure from two non-chiral agents

Four different dimethyltin(IV) complexes of Schiff bases derived from 2-amino-3-hydroxypyridine and different substituted salicylaldehydes have been synthesized. The compounds, with the general formula [Me₂Sn(2-OArCHNC₅H₃NO)], where Ar = –C₆H₃(5-CH₃) [Me₂SnL¹], –C₆H₃(5-NO₂) [Me₂SnL²], –C₆H₂(3,5-Cl₂) [Me₂SnL³], and –C₆H₂(3,5-I₂) [Me₂SnL⁴], were characterized by IR, NMR (¹H and ¹³C), mass spectroscopy and elemental analysis. Me₂SnL³ was also characterized by X-ray diffraction analysis and shows a fivefold C₂NO₂ coordination with distorted square pyramidal geometry. H₃C–Sn–CH₃ angles in the complexes were calculated using Lockhart's equations with the ¹J(^117/119Sn–¹³C) and ²J(^117/119Sn–¹H) values (from the ¹H-NMR and ¹³C-NMR spectra). The in vitro antibacterial and antifungal activities of dimethyltin(IV) complexes were also investigated.