DMSO Complexes Research Articles

Tailoring Ru(II) pyridine/triazole oxygenation catalysts and using photoreactivity to probe their electronic properties.

Tuning of ligand properties is at the heart of influencing chemical reactivity and generating tailor-made catalysts. Herein, three series of complexes [Ru(L)(Cl)(X)]PF6 (X=DMSO, PPh3 , or CD3 CN) with tripodal ligands (L1-L5) containing pyridine and triazole arms are presented. Triazole-for-pyridine substitution and the substituent at the triazole systematically influence the redox behavior and photoreactivity of the complexes. The mechanism of the light-driven ligand exchange of the DMSO complexes in CD3 CN could be elucidated, and two seven-coordinate intermediates were identified. Finally, tuning of the ligand framework was applied to the catalytic oxygenation of alkanes, for which the DMSO complexes were the best catalysts and the yield improved with increasing number of triazole arms. These results thus show how click-derived ligands can be tuned on demand for catalytic processes.

Solid-Supported Single-Component Pd(II) Catalysts for Polar Monomer Insertion Copolymerization

Heterogenized representatives of neutral phosphine sulfonato Pd(II) complexes for polar monomer insertion polymerization were prepared by two different approaches. [{κ2-(P,O)-(2-anisyl)2PC6H4SO2O}Pd(Me)L] (L = pyr, dmso, or Cl) complexes were physisorbed on inorganic substrates, namely, clay or silica. In addition, new phosphine sulfonato complexes bearing hydroxyl linker groups at the nonchelating P-aryl moiety were prepared. These complexes were covalently tethered to cross-linked polystyrene. All immobilized palladium complexes are active in ethylene polymerization and ethylene/MA copolymerization without any additional cocatalyst. In addition, separation from the polymer solution formed and reutilization for another polymerization were demonstrated for polystyrene-bound complexes.

Synthesis, structural characterization and cis–trans isomerization of novel (salicylaldiminato)platinum(ii) complexes

The reaction of cis-[PtCl₂(dmso)] with the salicylaldimine ligand, N-(2-hydroxybenzylidene)-2,6-di-isopropylaniline, LA in the presence of sodium acetate in methanol produced both cis- and trans-[PtClLA(dmso)], 1a and 1b. An analogous reaction for the less bulky ligand, N-(2-hydroxybenzylidene)aniline LB produced only cis-[PtClLB(dmso)], 2. The reactions of these dmso complexes with triphenylphosphine also yielded complexes with different geometries depending on the nature of the salicylaldiminato ligand. Thus the cis-trans isomerization of cis-[PtClLA(PPh₃)] 3a was investigated both experimentally and computationally, and a tetrahedral transition state was detected in this process. A good agreement of the experimental activation parameters with those determined theoretically using DFT was obtained. LA was also reacted with [PtClMe(cod)] in methanol to yield the corresponding salicylaldiminato complex 6 in which the methyl group is cis to the imine nitrogen. X-ray crystal structures of some compounds obtained are reported.

Synthesis, characterization, antiproliferative and anti-metastatic properties of two ruthenium–DMSO complexes containing 2,2′-biimidazole

Two new ruthenium complexes, trans,cis,cis-[RuCl 2(DMSO) 2(H 2biim)] ( 1) and mer-[RuCl 3(DMSO)(H 2biim)] ( 2) (DMSO = dimethyl sulfoxide and H 2biim = 2,2′-biimidazole), have been synthesized and fully characterized by single-crystal X-ray analysis. The less stable complex 2 is more cytotoxic against the four human cancer cell lines tested than 1. Further studies show that 1 and 2 exhibit cell growth inhibition by triggering G0/G1 cell cycle arrest and mitochondria-mediated apoptosis. Additionally, complex 2 exerts potent inhibitory effects on the adhesion and migration of human cancer cells comparable to that of NAMI-A ([ImH][ trans-[RuCl 4(Im)(DMSO-S)], Im = imidazole). Target validation studies show that cyclin-dependent kinases (CDKs), other than DNA, are more likely to be targets of 1 and 2.

New Ru(II)–DMSO complexes of ON/SN chelates: Synthesis, behavior of Schiff bases towards hydrolytic cleavage of C [dbnd]N bond, electrochemistry and biological activities

The reaction of cis-[RuCl 2(DMSO) 4] with salicylaldehyde semicarbazone in ethanol resulted in the chemoselective cleavage of the C N bond of the Schiff base, forming a complex in which the semicarbazide remains coordinated to the metal, as observed previously with trans-[RuCl 2(DMSO) 4]. In another set of reactions of cis-[RuCl 2(DMSO) 4] with 4-aminoantipyrine derivatives of salicylaldehyde, 2-hydroxy-1-naphthaldehyde and o-vanillin, C N cleavage was observed in all three cases yielding the same compound, [RuCl 2(DMSO) 2(4-aminoantipyrine)]. However, when the reactions, under the same experimental conditions, were extended to unsubstituted/N-substituted thiosemicarbazones of salicylaldehyde and 2-hydroxy-1-naphthaldehyde, no cleavage was observed. All the new complexes were characterized by analytical and spectroscopic techniques. The structures of two of the complexes, [RuCl 2(DMSO) 2(semicarbazide)]·2H 2O and [RuCl 2(DMSO) 2(4-aminoantipyrine)], were determined by single crystal XRD and are in support of the cleavage. The electrochemistry of the complexes was studied by cyclic voltammetry. Further, the preliminary DNA-binding ability and antibacterial activity of the complexes were studied.

Density functional theory and topological analysis on the hydrogen bonding interactions in N-protonated adrenaline–DMSO complexes

In this study, complexes formed via hydrogen bond interactions between N-protonated adrenaline (AdH+) and DMSO have been studied by density functional theory (DFT). The relevant geometries, energies, and IR characteristics of the hydrogen bonds (H-bonds) have been systematically investigated. The natural bond orbital (NBO) and the quantum theory of atoms in molecule (QTAIM) analysis have also been applied to understand the nature of the hydrogen bonding interactions in complexes. The H-bonds involving amino or hydroxyls as H-donor are dominant H-bonds in complexes and are attributed to strong H-bonds. The weak H-bonds, such as π H-bonds and H-bonds involving methyl (DMSO) or methenyls (C2H6 and C5H7 of AdH+) as H-acceptors, were found in complexes as well. The complexes in which the dominant H-bond involves amino of AdH+ as H-donor are more stable than those with the dominant H-bond involving hydroxyls as H-donor. Some relationships between various properties of QTAIM, NBO, geometry as well as frequency were also investigated.

Platinum(IV) DMSO Complexes: Synthesis, Isomerization, and Agostic Intermediates

Oxidation of cyclometalated Pt(II) complexes with S-bound DMSO ligands initially results in Pt(IV) complexes that retain the S-bound DMSO ligands in the same relative position. Isomerization reactions result in a rearrangement of the ligands to give O-bound DMSO complexes, with the DMSO trans to a cyclometalated carbon. X-ray structures representing the only two known examples of Pt(IV) complexes with O-bound DMSO ligands have been solved. The rate of isomerization of complexes without a pendant alkyl chain is strongly solvent dependent, consistent with the need to stabilize a coordinatively unsaturated intermediate. Pt(IV) complexes with a pendant alkyl chain show little dependence on isomerization rate with solvent, with solution NMR data strongly suggesting the presence of agostic complexes. DFT calculations provide support for the presence of agostic complexes, with the same interactions being used to account for the loss of DMSO from the O-bound DMSO complexes.

Tris(pyrazolyl)methane]ruthenium Complexes Capable of Inhibiting Cancer Cell Growth

AbstractThe [tris(pyrazolyl)methane]ruthenium complexes [(κ3‐tpm)RuCl(solv)2]PF6 [tpm = tris(pyrazolyl)methane; solv = MeCN, dmso] and [(κ3‐tpm)RuCl(LL)]PF6 [LL = κ2‐dppe, κ2‐dppp, κ2‐dppb, (PMePh2)2] have been prepared, characterized and screened in vitro for their antiproliferative properties against the MCF‐7 (breast) and HeLa (cervical) cancer cell lines by using the MTT assay. Although the MeCN and dmso complexes showed no activity under the conditions used, the phosphane complexes exhibited remarkable cytotoxic behaviour. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Theoretical Insight on the S → O Photoisomerization of DMSO Complexes of Ru(II)

Complexes of the type [Ru(tpy)(L)(dmso)](n+) (where tpy = 2,2':6',2''-terpyridine; L = 2,2'-bipyridine (bpy), n = 2; N,N,N',N'-tetramethylethylene diamine (tmen), n = 2; acetylacetonate (acac), n = 1; oxalate (ox), n = 0; malonate (mal), n = 0) were investigated by density functional theory (DFT). The results do not support a promoting role for the dsigma* ligand field (LF) states during excited state S --> O isomerization. Instead, the calculations show that the formation of a Ru(III) center is important in the isomerization, along with the identity of the ancillary bidentate ligand. The present work shows that the orbital contributions from the bidentate ligand to the HOMO, which is typically centered on the ruthenium, plays an important role in the photochemical and oxidative reactivity of the complexes.

Synthesis, characterization, electrochemical studies, DNA binding, and cleavage activity of mixed copper(II)oxime DMSO complexes

Mixed ligand complexes having molecular formulae Cu(L)2(DMSO)2 [where L ¼ salicylaldoxime (SAO), 2-hydroxyacetophenone oxime (HAO), and resacetophenone oxime (RPO)] have been synthesized and characterized by molar conductivity, magnetic susceptibility, UV–vis, IR, and ESR methods. The electronic and ESR spectra suggest distorted octahedral geometry for mixed ligand complexes. From ESR data all the complexes follow the order gjj 4g? 4 2.0037 showing covalent bonding nature and copper(II) (d 9 ) ion in axial symmetry with unpaired electron in dx27y2 orbital. Cyclic voltammetric studies show quasireversible reduction attributable to Cu 2þ /Cu þ . Absorption titration studies revealed that each complex is an avid binder of CT DNA. The apparent binding constants are in the range 3.2 6 10 5 to 2.4 6 10 6 . The cleavage activity of complexes was carried out on double-stranded pBR322 circular plasmid DNA using gel electrophoresis. All complexes show increased nuclease activity in the presence of oxidant (H2O2) and cleavage is strongly dependent on time of incubation and concentration of complex. Control cleavage experiment carried out in the presence of potential inhibitors, viz. dimethyl sulfoxide, tert-Butyl alcohol, ethylenediaminetetraacetic acid and NaN3, inhibits cleavage activity suggesting an oxidative mechanism with major active species involving . OH in cleavage of plasmid DNA.

Ru(II)–DMSO complexes containing aromatic and heterocyclic acid hydrazides: Structure, electrochemistry and biological activity

The reaction of cis-[RuCl 2(DMSO) 4] with a family of aromatic and heterocyclic acid hydrazides yielded new complexes of the general formula trans-[RuCl 2(DMSO) 2(hydrazide)] · nH 2O ( n = 0; 1– 6; n = 1; 7). The new complexes have been characterized by IR, UV–Vis and 1H NMR spectroscopic methods. In addition, the structure of one of the complexes, [RuCl 2(DMSO) 2(tcah)] · H 2O (tcah = thiophene-2-carboxylic acid hydrazide), has been determined by single crystal X-ray diffraction. All the studies reveal the neutral bidentate coordination of the hydrazide ligands through the acyl oxygen and amine nitrogen atoms. The electron transfer properties of the complexes were studied by cyclic voltammetry and all the complexes except one show an irreversible/quasi-reversible reduction wave (Ru II/Ru I) and an uncoupled oxidation peak (Ru III/ Ru II). The preliminary DNA-binding ability of the complexes, studied with herring sperm DNA, shows the binding of the complexes with DNA with a lesser affinity than classical intercalators. The complexes have also been screened for their antibacterial activity against five pathogenic bacteria.

New Ru(II)–dmso complexes with heterocyclic hydrazone ligands towards cancer chemotherapy

The synthesis and characterization of ruthenium(II) complexes, [RuCl 2(dmso) 2(bfmh)] ( 1; dmso = dimethyl sulfoxide, bfmh = benzoic acid furan-2-ylmethylene-hydrazide), [RuCl 2(dmso) 2(btmh)]( 2; btmh = benzoic acid thiophen-2-ylmethylene-hydrazide), [RuCl 2(dmso) 2(bfeh)]( 3; bfeh = benzoic acid (1-furan-2-yl-ethylidene)-hydrazide) and [RuCl 2(dmso) 2(bpeh)]( 4; bpeh = benzoic acid (1-pyridin-2-yl-ethylidene)-hydrazide) are described. The ligands, when treated with either cis-[RuCl 2(dmso) 4] or trans(Cl)–[RuCl 2(dmso) 2(bpy)], resulted in the same products. This has been confirmed by IR spectra and single crystal X-ray diffraction studies. The redox behaviors of the complexes have been found to be strongly dependent on the electronic nature of the moieties present in the hydrazone ligands. The binding of the complexes to Herring sperm DNA has been studied by absorption titration and cyclic voltammetry. But, due to the random change in the absorption on the addition of DNA, only a qualitative result rather than a quantitative result has been obtained. All the complexes have been found to bind DNA through different modes to different extents. The antibacterial properties of the ligands and the complexes have been studied against five pathogenic bacteria and also the minimum inhibitory concentrations (MIC) of all the ligands and complexes 2 and 4 have been evaluated.

Influence of the anionic ligands on the anticancer activity of Ru(II)–dmso complexes: Kinetics of aquation and in vitro cytotoxicity of new dicarboxylate compounds in comparison with their chloride precursors

We performed extensive studies on the kinetics of hydrolysis of a series of Ru(II)–dmso complexes containing dicarboxylate ligands, such as oxalate, malonate, succinate and 1,1-cyclobutane dicarboxylate (cbdc), derived from anticancer-active Ru(II)–dmso–Cl precursors. The in vitro antitumor activity of those compounds in comparison with their chloride precursors was evaluated against two tumor cell lines, the human KB oral carcinoma and the murine B16-F10 melanoma. The aim of this study was to assess how the nature of the anionic ligands (i.e. dicarboxylates vs. chlorides) affects the chemical behavior and the in vitro antitumor activity of Ru(II)–dmso complexes. Among the tested compounds only one complex, the dimer [fac-Ru(dmso-S)3(H2O)(μ-cbdc)]2 (5), exhibited moderate activity against both cell lines. Interestingly, this compound is the most kinetically stable in aqueous solution among those investigated. Despite the moderate in vitro activity, in an in vivo test, complex 5 exhibited no activity against both the primary tumor growth and the formation of spontaneous metastases on the MCa mammary carcinoma model.

An easy way to achieve three‐dimensional metal–organic coordination polymers: synthesis and crystal structure of dizinc diisophthalate bis‐dimethylsulfoxide monohydrate: [Zn2(ip)4(DMSO)2(H2O)·3 DMSO]n

AbstractAn easy way of producing three‐dimensional metal–organic coordination polymers involving zinc(II) benzene‐dicarboxylates is reported. The reaction of zinc oxide with benzene dicarboxylic acids in water yielded the expected hydrated zinc dicarboxylates. These zinc compounds were then suspended in dimethylsulfoxide and heated to above 100 °C for a couple of hours; the solutions were allowed after filtration to cool down to eventually deliver crystalline compounds displaying complex zeotype structures. The crystal structure of the title compound, [Zn2(ip)4(DMSO)2(H2O)·3 DMSO]n (ipH2 = isophthalic acid = 1,3‐benzenedicarboxylic acid, DMSO = dimethylsulfoxide), is reported for the first time and shows a three‐dimensional network where octahedrally and tetrahedrally coordinated zinc atoms (present in a 1:1 ratio) are linked by bridging isophthalate ligands. The complex coordination network exhibits a remarkable channel structure along the z‐axis. The related zinc terephthalate–DMSO complex was similarly prepared and the crystal structure determination revealed an already documented zeotypic structure: [{Zn4(OH)2(tp)3(DMSO)4} 2H2O]n (tpH2 = terephthalic acid = 1,4‐benzenedicarboxylic acid). Weak interactions as well as hydrogen bonds involving water molecules and carboxy groups play a major role in the formation of these complex three‐dimensional networks. In comparison, the zinc 1,2‐benzene‐dicarboxylate–DMSO complex could not be isolated, even under more drastic conditions. The higher symmetry of the coordination network found in the zinc terephthalate–DMSO complexes was incidentally corroborated by 13C CP/MAS spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.

Molecular association in dimethyl sulfoxide-nitromethane mixtures: Raman spectroscopy and quantum-chemical calculations

Dimethyl sulfoxide-nitromethane (DMSO-NM) binary mixtures have been studied. Intermolecular associates are formed in these mixtures via the interaction between DMSO and NM molecular dipoles and hydrogen bonding. Ab initio calculations have been carried out at the MP2 perturbation theory level using the 6-31G(d, p) basis set to determine the optimal ground state geometry for DMSO complexes with NM and correctly assign new vibrational bands of molecules in various types of mixed intermolecular associates.

Chemistry in Acetone Complexes of Metal Dications: A Remarkable Ethylene Production Pathway

Electrospray ionization can generate microsolvated multiply charged metal ions for various metals and ligands, allowing exploration of chemistry within such clusters. The finite size of these systems permits comparing experimental results with accurate calculations, creating a natural laboratory to research ion solvation. Mass spectrometry has provided much insight into the stability and dissociation of ligated metal cations. While solvated singly charged ions tend to shrink by ligand evaporation, solvated polycations below a certain size exhibit charge reduction and/or ligand fragmentation due to organometallic reactions. Here we investigate the acetone complexes of representative divalent metals (Ca, Mn, Co, Ni, and Cu), comparing the results of collision-induced dissociation with the predictions of density functional theory. As for other solvated dications, channels involving proton or electron transfer compete with ligand loss and become dominant for smaller complexes. The heterolytic C-C bond cleavage is common, like in DMSO and acetonitrile complexes. Of primary interest is the unanticipated neutral ethylene loss, found for all metals studied except Cu and particularly intense for Ca and Mn. We focus on understanding that process in the context of competing dissociation pathways, as a function of metal identity and number of ligands. According to first-principles modeling, ethylene elimination proceeds along a complex path involving two intermediates. These results suggest that chemistry in microsolvated multiply charged ions may still hold major surprises.

Synthesis and characterization of [M(DMSO)6][SnCl6] complexes (M = Fe2+, Co2+, and Ni2+) — An old mystery solved

The synthesis of an "unknown" Fe(II) complex originally reported in 1973 and formulated then as [Fe(DMSO)5Cl][SnCl4] was thoroughly reproduced and the compound reformulated as the novel [Fe(DMSO)6][SnCl6] double complex salt. Current elemental analysis and IR and Mössbauer spectroscopy matched the original 1973 data, and Raman spectroscopy and single crystal X-ray diffraction provided additional confirmation of our reformulation. [Fe(DMSO)6][SnCl6] (1) crystallizes in the trigonal space group R[Formula: see text] with octahedral [Fe(DMSO)6]2+ and [SnCl6]2– complex ions with an Fe—O bond length of 2.121(3) Å. The same synthesis was extended to Co(II) and Ni(II) to generate the novel [Co(DMSO)6][SnCl6] (2), which crystallizes in the triclinic space group P[Formula: see text] with a Co—O bond length of 2.093(4)–2.113(5) Å, and [Ni(DMSO)6][SnCl6] (3), which crystallized in the trigonal R[Formula: see text] space group and has a Ni—O bond length of 2.062(2) Å. The Sn—Cl bond length in all three complexes ranged from 2.421(2) to 2.448(2) Å.Key words: DMSO complexes of Fe(II), Co(II) and Ni(II), SnCl62– salts, IR, Raman and Mössbauer spectroscopy, X-ray crystal structures.

Replacement of Chlorides with Dicarboxylate Ligands in Anticancer Active Ru(II)-DMSO Compounds: A New Strategy That Might Lead to Improved Activity

A series of new Ru(II)-DMSO complexes containing dicarboxylate ligands (dicarb), namely, oxalate (ox), malonate (mal), methylmalonate (mmal), dimethylmalonate (dmmal), and succinate (suc), have been synthesized and structurally characterized. These compounds were prepared from the known Ru(II)-Cl-DMSO anticancer complexes cis,fac-[RuCl2(DMSO-S)3(DMSO-O)] (1) and trans-[RuCl2(DMSO-S)4] (2) and from the chloride-free precursor fac-[Ru(DMSO-S)3(DMSO-O)3][CF3SO3]2 (3), with the aim of assessing how the nature of the anionic ligands influences the biological activity of these species. Basically, the investigated ligands can be divided into two groups. The reaction of either 1 or 2 with K2(dicarb) (dicarb = ox, mal, mmal) yielded preferentially the mononuclear species [K]fac-[RuCl(DMSO-S)3(eta2-dicarb)] (dicarb = mal, 6; mmal, 9; ox, 14) that contains a chelating dicarboxylate unit and a residual chloride. Likewise, when 3 was used as a precursor, the neutral mononuclear species fac-[Ru(DMSO-O)(DMSO-S)3(eta2-dicarb)] (dicarb = mal, 7; mmal, 10; ox, 16), which contains a DMSO-O ligand in the place of Cl-, was obtained. On the contrary, K2(suc) and K2(dmmal) yielded preferentially the dinuclear species [fac-Ru(DMSO-S)3(H2O)(mu-dicarb)]2 (dicarb = dmmal, 11; suc, 13), with two bridging dicarboxylate moieties. The two water molecules in anti geometry have strong intramolecular H-bonding with the non-coordinated oxygen atoms of the carboxylate groups. The solid-state X-ray structural data showed that the preferential binding mode of the investigated dicarboxylates, either bridging (mu) or chelating (eta2), is dictated mainly by steric reasons. Oxalate, unlike the other dicarboxylates, has also the bridging bis-chelate (eta4,mu) coordination mode available: this was found in the dinuclear species [{fac-RuCl(DMSO-S)3}2(eta4,mu-ox)] (15) and [{fac-Ru(DMSO-O)(DMSO-S)3}2(eta4,mu-ox)][CF3SO3]2 (17). We also isolated the unprecedented neutral metallacycle, [fac-Ru(DMSO-S)3(eta3,mu-ox)]4 (18), in which each oxalate unit has one unbound oxygen atom. The new complexes were thoroughly characterized by 1-D (1H and 13C) and 2-D (H-H- COSY and HMQC) NMR spectroscopy in solution and by IR spectroscopy in the solid state. The molecular structures of 10 compounds, 6-11, 13, 15, 17, and 18, were determined by X-ray crystallography. The behavior of selected complexes in aqueous solution was investigated by 1H NMR spectroscopy.

Efficient Energy Conversion in Photochromic Ruthenium DMSO Complexes

The photochromic compounds trans- and cis-[Ru(tpy)(Mepic)(dmso)](OSO2CF3) (2 and 3, respectively; tpy is 2,2':6',2"-terpyridine; Mepic is 6-methyl-2-pyridinecarboxylate; dmso is dimethyl sulfoxide) and cis-[Ru(tpy)(Brpic)(dmso)](PF6) (4; Brpic is 6-bromo-2-pyridinecarboxylate) were prepared and characterized by single-crystal X-ray crystallography, electrochemistry, NMR, IR, and UV-vis spectroscopy. The geometry labels refer to the relationship between the carboxylate oxygen of the picolinate ligand and dmso. Electrochemical studies reveal that only the trans isomer shows S-to-O isomerization following oxidation of Ru(II) and O-to-S isomerization following reduction of Ru(III). The cis isomers of both complexes feature reversible one-electron Ru(III/II) couples. All complexes undergo phototriggered S-to-O isomerization following MLCT (metal-to-ligand charge transfer) excitation with quantum yields (Phi(S-->O)) of 0.79 (2), 0.011 (3), and 0.014 (4). The methyl group in 2 promotes isomerization by hindering rotation of the dmso ligand about the Ru-S bond. Computational results support this role for the methyl group. Relative energy calculations show that the barrier to rotation is approximately 8 kcal mol(-1). These results suggest that rotation is an important vibration for isomerization in photochromic ruthenium-dmso complexes.

Organotin Perfluorooctanesulfonates as Air‐Stable Lewis Acid Catalysts: Synthesis, Characterization, and Catalysis

The reactions of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane and dialkyltin dihalides with silver perfluorooctanesulfonate provided the corresponding sulfonates as hydrates. The number of water molecules (n) of hydration was dependent on the conditions. The distannoxane derivative was identified as n from 0.5 to 6, while in the hydrated mononuclear species and DMSO complexes n varied widely from 4 to 13. 119Sn NMR spectroscopy and conductivity measurements indicated the ionic dissociation of these compounds in solution. These compounds exhibited unusually high solubility in polar organic solvents. The ionic dissociation together with facile hydration probably causes the unusual solubility. The Lewis acidity of these compounds was found to be high among organotin derivatives on the basis of ESR spectra of superoxide/metal-ion complexes. In contrast to well-known organotin triflates, these compounds suffered no hydrolysis upon storage in open air. The high catalytic activity of the distannoxane 1 was exemplified for various carbon-carbon bond-forming reactions, such as Mukaiyama-aldol as well as -Michael reactions and allylation of aldehydes.