Petr Švec

Pnictogen bonding in pyrazine•PnX 5 (Pn = P, As, Sb and X = F, Cl, Br) complexes

AbstractThis paper presents a study of pnictogen bonding in a series of pyrazine•PnX5 (Pn = P, As, Sb and X = F, Cl, Br) complexes. The whole series was studied computationally. Moreover, the pyrazine complexes with PCl5 and SbCl5 were prepared and characterized experimentally. It was found that the Pn-N distances are only slightly elongated when compared to the sum of covalent radii. The conformation of PnX5 changed considerably upon the complex formation, which resulted in a significant change of the dipole moment of the PnX5 fragment and a considerably more positive σ-hole on the pnictogen atom. Finally, interaction energies were decomposed in order to provide a deeper insight into the nature of the studied pnictogen-bonded complexes. Graphical abstractThe conformation of PnX5 changed considerably upon the complex formation, which resulted in a considerably more positive σ-hole on the pnictogen atom.

Use of C,N-chelated triorganotin(IV) fluoride for fluorination of organic compounds, coordination compounds, phosphines, silanes and stannanes

Abstract C,N-chelated triorganotin(IV) compounds containing the LCN ligand, where LCN is {2-[(CH3)2 NCH2]C6 H4} -, reveal the monomeric structure in solution as well as in the solid state with pentacoordinated tin atom in trigonal bipyramidal coordination polyhedra. These compounds were used as mild and very efficient metathetical fluorinating agents in fluorinations of various organic, inorganic substrates and organometallic species containing E-Cl (E = C, Si, P, S and metal) bond(s) (metal halides, phosphines, silanes, etc.) as well as the F ion selective carriers with low detection limits.

C,N-Chelated organotin(iv) azides: synthesis, structure and use within click chemistry

A set of tri- and diorganotin(IV) azides bearing 2-(N,N-dimethylaminomethyl)phenyl as a C,N-chelating ligand (LCN) has been prepared and structurally characterized. Triorganotin(IV) azides of the type LCNR2SnN3 (R = n-Bu (1) and Ph (2)) and (LCN)2(n-Bu)SnN3 are monomeric both in solution and in the solid state. The central tin atom in these species is five-coordinated with distorted trigonal bipyramidal geometry. Diorganotin(IV) azides of the type LCNRSn(N3)2 (R = n-Bu and Ph) are monomeric with trigonal bipyramidal geometry around the tin atom as well. Finally, (LCN)2Sn(N3)2 contains a six-coordinated tin atom with heavily distorted octahedral geometry due to the presence of two LCN units. The potential use of selected organotin(IV) azides 1 and 2 as useful building blocks within click chemistry was investigated. The reactions of 1 and 2 with various nitriles resulted in the formation of corresponding triorganotin(IV) tetrazolides (i.e. κ-N1: LCN(n-Bu)2Sn(5-MeCN4), LCNPh2Sn(5-MeCN4), LCN(n-Bu)2Sn(5-Me2NCH2CN4), LCNPh2Sn(5-Me2NCH2CN4); and κ-N2: LCN(n-Bu)2Sn(5-t-BuCN4), LCNPh2Sn(5-t-BuCN4), LCN(n-Bu)2Sn(5-PhCN4), LCNPh2Sn(5-PhCN4)). Similarly, the reaction of 1 and 2 with cyclooctyne provided corresponding C,N-chelated di-n-butyl/diphenyltin(IV) κ-N1 4,5,6,7,8,9-hexahydrocycloocta[d][1,2,3]triazol-1-ides. All azido complexes and products of the [3+2] cycloaddition reactions were characterized by the combination of elemental analysis, mass spectrometry, IR spectroscopy, multinuclear NMR spectroscopy and, in the case of crystalline materials, XRD analysis. In addition, DFT calculations were carried out within the click chemistry reactions in order to corroborate the preferred formation of the respective tetrazolide regioisomer.

Triorganotin(IV) esters of 2-{[ N -(2-oxo-2H-naphthalene-1-yliden)hydrazo]}benzoic acid, instability of the cyclohexyl derivative

Three triorganotin(IV) esters of 2-{[N-(2-oxo-2H-naphthalene-1-yliden)hydrazo]}benzoic acid were prepared and studied by IR and NMR spectroscopy and X-ray crystallography for the tributyl- and triethyltin(IV)-2-{[N-(2-oxo-2H-naphthalene-1-yliden)hydrazo]}benzoates (2, 3). These compounds are monomeric in solution with four-coordinate tin. The hydrazo tautomeric forms are present in chloroform solution as well as in the solid state. The coordination geometries of tin in 2 and 3 are trigonal bipyramidal with all three carbons in equatorial positions, one carboxylic oxygen and the quinone-type oxygen from adjacent molecules are in axial positions forming centrosymmetric dimers with the ring containing 20 members. The yield of the tricyclohexyltin(IV) derivative (4) is much lower than 2 or 3, with instability towards moisture in solution. The product of the reaction with water is the bis(µ2-hydroxo)-bis{2-{[N-(2-oxo-2H-naphthalene-1-yliden)hydrazo]}benzoato}tetracyclohexylditin (4a) dimer. The tin is five-coordinate in the solid state by two cyclohexyl and two hydroxy groups, the last coordination site is occupied by a monodentate carboxy group. The dimeric form of this compound remains in chloroform solution.

Sequential Camouflage of the arachno-6,9-C2B8H14 Cage by Substituents

Sequential methylation of arachno-6,9-C2B8H14 (1) led to a series of methyl derivatives and finally to the camouflaging of all boron positions by mixed persubstitution. Thus, deprotonation of 1 produced the [arachno-6,9-C2B8H13] anion (1(-)), the methylation of which with MeI in tetrahydrofuran proceeded on the open-face boron vertexes with the formation of 5-Me-arachno-6,9-C2B8H13 (2; yield 28%) and 5,8-Me2-arachno-6,9-C2B8H12 (3; yield 36%). Observed in this reaction was also a side formation of 2-Me-closo-1,6-C2B8H9 (4; yield 6%).The electrophilic AlCl3-catalyzed CH3(+) attack of the neutral 1 in neat MeI at ambient temperature afforded 1,3-Me2-arachno-6,9-C2B8H12 (5), while a 76-h heating at 120 °C generated a mixture of the di- and triiodo derivatives 1,2,3,4,8,10-Me6-5,7-I2-arachno-6,9-C2B8H6 (6) and 1,2,3,4,7-Me5-5,7,10-I3-arachno-6,9-C2B8H6 (7). On the other hand, a HOTf-catalyzed reaction between 1 and MeOTf at reflux resulted in the isolation of 2-TfO-1,3.4,5,7,8,10-Me7-arachno-6,9-C2B8H6 (8; Tf = CF3SO2; yield 65%). The compounds were characterized by multinuclear ((11)B, (1)H, (13)C, and (19)F) NMR spectroscopy, mass spectrometry, and elemental analysis, and the structures of compounds 1, 1(-), 5, and 6 were established by X-ray diffraction analysis.

Triorganotin(IV) cation-promoted dimethyl carbonate synthesis from CO2 and methanol: solution and solid-state characterization of an unexpected diorganotin(IV)-oxo cluster

Two novel C,N-chelated organotin(IV) complexes bearing weakly coordinating carborane moieties were prepared by the reaction of the corresponding C,N-chelated organotin(IV) chloride (i.e. LCNR2SnCl, R = n-Bu (1) and Ph (2); LCN = 2-(N,N-dimethylaminomethyl)phenyl)) with monocarba-closo-dodecaborate silver salt (AgCB11H12; Ag·3). Both products of the metathesis, [LCN(n-Bu)2Sn]+[CB11H12]− (4) and [LCNPh2Sn]+ [CB11H12]− (5), respectively, were characterized by both multinuclear NMR spectroscopy and elemental analysis. The instability of 4 and 5 towards water is discussed. The solid-state structure of LCN(n-Bu)2SnOH·B(C6F5)3 (4a) as a model compound with a Sn–O(H)⋯B linkage is also reported. The evaluation of the catalytic activity of 4 and 5 was carried out within the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2. While 5 was shown to be definitively inactive, presumably due to cleavage of the Sn–Ph bond, compound 4 exhibits a beneficial action, since it leads to an amount of DMC higher than the stoichiometry (nDMC/nSn(cat) = 1.5). In addition, the solid state structures of [BnNMe3]+[CB11H12]− (6) and [(n-Bu)20Sn10O2(OMe)6(CO3)2]2+·2[CB11H12]− (7), isolated as single-crystals and resulting from the recombination of 4 under the reaction conditions (methanol/CO2), were established by sc-XRD analyses within the term of this work as well. 6 and 7 were also fully characterized by IR spectroscopy, multinuclear NMR in solution and elemental analysis.