Sandro Calogero

X-ray and mössbauer studies of tricyclohexyltin(IV) halides. The crystal structures of (cyclo-C6H11)3SnX (X = F, Br and I)

Abstract The structures of tricyclohexyltin fluoride (I), bromide (II) and iodide (III) have been determined by X-ray analysis. Compound I crystallizes in the space group P 2 1 / m with a = 10.422(6), b = 17.238(9), c = 5.769(3) A, β = 104.6(1)° and Z = 2. Compounds II and III crystallize in the space group Pcmn with a = 10.427(6), b = 16.914(9), c = 11.366(6) A, Z = 4; and a = 10.400(6), b = 16.900(10), c = 11.400(4) A, Z = 4, respectively. All three structures consist of discrete tetrahedral ( cyclo -C 6 H 11 ) 3 SnX units. The temperature dependence of the Mossbauer resonance areas has been examined in order to obtain information about the relationship between chemical structure and lattice dynamics.

Crystal structure of tricyclohexyltin chloride

The structure of tricyclohexyltin chloride has been determined by X-ray analysis. The compound crystallizes in the space group P 2 1/ m with a 10.386(6), b 17.195(9), c 5.713(3) A,β 104.26(9)° and Z = 2. It consists of discrete tetrahedral (cyclo-C 6 H 11 ) 3 SnCl units. The departure from the regular tetrahedral geometry is less than that in tricyclohexyltin acetate. The quadrupole splitting value (Δ 3.49 mm s −1 ), so large as to have been attributed to a penta-coordinated geometry, is shown to be consistent with the tetrahedral geometry when distortions are taken into account in the treatment of the point charge model.

X-ray crystal analysis of tricyclohexyltin trifluoroacetate and Mössbauer data for (cyclo-C6H11)3SnO2CR′ (R′ = CH3, CH2CL, CHCL2, CCl3 and CF3)

Abstract The halogenocarboxylates (cyclo-C6H11)3SnO2CR′, (R′ = CH3, CH2Cl, CHCl2, CCl3 and CF3) have been prepared, and characterized by Mossbauer and IR spectroscopy. The crystal structure of (cyclo-C6H11)3SnO2CCF3 has been determined by X-ray analysis. The crystals are orthorhombic, space group Pcmn, with unit cell parameters a 14.390 ± 0.004, b, 13.427 ± 0.004, c 11.516 ± 0.003 A. The structure was resolved by Patterson methods and refined to an R value of 0.147. The coordination about the tin atom can be considered distorted trigonal-pyramidal or distorted tetrahedral. Mossbauer data are explained in terms of distortions of bond angles about the tin atom.

Mössbauer study of some disubstituted distannoxanes (R′COO)R2SnOSnR2(OOCR′) and (R′COO)R2SnOSnR2(OH)

Abstract Mossbauer parameters have been determined for a series of disubstituted distannoxanes of type A, (R′COO)R 2 SnOSnR 2 (OOCR′), and of type B, (R′COO)R 2 SnOSnR 2 (OH), (R = n-C 4 H 9 , CH 2 = CH, CH 2 = CHCH 2 and R′ = CH 3 , CH 2 Cl, CHCl 2 , CCl 3 , CF 3 ). A treatment of the data by the point-charge method has been carried out. Taken together with the published literature X-ray, IR, NMR and molecular weight data, the results are consistent with dimeric structures in which the tin atoms are in a trigonal-bipyramidal geometry. The quadrupole splitting, with fixed R′, increases on passing from the allyland butyl- to vinyl-haloacetate derivatives. It is inferred that this trend might be correlated with the structural packing of the skeleton of the very similar ladder-type dimeric structures formed by inter- and intra-molecular SnO bonds.

The crystal structure of dichlorodimethyltin(IV) 1/1 tetramethylurea adduct

Abstract The results of a single crystal X-ray diffraction study of dichlorodimethyltin(IV) 1/1 tetramethylurea adduct are reported. The compound is five-coordinated with a distorted trigonal bipyramidal geometry.

The crystal structure of a bis-carbene complex of gold(I), {[(trans,trans-p-CH3C6H4NH)2C]Au}BF4

Abstract In the compound [(Ar(H)NCN(H)Ar) 2 Au]BF 4 (Ar = p -tolyl) the two AuC bonds (2.02(1) A) are colinear (177.4(1)°). Both the HN hydrogens lie on the same side of the carbene ligands, on the side away from the gold atom, so that the two carbene ligands are in an unusual trans,trans -configuration.

The X-ray crystal structure of dichloro-S,S′-bis(o-methylcysteinato)tin(IV): the first determination of an inorganic tin—amino acid derivative

Abstract The crystal structure of dichloro-S,S′bis(O-methylcysteinato)tin(IV), Cl2Sn{SCH2CH(NH2)-CoOMe}2, has been solved by a three-dimensional Patterson synthesis: the crystals are orthorhombic, space group P212121, with cell parameters a = 16.621(9), b = 9.843(5), c = 10.323(5) A, Z = 4, refined to R = 0.0356 for 1715 observable reflections. The tin is coordinated to two cis-nitrogen and two trans- sulphur atoms from the O-methylcysteinato ligands, and to two cis- chlorine atoms, in an approximately octahedral arrangement. The bond distances in the tin coordination sphere are: SnCl 2.445 A, SnS 2.434 A and 2.446 A, and SnN 2.264 A and 2.309 A. This structure is compared with those of other octahedral cis-Cl2Sn(L2)2 complexes and the results of anti-tumour tests on these derivatives are reported. The lack of anti-tumour activity exhibited by the title compound may be associated with the large (99.4°) cisClSnCl bond angle.

The influence of phosphine ligands on the stoichiometry of mixed-ligand hexacoordinate iron(II) complexes with isocyanides and phosphines

The synthesis and characterization of complexes of the type [FeX(4-CH3-C6H4NC)nL5−n]ClO4 (X  Cl, Br, or I; n = 2, 3 or 4; L  PhPMe2, PhPEt2, Ph2PMe, Ph2PEt, or Ph2P(OEt) are described. The steric hindrance by the phosphine ligand is tentatively correlated with the influence of the π-acidity of phosphine and isocyanide ligands in determining the composition of these compounds. Their structures have been postulated on the basis of infrared and PMR spectra. Mossbauer parameters have also been determined at liquid nitrogen temperature by a treatment of the data by the point-charge model.

Mössbauer studies of some new hexacoordinate iron(II) complexes with isocyanides, phosphines and halides

Abstract Mossbauer parameters have been determined, at 80 K, for some new complexes of the type [FeX(CNR)5-nLn]ClO4(n  3, 2, 0; X  Br-, I-; L  PhP(OEt)2; R  4-CH3C6H4, 2-CH3C6H4, C6H5, 4-NO2C6H4, 4-CH3OC6H4, 2,6-(CH3)2C6H3 and [FeX2(4-CH3C6H4NC)4]. Treatment by the point-charge model has been carried out to rationalize quadrupole splitting and centre shift values for chloro, bromo and iodo derivatives. The structural assignments, by pqs parameters, are consistent with X-ray and IR data.

The crystal structure of the ternary tin(II) chalcogenide halide Sn7Br10S2

Abstract The X-ray crystal structure of Sn 7 Br 10 S 2 is reported. Sn 7 Br 10 S 2 is hexagonal with a = b = 12.185, c = 4.418 A, Z = 1. Space group P6 3 . There are three distinct tin sites and each tin atom lies in a partially occupied sixfold generals site of the hexagonal lattice. Two of the sites have tin environments that are typical of tin(II) materials but the third site is unusual. The arrangement of tin atoms in the cell requires the operation of co-operative disorder in the lattice. The anions occupy two sets of general positions in the cell with one set consisting only of Br atoms and the other having randomly distributed Br and S atoms.