Search

Complementarity Determining Region 3 of the immunoglobulin (Ig) H chain (CDR-H3) lies at the center of the antigen-binding site where it often plays a decisive role in antigen recognition and binding. Amino acids encoded by the diversity (DH) gene segment are the main component of CDR-H3. Each DH has the potential to rearrange into one of six DH reading frames (RFs), each of which exhibits a characteristic amino acid hydrophobicity signature that has been conserved among jawed vertebrates by natural selection. A preference for use of RF1 promotes the incorporation of tyrosine into CDR-H3 while suppressing the inclusion of hydrophobic or charged amino acids. To test the hypothesis that these evolutionary constraints on DH sequence influence epitope recognition, we used mice with a single DH that has been altered to preferentially use RF2 or inverted RF1. B cells in these mice produce a CDR-H3 repertoire that is enriched for valine or arginine in place of tyrosine. We serially immunized this panel of mice with gp140 from HIV-1 JR-FL isolate and then used enzyme-linked immunosorbent assay (ELISA) or peptide microarray to assess antibody binding to key or overlapping HIV-1 envelope epitopes. By ELISA, serum reactivity to key epitopes varied by DH sequence. By microarray, sera with Ig CDR-H3s enriched for arginine bound to linear peptides with a greater range of hydrophobicity but had a lower intensity of binding than sera containing Ig CDR-H3s enriched for tyrosine or valine. We conclude that patterns of epitope recognition and binding can be heavily influenced by DH germ line sequence. This may help explain why antibodies in HIV-infected patients must undergo extensive somatic mutation in order to bind to specific viral epitopes and achieve neutralization.

Reactions of anhydrous CoX2 (X = Br−, SCN−) and Ni(ClO4)2 with N,N,N′,N′-tetraisobutylpyridine-2,6-dithiocarboxamides (S-dbpt), N,N,N′,N′-tetraisopropyl pyridine-2,6-dithiocarboxamides (S-dppt), and N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamides (S-dept) lead to the formation of [Co(S-dbpt)Br2] (1), [Co(S-dppt)(SCN)2] (2), and [Ni(S-dept)2]·(ClO4)2·H2O (3), respectively. The X-ray crystal structures of the three S-dapt ligands and three complexes along with spectroscopic analyzes are presented. The molecular structure investigations of the S-dapt ligands show that the thiamide planes are twisted with respect to the pyridine ring, which is more in the case of phenyl groups. The structures of the Co(II) complexes reveal that an increase in steric crowding on the amide side arms of the ligands has no substantial effect on the geometry adopted by the corresponding complexes. The Co(II) gives only 1 : 1 five-coordinate, ion-paired complexes with a distorted square pyramidal geometry. Ni(II), on the other ...

Summary To test whether mechanisms controlling the range of diversity of the developing antibody repertoire in C57BL/6 mice (IgH b ) operate similarly to those identified in BALB/c mice (IgH a ), we compared the sequences of VH7183-containing H-chain transcripts from sorted adult bone marrow C57BL/6 B-cell subsets with those previously obtained from BALB/c mice. Patterns of VDJ gene segment utilization and CDR-H3 amino acid composition, charge, and average length in C57BL/6 pro-B cells were similar, although not identical, to BALB/c pro-B cells. However, C57BL/6 mature, recirculating B cells failed to demonstrate the reduction in the use of VH81X and the narrowing in the range of variance of CDR-H3 hydrophobicity that characterizes B-cell maturation in BALB/c mice. To further test the ability of the C57BL/6 strain to discard B cells expressing highly charged CDR-H3s, we introduced a mutant IgH a DH allele that forces use of arginine, asparagine and histidine. Unlike BALB/c mice, C57BL/6 mice congenic for the charged DH maintained normal numbers of mature, recirculating B cells that were enriched for charged CDR-H3s. Together; these findings indicate that the mature C57BL/6 B-cell pool permits expression of immunoglobulins with antigen binding sites that are typically discarded during late stage bone marrow B-cell development in BALB/c mice.

Reactions of N,N-diisopropylisonicotinamide (L) with anhydrous CuCl2, CuBr2 and Cu(ClO4)2·6H2O yielded: (a) an ionic product with the molecular composition of [CuL2(H2O)4]·2[CuLCl3] 1; (b) a coordination polymer [CuL2Br2]n 2 and (c) a mononuclear complex [CuL4(C3H8O)2]·(ClO4)2] 3, respectively. Similarly, the reaction of N,N-diisobutylisonicotinamide (L′) with Cu(NO3)2·3H2O yielded a coordination polymer [{CuL′2(H2O)2}(NO3)2]n 4. The ligands L and L′ coordinate in a monodentate fashion through the pyridine nitrogen atom to the metal centers in complexes 1 and 3. However, complexes 2 and 4 are coordination polymers in which the corresponding ligands (L and L′) act as bridging bidentate between metal centers to form 1D double chains. All the four complexes form networks through coordination polymerization and/or hydrogen bonding.

Reaction of Co(ClO4)2 · 6H2O with N,N-diisopropylisonicotinamide (L) has yielded a 1-D coordination polymer [{Co(L)2(H2O)2}(ClO4)2(CH3COCH3)2(H2O)2] n (1). Complex 1 has been characterized by infrared (IR) and UV-Vis spectroscopies, thermal analysis, and single crystal X-ray diffraction techniques. The structure has alternate arrangement of parallel 1-D cationic metal-ligand chains and H-bonded anionic chains containing perchlorate, acetone and water in the lattice. Further hydrogen bonding among both chains leads to formation of 2-D networks along almost perpendicular planes. Interpenetrations of such perpendicular 2-D sheets create a 3-D supramolecular structure.

Reactions of M(NO3)2 · xH2O [M = Co(II), Ni(II), and Cu(II)] with N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides(O-daap) in CH3CN yield [Co(O-dmap)(NO3)2] (1), [Co(O-deap)(NO3)2] (2), [Co(O-dpap)(NO3)2] (3), [Ni(O-dmap)(H2O)3](NO3)2] (4), [Ni(O-deap)(H2O)2(NO3)](NO3)] (5), [Cu(O-deap)(NO3)2] (6), and [Cu(O-dpap)(NO3)2] (7). X-ray crystal structures of 1, 2, 4, 5, and 7 reveal that O-daap ligands coordinate tridentate to each metal, O–N–O, with nitrate playing a vital role in molecular and crystal structures of all the complexes. The coordination geometry in the two Co(II) complexes, 1 and 2, is approximately pentagonal bipyramidal with nitrate bonded in a slightly unsymmetrical bidentate chelating mode. [Ni(dmap)(H2O)3](NO3)2 (4) and [Ni(deap)(H2O)2(NO3)](NO3) (5) exhibit octahedral geometry, the former containing uncoordinated nitrate while the latter has one nitrate coordinated unidentate and the other nitrate outside the coordination sphere. The Cu(II) in [Cu(dpap)(NO3)2] (7) occupies a distorted squa...

Reactions of anhydrous copper(II) chloride with NaX (1 : 1 or 1 : 2) and AgX (1 : 2) containing appropriate N,N,N′,N′-tetraalkylpyridine-2,6-dicarboxamides(O-daap) in CH3CN yield monosubstituted five-coordinate [Cu(L1)Cl(CF3SO3)] (1), [Cu(L2)Cl(ClO4)] (2), [Cu(L3)Cl(ClO4)] (3), and six-coordinate [Cu(L2)(CF3SO3)2] · H2O (4) (X = −OClO3 and–OSO2CF3; L1 = N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamides; L2 = N,N,N′,N′-tetraisopropylpyridine-2,6-dicarboxamides; L3 = N,N,N′,N′-tetraisobutylpyridine-2,6-dicarboxamides). The structures of these complexes have been determined by X-ray crystallography. The Cu2+ in 1–3 adopts distorted square-pyramidal geometry, while 4 exhibits octahedral structure. Steric factors in conjunction with lattice effects and the nature of the anions are responsible for the variety in coordination spheres. These compounds undergo extensive intermolecular H-bonding to give to 2-D sheets extending along various planes.

Reaction of anhydrous copper(II) chloride with N,N,N′,N′-tetraisopropylpyridine-2,6-dicarboxamide (L) leads to the synthesis of [Cu2Cl4L2]·2CH3CN, 1. The ligand coordinates to each CuII ion in a bidentate fashion through pyridine nitrogen and only one of the carbonyl oxygen atoms of the amide group rather than using tridentate coordination mode O–N–O. The structure can be described as a dichloro bridged centrosymmetric dimer where the two copper centers are pentacoordinated in a square pyramidal fashion. The two pyramids are arranged sharing a basal edge with their apical positions oriented opposite to each other. The crystal packing investigations show a 2D sheet in the lattice held together by dimeric acetonitrile entities. Complex 1 shows weak antiferromagnetic coupled Cu2+ ions.

Palladium nanoparticles consisting of metallic cores and encapsulating shells serve as an intriguing catalytic model system. This investigation is aimed at enhancing our understanding of the surface composition of palladium nanoparticles synthesized in polyol and exploiting their encapsulating shells to understand the catalytic properties of the nanoparticles more rationally. We investigated the surface structure of palladium nanoparticles by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). FTIR spectra showed the presence of monoalkoxide species with tilted geometry. TGA further confirmed the presence of these species along with some adsorbed byproducts formed during the reaction. Atomic force microscopy (AFM) shows the presence of diffused negatively charged coatings on the surface of the nearly spherical nanoparticles.

The synthesis, structure and magnetic properties of two new tetranuclear copper(II) compounds [{Cu(S-dbpt)}2(μ-Cl)2][{CuCl2}2(μ-Cl)2] (S-dbpt; N,N,N′,N′-tetraisobutylpyridine-2,6-dithiocarboxamide) 1 and [{CuCl(S-dppt)}]2[{CuCl2}2(μ-Cl)2] (S-dppt; N,N,N′,N′-tetraisopropylpyridine-2,6-dithiocarboxamide) 2 are reported. Both compounds contain a cationic complex with copper(II) coordinated to the ligand through both the thioamide S atoms and pyridilic N atom and one chlorine atom. The structure of the cationic dinuclear entity [{Cu(S-dbpt)}2(μ-Cl)2]2+ in 1 consists of two square pyramids sharing a basal to apical edge. For compound 2, there are two cationic mononuclear complexes [{CuCl(S-dppt)}]+. Both compounds contain the same dinuclear chlorine bridged anion [{CuCl2}2(μ-Cl)2]2−, containing a planar [Cu2(μ-Cl)2] core. Magnetic susceptibility measurements show weak antiferromagnetic coupling between the Cu(II) ions in these anionic complexes (J = −077 cm−1 for 1 and 0.88 cm−1 for 2). The cationic complex of 1 shows a ferromagnetic interaction with J = +3.2 cm−1.

The ligand N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamide (L1 and abbreviated as deap) reacts with CoX2 ( X = PF 6 - , BF 4 - , ClO 4 - and NO 3 - ) salts to give the octahedral complexes, [Co(L1)2(CH3CN)](PF6)2 (1) and [ Co ( L 1 ) 2 ( H 2 O ) 2 ] ( X ) 2 · H 2 O ( X = PF 6 - ( 2 ) , BF 4 - ( 3 ) , ClO 4 - ( 4 ) and NO 3 - ( 5 ) . The compounds have been characterised by elemental analysis, IR spectroscopy and X-ray crystallography. The composition of the product is dependant upon the nature of the reaction medium. Compound 1 contains ON and ONO bonded deap ligands in bidentate and tridentate coordinating modes, in which the coordination sphere of the Co2+ ion is completed by attachment of an acetonitrile molecule. Compounds 2 and 4 have identical cationic species [Co(L1)2(H2O)]2+ in which Co2+ is bonded by deap ligands in a bidentate ON mode. As deap is coordinating in a bidentate mode, the two coordinating water molecules are placed cis to each other in the octahedral arrangement. The similarity of the molecular structure of compounds 2 and 4 is, interestingly, also reflected in their crystal structures, both are structurally similar with a C2/c space group in the monoclinic crystal system. In the crystal lattice, due to the symmetrical disposition of the complex on a twofold axis, there is an interesting chain of molecules formed through hydrogen bonding. The lattice water has a crucial role in the formation of this chain, in fact it acts as a connecting link between the complex molecules running almost perpendicular to the ‘ac’ plane.

Mononuclear cobalt(II) complexes [Co(S-dept)X2] [X = Br (1), I (2) and NCS (3)] were synthesized using N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamide (S-dept), and characterised by conductivity, spectral and single-crystal X-ray diffraction studies. These studies reveal that the compounds consist of discrete monomeric molecules in which the cobalt atoms are five-coordinate in an environment that is best described as being distorted square-pyramidal. In dimethylformamide the iodo complex shows significant ionic dissociation (1:1 electrolyte) and its crystal field absorption spectrum is interpretable in terms of an octahedral structure [Co(S-dept)(DMF)2I]+. The temperature dependence of the magnetic susceptibility data is indicative of a high-spin compound with an important zero-field splitting. The best fitwas obtained with |D| = 20.5 cm–1 and g = 2.53 for 1, |D| = 14.2 cm–1 and g = 2.38 for 2 and |D| = 17.7 cm–1 and g = 2.35 for 3. The X-band EPR spectra at low temperature is also characteristic of an S = 3/2 state with important zero-field splitting. The most important band appears at low fields (ca. 1200 G). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The systematic investigation of electronic effects on the coordination geometry of nickel(II) thiocyanate complexes with the tridentate N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamide (S-dept) and N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamide (O-deap) ligands shows a significant change in the geometry of the metallic site. Their complexes conform to composition [Ni2(μ-NCS)2(S-dept)2(NCS)2] (1), [Ni(NCS)2(O-deap)(CH3CN)] · CH3CN (2) and [Ni(NCS)2(O-deap)(C2H5OH)] (3), respectively. X-ray crystallographic studies were done for 1–3. In the crystal lattice, complex 1 exists as a centrosymmetric dimer in which the dinuclear core is bridged by two N-bonded thiocyanate groups. The near octahedral geometry of the nickel atom is achieved through the two bridging N atoms of the thiocyanate groups, three SNS donor atoms of the ligand S-dept and through the terminal nitrogen atom of a non-bridging thiocyanate moiety. To the best of our knowledge, complex 1 presents the first example in literature with the highest asymmetry in N-bridging thiocyanato ligands. Ni ion is coordinated to ONO donor set of atoms of O-deap and two N-bonded NCS terminal groups. The sixth coordination site is completed by the N atom of an acetonitrile molecule. The coordination around Ni atom in 3 is also distorted octahedral. The change in the sixth coordination position from acetonitrile in 2 to ethanol in 3 has a profound influence in the overall topology of the metal–ligand complex. The complex interplay of weak interactions in stabilizing the 3-dimensional lattice of these molecules is well demonstrated.

The crystal and molecular structure of a 2:1 complex of CoCl2 with DETP (N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamide), has been determined. The compound is built up from {Co(DETP)(Cl)}+ and [Co2Cl4(μ2−Cl)2]2− groups. The cobalt atom in the cation is bonded to two sulphur atoms, a pyridilic nitrogen atom of the DETP ligand, and a chlorine atom in a distorted square planar geometry. The {Co(DETP)(Cl)}+ units are stacked over each other in a staggered manner so that each cobalt atom interacts weakly with a sulphur atom of a unit above and below it. The anionic cobalt is present as the centrosymmetric [Co2Cl4(μ2−Cl)2]2− ion in which two chlorine bridges complete tetrahedral coordination about the cobalt atoms.

A series of dinuclear copper(II) complexes (1), (2), (3) and (4) containing dimethylpyridine-2,6-dicarboxylate were synthesised and structurally characterised to delineate the role of the steric demand in deciding the observed coordination mode. In contrast to the bulky isopropyl derivative with symmetrical O-sp2 carbonylic coordination, the less sterically demanding methyl derivative adopts an unusual asymmetric coordination involving both O-sp2 carbonylic and O-sp3 alkoxy atoms of the ester moiety. However, the symmetric O-sp2 carbonylic coordination is reestablished upon dissolution in MeOH. In the absence of a sterically encumbered [Cu2(μ-Cl)2] core in (2), (3) and (4), the coordination reverts to the symmetrical carbonylic oxygen coordinating mode, underscoring the importance of overall space availability (steric demand) in and around the coordination sphere of the metal atom. Associated with these differential coordination modes, interesting structural dissimilarities are encountered in both the coordinating ligand and the coordination sphere of the copper centre. Besides X-ray crystallographic investigations on (1) and (2), culminating evidence is gathered through i.r., u.v.–vis. spectra and magnetic susceptibility measurements.

A number of alkyltin(IV) paratoluenesulfonates, R n Sn(OSO 2 C 6 H 4 CH 3 -4) 4-n (n = 2, 3; R = C 2 H 5 , n-C 3 H 7 , n-C 4 H 9 ), have been prepared and IR spectra and solution NMR ( 1 H, 13 C, 119 Sn) are reported for these compounds, including (n-C 4 H 9 ) 2 Sn(OSO 2 X) 2 (X = CH 3 and CF 3 ), the NMR spectra of which have not been reported previously. From the chemical shift δ( 119 Sn) and the coupling constants 1 J( 13 C, 119 Sn) and 2 J( 1 H, 119 Sn), the coordination of the tin atom and the geometry of its coordination sphere in solutions of these compounds is suggested. IR spectra of the compounds are very similar to that observed for the paratoluenesulfonate anion in its sodium salt. The studies indicate that diorganotin(IV) paratoluenesulfonates, and the previously reported compounds (n-C 4 H 9 ) 2 Sn(OSO 2 X) 2 (X = CH 3 and CF 3 ), contain bridging SO 3 X groups that yield polymeric structures with hexacoordination around tin and contain non-linear C-Sn-C bonds. In triorganotin(IV) sulfonates, pentacoordination for tin with a planar SnC 3 skeleton and bidentate bridging paratoluenesulfonate anionic groups are suggested by IR and NMR spectral studies. The X-ray structure shows [(n-C 4 H 9 ) 2 Sn(OSO 2 C 6 H 4 CH 3 -4) 2 .2H 2 O] to be monomeric containing six-coordinate tin and crystallizes from methanol-chloroform in monoclinic space group C2/c. The Sn-O (paratoluenesulfonate) bond distance (2.26(2) A) is indicative of a relatively high degree of ionic character in the metal-anion bonds.

Reactions of di-n-butyltin(IV) oxide with 4'/2'-nitrobiphenyl-2-carboxylic acids in 1:1 and 1:2 stoichiometry yield complexes [{(n-C 4 H 9 ) 2 Sn(OCOC 12 H 8 NO 2 -4'/2')} 2 O] 2 (1 and 2) and (n-C 4 H 9 ) 2 Sn(OCOC 12 H 8 NO 2 -4'/2') 2 (3 and 4) respectively. These compounds were characterized by elemental analysis, IR and NMR ( 1 H, 13 C and 119 Sn) spectroscopy. The IR spectra of these compounds indicate the presence of anisobidentate carboxylate groups and non-linear C-Sn-C bonds. From the chemical shifts S ( 119 Sn) and the coupling constants 1 J( 13 C, 119 Sn), the coordination number of the tin atom and the geometry of its coordination sphere have been suggested. [{(n-C 4 H 9 ) 2 Sn(OCOC 12 H 8 NO 2 -4')} 2 O] 2 (1) exhibits a dimeric structure containing distannoxane units with two types of tin atom with essentially identical geometry. To a first approximation, the tin atoms appear to be pentacoordinated with distorted trigonal bipyramidal geometry. However, each type of tin atom is further subjected to a sixth weaker interaction and may be described as having a capped trigonal bipyramidal structure. The diffraction study of the complex (n-C 4 H 9 ) 2 Sn(OCOC 12 H 8 NO 2 -4') 2 (3) shows a six-coordinate tin in a distorted octahedral frame containing bidentate asymmetric chelating carboxylate groups, with the n-Bu groups trans to each other. The n-Bu-Sn-n-Bu angle is 152.8° and the Sn-O distances are 2.108(4) and 2.493(5) A. The oxygen atom of the nitro group of the ligand does not participate in bonding to the tin atom in 1 and 3. Crystals of 1 are triclinic with space group P1 and of that of 3 have orthorhombic space group Pnna.

The development of a transformation system is a significant technical hurdle in the study of many filamentous fungi. Recently Agrobacterium tumefaciens was shown to transform several filamentous fungi, but until now only one independent confirmation of this promising finding has been published. Fusarium circinatum (teleomorph Gibberella circinata ) is an important pathogen of pine that has not been transformed previously. A. tumefaciens strain AGL1(pPK2) transformed three different isolates of F. circinalum with an efficiency of 2-150 transformants 10 −5 conidia. The T-DNA was integrated into the genome and was stable through mitotic and meiotic cell divisions. Most F. circinatum transformants contained a single T-DNA copy. Half of the tested transformants also contained non-T-DNA vector sequences. These findings should facilitate future analysis of F. circinatum pathogenicity and stimulate wider use of this valuable transformation method in fungal research.

The X-ray crystal structures of [(n-C4H9)2Sn{μ-OSO2C6H2(CH3)3}2]n (1) and [(n-C4H9)2Sn{(μ-OH)(μ-OSO2C6H2(CH3)3)}]n (2) were determined to delineate the coordination behaviour of the sulphonate group with tin(IV) and to evaluate the metal sulphonate bonding interactions. The synthesis of 1 has been achieved by azeotropic dehydration of di-n-butyltin(IV) oxide and mesitylenesulphonic acid. 1 is polymeric containing six-coordinate tin and crystallizes from anhydrous toluene in the orthorhombic space group P21212 with unit cell dimensions a=12.555(1), b=21.238(1), c=5.415(1) A; Z=2; R, 0.0236 and wR, 0.0607 for 1281 observed reflections. The structure exhibits highly symmetrical bridging bidentate mesitylenesulphonate groups and is made up of an infinite array of (n-C4H9)2SnO4 moieties. Compound 1 hydrolyzes very slowly to [(n-C4H9)2Sn{(μ-OH)(μ-OSO2C6H2(CH3)3)}]n (2), when kept in CH3OH–CHCl3 mixture at room temperature for 35 days. Crystals of 2 are monoclinic with space group P21/m and unit cell dimensions a=10.040(1), b=14.500(1), c=13.978(1) A; β=91.58(1)°; Z=4; R, 0.0226; wR, 0.0592 for 2725 observed reflections. The crystal structure is built of polymeric chains in which [{(n-C4H9)2Sn}2(OH)2] units are joined by bridging bidentate meistylenesulphonate groups. The crystal lattice is stabilized by a network of hydrogen bonds running through the sheets, in which an oxygen atom of the sulphonate group and the hydroxyl group attached to tin participate in a symmetrical fashion. In DMSO solutions, chemical shift (119Sn) and 1J (119Sn–13C) values for both 1 and 2 suggest a distorted octahedral geometry around tin in which DMSO may also be involved.

The title compound N,N,N′,N′-tetraethylpyridine-2,6-dicarboxamide (DEAP) forms a 1:1 complex with anhydrous CuCl2, [Cu(DEAP)Cl2], (1) which was crystallized from EtOH solution in the monoclinic space group P21/ n with cell constant, a = 10.024(1); b = 13.122(1); c = 14.404(1) A β = 101.31(1)° V = 1857.8(3) A3 and Z = 4. The chloro-perchlorato complex, [Cu(DEAP)Cl(ClO4)], (2) obtained in near quantitative yield by reacting (1) with an excess of NaClO4 in EtOH, crystallized in the monoclinic space group P21/ n with cell constants, a = 7.965(1); b = 25.827(2); c = 10.046(1) A β = 98.81(1)° V = 2042.2(4) A3 and Z = 4. Both (1) and (2) contain 5-coordinated copper linked to DEAP through O∼N∼O donor set of atoms with covalently bonded chlorine atoms in (1) and chlorine and perchlorate groups in (2). The coordination geometry is intermediate between square pyramidal and trigonal bipyramidal, and is probably best described as a trigonally distorted rectangular pyramid.

The isomeric trimethyltin(IV) 1- and 2- naphthoates have been prepared in high yield from trimethyltin chloride and the appropriate sodium naphthoate in THF solution. Spectroscopic data for the compounds point to the presence of monomers, probably with a tetrahedral structure in CDCl3 solution, but five-coordinate trigonal bipyramidal units in the donor solvent DMSO. An X-ray structure of the 2-isomer shows an infinite zig-zag chain structure in which the carboxylate group bridges asymmetrically between pairs of tin atoms, which have distorted trigonal bipyramidal geometry. Much of the distortion can be traced to a weak residual chelating effect from the carboxylate group.

Some methyltin(IV) sulphonates, MenSn(OSO2X)4‒n (n = 1−3 and X = 4-tolyl and 2-naphthyl) have been prepared. The 1H, 3C and 9Sn NMR spectra of these compounds and the previously reported compounds, Me3Sn(OSO2X) (X = CF3, CH3 and 4-CH3 C6H4) and Me2Sn(OSO2CH3)2, in coordinating and non-coordinating solvents have been studied. From the chemical shifts δ(9Sn) and the coupling constants 1J(13C, 119Sn) and 2J(1H, 119Sn), coordination number of the tin atom and the geometry of its coordination sphere have been suggested. These observations have been complemented by IR spectroscopy. Synthesis of the ternary compounds, MeSnCl(OSO2X)2 (X = CH3 and 4-CH3C6H4), by reaction between Me3Sn(OSO2X) and Me2SnCl2 and subsequent cleavage of the tin-carbon bond is also discussed.

Two similar synthetic pathways using the ligand N,N-diisobutylisonicotinamide (L) with anhydrous CoX(2) salts (being X = Cl(-), Br(-)) led to different species: a one-dimensional system, [CoLCl(2)](n), 1, and an ionic product [Co(L)(2)(H(2)O)(4)][CoLBr(3)](2)·2H(2)O, 2, respectively. Compound 1 is a polymer in which ligand L coordinates to tetrahedral Co(II) ions in a bidentate bridging fashion using the pyridine nitrogen and carbonyl oxygen atoms. Compound 2 consists of one octahedral cationic [Co(L)(2)(H(2)O)(4)](2+) entity and two tetrahedral anionic [CoLBr(3)](-) units. In this system, the ligand molecules coordinate only through the pyridine nitrogen atoms. The magnetic properties of 1 and 2 were investigated in the temperature range of 2.0 to 300.0 K and correlations between both (due to the existence of similar features) examined. The study of the magnetic properties of 1 was carried out by considering each Co(II) ion as a perfectly isolated system, hence, J = 0, but taking into account a significant zero-field splitting contribution due to distortions on the tetrahedral environment of the cobalt atoms. The fit of the magnetic susceptibility data together with reduced magnetization vs H/T measurements provided similar parameters (|D| = 10.8 cm(-1), g(⊥) = 1.92, g(‖) = 2.92 for the former and |D| = 11.04 cm(-1)and g = 2.05 for the latter, respectively). On the other hand, the magnetic response of compound 2 has been analyzed using a model which considers the presence of two tetrahedral and one octahedral Co(ii) ions (Co(Td) and Co(Oh)). The study was carried out in two separated blocks, above and below 80 K, where only the most significant effects at each interval of temperature were considered. As a result, the analysis of the magnetic data shows weak antiferromagnetic interactions between the Co(Oh)and the two Co(Td) ions (J = -0.41 cm(-1)) in 2. The best fit parameters were g(Co(Td)) = 2.89, g(Co(Oh)) = 3.50, |D(Co(Td))| = 10.62 cm(-1), |E(Co(Td))| = 2.95 cm(-1), Δ = 240.9 cm(-1) and J(L-S) = -107.1 cm(-1), from where λ was calculated with a final value of -144.8 cm(-1) (J(L-S) = Aκλ). The approximations performed to obtain these values provide reasonable results in agreement with compound 1 and also to other systems in the literature.

Reaction of anhydrous CoCl(2) with N,N'-diisopropylisonicotinamide (L) has yielded a coordination polymer containing linear trinuclear [Co(3)L(4)Cl(6)] units with a rare, mixed Co(T(d))-Co(O(h))-Co(T(d)) assembly (compound 1). The central Co(II) ion, of each trinuclear entity, exhibits a distorted octahedral geometry, with two ligand molecules coordinating through their carbonyl oxygen atoms along with two bridging Cl(-) ions and two pyridine N atoms from the neighboring molecules. Also, in each unit, two outer Co(II) ions display distorted tetrahedral geometry, coordinating to one ligand molecule through the pyridine N atom and to three Cl(-) ions (one of them bridged to the central Co(II) and the two acting as a terminal ligands). The magnetic properties of this compound were investigated in the temperature range of 2.0 to 300.0 K. Owing to the complexity of the system and the weak interactions among trinuclear aggregates, the magnetic response has been analyzed using a model which considers these units as isolated systems. In addition, magnetic data has been examined in two separated blocks, above and below 50 K, applying programs VPMAG FORTRAN and MAGPACK-fit, respectively. This way, only the most significant effects at each interval of temperature were considered: spin-orbit coupling of the Co(O(h)), at high temperatures and zero-field splitting parameters of the Co(T(d)) at the low. Spin-spin magnetic interaction has been taken into account for the whole range of temperatures. As a result, the analysis of the magnetic data shows that, within every trinuclear unit, the central position matches well with a high-spin Co(II) (S = 3/2) and also reveals weak ferromagnetic interactions between the Co(O(h)) and the two terminal Co(T(d)) ions (J = +0.34 cm(-1)).

The synthesis, structure, and magnetic properties of two new tetranuclear Cu(II) complexes containing N,N,N',N'-tetraethylpyridine-2,6-dithiocarboxamide (S-dept) of formula [Cu(2)Cl(2)(mu-S-dept)(2)][Cu(2)Cl(4)(mu-Cl)(2)] (1) and [Cu(2)(mu-Cl)(2)(S-dept)(2)][CuCl(3)(EtOH)](2) (2) are reported. Their X-ray crystal structures reveal that the complexes are composed of anionic and cationic dimers, that in both cases contain the metal centers which interact via Coulombic and/or hydrogen bonding interactions. In both cases, the Cu centers in the anionic moieties adopt a slightly distorted tetrahedral geometry whereas for the cationic moieties they adopt a square-pyramidal type of geometry. Magnetic susceptibility data show that compounds 1 and 2 present an overall antiferromagnetic behavior arising from the contribution of both anionic and cationic moieties. For 1, the best fit obtained gave J(1) = -2.62 +/- 0.19 cm(-1), J(2) = -19.54 +/- 0.47 cm(-1), and g(2) = 2.164 +/- 0.004 cm(-1) (R = 8.28 x 10(-5)) whereas for 2 it gave J(1) = 4.48 +/- 2.73 cm(-1), g(1) = 2.20 +/- 0.03, J(2) = -11.26 +/- 2.01 cm(-1), and g(2) = 2.10 +/- 0.03 (R = 1.15 x 10(-4)). The nature of the superexchange pathways in 1 and 2 is discussed on the basis of structural, magnetic, and molecular orbital considerations. Theoretical calculations are performed at the extended Huckel level in order to obtain their molecular orbitals and energies using their crystallographic data.

The 127I Mössbauer spectra of a series of mono- and diaryliodine(III) carboxylates have been recorded at 4.2 K. The observed parameters are shown to be strongly dependent on the primary bonding arrangement about iodine only and the secondary bonding interactions have little or no effect. The crystal and molecular structure of bis(trifluoroacetato)pentafluorophenyliodine(III), (C6F5)I(O2CCF3)2, has been determined. Crystals are triclinic, of space group [Formula: see text], witsh a = 5.732(2) Å, b = 12.127(4) Å, c = 29.658(9) Å, α = 116.53(2)°, β = 98.02(2)°, γ = 117.09(2)°, V = 1482.0(8) Å3, Dc = 2.33 g cm−3 for Z = 4, and R1 = 0.0420 (R2 = 0.0431) for 2722 reflections with I > 3σ(I). The two independent molecules in the asymmetric unit have essentially the same primary geometry about the central iodine, a distorted T-shaped AX3E2 arrangement. Keywords: 127I Mössbauer, aryliodine(III) carboxylates, crystal structure, (C6F5)I(O2CCF3)2.

The compounds seleninyl bis(trifluoromethanesulphonate) (1) and seleninyl bis(acetate) (2) have been prepared and characterized by elemental analysis, ir and Raman spectroscopy, and X-ray crystallography. Crystals of 1 are monoclinic, space group P21/n with a = 12.735(1) Å, b = 5.163(4) Å, c = 16.133(2) Å, β = 96.426(8)°, U = 1054 Å3, Dx = 2.48 g cm−3 for Z = 4, R = 0.038 for 1745 observed reflections with I > 2.5σ(I). Those of 2 are orthorhombic, space group Pcab with a = 6,845(3) Å, b = 8.992(2) Å, c = 23.560(9) Å, U = 1450 Å3Dx = 1.95 g cm−3 for Z = 8, R = 0.074 for 1073 observed reflections with I > 3.0σ(I). The primary geometry of the Se atom in SeO(O3SCF3)2 is AX3E with a Se=O distance of 1.571(3) Å and Se—O bond lengths to the CF3SO3 ligands of 1.902(3) and 1.922(3) Å. Completing the overall coordination geometry of the Se atom are 2 intramolecular and 4 intermolecular Se … O contacts which are less than van der Waals limits. The overall coordination geometry is somewhat irregular since the two triflate anions are significantly differently arranged with respect to the SeO3E tetrahedron. The crystal packing consists of layers of interacting molecules. In 2 there is some disorder. However, the major arrangement of the molecule has Se=O and Se—O(1), Se—O(3) distances to the acetate ligands of lengths 1.575(9), 1.847(7), and 1.831(8) Å respectively. The overall geometry of the Se atom in this compound is completed by two intramolecular secondary Se … O contacts involving the second O atoms of both acetates and two intermolecular contacts involving the seleninyl oxygen atom and atom O(2) of an acetate group in two different symmetry related molecules. Overall, the crystal packing consists of essentially centrosymmetric dimeric units linked together through Se=O—Se bridges. A 1:2 adduct of 1 with pyridine has also been prepared and characterised.

Chromyl Chloride reacts with carboxylic acids [RCOOH where R = C2H5, n-C3H7, CH2CI, CHCl2 and CCI3] to give reduced chromium(III) carboxylates, [Cr3 O(OOCR)6 (H2O)3 ]Cl. Magnetic susceptibility, UV-visible and IR measurements are all consistent with their trinuclear basic structures. Reactions of chromyl chloride with carboxylic acid anhydrides [(RCO)2O where R = CH3 , C2H5 and n-C3H7 ] give dinuclear oxo-bridged complexes of the type, [Cr2O(OOOCR)3 ]Cl. These compounds behave as non-electrolytes in polar organic solvents. IR spectra suggest the presence of bridging carboxylato groups containing Cr-O -Cr chains. Their low magnetic moment values suggest polymeric structures exhibiting antiferromagnetic coupling between Cr atoms.

Anhydrous iron(III) chloride reacts with pure carboxylic acids RCOOH [where R = C2H5, n-C3H7, CH2Cl, CHCl2 and CCl3] at low temperature to yield Fe2Cl5 (OOCR)·nRCOOH [n = 3 when R = C2H5 and n-C3H7 and n = 2 when R = CH2Cl, CHCl2 and CCl3] and [Fe3O(OOCR)6(H2O)3][FeCl4] at about 70–80°C. These reactions reveal that no hydrogen chloride is evolved but an acyl chloride is formed. Pyridine combines with [Fe3O(OOCR)6(H2O)3][FeCl 4] (R = C2H5 and n-C3H7) to form [Fe3O(OOCR)6(C5H5N)3][FeCl4]. Piperidine, on the other hand, reacts with the elimination of piperidinium chloride to form [Fe3O(OOCR)6(H2O)3][Fe(NC5H10)4] compounds containing covalently bonded piperidide. Compounds containing polyatomic ligands such as NO3− and NCS− instead of the chloro group in [Fe3O(OOCR)6(H2O)3][FeCl4] (R = C2H5 and n-C3H7) have been prepared. All these compounds have been characterized on the basis of IR, UV-vis., molar conductance, molecular weight and room temperature magnetic susceptibility measurements.

The compounds trichloroselenium(IV) and trichlorotellurium(IV) sulfonates, MCl3(XSO3) (M = Se and Te; X = CF3, CH3, and p-CH3C6H4), have been prepared and characterized by elemental analysis and infrared spectroscopy. Infrared spectra suggest that the XSO3− group acts as a monodentate ligand in the Se compounds and as a tridentate ligand in the Te compounds. MCl3(CF3SO3) (M = Se and Te) are found to act as CF3SO3− ion acceptors, and compounds (C2H5)4N[MCl3(CF3SO3)2] have been isolated. Some other reactions involving ligand substitution and complex formation have also been investigated. Reactions of potassium tellurate(IV) with trifluoromethane-, methane-, and paratoluenesulfonic acids are seen to yield K2[Te(CF3SO3)6], K2[Te(CH3SO3)6] and K2[TeO(p-CH3C6H4SO3)4], respectively. Keywords: trichloroselenium(IV) sulfonates, trichlorotellurium(IV) sulfonates, tetraethylammonium trichlorobis(trifluoromethanesulfonato)selenate(IV), tetraethylammonium trichlorobis(trifluoromethanesulfonato)tellurate(IV), IR spectra.

{sup 127}I Moessbauer spectra have been recorded at 4.2 K for a series of tris(carboxylato)iodine(III) derivatives. The observed Moessbauer parameters appear to be influenced only by the primary bonds to iodine. Details of the preparation of a Mg{sub 3}{sup 127m}TeO{sub 6} source for {sup 127}I Moessbauer spectroscopy are given. The crystal and molecular structure of tris(acetato)iodine(III). I(O{sub 2}CCH{sub 3}){sub 3}, has been determined. The crystals are monoclinic, of space group P2{sub 1}/c, with a = 6.630 (1) {angstrom}, b = 8.047 (3) {angstrom}, c = 18.296 (4) {angstrom}, {beta} = 93.82 (2){degree}, V = 974 (1) {angstrom}{sup 3}, D{sub c} = 2.07 g cm{sup {minus}3} for Z = 4, and R{sub 1} = 0.0863 (R{sub 2} = 0.0982) for 1436 reflections. The geometry about iodine consists of primary bonds to the three acetate groups (I-O = 2.159 (12), 2.023 (15), 2.168 (12) {angstrom}) and two strong intramolecular secondary bonds (I---O = 2.463 (13), 2.518 (13) {angstrom}) to two of the acetate groups forming a AX{sub 3}Y{sub 2}E{sub 2} pentagonal-planar arrangement. 29 refs., 3 figs., 5 tabs.

Reactions of carboxylic acid anhydrides [(RCO)2O where R = CH3, C2H5, n-C3H7 and CHCl2] with excess of chromium (VI) oxide at low temperatures yield chromyl carboxylates, CrO2(OOCR)2. These compounds are non-conducting in polar organic solvents. IR spectra suggest the presence of both unidentate and bidentate carboxylato groups and discrete Cr = 0 units. The 1H NMR spectra show the presence of only one type of carboxylato group. Reactions of carboxylic acid anhydrides with CrO3 in equimolar ratio yield reduced chromium(III) com pounds o f the type CrO(OOCR) at room temperature. Their millimolar solutions in C6H5NO2, CH3NO2 and CH3CN are non-conducting. IR spectra, magnetic susceptibility and some other properties have been investigated. Both types of compounds are polymeric in nature having covalent structures.

Density, viscosity and specific conductance have been measured at 5° interval between 25 to 50° for imidobis(sulphuryl chloride). The surface tension, freezing point and cryoscopic constant have also been determined. Its IR and proton NMR spectra have been recorded. Relative acidity strength measurements in acetic acid suggest that imidobis(sulphuryl chloride) is a stronger protonic acid than HBr, HSO3Cl and (CF3)2POOH.

Arsenic(III), antimony (III), and bismuth(III) oxides, sodium arsenite and bismuthate react with methanesulfonic anhydride, (CH3)2S2O5, to yield M(SO3CH3)3 (M = As(III), Sb(III), and Bi(III)), Na[AsO(SO3CH3)2], and Na[Bi(SO3CH3)4], respectively, in quantitative yield. Reaction of arsenic(III) oxide with pure methanesulfonic acid yields oxo(methanesulfonato)arsenic(III), AsO(SO3CH3), which behaves as a non-electrolyte in 100% methanesulfonic acid. The compounds have been characterized by elemental analysis, conductance, infrared, 1H nmr and thermal measurements. Their properties have been studied by ligand substitution and complex formation reactions. The M(SO3CH3)3 (M = As(III), Sb(III), and Bi(III)) compounds are capable of functioning both as Lewis acids and bases. These compounds exhibit basic behaviour in 100% methanesulfonic acid. The synthesis of complex mathanesulfonates Cs[M(SO3CH3)4] (M = As(III), Sb(III), and Bi(III)) is also described.

Bases constitute the largest class of electrolytes in imidobis (sulphuryl chloride) because of its highly acidic nature. Alkali metal salts, M N(SO 2 Cl) 2 (where M = Na, K and Rb) behave as ansolvobases whereas solutes containing oxygen, nitrogen or phosphorus donor atoms behave as solvobases. Electrolytes such as CH 3 CO 2 H, CHCl 2 CO 2 H, CF 3 CO 2 H, HCl, CH 3 SO 3 H, p -CH 3 C 6 H 4 SO 3 H and H 2 SO 4 which behave as acids in aqueous solutions behave as solvobases of this solvent. HSO 3 F behaves as ansolvoacid and SnCl 4 and SbCl 5 as solvoacids of this solvent system. Adducts of a few monocarboxylic acids with HN(SO 2 Cl) 2 have been isolated and characterized.

Solvolytic reactions in imidobis(sulphuryl chloride) have been carried out to prepare the ammonium and substituted ammonium salts; Me x NH 4− x Y, where x varies from 0–4 and Y = N(SO 2 Cl) 2 , Et 4 NY and Et 3 NHY. Other solvolysed products prepared are; AlY 3 , R 3 SnY [where R = Me and Ph], TiX 3 Y [where X = Cl and Br], ZrCl 3 Y, SbCl 3 Y 2 , TeBr 3 Y, S 4 N 3 Y and S 3 N 2 ClY. All these compounds have been characterized by elemental analyses, IR spectral studies and molar conductance measurements.

Chromium(III) Chloride, Basic Chromium(III) Formate, IR, Thermogravimetry, Magnetic Moment Chromium(III) chloride reacts with anhydrous formic acid to give basic chromium(III) formate [Cr3O(OOCH)6(H2O)2(HCOOH)](OOCH), HCOOH. Its reactions with bases (B) give compounds of the general composition [Cr30(C00CH)6(B)3](00CH). The title compound has been characterized by infrared spectral data, temperature range (266-110K) magnetic moment and thermogravimetry.