Maxwell J. O'Connor

Tellurium-125 NMR and mass spectra of dithiotellurides

Abstract The preparation, 125 Te NMR and mass spectra of some dithiotellurides, Te(RS) 2 (R = Ph, 2-PhCOOH, CPh 3 , CH 2 Ph, 3-PrCOOH, n-Bu, i-Pr, t-Bu) are discussed. The 125 Te chemical shifts have been found to lie within a range spanning ca . 690 ppm and correlate with the p K a values of the parent thiols. The mass spectra of the alkyl derivatives (R = n-Bu, i-Pr, t-Bu) indicate an initial step-wise loss of alkenyl groups followed by the elimination of hydrogen sulfide from the resultant bis(hydrosulfido)-tellurium ion.

Applications of molybdenum-95 NMR spectroscopy. 14. Construction of a transverse probe for the detection of broad 95Mo resonances in solution. Studies on Binuclear Mo(II) compounds

The use of a specifically constructed probe having a transverse solenoid coil operating at 13 MHz has permitted convenient detection of 95Mo resonances in solutions of [Mo] = 5 × 103 M for compounds whose linewidths, W12, are in excess of 1000 Hz. Application of a three-pulse sequence, 90°+x (acq)+-180°x-τ-90°−x (acq)+ and shielding of the coil with lead substantially reduces ring-down times. A series of binuclear molybdenum(II) species which feature formal Mo-Mo quadruple bonds were examined. 95Mo resonances were detected in the range 3227–4148 ppm and this is the most deshielded class of molybdenum compounds so far discovered. Observed linewidths covered the range 200–1500 Hz. Those for the compounds [MO2(O2CR)4] could be rationalized on the basis of quadrupolar relaxation and the Hu-Zwanzig model of molecular motion.

Applications of 95Mo NMR spectroscopy. XIII. Relaxation times of molybdenum compounds

Abstract The 95 Mo spin-lattice and spin-spin relaxation times have been measured for a number of compounds with linewidths ranging from less than 1 to 1720 Hz. Corresponding relaxation times range from 7 s to 180 μs. The results indicate that quadrupole relaxation is the only significant mechanism involved, allowing the T 1 values to be interpreted in terms of the electric field gradient, molecular size and shape, solution viscosity, temperature, and solvent-solute interactions. 97 Mo relaxation times are also reported for the more highly symmetric compounds.

Applications of 95Mo NMR Spectroscopy. X1. 95Mo 97Mo, and 17O relaxation times, quadrupole coupling constants, and the molybdenum relaxation mechanism in Mo(CO)6

Abstract Spin-lattice relaxation times ( T 1 s) of 95 Mo 97 Mo, 17 O, and 13 C for Mo(CO) 6 in CDCl 3 are reported. The rotational correlation time of the molecule is obtained from the chemical-shift anisotropy relaxation of 13 C. Quadrupole coupling constants are calculated for 95 Mo 97 Mo, and 17 O. The results indicate that 95 Mo and 97 Mo, relaxation is entirely quadrupolar and is caused by rotational reorientation of a permanent quadrupole coupling constant rather than from solvent molecule collisions and vibrationally induced momentary electric field gradients.

Molybdenum-95 nuclear magnetic resonance. Applications to substituted carbonyls

Molybdenum-95 NMR spectra of a variety of substituted molybdenum carbonyl species are reported. The large chemical shift range permits easy resolution of substituent effects, both within similar ligands and in the number of carbonyls replaced. Molybdenum-95—phosphorus-31 spin—phosphorus-31 spin—spin coupling is observed by this technique for the first time. The results are discussed in terms of general applications of the technique to molybdenum organometallic chemistry.

Synthesis and characterization of alkyl- and aryltin(IV) monothiocarbamates

Abstract The preparation of dialkyl- and diaryltin(IV) N,N′-dialkylmonothiocarbamates from the alkylammonium salt of the ligand and the appropriate diorganotin(IV) chlorides is described. The compounds R2Sn(R′2mtc)2 and Ph3Sn(R′2 mtc) (R = alkyl, aryl; R′2 = Me, Et; mtc = monothiocarbamate anion) are monomeric in dichloromethane or chloroform and are non-electrolytes in nitromethane. 1H spectra of CDCl3 CD2Cl2 and benzene solutions of R2Sn(R′2mtc)2 indicate that the dialkyltin(IV) moiety is non-linear (J119Sn-1HCH3 ca. 80 Hz) and that the N-alkyl substituents in the monothiocarbamate ligand are magnetically non-equivalent. Stereochemical non-rigidity of Me2Sn(Me2mtc)2 in CD2Cl2 is observed in the 1H nmr spectrum. Two isomeric species are observed with coalescence occurring at −30° to give a single species that shows restricted rotation of the N-methyl substituents. Further coalescence of these two equal intensity N-methyl signals occurs at 55 °C. A value of J119Sn--CH3(1J = 552 Hz) for the carbon bonded directly to tin in Et2Sn(Me2mtc)2 suggests that this type of compound involves six-coordination of the tin atom with SnS bonding being stronger than Sn-O bonding. The Ph3Sn(R′2mtc) species have distorted trigonal bipyramidal geometry with the oxygen of the bidentate monothiocarbamate in one of the axial positions.

Monothiocarbamate complexes of rhodium(I)

Abstract The preparation of some dicarbonyl(N-substituted-monothiocarbamato)rhodium(I) complexes is described. The red crystalline compounds are dimeric in chloroform solution and their infrared spectra in the terminal carbonyl region consist of three bands. These observations suggest that the structure of the compounds is similar to that of [Rh(co) 2 Cl] 2 with the sulphur atoms of the monothiocarbamate ligands bridging the two rhodium(I) ions in the dimer. The reaction of the dimeric species with excess ligand and triphenyl-phosphine is also described. The monothiocarbamate acts as a monodentate ligand bonded through the sulphur atom only, in the products formed in these reactions.

Crystal and molecular structure of tris(2-aminocyclopentene-1-dithiocarboxylato)-cobalt (III) monoacetone

The title compound crystallizes in the monoclinic space groupP21/c withZ=4 and cell dimensionsa=7.724(1),b=19.274(5),c=18.638(4) Å, and β=105.68(2) °. Refinement with 1126 terms, measured with MoKα radiation on a diffractometer, has yielded a conventionalR factor of 0.059. The non-hydrogen atoms in the complex molecule were refined with anisotropic temperature factors whereas those in the acetone molecule were refined isotropically. The nitrogen atoms in the complex are not coordinated; the coordination sphere involves Co—S6 bonding of approximateD3 symmetry, the average Co—S bond length being 2.275 Å. The geometry of the coordination sphere with respect to a definedC3 reference axis is similar to that found in several tris(N,N′-disubstituted-dithiocarbamato)cobalt(III) complexes. The acetone molecule is hydrogen bonded to one of the amino groups, the O ⋯ N distance being 2.99 Å.

The preparation and characterisation of tris(pyrrole-N-carbodithioato)-cobalt(III) hemikisdichloromethane. Crystal and molecular structure and solution properties

Abstract The title compound was obtained as monoclinic crystals belonging to the space group P21/c with a = 11.252(3), b = 18.062(2), c = 10.980(2) A, β = 111.30(2)° and Z = 4. Refinement with diffractometer data measured with CuKα radiation converged to give a conventional R index of 0.070. The CoS6 coordination geometry is distorted octahedral; some of the important bond lengths are CoS, 2.267(3); S---S, 2.801(5); CS, 1.675(9); (sulfur bonded) CN, 1.388(11) A. The average ligand bite angle is 76.3°, and the compound is isostructural with the Fe analogue. The green cobalt(III) complex is diamagnetic in the solid state and in solution in non-coordinating solvents. The solution visible absorption spectrum is typical of other tris(N,N′-disubstituted dithiocarbamoto)cobalt(III) complexes having effective D3 symmetry.

Mercury—mercury spin—spin coupling in an organomercury compound

The 199Hg NMR spectrum of 2-methoxy-1-nitro-3,5-bis(trifluoroacetatomercurio)benzene, prepared by mercuration of 1-methoxy-2-nitrobenzene with mercuric trifluoroacetate in trifluoroacetic acid, shows an AB system attributable to 199Hg199Hg coupling with 4J(199Hg199Hg) 2163 Hz.