Tim Allman

An investigation of the effect of digital resolution on the COSY two-dimensional NMR experiment by computer simulation

Abstract The COSY experiment produces cross peaks in the two-dimensional NMR spectrum if two spins are coupled, but these cross peaks will vanish as the coupling constant becomes small with respect to the digital resolution. This paper investigates quantitatively the behavior of the cross peaks and diagonal peaks as a function of the coupling constant, J, divided by the digital resolution for an AX spin system in the COSY and related experiments. This is done using a computer simulation program called SIMPLTN, which looks as much like a spectrometer as possible. The spin dynamics is simulated exactly and the output is in the form of a calculated FID, which is then processed like experimental data. In this way, the effects both of the spin parameters and of the data processing can be investigated.

Organobismuth compounds : X. Preparation and vibrational spectra of complexes of diphenylbismuth(III) derivatives

Abstract The cationic complex [Ph 2 Bi(OAsPh 3 ) 2 ] + and the anionic complexes Ph 2 BiX 2 − (X  Cl, Br, CN, SCN and N 3 ) have been prepared and their vibrational spectra have been investigated. The BiO stretching frequency for the cationic complex and the BiPh and BiX stretching frequencies for the anionic complexes have been assigned.

A reinvestigation of the vibrational spectra of mercury (II) halide complexes of triphenylphosphine and tricyclohexylphosphine

Abstract The i.r. (350-130 cm −1 ) and Raman (350 cm − and below) spectra of the 1:1 and 2:1 complexes of mercury (II) halides (chloride, bromide, iodide) with triphenylphosphine and tricyclohexylphosphine have been examined. Spectra for the Ph 3 PHgX 2 and Cy 3 PHgX 2 complexes are consistent with a centrosymmetric dimeric structure of C 2 h skeletal symmetry. Spectra for the (Ph 3 P) 2 HgX 2 and (Cy 3 P) 2 HgX 2 complexes are in accord with a pseudotetrahedral structure of C 2 v symmetry. The Hg-X and Hg-P stretching frequencies for all the complexes have been assigned. The Hg-P stretching frequencies for the 1:1 complexes are higher than those for the 2:1 complexes. In each series of complexes, the Hg-P stretching frequencies decrease in the order Cl > Br > I. For the given mercury (II) halide, the Hg-P stretching frequency is higher for the complex containing less bulky phosphine.

Crystal structure and solid-state31P CP-MAS NMR spectrum of the bis(trifluoroacetato) (triphenylphosphine)mercury(II) dimer [Hg(CF3CO2)2PPh3]2

The title compound belongs to the monoclinic space groupP21/c,a=20.29(1),b=12.644(8),c=18.25(1), Å,β=95.76(5)°. The unit cell contains two dimeric [Hg(CF3CO2)2PPh3]2 molecules in which each Hg atom forms strong primary bonds to a PPh3 molecule and an oxygen of a monodentate trifluoroacetate ligand. These two Hg atoms are bridged by two extra trifluoroacetate ligands, one providing a single oxygen to a Hg-O-Hg bridge, the other including both carboxylate oxygens in a Hg-O-C-O-Hg bridging moiety. This unusual type of bridging makes the two halves of the molecule symmetry independent, leading to distinct signals at 31.5 and 29.9 ppm for the phosphines in the31P CP-MAS NMR spectrum of the solid complex.