The First Example of a Structurally Characterized Monomeric Bismuth Selenolate

The reaction of intramolecularly coordinating 2-(4,4-dimethyloxazolino)phenyl selenolate ligand with anhydrous BiCl3 (3:1 equivalents) produces the monomeric, air stable, homoleptic bismuth(III) selenolate complex.

Synthesis and Structural Characterization of Monomeric Selenolato Complexes of Zinc, Cadmium, and Mercury

The synthesis and characterization of homoleptic zinc(II), cadmium(II), and mercury(II) selenolates incorporating the intramolecularly chelating oxazoline ligand are described. The derivatives, M[Se(Ox)](2) [M = Zn (1), Cd (2), Hg (3); Ox = 2-(4,4-dimethyl-2-oxazolinyl)benzene], were prepared in good yield via the metathesis reactions of MCl(2) with a lithium areneselenolate, OxSe(-)Li(+). The mercury complex 3 was also synthesized by treating the corresponding diselenide with elemental mercury. The complexes are quite stable and highly soluble in common nonpolar organic solvents. X-ray diffraction results show that the complexes are monomeric in the solid state. The geometry around the metal ion in all complexes is found to be distorted tetrahedral. The crystal structure of Zn[Se(Ox)](2) (1) shows that the complex is "helically" chiral and enantiomerically pure. The spontaneous splitting of the racemates indicates the solubility differences between the racemates and pure enantiomers. (1)H, (13)C, and (77)Se NMR measurements indicate that complex 1 retains its "helical" structure in solution. Crystal data (Mo Kalpha; 293(2) K) are as follows: 1, monoclinic space group P2(1), a = 9.3900(12) Å, b = 11.618(2) Å, c = 10.8822(14) Å, beta = 98.245(8) degrees, Z = 2; 2, orthorhombic space group Pbca, a = 12.777(6) Å, b = 17.841(10) Å, c = 21.010(8) Å, Z = 8; 3, monoclinic space group P2(1)/c, a = 9.087(2) Å, b = 11.889(2) Å, c = 22.456(4) Å, beta = 98.780(13) degrees, Z = 4.

Carbon Dioxide Laser Saturation Spectroscopy and the Hyperfine Structure of Monosubstituted Ozone 16O16O17O and 16O17O16O

Carbon dioxide lasers have been used in an offset-lock configuration to obtain saturation spectra of ozone, monosubstituted with O-17, at a linewidth of a few kHz. Rich hyperfine structures result from the O-17 nucleus, spin 5/2. These are used, together with earlier microwave data, to obtain the corresponding hyperfine parameters. The spectra also illustrate the sensitivity of hyperfine structures to subtle vibration-rotation interactions. Copyright 1998 Academic Press.

Dipyridamole thallium imaging: use in preoperative cardiac risk assessment in vascular surgical patients

BACKGROUND

The objective of this study was to determine whether routine performance of dipyridamole thallium imaging adds to the power of a careful clinical evaluation in the risk stratification of patients undergoing major vascular surgery.

METHODS

In this retrospective study, 115 cases evaluated by dipyridamole thallium imaging before major vascular surgery were reviewed. Patients were assigned to a high-risk cohort if they had a history of congestive heart failure or evidence of previous myocardial infarction.

RESULTS

Six (8%) patients from the high-risk cohort developed major cardiovascular complications. Reversible perfusion defects, present in 67% of the high-risk patients, did not predict complications. None of the patients in the low-risk cohort developed complications despite the presence of reversible perfusion defects in 33%. Patients in the high-risk cohort who underwent cardiac catheterization and selective coronary bypass grafting were uniformly free of perioperative complications. The extent and severity of fixed or reversible thallium perfusion did not predict the occurrence of cardiovascular complications. However, three patients were denied surgery following an unacceptable cardiovascular risk assessment based on clinical findings and multiple reversible thallium perfusion defects.

CONCLUSION

In low-risk patients, screening with dipyridamole thallium can identify patients with redistribution defects whose risk of perioperative ischemic events can be reduced by intensifying perioperative anti-ischemic management. If the patient is in the high-clinical-risk subgroup, screening with dipyridamole thallium does not identify a cohort with negligible perioperative risk; thus, further evaluation of these patients by cardiac catheterization should be considered.

The Crystal and Molecular Structure of Bis-[μ-2-(p-nitrophenyliminomethyl)phenolato-N,O]-bis(ethanol)bis(nitrato-O,O')dinickel(II), [Ni(slno)NO3(C2H5OH)]2, a Binuclear Ferromagnetic Salicylaldimine Derivative of Nickel Nitrate

The crystal and molecular structure of the complex bis-[μ-2-(p-nitrophenyliminomethyl)phenolato- N,O]-bis(ethanol)bis(nitrato-O,O')dinickel(11) and its magnetic properties are reported. Crystal data: space group PI, Z 1, a 8.882(2), b 9.332(3), c 12.533(4) �, α 94.40(2),B 109.99(2), γ 111.61(2)�, U 883 �3, R 2.8%, Rw 3.3% for 2154 reflections. The compound is prepared from the reaction of bis(N-p-nitrophenylsalicylaldimine)nickel(II) with nickel nitrate in hot triethoxymethane, and on cooling the solution deposited pale green transparent crystals. The structure contains neutral dimeric units with bridging through the phenolic oxygen atoms and has distorted octahedral geometry about each crystallographically identical nickel atom. The six donor atoms are made up of two oxygen atoms from the bidentate nitrate, oxygen from ethanol, nitrogen from the imine group and two bridging phenolic oxygen atoms. The Ni2O2 group is strictly planar possessing a crystallographic centre of symmetry. The angles subtended at the bridging oxygen atoms indicate a tetrahedral geometry and it is demonstrated that this is important in explaining the ferromagnetic intradimer interaction. The presence of hydrogen bonding between the ethanol hydrogen and the nitrate group of an adjacent molecule appears to be an important stabilizing factor in determining the structure and provides a possible pathway for the antiferromagnetic interdimer exchange interaction.