Alan P. Arnold

Synthesis, Structure and Spectroscopic Studies of Mercury(II) Selenolates and MeHgSeBut

Abstract Syntheses of Bu t SeH, Hg(SeR) 2 (R = Me, Et, Bu t , MeSeHgO 2 CMe, and MeHgSeBu t are described. The complexes Hg(SeBu t ) 2 and MeSeHgO 2 CMe have X-ray powder diffraction indicating that thet have identcial polmeric structures to their thiol analogues. Vibrational spectra for the complex Hg(SeBu t ) 2 with tetrahedral coordination for mercury indicate that mercuryue5f8selenium stretching modes occur in the region 130–140 cm −1 , the linear complex MeHgSeBu t has v(Hgue5f8Se) 194 cm −1 (IR) [200 cm −1 (Raman)] and J( 1 H- 199 Hg) 146.8 Hz, and the other complexes have Hgue5f8Se modes below ca. 200 cm −1 .

Chelation Therapy for Methylmercury(II) Poisoning. Synthesis and Determination of Solubility Properties of MeHg(II) Complexes of Thiol and Dithiol Antidotes

Methylmercury(II) complexes of the most widely studied antidotes for mercury poisoning have been prepared, and both the water solubility and 1-octanol/water partition coefficients determined for these complexes and the L-cysteine complex. New complexes of N-acetyl-D,L-penicillamine, 2-mercaptosuccinic acid, meso-dimercaptosuccinic acid, and Unithiol have been synthesized and characterized, and are found to have the formulations MeHgSCMe2CH(NHCOMe)CO2H, MeHgSCH(CO2H)CH2CO2H, MeHgSCH(CO2H)CH(CO2H)SHgMe, and Na[MeHgSCH2CH-(SHgMe)CH2SO3], respectively. Trends in octanol/water partition coefficients are consistent with reported studies of the effectiveness of antidotes for MeHg(II) poisoning and redistribution of MeHg(II) on administration of antidotes, particularly for British anti-Lewisite, Unithiol, and meso-dimercaptosuccinic acid.

Exchange Reactions of Aurothiomalate with 3-Selenopropionate in Aqueous Solution

Abstract Aelenol such as 3-selenopropionate react with aurothiomalate in aqueous solution al pH 8.3 to give Au(3-:lenopropionate)-3 bis complex ejecting thiomalate as a free ligand as observed by 13C nmr spcc-oscopy.

COMPLEXATION OF METHYLMERCURY(II) BY DL-SELENOMETHIONINE

Abstract The complexation of metal ions by methionine [Met] has attracted considerable interest.1–3 However, the coordination chemistry of selenomethionine [Se-Met] has received much less attention despite the fact that it is one of the few naturally occuring selenoaminoacids and a component of at least one bacterial selenoenzyme.4 It has been shown by 1H NMR spectroscopy1 that the prototypical ‘soft’ metal ion, methylmercury(II), binds to Met above pH 7 via the amino group and binds to the thioether group at low pH. A single crystal X-ray diffraction study has confirmed amino coordination in a complex isolated from alkaline solution.5

Organoselenium Chemistry. Synthesis of Selenetan-3-ol,1-Bromo-3-selenocyanatopropan-2-ol and 2-Benzylseleno-Substituted Fumaric and Succinic Acids

Approaches to the synthesis of diselenols have led to isolation of several new organoselenium compounds. Removal of mercury, as HgS, from [1,3-diselenylpropan-2-olato(2–)-Se,Sel]-mercury(II) results in decomposition of the organoselenium fragment to selenetan-3-ol, 1,3-Dibromopropan-2-ol reacts with KSeCN to form 1-bromo-3-selenocyanatopropan-2-ol; the selenoethers 2-(benzyl- se1eno)fumaric acid [(Z)-PhCH2SeC(CO2H)=CHCO2H] and 2-(benzylseleno)succinic acid [PhCH2SeCH(CO2H)CH2CO2H] are formed by base-catalysed reaction of phenylmethaneselenol with acetylenedicarboxylic acid and maleic acid, respectively. The conformations adopted by PhCH2XCH(CO2H)CH2CO2H (X = S, Se) in acetone have been determined by 1H n.m.r. spectroscopy.

Mercury(II) selenolates. Crystal structures of polymeric Hg(SeMe)2 and the tetrameric pyridinates [{HgCl(py)(SeEt)}4] and [{HgCl(py)0.5(SeBut)}4]

The crystal structures of the title compounds have been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to residuals of 0.044, 0.046, 0.058 for 818, 1 678, 2 016 independent ‘observed’ reflections respectively. For all compounds, crystals are monoclinic, space group P21/c. For Hg(SeMe)2, a= 8.440(4), b= 10.732(3), c= 6.681(3)A, β= 96.14(4)°, and Z= 4. For [{HgCl(py)(SeEt)}4](py = pyridine), a= 8.044(5), b= 17.387(14), c= 15.585(21)A, β= 101.75(2)°, and Z= 2. For [{HgCl(py)0.5(SeBut)}4]a= 12.151(5), b= 16.738(7), c= 10.138(6)A, β= 90.93(4)°, and Z= 2. Crystals of Hg(SeMe)2 contain infinite one-dimensional chains along b, the pseudo-tetrahedral mercury atoms being bridged by pairs of selenium atoms; Hg–Se bond distances are in the range 2.614(2)–2.764(2)A. The complexes [{HgCl(py)(SeEt)}4] and [{HgCl(py)0.5(SeBut)}4] were obtained from pyridine solutions containing Hg(SeR)2 and HgCl2, and both contain an eight-membered ring (–Hg–SeR–)4. The former contains two independent pseudo-tetrahedrally co-ordinated mercury atoms, ‘Hg(µ-SeEt)2Cl(py)’; the latter contains two inversion related mercury atoms, ‘Hg(µ-SeBut)2Cl(py)’, and two other inversion related mercury atoms linked by a dichloro-bridge ‘Hg(µ-SeBut)2(µ-Cl)2’. The structure of [{HgCl(py)0.5(SeBut)}4] is very similar to those of [{HgCl(L)0.5(SBut)}4](L = py or 4-methylpyridine) and is isomorphous with the 4-methylpyridine analogue. Mercury–selenium bond distances are slightly shorter than expected by comparison with covalent radii of sulphur and selenium.