G.W. Smith

Development of new technetium cores containing technetium—nitrogen multiple bonds. Synthesis and characterization of some diazenido-, hydrazido- and imido- complexes of technetium

Abstract The syntheses of several novel diazenido-, hydrazido- and imido- complexes of technetium are described. These precursors which contain technetium—nitrogen multiple bonds are derived directly from the appropriate organohydrazine or amine in good yield. Some of the chemistry has been extended to the metastable isotope 99mTc (γ, t 1 2 = 6 h) in highly dilute aqueous media to give single species in high radiochemical purity. These preparations are applicable to the synthesis of new technetium radiopharmaceuticals and should provide for the development of a whole new range of technetium-based diagnostic agents in nuclear medicine.

Synthesis and X-ray crystal structure of a mercury(II)-telluroamine complex. Monodentate behaviour by a potentially bidentate hybrid telluride ligand, 1-(NMe2)-2-(TeC6H4-4-OEt)-4-MeC6H3

Abstract The telluroamines 1-(NMe2)-2-(TeAr)-4-MeC6H3 (1) (Ar = 4-MeOC6H4 or 4-EtOC6H4) react with mercury(II) halides forming adducts of composition HgX2 · 1 (X = Cl or Br). The IR, far-IR (up to 50 cm−1), 1H and 13C NMR spectra of the mercury(II) complexes indicate that the ligands (1) behave as monodentate donors, coordinating through tellurium only. The complexes seem to be dimers of the composition [1 · XHg(μ-X)2HgX · 1]. The crystal structure of the adduct obtained from mercury(II) bromide has been determined. It reveals that the NMe2 group does not coordinate with mercury(II) and the complex is a dimer in which two somewhat asymmetrical bromine bridges are present between the mercury atoms. The coordination environment of each mercury is almost tetrahedral [91.25(3)–118.40(4)°]. The HgBr bridging bond lengths are 2.755(1) and 2.710(1) A.

Improved synthetic routes to tris(acetylacetonato)ruthenium(III) and a redetermination of the structure of the β-polymorph

Abstract The ruthenium-blue cluster-mediated synthesis of Ru(dike)3 complexes (dike = β-diketone) has been investigated in view of the low yields this route usually produces. Only the acetylacetonato complex of the metal was isolated without modifications to the procedure, allowing a redetermination of the crystal structure to be carried out; previously published data relating to the structure of the racemic complex is incorrect and is now superseded by a more accurate determination. Two forms of this complex have now been isolated, and a comparative analysis of these is presented here.

X-ray crystal and molecular structure of dichlorobis [2(1H)-pyridinethione-S]iron(II)

Attempts to prepare the mixed ligand complex, FeCl2(pyS)(Ph3P)2 from the reaction of iron(III) chloride with 2(1H)-pyridinethione-S(HpyS) and triphenylphosphine(Ph3P) in ethanol instead formed FeCl2(HPyS)2 characterized by X-ray crystallography. The structure was determined by the heavy atom method, using MoKα diffractometer data, and refined by full-matrix least squares toR=0.049 for 1123 observed reflections. The molecule possesses twofold symmetry with a distorted tetrahedral geometry about the iron(II) center with S-Fe-S and Cl-Fe-Cl bond angles of 98.76(5)° and 115.79(5)° and Fe-S and Fe-Cl bond distances 2.345(1) Å and 2.288(1) Å, respectively. Hydrogen bonding between NH and chlorine atoms leads to a polymeric type structure of linked molecules running approximately parallel to thea axis.

X-ray crystallography and NMR spectroscopy of some cyclohexyl esters

Abstract The X-ray structures and proton and carbon-13 NMR spectra have been obtained for two dicyclohexyl esters and one tricyclohexyl ester: namely, di-2-methylcyclohexylsuccinate (D2MCS), dicyclohexyl-3,4-furandicarboxylate (DCFDC) and tricyclohexyl-1,2,3-propanetricarboxylate (TCPTC). These esters are models for high-traction fluids. It was shown that the molecular modelling calculations we performed (on DCFDC and TCPTC) are not adequate for determining the minimum energy configuration of the compounds investigated.

The structure of tricyclohexylmethane

Abstract Tricyclohexylmethane has a melting point close to ambient temperature. Nevertheless the X-ray structure has been determined. The crystal is chiral but its chirality could not be established. The solid is unusual in that the atomic volume per carbon atom is 22.2 A3 which is substantially greater than is usual for a hydrocarbon. Since there is little data in the literature on the compound we have reported the solution-state proton and proton-decoupled NMR spectra.

New structural types for chromium(II)

The new compound Cr(thiourea)2(NCS)2 contains trans-planar units stacked along the a-axis of the unit cell so that the chromium ions lie in infinite chains. In this first example of chains of directly interacting paramagnetic metal ions, the CrCr separation is 3.97 A which leads to weak antiferromagnetism but does not provide a conducting pathway. In contrast, the molecules in Cr(OPD)2(NCS)2, where OPD is o-phenylenediamine, prepared during investigations aimed at producing planar Cr2+ complexes by template reactions, do not stack and contain thiocyanate bridges. The new complexes Cr(OPD)Cl2 and [Cr(OPD)6]Cl2 have been prepared. The latter has been used in reactions with acetylacetone aimed at producing planar chromium(II)-tetra-azamacrocyclic complexes, but a new metal-free octa-azamacrocycle has been obtained.

Structures of NN'-ethylenebis(monothioacetylacetone-iminato) nitrosylcobalt and NN'-ethylenebis(2-hydroxyacetophenoneiminato) nitrosylcobalt

The cobalt atoms in both [Co(NO)(sacacen)] and [Co(NO)(7-Mesalen)] {sacacenH2 isNN′-ethylenebis(monothioacetylacetoneimine) and 7-MesalenH2 isNN′-ethylenebis(2-hydroxyacetophenoneimine)} are 5-coordinate, with a tetragonal-pyramidal arrangement of donor atoms. The cobalt atom in [Co(NO)(sacacen)] lies just above the plane defined by the SNNS donor atoms of the quadridentate ligand, and the nitrosyl group occupies the apical position. A similar geometry is defined by the ONNO donor atoms and the NO group in [Co(NO)(7-Mesalen)]. The Co-N-O angles are strongly bent, as predicted from15N-nmr studies (127.2(6)°[Co(NO)(sacacen)] and 127.4(3)°[Co(NO)(7-Mesalen)]). Both nitrosyls crystallize in the monoclinic system. For [Co(NO)(sacacen)],a=8.501,b=12.673,c=13.866 Å,β=95.00°,Z=4 and space groupP21/c. The structure was determined by the heavy-atom method, usingMo Kα diffractometer data, and refined by full matrix least squares toR=0.062 for 2920 observed reflections. For [Co(NO)(7-Mesalen)],a=9.461,b=13.053,c=13.456,β=99.32°,Z=4 and space groupP21/c. The structure was determined as above toR=0.040 for 2461 observed reflections.

X-Ray crystal and molecular structure of phenyl(triphenylphosphine)-mercury(II) nitrate

Reaction of phenylmercury(II) nitrate with triphenylphosphine in dry ethanol gives the adduct [HgPh(PPh3)]NO3 whose structure has been determined by X-ray crystallography. The complex crystallizes in the monoclinic space group P21/n with unit-cell parameters a= 13.119(5), b= 10.529(2), c= 16.233(4)A, and β= 102.79(1)°. The geometry about mercury(II) is nearly T-shaped with P–Hg–C(Ph) 167.5(2)°. The Hg–P distance of 2.431(2)A indicates strong interaction and there is weak interaction between mercury and the nitrate oxygen atoms. This complex represents the first structurally characterized organomercury(II) complex with a tertiary phosphine.

X-ray structure of tricyclohexylmethyl chloride

The X-ray crystallographic structure of tricyclohexylmethyl chloride, a precursor of the tricyclohexylmethyl radical, has been determined. Colourless tablets of C19H33Cl crystallized from hexane/chloroform in the orthorhombic space group Pnma, with cell dimensions a=10.725(3),b=15.670(3),c=10.168(3) Å;V=1708.8(1.3) Å3;Z=4. 1586 reflections withI>3 σ(I), and 302 with zero intensity, on refinement gaveR=0.046,Rw=0.076. The three cyclohexyl rings are arranged to give the molecule a plane of symmetry containing the central C−H axis. The large volume per nonhydrogen atom, of about 21.3 Å3, is close to values found in the crystal structures of analogous tricyclohexyl compounds.