Norman A. Bell

Mercury(II)halide complexes of tertiary phosphines. Part VI. The crystal structure of HgCl2(PPh32 and a comparison with related compounds

Abstract Dichlorobis(triphenylphosphine)mercury(II) has been confirmed as having a discrete monomeric structure by a full single-crystal X-ray diffraction study. However, the structure is distorted, with angles about mercury ranging from 134.1(1)° (PHgP) to 98.6(1)° (Clz.sbnd;HgP).The extent of the angular distortion, and the bond length data, have been compare with values for HgI2(PPh3)2 and HgCl2 (PEt3)2, and with initial data obtained in the present work for HgBr2(PPh3)2.It is thus confirmed that: (a) the greater the donor strength of the phosphine (e.g. PEt3), the more the PHg bonding dominates over XHg, with larger PHgP angles and longer HgX bond lengths, and (b) the greater the mercury-halogen interaction (i.e. in iodides), the less significant is the HgP bonding, with smaller PHgP angles and longer HgP bonds.

Mercuric halide complexes of tertiary phosphines. Part I. The crystal structures of 1:1 complexes of triphenylphosphine, tributylphosphine and 1,2,5-triphenylphosphole

Abstract Complete crystal structure analyses have been carried out for 1:1 adducts of mercuric chloride with triphenylphosphine and 1,2,5-triphenylphosphole. In each case the structure consists of discrete centro-symmetric chlorine-bridged dimers, with mercury atoms in distorted tetrahedral environments, but with different HgCl bridge distances. Preliminary single-crystal X-ray photographs indicate that HgX2(PPH3) [X = Br or I] and HgBr2)1,2,5-triphenylphosphole) are isostructural with their chloro analogues. A full X-ray study has shown that the α-form of HgCl2(PBu3) comprises a discrete tetrameric unit, in which two unsymmetric dimers, related by a centre of symmetry, are loosely linked by further HgCl bridges.

Complexes of zinc dialkyldithiocarbamates. Part I. Complexes with bidentate nitrogen ligands; crystal structure of 1, 10-phenanthroline zinc dibutyldithiocarbamate

Abstract Reactions of Zn(S 2 CNR 2 ) 2 (R=Me, Et, Bu, PhCH 2 ) with an excess of 2,2′-bipyridyl, 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline or 3,4,7,8-tetramethyl-1,10-phenanthroline produce crystalline 1:1 complexes which are non-electrolytes. Thermogravimetric studies show that the 2,2′-bipyridyl complexes decompose by loss of ligand whereas the phenanthroline and substituted phenanthroline complexes undergo more complex decomposition. The crystal structure of [(1,10-phenanthroline)Zn(S 2 CNBu 2 ) 2 ] shows the monomeric nature of the complex, octahedral coordination of the metal, approximate planarity of the chelated ZnS 2 C unit and confirms infrared evidence for a degree of π-bonding in the CN bond of the dithiocarbamate moiety.

Complexes of heterocyclic thiones and Group 12 metals: Part four. Preparation and characterisation of 1:1 complexes of mercury(II) halides with 1,3-thiazolidine-2-thione and 1,3-benzothiazoline-2-thione. Crystal structure of the discrete trans dimer [(μ-dibromo)bis(trans{(bromo)(1,3-thiazolidine-2-thione)}mercury(II))]

Abstract The addition of 1,3-thiazolidine-2-thione (tzdSH) or 1,3-benzothiazoline-2-thione (bztzSH) to mercury(II) halides in equimolar quantities in ethanolic solutions resulted in the formation of the 1:1 complexes LHgX2 (L=tzdSH, bztzSH; X=Cl, Br, I) which were characterised by elemental analysis. Spectroscopic evidence confirmed the exocyclic sulphur to be the donor atom in the thione form of the ligand and that the complexes were halogen bridged dimers. The X-ray structure of [(tzdSH)HgBr2]2 shows the molecule to be a centrosymmetric double halogen bridged dimer with distorted tetrahedral coordination geometry for Hg; secondary Hg⋯Br interactions link the molecules together into chains, and there are intramolecular N–H⋯Br hydrogen bonds between the heterocyclic ligands and the bridging bromides.

Complexes of heterocyclic thiones and group twelve metals Part 1. Preparation and characterisation of 1:1 complexes of mercury(II) halides with 1-methylimidazoline-2(3H)-thione: the crystal structure of [(μ2-dibromo) bis(trans{(bromo) (1-methyl-imidazoline-2(3H)-thione)}mercury(II))] at 160 K

Abstract Stoichiometric (1:1) addition of aqueous alcoholic solutions of 1-methylimidazoline-2(3H)-thione (meimz2SH) to a similar series of mercury(II) halides produced crystalline complexes of empirical formula [HgX 2 (meimz2SH)] (X = Cl, Br, l). The chemical formulae of the complexes have been characterised by elemental chemical analysis. IR and 11 C NMR spectra indicated the presence of the thione form of the heterocyclic ligands in the complexes, as well as their thione-sulphur ligating character. The crystal structure of [HgBr 2 (meinz2SH)] 2 ] has been determined by single crystal X-ray diffraction methods. The complex crystallises in a monoclinic unit cell with a = 7.7063(13), b = 14.471(3), c = 25.705(4) A , β = 95.114(9)°, Z = 6 (dimers) and space group P 2 1 / n . The asymmetric unit consists of one general dimeric complex and half of a dimeric molecule on an inversion centre. Weak intermolecular secondary contacts occur between terminal bromine and mercury(II) atoms (Hg⋙Br=3.587−3.791 A). These contacts link the bromo-bridged dimers into weakly associated polymeric sheets, Consequently, the mercury(II) atoms have distorted trigonal-bipyramidal coordination in this complex. The apical sites of the trigonal-bipyramidal polyhedra are occupied by terminal bromine (HgBr terminal = 2.489(2)−2.532(2) A) and terminal thione-sulphur (HgS = 2.405(4) − 2.419(4) A) atoms. Equatorial bromine atoms consist of the long intermolecular bromine contacts and the bridging bromine atoms (HgBr bridging = 2.659(2) − 2.859(3) A). The latter arre also involved in the central, binuclear asymmetric Hg 2 (μ-Br) 2 cores. These cores also contain long Hg⋙Hg′ contacts (3.901 and 4.041 A) and narrow bridgingangles (HgBrHg = 89.90(5)−90.62(5)°). Further intermolecular contacts between the ligand amide (NH) groups and some of the bridging and terminal bromine atoms (NH…Br = 2.555−2.683 A) generate an extensive H-bonded network.

Complexes of heterocyclic thiones and Group 12 metals: Part 3. Preparation and characterisation of 1:2 complexes of mercury(II) halides with 1-methylimidazoline-2(3H)-thione: the crystal structures of [(HgX2)(1-methylimidazoline-2(3H)-thione)2] (X=Cl, Br, I) at 160 K

Abstract The stoichiometric addition (1:2 metal–ligand) of aqueous alcoholic solutions of the metal salts to similar solutions of 1-methyl-imidazoline-2(3 H )-thione (1-meimz2SH) generated crystalline complexes of general formula, [HgX 2 (1-meimz2SH) 2 ] (X=Cl, Br, I), in good yield. The chemical formulae of the complexes have been characterised by elemental chemical analysis. Infrared and 13 C NMR spectra indicated the presence of the thione form of the heterocyclic ligands in the complexes, as well as their thione–sulfur ligating character. X-ray crystal structure analyses have been performed on the three complexes. The metal in the chloro complex occupies a crystallographic two-fold axis which bisects the SHgS angle. The bromo and iodo complexes occupy general positions, but one of the ligands is disordered in the bromo complex. All of the complexes are mononuclear with the four-coordinate metals possessing distorted tetrahedral geometry. The extent of the distortion is indicated by the angles at the metal which range from 93.71(7) to 127.73(7)°. Metal–sulfur distances range from 2.4514(14) to 2.571(3) A. Metal–halogen distances range from 2.5984(13) A (chloro) through 2.641(3) and 2.647(3) A (bromo) to 2.7866(11) and 2.8047(9) A (iodo). Hydrogen bonds, involving the thioamide hydrogen (NH) and halogen atoms are exclusively intramolecular in the chloro complex, but both intramolecular and intermolecular in the bromo and iodo complexes.

Mercury(II) halide complexes of tertiary phosphines. Part III. The crystal structure and vibrational spectra of the discrete dimer β-HgCl2(PBu3), and a comparison with the ‘tetrameric’ α-form ☆

Abstract A discrete dimeric form of the 1:1 adduct of mercury(II) chloride with tributylphosphine, β-HgCl2(PBu3), has been characterised by full single-crystal X-ray diffraction analysis. In contrast to the previously reported α-form, which has been described as ‘tetrameric’, β-HgCl2(PBu3) consist of centrosymmetric halogen-bridged dimers with no indication of any further association; the far-i.r. and Raman spectra may readily be assigned on this basis. The spectra of the α-form are markedly different to those of the β-isomer, yet these too are best interpreted in terms of a dimeric structure, albeit one significantly distorted by weak inter-dimer interactions rather than the ‘tetrameric’ structure previously advocated.

Mercury(II) halide complexes of tertiary phosphines. Part IV. The crystal structure of HgCl2(PCy3) and a re-interpretation of its vibrational spectra

Abstract The previously proposed dimeric structure of HgCl2(PCy3) has been confirmed by full single-crystal X-ray diffraction analysis. However, rather than consisting of asymmetrically halogen-bridged dimeric molecules, the unit cell contains two independent centrosymmetric dimers. Differences between the molecular parameters of the two types of dimer are discussed and their origins considered. The structure determination has shown that the previous assignments of the far-infrared and Raman spectra are erroneous, and correct re-interpretation is given.

Complexes of heterocyclic thiones and Group 12 metals: Part 2: The chemical and electrochemical synthesis of mercury(II) complexes of 1-methylimidazoline-2(3H)-thionate. The crystal structure of trans-[bis-{(η1-S-1-methylimidazoline-2(3H)-thione)(η1-S-1-methylimidazoline-2(3H)-thionate)(μ2-S,N-1-methylimidazoline-2-thionate)mercury(II)}] at 160 K

Abstract Two complexes of mercury(II) and the anion of 1-methylimidazoline-2(3H)-thione (1-meimz2SH) have been prepared and characterised. The addition of an aqueous solution of mercury(II) acetate to an aqueous solution of 1-methylimidazoline-2(3H)-thione and triethylamine produced [Hg(1-meimz2S)2], as a colourless and intractable precipitate. The electrochemical oxidation of elemental mercury, in the presence of a saturated acetonitrile solution of 1-methylimidazoline-2(3H)-thione and a supporting electrolyte, produced two crystalline products, a pale-yellow microcrystalline complex, [Hg(1-meimz2S)2] and a colourless crystalline complex, [Hg(1-meimz2S)2(1-meimz2SH)]. An X-ray crystal structure analysis of [Hg(1-meimz2S)2(1-meimz2SH)] showed that the complex consists of discrete, centrosymmetrically constrained, mercury(II) dimers. Each dimer contains a pair of bifunctional, binuclear bridging, μ2-S,N(η1-S;η1-N), 1-methylimidazoline-2(3H)-thionate anionic ligands (HgSbridging=2.5196(6), HgN=2.325(2) A, NCSexo=126.0(2)°). The bridging ligands adopt a ‘head-to-tail’ configuration. This arrangement generates a central eight-membered ring, Hg2S2C2N2, in the complex. The ring adopts a chair conformation. Distorted, pseudo-tetrahedral four-coordination at each metal is completed by a pair of monodentate, sulfur donating, 1-methyl-imidazoline-2(3H)-thione neutral and anionic ligands (HgSthione=2.5735(7) and HgSthionate=2.4829(7) A). NH ⋯ N hydrogen bonds (N ⋯ N=2.701 A) effectively link the terminal ligands into eight-membered chelates.

Mercury(II) halide complexes of tertiary phosphines. Part X. Study of the triheteroarylphosphine complexes HgX2(PR3)2 [X = Cl, Br, I;R = 2-furyl or 2-thienyl]. Crystal structure of HgCl2[P(2-thienyl)3]2. Solid state vibrational and 31P NMR solution studies

Abstract The preparation of complexes of the type HgX 2 (PR 3 ) 2 [X = Cl, Br or I; R = 2-furyl or 2-thienyl] has been investigated, and a series of compounds has been characterised by analytical and, where possible, solid state vibrational and 31 P NMR solution studies. In addition, the X-ray crystal structure of HgCl 2 [P(2-thienyl) 3 ] 2 has been determined. Crystals of the complex are monoclinic, space group P 2 1 / n , with a = 9.556(6), b = 18.280(10), c = 16.609(9) A, β = 102.14(5)°. The structure was solved using the heavy atom method and refined to a final R -value of 0.049 for 4067 observed diffractometer data. The complex is found to be a distorted tetrahedral monomer, and the geometry about mercury has been compared with that found in HgCl 2 (PR 3 ) 2 (R = Et or Ph). These data, and in particular, the relative values of the PHgP angle, indicate the σ-donating ability of tri(2-thienyl)phosphine to be substantially weaker than that of triethylphosphine. Comparison of 1 J ( 199 Hg 31 P) coupling constants indicates that both triheteroarylphosphines are weaker σ-donors towards mercury(II) halides than is triphenylphosphine, a view given support by the crystallographic data, and also by the solid state vibrational data for certain of the complexes.