William Levason

Recent developments in the chemistry of selenoethers and telluroethers

Abstract The synthesis, properties and structures of complexes of mono-, bi-, poly-dentate and macrocyclic seleno- and telluro-ethers with both d-block and p-block elements reported in the last 10 years are described. Sections also describe the synthesis of new polydentate and macrocyclic ligands, the uses of their complexes, applications of 77Se- and 125Te-NMR spectroscopy, and current theories of bonding between d-block metals and neutral Group 16 donor ligands.

Systematics of palladium(II) and platinum(II) dithioether complexes. The effect of ligand structure upon the structure and spectra of the complexes and upon inversion at coordinated sulphur

Planar complexes cis-[MLX2] (M = Pd, Pt; X = Cl, Br, I) and [ML2(ClO4)2 have been prepared for the dithioethers (L), MeS(CH2)nSMe (n = 2, 3), PhS(CH2)nSPh (n = 2, 3), cis-RSCH=CHSR (R = Me, Ph) and o-C6H4(SR)2 (R = Me, Ph). The ligands PhS(CH2)nSPh (n = 6, 8) yield polymeric [PdLX2]n, whilst PhS(CH2)12SPh produces the trans chelates, trans-[PdLX2] (X = Cl, Br) and trans-[PtLCl2]. The infrared, uv-visible (both solid state and solution) and 1H spectra are reported and discussed. The [ML2](ClO4)2 complexes are 1:2 electrolytes but several show evidence for ion association. The 1H nmr spectra are reported for the complexes of the methyl substituted ligands and the coordination shifts of the methyl and vinyl protons and 3JPtH coupling are discussed. The variable temperature 1H nmr spectra show that rate of inversion at coordinated sulphur lies in the order Pt <Pd and Cl < I. Variation with backbone gives the order -CH2CH2- < o-C6H4 < cis-CHCH- < -CH2CH2CH2-.

The chemistry of copper and silver in their higher oxidation states

A. Introduction B. Copper(III) chemistry. (i) Fluorides and oxides (ii) Group VIB donor Iigands (iii) GroupVBdonorIigands (iv) Groups IIIB and IVB donor hgands (v) Biological role of copper(III) C. Copper chemistry D. Silver(II) chemistry (i) Fluorides and oxides (ii) Group VIB donor Iigands (iii)’ Group VB donor ligands (iv) Groups IIIB and IVB donor ligands E. Silver(II1) chemistry (i) Fluorides and oxides (ii) Group VIB donor ligands (iii) Group VB donor hgands F. Silver(IV) or (V) chemistry G. Gold chemistry, some comparisons Acknowledgements Note added in proof References 46 47 48 50 63 75 78 79 80 80 83 85 95 95 96 100 102 106 107 108 108 109

Coordination chemistry of stibine and bismuthine ligands

Abstract The synthesis of the common monodentate and bidentate stibines and bismuthines, and of multidentates containing one or more antimony or bismuth donor are briefly reviewed. The detailed coordination chemistries of SbH3, trialkyl- and triaryl-stibines and -bismuthines are described, followed by a treatment of distibine complexes and complexes of multidentates containing antimony (and rarely bismuth) in combination with other group 15 or 16 donors. The available X-ray structural data, antimony-121 Mossbauer results, and UV-visible data on these complexes are compiled. Throughout the article comparisons are drawn with complexes of lighter group 15 donor ligands and the considerable differences between stibine ligands and the more familiar phosphines and arsines are highlighted.

Coordination chemistry of higher oxidation states. Part 21. Platinum-195 NMR studies of platinum(II) and platinum(IV) complexes of bi- and multi-dentate phosphorus, arsenic and sulphur ligands

Abstract 195-Platinum NMR spectra are reported for a series of complexes of bidentate ligands [Pt(LL)X4] (X=Cl, Br; LL=diphosphine, diarsine, dithioether, diselenoether), [Pt(Me2PCH2CH2PMe2)2X2]X2, [Pt(o-C6H4(AsMe2)2)2X2]X2, and for the Pt(II) analogues. The trends in chemical shifts δ(Pt) and 1J(PtP), 1J(PtSe) coupling constants are discussed, and used to establish the nature of the solution species obtained by oxidation of Pt(II) complexes of some multidentate phosphorus and arsenic ligands. The [Pt(LL)I4] materials are shown to exist as [PtII(LL)I2] in dimethylsulphoxide solution, but [Pt(o-C6H4(AsMe2)2)2I2]2+ is a genuine Pt(IV) iodo-complex.

The coordination chemistry of periodate and tellurate ligands

Abstract The review describes the coordination chemistry of periodate [IO 6 H 5− n ] n − and tellurate [TeO 6 H 6− n ] n − ligands with both main group and transition metal centres. Relevant chemistry of periodic and telluric acids and their salts are reviewed, followed by discussion of the application of structural (single-crystal X-ray diffraction, PXRD, EXAFS) and spectroscopic (vibrational, UV-visible, multinuclear NMR) techniques to study their complexes. The known complexes of these anions with p-block metals, lanthanides and actinides, and d-block metals are systematically described, and the article concludes with an overview of the field and proposals for further studies.

Germanium(II) dications stabilized by azamacrocycles and crown ethers.

A crown for germanium: Neutral aza- and oxamacrocycles enable stabilization of halide-free germanium(II) dications (see structure, Ge teal, N blue, C gray). The resulting structures show a marked dependence upon the denticity, donor type, and ring size of the macrocycle.

Electrodeposition of metals from supercritical fluids

Electrodeposition is a widely used materials-deposition technology with a number of unique features, in particular, the efficient use of starting materials, conformal, and directed coating. The properties of the solvent medium for electrodeposition are critical to the techniques applicability. Supercritical fluids are unique solvents which give a wide range of advantages for chemistry in general, and materials processing in particular. However, a widely applicable approach to electrodeposition from supercritical fluids has not yet been developed. We present here a method that allows electrodeposition of a range of metals from supercritical carbon dioxide, using acetonitrile as a co-solvent and supercritical difluoromethane. This method is based on a careful selection of reagent and supporting electrolyte. There are no obvious barriers preventing this method being applied to deposit a range of materials from many different supercritical fluids. We present the deposition of 3-nm diameter nanowires in mesoporous silica templates using this methodology.

Coordination stabilised copper(I) flouride. Crystal and molecular structure of fluorotris(triphenylphosphine)copper(I)·ethanol (1/2), Cu(PPh3)3, P·2EtOH

Abstract The structure of the title compound has been determined by single crystal X-ray diffraction. The crystals are orthorhombic a = 13.435 (2), b = 18.812(3), c = 18.739(2) A, Z = 4, space group Pc21n (No 33). A total of 3291 observed reflections were measured and refined to R = 0.087. The copper is inn a distorted tetrahedral environment (P3F) with CuP = 2.325(3), 2.310(3) and 2.316(2), and CuF = 2.062(6) A. The solvent and temperature dependent solution behaviour of this complex has been examined by a combination of 1H, 19F and 31P NMR spectroscopy and conductivity measurements. The synthesis and properties of the unsolvated complex are briefly described.

Tetrakis(triphenylphosphine oxide) complexes of the lanthanide nitrates; synthesis, characterisation and crystal structures of [La(Ph3PO)4(NO3)3]·Me2CO and [Lu(Ph3PO)4(NO3)2]NO3

Abstract The reaction of Ln(NO3)3·6H2O (Ln=La, Ce, Pr or Nd) with a sixfold excess of Ph3PO in acetone formed [Ln(Ph3PO)4(NO3)3]·Me2CO. The crystal structure of the La complex shows a nine-coordinate metal centre with four phosphine oxides, two bidentate and one monodentate nitrate groups, and PXRD studies show the same structure is present in the other three complexes. In CH2Cl2 or Me2CO solutions, 31P NMR studies show that the complexes are essentially completely decomposed into [Ln(Ph3PO)3(NO3)3] and Ph3PO. Similar reactions in ethanol gave [Ln(Ph3PO)3(NO3)3] only. In contrast for Ln=Sm, Eu or Gd, only the [Ln(Ph3PO)3(NO3)3] are formed from either acetone or ethanol solutions. For the later lanthanides Ln=Tb–Lu, acetone solutions of Ln(NO3)3·6H2O and Ph3PO gave [Ln(Ph3PO)3(NO3)3] only, even with a large excess of Ph3PO, but from cold ethanol [Ln(Ph3PO)4(NO3)2]NO3 (Ln=Tb, Ho–Lu) were obtained. The structure of [Lu(Ph3PO)4(NO3)2]NO3 shows an eight-coordinate metal centre with four phosphine oxides and two bidentate nitrate groups. In solution in CH2Cl2 or Me2CO the tetrakis-complexes show varying amounts of decomposition into mixtures of [Ln(Ph3PO)3(NO3)3], [Ln(Ph3PO)4(NO3)2]NO3 and Ph3PO as judged by 31P{1H} NMR spectroscopy. The [Ln(Ph3PO)3(NO3)3] also partially decompose in solution for Ln=Dy–Lu, forming some tetrakis(phosphine oxide) species.