Gerald R. Willey

Lanthanide(III)chloride-tetrahydrofuran solvates: structural patterns within the series LnCl3(THF)n, where n = 2,3,3.5 and 4: crystal and molecular structures of [PrCl(μ-Cl)2(THF)2]n, [Nd(μ-Cl)3(H2O)(THF)]n and GdCl3(THF)4

Abstract Praseodymium(III), neodymium(III) and gadolinium(III) chloride adducts with tetrahydrofuran (THF) have been prepared and structurally characterized by X-ray crystallography. Removal of water from the corresponding hexahydrate LnCl3(H2O)6 using thionyl chloride in the presence of excess THF provides light-green cubic crystals of [PrCl3(THF)2]n (1), blue block crystals of [NdCl3(H2O)(THF)]n (2) and colourless needle crystals of GdCl3(THF)4 (3). In 1 each praseodymium atom is seven-coordinate and is linked to (two) adjacent metal centres by double (μ-Cl)2 halogen bridging units, resulting in a polymeric chain structure. The metal geometry approximates to distorted pentagonal bipyramidal with PrClbridge 2.852(6)–2.891(5), PrClterminal 2.668(6), PrOTHF 2.51(1) (axial), 2.53(2) A (equatorial). In 2 the structure is a two-dimensional cross-linked polymer in which each neodymium atom is connected to (three) others via double (μ-Cl)2 halogen bridge bonds. he coordination sphere of each metal centre comprises six chlorine atoms [NdClbridge 2.816(3)–2.938(3) A] and two oxygen atoms belonging to a THF molecule [NdO, 2.548(6) A] and a water molecule [NdO, 2.490(7) A], respectively. Hydrogen bonding interactions involving halogen atoms and coordinated water molecules from adjacent metal units (intermolecular) are observed, OH3·Cl 3.147–3.350 A. In 3 the molecular structure is based on a seven-coordinate pentagonal bipyramidal metal geometry in which two chlorides occupy the axial positions with the other chloride and the four solvate (THF) molecules making up the equatorial plane. GdCl 2.60(2)–2.66(2), GdO 2.40(2)–2.52(3) A. In addition, general comments concerning structural relationships within the series LnCl3(THF)n, where n = 2, 3, 3.5 and 4, are discussed.

STRUCTURAL CHEMISTRY OF SC(III) : AN OVERVIEW

Abstract Structural aspects of the chemistry of organometallic/coordination compounds of scandium(III) are reviewed. Individual compounds are classified and discussed in terms of coordination number and associated metal geometry through the range CN=3–9. The present review provides an exhaustive literature coverage 1926–1998 (April).

Ge(IV)–citrate complex formation: synthesis and structural characterisation of GeCl4(bipy) and GeCl(bipy)(Hcit) (bipy=2,2′-bipyridine, H4cit=citric acid)

Abstract The adduct [GeCl4(bipy)] (I), obtained by direct treatment of the parent halide with 2,2′-bipyridine (bipy), reacts with citric acid (H4cit) in acetonitrile solution to provide the chelate derivative [GeCl(bipy)(Hcit)] (II). The structures of compounds I and II have been determined by single crystal X-ray diffraction. For I the central germanium shows octahedral geometry with two mutually cis-chlorine atoms, GeCl (mean) 2.244(1) A, and the bidentate ligand, GeN (mean) 2.065(4) A occupying equatorial positions and two mutually trans-chlorine atoms, GeCl (mean) 2.267(1) A in axial locations. For II the citrate ligand is terdentate and bound to the central germanium via its hydroxyl, α-carboxylate and one of the β-carboxylate groups in a fac-octahedral arrangement. GeOhydroxyl 1.800(3) A, GeOcarboxylate (mean) 1.904(3) A, GeCl 2.209(1) A, GeN (mean) 2.012(3) A. The uncoordinated β-carboxylate group remains intact as a ‘dangling arm’. The structure also contains poorly defined and disordered acetonitrile (solvent) molecules trapped in the lattice.

Crown ether complexes of BiIII. Synthesis and crystal and molecular structures of BiCl3·12-crown-4 and 2BiCl3·18-crown-6

Crown ether complexes of bismuth(III) chloride of the types BiCl3·12-crown-4 (1), 2BiCl3·18-crown-6 (2), and BiCl3·15-crown-5 (3) have been prepared; compound (1), and probably compound (3), is a neutral adduct with the pyramidal BiCl3 linked to all four (five) oxygen atoms of the crown in a half-sandwich structure while compound (2) has the ionic formulation 2[BiCl2·18-crown-6]+[Bi2Cl8]2–, in which the bismuth cation is eight-co-ordinate involving all six oxygen atoms of the crown and two chlorine atoms in bicapped trigonal prismatic geometry.

Crown thioether complexes of p-block elements: crystal and molecular structures of SbCl3·9s3 (9s3 = 1,4,7-trithiacyclononane) and 2SbCl3·18S6 (18S6 = 1,4,7,10,13,16-hexathiacyclooctadecane)

The first crown thioether complexes of SbIII and BiIII, as representative p-block elements, have been isolated, viz SbCl3·9S31, BiCl3·9S3·0.5 MeCN, SbCl3·15S5, 2SbCl3·18S6 2 and BiCl3·18S6; X-ray crystal structure determinations of 1 and 2 establish full participation of ligand S-donor sites in metal ⋯ sulphur bonding in each case.

Synthesis and structure of antimony(III)chloride-1,4,7,10,13,16-hexaoxocyclooctadecane-(18-crown-6)-acetonitrile (1/1/1)

Abstract The adduct SbCl 3 ·18-crown-6·MeCN has been synthesised and its structure determined by single crystal X-ray diffraction techniques. [Sb(C 12 H 24 O 6 )Cl 3 ·CH 3 CN], M r = 533.6, orthorhombic, Pnma , a = 19.473(6), b = 13.946(5), c = 8.032(3) A, U = 2181.1(1.1) A 3 , Z = 4, D c = 1.625 g cm −3 , λ(Mo Kα) = 0.71073 A,μ(Mo Kα) = 16.7 cm −1 , T = 293 K, F (000) = 1072, R = 0.0503 for 1383 unique observed reflections with I /σ( I )⩾2.0. In this molecular complex the crown ether possesses approximate D 3 d symmetry and is bonded by all six oxygen atoms to a pyramidal SbCl 3 unit resulting in a half-sandwich structure. The solvent (MeCN) molecule is trapped in the lattice and plays no part in the coordination geometry of the central Sb atom.

Halide abstraction reactions of Sb(V) chloride: synthesis and characterisation of hexachloroantimonate salts of M(II) M= Zn, Mg; M(III) M= Cr; and M(IV) M= Ti, Sn and related Cp2M(IV) M= Ti, Zr and Hf

Abstract Reactions of SbCl5 with various covalent metal halides in MeCN have been studied as a convenient and direct route to metal hexachloroantimonate salts via Sb(V) halide abstraction. The isolation and characterization (Ir, Vis-UV, 1H NMR spectroscopic and microanalytical) of the complexes [Zn(MeCN)6][SbCl6]2, [CrCl2(MeCN)4][SbCl6], [SnCl3(MeCN)3][SbCl6], [TiCl2(MeCN)4][SbCl6]2, [Cp2M(Cl)(MeCN)x][SbCl6] M = ti, x = 1; M = Zr, Hf, x = 2, and [Cp2M(MeCN)y][SbCl6]2 M = Ti, y = 2; M = Zr, Hf, y = 3, is described. The reaction of MgCl2 with SbCl5 was carried out in EtOAC as solvent and gave [Mg(EtOAc)6][SbCl6]2. 121Sb NMR, IR and UV spectroscopic measurements provide positive identification of the SbCl6− anion.

Co-ordination studies of cyclic polythioethers: Complexes of Au(III), Nb(V), Sb(V), Sn(IV), Ta(V) and Ti(IV) halides with 1,4-dithiane and 1,3,5-trithiane

Abstract Reactions of the S -donor ligands 1,4-dithiane (DT) and 1,3,5-trithiane (TT) with a series of covalent metal halides have been studied. We report the preparation and characterisation of the 1:1 complexes AuCl 3 ·(TT), MCl 5 ·(TT) (M = Sb, Ta), TiCl 4 ·(TT), MX 4 ·(DT) (M = Sn, X = Cl, Br), MCl 5 ·(DT) (M = Nb, Ta), the 1:2 complexes MX 4 ·2(TT) (M = Ti, Sn, X = Cl; M = Sn, X = Br) and the 2:1 complexes 2MCl 5 ·(DT) (M = Nb, Ta). Structural assignments in terms of metal geometry and coordination number and of ligand binding as either monodentate or bidentate bridging between separate metal atoms are based on infrared data. Variable temperature 1 H NMR measurements of SnCl 4 ·2(TT) indicate fluxional rearrangements of the six-membered sulphur-containing rings.

Adducts of indium(III) bromide: synthesis and structural characterisation of [InBr3(THF)2], [InBr3(DMF)3], [InBr3(Me3[9]aneN3)] and [InBr3({–N(Me)–CH2–}3)]

Abstract Treatment of InBr3 with THF gives InBr3(THF)2. A crystal structure determination (X-ray diffraction) reveals that the five co-ordinate metal centre adopts a trigonal bipyramidal geometry with the three halogen atoms in the equatorial plane and the two THF ligands in axial positions. Cremer–Pople ring puckering analysis reveals one THF ligand in a twist conformation and the other in an envelope arrangement in each molecule. The reaction of InBr3 with DMF in hexane gives InBr3(DMF)3 identified (spectroscopic and X-ray diffraction) as the six co-ordinate fac-octahedral isomer. Treatment (1:1 in acetonitrile) of InBr3 with 1,4,7-trimethyl-1,4,7-triazacyclononane gives InBr3(Me3[9]aneN3) in which the anticipated facial co-ordination of the terdentate ligand results in a distorted octahedral geometry at the metal centre as confirmed by X-ray diffraction. Similar treatment of InBr3 with 1,3,5-trimethyl-1,3,5-triazacyclohexane gives InBr3({–N(Me)–CH2–}3) as verified by spectroscopic analyses and an X-ray diffraction study.

Synthesis and chemical properties of dicyclopentadienylzirconium bis(diphenylarsenide) and bis(diphenylantimonide), [(η-C5H5)2Zr(EPh2)2] (E = As OR Sb)

Abstract Treatment of Cp 2 ZrCl 2 (Cp = η-C 5 H 5 ) with LiEPh 2 (E = As or Sb) affords the corresponding pentelide complexes Cp 2 Zr(EPh 2 ) 2 . In the particular case of the Cp 2 TiCl 2 /LiAsPh 2 system there is evidence for reduction to Cp 2 TiAsPh 2 . The spectral and elemental characterisation and thermal degradation properties (from mass spectrometric studies) of these new compounds are discussed. The reactions of the metal(IV) pentelide complexes with protic reagents (including water) and halogen-containing compounds have been investigated, and compared with similar reactions for the phosphide-derivative Cp 2 Zr(PPh 2 ) 2 ; the majority are metathetical reactions involving halide /EPh 2 exchange.