Judith A. K. Howard

Proton-induced dimerisation and related reactions of mononuclear tungsten carbyne complexes. Crystal structures of the compounds [W{C(H)(C6H4Me-4)}(I)(CO)2(η-C5H5)] and [W{η2-C2(OH)(C6H4Me-4)}(CO)(PMe3)(η-C5H5)] [BF4]· (Me2CO)

Protonation of the compounds [W( 6;CR)(CO) 2 (η-C 5 H 5 )] R = C 6 H 4 Me-4 or Me) with ca. 0.5 mol equivalents of the reagent HBF 4 ·Et 2 O affords the ditungsten salts [W 2 (η-H)(η-RC 2 R)(CO) 4 (η-C 5 H 5 ) 2 ] [BF 4 ] formed via a coupling of the carbyne groups in the precursors. These compounds are readily deprotonated to give the bridged alkyne complexes [W 2 (η-RC 2 R)(CO) 4 (η-C 5 H 5 ) 2 ], a process which is reversed with acid. Aqueous HI with [W( CR)(CO) 2 (η-C 5 H 5 )] affords the iodo carbene complexes [W( CHR)(I)(CO) 2 (η-C 5 H 5 )]. The structure of the species with R = C 6 H 4 Me-4 has been established by X-ray diffraction [W C 2.05(2)A]. The tolyl substituent on the alkylidene carbon atom is transoid to the ηC 5 H 5 ligand, and the alkylidene group is transoid to the iodine atom. Protonation of the ketenyl-tungsten complexes (R = C 6 H 4 Me-4, PR′ 3 = PMe 3 , PPr 3 i or PMePh 2 ; R = Me, PR′ 3 = PMe 3 ) affords the salts [W{η 2 C 2 (OH)(R)}(CO)(PR′ 3 )(η-C 5 H 5 )][BF 4 ] containing hydroxy-alkyne ligands. The structure of the species with R = C 6 H 4 Me-4 and PR′ 3 - PMe 3 has been established by X-ray diffraction. It contains an acetone molecule of crystallisation which is hydrogen bonded to the proton of the hydroxyl group on the alkyne. The 1 H and 13 C-{ 1 H} NMR spectra of the new compounds are reported and discussed.

Structure and properties of a new conducting organic charge-transfer salt β-(BEDT-TTF) 2AuBr 2

Abstract A new conducting organic charge-transfer salt, β-(BEDT-TTF) 2AuBr 2 has been synthesised and its crystal structure determined. Single crystal four-probe conductivity has been measured at ambient and applied pressures from 300–1.4 K and EPR spectroscopy from 300–4.2 K. β-(BEDT-TTF) 2AuBr 2 crystallises in P 1 (Z=1) with a = 9.020(1), b = 5.707(9), c = 16.320(1) A ; ∝ = 97.60(1), β = 92.12(1), γ = 102.89(1)o; V = 811.8(2) A 3 . While the electronic properties are two-dimensional, the molecular packing of the BEDT-TTF molecules is slightly different from that found in other β-phase BEDT-TTF salts with triatomic counterions. β-(BEDT-TTF) 2AuBr 2 is metallic to 1.4K at pressures up to 5.6 kbar although at all pressures studied there is appreciable hysteresis in the cooling and warming cycles of the conductivity between 6 and 14K. Abrupt transitions in the temperature dependence of both the peak-to-peak EPR linewidth and integrated signal intensity occur near 20K. The possibility of a low temperature structural modification is discussed.

Synthesis and molecular structure of [Au3Ru4(μ3-H)(CO)12(PPh3)3]

Abstract The title compound can be prepared in good yield by heating either [Ru4(μ-H)4(CO)12] or [Au2Ru4(μ3-H)2(CO)12(PPh3)2] with [AuMe(PPh3)] in toluene. The related compound [Au3Ru4(μ3-H)(μ-dppm)(CO)12(PPh3)] has also been prepared. Both trigoldtetraruthenium clusters undergo dynamic behaviour in solution, involving intramolecular rearrangement of the metal core, as revealed by variable temperature NMR studies. The crystal structure of [Au3Ru4(μ3-H)(CO)12(PPh3)3] has been established by an X-ray diffraction study. The metal atom core comprises a trigonal bipyramidal AuRu4 unit with two AuRu2 faces capped by gold atoms.

Structures of three new Ag(CN)2 salts of BEDT-TTF

Three new BEDT-TTF salts of Ag(CN)2 have been obtained, in addition to the two already characterised. (BEDT-TTF)2Ag(CN)2.H2O (I) crystallises in a monoclinic space group, P21, and has a structure similar to the highest Tc organic superconductor, (BEDT-TTF)2Cu(NCS)2. The other two, of the same stoichiometry (BEDT-TTF)2Ag(CN)2 (II and III) crystallise in orthorhombic P21212 and monoclinic P21/n space group respectively. The modes of packing within the 2D layer are similar to one another. I and II are metallic to 150 and 1K respectively, although in II there isa gradual upturn in the resistivity below 15K. The EPR of III indicates Pauli like spin susceptibility between 100 and 300K, with a change to lower susceptibility at about 100K. III is possibly a metal with a metal-semiconductor transition at 100K.

Hydroboration of carbon-tungsten triple bonds; crystal structures of [W2{μ-MeCB(H)Et}(CO)4(η-C5H5)2] and [W{η3-CH(BC8H14)C6H4Me-4}(CO)2(η-C5H5)], and of related complexes

Abstract The compounds [W(≡CR)(CO) 2 L] (L = η-C 5 H 5 , R = Me, C 6 H 4 Me-4 or Ph; L = η-C 5 Me 5 , R = C 6 H 4 Me-4) react with BH 3 · thf to afford the ditungsten compounds [W 2 {μ-RCB(H)CH 2 R}(CO) 4 L 2 ]. The structures of the species with cyclopentadienyl ligands and R = Me and Ph have been established by X-ray diffraction. The reaction between [W(≡CC 6 H 4 Me-4)(CO) 2 (η-C 5 H 5 )] and 9-borabicyclo-[3.3.1]nonane (9-BBN) affords the mononuclear tungsten complex [W{η 3 -CH(BC 8 H 14 )C 6 H 4 Me-4}(CO) 2 (η-C 5 H 5 )]. An X-ray diffraction study identified the unusual η 3 -co-ordination mode of the organoboron ligand. Protonation of the complexes [W 2 {μ-RCB(H)CH 2 R}(CO) 4 (η-C 5 H 5 ) 2 ] (R = Me or C 6 H 4 Me-4) affords salts [W 2 (μ-H){μ-RCB(H)CH 2 R}(CO) 4 (η-C 5 H 5 ) 2 ][X] (X = SO 3 CF 3 or BF 4 ). An X-ray diffraction study on the compound with R = Me failed to locate the two hydrogen atoms associated with the boron but internuclear WW and BW separations, together with 1 H NMR studies, suggest that the cation contains a three centre BH⇀W bond and a four centre μ 3 -HBW 2 interaction. NMR studies ( 1 H and 13 C-{ 1 H}) on all the compounds are reported and discussed.

X-ray and neutron diffraction studies of the crystal and molecular structures of tris(ethylene)platinum and bis(ethylene)(tetrafluoroethylene)platinum

The structures of tris(ethylene)platinum and bis(ethylene (tetrafluoroethylene)platinum have been established by X-ray and neutron diffraction experiments. Tris(ethylene)platinum [Pt(C2H4)3] (I), formed by the displacement of 1, 5-cyclooctadiene from bis(1, 5-cyclooctadiene)platinum by ethylene, crystallizes in the trigonal space group R3̅m (a = b = 7.225(4), c = 11.054(7) Ǻ, 120K) and [Pt(C2H4)2(C2F4)] (II), obtained by the replacement of one ethylene ligand in (I) by tetrafluoroethylene, is shown to be triclinic, space group A1̄ with a = 8.680(3), b = 7.432(3), c = 12.716(6), Ǻ α = 90.13(4), β = 109.42(3), γ = 90.17(3)° (155 K). In both complexes, the six ligated carbon atoms are coplanar with the Pt atom at distances dependent primarily on the nature of the substituent at the contact carbon atom: mean Pt–C(H) 2.218(2), mean Pt–C(F) 2.031(5). Concomitant variations are recorded for the C═C separations, namely C═C(H), 1.382(7); C═C(F), 1.435(6). (I) exhibits a positional disorder of the ethylene ligands between two equivalent sites.

(BEDT-TTF)2CuCl2, a new conducting charge transfer salt

Abstract (BEDT-TTF)2CuCl2 (1), synthesized by oxidation and by electrocrystallization, has been characterized by single crystal X-ray diffraction, four-probe electrical conductivity, EPR and magnetic susceptibility, and shown to be semiconducting with σ ∼ 4 × 10−2 S cm−1 at 290 K and Ea = 0.3 eV. Static magnetic susceptibility and EPR measurements suggest strongly that the material is magnetic, consisting of strongly localized spins ( S = 1 2 per BEDT-TTF dimer) with one-dimensional antiferromagnetic exchange (J = 55 ± 5 K).

Pentamethylcyclopentadienylcopper: A metal ligand fragment isolobal with methylene

Abstract Treatment of copper(I) chloride with LiC5Me5 in tetrahydrofuran affords a reagent which is a useful source of the Cu(η-C5Me5) fragment in synthesis.

Fulvene—platinum complexes: X-ray crystal structure of [Pt(η2-C5H4CPh2)(PPh3)2]

Summary Bis(cycloocta-l,5-diene)platinum reacts with 2,3,4,5-tetraphenylfulvene to afford the complex [Pt( η 2 -CH 2 =C 5 Ph 4 )(cod)] (cod = C 8 H 12 ) in which the metal atom is coordinated to the exo -cyclic double bond of the fulvene. Related compounds [Pt( η 2 -CH 2 =C 5 Ph 4 )L 2 ] (L = PPh 3 , PMePh 2 , PMe 2 Ph, AsPh 3 or CNBu t ) have also been prepared and characterised. Reaction of the complexes [Pt-(C 2 H 4 ) 2 (L)] (L = P(cyclo-C 6 H 11 ) 3 , PPh 3 or AsPh 3 ) with 2,3,4,5-tetraphenylfulvene yields the compounds [Pt(C 2 H 4 )( η 2 -CH 2 =C 5 Ph 4 )(L)]. NMR data for the new species are reported and discussed. 6,6-Diphenylfulvene reacts with [Pt(cod) 2 ] and PPh 3 (1/2 mol ratio) to give the complex [Pt( η 2 -C 5 H 4 CPh 2 )-(PPh 3 ) 2 ] in which the metal atom is bonded to carbon atoms C(2) and C(3) of the fulvene ring. This was established by an X-ray diffraction study. Crystals are monoclinic, space group P2 1 / n , with Z = 4 in a unit cell of dimensions a = 13.761(4), b = 21.653(13), c = 17.395(6) A, β = 104.46(2)°. The structure has been solved and refined to R = 0.064 ( R ′ = 0.064) for 3139 independent diffracted intensities measured at room temperature. The platinum atom is in a trigonal environment formed by the two ligated phosphorus atoms and the C−C bond of the fulvene which is elongated to 1.52(3) A. The C 5 fulvene ring is planar, and makes an angle of 108° with the coordination plane around the platinum. In this plane the metal atom is slightly asymmetrically bonded with Pt−C 2.15(2) and 2.24(2) A, and Pt−P 2.280(6) and 2.301(6) A.

Properties of AuI2- and AuBr2- salts of BEDT-TTF

Abstract We report magnetic and high-pressure conductivity measurements for two β-phase salts of BEDT-TTF. β-(BEDT-TTF) 2 AuI 2 shows a high, temperature independent Pauli susceptibility of 3.4(3) × 10 −4 emu/mole. The superconducting transition (≈ 3.1K from resistivity measurements at 1 bar) is depressed at −1.0 K/kbar. The β-phase AuBr 2 -salt shows some structural differences in comparison to other β-phase salts. Its resistivity remains metallic down to 1.4K, and we find resistive anomalies at ≈ 110K and ≈ 5–13K in the pressure range 1 bar to 5.6 kbar.