Vicki-Anne Tolhurst

Characterization of tetra-aryl benzene isomers by using preparative gas chromatography with mass spectrometry, nuclear magnetic resonance spectroscopy, and x-ray crystallographic methods

The present study describes a preparative gas chromatographic (GC) approach employed to study a series of products arising from reaction of phenylacetylene with para-substituted aryl-iodides under Sonogashira catalysis conditions. GC analysis resolves the isomers from each reaction; however, it cannot provide structural details (their MS data are virtually identical). Since classical liquid chromatography cannot resolve the isomers, preparative-scale GC is the only practical approach to provide further spectroscopic characterization of the isomers. The products are well separated by GC so a single thick-film capillary column is adequate for this case, with operation up to approximately +300 degrees C. By collection of 50+ repeat injections, sufficient material could be isolated for (1)H NMR spectral analysis of the isomers, and for one isomer (isomer I) of a number of analogous related catalytic reaction mixtures, X-ray crystal structure determination enabled complete structural elucidation (absolute configuration) of the substitution pattern of the structure of this isomer. This confirmed isomer I to be the 2-para-aryl-substituted 1,3,5-triphenylbenzene product in all cases. (1)H NMR spectra of isomer I products generally had similar patterns but differed markedly from the second major isomer product (isomer II).

Structural aspects of tertiary amine adducts of alane and gallane

Abstract Structures of N-bound alane (AlH3) and gallane (GaH3) are reported: the dimethylbenzylamine adduct of gallane, [(PhCH2(Me)2NGaH3], which is monomeric with four-coordinate Ga, and the first chlorine containing amino complex of alane, [ClCH2CH2CH2(Me)2NAIH3]2, revealing that hydride bridging is favoured over AlCl interaction in Al obtaining a five-coordination environment. Also presented is a reinvestigation of the previously poorly defined structural determination of the trimethylamine adduct of gallane, [Me3NGaH3].

Bis-amido- complexes of heavier Group 15 metal chlorides with the sterically hindered, N-functionalised amido ligand, [{2-(6-Me)C5H3N}NSiMe3]−

Abstract The reaction of the lithium amide, [2-(6-methyl)pyridyl]trimethylsilylamido-lithium, with antimony(III) or bismuth(III) trichloride in diethyl ether gives the bis-amido antimony(III) or bismuth(III) chloride [{2-(6-Me)C5H3N}NSiMe3]MCl, [M  Sb (1)or Bi(2)] as colourless or yellow prisms respectively. The antimony complex is monometric in the solid state whereas the bismuth complex is dimeric with bridging chlorides.

Synthesis and spectroscopic studies of organometallic Mn(I) complexes containing the novel mixed donor ligands 2-{MeSeCH(2 - n)(SiMe3)n}C5H4N (n = 0-2)

Abstract Treatment of MnBr(CO)5 with one equivalent of the bidentate ligand, 2-{RECH(2−n)(SiMe3)n}C5H4N (E=S, R=Me, Ph, n=0; E=Se, R=Me, n=0, 1, 2) affords the complexes [MnBr(CO)3L] as orange powders. The effect of stepwise substitution at the α-carbon of the ligand by a trimethylsilyl group was investigated using 77Se{1H}- and 55Mn-NMR, and IR spectroscopies. In the case of the pyridyl-selenoether-containing complexes, each additional Me3Si− group increases the σ-donating properties of the ligand, in turn reflected in increased Mn→CO backbonding. The solid-state structure of the parent [MnBr(CO)3{2-(PhSCH2)C5H4N}] showed the molecule to have distorted fac-octahedral geometry. All other compounds were assigned the same stereochemistry based on CO stretching frequency comparisons.

Dithiocarbamate complexes of trivalent aluminium and gallium via metal hydrides

Abstract Reaction of the thiurams [R2NC(S)S]2 (R=Me, Et, Bz) with the trimethylamine complexes of alane (AlH3) and gallane (GaH3) results in the high yield production of the tris-dithiocarbamate complexes [M(S2CNR2)3] (M=Al, Ga) formed via the reductive cleavage of the SS bond. Transmetallation reactions of [(Et2O)k·AlH3]n with [M′(S2CNEt2)n] (M′=As, Sb, n=3, M′=Se, n=2) also result in the synthesis of [Al(S2CNEt2)3] in high yield. A number of these complexes have been structurally characterised: [Al(S2CNEt2)3] (1), isomorphous with its chromium(III) analogue, belonging to the monoclinic P21/n, Z=4, form of the [M(S2CNEt2)3] family; AlS are 2.377(6)–2.390(6) A, similar to values previously established for [Al(S2CNMe2)3]·CH2Cl2, which is isostructural with its Ga analogue, 3, (triclinic P 1 , Z=2), for which GaS are 2.418(2)–2.449(2) A; solvent⋯tris-dithiocarbamate interactions in these species appear to be of negligible significance. AlS are anomalously long cf. GaS in counterpart complexes ca. 2.37, 2.44 A, Al, GaOH2 in their alums being 1.877(3), 1.944(3) A. These observations are reinforced by studies of [M(S2CNBz2)3], M=Al, Ga, 2, 5, monoclinic P21, Z=4, isomorphous with previously reported M=Fe, Co, Ir complexes, and of orthorhombic Fdd2 [Ga(S2CNEt2)3]·2CHCl3, 4, in which the molecule lies on a crystallographic 2-axis, the hydrogen atoms of the chloroform molecules being wedged between the sulfur atoms of the pairs of ligands.

Alane reduction of selenium and tellurium: tertiary amine stabilised dimeric chalcogenides, trans-[{Me3N(H)Al(µ-E)}2](E = Se, Te)

Elemental selenium or tellurium react with trimethylamine alane, [Me3NAlH3], in toluene affording the bis-trimethylamine adducts of the dimeric chalcogenidoalanes, [{HAl(µ-E)}2](E = Se, Te) isolated as the trans-isomers; ab initio molecular orbital calculations on model species show that N-donor Lewis-base solvated dimeric species are the energetically most favourable structures for these chalcogenidoalane species.

Complexes of late transition metals containing the mixed donor ligands 2,6-(RSCH2)2C5H3N (R = Ph, Me): Crystal structures of [{Cu(2,6-(PhSCH2)2C5H3N)(μ-X)}2] (X = Cl, Br) and [Ni(2,6-(PhSCH2)2C5H3N)Br2]

A range of NiX2 and CuX (X = halide) complexes containing the tridentate NS2 ligands 2,6-bis(methylthiomethyl)pyridine (L1) and 2,6-bis(phenylthiomethyl)pyridine (L2) were prepared. Reaction of CuX with 1 molar equivalent of L1 or L2 afforded the binuclear species [{CuL(μ-X)}2] (L = L1, X = Cl; L = L2, X = Cl, Br, I). These compounds have been characterised by IR and 1H NMR spectroscopies, mass spectrometry and microanalysis. Crystal structure determinations of [{CuL2(μ-X)}2] (X = Cl, Br) confirm the dimeric nature of these complexes through bridging halide centres, with the NS2 ligands coordinated through their pyridyl nitrogens and one of the sulfur atoms in a bidentate manner. Reaction of NiX2 with 1 molar equivalent of L1 or L2 afforded mononuclear species for [NiLX2] (L = L1, X = I; L = L2, X = Br, I) and binuclear species for [NiLX2]2 (L = L1, X = Cl, Br; L = L2, X = Cl). These compounds have limited solubility and were characterised through IR and UV-Vis reflectance spectroscopies and microanalysis. The crystal structure determination of [NiL2Br2] confirms the compound to be monomeric with a five-coordinate, square pyramidal nickel centre.

Structural variations in the organo-potassium derivatives of triphenylmethane with PMDTA: a new modification of [Ph3CK · (N,N,N′,N″,N″-pentamethyldiethylenetriamine)]n

Abstract The metalation of triphenylmethane (Ph3CH) with potassium metal in toluene and PMDTA (N,N,N′N″,N″-pentamethyldiethylenetriamine) at 111 °C affords red crystals of [Ph3CK · PMDTA]n (1). X-ray analysis reveals that the single crystal structure of 1 is different to the one shown previously. Here a polymeric zigzag chain instead of a discrete molecule was observed. Crystal data (Mo K α radiation) at −100°C for 1: a = 9.872(2), b = 18.917(4), c = 29.047(6) A , β = 97.63(3)° , monoclinic space group Cc, R = 0.0449 (F2 > 2σ(F2)), wR2 = 0.1420.

Transition metal complexes of 1,3-dihydrobenzo[c]tellurophene: synthesis, spectroscopy and crystal structures

Reaction of 1,3-dihydrobenzo[c]tellurophene (L) with [Cu(MeCN)4]PF6 or AgBF4 yielded [CuL4]PF6 and [AgL4]BF4 respectively, which adopt distorted tetrahedral structures at the metal centre, with the tellurophene ligated via a Te-based lone pair, Cu–Te 2.587(2)–2.596(2) A; Ag–Te 2.7676(7)–2.8104(8) A. With palladium(II) and platinum(II) chlorides the neutral species [PdCl2L2] and [PtCl2L2] were formed readily. Infrared, 125Te-{1H} and 195Pt NMR spectroscopic studies showed that the former is the trans isomer, whereas the latter is the cis isomer. The 125Te-{1H} NMR spectra showed that in solution [RhCl3L3] is a mixture of mer and fac isomers in approximately 3∶2 ratio, whereas RuCl3 reacted with L in EtOH and hypophosphorous acid to give trans-[RuCl2L4] exclusively. The carbonyl derivatives fac-[MnCl(CO)3L2], [Mo(CO)5L], cis-[Mo(CO)4L2] and fac-[Mo(CO)3L3] have also been characterised through IR spectroscopy, 1H, 13C-{1H}, 55Mn, 95Mo and 125Te-{1H} NMR spectroscopy. For the molybdenum species δ(95Mo) and δ(125Te-{1H}) shift to high frequency with increasing substitution of the carbonyl ligands. The crystal structure of [Mo(CO)4L2] confirms the cis geometry and shows the Mo–CO bond lengths trans to L are about 0.10 A shorter than those trans to CO. The 1H NMR spectra of these complexes typically reveal AB quartets for the methylene protons, indicative of co-ordination through a Te-based lone pair in each case. The 125Te-{1H} NMR studies reveal a high frequency co-ordination shift except for the copper and silver species which show δ(125Te-{1H}) to low frequency of that for free L.

[2 + 2] Cycloaddition derivatives of stiba(III)alkene (SbC) and arsa(III)imine (AsN) intermediates

Mild thermolysis of (2-pyridyl)(SiMe3)2CSbCl2 and [2-(6-Me)pyridyl](SiMe3)NAsCl2 affords, respectively, the chloro-bridged polymeric geminal C-centred distibine(III) complex [(2-pyridyl)(SiMe3)CSbCl]∞ 1 and the geminal N-centred arsenic(III) amide [{2-(6-Me)pyridyl}NAsCl]2 2; the proposed mechanism involves the elimination of Me3- SiCl and a [2 + 2] stereospecific cis-cycloaddition of the stibaalkene (SbC) and arsaimine (AsN) intermediates.