Showing papers by "Louis J. Farrugia published in 1996"

Cationic, arylbismuth(III) complexes of the form [BiR2L2]+ and [BiRL4]2+ where L is a neutral two-electron donor ligand

Abstract: Synthetic and structural studies have been made for a range of cationic, ten-electron, four-co-ordinate, diarylbis(ligand)bismuth(III) complexes. Reactions between BiPh2Br, AgBF4 and 2 equivalents of a two-electron donor ligand L afforded the ionic complexes [BiPh2L2][BF4][L = OPPh3 or pyridine (py)]. The first was characterised by X-ray crystallography and comprises [BiPh2(OPPh3)2]+ cations, tetrafluoroborate anions and CH2Cl2 molecules of crystallisation. The bismuth centre is four-co-ordinate with a disphenoidal geometry in which the aryl groups are in equatorial positions with the ligands in axial sites. A long interaction is present between the bismuth centre and one of the fluorines of the BF4 group. A series of similar reactions were also carried out between BiR2Br (R = aryl), TlPF6 and 2 equivalents of L affording the ionic complexes [BiR2L2][PF6][R = Ph, L = OP(NMe2)3 or py; R = 4-MeC6H4, L = OP(NMe2)3; R = 2,4,6-Me3C6H2, L = OP(NMe2)3 or OPPh3]. Two of the complexes have also been characterised by X-ray crystallography, the cations having similar structures to that found in [BiPh2(OPPh3)2][BF4]. The reaction between BiPhBr2, 1 equivalent of TlPF6 and an excess of OP(NMe2)3 afforded the ionic complex [BiPh{OP(NMe2)3}4][PF6]2. The crystal structure of the dication comprises a square-based pyramidal bismuth centre with an apical phenyl group and four basal OP(NMe2)3 ligands. Examples of some dihalogenobismuth cations have also been obtained and their structures are described and compared with those of previously reported examples.

Cationic, four-co-ordinate, bis(organotransition metal)bismuth(III) complexes

Abstract: The ionic complex [Bi{OP(NMe2)3}2{Fe(CO)2(η-C5H5)}2][PF6] has been prepared and its crystal structure determined and compared with that of the valence isoelectronic anion [BiCl2{Fe(CO)2(η-C5H5)}2]–. Both structures have a four-co-ordinate bismuth centre with a geometry best described as equatorially vacant, trigonal bipyramidal in which the Fe(CO)2(η-C5H5) fragments are in the equatorial positions. The structure of [BiCl{Mo(CO)3(η-C5H4Me)}2] has also been determined and is compared with that of [BiCl{Mo(CO)3(η-C5H5)}2].

(μ2-Pinacolato-O,O')-bis(pinacolato-O,O')-diboron

Abstract: The title compound, 2,2′-(2,3-dimethyl-2,3-butanediyldioxy)bis­(4,4,5,5- tetramethyl-1,3,2-dioxaborolane, C18H36B2O6, B2pin3, has two trigonal planar B atoms, each chelated by one pinacolate group, linked by a third pinacolate The molecule is centrosymmetric, with an exactly anti conformation for the bridging pinacolate, and the two Bpin five-membered rings have a twist conformation with torsion angle O-C-C-O = −2739 (13)° The B—O bonds to the bridging pinacolate [1353 (2) A] are slightly shorter than the chelate B—O bonds [1367 (2) and 1373 (2) A]

X-ray crystal structures of Ru3(μ-H)(μ-C,N-C5H4N)(CO)10-n (P i Pr3) n ,n=0,1: A A case of the hydride following the Phosphine?

Abstract: The reaction ofRu3(μ-H)(μ-C,N-C5H4N)(CO)10 (1) with Pt(P i Pr3)(nb)2 {nb = bicyclo-[2.2.1]hept-2-ene} does not afford any Ru-Pt mixed metal clusters, but gives instead the mono-substituted phosphine derivative Ru3(μ-H) (μ-C,N-C5H4N)(CO)9(P i Pr3) (2) as the sole isolable product. Single crystal X-ray studies have been carriedout on 1 and 2. Crystal data for 1: monoclinic, space group P21/c,a = 16.9637(10) A,b = 7.6632(5) A,c = 17.4058(11) A, β = 117.214(5)°,V = 2009.0(2) A3,R(R w) = 0.022 (0.034) for 3090 independent absorption corrected data. Crystal data for 2: triclinic, space group PĪ,a = 9.3389(5) A,b = 11.4376(6) A,c = 15.1781(8) A,α = 76.454(4),β = 79.900(5),γ = 67.428(5)°,V = 1448.8(2) A3 R(R w ) = 0.024 (0.034) for 4564 independent absorption corrected data. In cluster 1 the Ru-Ru bonds are in the range 2.8462(4)-2.8986(4) A. The hydride andσ-pyridyl ligand bridge the same Ru-Ru vector, and the Ru(μ-H) bridge is symmetric, with Ru-H = 1.78(4) and 1.77(4) A. In cluster 2 the Ru-Ru distances show a greater ranger 2.7267(3)-3.0604(3) A. The phosphine ligand is bonded to the Ru atom which is not involved in theσ-pyridyl bridge. In contrast to 1, the hydride andσ-pyridyl ligands in 2 bridge different Ru-Ru vectors and the resultant Ru(μ-H)Ru bridge is asymmetric, with Ru-H = 1.70(4) and 1.89(4) A.

Dynamic disorder in crystalline [Fe2Os(CO)12] and direct evidence for rotation of the Fe2Os triangle in the solid state from variable temperature X-ray diffraction and 13C MAS NMR studies

Abstract: Single-crystal X-ray diffraction data have been collected for [Fe2Os(CO)12] at 120, 223, 288, 292 and 323 K. The two studies at ambient temperature (288 and 292 K) reveal a ≈12 : 1 disorder of the metal triangle as previously reported. At the two lowest temperatures there is no evidence of disorder, while at 323 K the ratio of the major : minor component of disorder decreases significantly to ≈1.4 : 1. Data collected on the same crystal specimens indicate unequivocally that this disorder is dynamic in nature. Two-dimensional exchange and one-dimensional variable-temperature 13C magic angle spinning (MAS) NMR spectroscopy showed that carbonyl exchange is rapid above 306 K in the crystalline solid. Two independent exchange processes of similar energy are observed. The first is consistent with the crystallographic evidence, and involves an ‘in-plane’ rotation of the Fe2Os triangle in steps of 60° within a relatively rigid icosahedral carbonyl manifold. The second involves localised axial–equatorial exchange in the Os(CO)4 group. The Os LIII and Fe K edge X-ray absorption fine structure spectra are consistent with identical structures being present in tetrahydrofuran solution and in the solid phase.

Metal complexes of chiral phosphorylalkoxides: crystal structure of dichlorobis[(1S)-2-(diphenylphosphoryl)-1-methylethanolato]titanium(IV)

Abstract: The chiral alcohols, (1S)-2-(diphenylphosphoryl)-1-methylethanol (S-Hdpomeo) and (1R)-2-(diphenylphosphoryl)-1-phenylethanol (R-Hdpopeo), have been synthesised in optically pure form by a simple two-step procedure. They can be readily deprotonated and the monoanions L so formed co-ordinate readily to TiIV or MoVI to give complexes of the type [TiCl2L2], cis-[MoO2(acac)L] or cis-[MoO2L2]. The complex [TiCl2(S-dpomeo)2] crystallised in the orthorhombic space group P212121, with a= 11.572(1), b= 13.209(1), and c= 20.452(1)A. It is octahedral, with trans chlorides, and cis phosphoryl and alkoxide donors. The six-membered chelate rings adopt asymmetric boat conformations, with equatorially projecting methyl groups. This is the first structurally characterised complex containing a phosphorylalkoxide ligand. The NMR spectroscopic evidence suggests retention of the solid-state structure upon dissolution, and considerable rigidity in the chelate rings.

(R)- and (S)-2-diphenylphosphinoyl-2′-hydroxy-1,1′-binaphthalene: versatile chiral bidentate ligands

Abstract: The homochiral compounds (R)- and (S)-2-diphenylphosphinoyl-2′-hydroxy-1,1′-binaphthalene, (R)- and (S)-Hbinappo, react with TiCl4 or ZrCl4 to produce complexes of bidentate binappo–, [MCl2(binappo)2](M = TiIV or ZrIV). VCl3, FeCl3 and MoO2Cl2 also react with Hbinappo, but require the presence of a base to produce [M(binappo)3](M = VIII or FeIII) or [MoO2(binappo)2]. The complex [MoO2(acac)2](acac = acetylacetonate) reacts with Hbinappo to produce [MoO2(acac)(binappo)]. The vanadium(III) tris(chelate) complexes are readily oxidised in air to [VO(binappo)2]. All of these complexes have been characterised by microanalytical, infrared, and, where appropriate, NMR, electronic and CD spectroscopic techniques. (S)-Hbinappo, [ZrCl2{(S)-binappo}2], [V{(S)-binappo}3] and [VO{(S)-binappo}2] have also been characterised by single-crystal X-ray techniques. In all of the complexes the ligands are co-ordinated through their phenolate and phosphinoyl oxygen atoms forming eight-membered chelate rings. The tris-chelate complexes form stereospecifically, (S)-binappo giving the Λ isomer exclusively, and the (R)-form producing Δ-[M(binappo)3]. Although each of the [M(binappo)3] species are necessarily sterically crowded, little M–O bond elongation is observed in the single-crystal X-ray structure of [V{(S)binappo}3]. Initial attempts at achieving asymmetric induction in TiIV-and VOIV-based oxidations of prochiral sulfides in the presence of these ligands are also presented, but observed enantiomeric excesses are generally < 10%.

Coordination complexes of thallium (III) chloride

Abstract: X-ray crystal structures are reported for two coordination complexes of thallium(III) chloride. In the neutral, monomeric complex [TlCl3(dmpu)2] (dmpu = N,N′-dimethyl-propylene urea), the coordination geometry around the thallium centre is essentially trigonal bipyramidal with equatorial chlorines and axial dmpu ligands similar to a number of other bis-ligand complexes previously characterised; crystal data, orthorhombic, space group Fdd2, a = 17.632(2), b = 27.257(3), c = 8.0353(9) A, D calc = 1.951 Mg/m3, R = 0.028. With the chelating ligand dppmO2 (Ph2P(O)CH2P(O)Ph2), the ionic compound [TlCl2(dppmO2)2] [TlCl4] · 2thf is obtained, which comprises an octahedrally coordinated thallium cation with trans chlorines and a tetrahedral [TlCl4]− anion; crystal data, triclinic, space group P 1, a = 10.7067(9), b = 16.190(2), c = 19.114(2) A, α = 103.55(1), β = 93.710(8), γ = 95.98(1)°, D calc = 1.664 Mg/m3, R = 0.090.

Picrotoximaesin, A Novel Picrotoxane Sesquiterpenoid from the Berries of Maesobotrya Floribunda

Abstract: A new picrotoxane sesquiterpenoid, picrotoximaesin (1), has been isolated from the methanol extract of the seeds of Maesobotrya floribunda. The structure and absolute configuration of the compound were determined using 1H NMR, 13C NMR, EIMS, and X-ray crystallography.

Camphor-based β-hydroxyphosphoryl ligands and their complexes of the type [MoO(O2)2L(H2O)]

Abstract: Homochiral hydroxyphosphoryl compounds, L, such as the novel camphor-based (1R)-endo,endo-3S-(diphenylphosphoryl)-2R-hydroxybornane, have been found to be prevented from behaving as bidentate ligands in the epoxidation catalysts [MoO(O2)2L(H2O)] by unexpectedly strong multiple-bond delocalisation producing near linear Mo–O–P angles.

2-(Diphenylphosphinoyl)propanoate complexes: crystal structure of tris[2-(diphenylphosphinoyl)propanoato]vanadium(III)

Abstract: 2-(Diphenylphosphinoyl)propanoic acid (Hdpop) has been prepared by a simple one-step procedure. The anion behaves as a versatile bidentate ligand, which co-ordinates to cations of VIII, CrIII and FeIII to give octahedral tris(chelate) complexes of the type M(dpop)3, to SnIV to give SnR3(dpop) and SnR2(dpop)2(R = Me or Ph), and to MoVI to give cis-[MoO2(dpop)2]. The derivative Tl(dpop), on the other hand, appears to be coordinated through the carboxylate group only. The α-hydrogen of the dpop ligands of the molybdenum and thallium complexes undergo a slow and reversible hydrogen–deuterium exchange reaction with deuteriomethanol, and the mechanism of this process is discussed. The structure of V(dpop)3·H2O·CH2Cl2, a rare example of a tris(dioxygen) chelate complex of vanadium(III), has been determined by single-crystal X-ray methods. There are two pairs of optical antipodes, Λ(R,R,R), and Δ(S,S,S), in the unit cell. The arrangement of donors about the metal is facial, with all the six-membered chelate rings adopting boat conformations. All the O–V–O bond angles are close to 90°, and the V–O(P) bond lengths averaging 2.023(2)A are slightly longer than those of V–O(C) at 1.979(2)A.