Allan H. White

Single component N-O chelated arylnickel(II) complexes as ethene polymerisation and CO/ethene copolymerisation catalysts. Examples of ligand induced changes to the reaction pathway

Abstract Arylnickel(II) phosphine complexes containing substituted N-O bidentate ligands, of the type [NiR(N-O)L][N-O = 4-nitropyridine-2-carboxylate (4-NO2-pyca), R = o-tolyl, L = PPh3; N-O = 2-pyrazinecarboxylate (pyzca), R = o-tolyl, L = PPh3; and N-O = 4-methoxypyridine-2-carboxylate (4-MeO-pyca), R = o-tolyl, L = PPh3] have been prepared and characterised. Single crystal X-ray studies of the complexes [Ni(o-tolyl)(pyca)PPh3], 1, and the isomorphous analogue [Ni(o-tolyl)(4-NO2-pyca)PPh3], 3, show the expected square planar coordination about the nickel centres, with the pyridine nitrogens being trans to the phosphine ligand for both compounds. The coordination spheres of the two complexes are very similar, no elongation of the Ni-N bond for complex 3, which contains the 4-NO2-pyca ligand, being evident. In complex 3 the o-tolyl ligand is disordered over two sites indicating the presence, in the solid state, of two conformers in which the o-methyl groups of o-tolyl are located to either side of the coordination plane. The complexes with substituted pyca ligands form single component catalysts for the conversion of ethene to high molecular weight polyethene and for the copolymerisation of ethene and carbon monoxide to polyketone under mild conditions. The nature of the product, whether predominantly high molecular weight polymer or a mixture of polymer and lower oligomer, is dependent on the basicity of the N-O chelate ligand. From an NMR study of the effect of added ethene on the complex [Ni(o-tolyl)(4-NO2-pyca)PPh3], a mechanism involving alkene promoted ligand dissociation is suggested.

Preparation and thermolysis of complexes derived from some trinuclear ruthenium clusters and 1,4-diphenylbuta-1,3-diyne

Reactions between Ru 3 ( μ -dppm)(CO) 10 and PhC≡CC≡CPh in thf, in the presence of Me 3 NO, afford the complexes Ru 3 ( μ 3 -PhC 2 C≡CPh)( μ -dppm)( μ -CO)(CO) 7 ( 1 ) and Ru 3 ( μ -dppm) μ -C 4 Ph 2 (C≡CPh) 2 (CO) 6 ( 2 ). Complex 1 was also obtained from Ru 3 ( μ 3 -PhC 2 C≡CPh)( μ -CO)(CO) 9 ( 3 ) and dppm in thf on heating. Two of the complexes formed by thermolysis of 1 in xylene at 130°C were identified crystallographically as Ru 3 μ 3 -CPhCHCC(C 6 H 4 -2)( μ -dppm)(CO) 8 ( 4 ) and Ru 3 μ 3 -C 4 H 2 Ph 2 ( μ CO)(CO) 5 (dppm) ( 5 ). In 4 , fragmentation of the cluster and metallation of one of the diyne phenyl groups took place; the dppm ligand bridges two non-bonded Ru atoms. In 5 , partial hydrogenation of the diyne has occurred to give a 2 η 1 : η 4 : η 4 -butadiendiyl ligand, the dppm ligand adopting a chelating mode on one of the two Ru atoms which is η 4 attached to the hydrocarbon. In comparison, thermolysis of 3 gave Ru 4 ( μ 4 -PhC 2 C≡CPh)(CO) n ( n = 12 ( 6 ) and 14 ( 7 )). The former has a distorted C 2 Ru 4 octahedral core, while in the latter the Ru 3 cluster has fragmented to give a ruthenacyclopentadiene derivative in which the central C-C bond bridges an Ru 2 (CO) 8 group.

Cationic methyl-palladium(II) complexes containing bidentate N ∧ O and P ∧ O ligands and a tridentate P ∧ O ∧ N ligand: Synthesis, carbonylation and catalytic applications in the copolymerisation of carbon monoxide and ethene

Abstract Cationic methyl-palladium complexes, containing chelating Nue5f8O, Pue5f8O and Pue5f8Oue5f8N ligands, of the type {[PdMe(Yue5f8O)L]BF4} and {[PdMe(Pue5f8Oue5f8N)]BF4} [Yue5f8O = methylpicolinate, L = PPh3, Ph2PCH2COOEt; Yue5f8O = Ph2PCH2COOEt, L = PPh3, 2,6-lutidine; Pue5f8Oue5f8N = diphenylphosphine-acetic acid-methyl-2-pyridylester (Ph2PCH2CO2CH2(NC5H4-2))] have been synthesized. The crystal structure of the complex {[PdMe(Nue5f8O)PPh3]BF4} indicates distorted square-planar coordination around the palladium centre. The bite angle of the methylpicolinate ligand is small [74.8(4)°] and the Pdue5f8N [2.141(9)A] and Pdue5f8O [2.180(7)A] bonds to the ligand are somewhat elongated. The complexes react readily with CO to give the corresponding acyl complexes, and with the exception of {[PdMe(Nue5f8O)Ph2PCH2COOEt]BF4} catalyse the reaction between CO and ethene at room temperature to give polyketone.

Synthesis and characterisation of nitrile complexes of iron

Abstract The reaction of cis-[FeH2(DMPE)2] (DMPE = 1,2-bis(dimethylphosphino)ethane) (1a) and trans-[FeCl2(DMPE)2] (7a) with acetonitrile, cyanocyclopropane, benzonitrile, p-bromobenzonitrile and terephthalonitrile and reaction of trans-[FeCl2(DEPE)2] (DEPE = 1,2-bis(diethylphosphino)ethane) (7b) with acetonitrile, cyanocyclopropane and benzonitrile in methanol solution resulted in a series of nitrile chloride complexes trans-[FeCl(N≡C-R)(PP)2]+ and bis-nitrile complexes trans-[Fe(N≡C-R)2(PP)2]2+ of iron. All of the complexes have been characterised spectroscopically and four bis-nitrile complexes have been characterised crystallographically. Crystals of trans-[Fe(N≡CCH3)2(DMPE)2][2PF6] (3a) are monoclinic, space group P2/c, with a = 8.697(3), b = 9.165(5), c = 20.026(5) A, β = 107.54(3)°, Z= 2 and R = 0.058 (2300 F values). Crystals of trans-[Fe(N≡CC3H5)2(DEPE)2][2BF4] (4b) are monoclinic, space group P21/n, with a = 11.146(1), b = 15.396(2), c = 11.810(2) A, β = 111.06(1)°, Z = 2 and R = 0.050 (3011 F values). Crystals of trans-[Fe(N≡CPh)2(DMPE)2][2PF6] (5a) are monoclinic, space group P21/n, with a = 11.006(2), b = 12.351(3), c = 13.650(4) A, β = 93.60(2)°, Z = 2 and R = 0.035 (2650 F values). Crystals of trans-[Fe(p-N≡CC6H4Br)2(DMPE)2][2PF6][0.5KPF6] (6a) are tetragonal, space group I4¯c2, with a = b = 20.015(6), c = 21.610(3) A, β = 90.00°, Z = 8 and R = 0.049 (2235 F values).

Trapping of a phenyl group by a ruthenium cluster during dephenylation of coordinated CH2(PPh2)2 (dppm)

Abstract Pyrolysis of {Ru 3 ( μ -dppm)(CO) 9 } n (dppa) ( n = 1 or 2) afforded Ru 3 ( μ 3 -PPhCH 2 PPh 2 )( μ 3 - η 1 : η 2 : P -C 2 PPh 2 )( μ -PPh 2 )( μ -PPh 2 (Ph)(CO) 6 , containing an Ru 3 chain bridged by a dephenylated dppm ligand and by C 2 PPh 2 and PPh 2 ligands derived from the dppa ligand. The phenyl group from the dppm ligand has been trapped by one of the Ru atoms to give a rare example of a cluster-bound σ -Ph group. The molecular structure of Ru 3 ( μ -H){ μ 3 - η 1 , η 2 -CCHP(O)Ph 2 }( μ -PPh 2 )( μ -dppm)(CO) 6 , obtained on one occasion from the mono-cluster complex, is also described.

Homoleptic anionic aryloxolanthanoid(III)complexes

Several anionic complexes of lanthanoid metals with the n2,6-diphenylphenolate ligand have been synthesized and their nroom-temperature single-crystal structures determined. In novel nreactions of anhydrous LnCl n 3 n (Ln = Nd or Er) nwith NaOC n 6 nH n 3 nPh n 2 n-2,6·0.5thf n(thf = tetrahydrofuran) in n1,3,5-tri-tert-butylbenzene at 300 °C, complexes of nthe type n[Na{Ln(OC n 6 nH n 3 nPh n 2 n-2,6) n 4 n n}] were obtained. Crystallisation of n[Na{Nd(OC n 6 nH n 3 nPh n 2 n-2,6) n 4 n n}] from bis(2-methoxyethyl) ether (diglyme) or 1,2-dimethoxyethane n(dme) afforded the corresponding solvated complexes n[Na(diglyme) n 2 n][Nd(OC n 6 nH n 3 nPh n 2 n n-2,6) n 4 n] or n[Na(dme) n 3 n][Nd(OC n 6 nH n 3 nPh n 2 n n-2,6) n 4 n] respectively, and from an analogous reaction for nLn = Er n[Na(diglyme) n 2 n][Er(OC n 6 nH n 3 nPh n 2 n n-2,6) n 4 n] was isolated. The complexes n[Na(diglyme) n 2 n][Ln(OC n 6 nH n 3 nPh n 2 n n-2,6) n 4 n] (Ln = Nd or Er) are isomorphous. Their nstructures revealed novel discrete homoleptic ntetrakis(aryloxo)lanthanoid(III) anions, well separated from nthe solvated sodium cations. Annealing the reaction mixture for the nsynthesis of n[Na{Nd(OC n 6 nH n 3 nPh n 2 n-2,6) n 4 n n}] at 120 °C gave single crystals of a monomeric nbimetallic in which the sodium ion is encapsulated by three aryloxide noxygens as well as by three phenyl rings of the phenolate ligand, and nneodymium is surrounded by a highly distorted tetrahedral arrangement of naryloxide oxygens. There are also intramolecular π-Ph–M n(M = Na or Nd) interactions.

Regioselectivity in the Lithiation of 1,3-Disubstituted Arenes

The regioselectivity of the lithiation of 1,4,5,8-tetramethoxynaphthalene-2-carbaldehyde (7) with butyllithium or phenyllithium in the presence of N,N,N′-trimethylethylenediamine and the subsequent bromination of the lithiated species so generated with 1,2-dibromotetrafluoroethane were investigated. Similar investigations with butyllithium as base in the presence of N,N,N′,N′-tetramethylethylenediamine or potassium t-butoxide were carried out on 1,4,5,8-tetramethoxynaphthalene-2-methanol (14). These studies were extended to 1,5,8-trimethoxynaphthalene-3-methanol (25), 3-methoxybenzenemethanol (29) and 3,5-dimethoxybenzenemethanol (32). The X-ray crystal structure of 6-bromo-1,4,5,8-tetramethoxynaphthalene-2-methanol (17) is described.

Synthesis, Structure and Alkali Metal Ion Binding Properties of a Podand Polyether Derived from Calix[4]arene, 5,11,17,23-tetra-tert-butyl-25,27-di(phenylmethoxy)-26,28-di(2‘-methoxyethoxy)-calix[4]arene

The ligand 5,11,17,23-tetra-t-butyl-25,27-di(phenylmethoxy)-26,28-di(2-methoxy-ethoxy)calix[4]arene,designed as an analogue of some calixcrown speciesin order to evaluate possible origins of their selectivity in alkali metal ion binding, has been synthesised and structurally characterised by X-ray crystallography. The crystals are monoclinic, P21/n, a = 15.940(6), b = 19.388(5), c = 20.020(5) Å,β = 109.10(2) deg., Z = 4, conventional R on |F| being 0.073 for 3454 independent, ’observed‘ (I > 3σ(I)) reflections. 1H-NMR studies in 1:1 CD3CN/CDCl3solvent have shown that the ligand exerts a strong preference for the lighteralkali metal ions (Li+ and Na+) contrary to the binding behaviour of knowncalixcrowns. This may reflect interactions restricted to the lower rim donor atoms without concomitant interaction with the calixarene π-electrons, perhaps because the latter interactions are substituted by those with the benzyl group π-electrons.

Synthesis of novel conformationally restricted L-glutamate analogues

The novel, optically active and conformationally restricted L-glutamate analogues 6, 7 and 11 have been prepared via the PPh3 catalysed cycloaddition of the allenes 2 and 9 with the chiral oxazolidinone 1.

Absolute stereochemistry of 1,2′-linked bi(naphthoquinone)s

Asymmetric syntheses of the enantiomers of the naturally occurring natropisomerically chiral 1,2′-linked bi(naphthoquinone)s n8′-hydroxyisodiospyrin and isodiospyrin have allowed their absolute nconfigurations to be assigned by X-ray and circular dichroism spectral nstudies of synthetic intermediates.