Neil A. Bailey

The syntheses, properties and crystal and molecular structures of the copper(II) and nickel(II) complexes of the non-symmetric schiff bases, derived from 1,2-diaminoethane, pentane-2,4-dione and 2-pyrollecarboxaldehyde

Abstract The synthesis of a non-symmetric Schiff base derived from 1,2-diaminoethane, pentane-2,4-dione and 2-pyrollecarboxaldehyde is described and the copper(II) and nickel(II) complexes are reported. The crystal structure of the nickel(II) complex is monoclinic, R = 0.0368, 1451 reflections: the crystal structure of the copper(II) complex is isomorphous, ( R = 0.0387, 1239 reflections). In both structures, the metals adopt square-planar coordination geometries and long intermolecular contacts lead to weak oligomerisation. The EPR spectra of the copper(II) complex is discussed and related to the structure.

Transition metal complexes with terminal or bridging imidato(1–) ligands. X-Ray crystal structures of trans-[Ir(CO)(NCOC2F4CO)(PPh3)2] and [{Pd(o-C6H4CHNPh)(µ-NCOC2H4CO)}2]·CH2Cl2, spectroscopic studies of [Mn(CO)5(NCOC2H4CO)], and the nature of the metal–nitrogen bond

The reaction of [Mn(CO)5Br] with the thallium(I) salt of succinimide yields the novel succinimidato(1–) complex [Mn(CO)5([graphic omitted]O)]. The imide-derived ligand is found to behave as a pseudo-halogen in terms of its σ-acceptor and π-donor properties by ‘Graham’ analysis of i.r. spectroscopic data. Mononuclear arylpalladium complexes, trans-[Pd(Ph)(im)(PPh3)2][im =Imidato(1–) ligand], and related carbonyl–rhodium and –iridium complexes, trans-[M (CO)(im)(PPh3)2], may be synthesised by reaction of the corresponding chloro-complexes with succinimide, phthalimide, or tetrafluorosuccinimide. The structure of trans-[Ir(CO)([graphic omitted]O)(PPh3)2] has been established crystallographically (Ir–N 2.09 A). Binuclear arylpalladium complexes containing halide or acetate bridges react with imides in the presence of base to give complexes in which the Imidato(1–) ligand adopts a novel bridging co-ordination mode, via nitrogen and one of the carbonyl oxygens. The structure of one complex of this type, [{Pd(o-C6H4CHNPh)(µ-[graphic omitted]O)}2]·CH2Cl2, has been confirmed crystallographically.

Formation of axial phenolate–metal bonds in square-pyramidal complexes

Copper(II) complexes derived from tripodal ligands capable of forming 5,6,6- or 5,5,6-membered chelate ring sequences have been synthesised and characterised. The crystal structures of two complexes [CuL-(O2CBut)]·MeCN [HL =(2-hydroxy-5-nitrophenylmethyl)(pyridin-2-ylethyl)(pyridin-2-ylmethyl)amine] and [CuL(O2CMe)]·H2O [HL =(2-hydroxy-5-nitrophenylmethyl)bis(pyridin-2-ylmethyl)amine] have been solved. They are neutral, mononuclear copper(II) species in the solid state. In contrast to copper(II) complexes derived from related tripodal ligands forming 6,6,6-membered chelate rings, the present complexes have an axial phenolate–copper(II) bond in their square-pyramidal structures. The formation of this bond is related to the steric factors arising from the flexibility of the ligand pendant arms. The complex [CuL(O2CMe)] exhibits structural features related to the biosite in galactose oxidase; an acetate co-ordinates to copper equatorially and a phenolate oxygen atom occupies the axial position.

Cyclometallated complexes of palladium(II) with the diphosphines trans-Ph2 PCHCHPPh2, cis-Ph2PCHCHPPh2 and Ph2P(CH2)4PPh2. The X-ray crystal structure of [{Pdd[2,4-Me2C6H2C(H)NCy]}2 (μ-Ph2P(CH2)4PPh2)(μ-Cl)2]

Abstract Treatment of 2,4-Me 2 C 6 H 3 C(H)NCy ( a ) or 2,3-(MeO) 2 C 6 H 3 C(H)NCy ( b ) (Cy  cyclohexyl) with palladium(II) acetate gave the cyclometallated acetato-bridged complexes 1a and 1b . These were converted into the analogous halide-bridged complexes by reaction with NaX ( 2a , 2b , X  Cl; 3a , 3b , X  Br; 4a , 4b , X  I). The halide-bridged dimers react: (a) with trans -Ph 2 PCHCHPPh 2 ( trans -dppe) and Ph 2 P(CH 2 ) 4 PPh 2 (dppb) in a dimer/diphosphine 1:1 molar ratio to give the dinuclear phosphine-bridged complexes 5a – 7a , 5b – 7b ( trans -dppe) and 8a – 10a , 8b – 10b (dppb); and (b) with cis -Ph 2 PCHCHPPh 2 ( cis -dppe) or Ph 2 P(CH 2 ) 4 PPh 2 (dppb), in a dimer/diphosphine 1:2 molar ratio, and NH 4 PF 6 , to give the mononuclear cyclometallated species 11a , 11b ( cis -dppe), or 12a and 12b (dppb). The structure of 8a is described. This is the first structurally characterised dinuclear palladium (II) complex with two cyclometallated moieties bounded through a diphosphine ligand. The crystals are monoclinic, space group P 2 1 / n with a = 1084.1(7), b = 3067.7(28), c = 1181.9(10) pm, β = 114.22(6)°, U 3.585(5) nm 3 , Z = 2, R = 0.0731 and R w = 0.0602 for 3970 independent reflections.

Mesogenic Transition Metal Complexes Liquid Crystal Phase Behaviour and Crystal and Molecular Structure of Some Nitrile Complexes of the Platinum Metals

Abstract A new range of transition metal-containing liquid crystals is formed by complexing classical organic mesogens directly to a metal. Thus, reaction of [PdCl2(PhCN)2] with 4-n-pentyl-4′-cyanobiphenyl (5CB) leads to [PdCl2(5CB)2] which exhibits a monotropic nematic phase. Complexes of long chain 4-alkyloxy-4′-cyanobiphenyls show enantiotropic mesophases. Analogously, reaction of [PtCl2(PhCN)2] or [Rh2Cl2(CO)4] with 4-alkyl-4′-cyanobiphenyls (L) yields mesogenic [PtCl2L2] or cis-[RhCl(CO)2 L] respectively. The crystal and molecular structure of [PdCl2(5CB)2] and [PtCl2(8CB)2] are also reported and show different packing in the solid state.

Polyphenol–caffeine complexation

Crystal structures of complexes of caffeine (1) with methyl gallate (2), m-nitrobenzoic acid (3), and potassium chlorogenate (4) are described; the results are used to comment on possible modes of association of natural polyphenols with substrates such as proteins.

Metallo-mesogens and liquid crystals with a heart of gold

Abstract Metallo-mesogens (molecular coordination complexes which show liquid crystalline properties) of various types have been made and characterized, including [MCl2(XC6H4C6H4CN)2], (M = Pd and Pt; X = n-alkyl and n-alkyloxy), [Rh(CO)2Cl(XC6H4C6H4CN)], [Ag(ROC6H4CHCHC5H4N2)]+Y−, [AuCl(ROC6H4CHCHC5H4N)], [M′(ROC6H4CS2)2]n (M′ = Zn, Ni, Pd) and [Au(ROC6H4CS2)X2] (X = Cl, Br). Most of these molecules are rod-like, with rigid central cores containing the metal and the ligating atoms, and flexible n-alkyl or -alkyloxy tails extending out along the molecular axes. They show the typical behaviour of thermotropic mesogens. The behaviour of the complexes can parallel that of the ligands (when they are also mesogenic), but transitions generally occur at rather higher temperatures. Many of these complexes exhibit unusual and useful optical properties; for example the palladium complexes (1) show a high birefringence.

Manganese(II) and iron(III) complexes of the tridentate ligands bis(benzimidazol-2-ylmethyl)-amine (L1) and -methylamine (L2). Crystal structures of [MnL1(CH3CO2)2], [FeL2Cl3], and [Fe2L12(µ-O){µ-(CH3)3CCO2}2][ClO4]2

The preparation and characterisation of [MnL1(CH3CO2)2](1), [Mn6(µ4-O)2(C6H5CO2)10(H2O)4](9), [FeL1Cl3](10), [FeL2Cl3](2), and [Fe2L12(µ-O){µ-(CH3)3CCO2}2][ClO4]2(3) are reported where L1 and L2 are bis(benzimidazol-2-ylmethyl)amine and bis(benzimidazol-2-ylmethyl)methylamine. The molecular structures of (1), (2), and (3) were determined by X-ray diffraction. Complex (1) exists as a discrete, neutral, mononuclear species in the solid state. The manganese(II) ion is five-co-ordinate with the tridentate ligand bound in a meridional manner. Both acetates are monodentate with Mn–O distances of 2.076(5) and 2.158(5)A. Complex (9) contains a [Mn6(µ-O)2]10+ core, formally 4MnII :2MnIII. Complex (2) is neutral, mononuclear, distorted octahedral. The ligand co-ordinates in a similar manner to that seen in (1) and the chlorides occupy the three remaining meridional sites, with Fe–Cl(equatorial) 2.318(5)A and Fe–Cl(axial) 2.322(5) and 2.433(5)A. The Mossbauer spectrum of (10) at room temperature comprises a quadrupole doublet: δ= 0.40(1), ΔEQ= 0.33(2) mm s–1. Complex (3) is a dinuclear iron(III) species containing the triply bridged [Fe2(µ-O)(µ-RCO2)2]2+ core. The Fe ⋯ Fe distance is 3.075(5)A and the Fe–O(oxo)–Fe angle is 117.0(6)°. The high-spin iron(III) centres are antiferromagnetically coupled with J=–116 cm–1. The Mossbauer spectra of (3) at room temperature and 70 K consist of doublets with δ= 0.44(1), ΔEQ= 1.37(2), and δ= 0.55(1), ΔEQ= 1.30(2) mm s–1 respectively.

The synthesis of tin(IV) complexes of 2-(2-mercaptophenyl)-imino-phenols by the electrochemical cleavage of a disulphide bond: The crystal structure of bis{2-(2-mercaptophenyl)imino-4,6-dimethoxy-phenoxy}tin(IV)

Abstract The electrochemical oxidation of anodic tin in acetonitrile solutions in the Schiff bases derived from the required salicylaldehyde and bis-(2-aminophenyl)disulphide (L 2 H 2 ) yields compounds of formulation SnL 2 . The crystal structure of bis{2-(2-mercaptophenyl) imino-4,6-dimethoxy-phenoxy}tin(IV) [SnL 1 2 ] have been determined. The tin atom has an octahedral coordination geometry with a meridional ligand occupancy; the average SnN, SnO and SnS bond lengths are 2.17, 2.07 and 2.47 A, respectively.

The chemistry of tetraphenylcyclopentadienone complexes of ruthenium and rhodium: the X-ray crystal structure of [Ru{η5-C5Ph4OC(O)CH(OMe)Ph}(CO)2Cl]

[Ru(η4-C5Ph4O)(CO)3](1) and [{Rh(η4-C5Ph4O)Cl}2](2) react with L-(–)-α-methylbenzylamine to give the tetraphenylcyclopentadienone complexes [Ru(η4-C5Ph4O)(CO)2{NH2CH(Me)Ph}] and [Rh(η4-C5Ph4O)Cl{NH2CH(Me)Ph}] respectively; trimethylamine N-oxide also reacts with complex (1) to give the amine adduct [Ru(η4-C5Ph4O)(CO)2(NMe3)](5). Complexes (2) and (5) oxidatively add HX to give the corresponding hydroxytetraphenylcyclopentadienyl complexes [{M(η5-C5Ph4OH)(L)X}n][M = Ru, L =(CO)2, X = Cl, OC(O)CF3, or OC(O)Me, n= 1; M = Rh, X = L = Cl, n= 2]; all these compounds readily reductively eliminate HX, the ease of this reaction increasing in the order of X and M listed. Methyl iodide also oxidatively adds to (5) to give the stable complex [Ru(η5-C5Ph4OMe)(CO)2I]. The acyl chlorides RC(O)Cl similarly oxidatively add to complexes (1) and (2) to give the corresponding ester complexes [M{η5-C5Ph4OC(O)R}(L)Cl}n][M = Ru, L =(CO)2, n= 1, R = Me; M = Rh, L = Cl, n= 2, R = Me or (–)CH(OMe)Ph]; the complex [Ru(η5-C5Ph4OH)(CO)2Cl] also reacts with RC(O)Cl to give [Ru{η5-C5Ph4OC(O)R}(CO)2Cl][R = Me or (–)CH(OMe)Ph (14)]. The X-ray structure of (14) is reported; the crystals are orthorhombic, space group p212121(no. 19) with a= 24.58(3), b= 14.518(13), c= 9.299(4)A, and Z= 4. The structure was solved via the heavy-atom method and refined to R= 0.0541 using 1 425 independent reflections. Carbonylation of [{Rh(η5-C5Ph4OC(O)R*)Cl2}2] in the presence of zinc gives [Rh{η5-C5Ph4OC(O)R*}(CO)2] and complex (14) undergoes carbonyl substitution with triphenylphosphine to give the two diastereoisomers of [Ru{η5-C5Ph4OC(O)R*}(CO)(PPh3)Cl][R*=(–)CH(OMe)Ph]. The use of [Rh{η5-C5Ph4OC(O)R*}(CO)2] and [{Rh(η5-C5Ph4OC(O)R*}Cl2}2][R*=(–)CH(OMe)Ph] as asymmetric hydroformylation and hydrogenation catalysts respectively is briefly discussed. I.r., 1H, 13C, and 31P n.m.r. spectroscopic data are presented.