Stephen B. Colbran

Chemical and electrochemical syntheses, and characterization of poly(2,5-dimethoxyaniline) (PDMA): a novel, soluble, conducting polymer

Abstract Poly(2,5-dimethoxyaniline) (PDMA) is obtained either from chemical oxidation with ammonium peroxydisulfate or from electro-oxidation of the corresponding monomer in aqueous hydrochloric acid. UV-Vis, 1 H NMR and FT-IR spectroscopic data, and voltammetric studies are presented to demonstrate that the chemically and electrochemically prepared PDMA samples have essentially the same properties. The voltammetry of PDMA-coated electrodes is described. It is shown that the PDMA film efficiently catalyses the proton-dependent benzoquinone-hydroquinone couple. Studies of the electropolymerization of PDMA from different aqueous acids reveal that the anion determines the surface morphology of the film deposited on the electrode. Preliminary results of the dependence of PDMA conductivity on pH are also presented.

A simple route to bis(terpyridyl)transition metal oligomers

Abstract Coupling of the aniline group in the heteroleptic bis(terpyridyl)ruthenium(II) complex ion, [Ru(terpy)(L 1 )] 2+ (L 1 xa0=xa04′-(4-anilino)-2,2′:6′,2″-terpyridine), with 4′-(4-chlorocarboxyphenyl)-2,2′:6′,2″-terpyridine provides a high yield route to a bis(terpyridyl)ruthenium(II) complex ligand , [Ru(terpy)(L 3 )] 2+ , in which the new amido-linked binucleating bis(terpyridine) ligand, L 3 , has both coordinated and pendant, non-coordinated terpyridyl domains. It is demonstrated that coordination of metal sources or ions by the non-coordinated terpyridine centre in the complex ligand can be used to selectively assemble metallosupramolecular dimers and trimers. The spectroscopic and electrochemical characteristics of the new complexes are described.

Systematic synthesis and characterisation of phosphido-bridged triosmium carbonyl clusters

Phosphine-substituted triosmium clusters Os3(CO)11PR1R2H (a: R1 = R2 = H; b: R1 = Ph, R2 = H; c: R1,R2 = Ph) have been found to yield, via a deprotonation/protonation sequence, the phosphido-bridged clusters (μ-H)Os3(CO)10(M-PR1R2): the intermediate anions [(Os3(CO)10(μ-PR1R2))−] and [((μ-H)Os3(CO)10(μ-PR1))−] in this systematic synthesis are described.

Electron transfer in organometallic clusters. XIV: Crystal and electronic structures of the tricobalt carbon cluster (η5-C5H5)Fe[η5-C5H4-CCo3(CO)9] and the biscarbyne cluster (η5-C5H5)Fe[η5-C5H4CCo3(η5-C5H5)3CH]

Abstract The crystal and molecular structures of (η5-C5H5)Fe[η5--C5H4CCo3(CO)9] (1), Pna21, α 17.354, b 11.463, c 11.207 A Z = 4, R = 0.053, Rw = 0.056 for 939 reflections (I>3σ(I)) at 293 K, and (η5-C5H5Fe[η5--C5H4CCo3(η5C5H5)3CH] (2), P21/n, a 13.807(9), b 11.254(4), c 13.991(9) A, β 99.98(5)°, Z = 4, R = 0.033 and Rw = 0.033 for 3051 observed reflections (I>3σ(I)) at 180 K, have been determined by X-ray methods. The results provide a detailed characterisation of related tricobalt-carbon complexes directly bound to ferrocene residues. In 1 the ferrocenyl moiety tops the pyramidal CCo3 cluster core, while in 2 the CCo3C core is bipyramidal with a ferrocenyl substituent on one capping carbon atom and a hydrogen atom at the other. In both cases the ferrocenyl group is tilted towards one cobalt atom of the cluster core, a distortion believed to be the consequence of the non-degeneracy of the carbyne p(π) orbitals resulting from a cooperative π-interaction between the clusters and the ferrocenyl substituents.

Transition-metal complexes of 4′(4-anilino)-2,2′ : 6′,2″-terpyridine (and derivatives): versatile building blocks for construction of metallooligomers and macromolecules

Transition-metal complexes of 4′(4-anilino)-2,2′ : 6′,2″-terpyridine have been prepared and used to construct co-ordination dimers and polymers linked by new binucleating terpyridine ligands.

A palladium(II) complex of a new iminophosphine ligand derived from diethylenetriamine and 2-(diphenylphosphino)benzaldehyde

Abstract The mononuclear complexes [Pd(oPdien)]X2 {oPdien=N-(2-diphenylphosphinobenzylidene)diethylenetriamine: (4a) X2=[ZnCl4]2−; (4b) X=[PF6]−; (4c) X=Cl−} are described. Complex 4a formed in high yield when [Pd(oPCHO)2Cl2] [oPCHO=2-(diphenylphosphino)benzaldehyde] (1) and [Zn(dien)Cl2] (2) were reacted together in an unsuccessful attempt to template formation of a bimetallic iminophosphine-bridged complex. The X-ray crystal structure of 4b has been determined. The ligand oPdien is the first iminophosphine derived from dien and has been isolated and used to prepare 4c.

Reactions of [MCl2(ppqMe2)2] (M=Pd, Pt) with I− and with CF3SO3H/I− including the synthesis and X-ray crystal structure of the palladium phosphidoxo complex [Pd2(μ-I)2{(PPh20)2H}2]

Abstract The compounds [MI 2 (ppqMe 2 ) 2 ] (5: Mue5f8Pd; 6: Mue5f8Pt) have been synthesised and their thermolyses and reactions with strong acids investigated. Thermolysis of 5 in the presence of excess iodide ion caused complete decomposition of the complex whereas the corresponding reaction of 6 gave the P∼O chelated complex [Pt(ppqMe) 2 ] ( 7 ) in good yield. Treatment of 5 with CF 3 SO 3 H/I− facilitated the loss of the 2,5-dimethoxyphenyl substituent from each phosphine ligand and gave the iodo-bridged palladium(II) phosphidoxo complex [Pd 2 (μ-I) 2 {(PPh 2 O) 2 H} 2 ] ( 8 ). An X-ray single crystal structural analysis of 8 is reported.

Structures and properties of 6-aryl substituted tris(2-pyridylmethyl)amine transition metal complexes

A series of metal(II) complexes of [6-(2′,5′-dimethoxyphenyl)-2-pyridylmethyl]bis(2-pyridylmethyl)amine (L) have been prepared. X-Ray crystal structures have been determined for L and its metal(II) chloride complexes for Mn, Fe, Co, Ni, Cu and Zn and the results compared. The preparation and crystal structure of the unusual carbonato-bridged copper-tetramer [Cu4(L)4(CO3)2][BF4]4·5.2H2O is also described. The solution-state structures of the complexes are deduced from their physicochemical and spectroscopic properties. The Zn(II) complex, [ZnCl2(L)], shows inversion about the ligand amine group on the NMR timescale — results from a variable temperature NMR study are presented and allow estimation of the barrier to amine inversion as 56 ± 0.5 kJ mol−1. Overall, it is found that the intramolecular steric interactions introduced by substitution of the tris(2-pyridylmethyl)amine (tpa)-skeleton by a single 6-aryl group result in significant changes to the structures and properties of the resulting metal complexes: in particular the aryl-substitution in L causes (i) a weaker ligand-field compared to tpa favouring high-spin complexes, (ii) a tendency toward lower coordination numbers, and (iii) hemilability in the Ni(II) and Cu(II) complexes — the aryl-substituted leg of the ligand (L) is coordinatively labile.

Nitrosyl derivatives of tricobaltcarbon clusters

Abstract The nitrosyl clusters PPN[YCCo 3 (CO) 7 (NO)] (Y = Me, Ph, COOH, (C 5 H 5 )Fe(C 5 H 4 )) have been prepared in high yield from the reaction of YCCo 3 (CO) 9 with PPN(NO 2 ) in THF, acetone or acetonitrile. Spectroscopic evidence indicates the structure of the nitrosyl anions is derived from that of YCCo 3 (CO) 9 by the replacement of two CO ligands on one cobalt atom by a linear, terminal nitrosyl group. The nitrosyl metallates are extremely sensitive to oxidation and attempts to protonate the anions resulted in the reformation of the parent YCCo 3 (CO) 9 , molecules. The oxidative electrochemistry of the ferrocene complex, PPN[(C 5 H 5 )Fe(C 5 H 4 CCo 3 (CO) 7 (NO)] is also discussed.

Monomeric and dimeric metal complexes of a simply prepared and versatile pentapyridyldiamine

Abstract The new pentapyridyldiamine, BPA-TPA, is easily made and has been used to prepare [Cu2(BPA-TPA)Br2]2Br2[Cu2Br4] and [Fe(BPA-TPA)](ClO4)2. The crystal structures of these complexes reveal BPA-TPA to be a versatile ligand, for example, capable of bridging two metal centres in chiral [Cu2(μ2-BPA-TPA)Br2]22+ ‘wedges’ or wrapping about a larger metal ion to give novel homoleptic seven co-ordinate species such as the chiral [Fe(κ7N-BPA-TPA)]2+ ion.