Ian R. Butler

Palladium (II) complexes of (diisopropylphosphino)-ferrocenes: improved catalysts for the Heck reaction

Abstract Palladium (II) chloride complexes of (diisopropylphosphino)ferrocenes act as efficient catalyst precursors for the Heck reaction, providing yields well in excess of the corresponding (diphenylphosphino)ferrocene analogues such as the archetypal [PdCl 2 (dppf)].

THE SYNTHESIS AND CHARACTERISATION OF HETEROSUBSTITUTED AMINOFERROCENES

Abstract The synthesis of 1-bromo-1′-aminoferrocene is reported using a simple synthetic methodology. This compound serves as a useful precursor to other heterosubstituted aminoferrocenes. For example, (1′-amino)ferrocenecarboxylic acid has been obtained and is conveniently isolated in its C -protected form by lithiation of 1-bromo-1′-aminoferrocene, quenching with solid carbon dioxide and esterification of the resulting carboxylate with methanolic HCl. The new ligand 1-diphenylphosphino-1′-aminoferrocene has also been obtained using a similar methodology.

Ferrocenylpyridines: a new synthesis of 4′-ferrocenylterpyridine and the single crystal structure of a C3-ferrocenophane, [(η-C5H4CHCH2C(O)2-C5H4N)2CHC(O)2-C5H4N]Fe

Abstract The synthesis and characterization of the new ligand 4′-ferrocenylterpyridine is reported together with the synthesis and characterization of a new C 3 -ferrocenophane containing three acylpyridine units. The terpyridine ligand was prepared in a two-step synthesis from ferrocenecarbaldehyde by aldol condensation and subsequent cyclization. Attempts to prepare the analogous 1,1′-bis-terpyridylferrocene derivative resulted in the formation of a new ferrocenophane : a consequence of inter-annular attack of an anion generated on the side chain of one cyclopentadienyl ring on a carbonyl centre on the side chain of the other cyclopentadienyl ring. The single crystal X-ray structure of this ferrocenophane, [( η -C 5 H 4 CHCH 2 C(O)2-C 5 H 4 N) 2 CHC(O)2-C 5 H 4 N]Fe, as its dichloromethane solvate, [Fe(C 33 H 27 N 3 O 3 )] · CH 2 Cl 2 , has been determined.

A remarkably simple route to tri-substituted ferrocenes: the ortho-lithiation of 1,1′-dibromoferrocene and bromoferrocene

Abstract The ortho- lithiation of 1,1′-dibromoferrocene is reported for the first time. The reaction is carried out using LDA at low temperature in THF to avoid metathesis. A number of electrophilic quenching reagents have been used, resulting in the formation of a new series of substituted 1,1′-dibromoferrocenes: [( η 5 -C 5 H 4 Br)Fe( η 5 -C 5 H 3 (Br)(R)- 1,2 )], R=–PPh 2 , –SCH 3 , –P(iPr) 2 , –CHO, –CO 2 H, –S(O) p- tol. The further derivation of one of these compounds, R=–PPh 2 , has been carried out, again using a lithiation and quench sequence, to demonstrate the versatility of these product compounds as precursors in their own right. In this manner a range of tri-substituted ferrocenes of the type [( η 5 -C 5 H 4 R)Fe( η 5 -C 5 H 3 (R)PPh 2 - 1,2 )], R=–PPh 2 , –SCH 3 , –P( i Pr) 2 , –CHO, –CO 2 H, have been prepared. The ortho -lithiation of bromoferrocene has been similarly achieved and thus this also provides a simple and effective new route to 1,2-disubstituted ferrocenes.

FERROCENYL ANTHRACENES : SYNTHESIS AND MOLECULAR STRUCTURE

Abstract The synthesis of a series of ferrocenylanthracene derivatives is described, utilising the palladium catalysed coupling reaction of 1,1′-bis(chlorozincio)ferrocene with halo-anthracenes. Bis-1,1′-(9-anthracenyl)ferrocene (1) was characterised by single crystal X-ray diffraction and shows an eclipsed ferrocenyl geometry. X-ray crystallographic studies indicate that there are no clear stacking interactions of either an intra- or intermolecular nature between the anthracenyl rings in the structure. A series of 9- and 10-disubstituted ferrocenylanthracene derivatives has also been prepared. In each case the palladium catalyst (Pd(dppf)Cl2) is recovered in a modified form, e.g. as the [(dppf)PdBr(9-anthracenyl)] complex in the synthesis of bis-1,1′-(9-anthracenyl)ferrocene. The single crystal X-ray structure of one such palladium complex [(dppf)PdBr-9-(10-chloroanthracenyl)] (15a) has been determined in a case where chloride/bromide exchange had occurred in the palladium complex intermediate. The potential application of compound 1 as synthon for the construction of a molecular sensing device is discussed. Cyclic voltammetry and fluorescence studies have been carried out for selected derivatives.

1,3-Bisdiphenylphosphinoferrocenes: the unexpected 2,5,-dilithiation of dibromoferrocene towards a new area of ferrocene-ligand chemistry

Abstract The synthesis and characterization of 1,3-bis-diphenylphosphinoferrocene is described for the first time. The ligand is obtained as a byproduct of the ortho-lithiation of 1,1′-dibromoferrocene, as a consequence of the dilithiation of one of the cyclopentadienyl rings. The intermediate compound 1,1′-dibromo-2,5-bis-(diphenylphosphino)ferrocene which is the precursor compound to the new ligand has been structurally characterized. Further reaction of 1,1′-dibromo-2,5-bis-(diphenylphosphino)ferrocene with n-butyllithium followed by quenching with chlorodiphenylphosphine affords the new 1,2,3,1′-tetrakis(diphenylphosphino)ferrocene, while the similar reaction of 1,1′-dibromo,2,2′-bis(diphenylphosphino)ferrocene gives 1,1′,2,2′-tetrakis(diphenylphosphino)ferrocene.

Diferrocenyltriphosphines 1: five-coordinate ruthenium complexes

Abstract The ligand bis-1-(1′-diphenylphosphinoferrocenyl)phenylphosphine, triphosfer, reacts with dichlorotris-triphenylphosphineruthenium(II) to give the complex [(triphosfer)RuCl 2 ], ( 17 ), in almost quantitative yield. This complex reacts with CO at ambient temperature to afford [(triphosfer)Ru(CO)Cl 2 ]. Three related complexes, [{(η-R 2 PC 5 H 4 )Fe–μ 2 -(η-C 5 H 4 P(R′)η-C 5 H 4 )Fe(η-C 5 H 4 R 2 )}RuCl 2 ], R,R′=Ph, i Pr ( 18–20 ), exhibit identical chemical properties. Reaction of complexes 17–20 with excess PMe 2 Ph results in the deligation of the ferrocene ligand. The electrochemistry shows that while the diferrocenyltriphosphine ligands undergo a single two-electron oxidation, irreversible in character, complexes ( 17–19 ) exhibit two separated one-electron oxidations having features of chemical reversibility. This data suggests that while within the ligands no electronic communication exists between the two ferrocene subunits, complexation with RuCl 2 allows communication between the two ferrocenes. The single crystal X-ray structure of [(triphosfer)RuCl 2 ] has been determined.

Ferrocenylpyridines: New isomers of ferrocenyl bipyridines and terpyridine

Abstract The synthesis, characterization and a discussion of the mechanism of formation of the two new ferrocenylpyridines 1-[6-(2,2′-bipyridyl)]-1′-[4″-(2″,2‴-bipyridyl)]-ferrocene and 3′-ferrocenyl-2,2′: 6′,2″-terpyridine is reported.

Studies of Dye Sensitisation Kinetics and Sorption Isotherms of Direct Red 23 on Titania

Sorption kinetics and isotherms have been measured for a commercial dye (Direct Red 23) on different samples of powdered Titania, and the data were analysed to better understand the dye sensitization process for dye sensitised solar cells (DSSCs). For the sorption kinetics, the data show rapid initial sorption (<1 hour) followed by slower rate of increasing uptake between 1 and 24 hours. While higher initial concentrations of dye correspond to higher sorption overall, less dye is absorbed from higher initial dye concentrations when considered as percentage uptake. The correlation between the sorption data and model isotherms has been considered with time. The Langmuir model shows better correlations compared to the Freundlich isotherm. The dye uptake data has also been correlated with Titania characterization data (X-ray diffraction, scanning electron microscopy, BET and zero point charge analysis). Kinetic data show significantly better fits to second-order models compared to first order. This suggests that chemisorption is taking place and that the interaction between the dye sorbate and the Titania sorbent involves electron sharing to form an ester bond.

A convenient preparation of iodoferrocenes

Abstract The synthesis of iodoferrocenes using stannylferrocenes as key intermediates is described. The method is suitable for the bulk preparation of iodoferrocenes.