Laurence P. Cuffe

A study of the reduction of substituted fulvenes using spectro-electrochemistry and ab initio theory.

Abstract Nine substituted fulvenes have been investigated for their synthetic suitability in the production of ansa -metallocenes. Results obtained from experimental methods, including cyclic voltammetry and spectro-electrochemistry, are combined with DFT calculations. This gives additional structural and spectroscopic information, as well as bonding parameters for fulvenes and their radical anions which are the key intermediate in the reaction. From these results, it can be deduced that certain aryl substituted fulvenes and benzofulvenes are promising synthons for ansa -metallocenes.

The linear and nonlinear optical properties of organometallic chromophores derived from ferrocene, [Fe2(η5-C5H5)2(CO)2(μ-CO)(μ-CCH3)]+[BF4]− and terthienyl spacers. Crystal structure of 2-[(E)-2-ferrocenylethenyl]-5-(2-thienyl)thiophene

Several chromophores based on ferrocene, [Fe2( 5 -C5H5)2(CO)2(-CO)(-CCH3)] + and terthiophene or dithienylbenzo[c]thiophene have been synthesized. Both thienyls have been shown to act as good donor end groups in their own right but contrary to our expectations the benzo[c]thiophene merocyanine has a lower hyperpolarizablity (344 × 10 − 30 esu) than its thienyl congener (650 ×10 −30 esu). The structure of 2-[(E)-2-ferrocenylethenyl]-5-(2-thienyl)thiophene has been determined by single crystal X-ray diffraction. The terminal thienyl (thp) group is disordered over two orientations about the bithienyl C(sp 2 )C(sp 2 ) bond such that the two sulfur atoms in either thp ring are positioned trans/cis in the ratio 0.628(4):0.372(4). The integrity of the alkenyl CC remains with a bond length of 1.332(2) A and the CC lengths adjacent are 1.453(4)/1.441(4) A . Twisting of the rings from planarity occurs along the Fc–CC–(thp)–(thp) axis: the angle which the ethenylthiophene CCC4H2S moiety makes with the C5H4 is 11.2(2)°, and with the major orientation of the disordered terminal thienyl group, 16(1)°.

Novel elimination of hydroxylamine and formation of a nickel tetramer on reactions of glutarodihydroxamic acid with model dinickel hydrolases

Reactions of glutarodihydroxamic acid with the hydrolase enzyme urease models, [Ni2(µ-H2O)(OAc)4(tmen)2] and [Ni2(OAc)3(urea)(tmen)2][OTf], lead to novel hydroxylamine elimination and formation of [Ni2(OAc)2{µ-O(N)(OC)2(CH2)3}(tmen)2][OTf] and the tetramer [Ni4(OAc)2(gluA2)2(tmen)4][OTf]2, respectively, both of which are structurally characterised by X-ray crystallography.

Oxygen versus nitrogen co-ordination in complexes of MoVI and hydroxamate derivatives of α-amino acids: equilibrium, structural and theoretical studies†

Equilibrium and spectroscopic studies showed that MoVI (MoO42–) reacts with α-aminohydroxamic acids (glycine-, sarcosine-, α-alanine-hydroxamic acids, Glyha, Sarha and α-Alaha) in the acidic pH range to give species involving O,O co-ordination whereas, as the pH is raised, species involving N,N co-ordination are formed. The crystal structure of [MoO2(Glyha)2] confirmed formation of an O,O co-ordination isomer. Theoretical studies of the O,O and N,N isomers of [MoO2(Glyha)2] and [MoO2(Sarha)2] showed the former to be the more stable but the relative closeness of the calculated energies of the isomers is in accord with the solution studies. Histidine hydroxamic acid (Hisha) forms O,O isomers in the acidic pH range but as the pH is raised forms two new isomers, one containing the amino nitrogen protonated and co-ordinated in a tridentate manner using the two hydroxamate oxygen atoms and the imidazole N while the other probably contains protonated imidazole N and is co-ordinated via the amino and hydroxamate nitrogens.