Cu-catalysed arylation reactions devoted to the formation of C-C and C-heteroatom bonds (Ullmann-type couplings) have acquired great importance in the last decade. This review discusses the history and development of coupling reactions between aryl halides and various classes of nucleophiles, focusing mostly on the different mechanisms proposed through the years. Selected mechanistic investigations are treated more in depth than others. For example, evidence in favour or against radical mechanisms is discussed. Cu(I) and Cu(III) complexes involved in the Ullmann reaction and N/O selectivity in aminoalcohol arylation are discussed. A separate section has been dedicated to the synthesis of heterocyclic rings through intramolecular couplings. Finally, recent developments in green chemistry for these reactions, such as reactions in aqueous media and heterogeneous catalysis, have also been reviewed.

A number of new ruthenium compounds have been synthesised, isolated and characterised, which exhibit excellent cytotoxicity against a number of different human tumour cell lines including a defined cisplatin resistant cell line and colon cancer cell lines. Addition of hydrophobic groups to the ruthenium molecules has a positive effect on the cytotoxicity values. Evidence is provided that, after incubation of a ruthenium compound with a 46 mer oligonucleotide duplex and subsequent nuclease treatment, ruthenium is bound to a guanine residue.

A number of new ionic titanocene compounds have been isolated and characterized. These exhibit significant cytotoxicity against a number of different human tumor cell lines including a defined cisplatin-resistant cell line. One of the compounds is an order of magnitude more active than its nonfunctionalized equivalent.

Novel rhodium, iridium, and ruthenium half-sandwich complexes containing (N,N)-bound picolinamide ligands have been prepared for use as anticancer agents. The complexes show promising cytotoxicities, with the presence, position, and number of halides having a significant effect on the corresponding IC50 values. One ruthenium complex was found to be more cytotoxic than cisplatin on HT-29 and MCF-7 cells after 5 days and 1 h, respectively, and it remains active with MCF-7 cells even under hypoxic conditions, making it a promising candidate for in vivo studies.

We show that the binding mode adopted by picolinamide derivatives in organometallic Os(II) and Ru(II) half-sandwich complexes can lead to contrasting cancer cell cytotoxicity. N-Phenyl picolinamide derivatives (XY) in Os(II) (1, 3-5, 7, 9) and Ru(II) (2, 6, 8, 10) complexes [(eta(6)-arene)(Os/Ru)(XY)Cl](n+), where arene = p-cymene (1-8, 10) or biphenyl (9), can act as N,N- or N,O-donors. Electron-withdrawing substituents on the phenyl ring resulted in N,N-coordination and electron-donating substituents in N,O-coordination. Dynamic interconversion between N,O and N,N configurations can occur in solution and is time- and temperature- (irreversible) as well as pH-dependent (reversible). The neutral N,N-coordinated compounds (1-5 and 9) hydrolyzed rapidly (t(1/2) > 4 > 1 > 9). In contrast, N,O-coordinated complexes 7 and 8 hydrolyzed slowly, did not bind to guanine or adenine, and were nontoxic.