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Abstract: The DNA binding of polypyridyl (pp) (η5-pentamethylcyclopentadienyl)iridium(III) complexes of the type [(η5-C5Me5)IrCl(pp)](CF3SO3) (pp=dpq, dppz, dppn) (1–3) and [(η5-C5Me5)Ir(L)(pp)](CF3SO3)2 (L=(NH2)2CS, pp=dpq, dppz, dppn) (4–6), (L=(NMe2)2CS, pp=dpq, dppz, dppn) (7–9) has been studied by UV/Vis spectroscopy, circular dichroism and viscosity measurements. Modest increases ΔT m of 2–7°C in the thermal denaturation temperature (for r =[complex]/[DNA]=0.1) and the effectively unchanged values or decreases in viscosity observed for CT DNA after incubation with complexes 1–3 for 60min are in accordance with thermodynamically preferred coordinative Ir-N (nucleobase) binding to the biopolymer. However, kinetically favoured intercalation for 2 and 3 leads to large initial hypochromic UV/Vis shifts for the π–π∗ transitions of their polypyridyl ligands in the range 300–450nm. As indicated by the large ΔT m value of 14°C and the marked increase in viscosity for 5/CT DNA mixtures, dppz appears to present an optimum surface area for side-on intercalation for L=(NH2)2CS. Whereas lower values for these parameters suggest partial intercalation for the smaller dpq ligand of complex 4, the ΔT m value of only 2°C and a decrease in DNA viscosity are in accordance with surface binding for the dppn complex 6. In contrast, replacement of L=(NH2)2CS in 6 by L=(NMe2)2CS in 9leads to very strong intercalative binding of the larger polypyridyl ligand with a binding constant K b =1.0(6)×107 M−1 following a possible change in the DNA structure from B to A, as suggested by CD spectroscopy. Viscosity studies and ΔT m values for complexes 7 and 8 are in accordance with, respectively, partial and strong intercalative binding of these complexes into DNA. Circular dichroism measurements suggest that the presence of the bulky (NMe2)2CS ligand causes significant distortions of the DNA structure for the larger dppz and dppn ligands. [Copyright &y& Elsevier]

Phosphine ligands containing mono- and multiply substituted aromatic substituents (1–13, 19a and 19b) are accessible in high yields by palladium-catalyzed P&z.sbnd;C coupling reactions between primary, secondary or disecondary phosphines and iodo- or bromoaromatic compounds. The reaction is of broad applicability and compatible with electron donor or electron acceptor substituents in ortho, meta or para position to the halogen in the aromatic ring systems. It may be performed in protic and aprotic solvents. The chiral spirocyclic boronato complex 15a is formed upon reaction of 3 with boric acid, while with benzeneboronic acid 15c with a peripheral Lewis acid group is obtained. The Pd-mediated P&z.sbnd;C coupling reaction of primary phosphines proceeds stepwise, tailor-made chiral secondary (16) and tertiary phosphines (17) being formed in high yields. Through combination with Suzuki-type C&z.sbnd;C coupling reactions, the scope of Pd-catalyzed P&z.sbnd;C coupling may be extended further, with novel ligands (20a, 20b, 21a, 21b) with biphenylyl substituents being accessible. The X-ray structures of the salicylic acid derivative 3 (space group P1¯) and of ortho-iso-propylphenyl-diphenylphosphine 6 (space group Pbca) have been determined. [Copyright &y& Elsevier]