Chemistry of a new family of aryl ruthenium species incorporating α-diimine chelation and a pendant imine-phenol function

The reaction of excess 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) with Ru(η2-RL)(PPh3)2(CO)Cl (1) has respectively furnished [Ru(η1-RL)(PPh3)2(CO)(bpy)](PF6) (2) and [Ru(η1-RL)(PPh3)2(CO)(phen)](PF6) (3) in very good yield (η2-RL is C6H2O-2-CHNHC6H4R(p)-3-Me-5, η1-RL is C6H2OH-2-CHNC6H4R(p)-3-Me-5 and R is H, Me, MeO, Cl). The chelation of bpy/phen is attended with the cleavage of RuO and RuCl bonds and iminium-phenolato→imine-phenol prototropic shift. The carbon monoxide ligand is located syn to the phenolic oxygen in 2 and 3 as opposed anti in 1. The crystal and molecular structures of [Ru(η1-HL)(PPh3)2(CO)(bpy)](PF6)·CH2Cl2 (2(H)·CH2Cl2) and [Ru(η1-ClL)(PPh3)2(CO)(phen)](PF6)·H2O (3(Cl)·H2O) are reported. In the lattice of 3(Cl)·H2O, the water molecules form dimers (O⋯O, 2.617(8) Å). In the hydrogen bonded imine-phenol function the N⋯O distance is 2.550(9) Å in 2(H)·CH2Cl2 and 2.581(7) Å in 3(Cl)·H2O. The Rubpy fragment in 2(H)·CH2Cl2 along with the CO ligand and the metallated carbon atom define an equitorial plane from which the metallated aldimine fragment (pendant Ph excluded) is rotated by 39.1° due to interligand repulsion and the two RuP distances (2.384(3) and 2.456(3) Å) become significantly different. The repulsion also counteracts the trans influence of the metallated carbanionic site, the RuN bond trans to the site being shorter. The behaviour of 3(Cl)·H2O is similar. In dichloromethane solution 2 and 3 display a quasireversible RuIII/RuII cyclic voltammetric response with E1/2 in the range 0.75–0.85 V versus SCE. The CO stretch in 2 and 3 is 30–40 cm−1 higher than that in 1 due to the presence of dπ(Ru)–pπ(bpy/phen) back-bonding. The corresponding MLCT absorption (λmax, ∼470 nm) gives rise to fluorescence (λmax, ∼540 nm). The reaction of 2-(2-pyridyl)benzthiazole (pbt) with 1 has furnished [Ru(η1-RL)(PPh3)2(CO)(pbt)](PF6) (8) in which pbt is (N,N) chelated. The properties of 8 are generally similar to those of 2 and 3.