Cyclometalation of benzo[h]quinoline (bzqH) by [RuCl(μ-Cl)(η 6 -C 6 H 6 )] 2 in acetonitrile occurs in a similar way to that of 2-phenylpyridine (phpyH) to afford [Ru(bzq)(MeCN) 4 ]PF 6 (3) in 52% yield. The properties of 3 containing ‘non-flexible’ benzo[h]quinoline were compared with the corresponding [Ru(phpy)(MeCN) 4 ]PF 6 (1) complex with ‘flexible’ 2-phenylpyridine. The [Ru(phpy)(MeCN) 4 ]PF 6 complex is known to react in MeCN solvent with ‘non-flexible’ diimine 1,10-phenanthroline to form [Ru(phpy)(phen)(MeCN) 2 ]PF 6 , being unreactive toward ‘flexible’ 2,2′-bipyridine under the same conditions. In contrast, complex 3 reacts both with phen and bpy in MeCN to form [Ru(bzq)(LL)(MeCN) 2 ]PF 6 {LL=bpy (4) and phen (5)}. Similar reaction of 3 in methanol results in the substitution of all four MeCN ligands to form [Ru(bzq)(LL) 2 ]PF 6 {LL=bpy (6) and phen (7)}. Photosolvolysis of 4 and 5 in MeOH occurs similarly to afford [Ru(bzq)(LL)(MeCN)(MeOH)]PF 6 as a major product. This contrasts with the behavior of [Ru(phpy)(LL)(MeCN) 2 ]PF 6 , which lose one and two MeCN ligands for LL=bpy and phen, respectively. The results reported demonstrate a profound sensitivity of properties of octahedral compounds to the flexibility of cyclometalated ligand. Analogous to the 2-phenylpyridine counterparts, compounds 4–7 are involved in the electron exchange with reduced active site of glucose oxidase from Aspergillus niger. Structure of complexes 4 and 6 was confirmed by X-ray crystallography.