Reaction of two equivalents 4-{(3-(pyridine-2-yl) 1H-pyrazole-1-yl}methyl benzonitrile (L1) and 3-{(3-(pyridine-2-yl)1H-pyrazole-1-yl}methyl benzonitrile (L2) with one equivalent of [($\eta^6$-arene)Ru(𝜇- Cl)Cl]₂ and [Cp^∗M(𝜇-Cl)Cl]₂ in methanol yielded mononuclear complexes of the formulae [($\eta^6$-arene)Ru(L1/L2)Cl]BF₄{arene =C₆H₆ (1, 6); C₁₀H₁₄ (2, 7); C₆Me₆ (3, 8)} and [Cp^∗M(L1/L2)Cl]PF₆/BF₄ {Cp^∗= $\eta^5$-C₅Me₅, M=Rh (4, 8); Ir (5, 10)}. These complexes are characterized by IR, ¹H NMR and identities of the structure are established by single crystal XRD studies of some of the representative complexes. It is confirmed from the spectral studies that the nitrile group is not taking part in complexation; instead it remains as a free pendant group only.

The chelating ligands 3-chloro-6-(3-pyridyl-1-pyrazolyl)pyridazine ($pp-Cl$) and 3,6-bis(3-pyridyl-1-pyrazolyl)pyridazine (bppp), were prepared by the condensation of pyridylpyrazole and 3,6-dichloropyridazine. The mononuclear complexes [($\eta^6$-arene)Ru($pp$-Cl)Cl]⁺ $\{\eta^6$-arene = C₆H₆ (1); 𝑝-${}^i$PrC₆H₄Me (2)}, [($\eta^5$-C₅Me₅)M($pp$-Cl)]⁺ {M = Rh (3); Ir (4)}, [($\eta^6$-arene)Ru($bppp$)Cl]⁺ $\{\eta^6$-arene = C₆H₆ (5); 𝑝-${}^i$PrC₆H₄Me (6)}, [($\eta^5$-C₅Me₅)M(bppp)]⁺ {M =Rh (7); Ir (8)} as well as the binuclear complexes [{($\eta^6$-arene)RuCl}₂(bppp)]²⁺ {$\eta^6$ -arene =C₆H₆ (9); 𝑝-$^i$PrC₆H₄Me (10)} and [{($\eta^5$-C₅Me₅)MCl}₂(bppp)]²⁺ {M = Rh (11); Ir (12)} have been synthesized from 3-chloro-6-(3-pyridyl-1-pyrazolyl)pyridazine ($pp-Cl$) or 3,6-bis(3-pyridyl-1-pyrazolyl)pyridazine (bppp) and the corresponding dimers [($\eta^6$-arene)Ru(𝜇-Cl)Cl]₂ and [Cp^∗M(𝜇-Cl)Cl]₂, respectively. All complexes were isolated as their hexafluorophosphate salts and characterized by IR, NMR, mass spectrometry and UV-visible spectroscopy. The molecular structures of [2]PF₆ and [7]PF₆ have been established by single crystal X-ray structure analysis.