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Abstract: Structural analysis of a previously reported half-sandwich complex having three-legged “piano-stool” geometry [(η6-C6H6)RuII(L1)Cl][PF6] (1) (L1 = 2-(pyrazol-1-ylmethyl)pyridine) is described. Treatment of 1 with (i) Ag(CF3SO3) in CH3CN and (ii) NaN3 in CH3OH, and (iii) the reaction between [(η6-C6H6)Ru(L2)Cl]-[PF6] (2) (previously reported) and NaCN in C2H5OH led to the isolation of [(η6-C6H6)Ru(L1)(CH3CN)][PF6]2 (3), [(η6-C6H6)Ru(L1)(N3)][PF6] (4), and [(η6-C6H6)Ru(L2)(CN)][PF6] (5), respectively (L2 = 2-(3,5-dimethyl-pyrazol-1-ylmethyl)pyridine). The complex [(η6-C6H6)Ru(L4)Cl][PF6] (6) with a new ligand (L4 = 2-[3-(4-fluorophenyl)pyrazol-1-ylmethyl]pyridine) has also been synthesized. The structures of 3–6 have been elucidated (1H NMR spectra; CD3CN). The molecular structures of 1, 4, and 6·C6H5CH3 have been determined. Notably, the crystal-packing in these structures is governed by C–H⋯X (X = Cl, N) interactions, generating helical architectures. [Copyright &y& Elsevier]

Abstract: A full account of half-sandwich complexes of ruthenium(II) having three-legged “piano-stool” geometry supported by tridentate (2-pyridyl)alkylamine ligands is presented. Reaction of the dimer [{(η6-C6H6)RuCl(μ-Cl)}2] with N-methyl-N,N-bis(2-pyridylmethyl)amine (MeL∗) in CH3OH in the presence of NH4PF6 affords the complex [(η6-C6H6)Ru(MeL∗)][PF6]2 (1). A similar reaction with N-methyl-N,N-bis(2-pyridylethyl)amine (MeL∗∗), however, affords a non-organometallic Ru(III)-dimeric complex (5) (the composition of this complex has been established by physicochemical method). Nucleophilic addition reaction on 1 with NaBH4 leads to the isolation of a cyclohexadienyl complex [(η5-C6H7)Ru(MeL∗)][PF6] (3). The molecular structure of 1 ·2CH3CN, 3, and previously reported cyclohexadienyl complex [(η5-C6H7)Ru(MeL)][PF6] (4) [MeL=N-methyl-[(2-pyridyl)ethyl(2-pyridyl)-methyl]amine], obtained from the reaction between NaBH4 and previously reported “piano-stool” complex [(η6-C6H6)Ru(MeL)][PF6]2 (2), has been confirmed by X-ray crystallography. Solution-state structure of new complexes 1 and 3 has been elucidated by their 1H NMR spectra in CD3CN. The behavior of complex 3 has been investigated with the aid of two-dimensional 1H NMR spectroscopy, as well. An attempt has been made to provide a rationale for the effect of supporting tridentate N-donor ligand [MeL, MeL∗, and MeL∗∗], varying in the chelate ring-size on (i) the relative stability of half-sandwich η6-benzene Ru(II) complexes and (ii) the electrophilicity of Ru(II)-coordinated benzene ring on the nucleophilic addition reactions. [Copyright &y& Elsevier]

Abstract: New series of half-sandwich ruthenium(II) complexes supported by a group of bidentate pyridylpyrazole and pyridylimidazole ligands [(η6-C6H6)Ru(L2)Cl][PF6] (1), [(η6-C6H6)Ru(HL3)Cl][PF6] (2), [(η6-C6H6)Ru(L4)Cl][PF6] (3), and [(η6-C6H6)Ru(HL5)Cl][PF6] (4) [L2, 2-[3-(4-chlorophenyl)pyrazol-1-ylmethyl]pyridine; HL3, 3-(2-pyridyl)pyrazole; L4, 1-benzyl-[3-(2′-pyridyl)]pyrazole; HL5, 2-(1-imidazol-2-yl)pyridine] are reported. The molecular structures of 1–4 both in the solid state by X-ray crystallography and in solution using 1H NMR spectroscopy have been elucidated. Further, the crystal packing in the complexes is stabilized by C–H⋯X (X=Cl and π), N–H⋯Cl, and π–π interactions. [Copyright &y& Elsevier]