The reaction of [(η⁶-p-cymene)Ru(μCl)₂Cl₂] with functionalized phosphine viz, diphenyl-2-pyridylphosphine yielded complexes of the type: (a) P-bonded complex [(η⁶-p-cymene)RuCl₂(PPh₂Py)] (1), (b) P-, N-chelated complex [(η⁶-p-cymene)RuCl-(PPh₂Py)]BF₄ (2) and [RuCl₂(PPh₂Py)₂] (3) resulting from the displacement of thep-cymene ligand. These complexes were characterized by¹H NMR,³¹P NMR and analytical data. The structures of complexes1 and2 have been confirmed by single crystal X-ray diffraction study. Complex1 crystallised in triclinic space groupP 1 witha = 10.9403 (3) Å,b= 13.3108 (3) Å,c= 10-5394 (10) Å, α=88.943 (2)°, β = 117.193 (2)°, γ= 113.1680 (10)°, Z=2 andV= 1230.39 (5) ų. The complex2 crystallises in monoclinic space group P2₁ witha = 9.1738 (4) Å,b = 14.0650 (6) s, c = 10.7453 (5) Å, β= 106.809 (1)°, Z = 2 andV= 1327.22 (10) ų

The reaction of [{(η⁵-C₅Me₅)M(μ-Cl)Cl}₂] {where M = Rh (1), Ir (2)} with functionalized phosphine viz., diphenyl-2-pyridylphosphine (PPh₂Py) in dichloromethane solvent yield neutral ϰ¹-P-coordinated rhodium and iridium complexes [(η⁵-C₅Me₅)RhCl₂(κ¹-P-PPh₂Py)]3 and [(η⁵-C₅Me₅) IrCl₂(ϰ¹-P-PPh₂Py)]4. Reaction of complexes 1 and 2 with the ligand PPh₂Py in methanol under reflux give bis-substituted complexes such as [(η⁵-C₅Me₅)RhCl(ϰ¹-P-PPh₂Py)₂]⁺5 and [(η⁵-C₅Me₅)IrCl(ϰ¹-P-PPh₂Py)₂]⁺6, whereas stirring in methanol at room temperature gives P-, N-chelating complexes of the type [(η⁵-C₅Me₅)RhCl(ϰ²-P-N-PPh₂Py)]⁺ 7 and [(η⁵-C₅Me₅)IrCl(ϰ²-P-N-PPh₂Py)]⁺8. Neutral ϰ¹-P-coordinated complexes [(η⁵-C₅Me₅)RhCl₂(ϰ¹-P-PPh₂Py)]3 and [(η⁵-C₅Me₅)IrCl₂(ϰ¹-P-PPh₂Py)]4 easily undergo conversion to the cationic P-, N-chelating complexes [(η⁵-C₅Me₅)RhCl(ϰ²-P-N-PPh₂Py)]⁺7 and [(η⁵-C₅Me₅) IrCl(ϰ²-P, N-PPh₂Py)]⁺8 on stirring in methanol at room temperature. These complexes are characterized by FT-IR and FT-NMR spectroscopy as well as analytical methods. The molecular structures of the representative complexes [(η⁵-C₅Me₅)RhCl₂(ϰ¹-P-PPh₂Py)]3, [(η⁵-C₅Me₅)IrCl₂(ϰ¹-P-PPh₂Py)]4 and hexafluorophosphate salt of complex [(η⁵-C₅Me₅)IrCl(ϰ²-P-PPh₂Py)₂]⁺6 are established by single-crystal X-ray diffraction methods

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.

Chelating mono- and di-pyridyl functionalized 𝛽-diketones, viz. 1-phenyl-3-(2-pyridyl) propane-1,3-dione (pppdH) and 1,3-di(2-pyridyl)propane-1,3-dione ($dppdH$) ligands yielded new water soluble $\eta^6$-arene ruthenium(II) complexes of the formulation [($\eta^6$-arene)Ru($\kappa^2$-N-O-pppdH)Cl]⁺ (arene = C₆H₆ 1, p$^i$PrC₆H₄Me 2, C₆Me₆ 3) and [($\eta^6$-arene)₂Ru₂($\kappa^4$-N-O-$dppd$)Cl₂]⁺ (arene = C₆H₆ 4, 𝑝-$^i$PrC₆H₄Me 5, C₆Me₆ 6), as their (complexes 1-4, 6) PF₆ salt or (complex 5) BF₄ salt. The complexes were obtained by treatment of respective precursors, [($\eta^6$-arene)Ru(𝜇-Cl)Cl]₂ (arene = C₆H₆, 𝑝-$^i$PrC₆H₄Me, C₆Me₆) in 1:2 and 1:1 molar ratio with pppdH and $dppdH$ in the presence of NH₄PF₆/NH₄BF₄. All the complexes have been characterized on the basis of FT-IR and NMR spectroscopic data as well as by elemental analysis. Molecular structures of representative complexes 2, 5 and 6 have been confirmed by single crystal X-ray diffraction studies. The `$O-C-C-C-O$' fragment of the coordinated ligand (pppdH) is neutral in complexes 1-3 and that of the $dppdH$ ligand existed as a neutral as well as concomitantly uninegative fashion in complexes 4-6 due to the delocalization of 𝜋-electrons.

The mononuclear compounds [($\eta^6$-arene)Ru(bppm)Cl]PF₆{bppm = 4,6-bis3-(2-pyridyl)-1Hpyrazol-1-yl}pyrimidine; arene = C₆H₆, [1]; 𝑝-$^i$PrC₆H₄Me, [2]; C₆Me₆, [3]}, [CpRu(bppm)(PPh₃)]PF₆{Cp = $\eta^5$-C₅H₅, [4]; $\eta^5$-C₅Me₅, [5]; $\eta^5$-C₉H₇, [6]} and [Cp^∗M(bppm)Cl]PF₆ {M = Rh [7]; Ir [8]} have been synthesized from the reaction of 4,6-bis{3-(2-pyridyl)-1H-pyrazol-1-yl}pyrimidine (bppm) and the corresponding precursor metal complexes [($\eta^6$-arene)Ru(𝜇-Cl)Cl]₂, [CpRu(PPh₃)₂Cl] and [Cp^∗M(𝜇-Cl)Cl]₂, respectively, in the presence of NH₄PF₆. They were characterized by the following techniques viz. IR, NMR, mass spectrometry and UV-visible spectroscopy. The molecular structures of [2] and [7] have been established by single crystal X-ray structure analyses.

Thereaction of [Cp^*M(𝜇-Cl)Cl]₂ (M = Rh, Ir) with 2-aminopyridyl based ligands lead to the formation of mononuclear neutral complexes of general formula [Cp^*MCl₂(L)] {where L1= 2-aminopyridine, L2= 2-amino-3-picoline, L3= 2-amino-3-nirtopyridine, and L4= 2-amino-3-pyridine carboxyaldehyde}. The complexes have been characterized by FT-IR, UV-Vis, $^1$H-$^{13}$C NMR and mass spectroscopic methods. X-ray crystallographic studies of the complexes have shown typical piano-stool geometry around the metal centre in which 2-aminopyridyl ligand acts as an N-monodentate ligand and the amino functionality is not involved in metal coordination. The intra/intermolecular arrangement is due to hydrogen bonding.

A series of Cp*Rh and Cp*Ir complexes of various nitrogen and oxygen donor ligands were synthesized and characterized. Mono, bi and tetradentate ligands were used to synthesize mononuclear and dinuclear complexes. Schiff base derivatives of picolinic hydrazine and 5-aminoquinoline were used in thesynthesis of complexes 1–8. Among the ligands used for complexation, L1 and L2 act as bidentate, L3 as monodentate and L4 as tetradentate in forming the corresponding complexes. All the complexes were characterized by spectroscopic techniques and the structures of complexes 2, 3, 5 and 7 were unambiguouslycharacterized by single crystal X-ray crystallography. Complexes 2 and 7 were found to have π-π stacking interactions and solvent to complex interactions, respectively. Metal-mediated deprotonation of N-H and monodentate binding of nitrogen are attributed to the formation of neutral complexes whereas ionic complexes are formed by (N,O) bonding.

A series of ruthenium, rhodium and iridium complexes with 4-phenyl-1-(pyridin-4yl)methylene thiosemicarbazide (L1) and 4-phenyl-1-(pyridin-4yl)ethylidene thiosemicarbazide (L2) ligands were synthesized and isolated with hexafluorophosphate as a counter ion. All these complexes were fully characterized with the help of FT-IR, UV-Vis, ¹H NMR, ¹³C NMR and elemental analysis. An agar-well diffusion method was employed for evaluation of antibacterial activities against one Gram-positive bacteria Staphylococcusaureus and two Gram-negative bacteria Escherichia coli, Klebsiella pneumoniae. Antimicrobial activity evaluation revealed that Cp^* rhodium complexes has a significant antibacterial activity for all the three strains, Cp^* iridium and p-cymene ruthenium complexes have shown moderated activity against the microorganisms but none of the complexes surpass the activity of their reference drugs. Results indicated that all the complexes reported here inhibit the growth of bacteria.