• MOHAN RAO KOLLIPARA

      Articles written in Journal of Chemical Sciences

    • Study of reactivity ofp-cymene ruthenium(II) dimer towards diphenyl-2-pyridylphosphine: Synthesis, characterization and molecular structures of [(η6-p-cymene)RuCl2(PPh2Py)] and [(η6-p-cymene)RuCl(PPh2Py)]BF4

      R Lalrempuia Patrick J Carroll Mohan Rao Kollipara

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      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) Å3. 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) Å3

    • Substitution reactions of diphenyl-2-pyridylphosphine with [(η5-C5Me5)M(μ-Cl)Cl]2 (M = Rh or Ir) dimers: Isolation of mono–, di– and chelating complexes

      Padavattan Govindaswamy Patrick J Carroll Yurij A Mozharivskyj Mohan Rao Kollipara

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      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)RhCl21-P-PPh2Py)]3 and [(η5-C5Me5) IrCl21-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)RhCl21-P-PPh2Py)]3 and [(η5-C5Me5)IrCl21-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)RhCl21-P-PPh2Py)]3, [(η5-C5Me5)IrCl21-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

    • $\eta^5$ and $\eta^6$ - cyclic 𝜋-perimeter hydrocarbon platinum group metal complexes of 3-(2-pyridyl)pyrazole derived ligands with a pendant nitrile group: Syntheses, spectral and structural studies

      Gloria Sairem Venkateswara Rao Anna Peng Wang Bbulal Das Mohan Rao Kollipara

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      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 [CpM(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 [CpM(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.

    • Study of $\eta^6$- cyclic 𝜋-perimeter hydrocarbon ruthenium complexes bearing functionalized pyridyl diketones: Isolation of complexes with $\kappa^2$-N∩O and $\kappa^4$-N∩O bonding modes of ligands

      Saphidabha L Nongbri Babulal Das Mohan Rao Kollipara

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      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.

    • Synthesis and structural study of platinum group metal complexes containing pyrimidine bridged pyrazolyl-pyridine ligand and $\eta^5$ and $\eta^6$ - cyclic hydrocarbons

      Thirumala Prasad Kota Mohan Rao Kollipara

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      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 [CpM(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 [CpM(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.

    • Half-sandwich pentamethylcyclopentadienyl group 9 metal complexes of 2-aminopyridyl ligands: Synthesis, spectral and molecular study

      Mahesh Kalidasan Scott Forbes Yurij Mozharivskyj Mohan Rao Kollipara

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      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.

    • Synthesis and structural studies of half-sandwich Cp* rhodium and Cp* iridium complexes featuring mono, bi and tetradentate nitrogen and oxygen donor ligands

      NARASINGA RAO PALEPU WERNER KAMINSKY MOHAN RAO KOLLIPARA

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      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.

    • Half-sandwich arene ruthenium, rhodium and iridium thiosemicarbazone complexes: synthesis, characterization and biological evaluation

      AGREEDA LAPASAM VENKANNA BANOTHU UMA ADDEPALLY MOHAN RAO KOLLIPARA

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      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.

    • Ruthenium, rhodium and iridium complexes containing diazafluorene derivative ligands: synthesis and biological studies

      CARLEY GIFFERT L NONGPIUR DEEPAK KUMAR TRIPATHI KRISHNA MOHAN POLURI HEMANT RAWAT MOHAN RAO KOLLIPARA

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      Reaction of [(arene)MCl2]2 with bidentate 4, 5-diazafluorene-9-one (dafo) and derived Schiff base ligands (L1–L3) in the presence of ammonium hexafluorophosphate yielded mononuclear cationic complexes having general formula [(arene)MLCl]PF6 {M = Ru, arene = benzene (1, 5, 9); M = Ru, arene = p-cymene (4, 8); M = Rh, arene = Cp* (2, 6, 10); M = Ir, arene = Cp* (3, 7, 11); L = 4, 5-diazafluorene-9-one(L1), N-(4, 5-diazafluoren-9-ylidene)aniline (L2), N-(4, 5-diazafluoren-9-ylidene)phenyl hydrazine (L3)}.All these complexes were isolated as hexafluorophosphate salts and characterized by spectral and analyticaltechniques such as FT-IR, UV-vis, NMR spectroscopy and ESI-Mass spectrometry. Complexes 1-3 werecharacterized by X-ray crystallographic studies, which indicated NN0 bidentate coordination of the ligandsthrough pyridine nitrogen atoms of the ligand. To evaluate the biological properties of these complexes,antibacterial and antioxidant experiments have been carried out. The complexes 8, 9 and 11 exhibitedantibacterial activity against Gram-positive bacteria. Results also show that the compounds possess prominentantioxidant activity against DPPH radicals.

      The reaction of [(arene)MCl2]2 with 4, 5- diazafluorene-9-one (dafo) and derived Schiff-base ligands yielded mononuclear cationic complexes having the general formula [(arene)MLCl]PF6-. Some of the complexes exhibited antibacterial activity against Gram-positive bacteria. Results also show that the compounds possess prominent antioxidant activity against DPPH radicals.

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