Kollipara Mohan Rao

Synthesis and characterization of [(Cp*)Ru(PPh3)(N-base)]X and [(η5-C9H7)Ru(PPh3)(N-base)]X complexes: Crystal and molecular structure of the complex [(η5-C9H7)Ru(PPh3)(phen)]PF6 (Cp* = C5Me5, indenyl = C9H7; N-bases = bipy. and phen.; X = BF4 or PF6)

Abstract The reactions of [(η5-Cp*)Ru(PPh3)2(CH3CN)]X (1) and [(η5-indenyl)Ru(PPh3)2(CH3CN)]X (2) (η5-Cp*=η5-C5Me5; η5-indenyl=η5-C9H7; X=BF4 or PF6) with 2,2′-bipyridine (bipy.) and 1,10-phenanthroline (phen.) in benzene or toluene yielded complexes of the type [(η5-Cp*)Ru(PPh3)(L2)]X where L2=bipy, X=BF4 (3) and L2=phen, X=PF6 (4); [(η5-indenyl)Ru(PPh3)2(L2)]X where L2=bipy, X=PF6 (5) and L2=phen, X=PF6 (6). Complex 6 has been established by single crystal X-ray diffraction analysis. Complex 6 crystallizes in the monoclinic space group P 21/c, with a=14.6020 (12), b=12.7100 (17) and c=18.981 (2) A, β=98.982 (9)°, V=3479.5 (7) A3 and Z=4. These complexes can also be prepared from reactions of [(η5-Cp*)Ru(PPh3)2Cl] (7) and [(η5-indenyl)Ru(PPh3)2Cl] (8) with the corresponding ligands in the presence of NH4PF6 or NH4BF4 in toluene. All the complexes were characterized by spectral and analytical data.

Study of half-sandwich mono and dinuclear complexes of platinum group metals containing pyrazolyl pyridine analogues: Synthesis and spectral characterization

AbstractThe 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 [(η6-arene)Ru(pp-Cl)Cl] +  {η6-arene = C6H6 (1); p-iPrC6H4Me (2)}, [(η5-C5Me5)M(pp-Cl)] +  {M = Rh (3); Ir (4)}, [(η6-arene)Ru(bppp)Cl] +  {η6-arene = C6H6 (5); p-iPrC6H4Me (6)}, [(η5-C5Me5)M(bppp)] +  {M =Rh (7); Ir (8)} as well as the binuclear complexes [{(η6-arene)RuCl}2(bppp)]2 +  {η6 -arene =C6H6 (9); p-iPrC6H4Me (10)} and [{(η5-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 [(η6-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. Graphical AbstractThe chelating ligands, 3-chloro-6-(3-pyridyl-1-pyrazolyl)pyridazine (pp-Cl) and 3,6-bis(3-pyridyl-1-pyrazolyl)pyridazine (bppp), were synthesized and their reactions with arene ruthenium, Cp* rhodium and Cp* iridium dimers resulted in the formation of mono and dinuclear complexes. The complexes were characterized by spectral techniques; the structures of representative compounds were confirmed by single crystal X-ray studies.

Hydroxylation of azomethine carbon: isolation of complexes of η5 and η6-cyclic hydrocarbon platinum group metals with a new Schiff-base ligand

A new Schiff base, (pyridin-2-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine, (L), was synthesized. Reaction of [(η6-arene)Ru(µ-Cl)Cl]2 and [Cp*M(µ-Cl)Cl]2 (M = Rh and Ir) with one equivalent of L in the presence of NH4PF6 in methanol yielded dinuclear complexes, [(η6-arene)2Ru2(L-OH)Cl](PF6)2 {arene = C6H6 (1), p-iPrC6H4Me (p-cymene) (2) and C6Me6 (3)}, and [Cp*2M2(L-OH)Cl](PF6)2 [M = Rh (4) and Ir (5)], respectively, leading to the formation of five new chiral complexes with –OH on the azomethine carbon. L is a pentadentate ligand where one of the metal centers is coordinated to two nitrogen atoms in a bidentate chelating fashion while the other metal is bonded tridentate to three nitrogen atoms. Although the ligand is neutral before coordination, after complexation it is anionic (uni-negative) with negative charge on the azo nitrogen {see the structures: N(5) in 2[PF6]2 and N(3) for 4[PF6]2}. The complexes have been characterized by various spectroscopic methods including infrared and 1H NMR and the molecular structures of the representative complexes are established by single-crystal X-ray diffraction studies.

Isolation and spectral studies of water-soluble η 5-cyclichydrocarbon rhodium and iridium complexes with pyridyl diketone analogues bonded through κ 2-N∩O, κ 4–N∩O, and κ3 -N-C-N modes

The reaction of [ M(µ-Cl)Cl]2 (M = Rh, Ir;  = η 5-C5Me5) with 1-phenyl-3-(2-pyridyl)propane-1,3-dione (pppdH) and 1,3-di(2-pyridyl)propane-1,3-dione (dppdH) in 1 : 2 and 1 : 1 molar ratio, respectively, yielded corresponding monomeric complexes [ M(κ 2-N-O-pppdH)Cl]+ [M = Rh (1), Ir (2)] and dimeric complexes [( )2M2(κ 4-N-O-dppd)Cl2]+ [M = Rh (3), Ir (4)]. The treatment of [ Ir(µ-Cl)Cl]2 with dppdH in 1 : 2 molar ratio yielded the activated monomeric complex [ Ir(κ 3-N-C-N-dppd)]+ (5). The formation of a C(sp3)–H is attributed to softer iridium, whereas Rh precursor yielded only the corresponding dimer 3. The formation of these complexes has been established by IR and NMR spectroscopic data and elemental analysis. Molecular structures of 2, 3, and 5 have been confirmed by single-crystal X-ray diffraction. The enolic “O–C–C–C–O” fragment of the coordinated ligand is neutral (κ 2-N-O-pppdH) in monomeric 1 and 2 and neutral as well as concomitantly uninegative (κ 4-N-O-dppd) in dimeric 3 and 4. In C–H-activated monomeric complex 5, the “O–C–C–C–O” fragment is in ketonic form with (κ 3-N-C-N-dppd) bonding of the ligand.

Synthesis, spectral and molecular studies of half-sandwich arene ruthenium and Cp*Rh/Cp*Ir complexes containing bidentate P-N and E–N ligands (E = S, Se) based on diphenyl(2-pyridyl)phosphine

The chalcogenide ligands {E=PPh2Py} (E = O, S, Se) were prepared by direct oxidation of diphenyl(2-pyridyl)phosphine using H2O2, S, and Se powder, respectively. The reaction of ligand with starting metal precursors [(arene)RuCl2]2 {M = Ru, arene = benzene; p-cymene} and [Cp*MCl2]2 (M = Rh, Ir) afforded a series of cationic half-sandwich complexes, [(arene/Cp*)MCl{κ2-(NE)-EPPh2Py)}]+. Reaction of O=PPh2Py with precursors yielded known complexes [(arene/Cp*)MCl{κ2-(PN)-PPh2Py)}]+ instead of expected complexes [(arene/Cp*)MCl{κ2-(NO)-O=PPh2Py)}]+. All new complexes were isolated as counterion and characterized by spectroscopic techniques like FT-IR, NMR, mass, and UV–vis. Some representative complexes were structurally determined by X-ray crystallographic analysis, revealing typical three-legged piano stool geometry around the metal center with a five-membered metallacycle.

Precursor-directed combinatorial biosynthesis of cephalosporin analogue by endolithic actinobacterium Streptomyces sp. AL51 by utilizing thiophene derivative

Natural products or their derivatives provide a reliable resource for new drugs. The multi-step chemical reaction to produce new drug is not only expensive but also release pollutants. The precursor-based combinatorial biosynthesis (PCB) is, however, a better option to produce novel natural products with potential pharmaceutical applications. The present work is an attempt to synthesize an antibacterial compound by transforming thiophene precursor using endolithic Streptomyces sp. AL51. The Streptomyces sp. AL51 was isolated from a granite rock sample collected from Mylliem, Meghalaya, India. The isolate was identified as Streptomyces sp. based on its cultural, morphological, biochemical and molecular characteristics. The bioactive compound CAx1 was extracted from the fermentation broth. The compound was characterized by bioactivity-guided fractionation and identified by infrared, UV–visible, nuclear magnetic resonance and mass spectrometry data and identified as 7-[1-(thiophene-5-yl)-1-formamido]-3-propylenyl-3-cephem-4-carboxylic acid with molecular formula C15H14N2O4S2. The purified compound showed considerable in vitro antibacterial activity against both Gram-positive and Gram-negative bacteria showing its broad spectrum property. The obtained results provide promising baseline information for the potential use of endolithic actinobacterium for semisynthetic drug discovery. This is the first report on PCB of broad range antibacterial compound by endolithic Streptomyces strain.

Synthesis and characterization of [(Cp*)Ru(PPh3)(N-base)]X and [(η5-C9H7)Ru(PPh3)(N-base)]X complexes: crystal and molecular structure of the complex [(η5-C9H7)Ru(PPh3)(phen)]PF6

Abstract The reactions of [(η5-Cp*)Ru(PPh3)2(CH3CN)]X (1) and [(η5-indenyl)Ru(PPh3)2(CH3CN)]X (2) (η5-Cp*=η5-C5Me5; η5-indenyl=η5-C9H7; X=BF4 or PF6) with 2,2′-bipyridine (bipy.) and 1,10-phenanthroline (phen.) in benzene or toluene yielded complexes of the type [(η5-Cp*)Ru(PPh3)(L2)]X where L2=bipy, X=BF4 (3) and L2=phen, X=PF6 (4); [(η5-indenyl)Ru(PPh3)2(L2)]X where L2=bipy, X=PF6 (5) and L2=phen, X=PF6 (6). Complex 6 has been established by single crystal X-ray diffraction analysis. Complex 6 crystallizes in the monoclinic space group P 21/c, with a=14.6020 (12), b=12.7100 (17) and c=18.981 (2) A, β=98.982 (9)°, V=3479.5 (7) A3 and Z=4. These complexes can also be prepared from reactions of [(η5-Cp*)Ru(PPh3)2Cl] (7) and [(η5-indenyl)Ru(PPh3)2Cl] (8) with the corresponding ligands in the presence of NH4PF6 or NH4BF4 in toluene. All the complexes were characterized by spectral and analytical data.

Synthesis and characterization of [(Cp*)Ru(PPh 3 )(N-base)]X and [(η 5 -C 9 H 7 )Ru(PPh 3 )(N-base)]X complexes: crystal and molecular structure of the complex [(η 5 -C 9 H 7 )Ru(PPh 3 )(phen)]PF 6 : (Cp*=C5Me5, indenyl=C9H7; N-bases=bipy. and phen.; X=BF4 or PF6)

Abstract The reactions of [(η5-Cp*)Ru(PPh3)2(CH3CN)]X (1) and [(η5-indenyl)Ru(PPh3)2(CH3CN)]X (2) (η5-Cp*=η5-C5Me5; η5-indenyl=η5-C9H7; X=BF4 or PF6) with 2,2′-bipyridine (bipy.) and 1,10-phenanthroline (phen.) in benzene or toluene yielded complexes of the type [(η5-Cp*)Ru(PPh3)(L2)]X where L2=bipy, X=BF4 (3) and L2=phen, X=PF6 (4); [(η5-indenyl)Ru(PPh3)2(L2)]X where L2=bipy, X=PF6 (5) and L2=phen, X=PF6 (6). Complex 6 has been established by single crystal X-ray diffraction analysis. Complex 6 crystallizes in the monoclinic space group P 21/c, with a=14.6020 (12), b=12.7100 (17) and c=18.981 (2) A, β=98.982 (9)°, V=3479.5 (7) A3 and Z=4. These complexes can also be prepared from reactions of [(η5-Cp*)Ru(PPh3)2Cl] (7) and [(η5-indenyl)Ru(PPh3)2Cl] (8) with the corresponding ligands in the presence of NH4PF6 or NH4BF4 in toluene. All the complexes were characterized by spectral and analytical data.