Formation of BH3 Adducts with Pyridine-2-Methylaminophosphine ligands: An experimental and computational study

The reaction of pyridine-2-methylaminophosphine [C5H4N-CH2NHPPh2] (1) and pyridine-2-methylphosphinoselenoic amide [C5H4N-CH2NHP(Se)Ph2] (2) with BH3⋅SMe2 yields the corresponding adducts [C5H4N(BH3)-CH2NHP(BH3)Ph2] (1a), and [C5H4N(BH3)-CH2NHP(Se)Ph2] (2a), respectively. The solid state structures of both the compounds were established by single crystal X-ray diffraction analysis. The phosphorus and the pyridine nitrogen atoms are coordinated to the boron atom in the case of 1a whereas only pyridine nitrogen atom is attached to the BH3 group in the case of 2a. To understand the nature of P-B/ N-B bonds and to compare the basicities of pyridine nitrogen, amino nitrogen and phosphorus atoms, density functional theoretical (DFT) calculations were performed on the BH3 adducts 1a and 2a. The results are consistent with the experimental results

Structural and Mechanistic Insights of Substituted Perimidine - Experimental and Computational Studies

We report here the synthesis of phenyl(2 - phenyl - 2,3 - dihydro - 1H - perimidin - 2 - yl)methanone ( 2 ) by the condensation reaction between 1,8 - diaminonaphthalene ( 1 ) and benzil in equimolar ratio at ambient temperature. Further reaction of compound 2 with one equivalent of sodium borohydride at 0 ºC resulted in quantitative conversion of ketone to corresponding alcohol, namely, phenyl(2 - phenyl - 2,3 - dihydro - 1H - perimidin - 2 - yl)methanol ( 3 ). The solid - state structures of both the compounds were established using single - crystal X - ray diffraction analysis. We probed, using quantum mechanics, the mechanism of formation of compound 2 through two of the most plausible routes and observed that it was more plausible that the first route, energy - wise, would result in product 2 . We also calculated the stabilization energy of intermolecular hydrogen bond ing, which leads to the formation of a dimer, which has already been observed in the solid - state structure of compound 3

Heavier Group 2 Metal Complexes with Flexible Scorpionate Ligand based on 2-Mercaptopyridine

We report the synthesis of novel alkaline earth metal complexes [2-SS-(Bmp)2M(THF)n] [M = Ca (2), Sr (3) n = 2; M = Ba (4), n = 3] of flexible dihydrobis(2-thiopyridone)borate (Bmp) ligand based on 2-mercaptopyridine. Complexes 2–4 were isolated in good yield by the reaction between sodium dihydrobis(2-thiopyridone)borate, [{(Bmp)Na(THF)}2]n (1) and corresponding alkaline earth metal diiodides in toluene at ambient temperature. The solid-state structures of strontium and barium complexes, complexes 3 and 4 respectively, were established using single-crystal X-ray diffraction analysis. The solid-state structure of sodium complex 1 was also confirmed using X-ray. The solid-state structures of complexes 3 and 4 revealed that the Bmp ligand coordinates through sulphur atoms to the metal ions in 2 fashion. The strontium ion is attached symmetrically and the barium ion is asymmetrically linked with the Bmp ligand, manifesting the 2-thiopyridone and pyridine-2-thiolate tautomeric form of the Bmp ligand. The strontium ion in complex 3 adopts a distorted octahedral geometry whereas the geometry around the barium ion can best be described as a distorted pentagonal bipyramidal. Both complexes 3 and 4 also have short B...H...M interaction due to the presence of BH2 group in the ligand. In the solid state, sodium complex 1 is polymeric in nature and in the asymmetric unit each sodium ion is bonded to two sulphur atoms through and modes. The adjacent BH2 group is also linked with each sodium ion through hydrogen atoms via 2 and

Modelling of Transition State in Grignard Reaction of Rigid N-(Aryl)imino-Acenapthenone (Ar-BIAO): A Combined Experimental and Computational Study

We present a combined synthetic and computational study on the addition of Grignard reagents RMgBr/RMgI (R = Me, Et) to various sterically rigid N-(aryl)imino-acenapthenone (Ar-BIAO) (Ar = 2,6-iPr2C6H3 (1), 2,6-Me2C6H3 (2), and 2,4,6-Me3C6H2 (3) ligands). In the experimental method, when compounds 1–3 were treated with RMgBr (R = Me, Et) at room temperature, the corresponding racemic N-(aryl)imino-acenapthylene-1-ol (Ar-BIAOH) compounds (Ar = 2,6- iPr2C6H3, R = Me (1a), Et (1b); Ar = 2,6-Me2C6H3, R = Me (2a), Et (2b); and Ar = 2,4,6-Me3C6H2, R = Me (3a), Et (3b)) were obtained in yields up to 82 %. The Ar-BIAOH compounds were characterized by spectroscopic and combustion analyses. The solid state structures of compounds 1a–3a were established by single-crystal X-ray diffraction analysis. To model the transition state of the Grignard reaction with asymmetrical and sterically rigid Ar-BIAO ligands having three fused rings containing exo-cyclic carbonyl and imine functionalities, we carried out computational analysis. During our study, we have considered the gas phase addition of CH3MgBr to 2 and the model system of 2-(methylimino)pentanone (2′). We have carried out ab initio (HF/3–21G*) and density functional theory calculations with the hybrid density functional B3LYP/6–311+G(2d,p) to probe two major aspects: (1) the stability of an intra-molecular chelation involving magnesium, carbonyl oxygen, and imine nitrogen and (2) to suggest a probable transition state and a mechanistic pathway. The computational investigation suggests the formation of a tetra-coordinated magnesium complex as the transition state for the Grignard reaction

Hydroboration, Cyanosilylation, and Sequential Cyanosilylation-Hydroboration of Carbonyl Compounds using Ti(IV) Amido Complex as an Efficient Catalyst

Catalytic hydroboration using pinacolborane (4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane) and cyanosilylation using trimethylsilyl cyanide of a wide range of aldehydes and ketones in the presence of titanium (IV) complexes [2‐{(C5H4N)CH2N‐P(=Se)Ph2}Ti(NMe2)3] (1) and [{2‐(C6H4F)NP(=Se)Ph2}Ti(NMe2)3] (2) are reported. The catalytic hydroboration and cyanosilylation processes are high‐yielding, general, and result in efficient conversion of carbonyl compounds to corresponding products under mild conditions. Titanium catalyst 1 exhibits high tolerance toward several functional groups. First‐order kinetics with respect to the catalyst and each of the substrates was observed for the titanium‐catalyzed hydroboration reaction of carbonyl compounds. First principles' calculations were performed to explore the catalytic hydroboration reaction mechanism. In addition, a combination of both reactions and sequential cyanosilylation‐hydroboration was reported. Ti(IV) complexes 1 and 2 were prepared by the aminolysis reaction of [Ti(NMe2)4] with protic ligands [(C5H4N)CH2NHP(=Se)Ph2] (L1H) and [(C6H4F)NHP(=Se)Ph2] (L2H) respectively. The third titanium complex [4‐{(Ph2P(=Se)NCH(C5H4N)CH(C5H4N)‐P(=Se)Ph2}Ti(NMe2)2] (3) was obtained by the reaction of [Ti(NMe2)4] and ligand L1H in a 1:2 molar ratio at room temperature. Molecular structures of complexes 1 and 3 in the solid state are reported

N-versus P-co-ordination for N-B and P-B bonded BH3 adducts for various phosphinamine ligands - An experimental and computational study

The reaction between phosphinamines [Ph2PNH(CHPh2)] (1), [Ph2PNH(CPh3)] (2) [Ph2PNH(CMe 3)] (3), [Ph2PNH(2,6-Me2C6H 3)] (4), and [Ph2PNH(2,6-iPr2C 6H3)] (5) with BH3.SMe2 yields corresponding adduct [Ph2P(BH3)NH(CHPh2)] (1a), [Ph2P(BH3)NH(CPh3)] (2a), [Ph 2P(BH3)NH(CMe3)] (3a), [Ph2P(BH 3)NH(2,6- Me2C6H3)] (4a), and [Ph2P(BH3)NH(2,6-iPr2C 6H3)] (5a) respectively. The solid state structures of all the compounds were established by single crystal X-ray diffraction analysis and in the solid state, all the compounds reveal that the phosphorus atom is preferably coordinated to the boron atom. Density functional theory (DFT) based electronic structure calculations were carried out taking various model phosphinamines to react with borane to establish the fact that the basicity of nitrogen atom adjacent to phosphorus in phosphinamines is reduced and thereby least preferred for coordination with boran

Unprecedented calcium metalla-macrocycle having phosphinoselenoic amide and diphenylphosphinate in the coordination sphere

An eight-membered calcium metalla-macrocycle of the composition [Ca{Ph 2P(Se)N(Ar)}{Ph2P(O)O}(THF)2]2 (2) (Ar = 2, 6-dimethylphenyl) can be isolated with a good yield by the reaction of neutral phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) and calcium bis(trimethylsilyl)amides [Ca{N(SiMe3)2} 2(THF)2] in toluene followed by crystallization in air. The homoleptic calcium phosphinoselenoic amido complex of the composition [Ca{Ph2P(Se)N(Ar)}2(THF)2] (3) can also be obtained through two synthetic routes. In the first route, [Ca{N(SiMe 3)2}2(THF)2] is treated with phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) at an ambient temperature followed by re-crystallization in an inert atmosphere to give complex 3 of high purity. In the second route, a one-pot reaction is carried out involving 1, calcium diiodide, CaI2, and potassium bis(trimethylsilyl)amide [K{N(SiMe3)2}] in toluene in an inert atmosphere. When complex 3 is treated with diphenylphosphinic acid in THF, compound 2 is also obtained with a good yield. Both complexes are confirmed using single-crystal X-ray diffraction analysis. The solid-state structure of complex 2 reveals an eight-membered macrocycle formed by two diphenylphosphinate groups and two calcium ions. In addition, a four-membered calcium metallacycle around each calcium atom is formed by the phosphinoselenoic amido ligand through coordination between the nitrogen and selenium atoms. In complex 3, the calcium atom is coordinated by two phosphinoselenoic amido groups and a direct metal selenium bond is observe

A comprehensive study of the estuary sea environment in the Bay of Bengal, near the Mahanadi River confluence

Abstract This study focuses on the environmental conditions of the Mahanadi Estuary near Paradeep Harbor and the adjacent sea. Data collected from May 2013 to April 2020 from 32 GPS fixed stations was analyzed to assess the water quality in different zones (estuarine, mixed zone, mixed zone south, and mixed zone north) of study area. Parameters such as pH, SST, TSS, nitrite, phosphate, silicate, TOC, chlorophyll, fecal coliform, and heavy metals were used to estimate the Water Quality Index (WQI) for each zone. The study found a deterioration (> 30%) in the overall water quality of the Mahanadi Estuary from 2013 to 2020, potentially attributed to river inflows, port activities, and industrial outflows in to the coastal ecosystem. Seasonal variations in temperature, salinity, turbidity, nitrite, nitrate, and ammonia were observed. The water quality showed a deteriorating trend in estuarine, mixed zone, mixed zone south, and mixed zone north. Based on the water quality indices, the ecosystem shows moderate levels of stress. The degraded water quality highlights the need for a targeted mitigation plan to reduce external pressures and enhance the overall ecosystem quality. Graphical Abstrac

International Nosocomial Infection Control Consortiu (INICC) report, data summary of 43 countries for 2007-2012. Device-associated module

We report the results of an International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2007-December 2012 in 503 intensive care units (ICUs) in Latin America, Asia, Africa, and Europe. During the 6-year study using the Centers for Disease Control and Prevention's (CDC) U.S. National Healthcare Safety Network (NHSN) definitions for device-associated health care–associated infection (DA-HAI), we collected prospective data from 605,310 patients hospitalized in the INICC's ICUs for an aggregate of 3,338,396 days. Although device utilization in the INICC's ICUs was similar to that reported from ICUs in the U.S. in the CDC's NHSN, rates of device-associated nosocomial infection were higher in the ICUs of the INICC hospitals: the pooled rate of central line–associated bloodstream infection in the INICC's ICUs, 4.9 per 1,000 central line days, is nearly 5-fold higher than the 0.9 per 1,000 central line days reported from comparable U.S. ICUs. The overall rate of ventilator-associated pneumonia was also higher (16.8 vs 1.1 per 1,000 ventilator days) as was the rate of catheter-associated urinary tract infection (5.5 vs 1.3 per 1,000 catheter days). Frequencies of resistance of Pseudomonas isolates to amikacin (42.8% vs 10%) and imipenem (42.4% vs 26.1%) and Klebsiella pneumoniae isolates to ceftazidime (71.2% vs 28.8%) and imipenem (19.6% vs 12.8%) were also higher in the INICC's ICUs compared with the ICUs of the CDC's NHSN