Tareq M.A. Al-Shboul

Oxidation products of calcium and strontium bis(diphenylphosphanide).

The tetrahydrofuran adducts [(thf)(4)M(PPh(2))(2)] (M = Ca, Sr) are air sensitive and can easily be oxidized by chalcogens. Metalation of diphenylphosphane oxide, diphenylphosphinic acid, and diphenyldithiophosphinic acid as well as salt metathetical approaches of the potassium salts with MI(2) allow the synthesis of [(thf)(4)Ca(OPPh(2))(2)] (1), [(dmso)(2)Ca(O(2)PPh(2))(2)] (2), [(thf)(3)Ca(O(2)PPh(2))I](2) (3), [(thf)(3)Ca(S(2)PPh(2))(2)] (4), [(thf)(2)Ca(Se(2)PPh(2))(2)] (5), [(thf)(3)Sr(S(2)PPh(2))(2)] (6), [(thf)(3)Sr(Se(2)PPh(2))(2)] (7), and [(thf)(2)Ca(O(2)PPh(2))(S(2)PPh(2))](2) (8), respectively. The diphenylphosphinite anion in 1 contains a phosphorus atom in a trigonal pyramidal environment and binds terminally via the oxygen atom to calcium. The diphenylphosphinate anions act as bridging ligands leading to polymeric structures of calcium bis(diphenylphosphinates). Therefore strong Lewis bases such as dimethylsulfoxide (dmso) are required to recrystallize this complex yielding chain-like 2. The chain structure can also be cut into smaller units by ligands which avoid bridging positions such as iodide and diphenyldithiophosphinate (3 and 8, respectively). In general, diphenyldithio- and -diselenophosphinate anions act as terminal ligands and allow the isolation of mononuclear complexes 4 to 7. In these molecules the alkaline earth metals show coordination numbers of six (5) and seven (4, 6, and 7).

Calcium-mediated Hydrophosphorylation of Organic Isocyanates with Diphenylphosphane Oxide

The calcium-mediated addition of diphenylphosphane oxide to organic isocyanates and isothiocyanates yields N-alkyl and N-aryl substituted diphenylphosphorylformamides (E = O, R = iPr, tBu, cHex, Ph, C6H4-4-Br, C6H2-2,4,6-Me3, and Naph) and -thioformamides (E = S, R = iPr, cHex, Ph, and C6H4-4-Me), respectively, of the type Ph2P(O)–C(E)–N(H)R. All derivatives were characterized by IR and NMR spectroscopy as well as X-ray diffraction experiments. The wavenumbers of the N–H stretching modes are smaller for the thio analogues and N-aryl substituents. In the solid state all formamides and thioformamides form dimers by N–H⋯O–P hydrogen bridges. The P–CCE bonds are significantly elongated compared with the P–CPh distances.

Chemosensor Engineering : Effects of Halogen Attached to Carbon - Carbon Triple Bond Substituent on Absorption Energy of Pyridine : DFT - Study

Pyridine, C5H5N, and pyridine derivatives of the structure C5(S)nH5-nN (S = -C≡C-X; X = F, Cl, Br, I) have been studied theoretically using DFT computation employing the B3LYP/LanL2DZ level of theory. Effects of substituent halogenation on electron density enrichment of the pyridine nitrogen, and thus its effectiveness as an electron donor have been investigated. Computational results showed that the substituent halogenation does affect the charge density accumulation on the nitrogen atom of pyridine as well as the C2=N and -C≡Cbond lengths and the C2 N C6 bond angle. In addition, charge density localization on the nitrogen atom has been found to depend on the number and position of side substituents. Hardness of the halogen atom attached to the tail of the side substituent has been proved to be a determining factor in promoting and qualifying substituted pyridines to act as effective electron donors. The influence of substituent halogenation on electronic localization or delocalization is further viewed by showing (1) charge density distribution surfaces and (2) occupancy of the HOMO molecular orbitals. The conclusions extracted from this investigation support our previous findings in earlier studies through which we attempt to gain more insights toward putting hands on key factors that are anticipated to qualify chelates to be good stabilizers for metal ion complexes that are demanded as chemosensors. Furthermore, this study is considered an important step of progress in our pursued research work that aims to promote inorganic complexes to act as accessible and low energy absorbers. This is essential when inorganic complexes are needed to be employed as colorimertric detectors in the field of chemosensation.

Novel Synthetic Routes to s-Block Metal 2,5-Diphenylphospholides and Crystal Structures of the Bis(tetrahydrofuran) Complexes of the Potassium, Calcium, and Strontium Derivatives

The reduction of 1,4-diphenyl-1,4-bis(diphenylphosphanyl)buta-1,3-diene (1) (1,4-diphenyl- NUPHOS) with potassium in THF yields bis(THF)potassium 2,5-diphenylphospholide (2) which crystallizes with a chain structure. The metathesis reaction of 2 with the iodides of calcium, strontium, and barium leads to the formation of [bis(THF)calcium bis(2,5-diphenylphospholide)] (3), [bis(THF)strontium bis(2,5-diphenylphospholide)] (4), and [bis(THF)barium bis(2,5-diphenylphospholide)] (5). The reaction of M{P(H)SiiPr3}2 with diphenylbutadiyne in THF also leads to the formation of the 2,5-diphenylphospholides of calcium (3), strontium (4), and barium (5). The molecular structures of 2 to 4 are discussed. The environment of the metal atoms is very similar in all these compounds: The metal atoms show an η5 coordination to the phospholide rings forming a bent sandwich complex. The open coordination site is occupied by two THF molecules Graphical Abstract Novel Synthetic Routes to s-Block Metal 2,5-Diphenylphospholides and Crystal Structures of the Bis(tetrahydrofuran) Complexes of the Potassium, Calcium, and Strontium Derivatives

Structure, vibrations and relative stability of 1-methylcyclobutene and methylenecyclobutane tautomers using DFT and CCSD methods

In this study, geometrical optimizations, infrared spectroscopic analysis and relative stabilities of 1-methylcyclobutene and methylenecyclobutane tautomers were investigated by utilizing high-level ab initio and DFT calculations. The thermodynamic data showed that 1-methylcyclobutene is the more stable isomer with enthalpy H∼0.8kcal/mol and Gibbs energy G∼1.3kcal/mol lower than that for methylenecyclobutane at the M06/aug-cc-PVTZ level of theory. These results are in good agreement with the available experimental data. Additionally, the geometrical parameters and vibrational frequencies agree well with the recorded results in literatures.