Main Group Chemistry

During large-scale preparations of 2,6-dimesitylbenzoic acid, Mes₂ArCO₂H (Mes = 2,4,6-trimethylphenyl), a highly insoluble by-product precipitated and was isolated. The material formed in modest yield but significantly impacted the preparation of Mes₂ArCO₂H. The isolated product could be dissolved, with difficulty, in acetone, THF or pyridine. Crystallization under the evaporating solvents resulted in the isolation of three new compounds in relatively low yield. From pyridine the compound [Mes₂ArCO₂Li(H₂O)(py)]₂ was recovered. Recrystallization from THF gave (Mes₂ArCO₂H)(Mes₂ArCO₂)Li(THF)₂, which has been shown to contain both neutral (benzoic acid) and anionic (benzoate) ligands. Finally, crystals of [Mes₂ArCO₂(H₂O)Li(μ-OH₂)(μ-O₂CMes₂Ar)Li(H₂O)]₂·2H₂O were isolated from the acetone solution. These new solids were characterized using single crystal X-ray structural determinations.

A novel energetic cesium compound based on trinitroresorein, [Cs₂(HTNR)(OH)(H₂O)]_n (H₂TNR: 2,4,6-trinitroresorcinol) has been synthesized by the reaction of cesium nitrate and styphnic acid. The molecular structure was characterized by using X-ray diffraction analysis, elemental analysis and FT-IR analysis. The crystalline material is monoclinic with space group P2(1)/c and the empirical formula is Cs₂C₆H₅N₃O₁₀. The unit cell parameters are: a = 6.843(1) Å, b = 10.185(2) Å, c = 19.026(4) Å, β = 96.21(1)°, V = 1318.21(40) ų, Z = 4, D_c = 2.746 Mg/m³, M_r = 544.95, F(000) = 1008, μ(Mo K_α) = 5.588 mm⁻¹. The thermal decomposition mechanism of the compound was studied by differential scanning calorimetry (DSC) and thermo-gravimetric derivative (TG-DTG) techniques. At the linear heating rate of 10°C/min, the thermal decomposition of the compound finally evolved CsCN and other gas products, which indicated three decomposition processes between 60 and 500°C.

The kinetics of oxidation of a loop diuretic drug furosemide (Fur) by diperiodatoargentate(III) (DPA) has been investigated spectrophotometrically in alkaline medium at a constant ionic strength of 0.20 mol dm⁻³. The stoichiometry was 1 : 2 (Fur: DPA). The order of the reaction with respect to [DPA] was unity while the order with respect to [Fur] was less than unity over the concentration range studied. The rate increased with increase in [OH⁻] and decreased with increase in [IO₄⁻]. The oxidation products were identified as 2-(4-carboxy-2-oxo-but-3-enylamino)-4-chloro-5-sulfamoyl-benzoic acid and Ag(I). The reaction constants involved in the different steps of the reaction mechanism were calculated. Kinetic experiments suggest that [Ag(H₂IO₆)(H₂O)₂] is the reactive silver(III) species.

A series of novel Schiff bases derived from 2-oxo-quinoline-3-carbaldehyde with ortho-phenylene diamine (o-phen) and nitro-ortho-phenylene diamine (nitro-o-phen) and its corresponding transition metal complexes were synthesized, characterized by elemental analysis, spectral (IR, ¹H-NMR, Mass, UV-Vis, Fluorescence, ESR and TGA) and magnetic studies. The results were found that all the metal complexes possess octahedral geometry. The measured molar conductance values in DMF solution indicates that the complexes are non-electrolytic in nature. The redox behavior of metal complexes are investigated by using cyclic voltammetry. Furthermore, Schiff bases and their metal complexes have been screened for antibacterial and antifungal activities by MIC method. The DNA cleavage studies showed the cleavage of DNA by the agarose gel electrophoresis method.

The reactions of Bi(NO₃)₃·5H₂O with 11-mercaptoundecanoic acid, L-cysteine, DL-homocysteine, DL-penicillamine and L-glutathione under 1 : 1, 1 : 2, and 1 : 3 mole ratios in the presence of variable amounts of triethylamine were studied. The compounds RS-Bi(NO₃)₂ were unstable either releasing NO₂ or by expelling one NO₃⁻ gave cyclic or polymeric products. The compounds (RS)₂Bi(NO₃) were obtained in the presence of two Et₃N but with three Et₃N removal of the NO₃⁻ lead to polymeric products. The trithiolates were obtained with a 3 : 1 : 3 stoichiometry. A notable exception was the behaviour of DL-penicillamine which gave other than the expected products. The di- and trithiolates are kinetically labile and can add or remove, respectively, thiols. These findings may have biochemical implications when Bi(III) is in a cell.

The reaction of para-substituted thiophenols with Bi(NO₃)₃ċ5H₂O and BiO(NO₃)ċH₂O was studied. The nitrate was more reactive than the subnitrate, and was a convenient bismuth compound for the preparation of trithiolates, Bi(SAr)₃. Thiols having electron withdrawing groups seem to be more reactive than those with electron donating groups. The thiolato groups in Bi(SAr)₃ can migrate to Bi(NO₃)₃ċ5H₂O thus giving (ArS)₂Bi(NO₃), but the monothiolate product, ArS-Bi(NO₃)₂, decomposed evolving NO₂. Bi(III) complexes with some aromatic thiols of probable biochemical interest are also described.

Some new indium compounds of bifunctional tridentate Schiff bases have been synthesized by the reactions of In(OPrⁱ)₃ with corresponding ligands in 1 : 2 molar ratio in refluxing benzene. Equimolar reactions of these mononuclear indium compounds with B(OPrⁱ)₃ yield heterodinuclear compounds. These newly synthesized compounds have been characterized by elemental analyses and molecular weight measurements. Their plausible structures have been proposed on the basis of IR and NMR (¹H, ¹³C, ¹¹B) and FAB-Mass spectral studies. Antibacterial activities of Schiff base ligands and their corresponding mononuclear compounds have been screened against gram positive E. coli and gram negative Pseudomonas with promising results.

The reaction of Cp₂ZrCl₂ with LiP(H)B(Ni-Pr₂)₂ • DME in a 1 : 2 ratio provides the metallodiphosphane Cp₂Zr[P(H)B(Ni-Pr₂)₂]₂ (5). Combination of 5 with Mo(CO)₄(norbornadiene) gives the diphosphane adduct Cp₂Zr[P(H)B{}(Ni-Pr₂)₂] ₂Mo(CO)₄ (7) in which 5 acts as a bidentate chelating ligand. The reaction of 5 with n-BuLi in a 1 : 1 ratio generates a phosphane-phosphide “ate” complex Li{Cp₂Zr[P(H)B(Ni-Pr₂)₂][PB(Ni-Pr₂)₂]} • DME (8). This unusual complex contains a planar, asymmetric ZrPLiP ring. The compounds have been characterized by spectroscopic methods and the molecular structures of 7 and 8 have been determined by X-ray diffraction methods.