Kiran Singhal

Synthesis and some reactions of tris (pentafluorophenyl) antimony compounds

Abstract (C6F5)3Sb has been found to react with interhalogens and halo-pseudohalogens, IX(X = Cl, Br, N3 and NCO), pseudohalogen (SCN), and elemental sulphur to give oxidative addition products (I–VI). (C6F5)3SbS(VI) may also be prepared by the reaction of (C6F5)3SbCl2 with H2S. Metathetical reactions of (C6F5)3SbCl2 with appropriate metallic salts yield covalent pentacoordinate disubstituted products (V, VII–XII) of the general formula, (C6F5)3SbY2 (Y = NCS, NCO, −ONCMe2, −ONCMePh −NCO(CH 2 ) 2 C O and p-NO2C6H4OCO). Treatment of (C6F5)3SbCl2 with aqueous NaN3 gives the binuclear oxo-bridge compound, [(C6F5)3SbOSb(C6F5)3](N3)2·(III) and (IV) are also accessible by displacement reaction of (I) or (II) with the corresponding metallic salt. Molecular weight, conductance measurements, and IR spectra on the new organoantimony(V) derivatives have been obtained. Reductive cleavage reactions of (C6F5)3SbS with hexaaryldileads, Ar6Pb2(Ar = Phenyl, p-tolyl) produce (C6F5)3Sb and the corresponding bis(triaryllead) sulphide but treatment of (C6F5)3SbX2(X = NCO, Cl) with Ar6Pb2 gave Ar4Pb and Ar2PbX2 together with (C6F5)3Sb. (C6F5)3SbCl2 and bis(triorganotin)sulphides undergo exchange of anionic groups.

Synthesis of some novel 2-substituted benzoxazoles as anticancer, antifungal, and antimicrobial agents

Benzoxazole derivatives show various types of biological properties such as antiviral, antineoplastic, anti-HIV-1, antitubercular, anthelmintic, antimicrobial, and antifungal activities. In the last few years 2-substituted benzoxazole derivatives have been studied extensively for their antitumor, antiviral, and antimicrobial activities. In an effort to identify new candidates that may be of value in designing new, potent, selective, and less toxic anticancer, antiviral, and/or antimicrobial agents, we synthesized 2-[(arylhydrazono) cyanomethyl]-5-chloro benzoxazoles (II), 2-[(arylidene)cyanomethyl]-5-halo benzoxazoles (III), and 2-[(cycloalkylidine)cyanomethyl]-5-chlorobenzoxazoles (IV), and tested them for anticancer, antifungal, and antibacterial activities. Some of these (compounds 11, 14) were found to possess anticancer activity and remarkable antifungal as well as antibacterial activities.

On the Lewis acidity of tris(pentafluorophenyl)antimony(V) dichloride towards neutral monodentate O, N and S donor ligands

Abstract Hexa-coordinate neutral adducts (C 6 F 5 ) 3 SbCl 2 ·L( I ) [L=DMSO, DBSO, Ph 3 AsO, Ph 3 PO, DPF, DMF, Py, 3-Pic, TU] and penta-coordinate cationic complexes [(C 6 F 5 ) 3 Sb(Ph 3 AsO) 2 ][ClO 4 ] 2 ( II ) and [(C 6 F 5 ) 3 Sb(bipy)][ClO 4 ] 2 ( III ) have been synthesised. Molecular adducts are monomeric in benzene and non-electrolyte in acetonitrile. IR spectra and conductance measurement suggest the absence of coordination of ClO 4 group to Sb atom in cationic complexes. Spectroscopic data conform to the requirement of octahedral configuration for neural complexes ( I ) and a trigonal bipyramidal structure for complex cations ( II ) and ( III ).

Synthesis of organoantimony(V) and μ-oxy-bis(triarylantimony) selenocyanates using a phase-transfer catalyst

Abstract Several new, pentacoordinated, triorganoantimony bis-selenocyanates [R3Sb(SeCN)2 (R = Me, Ph, p-CH3C6H4, p-ClC6H4, p-F-C6H4 or C6F5)], tetraorganostibonium selenocyanates [R3R′Sb(SeCN) (R = R′ = Ph; R = Ph, and R′ = CH2CHCH2)] and μ-oxy-bis(triarylantimony) bis-selenocyanates {[Ar3SbOSbAr3](SeCN)2 (Ar = Ph, p-CH3C6H4, p-ClC6H4 or p-FC6H4)} have been synthesized from potassium selenocyanate and the corresponding organoantimony halide (chloride and/or bromide) in the presence of the phase-transfer catalyst 18-crown-6, and characterized. Spectroscopic evidence suggested an iso structure (Sb—NCSe). The compounds were also obtained in the absence of 18-crown-6 but in lower yields. Some of these compounds were found to exhibit a significant biological activity.

On the reactivity of less common halopseudohalogens towards metalcarbon- and metalmetal-bonded compounds

Abstract Freshly generated solutions of iodine azide (IN3) and iodine isocyanate (INCO) in acetonitrile or carbon tetrachloride add oxidatively to tertiaryaryl derivatives of group VB elements, Ar3M (Ar = Ph, p-tolyl, p-ClC6H4 or p-FC6H4, and M = As, Sb or Bi) and diaryltellurium(II), Ar2Te (Ar = Ph or p-CH3OC6H4) at −10°C to −5°C to give stable covalent monomeric products, Ar3MIX and Ar2TeIX, respectively (where X = N3 or NCO). The mode of bonding of the pseudohalide group to M has been established by solid-state IR spectra. Ar3MI(N3) failed to react with CS2 but reaction with PhNCY (Y = O or S) gave cyclic tetrazole derivatives. Contrasting behaviour was also observed in the metathetic reaction of Ar2MIX and Ar2TeIX with silver pseudohalides [AgX′ (X′ = NCO or NCS)]. The tetraorgano compounds, R4M (M = Sn or Pb, and R = Ph or p-tolyl), and Bu3SnPh failed to react with IN3 and Bu3SnPhINCO but IN3 cleaved one tin-aryl bond from Ar4Sn in the presence of AlCl3. Addition of IN3 and INCO across the olefinic bond of Ph3SnCH2CHCH2 is preferred to tin-allyl bond cleavage. Reactions of hexaaryldileads with IN3 and INCO under appropriate conditions proceeded with the cleavage of a PbPb bond. Parallel reactions of cyanogen halides (CNI and CNBr) resulted in the formation of corresponding triaryllead halides and pseudohalide derivatives.

Synthesis and Biological Activity of a Novel Compound: (C6F5)2SbPh

A novel organoantimony compound “(C6F5)2SbPh” was synthesized in high yields by modified method and evaluated for insecticidal and antimicrobial activities. The compound was very effective against polyphagous insect pest of crops Spodoptera litura (Lepidoptera: Noctuidae) and polyphagous mite pest of crops Tetranychus urticae (Tetranychidae: Acari). The LC50 value for Spodoptera litura was 0.187 (μ g/insect) and 0.385% respectively in topical application and leaf dip methods. The compound also showed very high antifeedant activity against Spodoptera litura (EC50: 0.155%). The LC50 value against Tetyranychus urticae was 0.021%. Antibacterial activity of the compound (1%) was also tested against human pathogenic bacteria Klebsiella pneumoniae, Staphylococcus aureus, and Pseudomonas aeruginosa showed inhibition zone of 19.78 ± 0.44, 25.49 ± 0.73, and 19.71 ± 0.74 mm, respectively. The minimum inhibitory concentration (MIC) of the novel organoantimony compound against fungi Aspergillus flavus was 125 μ g/mL.

Cycloaddition Reactions of Unsaturated Substrates with a Germanium Nitrogen Bond

Abstract 1,2-Cycloaddition reactions of arylisothiocyanates, ArNCS (Ar-Ph, p -BrPh, p -ClPh, o -CH3Ph and p -CH3Ph), phenylisocyanate and benzonitrile with Ph3GeN3 have been conducted in the absence of solvent under strictly anhydrous conditions to give novel triphanyl-germanium substituted tetrazole derivatives. However, CS2 failed to react with Ph3GeN3 even on prolonged refluxing. A tentative mechanism for the formation of cyclic products has been suggested. The products have been characterized by IR and UV spectra and elemental analysis.

Synthesis And Reactions Of Sterically Hindered α-Naphthyl- And Cyclohexylantimony(V) Derivatives

ABSTRACT Interhalogen and halo-pseudohalogens IX (X=Cl, Br, N3, NCO), (SCN)2, S and TeCl4 add oxidatively to (α-C10H7)3Sb to afford (α-C10H7)3SbIX, (α-C10H7)3 Sb(SCN)2, (α-C10H7)3 SbS and (α-C10H7)3SbCl2, respectively. Reactions of R3SbCl2 (R=α-C10H7, cyclo-C6H11) with MY (M=Ag, K, Na; Y= SCN, CN, NCO, N3) yielded the penta-coordinate products, R3Sb(SCN)2, R3>Sb(NCO)2, (α-C10H7)3Sb(CN)2 and (α-C10 H7)3Sb(N)3)2. The compounds (α-C10H7)3SbIN3, (α-C10H7)3 SbI(NCO), (α-C10H7)3SbI(SCN) and (α-C10H7)3SbI(SeCN) are also accessible by selective replacement reactions of (α-C10H7)3SbICl or (α-C10H7)3SbIBr with the corresponding metal salts. Hydrolysis of R3SbCl2(R=α-C10H7, cyclo-C6>H11) afforded (R3SbCl)2O-type compounds. (α-C10H7)3Sb inserts into the N-chloro bond of N-chlorosuccinimide and N-cholorophthalimide to give and . These haloimides may also be prepared by the interaction of (α-C10H7)3SbCl2 with the corresponding sodium salt of the imido moiety.

Syntheses and Structures of Complex Diorganoantimony(V) Cations of the Type [R2SbL3]3+

Abstract A series of hitherto unreported solid salts of penta‐coordinated cations of the general formula [R2SbL3]3+, where R = C6H5, p‐ClC6H4, p‐CH3C6H4, p‐(CH3O)C6H4; L = DMSO, Ph3AsO, Py‐N‐oxide, DMF, α‐, β‐, and γ‐picoline have been prepared in the presence of tetraphenyl‐ and tetrafluoro‐borate counterions. The complexes have been formulated and characterized on the basis of elemental analyses, molar conductances, molecular weights, and solid state IR and solution state 1H NMR spectral data. The physico‐chemical data are consistent with five‐coordinate antimony complexes.

SYNTHESIS AND CHARACTERISATION OF STERICALLY HINDERED μ-OXYBIS[TRI(α-NAPHTHYL) ANTIMONY(V)] DERIVATIVES

ABSTRACT Several new μ-oxybis[tri(α-naphthyl)antimony(V)] derivatives of the general formula (R3SbL)2O (where R=α-C10H7; L=N3 CN, SCN; ON˭CPh(OH)CHPh, , OOCC6-H4NH2-p, OOCC6H5, OOCC6H4Cl-p, and have been prepared by the interaction of (R3SbCl)2O with the appropriate metal salts of the ligand. (R3SbN3)2O could also be obtained by the interaction of R3SbCl2 with NaN3 (1:2 molar ratio) in ether/water solvent mixture. The newly synthesised complexes have been characterised by elemental analyses, IR spectra, molecular weights and conductance measurements. A trigonal-bipyramidal geometry around the antimony atom with a Sb-O-Sb linkage is tentatively suggested.