Raju Ratnani

Synthesis, spectroscopic and structural aspects of some tetraorganodistannoxanes with internally functionalized oxime: crystal and molecular structures of [{R2Sn(ONC(Me)py)}2O]2 (R=Bun and Et) and 2-NC5H4C(Me)NOH

Diorganotin(IV) complexes of the type [{R2Sn(ON=C(Me)py)}(2)O](2)(R = Bu-n(1), Pr-n(2), Et (3) and Me (4)) have been synthesized by the condensation reaction of R2SnO with 2-NC5H4(Me)C=NOH (5) in 1:1 molar ratio in refluxing anhydrous benzene-toluene and characterized by elemental analyses and IR and NMR (H-1, C-13 and Sn-119) spectroscopy. Two sets of Sn-119 chemical shifts are observed in the Sn-119-NMR spectra of all of these compounds indicating the presence of two types of environment around the tin atoms in solution. The crystal structures of 1, 3 and 5 have been established by single crystal X-ray diffraction, The bonding in 1 differs from that in 3 but in both structures two different environments around the tin atoms are evident with the geometry around each tin atom being that of a distorted trigonal bipyramid with alkyl groups at the equatorial positions. The structure of 5 consists of chains of molecules arising from intermolecular hydrogen bonding involving the nitrogen atom of the ring.

Structural and optical studies of local disorder sensitivity in natural organic–inorganic self-assembled semiconductors

The structural and optical spectra of two related lead iodide (PbI) based self-assembled hybrid organic‐inorganic semiconductors are compared. During the synthesis, depending on the bridging of organic moiety intercalated between the PbI two-dimensional planes, different crystal structures are produced. These entirely different networks show different structural and optical features, including excitonic bandgaps. In particular, the modified organic environment of the excitons is sensitive to the local disorder both in single crystal and thin film forms. Such information is vital for incorporating these semiconductors into photonic device architectures. (Some figures in this article are in colour only in the electronic version)

Synthesis, characterisation and structures of thio-, seleno- and telluro-ether complexes of gallium(III)

The reactions of GaX3 (X = Cl, Br or I) with SMe2, SeMe2 and TeMe2 (L) in non-coordinating solvents produces only the pseudo-tetrahedral [GaX3L], which have been characterised by IR, Raman and multinuclear NMR (1H, 71Ga, 77Se or 125Te) spectroscopy, and by the crystal structure of [GaCl3(SeMe2)]. The 71Ga NMR resonances show small low frequency shifts for fixed halides as the neutral donors change from S --> Se --> Te. Bidentate ligands including MeS(CH2)2SMe, PhS(CH2)2SPh, MeSe(CH2)2SeMe, nBuSe(CH2)2Se(n)Bu and MeTe(CH2)3TeMe (L-L) also produce complexes with 4-coordinate gallium centres, [(GaX3)2(mu-L-L)], confirmed by the crystal structures of [(GaI3)2(mu-MeS(CH2)2SMe)], [(GaCl3)2(mu-PhS(CH2)2SPh)] and [(GaCl3)2(mu-nBuSe(CH2)2Se(n)Bu)]. The structural data are consistent with the weaker Lewis acidity of the gallium as the halide co-ligands become heavier. Multinuclear NMR studies suggest that in chlorocarbon solutions partial dissociation of the ligands occur, which increases with the halide co-ligand Cl < Br < I. The o-xylyl dithioether, o-C6H4(CH2SMe)2, despite being pre-organised for chelation, also forms [(GaCl3)2(mu-L-L)]. The corresponding diselenoether complex decomposes in solution with C-Se bond cleavage to form the selenonium salt [o-C6H4CH2Se(Me)CH2][GaCl4], which was structurally characterised. The ditelluroether o-C6H4(CH2TeMe)2 undergoes rapid C-Te bond fission and rearrangement upon reaction with GaCl3, and the telluronium species [o-C6H4CH2Te(Me)CH2]+ and [MeTe(CH2(o-C6H4)CH2TeMe)2]+ have been identified by ES+ mass spectrometry from their characteristic isotope patterns.

Synthesis, characterisation and structures of thio-, seleno- and telluro-ether complexes of indium(III) halides

The indium(III) halo-bridged octahedral dimers [InX(2)(L-L)(mu-X)(2)InX(2)(L-L)] (X = Cl: L-L = MeS(CH(2))(2)SMe, MeSe(CH(2))(2)SeMe, (n)BuSe(CH(2))(2)Se(n)Bu), the ionic trans-[InX(2)(L-L)(2)][InX(4)] (X = Cl: L-L = (i)PrS(CH(2))(2)S(i)Pr; X = Br: L-L = MeS(CH(2))(2)SMe, (i)PrS(CH(2))(2)S(i)Pr, MeSe(CH(2))(2)SeMe), cis-[InCl(2)(thiamacrocycle)][InCl(4)] (thiamacrocycle = [12]aneS(4) or [14]aneS(4)) and the neutral, octahedral [InCl(3)([9]aneS(3))] and [InCl(3){MeC(CH(2)SMe)(3)}] were obtained in good yield by the reaction of 1:1 molar ratios of InX(3) with the ligand in anhydrous CH(2)Cl(2) solution. The distorted tetrahedral [InX(3)(Me(2)Se)] (X = Cl, Br or I) and [InX(3)(Me(2)Te)] (X = Br or I) were obtained from 1:3 and 1:2 molar ratios respectively of InX(3) and Me(2)E (E = Se or Te) also in CH(2)Cl(2). The ligand-bridged, distorted tetrahedral dimers [(InCl(3))(2){micro(2)-o-C(6)H(4)(CH(2)SMe)(2)}] and [(InCl(3))(2){micro(2)-MeTe(CH(2))(3)TeMe}] are formed even from a 1:1 In:ligand ratio. Key structure types were confirmed from crystal structures of [InCl(2){RSe(CH(2))(2)SeR}(micro-Cl)(2)InCl(2){RSe(CH(2))(2)SeR(2)}] (R = Me or (n)Bu), trans-[InX(2){(i)PrS(CH(2))(2)S(i)Pr}(2)][InX(4)] (X = Cl or Br), trans-[InBr(2){MeSe(CH(2))(2)SeMe}(2)][InBr(4)], cis-[InCl(2)([14]aneS(4))][InCl(4)] and [InBr(3)(Me(2)Se)]. The bulk complexes have been characterised by IR and Raman spectroscopy and microanalyses, while (1)H, (77)Se{(1)H} and (125)Te{(1)H} NMR spectroscopy show that the compounds are extremely labile in solution and undergo rapid dynamic exchange equilibria. Comparisons are drawn between these structurally rather diverse In(III) chalcogenoether complexes and the corresponding Ga(III) species (all of which are neutral and involve distorted tetrahedral coordination). The reaction of TlCl(3) with Me(2)E (E = Se or Te) shows that chlorination of Me(2)E rather than adduct formation occurs, while no reaction occurred between TlCl(3) and Me(2)S, consistent with Tl(III) being a very poor Lewis acid.

The X-ray crystal structures of (O,O-2,3-dimethylbutylene and O,O-2-dimethylpropylene dithiophosphato)diphenyltellurium(IV) derivatives, Ph2Te[S2POCMe2CMe2O]2 and 2Ph2Te[S2POCH2CMe2CH2O]2·2Ph2TeCl2·CS2 and those of (O,O-2,3-dimethylbutylene and O,O-2-dimethylpropylene dithiophosphoric acids, HS2POCMe2CMe2O and HS2POCH2CMe2CH2O

Abstract The immediate environment about tellurium in Ph2Te[S2POCMe2CMe2O]2 (1) and 2Ph2Te[S2POCH2CMe2CH2O]2·2Ph2TeCl2·CS2 (2) is essentially that of a saw-horse structure in which the lone-pair is apparently stereochemically active and occupying an equatorial position in a distorted trigonal bipyramid. However, when the second sulfur atom of the unsymmetrical bidentate ligand is included in the coordination sphere, the arrangement about tellurium in compound 1 is better described as distorted octahedral and that in Ph2Te[S2POCH2CMe2CH2O]2 as distorted pentagonal pyramidal. An intermolecular association involving a chlorine atom of Ph2TeCl2 results in a pentagonal bipyramidal arrangement. Sulfur and chlorine bridges between the Te atoms of Ph2Te[S2POCH2CMe2CH2O]2 and Ph2TeCl2 indicate pseudo dimers or Te2S2Cl cages. The isolation of this mixed species rather than Ph2TeCl[S2POCH2CMe2CH2O] was most unexpected. There is no indication of hydrogen bonding in HS2POCMe2CMe2O (3) and HS2POCH2CMe2CH2O (4); even the shortest S–S internuclear distance, which is in compound 3, is 3.556(2) A. In both acids, the P–SH bond is significantly longer than the PS terminal bond.

Synthesis, spectroscopic studies and structural systematics of phosphine oxide complexes with Group II metal (beryllium-barium) nitrates

Complexes of the nitrates of beryllium, magnesium, calcium, strontium and barium with the phosphine oxides OPPh3, Ph2P(O)CH2P(O)Ph2, and o-C6H4(P(O)Ph2)2 have been prepared and characterised by analysis and IR spectroscopy and the structures of [Be(OPPh3)2(NO3)2], [Mg(OPPh3)2(NO3)2], [Ca{Ph2P(O)CH2P(O)Ph2}2(NO3)2] and [Ca{o-C6H4(P(O)Ph2)2}2(NO3)2] have been determined. The solution speciation has been probed by a combination of 1H, 31P{1H} and 9Be NMR spectroscopy and conductance measurements. The variation in speciation and stability from Be–Ba is interpreted in terms of changes in the charge/radius ratio of the cations—thus whilst Be and Mg interact strongly with the phosphinoyl ligands, strontium and especially barium have very limited affinity for these ligands, and the complexes are extensively dissociated in solution.

Structural diversity in supramolecular complexes of MCl(3) (M = As, Sb, Bi) with constrained thio- and seleno-ether ligands.

MCl(3) react with o-C(6)H(4)(EMe)(2) (E = S, Se) or o-C(6)H(4)(CH(2)ER)(2) (E = S, R = Me or Et; E = Se, R = Me) in anhydrous CH(2)Cl(2) or MeCN to give the yellow (Bi) or white (Sb) complexes, [MCl(3){o-C(6)H(4)(EMe)(2)}], [(MCl(3))(2){o-C(6)H(4)(CH(2)SMe)(2)}(3)], [MCl(3){o-C(6)H(4)(CH(2)SEt)(2)}], and [(BiCl(3))(4){o-C(6)H(4)(CH(2)SeMe)(2)}(3)], which were characterized by IR/Raman, (1)H NMR spectroscopy, and microanalysis. The corresponding reactions with AsCl(3) gave oils. Using the tetrachalcogenoethers, 1,2,4,5-C(6)H(2)(CH(2)EMe)(4) (E = S or Se), gave [(MCl(3))(2){1,2,4,5-C(6)H(2)(CH(2)EMe)(4)}] (E = S: M = As, Sb or Bi; E = Se: M = As) as powdered solids. The structures adopted are extremely diverse within this related series. Crystal structure determinations show infinite chains for [MCl(3){o-C(6)H(4)(EMe)(2)}] (M = Bi, E = S or Se; M = Sb, E = S), although the structures differ significantly in detail. [BiCl(3){o-C(6)H(4)(SMe)(2)}] is formed through chains of orthogonal μ-Bi(2)Cl(2) units linked together, with one dithioether ligand chelating per Bi atom, and seven-coordinate Bi; [SbCl(3){o-C(6)H(4)(SMe)(2)}] comprises weakly associated Sb(2)Cl(6) dimer units linked into chains by weakly bridging dithioethers, where both available lone pairs on each S atom are used. [BiCl(3){o-C(6)H(4)(SeMe)(2)}] comprises distorted square pyramidal units involving pyramidal BiCl(3) primary coordination and a weakly chelating diselenoether ligand, and assembled into infinite chains through long bridging Bi···Cl interactions via all three Cls. The 2:3 M:L complexes [(MCl(3))(2){o-C(6)H(4)(CH(2)SMe)(2)}(3)] (M = Bi or Sb) are isostructural, and also show one-dimensional polymers, but this time the coordination is based upon pyramidal MCl(3) units, with secondary bonding via three long M···S contacts from bridging dithioethers, and a further long M···Cl bridge which completes a distorted seven-coordinate environment at M. The Et-substituted thioether analogue gives the 1:1 [MCl(3){o-C(6)H(4)(CH(2)SEt)(2)}] for both Bi and Sb; the former showing a chain polymer structure based upon seven-coordinate Bi and bridging dithioethers and the latter a weakly Cl-bridged dimer with distorted octahedral coordination at Sb, with a chelating dithioether. The 4:3 [(BiCl(3))(4){o-C(6)H(4)(CH(2)SeMe)(2)}(3)] complexes are based upon a central BiCl(6) octahedron linked to each of the other three Bi atoms via two bridging Cl atoms; the outer Bi atoms are also bonded to two mutually trans Se donor atoms from distinct diselenoethers, and two terminal Cl atoms, giving a distorted octahedral coordination environment at Bi. One of the two crystallographically independent tetrabismuth units is discrete, while the other shows further Cl-bridges to adjacent units giving an infinite network. [(AsCl(3))(2){1,2,4,5-C(6)H(2)(CH(2)SMe)(4)}] also forms an infinite network based upon square pyramidal As(III), and comprises pyramidal AsCl(3) units each weakly coordinated to two (mutually cis) S-donor atoms from two different thioether ligands. The Sb-analogue is structurally very similar; however, in this case a solvent MeCN occupies the sixth coordination site. Finally, [(AsCl(3))(2){1,2,4,5-C(6)H(2)(CH(2)SeMe)(4)}] forms an infinite chain based upon distorted octahedral coordination at As through three terminal (pyramidal) Cl atoms, two Se atoms from κ(2)-μ(2)-selenoethers, although unexpectedly the chelation is through Se atoms that are mutually meta on the aromatic ring; with one Se atom on each ligand using both of its lone pairs to bridge (weakly) between two As atoms. These MCl(3)-chalcogenoether adducts are mostly weakly associated, and lead to very diverse structures which result from a combination of intra- and intermolecular interactions and crystal packing.

Selenoether macrocyclic chemistry—syntheses and properties of new potentially tridentate and hexadentate Se/O-donor macrocycles

Treatment of O(CH2CH2SeCN)2 with Na in NH3(l), followed by dropwise addition of a thf solution of o-C6H4(CH2Br)2 at -40 degrees C leads to formation of three mixed Se/O-donor macrocycles which are separable by column chromatography, the [1 + 1] species L1, the [2 + 2] ring L2 and the [3 + 3] ring L3, of which L2 is by far the major species. Using the same starting materials, but in a high dilution cyclisation at room temperature with NaBH4 in thf/EtOH gives exclusively the [1 + 1] ring, L1. The saturated ring Se/O-donor macrocycles, L4 and L5 are obtained by simultaneous dropwise addition of solutions of O(CH2CH2SeCN)2 and Br(CH2)3Br to NaBH4 suspended in thf/EtOH. The small tridentate Se2O-donor ring, L4, is again the dominant product under these conditions (71%), although the more flexible precursors in this reaction also give rise to the larger Se4O2-donor ring, L5, as a by-product in 8% yield. These compounds are readily separated and purified by column chromatography (ethyl acetate:hexane, 1:19). The new macrocycles have been characterised by 1H, (13)C{1H} and (77)Se{1H} NMR spectroscopy and mass spectrometry, together with crystal structures of L1 and L2. Complexes of L1 and L2 with late transition metals (Pd(II), Pt(II), Cu(I) and Ag(I)) are also described.

Synthesis of a series of 2,3-disubstituted 4H-1,4-benzothiazines and X-ray crystal structure of ethyl 7-chloro-3-methyl-4H-1,4-benzothiazine-2-carboxylate

The reaction between 2-aminobenzenethiol and ethyl acetoacetate is studied under a variety of conditions, and a procedure for the exclusive synthesis of 1,4-benzothiazines by the neat reaction of substituted aminothiols with β-ketoesters and β-dicarbonyl compounds in 85–96% yield is described. With microwave heating, even when both the reactants are solid, yields are high, reaction times brief, and work-up easy. A facile reaction is also observed even in a solid-state reaction. The molecular structure of ethyl 7-chloro-3-methyl-4H-1,4-benzothiazine-2-carboxylate (4d) was determined by single-crystal X-ray diffraction.

CHEMISTRY OF OXOMOLYBDENUM(V) AND (VI) COMPLEXES INCORPORATING OXYGEN, NITROGEN, AND/OR SULFUR DONOR ATOMS. II. SYNTHESIS AND CHARACTERIZATION OF SOME HETEROLEPTIC DIOXOMOLYBDENUM(VI) COMPLEXES OF THE TYPE [MoO2Cl(L)L′] (L=DITHIOCARBAMATES OR XANTHATES AND L′=OPPh3 AND DMSO)

ABSTRACT Heteroleptic dioxomolybdenum(VI) complexes of the type [MoO2Cl(L)L′] (L=diethyl dithiocarbamate, diisopropyl dithiocarbamate, pyrrolidine dithiocarbamate, piperidine dithio-carbamate, methyl xanthate or isopropyl xanthate; L′=triphenylphosphine oxide OPPh3 or dimethyl sulfoxide DMSO) have been synthesised by treating equimolar amounts of MoO2Cl2(L′)2 with the sodium or potassium salts of the corresponding dithiocarbamates or xanthates. All of these derivatives are coloured solids which are soluble in polar solvents. They have been characterized by elemental analyses and spectral (electronic, IR, NMR) studies.