Paloth Venugopalan

Cationic cobaltammines as anion receptors. Part V. Synthesis, characterization and X-ray structure of [CO(NH3)6]ClMoO4·3H2O

Orange, single crystals of the bimetallic salt hexaamminecobalt(III) chloride molybdate trihydrate, [Co (NH3)6]ClMoO4·3H2O, have been prepared by reacting hot aqueous solutions of hexaamminecobalt(III) chloride and sodium molybdate dihydrate in a 1:1 molar ratio. The salt was characterized by elemental analyses and spectroscopic studies (IR and electronic). The title complex salt crystallizes in orthorhombic, space group Pnma, with a = 18.408(2), b = 8.672(1), c = 8.661(1) Å, V =  1382.6(3) Å3, Z = 4 and R = 0.0255. A single-crystal X-ray structure determination revealed the presence of discrete ions [Co(NH3)6]3+, Cl− and and three lattice water molecule in the solid state. The formation of this salt suggests that [Co(NH3)6]3+ may be used as an anion receptor for the molybdate ion.

Modified Pictet–Spengler reaction. A highly diastereoselective approach to 1,2,3-trisubstituted-1,2,3,4-tetrahydro-β-carbolines using perhydro-1,3-heterocycles

Abstract A flexible variant of the Pictet–Spengler reaction employing oxazinanes as synthetic equivalents of several carbonyl compounds has been developed. Using acid catalyzed one pot condensation of perhydro-1,3-heterocycles various 1,3-disubstituted and 1,2,3-trisubstituted-1,2,3,4-tetrahydro-β-carbolines (THBCs) have been synthesized diastereoselectively.

Abundant Lattice Inclusion Phenomenon with Sterically Hindered and Inherently Shape-Selective Tetraarylpyrenes

Tetraarylpyrenes H1-H4 that typify molecular systems with orthogonal planes and lack hydrogen bonding functional groups were designed as new host systems with three distinct domains for guest inclusion. In particular, H2 and H4 hosts are found to include a variety of guest molecules. We have determined 42 crystal structures overall (i) to establish the importance of skeletal features of the hosts, (ii) to determine their adaptability in binding diverse guest molecules, and (iii) to delineate favored domains for location of guest molecules and preferred modes of association of the host systems. The unique features of H1-H4 are found to permit binding of aliphatic and aromatic guest species differently: the small-sized guest molecules such as CHCl(3), (CH(3))(2)S, etc. are found to be bound in the basin domain, whereas aliphatic and aromatic guests are found to be included in the channel/concave and trough regions, respectively. The crystal structure analyses reveal that as many as 20 out of 28 inclusion compounds of H2 are isostructural with one or more; we have identified 8 different crystal packing types with which each inclusion compound may be associated. The guest-binding potential of host H2 has been exploited to demonstrate the utility of these host systems in (i) the separation of regioisomeric methyl-substituted benzenes and mixtures of cis-trans isomers of decalin, perhydroisoquinoline, and cinnamonitrile, (ii) the stabilization of the keto-enol form of 1,3-diketones, and (iii) the conformational locking of flexible cycloalkanes.

Synthesis, spectroscopic characterization and X-ray crystal structure determination of trialkylbenzylammonium trans-diamminetetranitrocobaltate(III) salts where alkyl = methyl and ethyl

The two cobalt(III) complex salts [(CH3)3NCH2C6H5][trans-Co(NH3)2(NO2)4] and [(C2H5)3 NCH2C6H5][trans-Co(NH3)2(NO2)4] have been synthesized by reacting [(CH3)3NCH2C6H5]Cl and [(C2H5)3NCH2C6H5]Cl, respectively, with K[trans-Co(NH3)2(NO2)4], in aqueous medium at room temperature. The salt [(C2H5)3NCH2C6H5][trans-Co(NH3)2(NO2)4] crystallized from an acetone–water mixture; monoclinic, space group P21/n, cell dimensions a = 10.620(1), b = 14.954(1), c = 14.100(1) Å, β = 109.88°, V = 2105.8(3) Å3, Z = 4. An X-ray structure determination revealed the presence of discrete ions [(C2H5)3NCH2C6H5]+ and [trans-Co(NH3)2(NO2)4]− in the structure. In the anion cobalt(III) is coordinated octahedrally with the expected trans geometry.

Solid state structural and solution studies on the formation of a flexible cavity for anions by copper(I) and 1,2-bis(diphenylphosphino)ethane

Copper(l) complexes of 1,2-bis(diphenylphosphino)ethane (dppe) with a stoichiometry Cu-2(dppe)(3)(X)(2) [X- = CN- (1), SCN- (2), NO3- (3)] are obtained from direct reactions of CuX and dppe. The complexes are structurally and spectroscopically (NMR and IR) characterized. The structure of the [Cu-2(dPPe)(3)](2+) dication is similar to the structural motif observed in many other complexes with a chelating dppe and a bridging dppe connecting two copper centers. In complexes 1 -3, the anions are confined to the cavity formed by the phosphines which force a monodentate coordination mode despite the predominant bidentate/bridging character of the anions. The coordination angles rather than the thermochemical radii dictate the steric requirement of anions. While the solution behavior of 3, with nitrate, is similar to complexes studied earlier, complexes with pseudohalides exhibit new solution behavior

Influence of nitrogen donor ligands on the coordination modes of copper(II) 2-nitrobenzoate complexes: structures, DFT calculations and magnetic properties

Three novel copper(II) 2-nitrobenzoate complexes, [Cu(γ-pic)2(2-nitrobenzoate)2] 1, [Cu(β-pic)2(2-nitrobenzoate)2(H2O)2] 2 and [Cu2(H2tea)2(2-nitrobenzoate)2]·2(H2O) 3 (where γ-pic = 4-methylpyridine, β-pic = 3-methylpyridine and H2tea = mono deprotonated triethanolamine), were isolated by addition of γ-pic, β-pic and H3tea to the hydrated copper(II) 2-nitrobenzoate, [Cu2(2-nitrobenzoate)4(H2O)2]·2H2O, suspended in a methanol : water (4 : 1) mixture. The newly synthesized complexes have been characterized by elemental analyses, thermogravimetric analysis (TGA), spectroscopic techniques (EPR, IR and UV/Visible), magnetic susceptibility measurements, single crystal X-ray structure determination and DFT study. All compounds crystallize in the monoclinic crystal system with the P21/c space group. X-ray structure determination revealed the presence of monomers in both 1 and 2 and dimer in 3 with the deprotonated oxygen atom of the H2tea ligand bridging two Cu(II) atoms. Two co-crystallized water molecules are also present in 3. The crystal lattice is stabilized by C–H⋯O hydrogen bonding interactions in 1 and O–H⋯O, C–H⋯O hydrogen bonding interactions in 2 and 3. The dimeric complex exhibits relatively strong ferromagnetic exchange with J = −100 cm−1 (corresponding to H = JS1S2). The zero-field splitting parameters (zfs) of the dimer triplet states D and E were derived from HF EPR spectra recorded at moderately low temperatures. The sign of D was determined from low-temperature HF EPR spectra.

Magnetic behaviour vs. structural changes in an isomeric series of binuclear copper(II) complexes: an experimental and theoretical study

In an endeavor to study how a polydentate nitrogen donor ligand affects the magnetic properties of copper(II) methoxybenzoates, three novel complexes of copper(II) were investigated. [Cu2(H2tea)2(o-methoxybenzoate)2], [Cu2(H2tea)2(m-methoxybenzoate)2]·2H2O and [Cu2(H2tea)2(p-methoxybenzoate)2]·2H2O (where H2tea = mono-deprotonated triethanolamine) were synthesized by addition of triethanolamine (H3tea) to the hydrated Cu(o-,m-,p-methoxybenzoates)2. The newly synthesized complexes have been characterized by elemental analyses, spectroscopic techniques (electronic and FT-IR), magnetic moment determination, molar conductance studies, TGA, and single crystal X-ray determination. The experimental characterization was integrated with the ab initio theoretical determination of the magnetic coupling constant value and with the analysis of the correlation between this value and the relevant geometrical parameters. Variable temperature solid state magnetization measurements and ab initio calculations indicate a remarkable ferromagnetic coupling of the unpaired electrons centered on the two Cu atoms for the m- and p-methoxybenzoate complexes (J = 100.9 cm−1), while a non-negligible antiferromagnetic coupling is found for the third complex (J = −83.1 cm−1). This differential behaviour can be rationalized on the basis of the out-of-plane displacement (τ) of the alkoxo group with respect to the molecular Cu2O2 plane. Large τ values prevent an efficient overlap between the O 2p and the magnetic Cu 3dx2−y2, favouring a ferromagnetic coupling between the Cu sites.

Synthesis and spectroscopic characterization of trans-[Co(en)2(NO2)2]X (X = dodecyl sulfate, picrate, diclofenac or saccharinate) and the single-crystal X-ray structure of the saccharinate salt, trans-[Co(en)2(NO2)2](C7H4NSO3)·H2O

trans-[Co(en)2(NO2)2]X complexes, where X = C12H25SO4 (1), C6H2N3O7 (2), C14H10Cl2NO2 (3) and C7H4NSO3 (4), have been synthesized by slowly mixing aqueous solutions of trans-dinitrobis(ethylenediamine)cobalt(III) nitrate and sodium dodecyl sulfate, picrate, diclofenac and saccharinate, respectively, at a 1 : 1 mol ratio. Good crystals of trans-dinitrobis (ethylenediamine)cobalt(III) saccharinate monohydrate, [Co(en)2(NO2)2](C7H4NSO3)·H2O, were obtained. The salt is orthorhombic, space group P21212, with a = 21.553(2), b = 8.503(1), c = 10.238(1) Å, Z = 4, V = 1876.3(3) Å3, R 1 = 0.0286 and wR 2 = 0.0727. A structure determination revealed an ionic structure consisting of discrete [Co(en)2(NO2)2]+ cations and [C7H4SO3N]– anions.

Structural studies of diorganotin(IV) sulphonates The crystal structures of [(n-C4H9)2Sn{μ-OSO2C6H2(CH3)3}2]n and its partially hydrolyzed product [(n-C4H9)2Sn{(μ-OH)(μ-OSO2C6H2(CH3)3)}]n

The X-ray crystal structures of [( n -C 4 H 9 ) 2 Sn{μ-OSO 2 C 6 H 2 (CH 3 ) 3 } 2 ] n ( 1 ) and [( n -C 4 H 9 ) 2 Sn{(μ-OH)(μ-OSO 2 C 6 H 2 (CH 3 ) 3 )}] n ( 2 ) were determined to delineate the coordination behaviour of the sulphonate group with tin(IV) and to evaluate the metal sulphonate bonding interactions. The synthesis of 1 has been achieved by azeotropic dehydration of di- n -butyltin(IV) oxide and mesitylenesulphonic acid. 1 is polymeric containing six-coordinate tin and crystallizes from anhydrous toluene in the orthorhombic space group P 2 1 2 1 2 with unit cell dimensions a =12.555(1), b =21.238(1), c =5.415(1) A; Z =2; R , 0.0236 and wR , 0.0607 for 1281 observed reflections. The structure exhibits highly symmetrical bridging bidentate mesitylenesulphonate groups and is made up of an infinite array of ( n -C 4 H 9 ) 2 SnO 4 moieties. Compound 1 hydrolyzes very slowly to [( n -C 4 H 9 ) 2 Sn{(μ-OH)(μ-OSO 2 C 6 H 2 (CH 3 ) 3 )}] n ( 2 ), when kept in CH 3 OH–CHCl 3 mixture at room temperature for 35 days. Crystals of 2 are monoclinic with space group P 2 1 / m and unit cell dimensions a =10.040(1), b =14.500(1), c =13.978(1) A; β =91.58(1)°; Z =4; R , 0.0226; wR , 0.0592 for 2725 observed reflections. The crystal structure is built of polymeric chains in which [{( n -C 4 H 9 ) 2 Sn} 2 (OH) 2 ] units are joined by bridging bidentate meistylenesulphonate groups. The crystal lattice is stabilized by a network of hydrogen bonds running through the sheets, in which an oxygen atom of the sulphonate group and the hydroxyl group attached to tin participate in a symmetrical fashion. In DMSO solutions, chemical shift ( 119 Sn) and 1 J ( 119 Sn– 13 C) values for both 1 and 2 suggest a distorted octahedral geometry around tin in which DMSO may also be involved.

A facile Lewis acid-promoted allylation of azetidin-2-ones

Abstract Exposure of 3α-chloro-3-phenylthioazetidin-2-ones and allyltrimethylsilane to a Lewis acid promotes a remarkably facile and stereoselective C-3 allylation to give 3α-allyl-3-phenylthioazetidin-2-ones 4 in excellent yield. These allylated azetidin-2-ones undergo smooth desulphurization with tri-n-butyltin hydride or Raney-nickel producing cis-3-allyl- and cis-3-propylazetidin-2-ones.