Nazir Ahmad

Thermokinetic studies of organotin(IV) carboxylates derived from para-methoxyphenylethanoic acid

Thremogravimetric (TG) studies of a new series of organotin(IV) carboxylates of the general formula RnSnL4-n (where R = CH3, C2H5, C4H9, C6H5, C6H11 and C8H17, n = 2, 3 and L = para-methoxyphenylethanoate anion) have been carried out. Horowitz and Metzger method has been used to calculate thermokinetic parameters. It has been found that diorganotin dicarboxylates have larger activation energy than those of corresponding triorganotin carboxylates. Furthermore, the activation energy, Gibb’s free energy, entropy and enthalpy of diorganotin compounds shows the following trend, (CH3)2SnL2 < (C2H5)2SnL2 < (C4H9)2SnL2 < (C8H17)2SnL2. This is attributed to steady increase in chain length of the alkyl groups. However, triorganotin compounds do not show such behavior.

catena-Poly[bis-(μ(3)-2-methyl-benzoato)disilver(I)].

The crystal structure of the title compound, [Ag2(C8H7O2)2]n, features polymeric chains extending along the a axis, with the two Ag+ cations in a distorted trigonal coordination. The range of Ag—O bond lengths is 2.169u2005(2)–2.433u2005(2)u2005Å, whereas the Ag⋯Ag separations are in the range 2.8674u2005(4)–3.6256u2005(5)u2005Å. The 2-methylbenzoate groups are oriented at a dihedral angle of 60.7u2005(1)° with respect to each other.

Tetra-kis(μ(2)-2-methyl-3,5-dinitro-benzoato-κO:O)bis-[aqua-copper(II)] tetra-hydrate.

The title compound, [Cu2(C8H5N2O6)4(H2O)2]·4H2O, forms a centrosymmetric paddle-wheel-type dimer with an intramolecular Cu⋯Cu distance of 2.6540u2005(4)u2005Å. The CuII atom is in a square-pyramidal coordination environment formed by four O atoms of four carboxylate groups and one water molecule, which is located in the apical position. The carboxylate groups are twisted relative to the benzene rings by 11.09u2005(16) and 45.55u2005(19)°. The nitro groups are not coplanar with the parent aromatic rings [dihedral angles = 16.2u2005(3)–51.45u2005(14)°]. O—H⋯O hydrogen bonds between the coordinated water molecules and one of the nitro groups, as well as π–π stacking interactions [centroid–centroid distance = 3.5764u2005(12)u2005Å] between the benzene rings, assemble the complex molecules into a one-dimensional polymeric structure which is further extended into a three-dimensional polymeric network via O—H⋯O hydrogen bonds involving the water molecules of crystallization.

catena-Poly[bis­(μ3-2-methyl-3,5-dinitro­benzoato)disilver(I)]

In the title coordination polymer, [Ag2(C8H5N2O6)2]n, the silver ion is coordinated to three O atoms from three different anions in an approximate T-shape with one bond much longer than the other two. The polyhedral connectivity leads to [100] chains containing alternating centrosymmetric four-rings and eight-rings, with a short d 10⋯d 10 Ag⋯Ag interaction [2.8846u2005(4)u2005Å] across the latter. The nitro groups are oriented at dihedral angles of 21.2u2005(5) and 64.3u2005(3)° with respect to the aromatic ring of the ligand. A C—H⋯O interaction occurs in the crystal.

Octa-methyl-bis-(μ(2)-2-methyl-benzoato-κO:O')bis-(2-methyl-benzoato-κO)di-μ(3)-oxido-tetra-tin(IV).

The title compound, [Sn4(CH3)8(C8H7O2)4O2], is a distannoxane derivative of 2-methylbenzoic acid. The crystal structure is composed of centrosymmetric dimers lying about inversion centres. Both independent Sn atoms adopt distorted trigonal-bipyramidal SnC2O3 coordination geometries with the basal planes consisting of two C-atoms from the methyl groups and a bridging O atom. The Sn—C and Sn—O bond lengths lie in the ranges 2.090u2005(2)–2.104u2005(3) and 2.0241u2005(14)–2.2561u2005(15)u2005Å, respectively. The central four-membered planar Sn2O2 ring [Sn⋯Sn distance = 3.2993u2005(2)u2005Å] makes dihedral angles of 5.43u2005(11) and 59.50u2005(7)° with the methylphenyl groups, which are themselves oriented at a dihedral angle of 61.38u2005(8)°. Besides weak C—H⋯O and C—H⋯π interactions, the packing mainly features van der Waals forces between the molecules.

catena-Poly[[trimethyltin(IV)]-μ-2-methylbenzoato-κ2O:O′]

The polymeric structure of the title compound, [Sn(CH3)3(C8H7O2)]n, is composed of zigzag chains in which the tin(IV) atoms, coordinated by three methyl groups, are bridged by toluene-2-carboxylate ligands via their O atoms. A slightly distorted trigonal-bipyramidal SnC3O2 coordination geometry arises for the metal, with the O atoms in the axial sites. Weak C—H⋯O hydrogen bonds help to stabilize the packing.

Tetra­kis(μ-2-methyl­benzoato-κ2O:O′)bis­[(methanol-κO)copper(II)]

In the title compound, [Cu2(C8H7O2)4(CH3OH)2], the Cu—O bond distances are in the range 1.943u2005(2)–2.149u2005(2)u2005Å within a sligthly distorted square-pyramidal coordination. The Cu⋯Cu separation is 2.5912u2005(4)u2005Å. In the crystal, the molecules are linked into polymeric chains propagating in [001] by intermolecular O—H⋯O hydrogen bonds and C—H⋯π interactions.

(Dimethyl sulfoxide-κO)trimeth-yl(2-methyl-3,5-dinitro-benzoato-κO)tin(IV).

In the title mononuclear complex, [Sn(CH3)3(C7H5N2O6)(C2H6OS)], the SnIV ion is coordinated by three methyl groups in the equatorial plane, and by an O atom from a 2-methyl-3,5-dinitrobenzoate ligand and a dimethyl sulfoxide ligand in the axial sites, to form a slightly distorted trigonal–bipyramidal environment. The O atoms of one of the nitro groups are disordered over two sets of sites, with refined occupancies of 0.55u2005(4) and 0.45u2005(4). The closest intermolecular interaction is a weak C—H⋯O hydrogen bond.

catena-Poly[[(2-methyl­benzoato-κ2O,O′)sodium]-di-μ-aqua-κ4O:O′]

In the title coordination polymer, [Na(C8H7O2)(H2O)2]n, the cation is chelated by the carboxylate O atoms of the anion in a bidentate mode and is surrounded by the O atoms of four water molecules. The coordination of the Na+ cation is distorted octahedral. The water molecules bridge adjacent metal cations, forming polymeric layers parallel to (100). The structure is stabilized by an extensive network of O—H⋯O hydrogen bonds.

Poly[(μ6-2-methyl-3,5-dinitro­benzoato)potassium]

In the structure of the title coordination polymer, [K(C8H5N2O6)]n, each ligand bridges six K+ cations. The carboxylate group coordinates both bidentately to one K+ ion and monodentately to two K+ ions, while one nitro group coordinates bidentately to a fourth K+ ion. The last two K+ ions are coordinated by the remaining nitro group, one in a bidentate fashion, the other monodentately through one O atom. This bridging mode results in a three-dimensional network. The coordination geometry of the K+ ion is represented by an irregular KO9 polyhedron. Very weak C—H⋯O interactions are observed in the crystal structure.