Rosalice Mendonça Silva

Structures, semi-empirical calculations and thermolyses of some five- and six-membered chelate organotin mercaptide complexes

Abstract Characterization of Ph 2 Sn(Cl)(MBT) ( 1 ) (HMBT=2-mercaptobenzothiazole) has been carried out by IR, Mossbauer, 1 H, 13 C and 119 Sn spectroscopies and by X-ray crystallography for 1 together with that of Ph 2 Sn(SCH 2 CH 2 S) ( 2 ). Compound 1 , unexpectedly obtained from the reaction between Ph 2 SnCl 2 and KMBT in a 1:2 mole ratio, has a trigonal-bipyramidal geometry, due to intramolecular SnN interactions, both in the solid state and in solution; the axial sites are occupied by N and Cl, N(24)SnCl(4)=155.27(17)°, the chelate bite angle, N(24)SNS(15), is 64.65(17)°. Compound 2 is essentially monomeric in the solid state and has a distorted tetrahedral structure; the bond angles at tin vary from 92.50(16)° [S(2)SnS(5)] to 116.4(6)° [C(6)SnC(12)]. The shortest intermolecular Sn⋯S contact in 2 is 3.885 A, just within the sum of the van der Waals’ radii for Sn and S (4.0 A). PM3 semi-empirical calculations for 2 indicated that the geometry at the tin center can be accounted for by a high degree of p-character in the tin bonding orbitals to sulfur; PM3 semi-empirical calculations on Ph 2 Sn(SCH 2 CH 2 CH 2 S) ( 3 ) indicated the geometry at tin to be less distorted from tetrahedral, with a SSnS angle of 99°; the calculations further indicated that the only stable conformation of the six-membered ring in 3 is the chair form.

Crystal structures of three [bis(1,3-dithiole-2-thione-4,5-dithiolato)zincate]2− salts: [Q]2[Zn(dmit)2] (Q=1,4-Me2-pyridinium or NEt4) and [PPh4]2[Zn(dmit)2]·DMSO. Comparison of the dianion packing arrangements in [Q]2[Zn(dmit)2]

Abstract [Zn(dmit)2]2− dianions in [Q]2[Zn(dmit)2] complexes (2: Q=1,4-Me2-pyridinium (C7H10N) or NEt4), and [PPh4]2[Zn(dmit)2]·DMSO ((2: Q=PPh4)·DMSO) have distorted tetrahedral geometries, as a result of the 94.49(3) to 95.27(3)° range of the bite angle of the dmit ligands; H2-dmit=4,5-dimercapto-1,3-dithiole-2-thione, H2C3S5. The Zn–S bond lengths are in the range from 2.3285(8) to 2.3520(9) A. In (2: Q=C7H10N) and (2: Q=NEt4), both the cations and the dianions are found in alternating layers, which form columns and sheets. Whereas in (2: Q=C7H10N), there are no S⋯S contacts less than the sum of the van der Waals radii, 3.70 A, S⋯S contacts at 3.5792(13) and 3.6605(12) A, within dianion layers, are found in (2: Q=NEt4). In ((2: Q=PPh4)·DMSO), the steric bulk of the [PPh4]+ cations is such that the dianions cannot be distributed in well-defined sheets: no S⋯S contacts less than 4.0 A are found in ((2: Q=PPh4)·DMSO). The structures are compared with those reported for other [Q]2[Zn(dmit)2] compounds.

Syntheses, characterization and X-ray structure of potassium hydrotris(2-mercaptothiazolyl)borate, KMt, and potassium hydrotris(methimazole)borate, KTm

Os compostos hidrotris(2-mercaptotiazolil)borato de potassio, KMt, (1), e hidrotris(2-metimazolil)borato de potassio, KTm, (2), foram preparados ao se reagir a amina tiol correspondente com KBH4. Foram caracterizados por metodos espectroscopicos e analise elementar. As estruturas no estado solido de KMt.4H2O e do composto 2 foram determinadas por analises de difracao de raios-X. A maior maciez do ânion em KMt.4H2O, em comparacao com 2, e indicada pela ausencia de interacao entre ele e o cation, que possui moleculas de agua em sua esfera de coordenacao. Em KMt.4H2O a geometria em torno do ion potassio e octaedrica distorcida e em 2, pirâmide de base quadrada distorcida. Em 2 o ion potassio esta coordenado a dois atomos de enxofre dos aneis de um mesmo ânion e a tres outros atomos de enxofre pertencentes a unidades KTm vizinhas. Ambos os compostos possuem uma estrutura polimerica.

A triclinic polymorph of 1,3-thia­zolidine-2-thione (2-mercaptothia­zoline)

A planar conformation of 1,3-thiazolidine-2-thione (TZDTH), C3H5NS2, was crystallized for the first time. The new triclinic polymorph (P\overline 1) obtained was compared in terms of its intra- and intermolecular geometry with three previous reports of a monoclinic polymorph (P2(1)/n). The packing is based on centrosymmetric dimers of TZDTH, linked by N-H...S hydrogen bonds.

Syntheses and characterization of nickel thiolate complexes: X-ray structure of [Ni(SCH2CH2S)(PPh2CHCHPPh2)]

Abstract The complexes [Ni(SCH2CH2S)(dppen)], dppen=PPh2CHCHPPh2 (1) and [Ni(SCH2CH2CH2S)(dppen)] (2), have been prepared by reacting dried NiCl2, the phosphine and the appropriate dithiolate compound, in a 1:1:1 molar ratio. For both complexes the 31P NMR spectra confirmed that a chelate ring was formed around the metal, as the single resonance showed a downfield shift compared to the free phosphine. A less shielding effect was observed for the five-member ring formed in complex 1. In the 13C NMR could be observed a pseudo triplet for the resonance of the methylene carbons as a result of a different coupling to the phosphorus atoms. The crystal structure of complex 1 was determined by X-ray diffraction. Two molecules were found in the unit cell with square planar geometries, with one of them more distorted than the other.

Formation of sulfido ciobium complexes through C-S bond activation

Upon reacting (h5-C5H5)2NbCl2, h5-C5H5 = Cp, and (Ph)3Sn(SPh), in THF, (h5-C5H5)2Nb(Cl)(m-S)Sn(Ph)3(Cl), 1, and (h5-C5H5)2Nb(S)Cl, 2, were obtained. Complexes 1 and 2 were characterized by IR, 1H-NMR, 13C-NMR, Mossbauer spectroscopies, elemental analysis as well as by atomic absorption. Hydrolysis of 1 yielded the m-oxo species, (h5-C5H5)2Nb(Cl)(m-O)Sn(Ph)3Cl, 3, which was characterized by IR, 1H-NMR, 13C-NMR and Mossbauer spectroscopies, elemental analysis, atomic absorption as well as by X-ray crystallography. It crystallizes in the space group Pca21 with a = 17.282(3), b = 18.122(4), c = 17.3269(2), V = 5426.2(16) A3, and Z = 8. Additional studies indicated that the complexes were formed as a result of the nucleophilic displacement of the niobium-chloride bond by the thiolate ligand followed by a C-S bond cleavage. The cleavage occurs with an excess of the thiolate compound equal to or greater than 2:1.

γ-Lactones from Mezilaurus synandra☆

Abstract The trunk wood of Mezilaurus synandra contains the known alkaloids coclaurine, corytuberine and norcinnamolaurine, besides the novel (2 R ,3 R ,4 S )-2-dodec-ω-enyl-3-hydroxy-4-methylbutanolide.

Synthesis and X-ray Crystal Structure of a Stable cis-1,2-bis(diphenylphosphino)ethene Monodentate Thiolate Platinum Complex and TGA Studies of its Precursors

The stable Pt(II) complex [Pt(SPh)2(dppen) (4), (dppen, Ph2PCH=CHPPh2) was obtained from [PtCl(SPh)2(SnPh3)cod] (1) (cod = 1,5-cyclooctadiene) by reductive elimination reaction of SnClPh3 and substitution of the cod ligand by the diphosphine, albeit in low yields. Yields of 80% were obtained when [Pt(SPh)2cod] (3) was used as the starting material instead. The viability of these reactions was suggested by a TG study, performed on the starting materials. Complex 4 was characterized by multinuclear NMR (195Pt, 31P, 1H and 13C) and IR spectroscopies and elemental analysis. The molecular structure, solved by an X-ray diffraction study, exhibted a slightly distorted square-planar geometry and short C=C and Pt-P bond distances which were interpreted in terms of a p interaction between the double bond and the metal-ligand bond, as observed for other diphosphine compounds described previously.

Oxidative Additon of Tin Thiolates Yielding New Pt-Sn Heterobimetallic Complexes

The reactions between CODPtCl2, COD = 1,5 cyclooctadiene, and the tin thiolate compounds (Ph)3Sn(SPh) and (Ph)2Sn(SPh)2 have been studied. Reaction between CODPtCl2 and (Ph)3Sn(SPh) yielded two new Pt-Sn heterobimetallic complexes depending on the CODPtCl2/(Ph)3Sn(SPh) molar ratio. For a 1:2 molar ratio, CODPt(SPh)2(Cl)Sn(Ph)3.2CH2Cl2, complex 1, was obtained, together with the homometallic complex CODPt(SPh)Cl.CH2Cl2. For a 1:1 molar ratio the complex formed was CODPt(SPh)(Cl)2Sn(Ph)3.3CH2Cl2, complex 2. Reaction with (Ph)2Sn(SPh)2 did not yielded any heterobimetallic complex, but rather CODPt(SPh)2.4CH2Cl2. The complexes were characterized by IR, 1H-NMR, 13C-NMR, 195Pt-NMR, 119Sn-NMR and Mossabauer spectroscopies, elemental analysis and atomic absorption.

Synthesis and X-ray crystal structure elucidation of an organometallic oxide containing Nb and Sn

Abstract The organometallic oxide (η 5 -C 5 H 5 ) 2 Nb(Cl)(μ-O)Sn(Ph) 2 Cl 2 , 2 , was prepared and characterized by spectroscopic methods and elemental analysis. The molecular structure was determined by X-ray crystallography. The Nb atom is in a pseudotetrahedral coordination geometry environment comprised of the two Cp rings and the chlorine and oxygen atoms. The coordination geometry around the Sn atom is a distorted trigonal bipyramidal.The determined Nb–O bond distance of 1.789(6) A indicates a partial double bonding between Nb and O. Although the Sn–O bond can be described as a dative bond, it is a very strong interaction, 2.22(16) A. The formation of 2 involved the activation of one of the Sn–C phenyl bonds of the tin starting material. Residual water present in the reaction solvent was the source of the bridging oxygen in the molecule.