Carlos Camacho-Camacho

Rigid five-coordinate diorganotin derivatives of oxalic acid diamides, studied by 119Sn-NMR and X-ray structural analysis

Abstract Bis(2-hydroxy-3,5-di- tert -butyl-phenylanilido) oxalic acid reacts with diorganotin dichlorides, R 2 SnCl 2 , in the presence of triethylamine to give the polycyclic bis(diorganotin) derivatives 1 , in which the surroundings of each tin atom correspond to a distorted trigonal bipyramid with one nitrogen and two carbon atoms in the equatorial and two oxygen atoms in the axial positions. The solid state structure was established for 1a (R=Me) by X-ray analysis, and the agreement between the 119 Sn chemical shift in the solid state and in solution suggests that this structure is retained in solution. It was possible for the first time to determine isotope-induced chemical shifts 1 Δ 12/13 C( 119 Sn) for five-coordinate tin nuclei at natural abundance of 13 C. A positive sign of 1 Δ 12/13 C( 119 Sn) was found for R=Me ( 1a ), Bu ( 1b ) and Ph ( 1c ).

Syntheses and Characterization by NMR Spectroscopy and X-ray Diffraction of Complexes Derived from Metals of Groups 2 and 13 and the Ligand Bis(3,5-di-tert-butyl-1-hydroxy-2-phenyl)amine

Reaction of 3,5-di-tert-butylcatechol and aqueous ammonia with boron, aluminum, gallium, or strontium chloride, or with calcium or barium acetate produce, under oxidizing conditions, neutral complexes of stoichiometric formulae ML (M = BCl), ML2, [M = Al (2), Ga (3), Ca (4), and Ba (5)], and ML3H [M = Sr (6)] [L = different oxidation states of bis(3,5-di-tert-butyl-1-hydroxy-2-phenyl)amine]. The structures of 1 and 4–6 were established by 1H- and 13C-NMR spectroscopy and of 2, 3, and 6 by X-ray diffraction. The coordination compound ClBL (1) was obtained by transmetallation of ZnL2 with BCl3. It is a tetracyclic compound with tetracoordinated boron and nitrogen atoms, the ligand being in the reduced form, bis(hydroxyphenyl)amine. The paramagnetic complexes 2 and 3 crystallized in the triclinic system and are hexacoordinated with two orthogonal planar ligands bonded to the metal atoms. The ligands appear in two different oxidation states: one as the monoanion and another as a radical dianion. Based on their X-ray diffraction molecular structures, it is deduced that both ligands have similar structures, confirming electronic delocalization and fast interconversion of their oxidation states. Ca and Ba complexes are diamagnetic and hexacoordinated, both ligands being monoanions The strontium complex crystallized in the monoclinic system, the metal atom is nonacoordinated, having two ligands as monoanions, and a third one is a neutral protonated diquinone. Its structure is a distorted helix with three paddles in a C3 geometry and its unexpected diamagnetic behaviour is due to the presence of a reduced protonated ligand.

New hexacyclic binuclear tin complexes derived from bis-(3,5-di-tert-butyl-2-phenol)oxamide

Abstract The syntheses of bis-(3,5-di-tert-butyl-2-phenol)oxamide (2a) and four new hexacyclic bimetallic tin compounds derivatives are reported: bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis(dibutyltin) (3), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-(diphenyltin) (4), bis(triethylammonium) bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-(dichlorobutyl-stannate) (5), and bis-[(OSn) ethanol]-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-(chlorophenyltin) (6). All tin compounds show a planar ligand skeleton in which each tin atom is linked to the phenoxy group, to the anilinic nitrogen atom and to the oxygen of the oxamide group. Compounds 3 and 4 have two pentacoordinated diorganyl tin atoms with a distorted bpt geometry, whereas 5 contains a dianionic structure with two hexacoordinated tin atoms bonded to a n-butyl group and to two chlorine atoms and two triethyl ammonium as counterions. Compound 6 has two hexacoordinated tin atoms, each atom is bonded, in addition to the ligand, to one phenyl and one chlorine and coordinated to an ethanol molecule. Characterization of the compounds was made through usual analytical and spectroscopic methods. Structures of 4,6-di-tert-butyl-1-phenol-2-amine 1, the oxamide 2a and the four tin compounds 3–6 were established by the X-ray diffraction analyses.

SYNTHESES, CHARACTERIZATION AND REACTIVITY OF DIBENZOBICYCLIC PHOSPHORANES 10-P-5

Abstract Compound 1 has been prepared by demetallation with PCl3 of bis[3,5-di-tert-butyl-1,2-quinone-1-(2-hydroxy-3,5-di-tert-butylphenyl)imine] zinc complex 14. Compound 1 has been shown to be an excellent precursor in the syntheses of phosphorus heterocycles. The characterization of a new family of compounds such as those derived from 5-aza-2,8-dioxa-1-phosphav-dibenzo-[c,f]bicyclo-[3.3.0]octadiene in which the phosphorus substituents are X = chlorine 1, methyl 2, methoxy 3, isopropylamine 4, n-butylamine 5, sec-butylamine 6, tert-butylamine 7, 2-aminopyrimidine 8, glycol 9, catechol 10, 3,5-di-tert-butylcatechol 11, o-aminophenol 12, and phenylenediamine 13 is reported. The phosphorane system 10-P-5 of compounds 1–13 has been characterized by 1H, 13C and 31P NMR, IR, and mass spectra. The structure of compound 4 was determined by X-ray diffraction. Phosphoranes 1–8 have an aromatic, planar tetracyclic structure, in which the phosphorus atom is a trigonal bipyramid with the oxygen atoms in axial positi...

Novel Organotin(IV) Schiff Base Complexes with Histidine Derivatives: Synthesis, Characterization, and Biological Activity

Five novel tin Schiff base complexes with histidine analogues (derived from the condensation reaction between L-histidine and 3,5-di-tert-butyl-2-hydroxybenzaldehyde) have been synthesized and characterized. Characterization has been completed by IR and high-resolution mass spectroscopy, 1D and 2D solution NMR (1H, 13C  and 119Sn), as well as solid state 119Sn NMR. The spectroscopic evidence shows two types of structures: a trigonal bipyramidal stereochemistry with the tin atom coordinated to five donating atoms (two oxygen atoms, one nitrogen atom, and two carbon atoms belonging to the alkyl moieties), where one molecule of ligand is coordinated in a three dentate fashion. The second structure is spectroscopically described as a tetrahedral tin complex with four donating atoms (one oxygen atom coordinated to the metal and three carbon atoms belonging to the alkyl or aryl substituents), with one molecule of ligand attached. The antimicrobial activity of the tin compounds has been tested against the growth of bacteria in vitro to assess their bactericidal properties. While pentacoordinated compounds 1, 2, and 3 are described as moderate effective to noneffective drugs against both Gram-positive and Gram-negative bacteria, tetracoordinated tin(IV) compounds 4 and 5 are considered as moderate effective and most effective compounds, respectively, against the methicillin-resistant Staphylococcus aureus strains (Gram-positive).

Catalytic Acetylation Amines with Ethyl Acetate

The direct acetylation of various amines with ethyl acetate and {[Me2(MeC00)Sn]20}2 as catalyst is reported. Primary amines are acetylated in high yield while secondary bulky amines and aniline are obtained in low yield. A tentative mechanism is proposed. INTRODUCTION Acetylation of amines has numerous applications in synthetic organic chemistry, such as, a protective group or as a precursor of different functional groups. The reaction is usually achieved through acetylation with acetic anhydride /l/ , or under basic conditions /2,3,4/. Since basic or acid catalyst are often not suitable for sensitive functional groups, the development of new catalysts that allow the preparation of amides, under milder conditions, would increase the synthetic potential of this reaction. We are interested in a new direct synthetic procedure using organotin(IV) complexes as catalysts. Catalytic transesterification 151 and polymerizations 161 have been reported to be carried out under neutral conditions. In particular, transesterification studies with alcohols 151 (proton-donating nucleophiles) have been shown to react with different tin(IV) complexes to afford esters in good yields. We perceived that the use of tin(IV) complexes as catalyst could allow the acetylation reaction of amines in presence of ethyl acetate, in a similar fashion that an alcohol does in a transesterification reaction. This fact motivated us to investigate the potential of a direct synthesis of amides from the acetylation of several amines with ethyl acetate in the presence of dimethyltin(IV) acetic acid distannoxane (Scheme 1).