José M. Varela

Diorganotin(IV)-promoted deamination of amino acids by pyridoxal: SnR2+2 complexes of pyridoxal 5'-phosphate and of the Schiff base pyridoxal-pyridoxamine (PLPM), and antibacterial activities of PLPM and [SnR2(PLPM-2H)] (R = Me, Et, Bu, Ph)

Pyridoxal 5′-phosphate (PLP) and pyridoxal (PL) itself were reacted with diorganotin(IV) derivatives in the presence and absence of aminoacids. With PLP the complexes [SnR 2 (PLP-2H)] (R=Me, Et, Bu) were isolated and characterized by EI and FAB mass spectrometry and by IR, Raman and Mossbauer spectroscopy. Reaction mixtures containing PL, valine or glycine and SnR 2 (OAc) 2 (R=Me, Et) afforded complexes of the form [SnR 2 (PLPM-2H)], where PLPM is the Schiff base formed by condensation of PL and pyridoxamine (PM). PM was presumably formed by transamination between valine or glycine and PL. The PLPM complexes, and their butyl and phenyl analogues, were also synthesized directly by reacting SnR 2 O and PLPM, and were characterized by EI and FAB MS, by IR, Raman, Mossbauer and NMR spectroscopy, and in the case of the methyl and ethyl compounds by single-crystal X-ray diffractometry. Crystals of [SnMe 2 (PLPM-2H)]·H 2 O and [SnEt 2 (PLPM-2H)] consist of molecules in which the ligand is bound to the metal through the O atoms of the two deprotonated phenolic hydroxyl groups and the iminic N atom, and the metal exhibits distorted square pyramidal coordination. Both PLPM and its complexes show intense antibacterial activity against Pseudomonas aeruginosa (ATCC27853), but only the complexes exhibit significant activity against the other four bacterial strains assayed, Staphylococcus aureus , Bacillus subtilis , Escherichia coli and a carbapenem-resistant P. aeruginosa strain.

Reaction of the diethyltin(IV) cation with pyridoxine (PN, vitamin B6) in the presence of various anionic species: the crystal structure of [SnEt2(PN–H)]Cl

Abstract Reaction of the diethyltin(IV) cation with pyridoxine (PN, vitamin B6) in 80:20 (v/v) ethanol–water mixtures containing NO3− and Cl−, NO3− and AcO− or Cl− and AcO− ions in various molar ratios was investigated. The compounds [SnEt2(PN–H)]Cl (1), [SnEt2(PN–H)](NO3)·2H2O (2) and [SnEt2(PN–2H)] (3) were isolated. These compounds were characterized by IR, Raman and Mossbauer spectroscopy and EI and FAB mass spectrometry. The structure of compound 1, determined by X-ray diffraction, consists of dimeric [SnEt2(PN–H)]22+ units (in which two bridging-chelating hydrogen pyridoxinate anions link Sn atoms with coordination number five) and hydrogen-bonded Cl− ions. The behaviour of these compounds in DMSO-d6 and DMF-d7 was studied by NMR spectroscopy.

Triphenyltin(IV) sulfanylpropenoates: synthesis, crystal structures and antimicrobial activities

Three new triphenyltin(IV) sulfanylcarboxylates with the general formula [Q][SnPh3(L)] (Q = di-isopropylammonium cation; L = tspa, pspa or pyspa, where t = 3-(2-thienyl)-, p = 3-(2-phenyl)-, py = 3-(2-pyridinyl)- and spa = 2-sulfanylpropenoato) have been prepared by reaction of triphenyltin(IV) hydroxide with the corresponding acid in the presence of di-isopropylamine in ethanol. The compounds have been characterized by elemental analysis and mass spectrometry and by IR, Mossbauer and NMR (1H, 13C, 119Sn) spectroscopy. X-ray studies of the crystal structures of [Q][SnPh3(pspa)] and [Q][SnPh3(pyspa)] show that in both compounds the tin atom is coordinated to three phenyl C atoms and to S and one O atom of the ligand L. All three complexes are active against strains of the Gram-positive bacterium Staphylococcus aureus, but are inactive or only slightly active against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Copyright © 2000 John Wiley & Sons, Ltd.

Servant leadership and ethics: a dyadic examination of supervisor behaviors and salesperson perceptions

This study uses dyadic data from 145 salespeople paired with their managers to investigate relationships among servant leadership, ethical work climate (EWC), behavior control, trust in supervisor (TS), and salesperson performance. The manuscript tests a conceptual model based on precepts from servant leadership, the services climate concept, and the EWC notion. Research findings show that servant leadership behaviors from management (SLMB) impact salesperson performance through a mediating process that involves servant leadership perceptions from the salesperson (SLSP) and EWC. Results also show that (1) behavioral control moderates the impact of SLMB on SLSP and (2) TS moderates the impact of SLSP on EWC.

New structural features in triphenylphosphinesilver(I) sulfanylcarboxylates

We investigated the reactions of 1.5 : 1 : 1 mole ratio mixtures of triphenylphosphine, silver nitrate and 3-(aryl)-2-sulfanylpropenoic acids H(2)xspa in chloroform/water, where in the acid nomenclature, spa = 2-sulfanylpropenoato and x = p, Clp, mp, diBr-o-hp or f with p = 3-phenyl-, Clp = 3-(2-chlorophenyl)-, mp = 3-methoxyphenyl-, diBr-o-hp = 3-(3,5-dibromo-2-hydroxyphenyl)- and f = 3-(2-furyl)-. The compounds [Ag(PPh(3))(Hpspa)](1), [(AgPPh3)2(xspa)][x = Clp (2), o-mp (3), p-mp (4), diBr-o-hp (5) and f (6)] and [Ag(PPh3)3(Hfspa)](7) were isolated and all except 7 were characterized by IR, Raman and FAB mass spectrometry and by 1H, 13C and 31P NMR spectroscopy. Compound 6 was also characterized by (13)C CP/MAS, and compounds 1 and 6 by (109)Ag NMR spectroscopy. The crystal structures of 1, 2, 3, 4.(CH3)2CO, 5, 6.(CH3)2CO and 7 were determined by X-ray diffraction. has a supramolecular structure based on hydrogen bonding between dinuclear units, and all the other complexes adopt discrete structures. 2, 3, 4.(CH3)2CO, 5, and 6.(CH3)2CO are tetranuclear, and 7 mononuclear. The tetranuclear complexes contain the eight-membered coordination ring Ag4S2O2 (2, 3, 4.(CH3)2CO, 6.(CH3)2CO) or the twelve-membered ring Ag4(CO2)2S2 (5).

Synthesis and antimicrobial activities of silver(I) sulfanylcarboxylates. Structural isomers with identically or unequally coordinated Ag centers in an Ag4S4 ring.

We have investigated the reactions of silver nitrate and 3-(aryl)-2-sulfanylpropenoic acids [H(2)xspa, x: p = 3-phenyl-, f = 3-(2-furyl)-, t = 3-(2-thienyl)-, py = 3-(2-pyridyl)-] and 2-cyclopentylidene-2-sulfanylacetic acid (H(2)L) in 1 : 1 and 2 : 1 molar ratios. The 1 : 1 molar ratio gave compounds of type [Ag(HL)]; reaction of these compounds with diisopropylamine and NaOH gave [HQ][Ag(L)] (HQ = diisopropylammonium) and Na[Ag(L)] x H(2)O, respectively. These compounds, as well as those of type [Ag(2)(L)] obtained with the 1 : 2 molar ratio, were isolated and characterized by IR and NMR ((1)H and (13)C) spectroscopy. (109)Ag NMR spectroscopy and ESI-MS spectrometry were also used in some cases. The crystal structures of [HQ][Ag(pspa)] (11), in which the presence of structural isomers was detected, and [HQ][Ag(cpa)] (15) were determined by X-ray diffractometry. The antimicrobial activity of the complexes against E. coli, S. aureus, B. subtilis, P. aeruginosa/Resistant P. aeruginosa, and C. albicans was tested.

Synthesis and antimicrobial activities of silver(I) 3-(substituted phenyl)sulfanylpropenoates.

We investigated the reactions of silver nitrate with 3-(substituted phenyl)-2-sulfanylpropenoic acids H(2)L [L=xspa, where spa=2-sulfanylpropenoato and xin{Clp=3-(2-chlorophenyl)-, -o-mp=3-(2-methoxyphenyl)-, -o-hp=3-(2-hydroxyphenyl)-, -p-hp=3-(4-hydroxyphenyl)-, diBr-o-hp=3-(3,5-dibromo-2-hydroxyphenyl)-}] in 1:1 and 2:1 molar ratios. The 1:1 reactions gave compounds of type [Ag(HL)], which reacted with NaOH to afford Na[Ag(L)].xH(2)O (x=1 or 2) and with diisopropylamine to afford [HQ][Ag(L)] (HQ=diisopropylammonium). The 2:1 reactions gave products of type [Ag(2)(L)]. All the new compounds were isolated and characterized by IR spectroscopy, and all except the 2:1 adducts (which were insoluble) were studied by (1)H and (13)C NMR spectroscopy; ESI-MS spectrometry was also used for [HQ][Ag(L)] and Na[Ag(L)].xH(2)O, and the crystal structures of H(2)Clpspa and [HQ][Ag(Clpspa)] were determined by X-ray diffractometry. The antimicrobial activities of the complexes against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, Pseudomonas aeruginosa and carbapenem-resistant P. aeruginosa were evaluated and compared with those of Ag(I) complexes with other aryl sulfanylpropenoates or related ligands.

Au–O Interactions and others in triphenylphosphinegold(I) sulfanylpropenoates with diverse structures

We investigated the reactions of triphenylphosphinegold(I) chloride in ethanol or methanol with the 3-(2-aryl)-2-sulfanylpropenoic acids H2xspa [x = f, t, p; f = 3-(2-furyl)-, t = 3-(2-thienyl)-, p = 3-phenyl-; spa = 2-sulfanylpropenoato] in 1 ∶ 1 and 2 ∶ 1 mole ratios, and the reactions of diisopropylamine with the 1 ∶ 1 complexes. Compounds of types [Au(PPh3)(Hxspa)], [HQ][Au(PPh3)(xspa)] (HQ = diisopropylammonium) and [(AuPPh3)2(xspa)] were isolated and characterized by IR, Raman and FAB mass spectrometry and by 1H, 13C and 31P NMR spectroscopy. The structures of (Htspa)2·Me2CO and of the complexes [Au(PPh3)(Hfspa)] (1), [HQ][Au(PPh3)(pspa)] (6), [(AuPPh3)2(fspa)] (7), [(AuPPh3)2(tspa)]·2MeOH (8·2MeOH) and [(AuPPh3)2pspa]·2MeOH (9·2MeOH) were determined by X-ray diffractometry; those of the Au complexes exhibit π-stacking, hydrogen bonding and Au–Au and Au–O interactions as well as the expected Au–S and Au–P bonds.

Complexes derived from 4-amino-3-methyl-5-thione-1,2,4-triazole and monoorganomercury moieties. Crystal structure of (4-amino-5-mercapto-3-methyl-1,2,4-triazolato)methylmercury(II)

The compounds [HgR(L)] (R  Me or Ph; L  4-amino-5-mercapto-3-methyl-1,2,4-triazolate) have been prepared and the crystal structure of the methylmercury(II) compound determined. This compound crystallizes in the monoclinic space group P21/n with a = 5.087(1), b = 10.102(1), c = 16.167(2) A, β = 98.56(1)°, Z = 4 (R = 0.027; Rw = 0.030). It is formed of molecules in which the triazolate anion is bound to mercury strongly via the S atom and weakly via the amine N; there is also a weak intermolecular interaction between the endocyclic N and the Hg atom of a neighbouring unit.

Mono-organomercury and diorganothallium derivatives of rhodanine: Crystal structure of dimethyl(rhodaninato)thallium(III)

The complexes HgR(Rd) and TIR2(Rd) (R = Me, Ph; HRd = rhodanine) have been prepared from the reaction of the ligand with the appropriate organometallic hydroxide (Tl) or acetate (Hg). The crystal structure of TlMe2(Rd) was obtained and shows that the thallium atom is coordinated by two oxygen atoms and a sulphur atom from three different ligands, as well as the two carbon atoms of the methyl groups. The compound crystallizes, forming a planar association along the plane defined by the crystallographic axes ac. Comparison of this compound with TlPh2(Rd) and HgR(Rd) was undertaken using mass, IR, and multinuclear (1H, 13C, 199Hg, 205Tl) NMR spectra.