Fast transport of HCl across a hydrophobic layer over macroscopic distances by using a Pt(II) compound as the transporter: micro- and nanometric aggregates as effective transporters.

Bis-(diethyl-dithioxamidate)platinum(ii) is able to transport HCl from the donor aqueous phase to the receiving one over a mean distance of 12 cm in about 3 minutes across an organic membrane in the bulk, without stirring of the organic phase, i.e. at a rate far exceeding the unidirectional macroscopic diffusion coefficient. The way in which this surprising phenomenon can happen is linked to the behaviour of HCl which, because of dynamic interactions with [Pt(HEt2C2N2S2)2] (in which HCl is hosted as a tight ion pair [Pt(H2Et2C2N2S2)2][Cl]2) and chloroform molecules, gives rise to observable nanometric and micrometric domains, more dense than the surrounding bulk, whose formation and disaggregation processes accelerate the unidirectional macroscopic diffusion of HCl. Thermodynamic parameters obtained from the study of acid-base behaviour of the system Pt(ii) species/HCl/CHCl3 also agree with the proposed mechanism of HCl transport.

Metal Complexes as Self-Indicating Titrants for Acid-Base Reactions in Chloroform.

The paper reports an unprecedented spectrophotometric determination of amines in chloroform, in which amines are not transformed into colored derivatives. This result has been achieved by exploiting the acid-base properties of the tight-ion-paired metal complexes [(HR2DTO)Pt(H2R2DTO)][Cl], which are able to donate a HCl molecule to an amine, giving rise to an ammonium salt and to the neutral complexes [(HR2DTO)2Pt]. The circumstance that [(HR2DTO)Pt(H2R2DTO)][Cl] and [(HR2DTO)2Pt] species show different absorptions in the visible region of the electromagnetic spectrum enables the aforementioned platinum complexes to behave as self-indicating titrants in the spectrophotometric determination of aliphatic amines, which are known to be UV-vis transparent. The new method has been tested by determining a series of fatty amines in the bulk and gave excellent results. The limits of applicability of this method (pKa > 4) were found by testing a series of benzodiazepines.

Crystal structure of (µ-N,N'-di-benzyl-dithio-oxamidato-κN,S:N',S')bis-[(η(3)-crotyl)palladium(II)].

In the centrosymmetric dinuclear title compound, [Pd2(C4H7)2(C16H14N2S2)], the metal atom is η(3)-coordinated by three C atoms of a crotyl ligand [Pd-C = 2.147 (4), 2.079 (5) and 2.098 (5) Å], the longest distance influenced by the steric inter-action with the benzyl substituents of the di-benzyl-dithio-oximidate (DTO) ligand. The Pd-N and Pd-S bonds to this ligand are 2.080 (3) and 2.3148 (9) Å, respectively, completing a square-planar coordination environment for Pd(II). The benzyl groups are oriented so as to maximize the inter-action between a benzylic H atom and an S atom, resulting in a dihedral angle of 77.1 (2)° between the benzene rings and the metal complex plane. In the crystal, no inter-complex hydrogen-bonding inter-actions are present.

Crystal structure of N,N'-bis-(4-methyl-phen-yl)di-thio-oxamide.

Two half mol-ecules of the title compound, C16H16N2S2, are present in the asymmetric unit and both mol-ecules are completed by crystallographic inversion centers at the mid-points of the central C-C bonds: the lengths of these bonds [1.538 (5) and 1.533 (5) Å] indicate negligible electronic delocalization. The trans-di-thio-oxamide fragment in each mol-ecule is characterized by a pair of intra-molecular N-H⋯S hydrogen bonds. In the crystal, mol-ecules are linked by weak C-H..π inter-actions, generating a three-dimensional network.

Fast transport of HCl across a hydrophobic layer over macroscopic distances by using a Pt(II) compound as the transporter.

[Pt(H-(ethyl)2-dithiooxamidate)2] plays the role of a HCl symporter, allowing fast HCl transport over macroscopic distances (cm scale) across a hydrophobic layer made of a chloroform solution, without any stirring. The process is limited by interfacial transfer, whereas HCl is transported within the hydrophobic phase at extremely high rates.

Allylpalladium dimers with metals connected by binucleating dithiooxamidates in two different coordination modes: solution behavior and solid-state structure.

A series of allylpalladium dimers having metals connected by binucleating dialkyldithiooxamidate [N(R)SC-CS(R)N](2-) [R = methyl, ethyl, isopropyl, benzyl, isoamyl, (S)-1-(1-phenyl)ethyl, meso-(1-phenyl)ethyl, and rac-(1-phenyl)ethyl] were prepared by reacting the monochelate [(η(3)-allyl)Pd(N(R)SC-CS(R)NH κ-S,S Pd)] with [(η(3)-allyl)PdCl](2) in chloroform. At low temperature (20 °C), the bimetallic complexes [(η(3)-allyl)Pd](2)(µ-dialkyldithiooxamidate κ-N,N' Pd, κ-S,S' Pd') (kinetic compounds) are formed in a short reaction time (10 min). At a higher temperature (50 °C) and a longer reaction time (24 h), the corresponding bimetallic isomers [(η(3)-allyl)Pd](2)(µ-dialkyldithiooxamidate κ-N,S Pd, κ-N',S' Pd') (thermodynamic compounds) are obtained. Both kinetic and thermodynamic compounds can exist as endo or exo isomers, depending on the reciprocal orientation of the allyl cuspids. Both endo and exo isomers are only detectable in solution when the alkyl substituents are chiral alkyl groups. Moreover, diffractometric modeling agrees with the presence of both isomers in the solid state even when the alkyl substituent is an achiral alkyl group. In a chloroform solution, endo and exo isomers undergo isomeric conversion owing to the apparent allyl rotation that follows the Pd-N bond rupture in the (η(3)-allyl)Pd(N^N) frame of kinetic compounds or in the (η(3)-allyl)Pd(N^S) frame of thermodynamic compounds. The dithiooxamidate [N(R)SC-CS(R)N](2-), when engaged in a κ-N,S Pd, κ-N',S' Pd' coordination mode, behaves as a hybrid hemilabile binucleating ligand. At room temperature and in a chloroform solution, the kinetic compounds rearrange into the thermodynamically more stable isomers in about 3 or 4 days. The higher stability of the thermodynamic species was evaluated by means of computational studies in accordance with the maximum hardness principle. Finally, the crystal structures of [(η(3)-allyl)Pd](2)(µ-diethyldithiooxamidate κ-N,S Pd, κ-N',S' Pd'), [(η(3)-allyl)Pd](2)(µ-meso-(1-phenyl)ethyldithiooxamidate κ-N,S Pd, κ-N',S' Pd'), and [(η(3)-allyl)Pd](2)(µ-rac-(1-phenyl)ethyldithiooxamidate κ-N,N' Pd, κ-S,S' Pd') are reported.

The absolute configuration of palladium(II) and ruthenium(II) pseudochiral centers in either chiral or achiral environments.

The meso-dithioxamide H-((R)-1-(1-phenyl)ethyl)-NSC-CSN-((S)-1-(1-phenyl)ethyl)-H (H(2)-mesoDTO) bonds [(η(6)-p-cymene)chlorido-ruthenium(II)](+) or [(η(3)-allyl)-palladium(II)](+) fragment and provides the C(s) symmetrical complexes [(η(6)-p-cymene)ClRu(H-mesoDTO κ-S,S Ru)] (1) and [(η(3)-allyl)palladium(H-mesoDTO κ-S,S Pd)] (2). These complexes are pseudochiral, and each of them exists as a mixture of two symmetrical meso forms. The improper symmetry of [(η(3)-allyl)palladium(H-mesoDTO κ-S,S Pd)] has been broken in two different ways: (i) by changing the symmetrical allyl moiety with a η(3)-crotyl frame or (ii) by substituting the residual amidic hydrogen in the dithiooxamidate ligand with a M(PR(3))Cl(+) fragment (M = Pd or Pt and PR(3) = triorganophosphine). As a consequence, a chiral plane is added to the pseudochiral palladium center, and two pairs of enantiomers are formed in each case. Furthermore, [(η(6)-p-cymene)chlorido-ruthenium(II)](+) and [(η(3)-allyl)-palladium(II)](+) fragments have been joined by means of the binucleating meso-dithiooxamidate ligand in a κ-S,S Ru κ-N,N Pd coordination mode. The resulting C(s)-symmetrical complex [(η(6)-p-cymene)ClRu(µ-mesoDTO κ-S,S Ru κ-N,N Pd)Pd(η(3)-allyl)] (8) possesses two pseudochiral metal centers, and it is therefore a mixture of four isomeric meso forms. All of these isomers in a chloroform solution interconvert in that both palladium and ruthenium invert their configurations. A mechanism of epimerization for both palladium and ruthenium is proposed. The absolute configurations of pseudochiral palladium in [(η(3)-allyl)(c)-Pd(µ-((R)-1-(1-phenyl)ethyl)-NSC-CSN-((S)-1-(1-phenyl)ethyl) κ-N,N (c)-Pd κ-S,S (A,C)-Pd)(A,C)-Pd(tri(n)propyl-phosphine)Cl] (6) and of pseudochiral palladium and ruthenium in [(η(3)-allyl)(c)-Pd(µ-((R)-1-(1-phenyl)ethyl)-NSC-CSN-((S)-1-(1-phenyl)ethyl) κ-N,N (c)-Pd κ-S,S(s)-Ru)(s)-Ru(η(6)-isopropyltoluene)Cl] (8) are provided. A suitable stereochemical notation is proposed for bimetallic complexes containing pseudochiral centers in either a chiral or an achiral environment.

Tight-contact ion pairs involving Pt(II) dithiooxamide complexes: the acid-base reactions between hydrohalogenated ion-paired complexes and pyridine.

The equilibrium constants relative to HCl exchange between Pt(II)-containing tight contact ion pairs (TCIP) and pyridine have been investigated in chloroform solution at 298 K. The general formulas of the metal species are: {[Pt(H(2)-R(2)-dithiooxamide)(2)](2+), 2Cl(-)} (a-type compounds; R = methyl (1a), ethyl (2a), n-propyl (3a), iso-propyl (4a), n-butyl (5a), cyclohexyl (6a), benzyl (7a), beta-phenyl-ethyl (8a), allyl (9a)) and {[(H-R(2)-dithiooxamidate)Pt(H(2)-R(2)-dithiooxamide)](+), Cl(-)} (b-type compounds; R has the same meanings as before, given rise to 1b-9b species; moreover, the mixed R compound 10b, containing R = benzyl on a DTO (dthiooxamidate/dithiooxamide) ligand and R = ethyl on the other DTO ligand, has also been investigated). Moreover, the parent species [Pt(H-R(2)-dithiooxamidate)(2)] (c-type compounds; 1c-10c) have also been prepared. Out of 29 compounds reported in the paper, 19 compounds are here reported for the first time, and their synthesis and characterization data are also given. Compounds of a-type exhibit two successive equilibrium constants, which are related to successive HCl transfer from the TCIP to pyridine. By comparing the equilibrium constants Kc of the various b-type species, we have been able to (i) obtain information on the relative stability of the TCIP and, by taking advantage of the two equilibrium constants Kc1 and Kc2 found for each a-type species, (ii) gain knowledge on the electronic interaction between the two basic sites of the Pt(II) bis-dithiooxamide complexes, mediated by the metal center. Linear relationships are found between the pKc of the compounds and the sigma-Taft value (Sigma sigma*) of the amine substituents of the DTO ligands. Interestingly, the slope of such linear correlations is much steeper for pKc2 than for pKc1, indicating that the electronic interaction between the basic sites increases with the electron donating ability of the R substituent. A parallel is proposed between the splitting of HCl transfer equilibrium constants in a-type TCIP and oxidation potential splitting in dinuclear, bridge-linked metal complexes.

Solid-state luminescence switching of platinum(ii) dithiooxamide complexes in the presence of hydrogen halide and amine gases.

In the solid state, a non-luminescent platinum(ii) dithiooxamide species adsorbs gaseous HCl, yielding a tight ion pair species which exhibits photoluminescence; the process is quantitatively reversed on heating or by exposing the sample to ammonia vapors.

195Pt NMR of heteropolymetallic complexes containing secondary dithiooxamides as binucleating ligands.

Monometallic [Pt{S-S2C2(NR)2H}2] (S-S2C2(NR)2H = kappa2-S,S-S2C2(NR)2H = bis-dialkyl-dithioxamidate, R = methyl, isoamyl, benzyl) and binuclear and trinuclear heterobimetallic complexes [Pt{S-S2C2(NR)2H}{mu-S2C2(NR)2}MLn] (mu-S2C2(NR)2 = kappa2-S,S(Pt)-kappa2-N,N(M)-S2C2(NR)2) and [Pt{{mu-S2C2(NR)2}MLn}2] (MLn+ = [(eta3-allyl)palladium]+, [bis-(2-phenylpyridine)rhodium]+, [(eta6-p-cymene)(chloro)ruthenium]+, [(1,4-cyclooctadiene)rhodium]+, [(pentamethylcyclopentadienyl)(chloro)rhodium]+) have been prepared and characterized. The progressive substitution of the residual amidic hydrogen in the [Pt{S-S2C2(NR)2H}2] complexes with a MLn+ metal fragment results in the deshielding of platinum nuclei, a red shift of the MLCT absorption maximum, and a decrease in the oxidation potential. Such behavior has been interpreted as a progressive electron shift from platinum to the binucleating ligands, the extent of which depends on the nature of MLn+ metal fragment.

Bis(di-2-pyridyl sulfide-kappa2N,N')(4-methylpyrimidin-2-yl 2-pyridylmethyl sulfide-kappa2N,S)ruthenium(II) bis(hexafluorophosphate) acetonitrile solvate.

The crystal structure of the title compound, [Ru(C10H8N2S)2(C11H11N3S)](PF6)2.C2H3N, is composed of a bivalent octahedral RuII complex, two PF6- anions and an acetonitrile solvent molecule. Two PF6- units are found on a crystallographic binary axis, therefore contributing just one half each to the asymmetric unit cell. The structure displays a peculiar stereochemistry of the cation. Three bidentate ligands around the Ru centre, together with the coordination of the non-symmetric S atom, mean that these two atoms are chiral. This would lead to four stereoisomers, but only an enantiomeric pair was found in the analyzed sample.

Trinuclear heterobimetallic complexes with binucleating dithioxamides: stereoselective synthesis and solution behavior involving Pd-N bond rupture.

Bischelate platinum(II) complexes of the type [Pt(H-R(2)-N(2)C(2)S(2))(2)] (H-R(2)-N(2)C(2)S(2)(-) = dialkyl-dithioxamidate) are ditopic receptors which, after coordination of the first Pd(eta(3)-allyl)(+) moiety, induce the orientation of the second palladium-allyl fragment. Thus, a series of trimetallic complexes of formula bis-[(eta(3)-allyl)-palladium(II)](mu-bis-dialkyl-dithioxamidate-platinum(II) kappa-S,S-kappa-S',S'-Pt-kappa-N,N-Pd-kappa-N',N'-Pd') has been prepared in which the allyl fragments are oriented toward the same side of the molecular plane. We have also prepared the trimetallic complex using a dithioxamide obtained from the racemic phenylethylamine. Only two isomers were produced in equimolar ratio: the racemate that has four homochiral alkyl substituents and the mesoform containing the meso-dithioxamide that has homochiral substituents on the same side of molecular plane. Under the effect of the temperature, the trimetallic Pd-Pt-Pd complexes undergo rapid allyl isomerization; the mechanism of the isomerization, which is similar to that found by us in an analogue Pt-Pd bimetallic complex, is discussed. The crystal and molecular structure of bis-[(eta(3)-allyl)-palladium(II)](mu-bis-[S]-phenylethyl-dithioxamidate-platinum(II) kappa-S,S-kappa-S',S'-Pt-kappa-N,N-Pd-kappa-N',N'-Pd') has been reported.

N,N'-dibenzyldithiooxamide.

The title compound, alternatively known as N,N'-dibenzylethanedithioamide, C(16)H(16)N(2)S(2), lies about an inversion centre and contains a planar trans-dithiooxamide fragment characterized by a strong intramolecular hydrogen bond between the S atom and the adjacent amide H atom in the solid state, with an S...N distance of 2.926 (1) A. The aryl substituent is oriented orthogonal to the mean plane of the trans-dithiooxamide fragment due to steric hindrance and this effect is discussed.

(eta3-Allyl-2kappa3C)(chloro-1kappaCl)(micro-N,N'-diethyldithioxamidato-1:2kappa4S,S':N,N')[diphenyl(2-pyridyl)phosphine-1kappaP]palladium(II)platinum(II) chloroform solvate.

The title compound, [PdPtCl(C(3)H(5))(C(6)H(10)N(2)S(2))(C(17)H(14)NP)].CHCl(3), was obtained by deprotonation of the initial platinum(II) complex of the dithioxamide and subsequent reaction with [Pd(eta(3)-C(3)H(5))(micro-Cl)](2). Both metal atoms exhibit a square-planar coordination geometry, with the two planes forming a dihedral angle of 21.7 (2) degrees. The dithioxamide bis-chelating bridge is flat.

trans-diacetonitrilebis(di-2-pyridyl sulfide-N,N')ruthenium(II) bis(tetrafluoroborate) monohydrate.

The title complex, [Ru(C10H8N2S)2(CH3CN)2](BF4)2*H2O, is the product of the solvolysis of [Ru(dps-N,N)2(dps-N,S)](PF(6))2 (dps is di-2-pyridyl sulfide) in the presence of HBF4 in acetone-acetonitrile at room temperature. There are two independent cations, with the Ru atoms on inversion centres; each Ru atom has an octahedral geometry with the dps molecules behaving as N,N'-bidentate ligands and assuming a trans arrangement.

Luminescence Properties of Platinum(II) Dithiooxamide Compounds.

Tight contact ion pairs of general formula {Pt(H(2)-R(2)-dto)(2)(2+),(X(-))(2)} have been prepared, and their absorption spectra and luminescence properties (at room temperature in dichloromethane fluid solution and at 77 K in butyronitrile rigid matrix) have been studied (dto = dithiooxamide; R = methyl, X = Cl (1); R = butyl, X = Cl (2); R = benzyl, X = Cl (3); R = cyclohexyl, X = Cl (4); R = cyclohexyl, X = Br (5); R = cyclohexyl, X = I (6)). The absorption spectra of all the compounds are dominated by moderately strong Pt(dpi)/S(p) to dithiooxamide (pi) charge transfer (Pt/S --> dto CT) bands in the visible region (epsilon in the 10(4)-10(5) M(-)(1) cm(-)(1) range). Absorption features are also present at higher energies, due to pi-pi transitions centered in the dto ligands (ligand centered, LC). All the compounds exhibit a unstructured luminescence band in fluid solution at room temperature, with the maximum centered in the 700-730 nm range. The luminescence bands are blue-shifted about 4000 cm(-)(1) on passing to the rigid matrix at 77 K. Luminescence lifetimes are on the 10(-)(8)-10(-)(7) s time scale at room temperature and 1 order of magnitude longer at 77 K. Luminescence is assigned to triplet Pt/S --> dto CT excited states in all cases. Compounds 3-6 also exhibit a second higher-energy luminescence band at room temperature, centered at about 610 nm, attributed to a LC excited state. Charge transfer interactions between halides and dto ligands destabilize dto-centered orbitals, affecting the energy of Pt/S --> dto CT transitions and states. The X counterions and X --> dto CT levels are proposed to play a role in promoting excited state conversion between LC and Pt/S --> dto CT levels. The R substituents on the nitrogen atoms of the dto ligands influence the absorption and photophysical properties of the compounds, by affecting proximity of the ion pairs. The possibility to functionalize the R substituents may open the way to interface these luminescent compounds with desired substrates and to construct supramolecular assemblies.