On the reaction of Ph2PNHPPh2 with RNCS (R=Et, Ph, p-NO2C6H4): preparation of the zwitterionic ligand EtNHC(S)Ph2P==NPPh2C(S)NEt (HSNS) and the zwitterionic metalate [(SNS)Rh(CO)

The reaction of Ph(2)PNHPPh(2) (PNP) with RNCS (Et, Ph, p-NO(2)(C(6)H(4))) gives addition products resulting from the attack of the P atoms of PNP on the electrophilic carbon atom of the isothiocyanate. When PNP is reacted with EtNCS in a 1:2 molar ratio, the zwitterionic molecule EtNHC(S)PPh(2)==NP(+)Ph(2)C(S)N(-)Et (HSNS) is obtained in high yield. HSNS can be protonated (H(2)SNS(+)) or deprotonated (SNS(-)), behaving in the latter form as an S,N,S-donor pincer ligand. The reaction of HSNS with [(acac)Rh(CO)(2)] (acac=acetylacetonate) affords the zwitterionic metalate [(SNS)Rh(CO)]. Other products can be obtained depending on the R group, the PNP/RNCS ratio (1:1 or 1:2), and the reaction temperature. The proposed product of the primary attack of PNP on RNCS, Ph(2)PN==PPh(2)C(S)NHR (A), cannot be isolated. Reaction of A with another RNCS molecule leads to 1:2 addition compounds of the general formula RNHC(S)PPh(2)==NP(+)Ph(2)C(S)N(-)R (1), which can rearrange into the non-zwitterionic product RNHC(S)PPh(2)==NP(S)Ph(2) (2) by eliminating a molecule of RNC. Two molecules of A can react together, yielding 1:1 PNP/RNCS zwitterionic products of the formula RNHCH[PPh(2)==NP(S)Ph(2)]PPh(2)==NP(+)Ph(2)C(S)N(-)R (3). Compound 3 can then rearrange into RNHCH[PPh(2)==NP(S)Ph(2)](2) (4) by losing a RNC molecule. When R=Et (a), compounds 1 a, 2 a (HSNS), and 4 a have been isolated and characterized. When R=Ph (b), compounds 2 b and 4 b can be prepared in high yield. When R=p-NO(2)C(6)H(4) (c), only compound 3 c is observed and isolated in high yield. The crystal structures of HSNS, [(SNS)Rh(CO)], and of the most representative products have been determined by X-ray diffraction methods.     

Intramolecular dealkylation of chelating diamines with Ru(II) complexes

N,N, N',N'-Tetraethylethylenediamine undergoes simple or double intramolecular dealkylation reactions in the presence of the complexes [RuCl2(diene)]n (diene = cod, nbd) or trans-[RuCl2(diene)(morfoline)2 at 80 degrees C to afford chelating amine ligands which contains one or two N-H functionalities.     

Easy Access to Phosphido-Selenido Clusters. Reaction of [Ru3(CO)12] with Ph2(pyth)PSe {pyth=5-(2-Pyridyl)-2-Thienyl} and Crystal Structure of [Ru3(μ3-Se)(μ-PPh2)(μ-pyth)(CO)6{P(pyth)Ph2}]

The reaction of [Ru₃(CO)₁₂] with Ph₂(pyth)PSe (pyth=5-(2-pyridyl)-2-thienyl) allows to obtain two novel clusters [Ru₃(₃-Se)₂(CO)₇{P(pyth)Ph₂}₂] 1 and [Ru₃(₃-Se)(-PPh₂)(-pyth)(CO)₆{P(pyth)Ph₂}] 2 in satisfactory yields. The first one exhibits the well-known bicapped, open triangular, 50-electron nido-core, whereas 2, whose crystal structure has been determined, shows the rather rare Ru₃Se tetrahedron with the Ph₂P and pyth fragments as side-bridging ligands. Morever cluster 2 belongs to the exiguous family of selenido-phosphido clusters not easily achievable by other routes.     

Energy and frames of reference in general relativity

Summary When relativistic theory amalgamates space and time into event, other magnitudes of classical mechanics merge or superimpose. In special relativity it is still easy to find them again by referring to the inertial frame of reference, but general relativity presents them to us as already identified in the curvatures of the Riemannian universe, which admits of no inertial frames, except local ones. It is a search for particular magnitudes and relations (such as momentum and conservation laws), physically interpretablein the classical sense, which specifies a privileged frame. Starting from this frame of reference, the present Note sets out to define the energy-momentum density and super-potentials that give rise, in the same frame, to the known integral results due to the Einstein and Freud psendotensors. Thus the snags arising out of the transformation laws of these pseudotensors are eliminated at the same time.

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Sommario Quando, nelle teorie relativistiche, si sostituisce alle grandezze spazio e tempo la loro fusione nell'evento, altre grandezze della meccanica classica si fondono e sovrappongono. Nella relatività ristretta è ancora agevole ritrovarle, riferendosi all'osservatore inerziale; ma la Relatività generale ce le presenta già fuse nelle curvature dell'Universo riemanniano, che non ammette osservatori inerziali, se non locali. E' la ricerca di particolari grandezze e relazioni, (come la quantità di moto e le leggi di conservazione), fisicamente interpretabili nel senso classico, che precisa un riferimento privilegiato. Valendosi di questo riferimento, vengono definiti, nella presente Nota, densità di energia-quantità di moto e superpotenziali che danno luogo, nello stesso riferimento, ai noti risultati integrali dovuti agli pseudo-tensori di Einstein e Freud. Risultano così eliminati, nello stesso tempo, gli inconvenienti dovuti alle leggi di trasformazione di questi pseudo-tensori.

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Study conducted under the auspices of the mathematical teams of the Consiglio Nazionale delle Ricerche.     

Novel (4-oxothiazolidine-2-ylidene)benzamide derivatives: synthesis,characterization and crystal structures

Research on Chemical Intermediates - A convenient, one-pot, multicomponent synthesis of new (4-oxothiazolidine-2-ylidene)benzamide derivatives by unsymmetrical thioureas, various amines and methyl...     

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Gold(I) dicarbene complexes [Au₂(MeIm‐Y‐ImMe)₂](PF₆)₂ (Y=CH₂ ( 1 ), (CH₂)₂ ( 2 ), (CH₂)₄ ( 4 ), MeIm=1‐methylimidazol‐2‐ylidene) react with iodine to give the mixed‐valence complex [Au(MeIm‐CH₂‐ImMe)₂AuI₂](PF₆)₂ ( 1 a^I ) and the gold(III) complexes [Au₂I₄(MeIm‐Y‐ImMe)₂](PF₆)₂ ( 2 c^I and 4 c^I ). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au₂Cl₄(MeIm‐CH₂‐ImMe)₂](PF₆)₂ ( 1 c^Cl ) and [Au₂Cl₄(MeIm‐(CH₂)₂‐ImMe)₂](Cl)₂ ( 2 c^Cl‐Cl ) (as main product); remarkably in the case of complex 2 , the X‐ray molecular structure of the crystals also shows the presence of I‐Au‐Cl mixed‐sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl₂, Br₂ and I₂ to give the successive formation of the mixed‐valence gold(I)/gold(III) n a^X and gold(III) n c^X (excluding compound 1 c^I ) complexes. However, complex 3 affords with Cl₂ and Br₂ the gold(II) complex 3 b^X [Au₂X₂(MeIm‐(CH₂)₃‐ImMe)₂](PF₆)₂ (X=Cl, Br), which is the predominant species over compound 3 c^X even in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations.     

Coordination properties of the multifunctional S,N,S zwitterionic ligand EtNHC(S)Ph2PNPPh2C(S)NEt

The reaction of trialkylphoshanes and amino-phosphanes with isothiocyanates yields adducts containing the zwitterionic thioamidyl-phosphonium P⁺C(S)N^? functional group. Ligands containing this group were not previously studied, probably due to their instability towards dissociation, in the presence of metal species able to coordinate the P atom. The ligand EtNHC(S)Ph₂PNPPh₂C(S)NEt (HEtSNS) was obtained by reaction of Ph₂PNHPPh₂ with ethylisothiocyanate and proved to be very versatile: it can be protonated giving cation H₂EtSNS⁺ and deprotonated forming the dianion–cation EtSNS^?. HEtSNS and its derivatives behave as ligands showing five possible coordination fashions, S,N,S tridentate and S,S-bidentate (with a bite-angle varying from 180° to 90°), S-monodentate, S,S bridging and N,N,N interaction. Here we describe the coordination chemistry of HEtSNS, in particular towards Rh, Cu, Ag and Au, and some properties of its complexes which are still the only examples containing the P⁺C(S)N^? zwitterionic group.     

Synthesis of copper(I) bis(3,5-dimethylpyrazolyl)methane olefin complexes and their reactivity towards carbon monoxide

The chemistry of bis(3,5-dimethylpyrazolyl)methane complexes of copper(I) has been investigated and a dinuclear copper(I) derivative of formula {Cu₂[μ-CH₂(3,5-Me₂Pz)₂]₂}(TfO)₂ [TfO = trifluoromethanesulphonate anion, ], characterized by an uncommon bridging coordination of the bis(pyrazolyl)methane ligands, has been isolated and characterized by X-ray diffraction methods. Moreover, new olefin derivatives of general formula [Cu[CH₂(3,5-Me₂Pz)₂](olefin)]TfO have been prepared (olefin: coe = cyclooctene, van = 4-vinylanisole, nbe = norbornene), their carbonylation reactions, {Cu[CH₂(3,5-Me₂Pz)₂](olefin)}TfO + CO ? {Cu[CH₂(3,5-Me₂Pz)₂](CO)}TfO + olefin, have been studied gas volumetrically and the thermodynamical parameters of the equilibria for the displacement of the coordinated olefin by carbon monoxide have been determined.     

Heteronuclear rhodium, palladium, platinum, and gold organoimido complexes from dinuclear organoamido rhodium precursors

Treatment of the organoamido complexes [Rh(2)(mu-4-HNC(6)H(4)Me)(2)(L(2))(2)] (L(2) = 1,5-cyclooctadiene (cod), L = CO) with nBuLi gave solutions of the organoimido species [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(L(2))(2)]. Further reaction of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(cod)(2)] with [Rh(2)(mu-Cl)(2)(cod)(2)] afforded the neutral tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(cod)(4)] (2), which rationalizes the direct syntheses of 2 from [Rh(2)(mu-Cl)(2)(cod)(2)] and Li(2)NC(6)H(4)Me. Reactions of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(CO)(4)] with chloro complexes such as [Rh(2)(mu-Cl)(2)(CO)(4)], [MCl(2)(cod)] (M = Pd, Pt), and [Ru(2)(mu-Cl)(2)Cl(2)(p-cymene)(2)] afforded the homo- and heterotrinuclear complexes PPN[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)] (5; PPN=bis(triphenylphosphine)iminium), [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)M(cod)] (M = Pd (6), Pt(7)) and [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)Ru(p-cymene)] (8), while the reaction with [AuCl(PPh(3))] gave the tetranuclear compound [(CO)(4)Rh(2)(mu--4-NC(6)H(4)Me)(2)[Au(PPh(3))](2)] (9). The structures of complexes 6, 8, and 9 were determined by X-ray diffraction studies. The anion of 5 reacts with [AuCl(PPh(3))] to give the butterfly cluster [[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)]Au(PPh(3))] (10), in which the Au atom is bonded to two rhodium atoms. Reaction of the anion of 5 with [Rh(cod)(NCMe)(2)](BF(4)) gave the tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(CO)(6)(cod)] (11) in which the Rh(cod) fragment is pi-bonded to one of the arene rings, while the reaction of the anion of 5 with [PdCl(2)(cod)] afforded the heterotrinuclear complex 6 through a metal exchange process.     

Le coordinate intrinseche e l’integrazione delle equazioni della meccanica dei continui

Sunto Dopo aver definito le coordinate intrinseche in una generica varietà riemanniana viene costruita una variazione del tensore fondamentale che lascia invariate le coordinate stesse. Viene quindi dimostrato che la conoscenza di questa deformazione rende possibile la costruzione di un tensore doppio simmetrico avente data divergenza: cioè fornisce un integrale particolare delle equazioni della statica dei continui comunque curvi a due e tre dimensioni, in presenza di forze di campo. Viene inoltre mostrato che tale integrale particolare serve per costruire l’integrale generale delle equazioni stesse, e delle analoghe in assenza di forze di campo. Si può ottenere così anche l’integrale generale delle equazioni della dinamica dei continui negli spazi-tempo della Relatività generale. Entrata in Redazione il 19 aprile 1971.