Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 118
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Dalton Trans ; 2020 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-32342078

RESUMO

Early theoretical and experimental investigations of inorganic sulfur-nitrogen compounds were dominated by (a) assessments of the purported aromatic character of cyclic, binary S,N molecules and ions, (b) the unpredictable reactions of the fascinating cage compound S4N4, and (c) the unique structure and properties of the conducting polymer (SN)x. In the last few years, in addition to unexpected developments in the chemistry of well-known sulfur nitrides, the emphasis of these studies has changed to include nitrogen-rich species formed under high pressures, as well as the selenium analogues of well-known S,N compounds. Novel applications have been established or predicted for many binary S/Se,N molecules, including their use for fingerprint detection, in optoelectronic devices, as high energy-density compounds or as hydrogen-storage materials. The purpose of this perspective is to evaluate critically these new aspects of the chemistry of neutral, binary chalcogen-nitrogen molecules and to suggest experimental approaches to the synthesis of target compounds. Recently identified ternary S,N,P compounds will also be considered in light of their isoelectronic relationship with binary S,N cations.

2.
Chem Commun (Camb) ; 55(99): 14965-14967, 2019 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-31774421

RESUMO

The reaction of potassium carbonate with elemental sulfur or selenium in acetone in the presence of [PPN]Cl (PPN = (Ph3P)2N) produces catena-[S12]2-, the longest structurally characterised polysulfide dianion, or spiro-[Se11]2- as ion-separated [PPN]+ salts.

3.
Chem Soc Rev ; 48(15): 4338, 2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31305818

RESUMO

Correction for 'The role of polysulfide dianions and radical anions in the chemical, physical and biological sciences, including sulfur-based batteries' by Ralf Steudel et al., Chem. Soc. Rev., 2019, 48, 3279-3319.

4.
Chem Soc Rev ; 48(12): 3279-3319, 2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31123728

RESUMO

The well-known tendency of sulfur to catenate is exemplified by an extensive series of polysulfide dianions [Sn]2- (n = 2-9) and related radical monoanions [Sn]˙-. The dianions can be isolated as crystalline salts with appropriate cations and structurally and spectroscopically characterized. Although the smaller radical monoanions may be stabilized in zeolitic matrices, they are usually formed in solution via disproportionation or partial dissociation of the dianions as well as by electrochemical reduction of elemental sulfur. An understanding of the fundamental chemistry of these homoatomic species is key to unravelling their behaviour in a broad variety of chemical environments. This review will critically evaluate the techniques used to characterize polysulfide dianions and radical anions both in solution and in the solid state, i.e. Raman, UV-visible, EPR, NMR and X-ray absorption spectroscopy, X-ray crystallography, mass spectrometry, chromatography and high-level quantum-chemical calculations. This is followed by a discussion of recent advances in areas in which these anionic sulfur species play a crucial role, viz. alkali-metal-sulfur batteries, organic syntheses, biological chemistry, geochemical processes including metal transport, coordination complexes, atmospheric chemistry and materials science.


Assuntos
Fontes de Energia Elétrica , Sulfetos/química , Ânions/química , Complexos de Coordenação/química , Cristalografia por Raios X , Radicais Livres/química , Metais Alcalinos/química , Teoria Quântica
5.
Dalton Trans ; 47(36): 12493-12505, 2018 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-29384540

RESUMO

The chemistry of the chalcogen-centred methanides [HC(PR2E)2]- (E = S, Se, Te; R = alkyl, aryl) (PC(H)P-bridged anions) is less well-developed than that of the isoelectronic imidodiphosphinates [N(PR2E)2]-, which are PNP-bridged analogues. The objective of this Perspective is to compare the chemistry of s-block metal complexes of the PC(H)P- and PNP-bridged anions in the context of synthetic approaches, X-ray (solid-state) structures, multinuclear NMR spectra, redox behaviour, and applications in coordination and inorganic heterocyclic chemistry. The related monochalcogeno-centred anions [HC(PR2)(PR2E)]- and [N(PR2)(PR2E)]- (E = S, Se, Te; R = alkyl, aryl) are also included in the discussion. Consideration of the similarities and, especially, the differences in the properties and reactions of the methanides with those of their imidodiphosphinate analogues reveals a number of areas in which the significance of the PC(H)P-bridged anions could be advanced.

6.
Chem Soc Rev ; 46(17): 5182-5192, 2017 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-28702517

RESUMO

Binary S,N anions, e.g., NSN2- and SSNSS-, and related ternary S,N,O anions such as the structural isomers NSO-/SNO- and SSNO- are rarely mentioned in inorganic chemistry textbooks, despite the fact that their salts were synthesised and structurally characterised more than 30 years ago. These fundamentally important species and their conjugate acids, e.g. HNSO and HSNO, have been the focus of numerous investigations in recent years in view of their significance in disciplines as diverse as atmospheric chemistry and cell biology. This Tutorial Review provides a consolidated account of the fundamental chemistry including synthesis, spectroscopic characterisation, molecular and electronic structures, and properties of these intriguing species, and compares these aspects of their behaviour with those of isoelectronic sulfur oxides and N,O anions. A final section draws attention to the significance and applications of these simple S-N species in a broader context.

7.
Dalton Trans ; 46(5): 1357-1367, 2017 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-28091658

RESUMO

Cyclocondensation is a major preparative route for the generation of inorganic heterocycles especially in the case of ring systems involving a Group 15 or 16 element linked to nitrogen. This Perspective will consider recent experimental and computational studies involving the reactions of primary amines (or their synthetic equivalents) with pnictogen and chalcogen halides. The major focus will be a discussion of the identity and role of acyclic intermediates in the reaction pathways to ring formation, as well as the nature of the heterocycles so formed. The similarities and differences between the chemistry of group 15 and 16 systems are emphasised with a view to providing signposts for further investigations.

8.
Dalton Trans ; 45(32): 12691-701, 2016 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-27453403

RESUMO

A high-yield synthesis of [Li{S(H)C(PPh2S)2}]2 [Li2·(3)2] was developed and this reagent was used in metathesis with ZnCl2 and NiCl2 to produce homoleptic complexes 4 and 5b in 85 and 93% yields, respectively. The solid-state structure of the octahedral complex [Zn{S(H)C(PPh2S)2}2] (4) reveals notable inequivalence between the Zn-S(C) and Zn-S(P) contacts (2.274(1) Å vs. 2.842(1) and 2.884(1) Å, respectively). Two structural isomers of the homoleptic complex [Ni{S(H)C(PPh2S)2}2] were isolated after prolonged crystallization processes. The octahedral green Ni(ii) isomer 5a exhibits the two monoprotonated ligands bonded in a tridentate (S,S',S'') mode to the Ni(ii) centre with three distinctly different Ni-S bond lengths (2.3487(8), 2.4500(9) and 2.5953(10) Å). By contrast, in the red-brown square-planar complex 5b the two ligands are S,S'-chelated to Ni(ii) (d(Ni-S) = 2.165(2) and 2.195(2) Å) with one pendant PPh2S group. DFT calculations revealed that the energetic difference between singlet and triplet state octahedral and square-planar isomers of the Ni(ii) complex is essentially indistinguishable. Consistently, VT and (31)P CP/MAS NMR spectroscopic investigations indicated that a mixture of isomers exists in solution at room temperature, while the singlet state square-planar isomer 5b becomes favoured at -40 °C.

9.
Dalton Trans ; 45(14): 6210-21, 2016 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-26629863

RESUMO

The third member of the series of imidoselenium(II) chlorides ClSe[N(tBu)Se]nCl (n = 3) (9) has been isolated from the cyclocondensation reaction of tBuNH2 and SeCl2 in THF in a molar ratio of ca. 3:1 and characterized in the form of two polymorphs 9a and 9b by single crystal X-ray analysis. The unusual structural features of this nine-atom chain are explained satisfactorily in terms of a bonding model that invokes intra-molecular secondary bonding interactions and hyperconjugation. The reaction of the bifunctional reagent ClSe[N(tBu)Se]2Cl (8) with tBuNH2 in THF occurs via concurrent pathways to give 1,3,5-Se3(NtBu)3 (1) and 1,3-Se3(NtBu)2 (3a). The energetics of the reactions of tBuNH2 and SeCl2 in THF have been calculated at the PBE0/def2-TZVPP level of theory in order to assess the feasibility of ClSe[N(tBu)Se]nCl (7­9, n = 1­3) as intermediates in the formation of known cyclic selenium imides. DFT calculations were also employed to explore the energy profile of the pathway of the formation of the first member of the series ClSeN(tBu)SeCl (7) from tBuNH2 and SeCl2 in THF at 298 K. The neutral ligand ClSeN(tBu)SeCl (7) is Se,Se'-coordinated to the metal centre in the unusual adduct [PdCl2{Se,Se'-(SeCl)2N(tBu)}]·[PdCl2{Se,Se'-Se4(NtBu)3}]·MeCN (10·MeCN), which is the first metal complex of an imidoselenium(II) chloride.

10.
Inorg Chem ; 54(19): 9499-508, 2015 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-26379047

RESUMO

The complexes [MCl2{N,N'-(t)BuNSe(µ-N(t)Bu)2SeN(t)Bu}] [M = Cd (1), Hg (2)] were obtained in high yields by the reaction of tert-butylselenium diimide Se(IV)(N(t)Bu)2 with CdCl2 or HgCl2 in tetrahydrofuran. Recrystallization of 1 and 2 from acetonitrile (MeCN) afforded yellow crystals of 1·MeCN and 2·MeCN, respectively. Isomorphic 1·MeCN and 2·MeCN contain an unprecedented dimeric selenium diimide ligand, which is N,N'-chelated to the metal through exocyclic imido groups. In addition to the complexes 1 and 2, the (77)Se NMR spectra of acetonitrile solutions of 1·MeCN and 2·MeCN indicated the presence of the dimeric (t)BuNSe(µ-N(t)Bu)2SeN(t)Bu, monomeric Se(IV)(N(t)Bu)2, and cyclic selenium imides. Density functional theory calculations at the PBE0/def2-TZVPP level of theory were used to assign the (77)Se resonances of the dimer. A comparison of Gibbs energies of formation of some metal dichloride complexes [MCl2{N,N'-Se(IV)(N(t)Bu)2}] and [MCl2{N,N'-(t)BuNSe(µ-N(t)Bu)2SeN(t)Bu}] (M = Zn, Cd, Hg) indicated that the formation of complexes containing a dimeric selenium diimide ligand is favored over those containing a monomeric ligand for the group 12 metals. In the case of the group 10 metal halogenides (M = Ni, Pd, Pt), the Gibbs energies of the complexes with monomeric Se(IV)(N(t)Bu)2 ligands are close to those containing dimeric (t)BuNSe(µ-N(t)Bu)2SeN(t)Bu ligands. A plausible reaction pathway with a low activation energy involves the initial formation of [MCl2{N,N'-Se(IV)(N(t)Bu)2}] (M = Zn, Cd, Hg), which then reacts with another molecule of Se(N(t)Bu)2, leading to the final [MCl2{N,N'-(t)BuNSe(µ-N(t)Bu)2SeN(t)Bu}] complex. Without the presence of group 12 metal halogenides, the [2 + 2] cyclodimerization of Se(IV)(N(t)Bu)2 is virtually thermoneutral, but the activation energy is relatively high, which accounts for the kinetic stability of (t)BuNSe(µ-N(t)Bu)2SeN(t)Bu in solution. A minor byproduct, [Cd7Cl14{N,N'-Se(II)(NH(t)Bu)2}6]·4CH2Cl2, was identified by X-ray crystallography as a heptanuclear cluster with selenium(II) diamide ligands N,N'-chelated to the cadmium centers.

12.
Acta Crystallogr C Struct Chem ; 71(Pt 5): 407-9, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25940898

RESUMO

While exploring the chemistry of tellurium-containing dichalcogenidoimidodiphosphinate ligands, the first all-tellurium member of a series of related square-planar E(II)(E')4 complexes (E and E' are group 16 elements), namely bis(P,P,P',P'-tetraphenylditelluridoimidodiphosphinato-κ(2)Te,Te')tellurium(II) (systematic name: 2,2,4,4,8,8,10,10-octaphenyl-1λ(3),5,6λ(4),7λ(3),11-pentatellura-3,9-diaza-2λ(5),4λ(5),8λ(5),10λ(5)-tetraphosphaspiro[5.5]undeca-1,3,7,9-tetraene), C48H40N2P4Te5, was obtained unexpectedly. The formally Te(II) centre is situated on a crystallographic inversion centre and is Te,Te'-chelated to two anionic [(TePPh2)2N](-) ligands in an anti conformation. The central Te(II)(Te)4 unit is approximately square planar [Te-Te-Te = 93.51 (3) and 86.49 (3)°], with Te-Te bond lengths of 2.9806 (6) and 2.9978 (9) Å.

13.
Inorg Chem ; 54(10): 4990-7, 2015 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-25932943

RESUMO

The cyclocondensation reaction of equimolar amounts of SeCl2 and (Me3Si)2NMe in THF affords 1,3,5,7-Se4(NMe)4 (5b) [δ((77)Se) = 1585 ppm] in excellent yield. An X-ray structural determination showed that 5b consists of cyclic, puckered crown-shaped molecules with a mean Se-N bond length of 1.841 Å typical of single bonds. A minor product of this reaction was isolated as unstable orange-red crystals, which were identified by X-ray analysis as the adduct 1,5-Se6(NMe)2·(1)/2Se8 (1b·(1)/2Se8), composed of cyclic 1,5-Se6(NMe)2 and disordered cyclo-Se8 molecules. A detailed reinvestigation of the cyclocondensation reaction of SeCl2 and (t)BuNH2 as a function of molar ratio and time by multinuclear ((1)H, (13)C, and (77)Se) NMR spectroscopy revealed that the final product exhibits one (77)Se resonance at 1486 ppm and equivalent N(t)Bu groups. The shielding tensors of 28 selenium-containing molecules, for which the (77)Se chemical shifts are unambiguously known, were calculated at the PBE0/def2-TZVPP level of theory to assist the spectral assignment of new cyclic selenium imides. The good agreement between the observed and calculated chemical shifts enabled the assignment of the resonance at 1486 ppm to 1,3,5,7-Se4(N(t)Bu)4 (5a). Those at 1028 and 399 ppm (intensity ratio 2:1) could be attributed to 1,5-Se6(NMe)2 (1b).

14.
Chem Soc Rev ; 44(7): 1725-39, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25692398

RESUMO

The scant attention paid to tellurium in both inorganic and organic chemistry textbooks may reflect, in part, the very low natural abundance of the element. Such treatments commonly imply that the structures and reactivities of tellurium compounds can be extrapolated from the behaviour of their lighter chalcogen analogues (sulfur and selenium). In fact, recent findings and well-established observations clearly illustrate that this assumption is not valid. The emerging importance of the unique properties of tellurium compounds is apparent from the variety of their known and potential applications in both inorganic and organic chemistry, as well as materials science. With reference to selected contemporary examples, this Tutorial Review examines the fundamental concepts that are essential for an understanding of the unique features of tellurium chemistry with an emphasis on hypervalency, three-centre bonding, secondary bonding interactions, σ and π-bond energies (multiply bonded compounds), and Lewis acid behaviour.

15.
Inorg Chem ; 54(6): 3043-54, 2015 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-25719213

RESUMO

A comprehensive investigation of reactions of alkali-metal derivatives of the ditelluro dianion [TePV(NtBu)(µ-NtBu)]22­ (L2­, E = Te) with p-block element halides produced a series of novel heterocycles incorporating P2VN2 rings, tellurium, and group 13­16 elements. The dianion engages in Te,Te'-chelation to the metal center in Ph2Ge and R2Sn (R = tBu, nBu, Ph) derivatives; similar behavior was noted for group 14 derivatives of L2­ (E = S, Se). In the case of group 13 trihalides MCl3 (M = Ga, In), neutral spirocyclic complexes (L)M[NtBu(Te)PV(µ-NtBu)2PIIIN(H)tBu)] (M = Ga, In) comprised of a Te,Te'-chelated ligand L2­ and a N,Te-bonded ligand resulting from loss of Te and monoprotonation were obtained. In reactions with RPCl2 (R = tBu, Ad, iPr2N) a significant difference was observed between Se- and S-containing systems. In the former case, Se,Se'-chelated derivatives were formed in high yields, whereas the N,S-chelated isomers predominated for sulfur. All complexes were characterized by multinuclear (1H, 31P, 77Se, 119Sn, and 125Te) NMR spectroscopy; this technique was especially useful in the analysis of the mixture of (L)(Se) and (L)(SeSe) obtained from the reaction of Se2Cl2 with L2­ (E = Te). Single-crystal X-ray structures were obtained for the spirocyclic In complex (9), (L)GePh2 (E = Te, 10), (L)SntBu2 (E = Te, 12a); E = Se, 12aSe, E = S, 12aS) and (L)(µ-SeSe) (E = Te, 16).

16.
Dalton Trans ; 44(12): 5338-46, 2015 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-25689801

RESUMO

Metathetical reactions of alkali-metal derivatives of the dianion [(t)BuN(Se)P(µ-N(t)Bu)2P(Se)N(t)Bu](2-) ((2Se2-)) with Ag(NHC)Cl, Ag[BF4], AuCl(THT) and HgCl2, as well as the reaction of 2S(2-) with AuCl(THT) were investigated. The observed products all incorporate the monoprotonated ligands 2SeH(-) or 2SH(-) in a variety of structural arrangements around the metal centres, including tetrameric and trimeric macrocycles [Ag and Au (E = Se)], a ladder (Au, E = S) and a spirocycle (Hg); the ladder contains both the dianion 2S(2-) and the monoanion 2SH(-) as ligands linking three Au2 units. All complexes have been characterised in the solid state by single crystal X-ray analyses and in solution by multinuclear ((1)H, (31)P and (77)Se) NMR spectra.

17.
Dalton Trans ; 44(19): 8781-3, 2015 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-25600404

RESUMO

Reactions of the dianion [Te((t)BuN)P(µ-N(t)Bu)2P(N(t)Bu)Te](2-) with I2 or [Cp*RhCl2]2 unexpectedly produced complexes of the novel spirocyclic Te5 dianion [{(t)BuN(Te)P(µ-N(t)Bu)2P(Te)N(t)Bu}2µ-Te](2-), which is N,N'-coordinated to two Na(+) ions in the disodium derivative and adopts a Te,Te',Te''-bonding mode in the Cp*Rh complex.

18.
Acta Crystallogr Sect E Struct Rep Online ; 70(Pt 1): o20-1, 2014 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-24526971

RESUMO

The title compound, C62H78N4P4Se2Si4·2C5H12, is made up of two [SeC(PPh2NSiMe3)(PPh2NHSiMe3)] units related by an inversion center situated at the mid-point of the diselenide bond. It crystallized with two disordered mol-ecules of pentane used as solvent of crystallization. It is a rare example of an anti-periplanar diselenide and exhibits a long Se-Se bond of 2.4717 (8) Å. The Se-C bond length of 1.876 (5) Šis short in comparison with the range of values found for other diselenides (1.91-1.97 Å). The mol-ecule exhibits two intra-molecular N-H⋯N hydrogen bonds. In the crystal, there are no significant inter-molecular inter-actions present. One of the Me3Si- groups is disordered over two positions with a refined occupancy ratio of 0.708 (8):0.292 (8). The contribution of the disordered solvent to the scattering was removed with the SQUEEZE option of PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155]. The solvent contribution has been included in the reported mol-ecular weight and density.

19.
Chemistry ; 20(3): 704-12, 2014 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-24415362

RESUMO

A new structural arrangement Te3 (RP(III) )3 and the first crystal structures of organophosphorus(III)-tellurium heterocycles are presented. The heterocycles can be stabilized and structurally characterized by the appropriate choice of substituents in Tem (P(III) R)n (m=1: n=2, R=OMes* (Mes*=supermesityl or 2,4,6-tri-tert-butylphenyl); n=3, R=adamantyl (Ad); n=4, R=ferrocene (Fc); m=n=3: R=trityl (Trt), Mesor by the installation of a P(V) 2 N2 anchor in RP(III) [TeP(V) (tBuN)(µ-NtBu)]2 (R=Ad, tBu).


Assuntos
Compostos Heterocíclicos/química , Compostos Organofosforados/química , Telúrio/química , Cristalografia por Raios X , Compostos Heterocíclicos/síntese química , Espectroscopia de Ressonância Magnética , Conformação Molecular
20.
Inorg Chem ; 52(13): 7791-804, 2013 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-23786389

RESUMO

The reaction of H2C(PCl2)2 with 4 equiv of (t)BuMgCl in tetrahydrofuran (THF) produces 1,4-(CH2)2(P(t)Bu)4, 1, in about 65% yield. This six-membered ring reacts directly with elemental sulfur or selenium in toluene at low temperatures to give the mono- and dichalcogenides 1,4-(CH2)2(P(t)BuE)(P(t)Bu)3 (E = S, 2a, E = Se, 2b) and 1,4-(CH2)2-2,5-(P(t)BuE)2(P(t)Bu)2 (E = S, 3a, E = Se, 3b). X-ray structural determinations showed that 3a and 3b are isostructural in the solid state; the six-membered C2P4 ring exhibits a twist-boat geometry with chalcogen substituents in syn positions in each case. Density functional theory (DFT) calculations for the three possible isomers of disubstitution were performed to elucidate the factors that favor the 2,5-isomer. Thermal isomerism was observed in solutions of 3b or 3a in toluene at 60 and 95 °C, respectively, to give the corresponding 2,6-isomers. With an excess of chalcogen in toluene at reflux, the four-membered rings (H2C)(P(t)BuE)2E (E = S, 4a, E = Se, 4b) were obtained and identified by multinuclear NMR spectroscopy and single crystal X-ray crystallography, which showed the (t)Bu groups in a trans orientation with respect to the CP2E ring. With a large excess of chalcogen, the five-membered rings (H2C)(P(t)BuE)2E2 (E = S, 5a, E = Se, 5b) were also observed; the X-ray structure of 5b revealed a half-envelope conformation for the CP2Se2 ring. The direct reaction of 4a with sulfur in boiling toluene does not produce 5a, whereas 5b is formed slowly and in low yields from 4b and selenium under similar conditions. On the basis of DFT calculations of the relative energies of likely intermediates, chalcogen insertion into the P-P bonds of 3a and 3b to give eight-membered C2P4E2 rings, followed by monomerization, is proposed as a feasible pathway for the formation of the four-membered CP2E heterocycles 4a and 4b.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA