Mononuclear (Pd, Pt), heterodinuclear (PdAg, PtAg), and tetranuclear (Pd2Ag2, Pt2Ag2) 1,1-ethylenedithiolato complexes

lp;&-5q;1 The reactions of [Tl2[S2C=C[C(O)Me]2]]n with [MCl2L2] (1:1) or with [MCl2(NCPh)2] and PPh3 (1:1:2) give complexes [M[eta2-S2C=C[C(O)Me]2]L2] [M = Pt, L2 = 1,5-cyclooctadiene (cod) (1); L2 = bpy, M = Pd (2a), Pt (2b), L = PPh3, M = Pd (3a), Pt (3b)] whereas with MCl2 and QCl (2:1:2) anionic derivatives Q2[M[eta2-S2C=C[C(O)Me]2]2] [M = Pd, Q = NMe4 (4a), Ph3P=N=PPh3 (PPN) (4a'), M = Pt, Q = NMe4 (4b)] are produced. Complexes 1 and 3 react with AgClO4 (1:1) to give tetranuclear complexes [[ML2]2Ag2[mu2,eta2-(S,S')-[S2C=C[C(O)Me]2]2]](ClO4)2 [L = PPh3, M = Pd (5a), Pt (5b), L2 = cod, M = Pt (5b')], while the reactions of 3 with AgClO4 and PPh3 (1:1:2) give dinuclear [[M(PPh3)2][Ag(PPh3)2][mu2,eta2-(S,S')-S2C=C[C(O)Me]2]]]ClO4 [M = Pd (6a), Pt (6b)]. The crystal structures of 3a, 3b, 4a, and two crystal forms of 5b have been determined. The two crystal forms of 5b display two [Pt(PPh3)2][mu2,eta2-(S,S')-[S2C=C[C(O)Me]2]2] moieties bridging two Ag(I) centers.     

手性3,5-二甲基-2-芳基-2-吗啉醇盐酸盐的合成及其晶体结构

以(S)-2-氨基丙醇为手性源与α-溴-3-氯苯丙酮反应, (R)-2-氨基丙醇为手性源与6-甲氧基-2-(2-溴丙酰基)萘反应, 分别合成了手性纯化合物(2R,3R,5S)-3,5-二甲基-2-(3-氯苯基)-2-吗啉醇盐酸盐(4a)和(2S,3S,5R)-3,5-二甲基-2-(6-甲氧基-2-萘基)-2-吗啉醇盐酸盐(4b), 利用X射线单晶衍射仪测定了两化合物的晶体结构和两化合物的空间结构, 并初步分析两化合物空间结构, 化合物4a晶体属正交晶系, 空间群为P2₁2₁2, 晶胞参数为: a＝0.8718(2) nm, b＝0.7883(2) nm, c＝2.0247(6) nm, Z＝4, V＝1.3915(7) nm³, D_c＝1.328 g/cm³, F(000)＝584, R₁＝0.0399, wR₂＝0.0797, S＝1.042. 化合物4b晶体属正交晶系, 空间群为P2₁2₁2₁, 晶胞参数为: a＝0.71035 (9) nm, b＝0.77703(10) nm, c＝2.9820(4) nm, Z＝4, V＝1.6318(4) nm³, D_c＝1.318 g/cm³, F(000)＝688, R₁＝0.0520, wR₂＝0.1108, S＝0.994.     

四氢糠酸的拆分工艺改进

利用非对映异构体盐在溶剂中溶解度的不同,以(1S,2R)-1-氨基-2-茚醇(1)为手性拆分剂,拆分四氢糠酸［(RS)-THFA, (RS)-2］获得高光学纯的(S)-2,其结构经¹H NMR, ¹³C NMR和HPLC确证。探究了不同溶剂量和投料比对拆分效果的影响。结果表明较佳拆分条件为：以4-甲基-2-戊酮(3)作溶剂,n［(RS)-2］: n(1)=2.2 : 1,一次拆分得91.7% ee (S)-2;再以n［91.7% ee (S)-2］: n(1)=6 : 5进行二次拆分得99.0% ee (S)-2。拆分剂的回收率提高至92.0%,同时对拆分母液中的非目标对映体成功地进行消旋化,回收率为89.0%,实现了四氢糠酸的循环拆分。     

Lipase-catalyzed resolution of (2R*,3S*)- and (2R*,3R*)-3-methyl-3-phenyl-2-aziridinemethanol at low temperatures and determination of the absolute configurations of the four stereoisomers

[reaction: see text] Lipase-catalyzed resolution of (2R*,3S*)-3-methyl-3-phenyl-2-aziridinemethanol, (+/-)-2, at low temperatures gave synthetically useful (2R,3S)-2 and its acetate (2S,3R)-2a with (2S)-selectivity (E = 55 at -40 degrees C), while a similar reaction of (2R*,3R*)-3-methyl-3-phenyl-2-aziridinemethanol, (+/-)-3, gave (2S,3S)-3 and its acetate (2R,3R)-3a with (2R)-selectivity (E = 73 at -20 degrees C). Compound (+/-)-2 was prepared conveniently via diastereoselective addition of MeMgBr to tert-butyl 3-phenyl-2H-azirine-2-carboxylate, (+/-)-1a, which was successfully prepared by the Neber reaction of oxime tosylate of tert-butyl benzoyl acetate 7a. The tert-butyl ester was requisite to promote this reaction. For determination of the absolute configuration of (2S,3R)-2a, enantiopure (2S,3R)-2 was independently prepared in three steps involving diastereoselective methylation of 3-phenyl-2H-azirine-2-methanol, (S)-10, with MeMgBr. The absolute configuration of (2S,3S)-3 was determined by X-ray analysis of the corresponding N-(S)-2-(6-methoxy-2-naphthyl)propanoyl derivative (S,S,S)-13.     

Volume-based thermodynamics: estimations for 2:2 salts

The lattice energy of an ionic crystal, U(POT), can be expressed as a linear function of the inverse cube root of its formula unit volume (i.e., Vm(-1/3)); thus, U(POT) approximately 2I(alpha/Vm(1/3) + beta), where alpha and beta are fitted constants and I is the readily calculated ionic strength factor of the lattice. The standard entropy, S, is a linear function of Vm itself: S approximately kVm + c, with fitted constants k and c. The constants alpha and beta have previously been evaluated for salts with charge ratios of 1:1, 1:2, and 2:1 and for the general case q:p, while values of k and c applicable to ionic solids generally have earlier been reported. In this paper, we obtain alpha and beta, k and c, specifically for 2:2 salts (by studying the ionic oxides, sulfates, and carbonates), finding that U(POT)[MX 2:2]/(kJ mol(-1)) approximately 8(119/Vm(1/3) + 60) and S degree [MX 2:2]/(J K(-1) mol(-1)) approximately 1382V(m) + 16.     

The molecular and electronic structure of the electron transfer series [Fe2(NO)2(S2C2R2)3](z) (z = 0, -1, -2; R = phenyl, p-tolyl, p-tert-butylphenyl)

Three dinuclear (nitrosyl)iron complexes containing three 1,2-di(phenyl)ethylene-1,2-dithiolate ligands have been prepared ([Fe2(NO)2(S2C2R2)3]0 (R = phenyl, 1a; p-tolyl, 2a; (4-tert-butyl)phenyl, 3a)). Each of these compounds represents the first member of a three-membered electron-transfer series: [Fe2(NO)2(S2C2R2)3]z (z = 0, -1, , -2). The salt [Co(Cp)2][Fe2(NO)2(L3)3] has also been isolated. The molecular structures of 2a and 3a have been determined by X-ray crystallography. Both neutral complexes contain two nearly linear FeNO units, one of which is S,S'-coordinated to two dithiolene ligands yielding a square-based pyramidal Fe(NO)S4 polyhedron; the second FeNO moiety forms two (micro2-S)-bridges to the first unit and is S,S'-coordinated to a third dithiolate radical yielding also a square-based pyramidal Fe(NO)S4 polyhedron. The electronic structures of the neutral, monoanionic, and dianionic species have been elucidated spectroscopically (UV-vis, IR, EPR, M?ssbauer): [[FeII(NO+)](L*)[FeII(NO)](L)2]0 (S = 0); [[FeII(NO)](L*)[FeII(NO)](L)2]1- (S = 1/2); and [[FeII(NO)](L)[FeII(NO)](L)2]2- (S = 0), where (L)2- represents the corresponding closed-shell dithiolate dianion and (L*)- is its monoanionic radical.     

Mechanism for Solvent Exchange on trans-[Os(en)(2)(eta(2)-H(2))S](2+)

Solvent exchange on trans-[Os(en)(2)(eta(2)-H(2))S](2+) (S = H(2)O, CH(3)CN) has been studied in neat solvent as a function of temperature and pressure by (17)O NMR line-broadening and isotopic labeling experiments (S = H(2)O) and by (1)H NMR isotopic labeling experiments (S = CH(3)CN). Rate constants and activation parameters are as follows for S = H(2)O and CH(3)CN, respectively: k(ex)(298) = 1.59 +/- 0.04 and (2.74 +/- 0.03) x 10(-)(4) s(-)(1); DeltaH() = 72.4 +/- 0.5 and 98.0 +/- 1.4 kJ mol(-)(1); DeltaS() = +1.7 +/- 1.8 and +15.6 +/- 4.9 J mol(-)(1) K(-)(1); DeltaV() = -1.5 +/- 1.0 and -0.5 +/- 1.0 cm(3) mol(-)(1). The present investigation of solvent exchange when compared with a previous study on substitution reactions on the same complexes leads to the conclusion that substitution reactions on these compounds undergo an interchange dissociative, I(d), or dissociative, D, reaction mechanism, where solvent dissociation is the rate-limiting step.     

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.     

New strontium polysulfides, SrS3, and Sr2(OH)2S4.10H2O, obtained by the high-pressure treatment of a Sr-S mixture

A new polymorph of SrS(3) was obtained by a reaction of SrS and S with an atomic ratio of Sr:S = 1:5 under a pressure of 5 GPa at 1200 degrees C. It crystallized in a tetragonal unit cell with a = 6.708(1) A, c = 3.942(1) A, and V = 177.36(6) A(3). It was isotypic with BaS(3), and contained S3(2-) polysulfide ions. The product obtained from the high-pressure synthesis contained an amorphous component. It was highly deliquescent and formed a yellowish solution. A new layered polysulfide, Sr(2)(OH)(2)S(4).10H(2)O, crystallized in the solution. The sulfide belonged to a triclinic space group of P (No. 2) with lattice constants of a = 5.9107(5) A, b = 7.8682(6) A, c = 9.4134(6) A, alpha = 75.639(6) degrees, beta = 73.824(3) degrees, gamma = 71.639(3) degrees, V = 392.83(5) A(3), and Z = 1. Each Sr ion was coordinated with one OH ligand and eight H(2)O ligands. Six H(2)O ligands out of the eight were bridging ligands to form two-dimensional [Sr(2)(OH)(2)(H(2)O)(10)(2+)]( infinity ) cationic layers, between which S4(2-) tetrapolysulfide ions were situated. The S4(2-) anion had a coplanar configuration with a dihedral angle of 180.0 degrees. The stability of S4(2-) anions having different conformations was discussed from a viewpoint of ab initio MO calculations on changing the dihedral angles of S4(2-).     

Synthesis, crystal structure, and magnetic studies of oxo-centered trinuclear chromium(III) complexes: [Cr(3)(mu(3)-O)(mu(2)-PhCOO)(6)(H(2)O)(3)]NO(3). 4H(2)O.2CH(3)OH, a case of spin-frustrated system, and [Cr(3)(mu(3)-O)- (mu(2)-PhCOO)(2)(mu(2)-OCH(2)CH(3))(2)(bpy)(2)(NCS )(3)], a new type of [Cr(3)O] core

The synthesis, crystal structure, and magnetic properties of two trinuclear oxo-centered carboxylate complexes are reported and discussed: [Cr3(mu3-O)(mu2-PhCOO)6(H2O)3]NO3.4H2O.2CH3OH (1) and [Cr3(mu3-O)(mu2-PhCOO)2(mu2-OCH2CH3)2(bpy)2(NCS)3] (2). For both complexes the crystal system is monoclinic, with space group C2/c for 1 and P1/n for 2. The structure of complex 1 consists of discrete trinuclear cations, associated NO3- anions, and lattice methanol and water molecules. The structure of complex 2 is built only by neutral discrete trinuclear entities. The most important feature of 2 is the unusual skeleton of the [Cr3O] core due to the lack of peripheral bridging ligands along one side of the triangular core, which is unique among the structurally characterized (mu3-oxo)trichromium(III) complexes. Magnetic measurements were performed in the 2-300 K temperature range. For complex 1, in the high-temperature region (T > 8 K), experimental data could be satisfactorily reproduced by using an isotropic exchange model, H = -2J12S1S2 - 2J13S1S3 - 2J23S2S3 (J12 = J13 = J23) with Jij = -10.1 cm(-1), g = 1.97, and TIP = 550 x 10(-6) emu mol(-1). The antisymmetric exchange interaction plays an important role in the magnetic behavior of the system, so in order to fit the experimental magnetic data at low temperature, a new magnetic model was used where this kind of interaction was also considered. The resulting fitting parameters are the following: Gzz = 0.25 cm(-1), delta = 2.5 cm(-1), and TIP = 550 x 10(-6) emu mol(-1). For complex 2, the experimental data could be satisfactorily reproduced by using an isotropic exchange model, H = -2J1(S1S2 + S1S3) - 2J2(S2S3) with J1 = -7.44 cm(-1), J2 = -51.98 cm(-1), and g = 1.99. The magnetization data allows us to deduce the ground term of S = 1/2, characteristic of equilateral triangular chromium(III) for complex 1 and S = 3/2 for complex 2, which is confirmed by EPR measurements.     

Regioselective ring opening of amino epoxides with nitriles: an easy synthesis of (2R,3S)- and (2S,3S)-1,3-diaminoalkan-2-ols with differently protected amine functions

[reaction: see text] Transformation of enantiopure (2R,1'S)- or (2S,1'S)-2-(1-aminoalkyl)epoxides 1 or 2 into the corresponding (2R,3S)- and (2S,3S)-1,3-diaminoalkan-2-ols 3 or 4 is described. The opening of the epoxide ring with different nitriles (Ritter reaction) takes place with total selectivity and in high yields in the presence of BF3.Et2O. Interestingly, the two amine groups are differently protected. A mechanism to explain this transformation is proposed.     

Kinetics of the reactions between [S(2)MoS(2)Cu(SC(6)H(4)R-4)](2-)(R = MeO, H, Cl or NO(2)) and CN(-): substitution mechanism at a 3-coordinate Cu(I) site

The kinetics of the reaction between [S(2)MoS(2)Cu(SC(6)H(4)R-4)](2-)(R = MeO, H, Cl or NO(2)) and CN(-) to form [S(2)MoS(2)CuCN](2-) have been studied in MeCN using stopped-flow spectrophotometry. In all cases, the rate law is of the form, Rate ={k+k(2)(R)[CN(-)]}[S(2)MoS(2)Cu(SC(6)H(4)R-4)(2-)]. It is proposed that both k and k correspond to associative substitution mechanisms. The k pathway involves attack by CN(-) at the copper site followed by dissociation of the thiolate. The k pathway involves attack of the solvent (MeCN) at the copper site, followed by dissociation of the thiolate to form [S(2)MoS(2)Cu(NCMe)](-). Subsequent rapid substitution of the coordinated solvent by cyanide produces [S(2)MoS(2)CuCN](2-). The evidence that both the k and k pathways involve associative mechanisms are: (i) the 4-R-substituent on the thiolate ligand has a similar effect on both k and k, with electron-withdrawing 4-R-substituents facilitating substitution; (ii) both the k and k pathways are associated with similar activation parameters (for k(1)(H): DeltaH++ = 5.5 +/- 0.5 kcal mol(-1), DeltaS++ = -23.9 +/- 2.0 cal deg(-1) mol(-1); for k(2)(H): DeltaH++ = 2.3 +/- 0.5 kcal mol(-1), DeltaS++ = - 23.9 +/- 2.0 cal deg(-1) mol(-1)) and (iii) addition of C(6)H(5)S(-) results in a similar increase in both k and k.     

[(CH_3)_4N]_2Na[Mo_2O(S_2)_3S_5]·H_2O的合成和晶体结构

标题晶体属斜方晶系,空间群Pbn2_1,a=9.086(2),b=13.439(3),c=22.858(11),V=2791,Z=4,Dc=1.927g/cm~3。在CAD—4衍射仪上收集强度数据,采用直接法和Fourier技术解出结构,并用全矩降最小二乘法修正。对于1180个独立衍射最终偏离因子0.067。结构中的阴离子与其同系物[(CH_3)_4-N]_2K(Mo_2O(S_2)_3(NO)_2]·H_2O中的阴离子配位情况相似。只是结构中的Mo—S与Mo—O键长有差异。这种差异在两者的红外光谱上有着相应的表现。     

Topochemical anion metathesis routes to the Zr2N2S phases and the Na2S and ACl derivatives (A = Na,K, Rb)

Anion metathesis reactions between ZrNCl and A(2)S (A = Na, K, Rb) in the solid state follow three different pathways depending on reaction temperature and reactant stoichiometry: (1) the reaction of ZrNCl with A(2)S in the 2:1 stoichiometry at 800 degrees C/72 h/in vacuo yields alpha-Zr(2)N(2)S with the expected layered structure of La(2)O(2)S. Above 850 degrees C, alpha-Zr(2)N(2)S (P3 macro m1; a = 3.605(1) A, c = 6.421(3) A) neatly transforms to beta-Zr(2)N(2)S (P6(3)/mmc: a = 3.602(1) A, c = 12.817(1) A). The structures of the alpha- and beta-forms are related by an a/2 shift of successive Zr(2)N(2) layers. (2) The same reaction at low temperatures (300-400 degrees C) yields ACl intercalated phases of the formula A(x)Zr(2)N(2)SCl(x) (0 < x < approximately 0.15), where alkali ions are inserted between the S/Cl.S/Cl van der Waals gap of a ZrNCl-type structure. The S and Cl ions are disordered and the c lattice parameters are alkali dependent (R3 macro m, a approximately 3.6 A, c approximately 28.4 (Na), 28.9 (K), and 30.5 A (Rb). A(x)Zr(2)N(2)SCl(x) phases are hygroscopic and reversibly absorb water to give monohydrates. (3) Reaction of ZrNCl with excess A(2)S at 400-1000 degrees C gives A(2)S intercalated phases of the formula A(2)(x)Zr(2)N(2)S(1+)(x) (0 < x < 0.5), where the alkali ions reside between the S.S van der Waals gap of a ZrNCl type structure (R3 macro m, a approximately 3.64 A, c approximately 29.48 A). Structural characterization of the new phases and implications of the results are described.     

Toward the development of a structurally novel class of chiral auxiliaries: diastereoselective aldol reactions of a (1R,2S)-ephedrine-based 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one

[reaction: see text] Asymmetric aldol addition reactions have been conducted with (1R,2S)-ephedrine-derived 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one (2). Diastereoselectivities range from 75:25 to 99:1 for the formation of the crude non-Evans syn adducts 8a-h. The facial selectivity of the enolate is directed by the stereogenic N(4)-methyl substituent. Aldol adduct 8a is readily cleaved by acid hydrolysis to afford (2S,3S)-3-hydroxy-2-methyl-3-phenylpropionic acid (9) in >95% ee.     

Incorporation of a new type of transition metal complex into the thioarsenate anion: syntheses, structures, and properties of two novel compounds [Mn3(2,2'-bipy)3(AsVS4)2]n.nH2O and Mn2(2,2'-bipy)As2IIIS5

The incorporation of [Mn(2,2'-bipy)2]2+ with thioarsenate resulted in the formation of two novel compounds, [Mn3(2,2'-bipy)3(As(V)S4)2]n.nH2O (1) and Mn2(2,2'-bipy)As2(III)S5 (2), in which the main-group chalcogenide framework is incorporated with a [tm(2,2'-bipy)m]n+ complex. Meanwhile, the tetrathioarsenate(V) anion acts as a new mu3-1kappaS:1,2kappaS':2,3kappaS":3kappaS'" ligand in 1, in which all four S atoms of the [As(V)S4]3- anion are coordinating to metal. As a result, the two compounds exhibit semiconducting properties (Eg = 2.18 eV (1) and 1.83 eV (2)) and strong blue photoluminescence, with the emission maximum occurring at about 440 nm. Magnetic measurements show that both compounds have AF ordered states with Néel temperatures of 19 and 24 K for 1 and 2, respectively.     

Synthesis and Chemical and Electrochemical Characterization of Fe-S Carbonyl Clusters. X-ray Crystal Structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)

A reinvestigation of the redox behavior of the [Fe(3)(&mgr;(3)-S)(CO)(9)](2)(-) dianion led to the isolation and characterization of the new [Fe(5)S(2)(CO)(14)](2)(-), as well as the known [Fe(6)S(6)(CO)(12)](2)(-) dianion. As a corollary, new syntheses of the [Fe(3)S(CO)(9)](2)(-) dianion are also reported. The [Fe(5)S(2)(CO)(14)](2)(-) dianion has been obtained by oxidative condensation of [Fe(3)S(CO)(9)](2)(-) induced by tropylium and Ag(I) salts or SCl(2), or more straightforwardly through the reaction of [Fe(4)(CO)(13)](2)(-) with SCl(2). The [Fe(6)S(6)(CO)(12)](2)(-) dianion has been isolated as a byproduct of the synthesis of [Fe(3)S(CO)(9)](2)(-) and [Fe(5)S(2)(CO)(14)](2)(-) or by reaction of [Fe(4)(CO)(13)](2)(-) with elemental sulfur. The structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)] were determined by single-crystal X-ray diffraction analyses. Crystal data: for [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)], monoclinic, space group P2(1)/c (No. 14), a = 24.060(5), b = 14.355(6), c = 23.898(13) ?, beta = 90.42(3) degrees, Z = 4; for [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)], monoclinic, space group C2/c (No. 15), a = 34.424(4), b = 14.081(2), c = 19.674(2) ?, beta = 115.72(1) degrees, Z = 4. The new [Fe(5)S(2)(CO)(14)](2)(-) dianion shows a "bow tie" arrangement of the five metal atoms. The two Fe(3) triangles sharing the central Fe atom are not coplanar and show a dihedral angle of 55.08(3) degrees. Each Fe(3) moiety is capped by a triply bridging sulfide ligand. The 14 carbonyl groups are all terminal; two are bonded to the unique central atom and three to each peripheral iron atom. Protonation of the [Fe(5)S(2)(CO)(14)](2)(-) dianion gives reversibly rise to the corresponding [HFe(5)S(2)(CO)(14)](-) monohydride derivative, which shows an (1)H-NMR signal at delta -21.7 ppm. Its further protonation results in decomposition to mixtures of Fe(2)S(2)(CO)(6) and Fe(3)S(2)(CO)(9), rather than formation of the expected H(2)Fe(5)S(2)(CO)(14) dihydride. Exhaustive reduction of [Fe(5)S(2)(CO)(14)](2)(-) with sodium diphenyl ketyl progressively leads to fragmentation into [Fe(3)S(CO)(9)](2)(-) and [Fe(CO)(4)](2)(-), whereas electrochemical, as well as chemical oxidation with silver or tropylium tetrafluoroborate, in dichloromethane, generates the corresponding [Fe(5)S(2)(CO)(14)](-) radical anion which exhibits an ESR signal at g = 2.067 at 200 K. The electrochemical studies also indicated the existence of a subsequent one-electron anodic oxidation which possesses features of chemical reversibility in dichloromethane but not in acetonitrile solution. A reexamination of the electrochemical behavior of the [Fe(3)S(CO)(9)](2)(-) dianion coupled with ESR monitoring enabled the spectroscopic characterization of the [Fe(3)S(CO)(9)](-) radical monoanion and demonstrated its direct involvement in the generation of the [Fe(5)S(2)(CO)(14)](n)()(-) (n = 0, 1, 2) system.     

From acetylene complexes to vinylidene structures: The GeC2H2 system

The expansion of germanium chemistry in recent years has been rapid. In anticipation of new experiments, a systematic theoretical investigation of the eight low lying electronic singlet GeC₂H₂ stationary points is carried out. This research used ab initio self‐consistent‐field (SCF), coupled cluster (CC) with single and double excitations (CCSD), and CCSD with perturbative triple excitations [CCSD(T)] levels of theory and a variety of correlation–consistent polarized valence cc‐pVXZ and cc‐pVXZ‐DK (Douglas‐Kroll) (where X = D, T, and Q) basis sets. At all levels of theory used in this study, the global minimum of the GeC₂H₂ potential energy surface (PES) is confirmed to be 1‐germacyclopropenylidene ( Ge‐1S ). Among the eight singlet stationary points, seven structures are found to be local minima and one structure ( Ge‐6S ) to be a second‐order saddle point. For the seven singlet minima, the energy ordering and energy differences (in kcal mol^?1, with the zero‐point vibrational energy corrected values in parentheses) at the cc‐pVQZ‐DK (Douglas‐Kroll) CCSD(T) level of theory are predicted to be 1‐germacyclopropenylidene ( Ge‐1S ) [0.0 (0.0)] < vinylidenegermylene ( Ge‐3S ) [13.9 (13.5)] < ethynylgermylene ( Ge‐2S ) [17.9 (14.8)] < Ge ‐ 7S [37.4 (33.9)] < syn‐3‐germapropenediylidene ( Ge‐8S ) [41.2 (37.9)] < germavinylidenecarbene ( Ge‐5S ) [66.6 (61.6)] < nonplanar germacyclopropyne ( Ge‐4S ) [67.8 (63.3)]. These seven isomers are all well below the dissociation limit to Ge (³P) + C₂H₂( ¹Σ). This system seems particularly well poised for matrix isolation infrared (IR) experiments. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Mild and efficient functionalization at C6 of purine 2'-deoxynucleosides and ribonucleosides

[reaction: see text] Treatment of sugar-protected inosine and 2'-deoxyinosine derivatives with a cyclic secondary amine or imidazole and I(2)/Ph(3)P/EtN(i-Pr)(2)/(CH(2)Cl(2) or toluene) gave quantitative conversions into 6-N-(substituted)purine nucleosides. S(N)Ar reactions with 6-(imidazol-1-yl) derivatives gave 6-(N, O, or S)-substituted products. The 6-(benzylsulfonyl) group underwent S(N)Ar displacement with an arylamine at ambient temperature.