氧族桥原子对类立方烷簇[Mo_4X_4Cp_4′]成键特征的影响(X=O,S,Se,Te;Cp′=Cp or Pr~iCp)

本文用EHMO法对(Mo_4X_4Cp′4](X=0,S,Se,Tc)四个类立方烷型簇合物的电子结构进行了计算,结果表明,桥基X从O到Te,前线区域分子轨道中桥基成分明显增加,能级普遍升高;Mo-Mo间作用有所增强;能隙ΔE(LUMO-HOMO)增大;Mulliken键级P的次序为P_(Mo-Se)>P_(Mo-S)>P_(Mo-Tc)>P_(Mo-o)>P_(Mo-Mo),说明第二过渡系元素Mo更倾向于与较重的se桥结合形成类立方烷型簇合物。     

[Fe4S4Cl4—n（S2CNEt2）n]^2—（n=0,1,2,4）：原子簇的电子结构研究

用CNDO/2(s,p,d)方法研究了类立方烷系列Fe-S簇合物[Fe_4S_4Cl_4(?)(S_2CNEt_2)_n]~(2-)(n=0,1,2,4)的电子结构。得出[S_2CN(Et)_2]-螯合配位Fe_4S_4~(2+)簇合物中存在两类不同价态铁原子的结论;骨架Fe_4S_4~(2+)中μ_3-S电子是非定域化的,同Mssbauer谱测定结果一致。讨论了簇合物Fe—Fe之间的成键作用、螫合配体的作用和氧化还原性质。     

钼铁混合金属原子簇的研究——Ⅰ.(η~5-C_5H_5)_2Mo_2Fe_2(μ_4-Te)(μ_3-Te)_2(CO)_6的合成和结构表征

本文用Fe_3(μ_3-Te)_2(CO)_9同Mo_2(CO)_6(η~5-C_5H_5)_2反应合成出标题化合物。结晶学参数如下:空间群Imm2,620个I≥2σ(I)的独立衍射参加最小二乘法修正结构,最终R因子值为0.022。X射线分析表明Mo_2Fe_2形成一蝴蝶型结构,其中两钼原子占据两蝴蝶翼的交界处,Mo—Mo=2.819。两个铁则处于蝴蝶翼的顶端,Mo—Fe=2.932(2)。每个钼原子与一个环成二烯基键联,三个羰基配体以端基的形式与每个铁原子键联。一碲原子处在蝴蝶型开口的上方键联四个金属原子,Mo—Te(μ_4)=2.625(2),Fe—Te(μ_4)=2.713(2)。两个μ_3-碲原子处在μ_4-Te原子的对面,分别处在二个FeMo_2三角面上,Mo—Te(μ_3)=2.678(1),Fe—Te(μ_3)=2.513(3)。整个分子具有严格的C_2v对称性,整个簇骼结构可看成双帽三角双锥构型。     

簇合物[Fe_6S_9(SCH_2CH_2OH)Cl]~(4-)的合成、结构和性质研究

将一定量的FeCl_2,(NH_4)_2MoS_4和HSCH_2CH_2OH在甲醇-甲醇钠溶剂中反应,制备出[(C_2H_5)_4N]_4[Fe_6S_9(SCH_2CH_2OH)Cl]单晶。该化合物属三斜晶系,P1空间群,a=12.818(4),b=13.622(3),c=18.328(7),α=106.09(2)°,β=100.75(2)°,γ=102.69(2)°,Z=2。对7517个可观测反射(1>3σ(Ⅰ))精修所有结构参数,得到一致性因子R=0.0818。结构测定结果表明:在[Fe_6S_9(SCH_2CH_2OH)Cl]~(4-)中存在着μ_2—S桥,μ_3—S桥和μ_4—S桥。该簇合物的核[Fe_6S_9]~(2-)由8个非共面的菱形组成。其中有4个Fe(μ_2—S)(μ_3—S)Fe,2个Fe(μ_2—S)(μ_4—S)Fe和2个Fe(μ_3—S)(μ_4—S)Fe菱形。用EHMO方法对簇合物电子结构进行了量子化学的研究。结构上键长表现出Fe—(μ_4—S)>Fe—(μ_3—S)>Fe—(μ_2—S)的规律,与EHMO计算得到键序Fe(μ_4—S)相似文献   

Nb_3X_4(X=S,Se,Te)的能带结构研究

固相过渡金属原子簇化合物Nb_3X_4(X=S,Se,Te)在低温下出现超导行为,且从S到Te,Nb_3X_4的超导转变温度Tc呈下降趋势。本文采用EHT近似下的紧束缚能带方法,计算了Nb_3X_4的能带结构。讨论其电子结构与超导电性的关系,并从化学键的观点出发对其Tc的递变加以解释。此外,本文还给出了Nb金属晶体的能带结构。     

Fe—S蛋白模型化合物的从头计算研究

对Fe_2s_2(SH)_4,Fe_4S_4(SH)_4各种氧化态的从头计算,得到了不同于以往文献报道的结果,结合实验,分析了端基S特性轨道处于前线位置,而以Fe的3d为主要成分的能级在较内层的合理性;讨论了不同氧化态活性位置与几何构型变化的原因;并初步探讨了在生物过程中,Fe—S蛋白作为电子载体的作用机制。     

五配位铁硫化合物(Et4N)4〔Fe2(S,X-C6H4-o)4〕的合成与晶体结构

利用无水FeCl与双齿配体Na_2BDT或Na_2MP(Na_2S,X-C,H_4-o_2:X=S,BDT;X=O,MP)在乙醇溶液中反应,然后加入沉淀剂Et_4NBr,可以得到双核铁硫化合物(Et_4N)_2[Fe_(S,X-CH_4-o)_4](1,X=S;2,X=0)。它们分别具有以双硫或双氧桥联起来的五配位扭曲三角双锥构型的铁原子。分子为心对称,核心Fe_2X_2~(2+)为平面。每个铁原子上的二个苯环平面A和B相互近于平行(1,二面角10.1°)或近于垂直(2,二面角100.2°);但铁原子与XSCC平面非共面。Fe原子离平面0.05～0.5A。2是第一个以双齿配位的双氧桥铁硫化合物,它既含有桥基氧原子又具有端基氧原子,对研究含氧配位的铁原子周围环境,为模拟固氧酶中的“P簇”,有一定意义。     

铁钼硫原子簇化合物的合成与结构研究 Ⅴ.[MoFe_3S_4]类立方烷簇合物的转化反应和[Et_4N]_3[Mo_2Fe_6S_8(SC_6H_4CH_(3-m))_3Cl_6]的晶体结构

具[MoFe_3S_4]类立方烷结构单元的双类立方烷化合物[Et_4N]_4[Mo_2Fe_7S_8(SR)_(12)](1a,R=Ph;1b,R=tolyl-m)或单类立方烷化合物[MoFe_3S_4(dtcR_2)_5](2a,R=Me;2b,R=Et)与酰氯在乙腈中反应,分别得到不含Fe桥的双类立方烷化合物(Et_4N)_3[Mo_2Fe_6S_8(SR)_3Cl_6](3a,R=Ph;3b,R=tolyl-m)与[MoFe_3S_4]骨架支解后的Fe(dtcR_2)_2Cl(4a,R=Me;4b,R=Et)。说明在相同反应条件下,[MoFe_3S_4]单元在1中比在2中稳定。本文首次将1型与3型结构通过一步化学反应连系起来。3型化合物的产生得到X射线衍射测定及~1H NMR谱的证实。本文报道3b的单晶结构及3的~1H NMR数据。3b属六方晶系,P6_3/m,a=1.6827(3),c=1.5951(16)nm;V=3.91158nm~3;D_c=1.491g/cm~3;Z=2;F(000)=1780;偏离因子R=0.048。化合物2与酰氯反应产生4,由红外及紫外可见光谱证实。     

含全双硫螯合配体簇合物的研究——Ⅱ.[Mo_2Fe_2(μ_3-S)_4(S_2CNEt_2)_5]·CH_3CN的合成、结构和性质

在无氧非水介质中,以(NH_4)_2MoS_4,FeCl_3和NaS_2CNEt_2为原料合成了簇合物 [Mo_2Fe_2S_4(S_2CNEt_2)_5]·CH_3CN.X射线单晶结构测定表明,它具有[Mo_2Fe_2S_4]~(5+)类立方烷核心骨架。每个金属原子有一螯合基团S_2CNEt_2配位。第五个S_2CNEt_2基团在两个Mo原子间跨桥配位。XPS和Mossbauer谱的测定及M-S(M=Fe或Mo)键长比较表明,簇合物中Fe原子的氧化态是不同的,而两个Mo原子则具有相同的氧化态。该簇合物为顺磁性物质,μ_m=4.27μ_B。此外,还测定了它的红外光谱,紫外-可见光谱和催化乙炔还原活性。     

过渡金属类立方烷型簇合物合成中的“活性元件组装”设想

本文讨论了Roussin黑盐的形成机理和“G”系模型物结构及其固氮活性成因的化学和量子化学研究结果。并由此提出了过渡金属类立方烷型簇合物合成中的“活性元件组装”设想;即过渡金属原子簇,特别是含μ2和μ3桥的类立方烷簇,可能由构成该原子簇的基本结构“元件”在一定活化条件下组装而成。考察了现有的Fe-S,Mo-S,Mo-Fe-S以及一些M-M′-X构型相类似的类立方烷簇合物,如[Fe_4S_4(SR)_4]~(2-),[MoFe_3S_4(SR)_n]~(m-),[VFe_3S_4Cl_3(DMF)3]单类立方烷簇,[Mo_2Fe_6S_9(SR)_8]~(8-),[Mo_2Fe_6S_8(SR)_9]~(3-),[Mo_2Fe_7S_8(SR)_(12)]~(3-,4-)桥联双立方烷簇以及(MeZn)_6Zn(OMe)_8孪合双立方烷簇的自兜合成反应,发现尽管它们似乎都是由简单的无机盐和有机配体“自兜”而成,然而它们都不能不经过某些“元件组装”的过程。提出了它们的可能的“元件组装”途径。此外还讨论了“元件组装在其他合成Mo、Fe、S类立方烷簇的反应中的存在。最后还进一步探讨了其他类型簇合物合成反应情况,表明“元件组装”设想是可能推广到类立方烷型簇以外的其他一些原子簇的合成的。     

Straightforward route to the adamantane clusters [Sn4Q10]4- (Q = S, Se, Te) and use in the assembly of open-framework chalcogenides (Me4N)2M[Sn4Se10] (M = Mn(II), Fe(II), Co(II), Zn(II)) including the first telluride member (Me4N)2Mn[Ge4Te10

The reaction of K(2)Sn(2)Q(5) (Q = S, Se, Te) with stoichiometric amounts of alkyl-ammonium bromides R(4)NBr (R = methyl or ethyl) in ethylenediamine (en) afforded the corresponding salts (R(4)N)(4)[Sn(4)Q(10)] (Q = S, Se, Te) in high yield. Although the compound K(2)Sn(2)Te(5) is not known, this reaction is also applicable to solids with a nominal composition "K(2)Sn(2)Te(5)" which in the presence of R(4)NBr in en are quantitatively converted to the salts (R(4)N)(4)[Sn(4)Te(10)] on a multigram scale. These salts contain the molecular adamantane clusters [Sn(4)Q(10)](4-) and can serve as soluble precursors in simple metathesis reactions with transition metal salts to synthesize the large family of open-framework compounds (Me(4)N)(2)M[Sn(4)Se(10)] (M = Mn(2+), Fe(2+), Co(2+), Zn(2+)). Full structural characterization of these materials as well as their magnetic and optical properties is reported. Depending on the transition metal in (Me(4)N)(2)M[Sn(4)Se(10)], the energy band gaps of these compounds lie in the range of 1.27-2.23 eV. (Me(4)N)(2)Mn[Ge(4)Te(10)] is the first telluride analogue to be reported in this family. This material is a narrow band gap semiconductor with an optical absorption energy of 0.69 eV. Ab initio electronic band structure calculations validate the semiconductor nature of these chalcogenides and indicate a nearly direct band gap.     

Synthesis,Structure, and Optical Properties of New Cadmium Chalcogenide Clusters of the Type [Cd10E4(E'Ph)12(PR3)4], (E,E' = Te,Se, S)

New cadmium chalcogenide cluster molecules [Cd₁₀E₄(E'Ph)₁₂(PⁿPr₃)₄], E = Te, E' = Te ( 1 ) and [Cd₁₀E₄(E'Ph)₁₂ (PⁿPr₂Ph)₄] E = Te, E' = Se ( 2 ); E = Te E' = S ( 3 ); E = Se, E' = S ( 4 ) have been synthesized and structurally characterized by single crystal X‐ray structure analysis. The influence of the variation of the chalcogen atom is investigated by structural means and by optical spectroscopy. All cluster‐molecules have a broad emission in the blue‐visible range at low temperature as indicated by photo luminescence (PL) measurements. A clear classification of the emission peak position can be made based on the E' species suggesting that the emission is assigned to transitions associated with the cluster surface ligands. Photoluminescence excitation and absorption measurements display a systematic shift of the band gap to the higher energies with the variation of E and E' from Te to Se to S, as also occurs in the respective series of the bulk semiconductors.     

Application of a universal force field to mixed Fe/Mo-S/Se cubane and heterocubane clusters. 1. Substitution of sulfur by selenium in the series [Fe4X4(YCH3)4]2-; X = S/Se and Y = S/Se

A series of Fe-S and Fe-Se cubane clusters containing all four combinations of the general formula [Fe(4)X(4)(Y-CH(3))(4)](2)(-) (X = S/Se, Y = S/Se) is investigated with FTIR and Raman spectroscopy. The terminally selenolate coordinated clusters (Y = Se) are prepared by a new synthetic route. All four cluster compounds are structurally characterized by X-ray single-crystal structure determination. Infrared and Raman spectra of all compounds are presented and interpreted with normal coordinate analysis. The corresponding force fields are based on that developed for the Fe(4)S(4)-benzyl cluster (Czernuszewicz, R. S.; Macor, K. A.; Johnson, M. K.; Gewirth, A.; Spiro, T. G. J. Am.Chem. Soc. 1987, 109, 7178-7187). An empirical procedure is presented to convert Fe-S into Fe-Se force constants. Only minor changes in force constants are found upon S --> Se exchange, reflecting the similarity of the Fe-S and Fe-Se bonds. The drastic frequency shifts in the metal-ligand region observed upon substitution of sulfur by selenium are, therefore, primarily due to the corresponding mass changes.     

Synthesis and characterization of Pd and Pt complexes of 1,3-bis(ferrocenylchalcogeno)propanes: crystal structures of FcSe(CH2)3SeFc and [M{FcE(CH2)3E'Fc}2](PF6)2 (M = Pd, Pt; E, E' = Se, Te; Fc = [Fe(eta5-C5H5)(eta5-C5H4)])

Reaction of a 1,3-bis(ferrocenylchalcogeno)propane, FcE(CH2)3E'Fc (L: E, E' = Se or Te; Fc = [Fe(eta5-C5H5)(eta5-C5H4)]), with a palladium(II) or platinum(II) precursor [M(NCMe)4](PF6)2 (M = Pd or Pt) in acetonitrile at room temperature led in good yield to the bis-chelate complexes [ML2](PF6)2. The structures of FcSe(CH2)3SeFc and all six complexes have been determined by X-ray crystallography. Electrochemical studies showed that electronic communication between ferrocenyl groups, absent in all three bis(ferrocenylchalcogeno)propanes, is established on complexation only for E = Se and E' = Se or Te, when the through-bond Fe...Fe distance is reduced to 13.17 A or less.     

Experimental and Theoretical Investigations of Structural Isomers of Dichalcogenoimidodiphosphinate Dimers: Dichalcogenides or Spirocyclic Contact Ion Pairs?

A synthetic protocol for the tert-butyl-substituted dichalcogenoimidodiphosphinates [Na(tmeda){(EPtBu(2))(2)N}] (3 a, E=S; 3 b, E=Se; 3 c, E=Te) has been developed. The one-electron oxidation of the sodium complexes [Na(tmeda){(EPR(2))(2)N}] with iodine produces a series of neutral dimers (EPR(2)NPR(2)E--)(2) (4 b, E=Se, R=iPr; 4 c, E=Te, R=iPr; 5 a, E=S, R=tBu; 5 b, E=Se, R=tBu; 5 c, E=Te, R=tBu). Attempts to prepare 4 a (E=S, R=iPr) in a similar manner produced a mixture including HN(SPiPr(2)). Compounds 4 b, 4 c and 5 a-c were characterised by multinuclear NMR spectra and by X-ray crystallography, which revealed two alternative structures for these dimeric molecules. The derivatives 4 b, 4 c, 5 a and 5 b exhibit acyclic structures with a central chalcogen-chalcogen linkage that is elongated by approximately 2 % (E=S), 6 % (E=Se) and 8 % (E=Te) compared to typical single-bond values. By contrast, 5 c adopts an unique spirocyclic contact ion-pair structure in which a [(TePtBu(2))(2)N](-) ion is Te,Te' chelated to an incipient [(TePtBu(2))(2)N](+) cyclic ion. DFT calculations of the relative energies of the two structural isomers indicate a trend towards increasing stability for the contact ion pair relative to the corresponding dichalcogenide on going from S to Se to Te for both the isopropyl and tert-butyl series. The two-electron oxidation of [Na(tmeda){(EPtBu(2))(2)N}] (E=S, Se, Te) with iodine produced the salts [(EPtBu(2))(2)N](+)X(-) (7 a, E=S, X=I(3); 7 b, E=Se, X=I; 7 c, E=Te, X=I), which were characterised by X-ray crystallography. Compound 7 a exists as a monomeric, ion-separated complex with [d(S--S)=2.084(2) A]; 7 b and 7 c are dimeric [d(Se--Se)=2.502(1) A; d(Te--Te)=2.884(1) A].     

Bonding preferences of C2X4-bridged bimetallic transition metal complexes of Ti, Cu, and Ag

The bonding preference of transition metal species of general formula [(PH3)2M]2(mu-C2X4), where M = Cu or Ag and X = O, S, Se, or Te, and (Cp2Ti)2(mu-C2X4), where X = S or Se, are explored using density functional theory. The relative energies of metal binding to the bridging ligand in a dithiolene-like vs dithiocarbamate-like manner are evaluated. In all cases, the most stable structure corresponds to dithiolene-like (or side-side) bonding, consistent with the vast majority of these compounds which have been experimentally characterized. However, for M = Ag and X = S, Se, or Te, the two isomers are nearly degenerate.     

Strukturen neuer SeII- und TeII-Komplexe mit 2,2-Dicyanethylen-1,1-dithiolat, 2,2-Dicyanethylen-1,1-thioselenolat und 2,2-Dicyanethylen-1,1-diselenolat

Structures of New Se^II and Te^II Complexes Containing 2,2-Dicyanethylene-1,1-dithiolate, 2,2-Dicyanethylene-1,1-thioselenolate, and 2,2-Dicyanethylene-1,1-diselenolate (NBu₄)₂{Se[S₂C?C(CN)₂]₂} ( I ), (AsPh₄)₂ · {Te[SSeC?C(CN)₂]₂} ( II ), and (NBu₄)₂{Te[Se₂C?C(CN)₂]₂} ( III ) containing the bidentate chelate ligands 2,2-dicyanethylene-1,1-dithiolate i-mnt , 2,2-dicyanethylene-1,1-thioselenolate i-mnts , and 2,2-dicyanethylene-1,1-diselenolate i-mns have been prepared and characterized by X-ray structure analysis. The central units consist of [M(X? X)₂E₂]^2? (M = Se, Te; X? X = ligand; E = lone-pair) with fourfold coordinated Se^II and Te^II, respectively. The complex anions [Se(i-mnt)₂E₂]^2? as well as [Te(i-mnts)₂E₂]^2? show a trapezoide distortion with d(Se? S) = 2.276(5); 2.287(5); 2.803(5); 2.789(5) Å and d(Te? Se) = 2.611(2); 2.617(3); d(Te? S) = 2.889(5); 2.935(4) Å. In III there are centrosymmetric complex anions [Te(i-mns)₂E₂]^2? with nearly identical Te? Se-bond-lengths: 2.674(3) and 2.692(2) Å. These Te? Se bonds are elongated compared to usual Te? Se bonds.     

Synthesis and reactions of cubane-type iron-sulfur-phosphine clusters,including soluble clusters of nuclearities 8 and 16

A family of soluble, reduced iron-sulfur clusters with nuclearities 4, 8, and 16 having tertiary phosphine ligation and based on the Fe(4)S(4) cubane-type structural motif has been synthesized. The results of this investigation substantially extend and improve the results of our original work on iron-sulfur-phosphine clusters (Goh, C.; Segal, B. M.; Huang, J.; Long, J. R.; Holm, R. H. J. Am. Chem. Soc. 1996, 118, 11844). A general property of this cluster family is facile phosphine substitution. The clusters [Fe(4)S(4)(PR(3))(4)](+) are precursors to monosubstituted [Fe(4)S(4)(PR(3))(3)X] (X = Cl-, RS-), homoleptic [Fe(4)S(4)(SR)(4)](3-), and all-ferrous monocubanes [Fe(4)S(4)(PR(3))(4)] (R = Pr(i), Cy, Bu(t); generated in solution). In turn, [Fe(4)S(4)(PPr(i)()(3))(3)(SSiPh(3))] and [Fe(4)S(4)(PPr(i)(3))(4)] can be transformed into the dicubanes [Fe(8)S(8)(PPr(i)()(3))(4)(SSiPh(3))(2)] and [Fe(8)S(8)(PPr(i)((3))(6)], respectively. Further, the tetracubanes [Fe(16)S(16)(PR(3))(8)] are also accessible from [Fe(4)S(4)(PR(3))(4)] under different conditions. X-ray structures are described for [Fe(4)S(4)(PCy(3))(3)X] (X = Cl-, PhS-), [Fe(8)S(8)(PPr(i)(3))(4)(SSiPh(3))(2)], [Fe(8)S(8)(PPr(i)()(3))(6)], and [Fe(16)S(16)(PCy(3))(8)]. The monosubstituted clusters show different distortions of the [Fe(4)S(4)](+) cores from idealized cubic symmetry. The dicubanes possess edge-bridged double cubane structures with an Fe(2)(mu(4)-S)(2) bridge rhomb and idealized C(2)(h)() symmetry. The ready cleavage of these clusters into single cubanes is considered a probable consequence of strained bond angles at the mu(4)-S atoms. Tetracubanes contain four individual cubanes, each of which is implicated in two bridge rhombs so as to generate a cyclic structure of idealized D(4) symmetry. Redox properties and M?ssbauer spectroscopic parameters are reported. The species [Fe(4)S(4)(PR(3))(4)] (in solution), [Fe(8)S(8)(PR(3))(6)], and [Fe(16)S(16)(PR(3))(8)] are the only synthetic all-ferrous clusters with tetrahedral iron sites that have been isolated. Their utility as precursors to other highly reduced iron-sulfur clusters is under investigation.