三核钼簇合物的配基置换反应及{[Mo_3(μ_3—S)(μ—S)_3(dtp)_3(C_3H_4N_2)_3]~+(dtp)~-}·(CH_3)_2CO(Ⅰ)的合成和晶体结构

具有松散配位的三核钼簇合物[Mo_3(μ_3—S)(μ—S)_3(μ—dtp)(dtp)_3·(H_2O)](A)(dtp=S_2P(OC_2H_5)_2)和过量的咪唑反应时,(H_2O)配体和双啮桥基配体(dtp)可以同时被置换而形成标题化合物(Ⅰ)。晶体结构属三斜晶系,空间群P1。结构组成包括簇阳离子[Mo_3(μ_3—S)(μ—S)_3(dtp)_3·(C_3H_4N_2)_3],(dtp)阴离子及丙酮溶剂。簇阳离子具有近似C_3对称性,三个Mo原子基本上形成等边三角形,其Mo—Mo键长分别为2.763(1),2.762(1),和2.756(1),此簇合物是配体取代反应系列研究的产物之一,是由已知原子簇反应获得新型簇合物的一个例证。     

“松散”配位的三核钼簇化合物——Mo_3(μ_3-X)(μ-S)_3[S_2P(OEt)_2]_4·L(X=O,S或[(1/2)O+(1/2)S];L=H_2O,SC(NH_2)_2)

文献报道的三钼簇合物大多是配位对称的,而配位不对称的(包括配位空缺或称为配位不饱和的)在化学上更有意义,但报道甚少。最近我们合成了“松散”配位的三核钼簇合物若干个,其中簇合物{Mo_3(μ_3-S)(μ-S)_3[S_2P·(OEt)_2]_4(H_2O)}(1)和{Mo_3(μ_3-X)(μ-S)_3[S_2P·(OEt)_2]_4·SC(NH_2)_2}(2 X=1/2O+1/2S),已用X射线衍射法测定了晶体结构,发现不对称配位的Mo—L键较通常的长,显得“松散”,配基L可以被其他π-型中性配基置换,在化学上     

(d-p)π共轭作用对簇合物Mo_2S_4(dtp)_2和Mo_3S_4(dtp)_4·Py电子光谱的影响

比较了含有配位不饱和过渡金属原子簇合物Mo_2S_4(dtp)_2,(Ⅰ)和Mo_3S_4(dtp)_4·Py,(Ⅱ)的紫外—可见电子吸收光谱实验数据和半经验的量子化学方法INDO计算得到的电子跃迁能,讨论了(d-p)π型共轭作用对其电子吸收光谱位移的影响。结果表明,过渡金属簇合物中电子吸收光谱位移,与有机共轭体系有着类似的变化规律,即随着共轭π键数目增加,π-π电子跃迁的吸收光谱红移。     

Mo_4(μ_3-O)_2O_4Cl_2(O_2CC_6H_5)_6和Mo_4(μ_3-O)_2O_4Cl_2(O_2CC_6H_4CH_3)_6·2C_6H_5Cl簇合物中弱M—M键的研究

测定了Mo_4(μ_(3-)O)_2O_4Cl_2(O_2CC_6H_5)_6和Mo_4(μ_(3-)O)_2O_4Cl_2(O_2CC_6H_4CH_3)_6·2C_6H_5Cl四钼簇合物在N,N-二甲基甲酰胺溶液中的循环伏安特性、电子吸收光谱、固体粉末样品的表面光电压谱和光声光谱。讨论Mo_2(V)结构单元中弱M—M键的特性,认定了Mo—Mo键前线区域轨道的对称标号。     

四核钼簇合物的配体取代反应及产物Mo_4S_4(μ-OAc)_2(dtp)_4的晶体结构

标题化合物(Ⅰ)经由Mo_4S_4(μ-dtp)_4(Ⅱ)[dtp=S_2P(OEt)_2]和Ni(OAc)_2反应而得。(Ⅰ)晶体属单斜晶系,空间群P2/c,a=13.176(4),b=11.699(3),c=18.526(4)(?),β=116.11(3)°,V=2564(3)(?)~3,Z=2,D_c=1.776g·cm~(-3)。晶体结构由直接法解出,最终偏离因子R=0.085。本文结果表明,可由已知的四核钼簇合物经过配体置换反应,合成得到其簇骼中心[Mo_4S_4]保持不变并具有-OAc作为桥式配体和-dtp作为端基配体的混合配体类立方烷[Mo_4S_4]簇合物。     

三核钼簇合物配基置换反应: 两个三核钼簇合物[Mo3S4(DTC)4(DMF)](EtOH)和[Mo3S4(DTC)4(Py)](Py)2(H2O)的合成和晶体结构研究

通过配基置换反应合成出两个新的三核钼簇合物[Mo_3S_4(DTC)_4(DMF)](EtOH(1)和[Mo_3S_4-(DTC)_4(Py)](Py)_2(H_2O)(2)。用X射线衍射法测定了这两个簇合物的晶体结构。簇合物1的空间群为PI,晶胞参数:a=10.624(5),b=11.373(2),c=19.216(5)A;α=87.92(2),β=79.89(3),r=69.44(3);Z=2。簇合物2的空间群为PI,晶胞参数:a=11.505(2),b=11.945(1),c=18.974(2)A;α=99.18(1),β=94.82(1),r=93.84(1)°;Z=2。结构分析结果表明,两个簇合物的簇胳均是{Mo_3S_4}~(4+)的三核钼原子簇。对簇合物中配基对Mo-Mo键的影响以及配基置换反应的规律性进行了讨论。     

多中心d-pπ键与高氧化态钼簇合物的几何构型——(Ⅰ)“碎片结构”模型及分子轨道研究

本文通过对不同构型的二核钼簇合物簇胳结构的分子轨道计算,揭示了Mo—B(T)原子间的多中心d-p π键与该结构的稳定性及结构参数α、θ和R之间的内在联系,提出了2～6核高氧化态钼簇合物的簇胳由“碎片结构”组合而成的设想,该模型对以μ_2-S_2为桥的三核钼簇合物中的“共面—异面”规则和簇胳为[Mo_4S_3O]~(6+)的钼簇中的反常Mo—Mo键距给出合理解释,确认了桥原子对Mo—Mo键长和键强的决定作用。     

具有“松散”配位的三核钼簇合物的研究 {Mo_3(μ_3-X)(μ-S)_3[S_2P(OEt)_2]_4·SC(NH_2)_2}(X=1/2O+1/2S)的合成和结构测定

前文报道了簇合物{Mo_3(μ_3-S)(μ-S)_3[S_2P(OEt)_2]_4·H_2O}(1)的合成和结构,并指出了它的化学活泼性.当它与硫脲反应时,处在松散配位的H_2O被硫脲取代而成簇合物{Mo_3~-(μ_3-S)(μ-S)_3[S_2P(OEt)_2]_4·SC(NH_2)_2}(2),虽未得到适于X射线单晶结构测定用的晶体,但已为红外光谱的数据所证实.按本文合成方法所得簇合物经二氯甲烷-石油醚重结晶,得褐色针状单晶,结构分析表明为标题簇合物,μ_3桥原子由(1/2O+1/2S)统计占有.     

两个具有[Mo_3M′S_4]~(5+)(M′=Mo,W)簇芯的原子簇化合物的合成和晶体结构

以MO_3S_4(dtp)_4 H_2O和M′(CO)_6(M′=Mo,W)为起始物在核酸介质下通过[3+1]模式合成,分别得到一个同核和一个异核四核簇[Mo_4S_4(μ-C_2H_5CO_2)_2(dtP)_3]4和[Mo_3WS_4(μ-CH_3CO_2)_2(dtpH)(dtp)_3]5[dtp=(EtO)_2PS~-_2;dtpH=(EtO)_2P(S)(SH)] 两个簇合物以单晶X射线分析和IR谱学进行结构表征,它们均具有[M_4S_4]~(5+)类立方烷簇芯     

双核配合物组合合成Mo_nFe_(4-n)S_4单立方烷簇合物及Mo_2Fe_2S_4(C_4H_8dtc)_6·3.5C_2H_2Cl_4的结构

从含有M Fe(M=Mo,Fe)结构单元的双核配合物Mg(DMF)_6[Fe_2S_2Cl_4]及Mg(DMF)_6[FeCl_2·MoS_4]起始,经不同的组合反应,分别得到Fe_4S_4,MoFe_3S_4及Mo_2Fe_2S_4单立方烷簇合物。讨论了这一反应的某些特点并报道了双桥联六配体的Mo_2Fe_2S_4(C_4H_8dtc)_6的晶体与分子结构。     

Die Kristallstruktur des Komplexnitrides Mo(Ta,Mo)2N2

In the ternary system Ta/Mo/N a complex nitride of formula Mo(Ta,Mo)₂N₂ was observed at a nitrogen pressure of 360 bar and a temperature of 1,600°C. The crystal structure was determined from X-ray powder diagrams. The tetragonal unit cell, space groupI4/mmm-D _4h ¹⁷ , lattice parametersa=0.3051 nm,c=1.2530 nm contains ten atoms with an arrangement of the metal atoms corresponding to the MoSi₂-Type structure.

     

Metal–metal bond energies in Mo2, Mo2Cl,and Mo2(O2CH)4

Previous attempts to determine the strengths of multiple metal-metal bonds are reviewed. Estimates of 73 and 97 kcal/mole for the Mo? Mo bond energies in Mo₂Cl and Mo₂(O₂CH)₄, respectively, are obtained by combining the known experimental bond energy in Mo₂ (96.5 ± 5 kcal/mole) with the results of SCF-Xα-SW calculations on Mo₂, Mo₂Cl, and Mo₂(O₂CH)₄. Possible errors in the estimates are discussed. It is noted that the quadruple bonds in the complexes are predicted stronger per component than the sextuple bond in the diatomic.     

Rubidium dimolybdate,Rb2Mo2O7, and caesium dimolybdate,Cs2Mo2O7

The crystal structures of dirubidium hepta­oxodimolybdate, Rb₂Mo₂O₇, and dicaesium hepta­oxodimolybdate, Cs₂Mo₂O₇, in the space groups Ama2 and P2₁/c, respectively, have been determined for the first time by single‐crystal X‐ray diffraction. The structures represent two novel structure types of monovalent ion dimolybdates, A₂Mo₂O₇ (A = alkaline elements, NH₄, Ag or Tl). In the structure of Rb₂Mo₂O₇, Mo atoms are on a twofold axis, on a mirror plane and in a general position. One of the Rb atoms lies on a twofold axis, while three others are on mirror planes. Two O atoms attached to the Mo atom on a mirror plane are located on the same plane. Rubidium dimolybdate contains a new kind of infinite Mo–O chain formed from linked MoO₄ tetra­hedra and MoO₆ octa­hedra alternating along the a axis, with two terminal MoO₄ tetra­hedra sharing corners with each octa­hedron. The chains stack in the [001] direction to form channels of an approximately square section filled by ten‐coordinate Rb ions. Seven‐ and eight‐coordinate Rb atoms are located between chains connected by a c translation. In the structure of Cs₂Mo₂O₇, all atoms are in general positions. The MoO₆ octa­hedra share opposite corners to form separate infinite chains running along the c axis and strengthened by bridging MoO₄ tetra­hedra. The same Mo–O polyhedral chain occurs in the structure of Na₂Mo₂O₇. Eight‐ to eleven‐coordinate Cs atoms fill the space between the chains. The atomic arrangement of caesium dimolybdate has an ortho­rhom­bic pseudosymmetry that suggests a possible phase transition P2₁/c→Pbca at elevated temperatures.     

Die Kristallstruckturen von TiSi,Ti(Al,Si)2 und Mo(Al,Si)2

Zusammenfassung Es werden die Kristallstrukturen der Silicidphasen: TiSi, TiAl_0,3–0,6Si_1,7–1,4 und MoAl_1,3Si_0,7 ermittelt. TiSi ist mit der FeB-Struktur isotyp, wie bereits früher festgestellt wurde. Die Gitterparameter sind:a=6,53₁,b=3,63₁ undc=4,98₇ kX. E. Die Struktur TiAl_0,3–0,6Si_1,7–1,4 kann zum ZrSi₂-Typ gerechnet werden, ist aber pseudotetragonal:a=c=3,58₃–3,61₁ undb=13,49 kX. E. Neben Mo(Si,Al)₂ mit C 40-Typ besteht noch eine weitere Al-reichere, ternäre Kristallart MoAl_1,3Si_0,7 mit TiSi₂-Typ. Die Gitterparameter errechnen sich zu:a=8,23₉,b=4,78₃ undc=8,75₈ kX. E.     

Einfache Darstellungsmethoden des einzigen bekannten Perthiometallats [(S2)2 Mo(S2)2Mo(S2)2]2−. Zur Kenntnis der Einheit {Mo2(S2)2}6+

Simple Preparation Methods of the Only Known Perthiometallate [(S₂)₂(Mo)S₂)₂ Mo(S₂)₂]^2? · On the Moiety {Mo₂(S₂)₂}⁶⁺ Different aspects of the preparation of the only known perthiometallate [(S₂)₂Mo(S₂)₂Mo(S₂)₂]^2? (a compound with the unusual coordination number (9) have been discussed. Simple preparation methods could be developed. A discussion of the properties of the stabilising central moiety {Mo(S₂)₂}⁶⁺ containing a metal-metal bond follows.     

Thermal homolytic fission of the MoMo bond in (h5 -C5H5)2Mo2(CO)6

Kinetic studies of reactions of the MoMo bonded complex (h⁵-C₅H₅)₂Mo₂(CO)₆ in decalin show that it undergoes reversible homolytic fission and that the activation enthalpy required to break the MoMo bond is 135.9 ± 2.2 kJ mol^?1.     

双核钼(O)配合物[(C2H5)4N]2[Mo2(CO)8(SCH2CO2(C2H5)2]的合成, 结构, 光谱和反应性能研究

Et4NI,NaSCH2CO2C2H5和Mo(CO)6在乙腈中反应制得一种新的双核钼(0)配合物[Et4N]2-[Mo2(CO)8(SCH2CO2Et)2](1), 电化学和反应性能研究指出1在电位～-0.43V发生一有趣的双电子一步氧化, 产生[Mo2(CO)8(SCH2CO2Et)2], 若氧化反应在配位溶剂中进行, 则其部分羰基被配位溶剂分子所取代成为[Mo2(CO)6(SCH2CO2Et)2L2](L=CH3CN).在1中, Mo…Mo不存在金属键以及MoS2Mo核骨架完全不同于氧化的产物Mo(I)配合物. 这结果完全证实了双电子一步转移是由于双金属中心的金属-金属键的形成或断裂伴随桥联双金属中心结构的重排而产生的推断.     

Studies,on the synthesis,structure, IR spectra and reactivity of a new dinuclear Mo(0) complex, [Et4N]2[Mo2(CO)8(SCH2CO2Et)2]

Reaction of Et₄NI, NaSCH₂CO₂Et and Mo(CO)₆ in CH₃CN affords a new dinuclear molybdenum (0) complex, [Et₄N]₂[Mo₂(CO)₈(SCH₂CO₂Et)₂] (1). Electrochemistry and reactivity investigation indicate that 1 undergoes an interesting two-electron oxidation in a single step (-0.43 V) and a substitution of its carbonyls by coordinating solvents resulting in two kinds of Mo(I)-complexes, Mo₂(CO)₈(SCH₂CO₂Et)₂ and (Mo₂(CO)₆SCH₂CO₂Et)₂(CH₃CN)₂. vC=O and vMo-CO have been assigned. The crystal and molecular structure has been determined from three-dimensional X-ray data. 1 crystallized in the triclinic, space group with a=10.362(1), b=10.391(1), c= 10.815(2)Å; α=91.64(2)°, β=100.07(2)°, γ=114.46(1)°; Z=1; R=4.8% for 2975 reflections with I>3σ(I). Nonbonding of Mo … Mo [3.939(1)Å] and the configuration of MoS₂Mo unit in 1 are very different from those in related Mo(I)-product. These results confirm our previous speculation that the two-electron character derives from creation or cleavage of a metal-metal single bond coupled with structural rearrangement in a bridged bimetallic center.