双核钨簇合物W_2Cl_4(OR)_4(ROH)_2结构的EXAFS研究

Structural Research of the Cluster Compounds of W_2Cl_4(OR)_4(ROH)_2 by EXAFS

我们曾用EXAFS和X射线单晶衍射研究了M_3W_2Cl_9类双钨簇合物的结构,发现簇胳[W_2Cl_9]^(3-)的结构很牢固,改变阳离子M^+的性质和大小,都不会改变其结构。W_2Cl_9(RO)_4(R′OH)_2类簇合物与M_3W_2Cl_9类似,具有一个双钨簇胳。Anderson等曾研究R为甲基或乙基的两个簇合物的单晶结构,正四价的两个钨原子间用双键及两个氧桥键相联接。与M_3W_2Cl_9另一不同处是取代基RO及R′OH与钨原子直接相联,其间还形成氢键,故RO或R′OH对簇胳的影响要大于M_3W_2Cl_9中阳离子M^+。本文合成6种具有不同取代基的W_2Cl_4·(RO)_4(ROH)_2化合物,用EXAFS研究其结构,以期了解不同取代基对簇胳结构的影响。

Five cluster compounds of double tungsten nucleus W2Cl4(OR)4(ROH)2 have been investigated by EXAFS in which R- is Pr-, n-Bu, i-Bu, sec-Bu and n-Oct respcctivily. An in-lab EXAFS spectrometer-FXAS was used to collect the data of W LI edges. The backscattering amplitudes and the phase shifts of W, Cl and O atoms were obtained from the standard W2Cl4(OCH3)4(CH3OH)2. The structural parameters of the clusters from the curve fitting are listed. The conclusion is that the structures of cluster nucleus of the five compounds do not obviously change with the change of the size and the structure of the group--OR in the compounds. The structural stability results from the double bond and two bridge oxygen bonds between the two tungsten atoms.