Cremer Christian, Burger Peter
Anorg.-chem. Institut, Universität Zürich, Switzerland.
Chemistry. 2003 Aug 4;9(15):3583-96. doi: 10.1002/chem.200204330.
A series of novel dinuclear tungsten(IV) oxo complexes with disubstituted 4,4'-R,R-2,2'-bipyridyl (R(2)bpy) ligands of the type [(CpW(R(2)bpy)(mu-O))(2)]PF(6) (R=NMe(2), tBu, Me, H, Cl) was prepared by hydrolysis of the tungsten(IV) trichloro complexes [CpW(R(2)bpy)Cl(3)]. Cyclic voltammetry measurements for the tungsten(IV) oxo compounds provided evidence for one reversible oxidation and two reversible reductions leading to the oxidation states W(V)W(IV), W(IV)W(III) and W(III)W(III). The corresponding complexes (Cp*W(R(2)bpy)(mu-O))(2) PF(6) (n=0 for R=Me, tBu, and 1, 3 for both R=Me) could be isolated after chemical oxidation/reduction of the tungsten(IV) oxo complexes. The crystal structures of the complexes [(CpW(R(2)bpy)(mu-O))(2)]BPh(4) (R=NMe(2), tBu) and (Cp*W(Me(2)bpy)(mu-O))(2)PF(6) (n=0, 1, 2, 3) show a cis geometry with a puckered W(2)O(2) four-membered ring for all compounds except [(CpW(Me(2)bpy)(mu-O))(2)] which displays a trans geometry with a planar W(2)O(2) ring. Examining the interaction of these novel tungsten oxo complexes with protons, we were able to show that the W(IV)W(IV) complexes [(CpW(R(2)bpy)(mu-O))(2)]PF(6) (-) (R=NMe(2), tBu) undergo reversible protonation, while the W(III)W(III) complexes [(CpW(R(2)bpy)(mu-O))(2)] transfer two electrons forming the W(IV)W(IV) complex and molecular hydrogen.
通过三氯钨（IV）配合物[CpW（R₂bpy）Cl₃]的水解反应，制备了一系列具有二取代4,4'-R，R-2,2'-联吡啶（R₂bpy）配体的新型双核钨（IV）氧代配合物[(CpW（R₂bpy）（μ-O）)₂][PF₆]₂（R = NMe₂、tBu、Me、H、Cl）。对钨（IV）氧代化合物进行循环伏安法测量，结果表明存在一个可逆氧化过程和两个可逆还原过程，分别生成氧化态为W（V）W（IV）、W（IV）W（III）和W（III）W（III）的产物。在对钨（IV）氧代配合物进行化学氧化/还原后，可以分离得到相应的配合物[(CpW（R₂bpy）（μ-O）)₂]ⁿ⁺[PF₆]ⁿ（R = Me、tBu时n = 0；R = Me时n = 1、3）。配合物[(CpW（R₂bpy）（μ-O）)₂][BPh₄]₂（R = NMe₂、tBu）和[(CpW（Me₂bpy）（μ-O）)₂]ⁿ⁺[PF₆]ⁿ（n = 0、1、2、3）的晶体结构表明，除了[(CpW（Me₂bpy）（μ-O）)₂]呈现平面W₂O₂环的反式几何构型外，所有化合物均具有带褶皱W₂O₂四元环的顺式几何构型。通过研究这些新型钨氧代配合物与质子的相互作用，我们发现W（IV）W（IV）配合物[(CpW（R₂bpy）（μ-O）)₂][PF₆⁻]₂（R = NMe₂、tBu）会发生可逆质子化，而W（III）W（III）配合物[(CpW（R₂bpy）（μ-O）)₂]会转移两个电子，形成W（IV）W（IV）配合物和分子氢。
