Phosphorano-Stabilized Carbene Complexes with Short Thorium(IV)– and Uranium(IV)–Carbon Bonds

While no alkylidene
complexes of the f elements are known, the
use of phosphorano-stabilized carbene complexes to produce short actinide–carbon
bonds has been previously demonstrated. Complexes of the form, (C5Me5)2­An­(X)­(CHPPh3), with short thorium­(IV)– and uranium­(IV)–carbon­(carbene)
bonds have been synthesized from the reaction of (C5Me5)2­An­(X)­(CH3) (An =
Th, U; X = Cl, Br, or I) with the ylide, CH2​PPh3. The resulting uranium complexes feature the shortest uranium­(IV)–carbon
bonds reported to date. The molecular and electronic structure of
the thorium phosphorano-stabilized carbene complexes is detailed using
X-ray crystallography, 13C NMR spectroscopy, and density
functional theory calculations, and compared to thorium methandiide
complexes.

尽管目前尚未见f区元素的亚烷基配合物（alkylidene complexes）相关报道，但此前已有研究利用磷稳定化卡宾配合物（phosphorano-stabilized carbene complexes）成功构建了短锕系-碳键。通式为(C5Me5)₂An(X)(CHPPh₃)的配合物（其中C5Me5为五甲基环戊二烯基，An为锕系元素(An)），可由(C5Me5)₂An(X)(CH₃)（An=Th、U；X=Cl、Br或I）与叶立德(ylide) CH₂=PPh₃反应合成，其结构中含有短的四价钍-碳（卡宾(carbene)）键与四价铀-碳（卡宾(carbene)）键。所得到的铀基配合物拥有目前已报道的最短四价铀-碳键。本研究通过X射线晶体学(X-ray crystallography)、碳13核磁共振波谱法(13C NMR spectroscopy)与密度泛函理论(density functional theory)计算，对该类钍基磷稳定化卡宾配合物的分子与电子结构进行了详细解析，并与钍基亚甲基二负离子配合物(methandiide complexes)开展了对比研究。