Catalytic Addition of Terminal Alkynes to Carbodiimides by Half-Sandwich Rare Earth Metal Complexes

The catalytic addition of terminal alkynes to carbodiimides has been achieved for the first time by use of half-sandwich rare earth metal complexes, such as {Me2Si(C5Me4)(NPh)}Y(CH2SiMe3)(THF)2, which offers a straightforward, atom-economic route to the N,N‘-disubstituted propiolamidines which contain a conjugated C−C triple bond, a new family of amidines which were difficult to prepare by other means. A rare earth metal amidinate species was confirmed to be a true catalytic species in this process, thus demonstrating for the first time that an amidinate unit, though being often used as an ancillary ligand for various organometallic complexes, can itself participate in a catalytic reaction under appropriate conditions.

本研究首次利用半夹心型稀土金属配合物（half-sandwich rare earth metal complexes，示例为{Me2Si(C5Me4)(NPh)}Y(CH2SiMe3)(THF)2）实现了端炔（terminal alkynes）对碳二亚胺（carbodiimides）的催化加成反应。该反应为制备含共轭碳碳三键（conjugated C−C triple bond）的N,N'-二取代丙炔脒（N,N‘-disubstituted propiolamidines）提供了一条简便且原子经济（atom-economic）的合成路径，这类化合物是一类难以通过其他手段制备的新型脒类家族成员。研究证实，稀土金属脒基物种是该反应的真实催化活性物种，这首次证明了尽管脒基单元常被用作各类有机金属配合物的辅助配体（ancillary ligand），但在适宜条件下其自身也可参与催化反应。