There is continued burgeoning interest in metal–metal multiple bonding to further our understanding of chemical bonding across the periodic table. However, although polar covalent metal–metal multiple bonding is well known for the d and p blocks, it is relatively underdeveloped for actinides. Homometallic examples are found in spectroscopic or fullerene-confined species, and heterometallic variants exhibiting a polar covalent σ bond supplemented by up to two dative π bonds are more prevalent. Hence, securing polar covalent actinide double and triple metal–metal bonds under normal experimental conditions has been a fundamental target. Here we exploit the protonolysis and dehydrocoupling chemistry of the parent dihydrogen-antimonide anion, to report one-, two- and three-fold thorium–antimony bonds, thus introducing polar covalent actinide–metal multiple bonding under normal experimental conditions between some of the heaviest ions in the periodic table with little or no bulky-substituent protection at the antimony centre. This provides fundamental insights into heavy element multiple bonding, in particular the tension between orbital-energy-driven and overlap-driven covalency for the actinides in a relativistic regime.

人们对金属-金属多重键合的兴趣持续增长，以进一步加深我们对元素周期表中化学键合的理解。然而，尽管极性共价金属-金属多重键合对于d和p嵌段而言是众所周知的，但对于锕系元素来说，它相对不发达。同金属的例子存在于光谱或富勒烯限制的物种中，并且表现出极性共价σ键并辅以最多两个配位π键的异金属变体更为普遍。因此，在正常实验条件下确保极性共价锕系金属双键和三键金属-金属键一直是一个基本目标。在这里，我们利用母体二氢锑阴离子的质子解和脱氢偶联化学，报告一、二和三重钍-锑键，从而在正常实验条件下在一些最重的钍-锑键之间引入极性共价锕系元素-金属多重键合。元素周期表中锑中心很少或没有大取代基保护的离子。这提供了对重元素多重键合的基本见解，特别是相对论状态下锕系元素的轨道能量驱动和重叠驱动的共价之间的张力。