Low-coordinate zero-valent metal species are implicated as key intermediates in various transition-metal-catalyzed and -mediated reactions. However, knowledge on this type of metal species has been mainly restricted to the metals in groups 8–10, and that on the earlier transition-metal analogs is very limited. Herein, we report three-coordinate formal Mn(0) complexes [(NHC)Mn(η²:η²-dvtms)] (NHC = N-heterocyclic carbene, dvtms = divinyltetramethyldisiloxane). Spectroscopic and computational studies established that these formal Mn(0) complexes have an S = 3/2 ground-spin state and feature strong metal-to-alkene π backdonation. As a result of the high covalency of the metal-ligand bonding, these formal Mn(0) complexes are best described as resonance among a series of limiting canonical structures of Mn(0)-dvtms, Mn(II)-[dvtm]^2–, and Mn(IV)-[dvtms]^4–. These formal Mn(0) complexes can perform reductive coupling with unsaturated hydrocarbons and show diversified reactivity toward H₂O, H₂, CO, and I₂, which hint at the synthetic utility of the three-coordinate formal Mn(0) species.

低配位的零价金属物种被认为是各种过渡金属催化和介导的反应中的关键中间体。但是，关于这类金属种类的知识主要限于第8-10组中的金属，而有关较早的过渡金属类似物的知识则非常有限。在本文中，我们报道三坐标正式锰（0）配合物[（NHC）的Mn（η ²：η ² -dvtms）]（NHC = Ñ -杂环卡宾，dvtms =二乙烯基四）。光谱和计算研究确定这些形式的Mn（0）配合物具有S = 3/2基态自旋态，并具有强力的金属到烯烃π返配。由于金属-配体键的高共价性，这些形式的Mn（0）配合物最好描述为Mn（0）-dvtms，Mn（II）-[dvtm] ²的一系列限制性正则结构之间的共振^–和Mn（IV）-[dvtms] ^4–。这些形式的Mn（0）配合物可以与不饱和烃进行还原偶联，并且对H ₂ O，H ₂，CO和I ₂表现出多样化的反应性，这暗示了三坐标形式的Mn（0）物种的合成效用。