Unveiling the Bonding Scenario in Metal–Aryne Complexes with EDA-NOCV Analyses

Transition metal-based organometallic compounds have
been explained
by the Dewar–Chatt–Duncanson (DCD) model, established
in 1953, which provides a conceptual framework elucidating the interaction
between transition metals and ligands. This interaction involves σ-donation
from the ligand to the symmetric vacant d-orbital of the transition
metal (TM⃖L), coupled with π-backdonation from a distinctly
occupied d-orbital of the transition metal to the suitable empty orbital
(mostly antibonding type) on the ligand (TM → L), which leads
to the variations in bond lengths in the bonded ligand (typically
bond elongation) and vibrational frequencies within ligand bonds (such
as C=O, N=N, and C=C of olefins), serving as an indicator of the ligand’s
π-accepting strength. One such effective and highly reactive
ligand is benzyne/aryne, which is generated in situ and has been stabilized by coordinating to a transition metal. The
transition metal–aryne complexes are primarily formed with
low-valent early transition metals and late (d10) transition
metals. The findings, on employing the EDA-NOCV calculations of different
classical textbook examples of experimentally synthesized mononuclear
TM–aryne complexes, specifically TM–benzyne complexes,
reveal intriguing deviations from the original DCD model and suggest
that the bonding interaction of these well-known organometallic complexes
occurs between TM and aryne fragments in their ‘electronically
charged doublet states’ (as TM+ and aryne–). Notably, when the TM resides within groups IV–IX of the
periodic table, the interaction exhibits one dative σ-bond,
one electron-sharing π-bond, and one (a few have two) additional
dative σ/π bond (D + E). Even though late TM (d10, Ni/Pd/Pt) exhibits the potential to form both dative bonds (D)
(in accordance with the DCD model) and D + E interaction between electronically
charged fragments, it still slightly favors the later bonding scenario.
The major contribution in the bond formation of TM–aryne complexes
is from electrostatic interaction energy (ΔEelstat) and the major contribution toward the orbital
interaction (ΔEorb) is dominated
by the electron sharing π-bond formation.

基于过渡金属的有机金属化合物，其结构已通过德乌尔-查特-邓肯森（Dewar–Chatt–Duncanson，简称DCD）模型得到阐释，该模型建立于1953年，为理解过渡金属与配体之间的相互作用提供了一个概念框架。该相互作用涉及配体向过渡金属（TM）对称空d轨道的σ捐赠（TM⃖L），以及过渡金属（TM）一个明确占据的d轨道向配体适当空轨道（多为反键型）的π回捐（TM → L），这一过程导致了键长（通常为键伸长）以及配体键（如烯烃中的C=O、N=N和C=C）振动频率的变化，这些变化可作为配体π接受能力的指示。其中一种有效且高度活泼的配体是苯炔/芳炔，它通过原位生成并通过与过渡金属配位得到稳定。过渡金属-芳炔配合物主要与低价的早期过渡金属和晚期（d10）过渡金属形成。通过采用EDA-NOCV计算不同经典教科书中的实验合成的单核TM-芳炔配合物实例，特别是TM-苯炔配合物，我们发现这些已知有机金属化合物的键合相互作用发生在其“电子充电双态”的TM和芳炔片段之间（作为TM+和芳炔-）。值得注意的是，当TM位于周期表的IV至IX族时，该相互作用表现出一个配位σ键，一个电子共享π键，以及一个（少数为两个）额外的配位σ/π键（D + E）。尽管晚期TM（d10，Ni/Pd/Pt）根据DCD模型具有形成配位键（D）和电子充电片段之间的D + E相互作用的潜力，但它仍然略微偏向于后一种键合场景。在TM-芳炔配合物的键形成中，主要的贡献来自于静电相互作用能（ΔEelstat），而轨道相互作用的主要贡献则由电子共享π键的形成所主导。