Geometrically Enforced Donor-Facilitated Dehydrocoupling Leading to an Isolable Arsanylidine-Phosphorane

A proximate Lewis
basic group facilitates the mild dehydrogenative
P–As intramolecular coupling in the phosphine-arsine peri-substituted
acenaphthene 3, affording thermally and hydrolytically
stable arsanylidine-phosphorane 4 with a sterically accessible
two-coordinate arsenic atom. The formation of 4 is thermoneutral
due to the dehydrogenation being concerted with the donor coordination.
Reaction of 4 with a limited amount of oxygen reveals
arsinidene-like reactivity via formation of cyclooligoarsines, supporting
the formulation of the bonding in 4 as base-stabilized
arsinidene R3P→AsR.

邻近的路易斯碱基团(Lewis basic group)可促进温和条件下的脱氢型分子内P-As偶联反应，该反应发生于连有膦胂取代基的peri位取代苊(acenaphthene)3中，最终得到热稳定且水解稳定的胂亚基-磷叶立德(arsanylidine-phosphorane)4，该产物含有空间可及的两配位砷原子。化合物4的生成过程为热中性反应，这是因为脱氢步骤与供体配位过程协同进行。将化合物4与有限量氧气反应时，可通过生成环低聚胂(cyclooligoarsines)展现出类胂宾(arsinidene)反应活性，该结果佐证了化合物4的成键方式为碱稳定化胂宾R3P→AsR的论断。