Unexpected Photodegradation of a Phosphaketenyl‐Substituted Germyliumylidene Borate Complex

The first zwitterionic borata‐bis(NHC)‐stabilized phosphaketenyl germyliumylidene [(L₂(O=C=P)Ge:] 2 (L₂=(p ‐tolyl)₂B[1‐(1‐adamantyl)‐3‐yl‐2‐ylidene]₂) has been synthesized by salt‐metathesis reaction of [L₂(Cl)Ge:] 1 with sodium phosphaethynolate [(dioxane)_n NaOCP]. Unexpectedly, its exposure to UV light affords, after reductive elimination of the entire PCO group, the unprecedented [L₂Ge‐GeL₂] complex 3 in 54 % yields bearing the Ge₂²⁺ ion with Ge in the oxidation state +1. In addition, the 1,3‐digermylium‐2,4‐diphosphacyclobutadiene [L₂Ge(μ‐P)₂GeL₂] 4 and bis(germyliumylidenyl)‐substituted diphosphene [(L₂Ge‐P=P‐GeL₂)] 5 could also be obtained in moderate yields. The formation of 3 – 5 and their electronic structures have been elucidated with DFT calculations.