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)2 B[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 [L2 Ge-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 [L2 Ge(μ-P)2 GeL2 ] 4 and bis(germyliumylidenyl)-substituted diphosphene [(L2 Ge-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.