From a Phosphaketenyl‐Functionalized Germylene to 1,3‐Digerma‐2,4‐diphosphacyclobutadiene

The first 4π‐electron resonance‐stabilized 1,3‐digerma‐2,4‐diphosphacyclobutadiene [L H 2 Ge 2 P 2 ] 4 (L H =CH[CHNDipp] 2 Dipp=2,6‐ i Pr 2 C 6 H 3 ) with four‐coordinate germanium supported by a β‐diketiminate ligand and two‐coordinate phosphorus atoms has been synthesized from the unprecedented phosphaketenyl‐functionalized N‐heterocyclic germylene [L H Ge‐P=C=O] 2 a prepared by salt‐metathesis reaction of sodium phosphaethynolate (P≡C−ONa) with the corresponding chlorogermylene [L H GeCl] 1 a . Under UV/Vis light irradiation at ambient temperature, release of CO from the P=C=O group of 2 a leads to the elusive germanium–phosphorus triply bonded species [L H Ge≡P] 3 a , which dimerizes spontaneously to yield black crystals of 4 as isolable product in 67 % yield. Notably, release of CO from the bulkier substituted [L tBu Ge‐P=C=O] 2 b (L tBu =CH[C( t Bu) N ‐Dipp] 2 ) furnishes, under concomitant extrusion of the diimine [Dipp‐NC( t Bu)] 2 , the bis‐N,P‐heterocyclic germylene [DippNC( t Bu)C(H)PGe] 2 5 .