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

Abstract

The first 4π-electron resonance-stabilized 1,3-digerma-2,4-diphosphacyclobutadiene [LH2Ge2P2] 4 (LH=CH[CHNDipp]2 Dipp=2,6-iPr2C6H3) 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 [LHGe-P=C=O] 2 a prepared by salt-metathesis reaction of sodium phosphaethynolate (P≡C−ONa) with the corresponding chlorogermylene [LHGeCl] 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 [LHGe≡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 [LtBuGe-P=C=O] 2 b (LtBu=CH[C(tBu)N-Dipp]2) furnishes, under concomitant extrusion of the diimine [Dipp-NC(tBu)]2, the bis-N,P-heterocyclic germylene [DippNC(tBu)C(H)PGe]2 5.