Synthesis and Structures of Complexes Demonstrating the Coordinative Versatility of the 2,4-Diimino-3-phosphinopentene Anion (γ-Phosphino-β-diketiminate)

The synthesis and characterization of a 2,4-diimino-3-phosphinopentene anion (γ-phosphino-β-diketiminate) is reported and enables diversification of the β-diketiminate ligand framework, which has been widely employed across the periodic table. Phosphines are observed to adopt the γ-position of the ligand rather than the N,N‘ chelate. While aluminum and lithium adopt the familiar N,N‘ chelate arrangement with the new 2,4-diimino-3-phosphinopentene anion ligand, reactions with AsCl₃ or SbCl₃ result in substitution at the β-methyl position on the ligand backbone, realizing novel P→E (E = As or Sb) intramolecular coordination. The chemistry of the 2,4-diimino-3-phosphinopentene anion can be monitored by the ³¹P NMR chemical shifts, which are distinctively diagnostic of the coordinative engagement of the ligand.