Phosphanyl-substituted π-excess σ2P heterocycles: Coordination behaviour of 2-di-tert-butylphosphanyl-1-neopentyl-1,3-benzazaphosphole towards CuCl, HgCl2 and [Rh(COD)2]BF4

Reaction of the heterocyclic –PC(PtBu2)–N– hybrid ligand 1 with CuCl or HgCl2 in THF provided the metal complexes 2 and 3. The crystal structure analysis showed dimeric η1-phosphanyl and μ-chloro-coordinated species with the dicoordinated P-atom remote from the metal. In solution broadened phosphorus resonances are observed indicating low kinetic stability and ligand exchange reactions. The reaction of 1 with [Rh(COD)2]BF4 was much slower, required heating and led finally to the four-membered dihydrobenzazaphosphole Rh(COD) P⁁P′-chelate complex 4. The initial Rh(COD)+ complex proved very labile and added moisture traces at the PC bond, whereas the free ligand is stable to aqueous acids and bases.