Sodium phosphaethynolate as P-source for the synthesis of molecular rhodium phosphides: an exploratory study

Molecular transition metal phosphides (TMPs) containing a Rh₂P₂ and unprecedented Rh₄P₄ core could be generated from Na[OCP] and rhodium(I) precursor complexes carrying the bischelating tropPPh₂ ligand. These reaction proceed through a formal P-transfer step (trop = 5H-dibenzo[a,d]cyclohepten-5-yl), which involves migration of the CO unit to the Rh(I) center. With the related tetradentate ligand trop₃P and tridentate ligand trop₂PPh the first neutral and anionic [Rh_x(L)_n(PCO)_y]_z complexes containing up to two rhodium centers and three intact phosphaethynolate units. These complexes are inert against CO migration. The results demonstrate a large influence of the metal coordination sphere on product formation, and indicate that low-coordinate rhodium(I) precursors are most effective for the preparation of RhP complexes using Na[OCP] as P-source.