Synthesis and Hydrogenation of Heavy Homologues of Rhodium Carbynes: [(Me P) (Ph P)Rh≡E-Ar*] (E=Sn, Pb).

Tetrylidynes [(Me P) (Ph P)Rh≡SnAr*] (10) and [(Me P) (Ph P)Rh≡PbAr*] (11) are accessed for the first time via dehydrogenation of dihydrides [(Ph P) RhH SnAr*] (3) and [(Ph P) RhH PbAr*] (7) (Ar*=2,6-Trip C H , Trip=2,4,6-triisopropylphenyl), respectively. Tin dihydride 3 was either synthesized in reaction of the dihydridostannate [Ar*SnH ] with [(Ph P) RhCl] or via reaction between hydrides [(Ph P) RhH] and  [(Ar*SnH) ]. Homologous lead hydride [(Ph P) RhH PbAr*] (7) was synthesized analogously from [(Ph P) RhH] and  [(Ar*PbH) ]. Abstraction of hydrogen from 3 and 7 supported by styrene and trimethylphosphine addition yields tetrylidynes 10 and 11. Stannylidyne 10 was also characterized by Sn Mössbauer spectroscopy. Hydrogenation of the triple bonds at room temperature with excess H gives the cis-dihydride [(Me P) (Ph P)RhH PbAr*] (12) and the tetrahydride [(Me P) (Ph P)RhH SnH Ar*] (14). Complex 14 eliminates spontaneously one equivalent of hydrogen at room temperature to give the dihydride [(Me P) (Ph P)RhH SnAr*] (13). Hydrogen addition and elimination at stannylene tin between complexes 13 and 14 is a reversible reaction at room temperature.