Heavy metalla vinyl-cations show metal–Lewis acid cooperativity in reaction with small molecules (NH3, N2H4, H2O, H2)

Abstract

Halide abstraction from tetrylidene complexes [TbbE(Br)IrH(PMe₃)₃] [E = Ge (1), Sn (2)] and [Ar*E(Cl)IrH(PMe₃)₃] gives the salts [TbbEIrH(PMe₃)₃][BAr^F₄] [E = Ge (3), Sn (4)] and [Ar*EIrH(PMe₃)₃][BAr^F₄] [E = Ge (3′), E = Sn (4′)] (Tbb = 2,6-[CH(SiMe₃)₂]₂-4-(t-Bu)C₆H₂, Ar* = 2,6-Trip₂C₆H₃, Trip = 2,4,6-triisopropylphenyl). Bonding analysis suggests their most suitable description as metalla-tetrela vinyl cations with an IrE double bond and a near linear coordination at the Ge/Sn atoms. Cationic complexes 3 and 4 oxidatively add NH₃, N₂H₄, H₂O, HCl, and H₂ selectively to give: [TbbGe(NH₂)IrH₂(PMe₃)₃][BAr^F₄] (5), [TbbE(NHNH₂)IrH₂(PMe₃)₃][BAr^F₄] [E = Ge (7), Sn (8)], [TbbE(OH)IrH₂(PMe₃)₃][BAr^F₄] [E = Ge (9), Sn (10)], [TbbE(Cl)IrH₂(PMe₃)₃][BAr^F₄] [E = Ge (11a), Sn (12a)], [TbbGe(H)IrH₂(PMe₃)₃][BAr^F₄] (13), [TbbSn(μ-H₃)Ir(PMe₃)₃][BAr^F₄] (14), and [TbbSn(H)IrH₂(PMe₃)₃][BAr^F₄] (15). 14 isomerizes to give 15via an 1,2-H shift reaction. Hydride addition to cation 3 gives a mixture of products [TbbGeHIrH(PMe₃)₃] (16) and [TbbGeIrH₂(PMe₃)₃] (17) and a reversible 1,2-H shift between 16 and 17 was studied. In the tin case 4 the dihydride [TbbSnIrH₂(PMe₃)₃] (18) was isolated exclusively. The PMe₃ and PEt₃ derivatives, 18 and [TbbSnIrH₂(PEt₃)₃] (19), respectively, could also be synthesized in reaction of [TbbSnH₂]⁻ with the respective chloride [(R₃P)_nIrCl] (R = Me, n = 4; R = Et, n = 3). Reaction of complex 19 with CO gives the substitution product [TbbSnIrH₂(CO)(PEt₃)₂] (20). Further reaction with CO results in hydrogen transfer from the iridium to the tin atom to give [TbbSnH₂Ir(CO)₂(PEt₃)₂] (21). The reversibility of this ligand induced reductive elimination transferring 20 to 21 is shown.