Heavy Metalla Vinyl-Cations show Metal-Lewis Acid Cooperativity in Reaction with Small Molecules (NH3, N2H4, H2O, H2)
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][BArF4] [E =Ge (3), Sn (4)] and [Ar*EIrH(PMe3)3][BArF4] [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 a Ir=E double bond and a near linear coordination at the Ge/Sn atoms. Cationic complexes 3 and 4 oxidatively add NH3, N2H4, H2O, HCl∙Et2O, and H2 selectively to give: [TbbGe(NH2)IrH2(PMe3)3][BArF4] (5), [TbbE(NHNH2)IrH2(PMe3)3][BArF4] [E = Ge (7), Sn(8)], [TbbE(OH)IrH2(PMe3)3][BArF4] [E = Ge (9), Sn(10)], [TbbE(Cl)IrH2(PMe3)3][BArF4] [E = Ge (11a), Sn(12a)], [TbbGe(H)IrH2(PMe3)3][BArF4] (13), [TbbSn(µ-H3)Ir(PMe3)3][BArF4] (14), and [TbbSnHIrH2(PMe3)3][BArF4] (15). 14 isomerizes to give 15 via 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 1,2H-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.