Synthesis and Reactivity of the Labile Dihydrogen Complex [{MeC(CH(2)PPh(2))(3)}Ir(H(2))(H)(2)]BPh(4)

The novel Ir(III) nonclassical tetrahydrido complex [(triphos)Ir(H(2))(H)(2)]BPh(4) (4BPh(4)) has been prepared by hydrogenation of the ethene dihydride complex [(triphos)Ir(C(2)H(4))(H)(2)]BPh(4) in either the solid state (P(H)()2 >/= 1 atm) or CH(2)Cl(2) solution (P(H)()2 >/= 3 atm) [triphos = MeC(CH(2)PPh(2))(3)]. Complex 4BPh(4)()()is very labile in solution and can be isolated in the solid state exclusively from solid-gas reactions. Characterization of 4BPh(4) in solution can be achieved( )()by high-pressure NMR and IR spectroscopies, however. Various deuterated isotopomers of [(triphos)Ir(H(2))(H)(2)](+) have been obtained in CD(2)Cl(2) solution at low temperature by treatment of the trihydride [(triphos)IrH(3)] with DOSO(2)CF(3). On the basis of a variety of NMR experiments, the complex cation [(triphos)Ir(H(2))(H)(2)](+) is assigned an octahedral structure where two terminal hydride ligands and a dihydrogen molecule are trans to the phosphorus atoms of a facial triphos ligand. Complex 4BPh(4)()()dissolves in THF at room temperature yielding [(triphos)IrH(3)], BPh(3), and benzene; a similar reaction occurs in acetone, whereas in CH(2)Cl(2) the complex loses H(2) converting to the dimers cis- and trans-[(triphos)IrH(&mgr;-H)(2)HIr(triphos)](BPh(4))(2).