| Abstract: | Density functional theory results of the electronic structure of an iridium sulfide, Ir₂S₂(PPh₃)₄ (2), are presented here, along with a discussion of the reaction mechanism of dihydrogen activation on this sulfide. This Ir (II) sulfide shows unusual reactivity binding two equivalents of H₂. The first reaction was believed to be a homolytic cleavage of one H₂, between the two iridium centers, which would produce the dihydride complex Ir₂(PPh₃)₂H₂([mu]-S)₂ (3), while the second-product was believed to arise from heterolytic cleavage by (3) of a second H_(2), between an iridium and a bridging-sulfur atom, which would produce Ir₂([mu]-S)([mu]-SH)([mu]-H)H₂(PPh₃)₄ (4). Previously published crystal structures on (2) and (3) suggest that the there is a strong metal-metal bond in the Ir(II) d7 dimer, (2), and that this bond is surprisingly preserved in the first H₂ cleavage product, (3). We investigated the activation of H₂ by this Ir(II) complex, and the corresponding model complex Ir₂([mu]-S)₂(PH(3))₄, in order to determine the details of this pathway. Our proposed mechanism suggests that the activation of the first equivalent of hydrogen can be either heterolytic or hemolytic, leading to a species with a bridging hydride Ir₂H([mu]-S)₂([mu]-H)(PPh₃)₄ (3-brid) in which the metal-metal bond is preserved, while the second activation appears to be a heterolytic activation, which produces the final product (4). The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152530 |
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