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THE SYNTHESIS, REACTIVITY, AND STRUCTURAL ANALYSIS OF ANIONIC RHODIUM(-I) AND IRIDIUM(-I) COMPLEXES
Abstract
Anionic Rh(-I) and Ir(-I) complexes containing olefin or phosphine ligands were synthesized via the alkali metal reduction of CpM(COD) (M = Rh,Ir) in the presence of excess ligand. Other methods of synthesis involving the chemical reduction of rhodium and iridium containing species were also investigated. The reactivities of these novel anionic complexes were determined. ${\rm M(COD)\sb{2}\sp{-}}$ (M = Rh,Ir) undergoes substitution reactions with phosphines, CO, and other bidentate olefins to form the corresponding ${\rm ML\sb{4}\sp{-}}$ or ${\rm M(L\sb{2})\sb{2}\sp{-}}$ complexes. ${\rm Rh(COD)\sb{2}\sp{-}}$ reacts with PhC$\equiv$CPh to form hexaphenylbenzene, and with bis(trimethylsilyl)acetylene to form ((COD)Rh(C$\equiv$CSiMe$\sb{3})\sb{2}\rbrack\sp{-}.$ A kinetic rate study was conducted for the ${\rm Rh(COD)\sb{2}\sp{-}}$ substitution with DPPE showing a concentration dependence on both ${\rm Rh(COD)\sb{2}\sp{-}}$ and DPPE. The chemical reactivities of anionic Rh(-I) phosphine complexes were also investigated, showing them to be strong ${\rm H\sp{+}}$ accepters, and highly susceptible to oxidative addition reactions. All reactions and products were analyzed by ${\rm \sp{1}H},$ ${\rm \sp{13}C},$ and/or ${\rm \sp{31}p}$ NMR spectroscopy. X-ray structural analyses were conducted for (Na(18-crown-6)${\rm (DMF)\sb{2}}$) ${\rm \lbrack Rh(COD)\sb{2}\rbrack}$ (I), ((K(18-crown-6))$\sb{2}$Cp) -${\rm \lbrack Ir(COD)\sb{2}\rbrack}\cdot$2DMF (II), and (Na(18-crown-6)${\rm (THF)\sb{2}}$) ((COD)Rh(C$\equiv$CSiMe$\sb{3})\sb{2}$) (V). All three compounds crystallize in a triclinic unit cell with two cation/anion pairs per unit cell. The space group for all three is ${\rm P}\sb{\bar 1}.$ Unlike the isoelectronic ${\rm Ni(COD)\sb{2}}$ molecule which has a tetrahedral arrangement of olefin ligands around the metal, complexes (I) and (II) have an arrangement midway between tetrahedral and square planar. Such an arrangement produces quite short H$\cdots$H contacts between olefinic hydrogens on different COD ligands. Complex (V) has a square planar $16{\rm e}\sp{-}$ ${\rm d}\sp{8}$ geometry.
Subject Area
Chemistry
Recommended Citation
MANN, CHARLES M, "THE SYNTHESIS, REACTIVITY, AND STRUCTURAL ANALYSIS OF ANIONIC RHODIUM(-I) AND IRIDIUM(-I) COMPLEXES" (1987). ETD collection for University of Nebraska-Lincoln. AAI8717261.
https://digitalcommons.unl.edu/dissertations/AAI8717261