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Title:Synthesis, Structure, and Reactivity of High-Nuclearity Carbido Clusters of Rhenium
Author(s):Henly, Timothy James
Doctoral Committee Chair(s):Shapley, John R.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Abstract:The cluster anion (Re$\sb7$C(CO)$\sb{21}\rbrack\sp{3-}$ reacts with late transition metal-based electrophiles to yield the mixed-metal clusters (Re$\sb7$C(CO)$\sb{21}$ML$\sb{\rm n}\rbrack\sp{2-}$ and with H$\sp+$ to yield the hydrido species (HRe$\sb7$C(CO)$\sb{21}\rbrack\sp{2-}$. These complexes have been fully characterized by IR, $\sp1$H NMR, and fast-atom bombardment mass spectroscopies. $\sp1$H and $\sp $C NMR, IR, and cyclic voltammetry studies on selected complexes indicate that the (Re$\sb7$C(CO)$\sb{21}\rbrack\sp{3-}$ cap is a poorer electron donor to the ML$\sb{\rm n}\sp+$ moiety than the cyclopentadienide ligand in the analogous compounds $(\eta\sp5$-C$\sb5$H$\sb5$)ML$\sb{\rm n}$. Variable-temperature $\sp $C NMR studies and X-ray diffraction experiments on several of the mixed-metal clusters demonstrate that each of these compounds adopts a trans-bicapped octahedral configuration of metal atoms, i.e., the ML$\sb{\rm n}$ fragment symmetrically caps the triangular face opposite the unique Re(CO)$\sb3$ group. The compound (HRe$\sb7$C(CO)$\sb{21}\rbrack\sp{2-}$ is a mixture of two isomers, which differ in the position of the hydride ligand on the metal framework.
A set of clusters (Re$\sb7$C(CO)$\sb{21}$HgY) $\sp{2-}$ (Y = halide, pseudohalide, or hydrocarbyl) has also been prepared and characterized. Some of these compounds undergo ligand-exchange reactions of the type: (Re$\sb7$C(CO)$\sb{21}$HgY) $\sp{2-}$ + YHgZ ${}\sbsp{\gets}{\to}$ (Re$\sb7$C(CO)$\sb{21}$HgZ) $\sp{2-}$ + HgY$\sb2$. The position of the equilibrium depends on the electronic properties of Y and Z, with electron-withdrawing groups facilitating ligand redistribution.
The reaction of Re$\sb2$(CO)$\sb $ with sodium in a 1:1.2 molar ratio in triglyme at 200$\sp\circ$C yields the new rhenium carbido clusters (HRe$\sb6$C(CO)$\sb \rbrack\sp{3-}$ and (HRe$\sb5$C(CO)$\sb \rbrack\sp{2-}$. The former complex contains an octahedral arrangement of Re(CO)$\sb3$ units; it reacts with transition metal electrophiles to give the mixed-metal clusters (HRe$\sb6$C(CO)$\sb $ML$\sb{\rm n}\rbrack\sp{2-}$. The latter cluster consists of a square-based pyramid of rhenium atoms with a $\mu\sb5$-carbido atom 0.10 A below the basal plane and a semibridging carbonyl on one basal-apical edge. This compound is the first example of such a M$\sb5$C complex outside of the iron triad elements.
Issue Date:1988
Description:193 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.
Other Identifier(s):(UMI)AAI8815352
Date Available in IDEALS:2014-12-15
Date Deposited:1988

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