Model Chemistry on Metal Surfaces: Synthesis, Structure and Reactivity Studies of Tungsten-Osmium Mixed-Metal Clusters

Chi, Yun

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Description

Title

Model Chemistry on Metal Surfaces: Synthesis, Structure and Reactivity Studies of Tungsten-Osmium Mixed-Metal Clusters

Author(s)

Chi, Yun

Issue Date

1986

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Chemistry, Inorganic

Abstract

• Reaction of H(,2)Os(,3)(CO)(,10) with CpW(CO)(,2)(CTol) provides four mixed-metal compounds, i.e. CpWOs(,3)(CO)(,11) (mu)(,3)-(eta)('2)-C(O)CH(,2)Tol (1), CpWOs(,3)(CO)(,10)((mu)(,3)-CTol)(,2)H (2), Cp(,2)W(,2)Os(CO)-(,7)((mu)(,3)-(eta)('2)-C(,2)Tol(,2)) (3),
• and CpW(CO)(,3) ((mu)-H)(,2)Os(,3)(CO)(,9)((mu)(,3)-CTol) (4). Reaction of 4 with Cp- W(CO)(,2)-(CTol) give complex 2. Pyrolysis of 1 and 3 gives CpWOs(,3)- (CO)(,9)((mu)-O)((mu)(,3)-CCH(,2)Tol) (5) and Cp(,2)W(,2)Os(CO)(,5)((mu)-CTol)((mu)(,3)-CTol), respectively. Compound 5 undergoes monocarbonylation to give
• CpW(CO)(,2)(CTol) provides a TBP pentanuclear cluster CpW(,2)Os(,3)- (CO)(,9)((mu)(,3)-O)((mu)(,3)-(eta)('2)-CCHTol); VT-('1)H NMR studies show that the vinylidene ligand undergoes a one-third cycle of circumambulation. (Abstract shortened with permission of author.)
• CpWOs(,3)(CO)(,10)((mu)-O)((mu)(,3)-CCH(,2)Tol), which is an intermediate for the acyl C-O bond scission process (1 (--->) 5). Pyrolysis of 5 gives CpWOs(,3)(CO)(,9)((mu)-H)((mu)-O)((mu)-CCHTol).
• Treatment of 5 with Ph-C(TBOND)C-Ph provides a butterfly cluster Cp- WOs(,3)(CO)(,8)((mu)-O)((mu)(,3)-CCH(,2)-Tol)((mu)(,3)-(eta)('2)-C(,2)Ph(,2)). This complex under- goes reaction under an H(,2) atmosphere, or decarbonylation to give
• CpWOs(,3)(CO)(,7)((mu)-H)(,2)((mu)-O)((mu)(,4)-(eta)('2)-CCHTol)(CH=CHPh) or CpWOs(,3)- (CO)(,7)((mu)-O)((mu)-(eta)('2)-CHCHTol)(C(,2)Ph(,2)), respectively.
• Reaction of 5 with various HX reagents, X = H, Cl, Br and S-C(,6)H(,5), provides three alkylidene complexes with the formulation of CpW- Os(,3)(CO)(,9)((mu)-X)((mu)-O)((mu)-CHCH(,2)Tol) (isomers-a, b and c). The inter- conversion of a and b, and of b and c involves H-migration and alkyl- idene isomerization, respectively. For the alkylidene complexes, X (NOT=) H, only b and c isomers are isolated, in which c is the thermodynam- ically more stable form. Treatment of CpWOs(,3)(CO)(,9)((mu)-Cl)((mu)-O)((mu)-CHCH(,2)Tol) (isomers b and c) with gaseous BCl(,3) generates CpWOs(,3)- (CO)(,9)((mu)-Cl)((mu)-OBCl(,3))((mu)-CHCH(,2)Tol) in which BCl(,3) has been found to coordinate the bridging oxo-ligand, thereby activating the reverse alkylidene isomerization from isomers c to b.
• Reaction of 5 with cyclooctene under N(,2) or H(,2) affords CpWOs(,3)- (CO)(,8)(C(,8)H(,14))((mu)-H)((mu)-O)((mu)-CCHTol) (6), or CpWOs(,3)(CO)(,8)(C(,8)H(,14))((mu)-H)((mu)-O)((mu)-CHCH(,2)Tol), respectively. The reaction presumably pro- ceeds by cyclooctene substitution to give an alkylidyne intermediate
• CpWOs(,3)(CO)(,8)(C(,8)H(,14))((mu)-O)((mu)(,3)-CCH(,2)Tol). Compound 6 undergoes olefin exchange with ethylene to provide CpWOs(,3)(CO)(,8)(C(,2)H(,4))((mu)-H)- ((mu)-O)((mu)-CCHTol), in that the C(,2)H(,4) group is coordinated to an Os atom associated with the bridging hydride; the reversible C(,2)H(,4) inser- tion into Os-H-Os bond is established by dynamic NMR techniques.
• Exchange with either dimethyl meleate (fumarate) gives another extreme of such olefin insertion reaction, an alkyl complex CpWOs(,3)- (CO)(,8)((mu)-O)((mu)-CCHTol) CH(CO(,2)CH(,3))CH(,2)(CO(,2)CH(,3)) being isolated.
• The reversible insertion of an alkyne into the Os-H-Os bond is explored by exchange of C(,8)H(,14) with Ph-C(TBOND)C-Ph, giving CpWOs(,3)- (CO)(,8)((mu)(,3)-O)((mu)(,3)-(eta)('2)-CCHTol)((mu)-(eta)-CPh=CHPh). Reaction of 6 with

Graduation Semester

1986

Type of Resource

text

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