The 'Indenyl Effect' in iridium(I) olefin complexes

Szajek, Lawrence Philip

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Description

Title

The 'Indenyl Effect' in iridium(I) olefin complexes

Author(s)

Szajek, Lawrence Philip

Issue Date

1991

Doctoral Committee Chair(s)

Shapley, John R.

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

Language

eng

Abstract

• "The complexes CpIr($\eta\sp2$-C$\sb8$H$\sb{14}$)CO and ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb8$H$\sb{14}$)CO were prepared in high yield from (($\eta\sp2$-C$\sb8$H$\sb{14}$)$\sb2$Ir(CO)Cl) $\sb2$ and thallium cyclopentadienide or potassium indenide, respectively. The stereoisomers of CpIr($\eta\sp2$-C$\sb8$H$\sb{14}$)CO, ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb8$H$\sb{14}$)CO, and ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb8$H$\sb{14}$)$\sb2$, were characterized by two-dimensional NMR techniques. Due to the ""Indenyl Effect,"" ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb8$H$\sb{14}$)CO was more reactive than CpIr($\eta\sp2$-C$\sb8$H$\sb{14}$)CO toward Lewis bases. The labile cyclooctene ring of ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb8$H$\sb{14}$)CO was readily replaced under mild conditions by other two electron donors such as triphenylphosphine, carbon monoxide, ethylene, or phenylacetylene; CpIr($\eta\sp2$-C$\sb8$H$\sb{14}$)CO was not reactive under identical or more severe conditions. The complex ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb8$H$\sb{14}$)CO readily oxidatively added C-Br and Si-H bonds, again under mild conditions, and was found to be an active and robust catalyst for the hydrogenation and hydrosilylation of alkenes and alkynes. The reaction of CO with ($\eta\sp5$-C$\sb9$H$\sb7$)Ir(CO)$\sb2$ resulted in the formation of the $\eta\sp1$-slipped indenyl ring of ($\eta\sp1$-C$\sb9$H$\sb7$)Ir(CO)$\sb3$."
• "For CpIr($\eta\sp2$-C$\sb2$H$\sb4$)L and ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb2$H$\sb4$)L, where L = ethylene or CO, the barrier to ethylene rotation about the iridium-ethylene bond axis was determined by lineshape fitting of variable-temperature $\sp1$H NMR spectra. The free energies of activation were found to be 5-6 kcal/mole less for the indenyl complexes than for the corresponding cyclopentadienyl complexes (14 and 20 kcal/mole, respectively). This lowering of the barrier to ethylene rotation is an attribute of the ""Indenyl Effect."""
• Some related projects included the following. Attempted preparation of CpIr($\eta\sp2$-C$\sb8$H$\sb{14}$)$\sb2$ resulted in an unexpected but useful synthesis of the cyclopentadiene complex CpIr($\eta\sp4$-C$\sb5$H$\sb6$). The proton and carbon resonances of the series of complexes CpM($\eta\sp4$-C$\sb5$H$\sb6$), where M = Co, Rh, or Ir, were compared. Protonation studies of CpIr($\eta\sp2$-C$\sb8$H$\sb{12}$) and ($\eta\sp5$-C$\sb9$H$\sb7$)Ir($\eta\sp2$-C$\sb8$H$\sb{12}$) allowed us to examine $\eta\sp5$ to $\eta\sp6$ haptotropic indenyl ring shifts. Synthetic routes to a metal cyclopentaphenanthrene complex Cp*Ru($\eta\sp5$-C$\sb{15}$H$\sb9$), were explored.

Type of Resource

text

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Copyright 1991 Szajek, Lawrence Philip

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