Organometallics
Communication
increased occupancies of Pd−Cl(4) σ* (0.61) in comparison to
Pd−Cl(5) σ* (0.57) are consistent with a slightly shorter Pd−
Cl bond trans to the phosphaalkene. Stabilization energies
corresponding to these delocalizations are 213.1 and 139.6
kcal/mol, respectively. Unsurprisingly, the π interactions are
much smaller. The π-acceptor components for the tertiary
phosphorus P(2) are the three P−C σ* orbitals; of these P−
C(6) lies in the coordination plane and P−C(11) and P−
C(13) lie out of the plane. The in-plane energy stabilization for
P(2) is 2.2, and the two out of plane interactions sum to 3.5,
giving a total of 5.7 kcal/mol in π-acceptor interactions. In
contrast, P(3) has two in-plane interactions involving P−C σ*
orbitals affording 4.1 kcal/mol stabilization, and a significant
out-of-plane interaction with the PC π* orbital (7.4 kcal/
mol) giving a total 11.5 kcal/mol stabilization. This method of
appraisal concludes that the phosphaalkene component is a
poorer σ donor and a slightly better π acceptor than its tertiary
phosphine partner.
support and access to their chemical inventories, Strem
Chemical Co., Sigma-Aldrich, Chemglass Life Sciences, Fisher
Scientific, Wilmad-Labglass, Dr. Christian Ehm for a critical
reading of an early draft, and William Brennessel (University of
Rochester) for elemental analyses.
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(
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AUTHOR INFORMATION
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval.
Notes
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
M.F.C. thanks the University of Hawai‘i at Manoa for generous
start-up funds and laboratory space, the UHM faculty for
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Organometallics XXXX, XXX, XXX−XXX