Phosphinimide ligands: Difference between revisions
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== Applications == |
== Applications == |
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=== Catalysis === |
=== Catalysis === |
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=History= |
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Phosphinimide ligands have shown recent promise in the area of ethylene polymerization. Since 1955 this field has been dominated by metallocene based catalysts starting with the Ziegler catalyst, followed shortly by the kaminsky catalyst in 1976(10,11). The initial design bases for phosphinimide ligands was suggested due to the fact they have similar steric and electronic properties to metallocene catalysts(8). |
Phosphinimide ligands have shown recent promise in the area of ethylene polymerization. Since 1955 this field has been dominated by metallocene based catalysts starting with the Ziegler catalyst, followed shortly by the kaminsky catalyst in 1976(10,11). The initial design bases for phosphinimide ligands was suggested due to the fact they have similar steric and electronic properties to metallocene catalysts(8). |
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Revision as of 01:29, 18 November 2012
Structure and Bonding
R3PN- (4,1)
(5)
Properties and Reactivity
Synthesis
(6,1)
Applications
Catalysis
History
Phosphinimide ligands have shown recent promise in the area of ethylene polymerization. Since 1955 this field has been dominated by metallocene based catalysts starting with the Ziegler catalyst, followed shortly by the kaminsky catalyst in 1976(10,11). The initial design bases for phosphinimide ligands was suggested due to the fact they have similar steric and electronic properties to metallocene catalysts(8).
Phosphinimide Ligands Compared to Cylclopentadienyl Ligands in Ethylene Polymerization
In most respects the sterics of phosphinimide ligands and electronic properties are considered analogous to cyclopentadienyl ligands(7,8,9). Stericly the metal bound phosphinimide ligand t-Bu3PN produces a cone angles of 87°, quite similar to 83° for cylclopentadienyl suggesting they occupy similar area8. This however does not take into account that the bulkyness of the phosphinimide ligand is partly removed from the metal, by the distance of the nitrogen metal bond. This removal of bulkyness can be considered a beneficial to catalysis as one of the strategies to increase polymerization is to increase the exposure of the metal centre(8). The consequence to a less stericly crowded metal centre appears to be deactivation of the catalysis by lewis acids(7,8).
Diagram of cyclopent. Lign and phophino ligand
The phosphinimide ligands provide an alternative to metallocene catalysts due to their capability to be easily altered during synthesis, allowing for immense variation in the sterics and electronics properties of the system. Therefore, increased specificity of the catalytic properties may be obtained. Also mechanistic and catalytic studies of PE synthesis may be obtained easier through substituent variation and 31P nmr analysis.
Table of catalysis.-9 pg 5
-Activation 11
-olefin polymerization (1,3,7,8
-industrial 9
-general catalysis(2,10)
References
1.http://pubs.acs.org/doi/full/10.1021/om050096b
2.http://search.proquest.com/docview/305323031
3.http://www.nrcresearchpress.com/doi/pdf/10.1139/v06-071
4.http://www.sciencedirect.com/science/article/pii/S001085459800191X
5.http://www.sciencedirect.com/science/article/pii/S0065305505540061
6.http://www.sciencedirect.com/science/article/pii/S0010854597900552#
7.http://pubs.acs.org.ezproxy.library.uvic.ca/doi/pdf/10.1021/om060565p
8.http://pubs.acs.org.ezproxy.library.uvic.ca/doi/pdf/10.1021/om020954t
11.http://search.proquest.com/docview/304631081/abstract?accountid=14846
James Funk
Amanda Charpentier
Greg McGinnis