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The synthesis of new weakly coordinating diborate anions: anion stability as a function of linker structure and steric bulk

The synthesis of new weakly coordinating diborate anions: anion stability as a function of linker structure and steric bulk
The synthesis of new weakly coordinating diborate anions: anion stability as a function of linker structure and steric bulk
The successive addition of KCN and Ph3CCl to B(C6F4-C6F5-2)(3) (PBB) affords triphenylmethyl salts of the [NC-PBB](-) anion. By contrast, the analogous reaction with sodium dicyanamide followed by treatment with Ph3CCl leads to the zwitterionic aminoborane H2NB(C12F9)(2)C12F8, via nucleophilic attack on an o-F atom, together with CPh3[F-PBB]. Whereas treatment of [NC-PBB](-) with either PBB or B(C6F5)(3) fails to give isolable cyano-bridged diborates, the reaction of Me3SiNC-B(C6F5)(3) with PBB in the presence of Ph3CCl affords [Ph3C][PBB-NC-B(C6F5)(3)]. Due to steric hindrance this anion is prone to borane dissociation. The longer linking group N(CN)(2)(-) gives the very voluminous anions [N{CNB(C6F5)(3)}(2)](-) and [N(CN-PBB)(2)](-). A comparison of propylene polymerisations with rac-Me2Si(Ind)(2)ZrMe2 activated with the various boranes or trityl borates gives an anion-dependent activity sequence, in the order [NC-PBB](-) < [MeB(C6F5)(3)](-) < [MePBB](-) approximate to [PBB-NCB(C6F5)(3)](-) approximate to [N{CNB(C6F5)(3)}(2)](-) < [F-PBB](-) << [B(C6F5)(4)](-) < [N(CN-PBB)(2)](-). The anion [N(CN-PBB)(2)](-) gives a catalyst productivity about 2500 times higher than that of [NC-PBB](-) and exceeds that of [B(C6F5)(4)](-) based catalysts. The van der Waals volumes and surface areas of the anions have been calculated and provide a rationale for the observed reactivity trends in polymerisation reactions.
dot-f-c, metallocene polymerization catalysts, stereospecific olefin polymerization, propene polymerization, alkene polymerization, noncoordinating anions, ziegler catalysts, amine adducts, complexes, zirconium
1477-9226
2415-2426
Hannant, Mark H.
9260c1e6-45b8-46a6-b32a-389491fb0b79
Wright, Joseph A.
3e730775-dda4-4d1e-83ad-8b1e96fb2cbe
Lancaster, Simon J.
06d860ba-99d7-4be1-a78d-39505c0fc14b
Hughes, David L.
d3b8245e-976a-47e6-8fe6-6ebcf38e2255
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Bochmann, Manfred
ec2bb201-23cc-4f91-aa80-258e6c8cc9fb
Hannant, Mark H.
9260c1e6-45b8-46a6-b32a-389491fb0b79
Wright, Joseph A.
3e730775-dda4-4d1e-83ad-8b1e96fb2cbe
Lancaster, Simon J.
06d860ba-99d7-4be1-a78d-39505c0fc14b
Hughes, David L.
d3b8245e-976a-47e6-8fe6-6ebcf38e2255
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Bochmann, Manfred
ec2bb201-23cc-4f91-aa80-258e6c8cc9fb

Hannant, Mark H., Wright, Joseph A., Lancaster, Simon J., Hughes, David L., Horton, Peter N. and Bochmann, Manfred (2006) The synthesis of new weakly coordinating diborate anions: anion stability as a function of linker structure and steric bulk. Dalton Transactions, (20), 2415-2426. (doi:10.1039/b515548g).

Record type: Article

Abstract

The successive addition of KCN and Ph3CCl to B(C6F4-C6F5-2)(3) (PBB) affords triphenylmethyl salts of the [NC-PBB](-) anion. By contrast, the analogous reaction with sodium dicyanamide followed by treatment with Ph3CCl leads to the zwitterionic aminoborane H2NB(C12F9)(2)C12F8, via nucleophilic attack on an o-F atom, together with CPh3[F-PBB]. Whereas treatment of [NC-PBB](-) with either PBB or B(C6F5)(3) fails to give isolable cyano-bridged diborates, the reaction of Me3SiNC-B(C6F5)(3) with PBB in the presence of Ph3CCl affords [Ph3C][PBB-NC-B(C6F5)(3)]. Due to steric hindrance this anion is prone to borane dissociation. The longer linking group N(CN)(2)(-) gives the very voluminous anions [N{CNB(C6F5)(3)}(2)](-) and [N(CN-PBB)(2)](-). A comparison of propylene polymerisations with rac-Me2Si(Ind)(2)ZrMe2 activated with the various boranes or trityl borates gives an anion-dependent activity sequence, in the order [NC-PBB](-) < [MeB(C6F5)(3)](-) < [MePBB](-) approximate to [PBB-NCB(C6F5)(3)](-) approximate to [N{CNB(C6F5)(3)}(2)](-) < [F-PBB](-) << [B(C6F5)(4)](-) < [N(CN-PBB)(2)](-). The anion [N(CN-PBB)(2)](-) gives a catalyst productivity about 2500 times higher than that of [NC-PBB](-) and exceeds that of [B(C6F5)(4)](-) based catalysts. The van der Waals volumes and surface areas of the anions have been calculated and provide a rationale for the observed reactivity trends in polymerisation reactions.

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Published date: 2006
Keywords: dot-f-c, metallocene polymerization catalysts, stereospecific olefin polymerization, propene polymerization, alkene polymerization, noncoordinating anions, ziegler catalysts, amine adducts, complexes, zirconium

Identifiers

Local EPrints ID: 44458
URI: http://eprints.soton.ac.uk/id/eprint/44458
ISSN: 1477-9226
PURE UUID: 7130a3d9-5786-4b3e-906e-0a27ac5e8598
ORCID for Peter N. Horton: ORCID iD orcid.org/0000-0001-8886-2016

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Date deposited: 01 Mar 2007
Last modified: 29 Oct 2019 01:57

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Contributors

Author: Mark H. Hannant
Author: Joseph A. Wright
Author: Simon J. Lancaster
Author: David L. Hughes
Author: Peter N. Horton ORCID iD
Author: Manfred Bochmann

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