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

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). pp. 2415-2426. ISSN 1477-9234

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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)2C12F8, 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)2ZrMe2 activated with the various boranes or trityl borates gives an anion-dependent activity sequence, in the order [NC-PBB]- < [MeB(C6F5)3]- < [MePBB]- ˜ [PBB-NCB(C6F5)3]- ˜ [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.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Chemistry (former - to 2024)
UEA Research Groups:	Faculty of Science > Research Groups > Synthetic Chemistry (former - to 2017) Faculty of Science > Research Groups > Chemistry of Materials and Catalysis Faculty of Science > Research Groups > Chemistry of Light and Energy Faculty of Science > Research Groups > Energy Materials Laboratory
Depositing User:	Rachel Smith
Date Deposited:	02 Nov 2010 17:48
Last Modified:	06 Feb 2025 03:00
URI:	https://ueaeprints.uea.ac.uk/id/eprint/10525
DOI:	10.1039/b515548g

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