Peripheral methyl activation in η4-1,2,3,4-tetramethylcyclobutadienylcobalt complexes: template synthesis and subsequent reactivity of triphosphamacrocycles

Edwards, Peter Gerald ORCID: https://orcid.org/0000-0001-6999-753X, Kariuki, Benson ORCID: https://orcid.org/0000-0002-8658-3897, Newman, Paul David ORCID: https://orcid.org/0000-0002-1808-1211 and Zhang, Wenjiang 2014. Peripheral methyl activation in η4-1,2,3,4-tetramethylcyclobutadienylcobalt complexes: template synthesis and subsequent reactivity of triphosphamacrocycles. Organometallics 33 (19) , pp. 5440-5447. 10.1021/om500734b

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Abstract

The cationic complex (η4-1,2,3,4-tetramethylcyclobutadienyl)cobalt(trisacetonitrile), [(η4-C4Me4)Co(NCCH3)3]+ (1), allows the stepwise introduction of suitable phosphine precursors to the [(η4-C4Me4)Co]+ fragment by replacement of the labile acetonitrile ligands. These reactions give rise to the piano-stool complexes [(η4-C4Me4)Co(dppe)(NCCH3)]+ (2), [(η4-C4Me4)Co(dppe)(PH2Ph)]+ (3), [(η4-C4Me4)Co(dfppb)(NCCH3)]+ (4), and [(η4-C4Me4)Co(dfppb)(PH2Ph)]+ (5), where dfppb = 1,2-bis{di(2-fluorophenyl)phosphino}benzene and dppe = 1,2-bis(diphenylphosphino)ethane. Complex 5 is a template for the synthesis of the P3 macrocycle complex [(η4-C4Me4)Co{1,4-bis(2-fluorophenyl)-7-phenyl[b,e,h]tribenzo-1,4,7-triphosphacyclononane}]+ (6), through base-promoted intramolecular macrocyclization. The hydrogens of two of the ring methyls of the tetramethylcyclobutadienyl ligand in the macrocycle complex 6 are sufficiently acidic to undergo deprotonation by KOtBu, promoting nucleophilic attack at the fluorine-bearing ortho-carbons of the 2-fluoroaryl groups on two of the phosphorus donors in 6. The resultant hemi-incarcerand complex [{η4,κP,κP,κP-Me2C4-[1,4-bis(2-CH2C6H4)-7-C6H5-[b,e,h]tribenzo-1,4,7-triphosphacyclononane]-1,2}Co]+ (cis-7) contains a hybrid phosphorus/carbon donor ligand where the P3 macrocycle is connected to the cyclobutadienyl function through two cis-2-methylphenyl links. The new complexes have been characterized fully by spectroscopic and analytical techniques including single-crystal X-ray structure determinations of 2, 3, 4, 5, 6, and cis-7.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Additional Information:	Published online August 29th 2014.
Publisher:	American Chemical Society
ISSN:	0276-7333
Last Modified:	27 Oct 2022 09:08
URI:	https://orca.cardiff.ac.uk/id/eprint/64509

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