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

Peripheral methyl activation in η4-1,2,3,4-tetramethylcyclobutadienylcobalt complexes: template synthesis and subsequent reactivity of triphosphamacrocycles
Peripheral methyl activation in η4-1,2,3,4-tetramethylcyclobutadienylcobalt complexes: template synthesis and subsequent reactivity of triphosphamacrocycles
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.
0276-7333
5440-5447
Edwards, Peter G.
fcd5e923-9269-48a2-8fd3-0b8120f9a82b
Kariuki, Benson M.
634ee7db-bcd1-4544-b667-2ad8c48ecedd
Newman, Paul D.
42e7ca00-b874-4cfb-a74a-6308015c4a8e
Zhang, Wenjian
1f80ac5e-d4c2-4720-b19e-be700cd411e7
Edwards, Peter G.
fcd5e923-9269-48a2-8fd3-0b8120f9a82b
Kariuki, Benson M.
634ee7db-bcd1-4544-b667-2ad8c48ecedd
Newman, Paul D.
42e7ca00-b874-4cfb-a74a-6308015c4a8e
Zhang, Wenjian
1f80ac5e-d4c2-4720-b19e-be700cd411e7

Edwards, Peter G., Kariuki, Benson M., Newman, Paul D. and Zhang, Wenjian (2014) Peripheral methyl activation in η4-1,2,3,4-tetramethylcyclobutadienylcobalt complexes: template synthesis and subsequent reactivity of triphosphamacrocycles. Organometallics, 33 (19), 5440-5447. (doi:10.1021/om500734b).

Record type: Article

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.

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Accepted/In Press date: 29 August 2014
e-pub ahead of print date: 29 August 2014

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Local EPrints ID: 430163
URI: http://eprints.soton.ac.uk/id/eprint/430163
ISSN: 0276-7333
PURE UUID: 2a8d363b-1ca8-4e02-8007-ee7c5114c8be

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Date deposited: 15 Apr 2019 16:30
Last modified: 09 Oct 2020 16:40

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Contributors

Author: Peter G. Edwards
Author: Benson M. Kariuki
Author: Paul D. Newman
Author: Wenjian Zhang

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