Diphosphine substitution in pentakis(arylisocyanide)cobalt(I) complexes; P-31 NMR, cyclic voltammetric and ESI mass spectrometry studies
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Author list: Mbaiwa FF, Becker CAL
Publisher: Elsevier
Place: LAUSANNE
Publication year: 2006
Journal: Inorganica Chimica Acta (0020-1693)
Journal acronym: INORG CHIM ACTA
Volume number: 359
Issue number: 4
Start page: 1041
End page: 1049
Number of pages: 9
ISSN: 0020-1693
eISSN: 1873-3255
Languages: English-Great Britain (EN-GB)
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Abstract
Five new complexes of the type [Co(CNC(6)H(3)iPr(2)-2,6)(4)PPh2-R'-PPh2]X, X = BF4, ClO4; R'=-(CH2)(2)-(1), -(CH-(2))(3)- (2), -CH=CH-trans (3), -C C- (4) and -C6H4-P (5); and two new bimetallic complexes, [{Co(CNC(6)H(3)iPr(2)-2,6)(4)}(2)(mu-PPh2(CH2)(3)PPh2)](ClO4)(2) (6) and [{Co(CNC(6)H(3)iPr(2)-2,6)(4))}(2)(mu-PPh2C6H4PPh2-p))](ClO4)(2) (7), have been synthesized and characterized by various spectroscopic methods. Known monometallic and bimetallic complexes bearing the ligand CNC6H3Et2-2,6 instead of CNC(6)H(3)iPr(2)-2,6 have been included in the P-31 NMR, cyclic voltammetric and mass spectrometry studies. Comparison of the CNC6H3Et2-2,6 with the CNC6H3Et2-2,6 complexes shows that the increased steric bulkiness of the former makes it more suitable for synthesis of the monometallic complexes, whilst the CNC6H3Et2-2,6 is more apt to give bimetallic complexes. Thus, the two arylisocyanides are complementary with respect to synthesis of the monometallic and bimetallic complexes. The P-31 NMR indicates that the diphosphines in monometallic complexes behave as non-fluxional, monodentate ligands at ambient temperature, with (31)p-(31)p Coupling shown for the PPh2CH2PPh2, PP2(CH2)(2)PPh2 and PPh2C CPPh2 ligands. Cyclic voltammetry fails to show electronic communication in the bimetallic complexes, and mass spectrometry indicates significantly greater stability for fragments containing potentially chelating diphosphines as compared to diphosphines that cannot chelate. (c) 2005 Elsevier B.V. All rights reserved.
Keywords
arylisocyanides, cyclic voltammetry, diphosphines, ligand substitution P-31 NMR
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