The role of the second coordination sphere of [Ni(PCy 2NBz2)2](BF4) 2 in reversible carbon monoxide binding

Aaron D. Wilson, Kendra Fraze, Brendan Twamley, Susie M. Miller, Daniel L. DuBois, M. Rakowski DuBois

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Abstract

The complex [Ni(PCy2NBz2) 2](BF4)2, 1, reacts rapidly and reversibly with carbon monoxide (1 atm) at 25°C to form [Ni(CO)(PCy 2NBz2)2](BF4) 2, 2, which has been characterized by spectroscopic data and by an X-ray diffraction study. In contrast, analogous Ni(II) carbonyl adducts were not observed in studies of several other related nickel(II) diphosphine complexes. The unusual reactivity of 1 is attributed to a complex interplay of electronic and structural factors, with an important contribution being the ability of two positioned amines in the second coordination sphere to act in concert to stabilize the CO adduct. The proposed interaction is supported by X-ray diffraction data for 2 which shows that all of the chelate rings of the cyclic ligands are in boat conformations, placing two pendant amines close (3.30 and 3.38 Å) to the carbonyl carbon. Similar close C-N interactions are observed in the crystal structure of the more sterically demanding isocyanide adduct, [Ni(CNCy)(PCy2NBz2) 2]2(BF4)2, 4. The data suggest a weak electrostatic interaction between the lone pairs of the nitrogen atoms and the positively charged carbon atom of the carbonyl or isocyanide ligand, and illustrate a novel (non-hydrogen bonding) second coordination sphere effect in controlling reactivity.

Original languageEnglish
Pages (from-to)1061-1068
Number of pages8
JournalJournal of the American Chemical Society
Volume130
Issue number3
DOIs
Publication statusPublished - Jan 23 2008

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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