TY - JOUR
T1 - The role of the second coordination sphere of [Ni(PCy 2NBz2)2](BF4) 2 in reversible carbon monoxide binding
AU - Wilson, Aaron D.
AU - Fraze, Kendra
AU - Twamley, Brendan
AU - Miller, Susie M.
AU - DuBois, Daniel L.
AU - DuBois, M. Rakowski
PY - 2008/1/23
Y1 - 2008/1/23
N2 - 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.
AB - 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.
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U2 - 10.1021/ja077328d
DO - 10.1021/ja077328d
M3 - Article
C2 - 18163630
AN - SCOPUS:38349187638
VL - 130
SP - 1061
EP - 1068
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 3
ER -