US EPA

8706492 

Journal Article 

Electron paramagnetic resonance spectrum of Cu(CO)3: An inorganic isolobal analogue of methyl 

Howard, JA; Mile, B; Morton, JR; Preston, KF; Sutcliffe, R 

1986 

1 

Journal of Physical Chemistry
ISSN: 0022-3654 

90 

6 

1033-1036 

English 

10.1021/j100278a014 

Copper tricarbonyl, Cu(CO)3, has been prepared on a rotating cryostat by reacting 63Cu atoms with CO on either a cyclohexane or adamantane surface at 77 K. Its EPR spectrum (4-77 K) yielded the following parameters: gxx = gyy = 2.0028, gzz = 2.0010; for 63Cu, axx = ayy ≃ 0 MHz, azz = 225 MHz; for 13C, axx = ayy = 29 MHz, azz = 8 MHz. The spectrum of Cu(CO)3 in adamantane was isotropic at 223 K, yielding the following parameters: giso = 2.0014, a63 = 93.9 MHz, a13(3) = 22.0 MHz. Cu(CO)3 is a planar molecule belonging to the A2″ representation in D3h symmetry. Most of the unpaired electron is in the Cu 4pz orbital perpendicular to the molecular plane. There is a marked temperature dependence of the isotropic copper hyperfine interaction, which increases from 75 MHz at 4 K to 98 MHz at 250 K. This is attributed to an out-of-plane vibration of the radical which modulates the isotropic copper hyperfine interaction. An analysis of this effect yields a v2 vibration frequency of ∼300 cm-1. Cu(CO)3 is stable to decomposition or dimerization in adamantane up to at least 263 K and may provide a suitable vehicle for incorporating copper into inert supports for catalytic purposes.