7 responding to the loss of one and two molecules of carbon monoxide, respectively. The NMR spectrum of 5 shows the highly deshielded C-3 and C-8 protons as a singlet at 6 8.80, while the a and fl protons of the more remote aromatic ring form an eight-line A2B2 system centered at 6 8.31 and 7.90, respectively. The infrared spectrum of 5 (KBr) shows broad carbonyl absorption around 5.8 pm; its ultraviolet spectrum in chloroform is complex and ...