CRYSTAL-STRUCTURE, AND VARIABLE-TEMPERATURE PROTON AND C-13 NMR-SPECTRA OF THE 9-MEMBERED RING COMPLEX (E,Z-PPH(2)CH(2)C((T)BU)=N-N=C((T)BU)CH(2)PPH(2))]

Treatment of [Cr(CO)(4)(nbd)] (nbd = norbornadiene) with Z,Z-PPh(2)CH( 2)C((t)Bu)=N-N=C((t)Bu)CH(2)PPh(2) gave the title compound 2b, the str ucture of which was determined by a single crystal X-ray diffraction s tudy. The proton NMR spectrum of 26 at 308 K and 400 MHz showed that f or each of the methylene groups the protons are equivalent, but the sp ectrum is temperature dependent and at 188 K the slow exchange limitin g spectrum is obtained, with all methylene hydrogens chemically non-eq uivalent; corresponding changes were observed in the C-13-(H-1) NMR sp ectrum. The behaviour is due to the fluxionality of the 9-membered rin g.