The thermally initiated reaction of hexafluorobut-2-yne and (q-C5H5)C~(C0)2 gives the 1-4-q-
hexakis(trifiuoromethy1)benzene complex (7-C5H5)Co [(CF3C2CF3)3] in addition to the known
cyclopentadienone complex (q-C5H5)Co [(CF3C2CF3)2CO]. The related reaction of but-2-yne with
(q-CjH j)Co(CO)2 gives several compounds in addition to the cyclopentadienone complex (q-C jHj)C~-
[(MeC2Me)2CO] which has been isolated previously from this reaction. Thus, the duroquinone
complex (q-C5H5)Co [(MeC2Me)2(C0)2], the maleoyl complex (q-C5H5)Co(MeC2Me)(C0)3, and
free duroquinone have been obtained. The yields of the various products are influenced by the
reaction conditions. The metallocyclopentadiene complex (q-C jH j)2Rh2(CF3C2CF3)2, which is formed
in the reaction between (q-C,H,)Rh(CO), and hexafluorobut-2-yne, exhibits fluxional behaviour
in solution at c. 130". Two complexes are formed in the reaction at 100-120' between (q-C5Hj)Rh-
(CO)2 and but-2-yne. These are the cyclopentadienone complex (q-C5H5)Rh [(MeC2Me)2CO] and
the duroquinone complex (7-CjH5)Rh [(MeC2Me)2(C0)2].
Comparison of the various reactions indicates that: (i) a cyclopentadienone complex (q-CgH5)M-
[(MeC2Me)2CO] is generally formed as major product and a duroquinone complex (q-C5Hj)M-
[(MeC2Me)2(C0)2] is generally formed as a minor product in reactions between (q-C5H5)M(C0)2,
M = Co and Rh, and but-2-yne; and (ii) a tetrahaptobenzene complex (q-C5H5)M [(CF3C2CF3)3] is
formed as major product when M = Rh and as a minor product when M = Co in reactions between
(q-C5H5)M(CO)2 and hexafluorobut-2-yne.
Recent Studies on the Nitrogen Fixation by Transition Metal Complexes
