Sequential reaction of (η5-C5Me5)Fe(CO)2I with silver tetrafluoroborate, cyclopentadiene, and finally triethylamine affords the new compound (η5-C5Me5)Fe(CO)2(η1-C5H5) (2) in 75% yield. Reaction of 2 with dimethyl fumarate in dichloromethane gives the [3 + 2] cycloadduct dimethyl 7-syn-[(η5-C5Me5)Fe(CO)2]bicyclo[2.2.1]hept-5-ene-2-endo,3-exo-dicarboxylate in 90% yield. Competitive cycloaddition of the η1-C5H5 moiety in (η5-C5H5)Fe(CO)2(η1-C5H5) (1) and 2 with dimethyl fumarate reveals 2 to be ca. 5 times more reactive. Reaction of 1 and 2 with bis(trifluoromethyl)ketene produces the unexpected and unique 2:1 adducts [(η5-C5R6)Fe(CO)2](1,3-bis[(CF3)2CHCO]cyclopentadienyl} (4, R = H; 5, R = Me). The molecular and crystal structure for 2 is presented. Complex 2 crystallizes in the monoclinic space group P21/n with a = 8.591 (2) Å, b = 36.347 (13) Å, c = 10.119 (3) Å, β= 92.71 (2)°, and Z = 8. The structural parameters are refined to convergence with R1= 0.063 and R2= 0.084 for 2563 reflections having I > 3σ(I). A low-temperature 1H NMR study reveals that the η1-C5H5 ligand in 2 possesses increased fluxionality relative to analogue 1. The increased fluxionality of the η1-C5H5 ring in 2 is attributed to a combination of electronic and steric differences of the η5-C5Me5 ligand relative to the η5-C5H5 group.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry