Cyclopentadienyldicarbonyliron halides as electrophiles. Reactions of (η5-C5H5)Fe(CO)2X with RLi in the presence of PPh3 to produce (η4-exo-RC5H5)Fe(CO)2(PPh3) and preparation of [(η5-C5H5)Fe(CO)C(O)Me](μ,η1,η 1 -dppf) [(η4-exo-MeC5H5)Fe(CO)2]