2-Pyridylmetallocenes: Part I. Electrophilic halogenation of 2-pyridylferrocene. Molecular structures of 2-pyridylferrocene and its α-brominated and -fluorinated derivatives. Synthesis of 2-pyridylruthenocene and 2-pyridylcymantrene

A new high-yield synthesis of 2-pyridylferrocene (1) without formation of the 1,1′-disubstituted product has been developed. Also the corresponding ruthenocene and cymantrene derivatives [C5H4(2-C5H4N)]MLn (MLn = Ru(C5H5) (2), Mn(CO)3 (3)) were prepared and fully characterized. Ortho-lithiation of 1 followed by electrophilic halogenation yielded [C5H3X(2-C5H4N)]Fe(C5H5) [X = F (4), Cl (5), Br (6), I (7)], with 4 only being the second reported and first fully characterized fluoroferrocene. The molecular structures of 1, 4 and 6 have been determined by X-ray crystallography.