Stilbene analogues incorporating the Co(η4-C4Ph4)(η5-C5H4-) end group

The preparation, spectroscopy, structure and electrochemistry of some [Co(η4-C4Ph4)(η5-C5H4R)] complexes

“…Work-up of this solution as per [14][BF 4 ] afforded a sample for electrochemical studies. l max /nm (3/dm 3 mol À1 cm À1 ) (CH 2 Cl 2 ): 395 (24 000); 585 (sh, 900); 855 (12 000).…”

“…[37], and also with the oxidation potentials of the metallocenyl groups (see below). When the alcohol 9 is converted to the cation [14] þ , the number of resonances due to the Fe(h 5 -C 5 H 4 e) moieties declines from five to three and there is one due to the Fe(h 5 -C 5 H 5 ). Thus the a/a 0 and b/b 0 pairs of the two ferrocenyl groups in the cation are no longer in different NMR environments.…”

“…Thus the a/a 0 and b/b 0 pairs of the two ferrocenyl groups in the cation are no longer in different NMR environments. This is a consequence of planar coordination about C a in [14] þ and rapid rotation about its C a -C ipso bonds. The chemical shift of the C a resonance at d 196.9 is much lower than that found in [13] þ but its Dd of 124.3 ppm is much larger and comparable to that observed for the Ph 3 COH/Ph 3 C þ system (128 ppm) [38].…”

“…Taken as a whole this suggests that, as in [13] þ , the positive charge is delocalized away more effectively by the Fe centres than the Co, but because [14] þ contains two ferrocenyl groups, the effect on each is less pronounced than on the single ferrocenyl group of [13] þ . When the structure of [14] þ is represented by a resonance hybrid of four mesomers, each of the equivalents of II in Fig.11 makes a smaller contribution than does II itself to [13] þ , and so the C a -ferrocenyl bonds have a lower order in [14] þ than in [13] þ .…”

“…These provide access to organometallic functionalised alkenes, a research area currently attracting much attention [13]. This work will be covered in a subsequent paper [14].…”