Mp. Thornberry et al., Synthesis and structure of piano stool complexes derived from the tetrakis(pentafluorophenyl)cyclopentadienyl ligand, ORGANOMETAL, 20(5), 2001, pp. 920-926
The reaction of NaCp (Cp = C5H5) With excess C6F6 and excess NaH in refluxi
ng diglyme afforded a 57% yield of 1,2,3,4-tetrakis(pentafluorophenyl)cyclo
pentadiene (1). Treatment of 1 with NaH in THF afforded sodium tetrakis(pen
tafluorophenyl)cyclopentadienide (2) in 89% yield. Reactions of 2 with M(CO
)(5)Br (M = Mn, Re) yielded [(C6F5)(4)C5H]M(CO)(3) complexes (3, M = Mn, 33
%, and 4, M = Re, 28%). Reactions of 2 with various iron(II) salts and with
CoBr2 however failed to afford the corresponding octaarylated metallocenes
. Infrared spectroscopic analysis of 3 and 4 revealed an increase of 16(1)
cm(-1) relative to CpM(CO)(3) in the A-symmetric C-O stretching frequency,
suggesting that the C6F5 groups have a highly electron-withdrawing effect o
n the coordinated M(CO)(3) moieties. Crystal structures of 1, 1.(1)/2C6D6,
2, and 3 display a propeller-like arrangement of the C5F5 groups. Complexes
2 and 3 show elongation of the Cs(centroid)-M bond distances relative to C
pMn(CO)(3) and CpRe(CO)(3), which is attributed to steric effects.