An NMR study of the rotational barriers in cobalt-stabilized carbocations: X-ray crystal structures of (η4-C4Ph4)Co-(η5-C5H4R), where R is CH3CO, CHO, CH(tBu)OH

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

“…These alcohols are readily dehydroxylated to the di-and triarylmethyl cation analogues [Co(h 4 -C 4 Ph 4 )(h 5 -C 5 H 4 CHFc)] þ and [Co(h 4 -C 4 Ph 4 ) (h 5 -C 5 H 4 CFc 2 )] þ isolated as their [BF 4 ] À salts. The cations are the counterparts of the previously reported [Co(h 4 -C 4 Ph 4 )(h 5 -C 5 H 4 CHR)] þ (R ¼ Bu t and Ph) and [Co(h 4 -C 4 Ph 4 )(h 5 -C 5 H 4 CPh 2 )] þ [11,12].…”

Aldol condensation reactions of [Co(η4-C4Ph4){η5-C5H4C(O)CH3}]

“…However, there is a well-established route to this compound [2] using preformed sodium acetylcyclopentadienide as outlined in Scheme 3 and described in Section 2.…”

“…Published procedures were used to prepare [Co(g 4 -C 4 Ph 4 ){g 5 -C 5 H 4 C(O)CH 3 }] (1a) [2], [Co(g 4 -C 4 Ph 4 )(g 5 -C 5 H 4 CHO)] (2a) [2], [Fe(g-C 5 H 5 ){g 5 …”

“…This followed the procedure given in Ref. [2]. A solution of sodium cyclopentadienide from freshly cracked cyclopentadiene (0.5 mL and sodium metal) and methyl acetate (0.61 mL) in tetrahydrofuran (20 mL) was refluxed for 2 h and then cooled.…”

“…Compound 3k adopts orientation (a), 3i adopts orientation (b), 3d, 3g and 3h adopt orientation (c), and 3e adopts orientation (f). [2] are all tilted with respect to the plane of the cyclobutadiene ligand and in the same sense so that these C 4 Ph 4 constitute a four-bladed propeller. A similar arrangement is observed in 3d and 3h with dihedral angles between cyclobutadiene and phenyl rings of 28.9-36.6°and 29.0-36.2°, respectively, and in 3k where the dihedral angles are all different at 42.1°to C(5), 25.5°to C(11), 30.4°to C(17) and 54.5°to C(23), as they are in 3g at 19.0°to C(5), 57.5°to C(11), 47.1°to C(17) and 34.1°to C(23).…”