Oligoalkyne-Bridged (η4-Cyclobutadiene)(η5-cyclopentadienyl)cobalt Fragments − Syntheses and Properties

Abstract

The syntheses of (η 5 -cyclopentadienyl)(η 4 -tetraphenylcyclobutadiene)cobalt units bridged by buta-1,3-diyne, octa-1,3,5,7-tetrayne, and dodeca-1, 3,5,7,9,11-hexayne units (15, 18, 21) are reported. All three species could be obtained by Hay coupling of the corresponding mono-, di-, and triyne units 14, 17, and 20. In the case of 14−17 and 21, the molecular

Synthesis and 1H NMR spectroscopic properties of substituted (η4-tetraarylcyclobutadiene)(η5-cyclopentadienyl)cobalt metallocenes

“…Methyl ester 2a was reduced with LiAlH 4 to the alcohol 15 [7b, 16] which was further reduced with LiAlH 4 in the presence of AlCl 3 to the methyl substituted derivative 16 (Scheme 5). Oxidation of 15 with catalytic tetrapropylammonium perruthenate (TPAP) and stoichiometric N-methylmorpholine-N-oxide (NMO) proceeded cleanly to give aldehyde 17 [5a] which was transformed into the 1-alkyne 18 as previously outlined [7b].…”

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

“…However, yields of [Co(h 4 -C 4 Ph 4 )(h 5 -C 5 H 4 R)] vary considerably as a function of R and although both 2 and 3 are desirable entry compounds, the yield of 2 (R ¼ CO 2 Me) at 67% is greater than that of 3 (R ¼ CHO) at 16%. 3 can be prepared from 2 in much higher yields (60% based on [Co(PPh 3 ) 3 Cl]) by reduction to the primary alcohol 4 (Scheme 2) and subsequent oxidation to 3 [9,24].…”

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

“…Previous reports have focussed on the readily available ester, (C 4 Ph 4 )Co(C 5 H 4 -CO 2 Me) [22], which, when treated with Grignard or organo-lithium reagents, yields the symmetrical alcohols (C 4 Ph 4 )Co(C 5 H 4 -CR 2 OH), where R ¼ H, Me or Ph [23]. Careful oxidation of the primary alcohol furnishes the aldehyde (C 4 Ph 4 )Co (C 5 H 4 -CH@O) [24]. The carbinol (C 4 Ph 4 )Co(C 5 H 4 -CPh 2 OH) had been previously prepared by the reaction of (C 4 Ph 4 )Co(C 5 H 4 Li) with benzophenone [4].…”