Syntheses, Structures and Electronic Properties of Cationic Hydroxy‐ and Methoxy‐Substituted Tricarbonyl(tetracyclopropylcyclopentadienyl)iron Complexes

Abstract

Tetracyclopropylcyclopentadienone, upon liberation from its previously known tricarbonyliron complex 3, undergoes rapid [4+2] cyclodimerization to the highly congested1,2,4,5,6,7,8,9‐octacyclopropyltricyclo[5.2.1.02,6]deca‐4,8‐diene‐3,10‐dione (6) which was characterized by an X‐ray crystal structure analysis. Upon alkylation of 3 with Me3OBF4 as well as protonation with HBF4 or CF3SO3H, the remarkably stable cationic tricarbonyl(tetracyclopropylcyclopentadienyl)iron complexes 9, 10 and 11, 12, respectively, were obtained in high yields (91, 87 and 74, 79 %, respectively). X‐ray crystal structural data for 11 and 12 as well as NMR‐ and IR spectroscopic evidences for all four new complexes 9–12 indicate that their positive charge predominantly rest on the tricarbonyliron fragments. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Product Class 6: Oxonium Salts

“…[90] The anionic nucleophile can be varied to accommodate different functionalities, such as alkyl, [91,92] aryl, [82,93] amino, [94] or silyl groups. [95] Although not as common as the Fischer carbene preparation, there are examples of other metal-based O-alkylations using tungsten, [96] iron, [97] and rhenium. [98] [(Z)-1,2-Dimethoxybut-2-enylidene]pentacarbonylchromium (10): [81] CAUTION: A 2 M solution of tert-butyllithium in heptane ignites in moist air and reacts explosively with water.…”

Three-Membered-Ring-Based Molecular Architectures

“…Upon liberation from its tricarbonyliron complex 648 , tetracyclopropylcyclopentadienone undergoes rapid [4 + 2] cyclodimerization to the highly congested 1,2,4,5,6,7,8,9-octacyclopropyltricyclo[5.2.1.0 2,6 ]deca-4,8-diene-3,10-dione ( 652 ) (Scheme ), which was characterized by an X-ray crystal structure analysis . Alkylation of 648 with R 3 OBF 4 (R = Me, Et) as well as protonation with HBF 4 or CF 3 SO 3 H afforded the remarkably stable cationic alkoxy- and hydroxy-substituted tricarbonyl(tetracyclopropylcyclopentadienyl)iron complexes 653 − 656 in high yields (74−91%, Scheme ).…”

“…Treatment of 648 with cyclopropylmagnesium bromide gave the tricarbonyl(pentacyclopropylcyclopentadienyl)iron complex 657 in 48% yield (Scheme ); the latter, however, turned out to be unstable at ambient temperature, and attempted generation of the cationic tricarbonyl(pentacyclopropylcyclopentadienylium)iron complex from 657 by treatment with trifluoromethanesulfonic acid in dichloromethane at 0 °C was unsuccessful …”