Über die darstellung methyl-substituierter cyclobutadieneisen-tricarbonyle

Cyclobutadienemetal complexes

“…The treatment of c/s-3,4-carbonyldioxycyclobutenes (51), 78 prepared by the irradiation of vinylene carbonate with alkynes, with either Fe2(CO)9 or, preferably, Na2Fe(CO)4 gave the parent cyclobutadieneiron tricarbonyl (3) as well as the iron tricarbonyl complexes with butylcyclobutadiene (52) and 1,2-dimethylcyclobutadiene (23)54 ligands (eq 1). This procedure was ultimately extended to the synthesis of methoxymethylcyclobutadieneiron tricarbonyl (53)79 and 1 -methy l-2-methoxy methy Icyclobutadieneiron tricarbonyl (54).80 In general, this technique affords the respective iron complexes in yields ranging from 25 to 50% depending on the organic precursor (51) which is utilized in the reaction. The reactions of alkynes with transition metal complexes in general and metal carbonyls in particular have been extensively studied during the last three decades.81 These reactions are known to afford a large variety of organic and/or organometallic products.…”

Brom-cyclobutadien-eisentricarbonyl / Bromo-cyclobutadiene-irontricarbonyl

“…und die aus den 13 C -H-Kopplungen abgeleitete übereinstimmende Hybridisierung von C(2) und C(4) sind angesichts des Substituenten an C(l) unvereinbar mit einer Rechteckstruktur eines Cyclobutadiens mit alternierenden Doppel-und Einfachbindungen (hinsichtlich einer ausführlichen Beweisführung vgl. 1. c. [5][6][7][8] ).…”

Cyclobutadieneiron Tricarbonyl Annelated with Homoadamantene Frameworks

“…Modification of cyclic π-systems with these rigid frameworks has proven to be quite effective for the stabilization of the positively charged, open-shell π-systems due not only to electronic effects, such as the σ−π interaction (C−C hyperconjugation) and inductive electron donation, but also to Bredt’s rule protection, which prevents the loss of a hydrogen atom from the bridgehead carbons directly attached to the π-system. As for cyclobutadiene metal complexes, the donor ability of the cyclobutadiene ligand is tunable by the groups attached to it . Accordingly, the characteristics of transition metal complexes are expected to be tuned by the introduction of rigid σ-frameworks to the π-systems .…”