Synthese und Struktur eines [Co2(CO)6]- komplexierten Propargylkations

Abstract

Nach vielen vergeblichen Bemühungen über zwei Jahrzehnte gelang nun die erste Kristallstrukturanalyse eines [Co2(CO)6]‐komplexierten Propargylkations, des BF4‐Salzes von 1. Das kationische Zentrum ist zwar nahezu ideal sp2‐hybridisiert, die Metallcluster weisen aber dennoch erheblich unterschiedliche Strukturen auf.

[Co2(CO)6(Alkynyl)] Complexes of Dibenzosuberyl and Dibenzosuberenyl Carbocations: Dibenzotropylium or Dibenzoheptafulvene?

“…Although [Co 2 (CO) 6 (propargyl)] cations are notoriously difficult to obtain as X‐ray‐quality crystals, replacement of a [Co(CO) 3 ] cationic fragment, as in 10 a or 11 a , by an isolobal neutral [Fe(CO) 3 ] unit yields neutral iron–cobalt complexes that are excellent structural models for the aforementioned dicobalt cluster cations. By using this approach, the mixed‐metal species [FeCo(CO) 6 {(fluorenylidene)=C=CSiMe 3 }] ( 13 ) and [FeCo(CO) 6 {(2,3‐diphenylindenylidene)=C=CSiMe 3 )}] ( 14 ) were prepared by the reaction of the appropriate [Co 2 (CO) 6 (alkynol)] cluster with [Fe(CO) 5 ] in acetone, and were characterised by X‐ray crystallography .…”

Density Functional Investigation of Reactive Intermediates Derived from Alkyne-Co2(CO)6 Complexes

“…The structural features of reactive intermediates of type 3 have been the subject of several investigations, but it proved difficult to determine the exact structure of such species experimentally (e.g., by X‐ray crystallography). Only for a compound in which a carbenium center is stabilized by two alkyne–Co 2 (CO) 6 fragments was an X‐ray structure reported 14. The structure of this cationic species is not significantly distorted with respect to those of neutral alkyne–Co 2 (CO) 6 complexes.…”

Hexasilylated Total Carbomer of Benzene

“…Indeed, the propargylic carbocations described by Nicholas are known to exhibit controlled reactivity,17 and Melikyan et al. showed that trialkynyl carbocations are stabilized by complexation to Co 2 (CO) 6 units 18. After several attempts to assist the aromatization of 15 with stoichiometric and substoichiometric amounts of a cobalt complex (competing complexation of the endocyclic triple bonds could not be ruled out), it was found that the use of only two equivalents of Co 2 (CO) 8, followed by treatment with SnCl 2 /HCl and direct oxidative decomplexation with ceric ammonium nitrate (CAN), afforded the hexaalkynyl carbobenzene 1 a in 12 % yield over three steps (Scheme ).…”