Ferrocene‐Based N‐Heterocyclic Carbenes with Functionalised Benzyl Substituents

Abstract

We describe herein N-heterocyclic carbenes (NHCs) with a 1,1Ј-ferrocenylene backbone that contain substituents at the nitrogen atoms relevant for applications in the area of metallopharmaceuticals, namely benzyl units functionalised with dimethylamino and methoxy groups at the para position. These carbenes are too unstable for isolation. They were generated from the corresponding formamidinium tetrafluoroborates by deprotonation and efficiently trapped in situ. Trapping with elemental selenium afforded the corre-

N‐tert‐Alkyl‐Substituted N‐Heterocyclic Carbenes with a 1,1’‐Ferrocenediyl Backbone

“…Similar structural features have been observed for closely related compounds such as, for example, fc(N=CH-p-C 6 H 4 -OMe) 2 . [41] Figure 5 and Figure 6 show the molecular structures of the diaminoferrocenes 4 b and 4 d. Note that the structures, but not the synthesis, of 4 a and 4 c had already been reported by us previously. [29,42] Similar to 4 a, [42] the molecules of 4 b and 4 d exhibit a synperiplanar conformation of the cyclopentadienyl rings with fairly small NÀ C ipso À C ipso À N torsion angles below ca.…”

Forever young: the first seventy years of ferrocene

“…Ferrocene-based carbenes from the second class are represented by structurally unique [3]ferrocenophane carbenes 69 146,147 and by compounds in which a cyclic carbene fragment is fused onto a ferrocene unit. Representative compounds of the latter type, as shown in Scheme 19, include the singly and doubly annellated imidazole derivatives 70 148 and 71 , 149 triazole 72 , 150 and amino-ferrocenyl carbenes 73 , 74 , 151 and 75 .…”

A Stable Crystalline N‐Heterocyclic Carbene with a 1,1’‐Ferrocenylene Backbone and BenzylicN‐Substituents

“…The structural features of diimine 3 b are similar to those of fc(NH=CH− p ‐C 6 H 4 −OMe) 2 [10] . The N imine atoms of 3 b each exhibit two significantly different C−N bond lengths, on average ca.…”

“…The molecular structure of diamine 4 b closely resembles that of fc(NH=CH− p ‐C 6 H 4 −NMe 2 ) 2 , [10] exhibiting crystallographically imposed inversion symmetry (molecular point group C i ), which is reflected in a fully staggered orientation of the cyclopentadienyl rings with diametrically opposed amino substituents. The C−N bond lengths of 1.397(6) and 1.462(6) Å are in accord with single bonds between an sp 3 ‐hybridised nitrogen atom and sp 2 ‐ and sp 3 ‐hybridised carbon atoms, respectively.…”

“…We have already published results for aryl= p ‐C 6 H 4 −X (X=OMe, NMe 2 ). These groups lead to fcNHCs too unstable for isolation, which, however, could be efficiently trapped by complexation at rhodium(I) or by reaction with elemental selenium [10] . We here describe our work with the pristine benzyl substituent (CH 2 Ph, Bn) and its mesityl‐containing homologue CH 2 Mes (Bn*).…”