Double C(sp³) dehydrogenation as a route to coordinated Arduengo carbenes: experiment and computation on comparative π-acidity

Double CH Bond Activation of C(sp3)H2 Groups for the Preparation of Complexes with Back‐to‐Back Bisimidazolinylidenes

“…All hydrogen and solvent (hexane) atoms have been omitted for clarity. Selected distances [] and angles [8]: Ir1-C1 2.017 (7), Ir1-Cl1 2.3509(19), Ir1-C46 2.107 (7), Ir1-C47 2.114 (8), Ir1-C42 2.202 (7), Ir1-C43 2.211 (7), Ir2-C3 2.018 (7), Ir2-Cl2 2.345(2), Ir2-C34 2.078(9), Ir2-C33 2.087 (9), Ir2-C38 2.202 (7), Ir2-C37 2.204 (7); C1-Ir1-Cl1 90.86 (18), .…”

“…In this regard, we believe that the design of new discrete multitopic carbenes that are poised to bind multiple transition metals may require new strategies for NHC generation.In certain cases, carbenes can be generated by double C À H bond activation of C(sp 3 )H 2 groups. [7][8][9] Although most of the known examples involve the transformation of cyclic ethers into traditional Fischer carbenes, [8] there is one example in which the double C(sp 3 ) dehydrogenation of a cyclic H 2 C(NRCH 2 ) 2 species afforded an Ru-NHC complex. [9] To check the general applicability of this alternative synthetic route to carbene complexes, we investigated the possibility that the N heterocycle 1 (Scheme 1) might react with iridium or rhodium complexes if a hydrogen acceptor was added to the reaction medium to facilitate the formation of the N-heterocyclic carbene.To our surprise, the reaction of 1 (R = Bn) with [{MCl-(cod)} 2 ] (M = Rh and Ir) in CH 3 CN at reflux afforded 2 a and 3 in moderate yields (38 % for 2 a, 45 % for 3) without the need to add a hydrogen acceptor.…”

“…[7][8][9] Although most of the known examples involve the transformation of cyclic ethers into traditional Fischer carbenes, [8] there is one example in which the double C(sp 3 ) dehydrogenation of a cyclic H 2 C(NRCH 2 ) 2 species afforded an Ru-NHC complex. [9] To check the general applicability of this alternative synthetic route to carbene complexes, we investigated the possibility that the N heterocycle 1 (Scheme 1) might react with iridium or rhodium complexes if a hydrogen acceptor was added to the reaction medium to facilitate the formation of the N-heterocyclic carbene.…”

Double CH Bond Activation of C(sp3)H2 Groups for the Preparation of Complexes with Back‐to‐Back Bisimidazolinylidenes

“…In certain cases, carbenes can be generated by double CH bond activation of C(sp 3 )H 2 groups 7–9. Although most of the known examples involve the transformation of cyclic ethers into traditional Fischer carbenes,8 there is one example in which the double C(sp 3 ) dehydrogenation of a cyclic H 2 C(NRCH 2 ) 2 species afforded an Ru–NHC complex 9.…”

Synthesis of a ruthenium bis(diisopropylamino(isocyano)borane) complex from the activation of an amino(cyano)borane

“…The N3-C8 (6a: 1.184(5); 6b: 1.186(5)) and N1-C1 (6a: 1.178(5); 6b: 1.173(5)) bond lengths are however similar, and are set at the upper limit for a coordinated isocyano CN group when compared with those in the only two reported crystal structures R 2 R 1 BNCCr(CO) 5 [29][30][31][32] They both exhibit a partial C-N triple bond character. The isocyano carbon ruthenium distances Ru1-C1 and Ru1-C8 are shorter than the sum of the single-bond covalent radii (2.00 Å), 33 thus suggesting a partially double bond character [34][35][36][37][38][39] as a result of the metal-to-ligand π-back bonding that takes place more effectively towards the isocyanoborane trans to the cyano group and involving a deviation from linearity of the CN-B axis at the N atom. The nitrogen boron distances in 6a/6b (1.335 < NB < 1.495 Å) are in the range of values observed for amino substituted trigonal-planar boron groups.…”