Double CH Activation of a Masked Cationic Bismuth Amide

Abstract

The transformation of C-H bonds into more reactive C-M bonds amenable to further functionalization is of fundamental importance in synthetic chemistry. We demonstrate here that the transformation of neutral bismuth compounds into their cationic analogues can be used as a strategy to facilitate CH activation reactions. In particular, the double CH activation of bismuth-bound diphenyl amide, (NPh ) , is reported along with simple one-pot procedures for the functionalization of the activated positions. The organometallic products of the first and second CH activation steps were isolated in high yields. Analysis by NMR spectroscopy, single-crystal X-ray diffraction, and DFT calculations revealed unusual ground-state properties (e.g., ring strain, moderate heteroaromaticity), and provided mechanistic insight into the formation of these compounds.

Intramolecular Metal⋅⋅⋅π‐Arene Interactions in Neutral and Cationic Main Group Compounds

“…Previous work hass uggested that this interaction may be described as "a highly polarised (Bi=N) double bond", supported by DFT calculations on model systemst hat show a small percentage of electron density is located at the bismuth. [9b] TheN -Bi-Cl angle (96.3(4)8/9 8.2(4)8)i ss imilart ot hose reported for the relatedb ismuth cations E. (2) N-Bi-X196.21 (6) 98.42 (7)97.33(6) N-Bi-X295.89 (6) 95.09(8)99.20 (6) (19) [a] 4a/4b X = Cl; 5a X = I.…”

“…[2] Amongt hese ligand systems, bulky secondary amides of the form [N(Ar*)(SiR 3 )] À (Ar* = bulky aryl group, R = aryl or alkyl) have received significant attention due to relatively simple synthetic access, and the ability to easily tune the steric bulk through modification of the substituents. [3] An added feature of this ligand class, in which the central aryl-group Ar* incorporates additional aromatic rings, is the ability to provide secondary (intramolecular) M···p-arene interactions (vide infra).O f particular relevance to this work, Jones andco-workersdemonstrated that ligands of this type ( Me Ar°= 2,6-(CHPh 2 ) 2 -4-MeC 6 H 2 )m ay be used to stabilizee lectrophilic germanium and tin cations through weak h 2 -arene interactions to the flanking phenylgroups (A, Figure 1). [4] Bismuth cations have recently garnered interest as highly electrophilic catalysts for ar ange of CÀCa nd CÀNb ond form-ing processes.…”

“…[5] More unusual reactivity hasa lso been observed, including, for example, double ortho-CÀHa ctivation of aryl substituents by a" masked"c ationic bismuth amide. [6] Possessing both al one pair of electrons and av acant p-orbital on the metal centre, cationic bismuth speciesa re predicted to have Lewis amphoteric properties and have consequently drawn close comparisons to carbenes. [7] However,s table twocoordinate bismuth cations of the type [R 2 Bi] + are rare, and often requirea dditional donor interactions to stabilize the reactive metal centre.…”

“…In this contributionw er eport neutral and cationic bismuth compounds containingt he bulky amide ligand, [N( tBu Ar°)(SiPh 3 )] À ( tBu Ar°= 2,6-(CHPh 2 ) 2 -4-tBuC 6 H 2 ). [11] Our motivation was to determine the role of Bi···p-arene interactions in the stabilization of low-coordinate species when additional phenylg roups from at riphenylsilyls ubstituent are present in the metal coordinations phere.…”

“…Yield 0.59 g, 91 %. 1 H( 300 MHz): d = 7.96 (m, 6H, m-C 6 H 5 SiPh ), 7.41 (m, 9H, p-C 6 H 5 SiPh and o-C 6 H 5 SiPh ), 7.33-7.16 (br m, 12 H, C 6 H 5 and C6 H 2 ), 7.08-6.70 (br m, 10 H, C 6 H 5 ), 6.67 (s, 2H,C HPh 2 ), 3.62 (m, 6H,T HF-CH 2 ), 1.40 (s, 9H,C Me 3 ), 1.56 ppm (m, 6H,T HF-CH 2 ) 13. C{ 1 H} (75 MHz)*: d = 145.2, 143.0, 140.1, 137.…”