The Aromatic 2-Iminomethylphenyltellurenyl Cation. A Lewis Superacid Despite the Intramolecularly Coordinating N-Donor Ligand

Abstract

The reaction of 2-(tBuNCH)C 6 H 4 TeCl with silver salts of weakly coordinating anions, AgX {X = O 3 SCF 3 , SbF 6 , or Al[OC(CF 3 ) 3 ] 4 }, provided the aryltellurenyl salts [2-(tBuNCH)-C 6 H 4 Te](O 3 SCF 3 ) (1), [2-(tBuNCH)C 6 H 4 Te](SbF 6 ) (2), and [2-(tBuNCH)C 6 H 4 Te]{Al[OC(CF 3 ) 3 ] 4 } (3), which comprise loosely associated ion pairs in the solid state. In solution, 1−3 undergo electrolytic dissociation into the tellurenyl cation [2-(tBuNCH)-C 6 H 4 Te] + ([4] + ) and the respective anions X − to various degrees, which was investigated by multinuclear NMR spectroscopy and conductivity measurements. The electronic structure of 1−3 and [4] + at both multiplicities (M = 1 and 3) was studied by DFT calculations using a set of real-space bond indicators. NICS calculations confirm the aromatic character of the central C 3 NTe ring in [4] + (M = 1). FIA calculations suggest that [4] + is a Lewis superacid.

Isolation of an Antiaromatic 9‐Hydroxy Fluorenyl Cation

“…In an effort to address this question, we calculated nuclear‐independent chemical shifts (NICS) for a number of aromatic and antiaromatic parents compounds (Figure 4). [18] The NICS(0) iso values of benzene and the cyclopentadienyl cation, determined at the ring critical points (rcp) are −8.08 and −13.14, whereas the NICS(1) iso values, referring to points perpendicular to the ring, 1 Å above the rcps are −10.21 and −10.45 [19] . Compared to these clearly aromatic benchmarks, the anti‐aromatic cyclopentadienyl cation shows the largest deviation with NICS(0) iso and NICS(1) iso values of 88.96 and 67.45.…”

“…[18] The NICS(0) iso values of benzene and the cyclopentadienyl cation, determined at the ring critical points (rcp) are À 8.08 and À 13.14, whereas the NICS(1) iso values, referring to points perpendicular to the ring, 1 Å above the rcps are À 10.21 and À 10.45. [19] Compared to these clearly aromatic benchmarks, the anti-aromatic cyclopentadienyl cation shows the largest deviation with NICS(0) iso and NICS(1) iso values of 88.96 and 67.45. Introduction of the hydroxyl group in 9position dramatically reduces these values to 25.89 and 16.25.…”

“…The identity of 1-3 was inferred by the full assignment of the 1 H and 13 C NMR spectra and confirmed by X-ray structure determination (Figure 1). [13] In solution, 1 is characterized by its 19 F NMR chemical shift (CDCl 3 ) of δ = 52.2 ppm. It reveals a doublet in the 13 C NMR spectrum for the ipso carbon atom at δ = 157.7 ppm with a coupling constant of 1 J( 13 CÀ 19 F) = 357.2 Hz.…”

Lewis Superacidic Tellurenyl Cation‐Induced Electrophilic Activation of an Inert Carborane

“…[3] Despite the N-donor coordination and the aromatic character of the five-membered C 3 NTe ring, I is a highly electrophilic Lewis superacid that gives rise to ion pairs even with weakly coordinating anions (WCAs). [3] These ion pairs , which is known as robust entity with a very low reactivity. [4] However, the salt metathesis reaction of 2-(tBuNCH)C 6 H 4 TeCl (II) [5] with Ag[CB 11 H 12 ] [6] provided again a contact ion pair [2-(tBuNCH)C 6 H 4 Te][CB 11 H 12 ] (1), which was isolated as yellow crystals in 99 % yield (Scheme 1, Figure 2).…”

“…I). [3] (tBuNCH)C 6 H 4 Te][Al{OC(CF 3 ) 3 } 4 ] (2.051(4) Å). The cation and anion of 1 are associated by a prominent Te•••H contact (2.550(1) Å) with the BÀ H functionality in the B12 position.…”