Synthesis, Structure, and Reactions of (Acylimino)triaryl-λ⁵-bismuthanes:  First Comparative Study of the (Acylimino)pnictorane Series

Abstract

The synthesis, structure, and reactions of (acylimino)triaryl-lambda(5)-bismuthanes and a comparative study of the structure and reactivity of a series of (acylimino)pnictoranes are reported. Treatment of ortho-substituted triarylbismuth dichlorides 1 (Ar(3)BiCl(2); Ar = 2-MeC(6)H(4), 2-MeOC(6)H(4), 2,4,6-Me(3)C(6)H(2)) with amides 2 (H(2)NCOR; R = CF(3), CCl(3), 3,5-(CF(3))(2)C(6)H(3)) in the presence of 2.2 equiv of KO-t-Bu in dichloromethane afforded (acylimino)triaryl-lambda(5)-bismuthanes 3 (Ar(3)Bi=NCOR) in yields of 77-96%. The ortho-substituted aryl ligands and the electron-withdrawing N-substituents afford kinetic and thermodynamic stabilization, respectively, to the reactive Bi=N bond. The structures and properties of a series of (acylimino)pnictoranes (Ar(3)M=NCOR and H(3)M=NCOCF(3); M = P, As, Sb, Bi) are compared by IR and (13)C and (15)N NMR, X-ray crystallography, and ab initio molecular orbital calculations. It was found that the contribution of the M(+)-N=C-O(-) canonical form becomes more prominent and the single-bond character of the M=N bond increases progressively as the pnictogen atom becomes heavier. The Bi=N bond of (acylimino)-lambda(5)-bismuthanes 3 possesses a highly polarized single-bond character, probably due to the differences in orbital size and electronegativity between the bismuth and nitrogen atoms. Thermal decomposition of (aroylimino)triaryl-lambda(5)-bismuthane 3f (o-Tol(3)Bi=NCOAr; Ar = 3,5-(CF(3))(2)C(6)H(3)) produces a gel in dry conditions or aniline 12 (ArNH(2)) in slightly wet conditions with a good recovery of tris(2-methylphenyl)bismuthane (4a). It is likely that the aryl isocyanate 13 (ArNCO) is produced during the thermolysis via a concerted C --> N migration of the Ar group with an elimination of the triarylbismuthonio group as bismuthane 4a. (Acylimino)triaryl-lambda(5)-bismuthanes 3 oxidize 1,1,2,2-tetraphenylethanediol, benzenethiol, methanol, and ethanol to benzophenone, diphenyl disulfide, methyl formate, and acetaldehyde, respectively, in two different reaction pathways depending on the structure of the substrates. Compound 3d (o-Tol(3)Bi=NCOCCl(3)) transfers the nitrenoid moiety to triphenylphosphane, triphenylarsane, and tris(2-methylphenyl)stibane to give the corresponding (acylimino)pnictoranes (Ar(3)M=NCOCl(3); M = P, As, Sb) and 4a, suggesting that 3d is thermodynamically much less stable than their lighter pnictogen counterparts. The copper-catalyzed decomposition of 3 (o-Tol(3)Bi=NCOR) afforded N-acyl-o-toluidines 18 (o-TolNHCOR) via a Bi --> N migration of the tolyl group. The observed reactivities of (acylimino)triaryl-lambda(5)-bismuthanes 3 demonstrate a good leaving ability of the bismuthonio group.

Diverse Structures and Remarkable Oxidizing Ability of Triarylbismuthane Oxides. Comparative Study on the Structure and Reactivity of a Series of Triarylpnictogen Oxides

“…These authors proposed the polymeric, oxo-bridged Bi−O−Bi network for this amorphous oxide on the basis of the IR spectra as well as their insolubility . Triarylbismuthane oxides were also obtained by oxygenation of the corresponding triarylbismuthanes with iodosylbenzene and by hydrolysis of triarylbismuthane imides …”

Structural studies of spiroarsoranes derived from 2-aminophenols

“…Also, the N3-C4 [1.414(6) Å for 5 and 1.405(3) Å for 6], N3A-C4A [1.389(5) Å for 5 and 1.391 (3) for 6], As2-N3 [1.818(4) Å for 5 and 1.809(2) Å for 6], and As2-N3A[1.799(4) Å for 5 and 1.799(2) Å for 6] bond lengths confirm that the N atoms have geometries closer to trigonal than to tetrahedral shapes [1,2,7,13]. However, the trigonal geometries of the nitrogen atoms no indicated the presence of As=N double bonds, the N-As lengths in 5-6 are larger than that bond distances reported for compounds with net As=N [17][18][19]. Contrary to what was observed by NMR, the X-ray studies indicate that the crystalline structures of 5 and 6 are not dissymmetric and that the As2-O1 and As2-N3 bond lengths are longer than those for As2-O1A and As2-N3A (Table 4).…”

A mini review on chemical fixation of CO2: Absorption and catalytic conversion into cyclic carbonates

“…[5][6][7][8]. In the past decade, there has been a rapid development on bismuth chemistry [9][10][11][12][13][14][15][16][17]. There are various researches on novel cationic organobismuth complexes and their applications [16][17][18][19][20][21][22][23].…”