Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole

Abstract

The inversion process of pyrrole, phosphole, arsole, stibole, and bismole is analyzed in detail by using ab initio and density functional techniques. The results are compared with the corresponding divinyl and diethyl compounds, HM(C2H3)2 and HM(C2H5)2, respectively (M = N, P, As, Sb, and Bi). The inversion barrier increases down the Group 15 elements and from the cyclic, via the divinyl to the diethyl compounds. The inversion process can be rationalized in terms of a second-order Jahn−Teller distortion using HOMO/LUMO energy differences. B3LYP calculations predict that fluorination of the pyrrole ring leads to nonplanar structures of both the tetra- and pentafluoropyrrole.

The Continuing Development of the Chemistry of Phospholes

“…Here the phospholide 112 is reacted with carbon dioxide, presumably to give first a phosphole-1-carboxylate (113), in which it appears that the carboxylate moiety acted as a migrating group. An important feature of 113 is that there are trimethylsilyl groups present at the 2,5-positions; they play a useful role, since the silyl groups can be transferred to the carboxylate ions formed at these positions to generate a new phospholide (114).…”

“…Related to the previous topic are theoretical studies on the magnitude of the pyramidal inversion barrier [102,113].…”

Arsole Aromaticity Revisited

“…The NICS results did attribute slight aromaticity to arsole; the NICS(0) and NICS(1) values for arsole were found to be 26% and 44% of the corresponding pyrrole values, respectively. In a recent paper by Pelzer et al [19], another geometry based descriptor, the Julg index [20], was calculated. In a recent paper by Pelzer et al [19], another geometry based descriptor, the Julg index [20], was calculated.…”

An Unusual Isomerization to Tetraazastiboles

“…While pyrrole is planar and can be referred to as an aromatic system, heavier Group 15 analogues of pyrrole are pyramidal and are therefore non-aromatic. [24] The most prominent structural features are summarized in Table 1 , [18] which indicates partial double-bond character for all of the NÀN bonds, with the N2ÀN3 bond being close to having a bond order of two. Although 4 seems to be predisposed to the release of molecular nitrogen, no fast decomposition was observed.…”