Unexpected 1,2‐Migration in Metallasilabenzenes: Theoretical Evidence for Reluctance of Silicon to Participate in π Bonding

Abstract

Density functional theory (DFT) calculations were carried out to investigate the 1,2-migration in metallasilabenzenes. The results suggested that the chloride migration of metallabenzenes is unfavorable due to the loss of aromaticity in the nonaromatic analogues. In sharp contrast, such a migration in metallasilabenzenes is favorable due to the reluctance of silicon to participate in π bonding. The migration of hydride and methyl group from the metal center to the silicon atom in metallasilabenzenes is computed to be also feasible. In addition, the π donor ligand and the third row transition metal can stabilize metallasilabenzenes. Thus, such a migration becomes less favorable thermodynamically and kinetically. These findings could be very helpful for synthetic chemists to realize the first metallasilabenzene.

Adaptive Aromaticity in Metallasilapentalynes

“…49 Our group has reported the 1,2-migration in metallasilabenzenes, which provides evidence for the reluctance of silicon to participate in the π bonding theoretically. 50 Besides, the ACID plots for metallapentalyne with Fe in S 0 and T 1 are provided in Figures S21 and S22, indicating its aromaticity in the S 0 state and nonaromaticity in the T 1 state. ACID plots for osmapentalyne 13 and ruthenapentalyne 15 have been reported in our previous work.…”

“…Note that there are some conjugation defects between metal–silicon or silicon–carbon in the ACID plots (Figure ), which should be understandable as the silicon atom is unwilling to participate in π-bonding . Our group has reported the 1,2-migration in metallasilabenzenes, which provides evidence for the reluctance of silicon to participate in the π bonding theoretically . Besides, the ACID plots for metallapentalyne with Fe in S 0 and T 1 are provided in Figures S21 and S22, indicating its aromaticity in the S 0 state and nonaromaticity in the T 1 state.…”

Probing the Origin of Challenge of Realizing Metallaphosphabenzenes: Unfavorable 1,2-Migration in Metallapyridines Becomes Feasible in Metallaphosphabenzenes

“…To the best of our knowledge, metallaphosphabenzene has not been synthesized so far, although its structure and property were investigated theoretically 19 20 . The difficulties in the synthesis and isolation of metallaphosphabenzene could be due to the reluctance of phosphorus to participate in multiple bonds 21 , similar to our previous finding 22 that 1,2-migration in metallasilabenzenes becomes favorable due to the reluctance of silicon to participate in π bonding. Thus, 1,2-migration in metallaphosphabenzenes may also occur ( Fig.…”

Recent Advances in Metallaaromatic Chemistry

“…Analogues of benzene where one CH group is formally replacedb yamain group element are wellk nown and in many cases have been shown to retain as ignificant degree of aromatic character. [24][25][26][27] Some notable examples from recent years include bisma-, [28] alumina-, [29] sila-, [30][31][32][33] germa- [34] and stannabenzenes. [35] The prospect of p-delocalization in analogueso fb enzene that contain at ransitionm etal wasf irst considered theoretically by Thorn and Hoffmann.…”

“…Analogues of benzene where one CH group is formally replaced by a main group element are well known and in many cases have been shown to retain a significant degree of aromatic character . Some notable examples from recent years include bisma‐, alumina‐, sila‐, germa‐ and stannabenzenes …”