Reactions of Metallacyclopentadiene with Terminal Alkynes: Isolation and Characterization of Metallafulvenallene Complexes

Abstract

Metallacyclopentadienes play an important role in transition-metal-catalyzed cyclotrimerization of alkynes. Isolation and characterization of these unique five-membered metallacycles could promote further understanding of related catalytic reactions. In this work, the first metallafulvenallene complexes were synthesized by the reaction of fused metallacyclopentadiene with terminal alkynes. Single-crystal X-ray diffraction and NMR spectroscopic studies on the metallafulvenallene complexes demonstrate that the bicyclic framework consists of a metallacyclopentadiene fused with a six-membered metallacycle, featuring an η1-vinylidene ligand. Deuterium labeling experiments were carried out to investigate the mechanism for the transformation of fused metallacyclopentadiene to fused metallafulvenallene. The UV–vis absorption spectra of these unique structures were measured.

Direct amidation of metallaaromatics: access to N-functionalized osmapentalynes via a 1,5-bromoamidated intermediate

“…In addition, the H3 proton signal (d ¼ 6.22 ppm) is also moved upeld compared with that of 1 (d ¼ 8.11 ppm) and previously reported metallapentalenes (ca. 7-9 ppm), 19 but is comparable with those observed in osmacyclopentadiene derivatives (d ¼ 6.41 ppm) 20. Notably, the 13 C{ 1 H} NMR and DEPT-135 spectra conrmed the C1 as a quaternary carbon at d ¼ 198.3 ppm.…”

“…7–9 ppm), 19 but is comparable with those observed in osmacyclopentadiene derivatives ( δ = 6.41 ppm). 20 Notably, the 13 C{ 1 H} NMR and DEPT-135 spectra confirmed the C1 as a quaternary carbon at δ = 198.3 ppm. The chemical shift is upfield compared with those found for related osmacyclopentadienes ( ca.…”

“…δ = 218–235 ppm) due to the bromide attached at C1. 20,21 The resonances of the two carbonyl carbons in the substituted imide group were observed at δ = 169.7 and 166.2 ppm, respectively. The 31 P{ 1 H} NMR spectrum shows signals from the two phosphorus atoms at δ = −22.68 and −21.11 ppm, respectively.…”

“…The chemical shi is upeld compared with those found for related osmacyclopentadienes (ca. d ¼ 218-235 ppm) due to the bromide attached at C1 20,21. The resonances of the two carbonyl carbons in the substituted imide group were observed at d ¼ 169.7 and 166.2 ppm, respectively.…”

Recent Advances in the Reactions of Cyclic Carbynes

“…In contrast to the 16-electron osmapentalene 52 secured by protonation [54], 18-electron osmapentalenes 62 and 63 were achieved by the nucleophilic attack of the methanethioxide (MeS − ) and the methanoxide (MeO − ) anions towards the carbyne carbon of osmapentalyne 50a under the atmosphere of carbon monoxide. [54] Xia and coworkers reported the transformation of osmapentalyne to osmafulvenallene 64 (Scheme 14), which constituted the pioneering example of well-characterized metallafulvenallenes [58]. The rationale of the mechanism is depicted in Scheme 15.…”