Reactions of a quintuply bonded chromium dimer with alkynes

Abstract

Quintuply bonded [(H)L(iPr)Cr](2) reacts with alkynes RC≡CR (R = Me, Et, Ph, CF(3)) to form exclusively 1 : 1 adducts [(H)L(iPr)Cr](2)(RCCR). All products feature relatively short Cr-Cr distances (1.919-1.962 Å) and elongated C-C bonds (1.315-1.436 Å), consistent with [2+2] cycloaddition reactions. The hydrocarbon adducts are 4-membered metallacycles, the bridging alkynes of which are progressively skewed with respect to the Cr-Cr axis. In contrast, perfluoroalkyne adds across the metal ligand moiety.

Reactivity of Dialumane and “Dialumene” Compounds toward Alkenes

“…This result is different from the reaction of compound 1 with azo‐compounds, wherein the 4 e − reduction involved both the metal centers and the dianionic α‐diimine ligands 7. However, a similar metal‐centered‐reduction process was observed in the reduction of the alkyne into the alkenediyl compound by the quintuply bonded [( H LCr) 2 ] compound ( H L={(2,6‐ i Pr 2 C 6 H 3 )NCH} 2 ) 13…”

“…[7] However, a similar metal-centered-reduction process was observed in the reduction of the alkyne into the alkenediyl compound by the quintuply bonded [( H LCr) 2 ] compound ( H L = {(2,6-iPr 2 C 6 H 3 )NCH} 2 ). [13] A…”

Interconversion of Quadruply and Quintuply Bonded Molybdenum Complexes by Reductive Elimination and Oxidative Addition of Dihydrogen

“…So far, only a few reports have appeared in the literature concerning mainly the chemical properties of the Cr À Cr quintuple bond. Thus, these complexes feature interesting reactivity toward unsaturated molecules like N 2 O, [19] alkenes, and alkynes, [20,21] and are able to activate white phosphorous, yellow arsenic, and AsP 3 . [22] Similar to carbonÀcarbon double and triple bonds, the CrÀCr quintuple bond of an aminopyridinate complex undergoes facile carboalumination, to generate the corresponding Cr À Cr quadruple-bond derivative with formally monoanionic bridging CH 3 and AlMe 2 groups.…”

M5M – Key compounds of the research field metal–metal quintuple bonding

“…The 2 + 2 + 2 cycloaddition product is an intermediate in the catalytic formation of benzenes from alkynes [33][34][35]. Cycloaddition reaction between quintuply bonded chromium complexes and alkynes have been intensively investigated by the Theopold group and us [32a, 36] prior to this interesting observation of the Tsai group. There, 2 + 2 cycloadditions are the dominating outcome.…”