Transient generation of the reactive carbene complex [Cp(CO)2W = CH(Tol)]+ and its reactions with alkynes to form vinylcarbene, allyl, naphthol, diene, and metallafuran complexes

Abstract

271ChemInform Abstract Although the p-tolylcarbyne-W complex (I) does not itself react with alkynes, its protonation product, the title carbene, readily incorporates 1,2-diphenylacetylene (II) or 1,2-dimethylacetylene (IX) to give the vinylcarbene complex (III) and the η4-naphthol omplex (XI), respectively. The vinylcarbene complex (III) readily undergoes CO/I-substitution to yield the neutral vinylcarbene complex (V) (space group I2/a, Z = 8). With (BH4)-, (III) is converted into the allyl complex (VI). Treating (III) with the nitrone (VII) leads to the etallafuran complex (VIII) ( P21/n, Z=4) which possesses a planar metallafuran ring with bond distances in the ring implying delocalized bonding. The naphthol ligand from (XI) can be released by air oxidation. The naphthol ligand undergoes deprotonation to form the eutral allyl complex (XII). Reaction of the carbyne complex (XIII) with HBF4 in the presence of 1,2-dimethylacetylene (IX) under CO (X) leads to the formation of the diene complex (XIV) by benzannulation reaction from the carbyne, alkyne, and one CO ligand. The elevance of these various reactions to the general mechanism of naphthol formation from metal carbenes and alkynes is discussed.

Addition of alkynes and osmium carbynes towards functionalized dπ–pπ conjugated systems

“…4), a series of reactant osmapentalynes (1b-1g) were synthesized by the treatment of carbon ligands (L2-L7) with multiyne chains with OsCl 2 (PPh 3 ) 3 and PPh 3 , the different substituents at different positions appear not to affect the reaction (3,(31)(32)(33)(34)(35)(36). For instance, the R′ substituent can be styryl (3), phenyl (31)(32)(33), thienyl (34) or hydrogen (35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46), and the Y group can be CH 2 (31,34), O (32,35) or C(COOMe) 2 (33,36). The structures of all the above complexes were confirmed by NMR spectroscopy, EA and HRMS ( Supplementary Figs.…”

“…The reactions of M≡C and C≡C bonds tend to afford cycloaddition intermediates or products on account of their high degree of unsaturation. For example, the alkyne metathesis undergoes metallacyclobutadiene intermediates process 12-14 , and [2+2], [2+2+1], and [2+2+2] cycloaddition products have been widely published [26][27][28][29][30][31][32][33][34][35][36][37] . Acyclic products, however, have never been reported.…”

η3-Allyl carbonyl complexes of group 6 metals: Structural aspects, isomerism, dynamic behaviour and reactivity

“…Deserving a brief comment is related η 3 -vinylcarbene complex 38 (Scheme 8). [99] The latter is readily converted into corresponding allyl complex 39 when treated with a hydride-donating nucleophile, suggesting the possibility that the η 3 -vinylcarbene derived from 40 might be obtained from 33 with appropriate alkylsubstitution, or treatment with, e.g., Ph3C + (Scheme 8); indeed, it is intuitive to equate the observed agostic interaction (vide supra) in 33 as an arrested state on this hypothesised route to the respective η 3vinylcarbene. Vinylcarbene complexes are also relevant as their existence has been suggested in terminal nucleophilic substitution coordinated allylic moieties bearing C1-alkoxy or arylsulfonyloxy substituents.…”

Metallafurans and their synthetic chemistry

“…Tertiary amine oxide can also be used as oxidative reagent to prepare a-metallafuran. Geoffroy and co-workers [42] reported the reaction of vinylcarbene complex 86 with nitrone gave red a-metallafuran 87 in 55 % yield (Scheme 21). This reaction involved transfer of an oxygen atom from nitrone to the carbene ligand of 86 and deprotonation of the vinyl substituent.…”