Transition-Metal Complexes of Arynes, Strained Cyclic Alkynes, and Strained Cyclic Cumulenes

Synthesis and structure of 1-metallacyclopent-3-yne complexes of group 4 metals

“…In particular, cyclopentynes, five-membered cyclic alkynes, are highly reactive and short-lived species. Hydrocarbyl cyclopentyne and thiacyclopentyne [4] have been prepared, and the formation was spectroscopically detected [5][6][7] or confirmed by trapping them by subsequent chemical reactions, such as 2 + 2 cycloaddition [8], metal complexation [9][10][11], and so on. However these compounds are so reactive that they have not been isolated in a pure form.…”

Synthesis, Structure, and Bonding of a Zirconocene–1,2‐Dehydro‐o‐carborane Complex

“…[1][2][3][4] The chemistry of its transitionmetal complexes has been extensively studied. [5,6] The first zirconocene-benzyne complex stabilized by PMe 3 was structurally characterized in 1986 (Scheme 1). [7] In sharp contrast, 1,2-dehydro-o-carborane, a three-dimensional relative of benzyne, was suggested as a reactive intermediate for the first time in 1990 by heating a lithium salt of o-bromocarborane.…”

“…[9] Reactivity studies showed benzyne and 1,2-dehydro-o-carborane to be quite similar in reactions with dienes. [8][9][10] In view of the rich chemistry of metal-benzyne complexes, [5,6] we are interested in the virtually undeveloped chemistry of metal 1,2-dehydro-o-carborane complexes. We report here the synthesis, single-crystal X-ray structure, and bonding of the first zirconocene-1,2-dehydro-o-carborane complex [ [11] was followed by treatment with 1 equiv of Li 2 C 2 B 10 H 10 to afford 1 as light-brown crystals in 60 % yield (Scheme 3).…”

Palladium-Catalyzed Cycloaddition Reactions of Arynes

“…Since then, complexes of arynes with a wide array of transition metals have been prepared, but in most cases only for structural studies [5][6][7][8][9] (Fig. 2).…”

“…Figure 3 shows some representative examples of aryne complexes of early transition metals that have been characterized by X-ray diffraction studies. The most useful procedure for the preparation of early transition metal complexes of type 13 is the thermal elimination of benzene or methane from diphenyl or arylmethyl compounds, respectively (12 and 14 in Scheme 1) [5][6][7][8][9]. At the end of the 1960s, the first studies of the reactivity of such a complex, specifically the aryne-titanocene complex 15, showed that it reacts with species such as alkynes, CO 2 , N 2 or selenium to form titanacycles [7].…”