Microwave-Assisted Synthesis of Cyclopentadienyl–Cobalt Sandwich Complexes from Diaryl Acetylenes

Abstract

Sealed tube microwaVe dielectric heating of diaryl acetylenes with cyclopentadienyl cobalt dicarbonyl at eleVated temperature in p-xylene proVides access to metallocenes in both the cyclobutadiene (Ar 4 C 4 CoCp) and cyclopentadienone (Ar 4 C 4 (CdO)CoCp) families. When compared with the traditional thermal approach, the current method offers dramatically reduced reaction times and, especially with respect to cyclopentadienone complexes, increased yields. In the case of an especially bulky diarylacetylene the microwaVe approach allows access to a complex that cannot be readily obtained under traditional thermal conditions. An initial microwaVe-promoted Sonogashira coupling may be employed for in situ generation of the diarylacetylene, although lower yields of the metallocene complexes are ultimately obtained.

Air‐Stable {(C5H5)Co} Catalysts for [2+2+2] Cycloadditions

“…The synthesis of the {CpCo}‐complexed cyclobutadiene 7 was also accomplished under microwave irradiation, following a procedure described for diphenylacetylene and [CpCo(CO) 2 ] [Scheme , Eq. (2)] 21. Interestingly, the yield (83 %) was much better than that reported with [CpCo(CO) 2 ] (52 %), owing to a far lower contamination by the [2+2+1] adduct 8 (9 % vs. 40 % with [CpCo(CO) 2 ]).…”

Synthesis and characterization of difunctionalized derivatives of the cyclobutadiene linked dimeric cobalt sandwich compound [(η5-Cp)Co(η4-C4Ph3)]2

“…Some hydrogen atoms have been omitted for clarity. Selected bond lengths ( A) and bond angles ( ): Co(1)eC(2) 2.071(4), Co(1)eC(8) 1.985(4), O(1)eC(1) 1.410(7), C(1)eC(2) 1.491(7), C(2)eC(3) 1.424(7), C(7)eC(7) 1.450(8), C(7)eC(8) 1.468(6), C(7)eC(11) …”

The broad diversity of CpCo(I) complexes

“…With 2 as a starting compound, Hamilton and colleagues developed a microwave-assisted synthesis of CpCo(I)-sandwich complexes from diaryl acetylenes (Harcourt et al 2008). For all substituents, a mixture of the respective cyclobutadiene and cyclopentadienone complexes was found.…”