161587-80-0Relevant academic research and scientific papers
Insertion reactions of benzyne-nickel(0) complexes with acetylenes
Bennett, Martin A.,Wenger, Eric
, p. 1267 - 1277 (2008/10/09)
Complexes of nickel(0) containing η2-4,5-difluorobenzyne, Ni((1,2-η)-4,5-F2C6H2)(PEt 3)2 (10) and Ni((1,2-η)-4,5-F2C6H2)(dcpe) (11; dcpe = 1,2-bis(dicyclohexylphosphino)ethane, Cy2PCH2-CH2PCy2) have been synthesized by alkali-metal reduction of the appropriate (2-halogenoaryl)nickel(II) halides. Spectroscopic measurements (13C NMR, FAB-MS) indicate that 10, 11, and the parent benzyne complex Ni((1,2-η)-C6H4)(PEt3)2 (2) are monomeric, analogous to the structurally characterized species Ni((1,2-η)-C6H4)(Cy2PCH2CH 2PCy2). Complexes 2 and 10 undergo rapid intermolecular exchange with PEt3 at room temperature and react with disubstituted acetylenes by double insertion into the metal-benzyne bond to form 1,2,3,4-tetrasubstituted naphthalenes. With electrophilic acetylenes (MeO2CC2CO2Me, MeC2-CO2Me, HC2CO2Me, and CF3C2CF3) an aromatic cyclotrimer is also formed; exceptionally, hexafluorobut-2-yne also gives with 10 a phenanthrene derived from two benzyne units and the acetylene. The unsymmetrical acetylenes tert-butylacetylene and methyl 2-butynoate give rise to good regioselectivity in the resulting naphthalenes, the favored isomers being very dependent on the steric and electronic influence of the substituents. The dcpe complexes react similarly but more slowly with acetylenes, and with MeO2CC2CO2Me the monoinsertion complexes Ni{C(CO2Me)=C(CO2Me)C6H2R 2-o}(dcpe) (R = H, F) can be observed.
