A #pi#-Stacked Organometallic Propeller: Experimental and Theoretical Studies on Reacitivity and Bonding in the #pi#-Arene-Bridged Nickel Triple-Decker [{(#eta#~5-Me_4EtC_5)Ni}_2(#mu#-#eta#~3:#eta#~3-decacyclene)]

摘要

Synthesis, structure, reactivity, and theoretical studies of a new type of Ni triple-decker complexes are reported. A prominent feature of its molecular structure is the (1]3:1]3)-bis- (enyl) coordination of two [(1]5-Me4EtC5)Ni] fragments to the central arene ring of the polycondensed 7t-perimeter decacy- clene. The central arene ring of decacyclene displays a dis- tinct chair conformation with significant tilt angles of 25.5 and 26.1°. The three naphthalene units are twisted in a pro- peller-like fashion with torsion angles of 16°, 16.6°, and 19°, which is twice the twisting observed for the free decacyclene ligand. According to Extended Hiickel Molecular Orbital (EHMO) calculations, a qualitative measure for arene lability in the title compound and a number of related arene-bridged metal complexes can be attributed to a subsequent filling of metal-arene antibonding orbitals. The experimentally ob- served reactivities of 7t-arene exchange in these complexes are reproduced nicely by the EHMO calculations. The title compound offers access to a number of organonickel chalco- genato complexes under mild conditions by cleavage of the S-S, Se-Se, or Te-Te bonds of diorganyl dichalcogenides R-E-E-R. The title compound is also capable of Csp2-H ac- tivation of azobenzene and [(dimethylamino)methyl]ferro- cene resulting in orthometallated complexes containing five- membered metallacycles. PES and semi-empirical ZINDO/S calculations were used to study the product of the orthomet- allation of the title compound with azobenzene. These stud- ies reveal that the HOMO of the metallacycle (IE = 6.45 eV) has dominant Ni-Cp and Ni-Carvl 7t-antibonding character.