This short review describes paths to superphanes with metal-stabilized cyclobutadiene and cyclopentadienone rings in a one-pot and stepwise fashion. The stepwise synthesis also led to a new class of belt-like systems with large rings composed of CpCo-stabilized cyclobutadiene rings connected with propane chains. Finally, our research yielded the first beltenes composed of alternating four-and eight-membered conjugated rings.A superphane is a phane in which all hydrogen atoms of the cyclic conjugated rings are tethered by bridges. This definition goes back to Boekelheide and Hopf [1]. So far, a number of superphanes with benzene rings, heterocycles, and metal-stabilized π-systems have been prepared [2]. Our affair with superphanes started with the reaction of cyclodeca-1,6-diyne 1 with CpCoL 2 , which afforded in a onepot reaction the superphane 2 (Scheme 1) [3]. This reaction was first extended to other cyclic alkynes such as cyclotetradeca-1,8-diyne [4] and cyclooctadeca-1,10-diyne [5]. The superphanes proved to be excellent starting materials for bridged cage hydrocarbons [6] and model compounds to study the interactions between two metal centers separated by chains of different lengths [7]. This encouraged us to design also a path for a stepwise synthesis of superphanes with four-and five-membered [8-10] rings as summarized in Scheme 2. The resulting superphanes are stable at room temperature, and their molecular structures were investigated. The intermediates 5-7, which were cyclized in an intramolecular reaction to 2 and 8-11, stimulated us to look for higher oligomers.

Cobalt studs the beltenes shown (R=H, CO2Me, SiMe3, 5 Me), which consist of annelated, conjugated four‐ and eight‐membered rings. These strained molecules were synthesized in a one‐pot reaction by a template supported trimerization of 5,6,11,12‐tetradehydrodibenzo[a,e]cyclooctene.

No abstract

Metal-stabilized belts: A torus, 3, consisting of three four- and three eight-membered conjugated rings and stabilized by (RCp)Co- and (RCp)Rh- units, was generated by irradiation of [(RCp)Co(CO)(2)] and [(RCp)Rh(C(2)H(4))(2)], respectively, and 1.Eleven metal stabilized [4.8](3)cyclacene derivatives were synthesized. The substances were prepared in one-pot reactions by irradiation of a solution of 5,6,11,12-tetradehydro-dibenzo[a,e]cyclooctatetraene and the corresponding cobalt reagents or rhodium compounds. The resulting cyclacene derivatives reveal D(3h) symmetry in solution. In the solid state the hoop shaped systems crystallize in layers, which are intercalated with solvent layers. To unravel the mechanism of the one-pot reaction we isolated an intermediate, which shows almost planar cyclooctatetraene rings.

No abstract