PREORGANIZED BIS-ETHYNES - MOLECULAR PI-TWEEZERS

Preorganized Bis‐ethynes: Molecular π‐Tweezers? 1,8‐Bis[(arylethynylphenyl)]naphthalenes of type V (e.g. 10, 11) and 1,8‐bis[(arylethenylphenyl)]naphthalenes (6, 6a, 7, 7a) were synthesized for the first time. In contrast to the known 1,8‐bis(arylethynyl)naphthalenes VI their “stereologs” 10 and 11 are thermally stabile. Yet they react with pentacarbonyliron to yield dinuclear transition metal complexes of the type 12, 13, i.e. a strained cyclophane macrocycle is formed by C‐C bond formation. The X‐ray analysis of the di‐tert‐butyl compound 11 shows that the peri substituents diverge, but with increasing distance from the naphthalene skeleton one of the arylethynyl units is bent to the opposite direction (Figure 2). The question whether the new molecular skeleton V can be viewed as molecular tweezers is discussed: as the hydrocarbons react irreversibly with transition metal carbonyls, they may rather be taken as “tweezers for single use”. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim