The presence of the azetidin-2-one ring in several widely used families of antibiotics, which include the penicillins and carbapenems, has stimulated considerable activity directed at the stereocontrolled synthesis of b-lactams. [1] One of the most popular methods is the [22] cycloaddition reaction of ketenes to imines (the Staudinger reaction). [2] The particular for sensory applications, and c) the incorporation of Mn into a cyclophane framework, which provides a more economical building block than Re for nonluminescent applications.
Experimental Section
Bimetallic [{(CO) 4 M} 2 BiBzIm] edges [15] (BzIm benzimidazolate) were formed by stirring [M(CO) 5 X] (M, X Mn, Br or Re, Cl) with K 2 [BiBzIm] [16, 17] at ambient temperature in CH 2 Cl 2 . At the reaction endpoint (monitored by FTIR), the solvent was partially removed and the desired [{(CO) 4 M} 2 BiBzIm] product precipitated as a yellow (1 a) or white (1 b) powder by addition of Et 2 O (45 % yield). [18] Rectangular cycles were obtained by reacting equimolar amounts of the bimetallic edge with 4,4'bpy in refluxing THF for two days. Hexanes were added to the flask after cooling to room temperature. Further cooling provided orange-yellow crystals (2 a) or a bright yellow powder (2 b) at $ 70 % yield. [19,20] Thin films of 2 a and 2 b were cast evaporatively from filtered THF/CHCl 3 (1/1) solutions.
Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-139036.
Copies of the data can be obtained free of charge on application to CCDC,