A [2]catenane constructed around a rhodium(III) center used as a template

Rhodium(III) has been used as a templating metal center for building a [2]catenane. In the first stage, a Rh(phen)(2) motif has been incorporated into a large ring. Subsequently, a 2,2'-bipyridine derivative has been threaded through the ring, this process being driven by coordination of the chelate to the Rh(III) center. The formation of the second ring has been performed using the ring-closing metathesis approach. Contrary to the other catenanes synthesized around transition metals, the second ring is formed at the rear of the coordination unit which it contains, by cyclizing two flexible end-functionalized fragments attached at the 4 and 4' positions of the 2,2'-bipyridine chelate.