Flexibility and anion exchange of [(X)@PdL] cages for recognition of size and charge of polyatomic anions

The self-assembly of Pd(NO 3 ) 2 with L (L = 1,2-bis(dimethyl(pyridin-3-yl)silyl)ethane) gives rise to [PdL 2 ](NO 3 ) 2 in high yields. Anion exchange of [PdL 2 ](NO 3 ) 2 with X − (X − = BF 4 − , ClO 4 − , and PF 6 − ) changes the skeleton into a cage of [(X)@Pd 2 L 4 ](X) 3 . Successive anion exchange of [(X)@Pd 2 L 4 ](X) 3 (X − = BF 4 − , ClO 4 − , and PF 6 − ) with X − (X − = ReO 4 − and SiF 6 2− ) produces [(ReO 4 )@Pd 2 L 4 ](ReO 4 ) 3 and [(SiF 6 )@Pd 2 L 4 ](SiF 6 ), respectively, irrespective of anion charge. The flexible nature and conformation of cages are significantly dependent on the nestled polyatomic anions. Thus, this system can be used as a molecular recognizer of the size and charge of ubiquitous polyatomic anions. A system of a Pd 2 L 4 coordination cage was constructed, and the cage is an efficient gauge for the recognition of ubiquitous polyatomic anions.