Controlled translocation of palladium(ii) within a 22 ring atom macrocyclic ligandElectronic supplementary information (ESI) available: Crystal and refinement data for compounds H4L, [PdCl(H3L)] (3a), [Pd(N-(3-aminopropyl)caprolactam)(H2L)] (5) and [Pd(OH2)(H2L)] (6) in CIF format. CCDC 990384-990387. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4dt00765d

• Main Authors: Burgess, Michael G, Naveed Zafar, M, Horner, Stephen T, Clark, George R, James Wright, L
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt00765d

Double aza -Michael addition of n -butylamine to the two acrylamide groups of acyclic N 2 , N 6 -bis(6-acrylamidopyridin-2-yl)pyridine-2,6-dicarboxamide gives the corresponding macrocycle, H 4 L . H 4 L has potential coordination pockets associated with the 2,6-dicarboxamide (head) and the butylamine (tail) regions of the macrocycle. Depending on the conditions employed, macrocyclic complexes with palladium( ii ) coordinated to either the tail or the head of the macrocycle can be isolated. Thus, treatment of H 4 L with [PdCl 2 (NCPh) 2 ] and sodium acetate, or [Pd(OAc) 2 ] gives the closely related "tail-coordinated" complexes [PdCl(H 3 L)] ( 3a ) or [Pd(OAc)(H 3 L)] ( 3b ), respectively. However, employment of the bases 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or pyridine during the treatment of H 4 L with [Pd(OAc) 2 ] results in the "head-coordinated" complexes [Pd(NH 2 R)(H 2 L)] (NH 2 R = N -(3-aminopropyl)caprolactam, which is formed by hydrolysis of DBU) ( 5 ) or [Pd(OH 2 )(H 2 L)] ( 6 ), respectively. Translocation of the palladium ion from the macrocycle tail in 3b to the head occurs on treatment with either DBU or N -(3-aminopropyl)caprolactam. In both cases the product 5 is formed. The aqua ligand in 6 is labile and easily displaced by the N-donor ligands n -butylamine, N -(3-aminopropyl)caprolactam or DBU to give the corresponding complexes [Pd(NH 2 n Bu)(H 2 L)] ( 4 ), ( 5 ), or [Pd(DBU)(H 2 L)] ( 7 ). The data suggest that hydrolysis of DBU to produce the N -(3-aminopropyl)caprolactam ligand in 5 is catalysed by the acetic acid formed during ligand metallation rather than by coordination to palladium. The X-ray crystal structures of H 4 L , 3a , 5 and 6 are reported. Palladium can be directed to coordinate to the "tail" region of the macrocycle H 4 L to give 3b . Translocation of the palladium from the tail coordination pocket to the head coordination pocket occurs on treatment with amines such as n -BuNH 2 to give 4 .