Carbophosphazene-Based Multisite Coordination Ligands: Metalation Studies on the Pyridyloxy Carbophosphazene, [NC(NMe2)]2[NP(p-OC5H4N)2]

The pyridyloxycarbophosphazene, [NC(NMe2)]2[NP(p-OC5H4N)2] (L), reacted with Cd(OAc)2·4H2O to afford a rail-road-like double-strand coordination polymer, [{Cd(CH3COO)2(L)}(CH3OH)(H2O)2]n (1). The crystal structure of 1 reveals that L functions as a bridging ligand to link successive cadmium atoms. Two such parallel-running strands are further interconnected by actetate bridging ligands forming Cd2O2 four-membered connections. The double-stranded coordination polymer is taken into the second dimension by intermolecular hydrogen bonding between the oxygen atoms of the acetate bridge and a tetrameric water cluster. Interaction of L with Cd(NO3)2·4H2O leads to the formation of [Cd(NO3)2(L)(MeOH)]n (2). In the presence of pyridine (Py), this reaction affords [Cd(NO3)2(L)(Py)2]n (3). In contrast to 1, compounds 2 and 3 are single-strand one-dimensional (1-D) coordination polymers. In 1−3, the cadmium atoms are seven-coordinate in a pentagonal−bipyramidal geometry. The reaction of L with ZnCl2, MnCl2, or CoCl2 leads to the formation of [{Zn(Cl)2(L)}(MeOH)]n (4), [Mn(Cl)2(L)2]n (5), and [Co(Cl)2(L)2]n (6). Structure 4 is a simple 1-D coordination polymer containing tetrahedral zinc atoms, while 5 and 6 are macrocycle-linked coordination polymers. In the latter, successive metal atoms are linked by a pair of carbophosphazene ligands to generate 24-membered macrocyclic rings which are interconnected to each other at the metal center to afford the coordination polymer chain.