Carbophosphazene-Supported Ligand Systems Containing Pyrazole/Guanidine Coordinating Groups

Carbophosphazene-based coordination ligands [{NC(NMe2)}2{NP(3,5-Me2Pz)2}] (1), [{NC(NEt)2}{NC(3,5-Me2Pz)}{NP(3,5-Me2Pz)2}] (2), [NC(3,5-Me2Pz)]2[NP(3,5-Me2Pz)2] (3), [{NCCl}2{NP(NC(NMe2)2)2}] (4), and [{NC(p-OC5H4N)}2{NP(NC(NMe2)2)2}] (5) were synthesized and structurally characterized. In these compounds, the six-membered C2N3P ring is perfectly planar. The reaction of 1 with CuCl2 afforded [{NC(NMe2)}2{NHP(O)(3,5-Me2Pz)}·{Cu(3,5-Me2PzH)2(Cl)}][Cl] (6). The ligand binds to Cu(II) utilizing the geminal [P(O)(3,5-Me2Pz)] coordinating unit. Similarly, the reaction of 2 with PdCl2 afforded, after a metal-assisted P−N hydrolysis, [{NC(NEt)2}{NC(3,5-Me2Pz)}{NP(O)(3,5-Me2Pz)}·{Pd(3,5-Me2PzH)(Cl)}] (7). In the latter, the [P(O)(3,5-Me2Pz)] unit does not coordinate; in this instance, the Pd(II) is bound by a ring nitrogen atom and a carbon-tethered pyrazolyl nitrogen atom. The reaction of 3 with PdCl2 also results in P−N bond hydrolysis affording [{NC(3,5-Me2Pz)2}{NP(O)(3,5-Me2Pz)}{Pd(Cl)}] (8). In contrast to 7, however, in 8, the Pd(II) elicits a nongeminal η3 coordination from the ligand involving two carbon-tethered pyrazolyl groups and a ring nitrogen atom. Metalated products could not be isolated in the reaction of 3 with K2PtCl4. Instead, a P−O−P bridged carbodiphosphazane dimer, [{NC(3,5-Me2Pz)NHC(3,5-Me2Pz)}{NP(O)}]2 (9), was isolated as the major product. Finally, the reaction of 5 with PdCl2 resulted in [{NC(OC5H4N)}2{NP(NC(NMe2)2)2}·{PdCl2}] (10). In the latter, the exocyclic P−N bonds are quite robust and are involved in binding to the metal ion. Compounds 6−10 have been characterized by a variety of techniques including X-ray crystallography. In all of the compounds, the bond parameters of the inorganic heterocyclic rings are affected by metalation.