Carbophosphazene-Supported Ligand Systems Containing Pyrazole/Guanidine Coordinating Groups
作者:Vadapalli Chandrasekhar、Venkatasubbiah Krishnan、Ramachandran Azhakar、Tapas Senapati、Atanu Dey、R. Suriya Narayanan
DOI:10.1021/ic102415x
日期:2011.3.21
Carbophosphazene-based coordination ligands [NC(NMe2)}(2)NP(3,5-Me(2)Pz)(2)}] (1), [NC(NEt)(2)}NC(3,5-Me(2)Pz)}NP(3,5-Me(2)Pz)(2)}] (2), [NC(3,5-Me(2)Pz)](2)[NP(3,5-Me(2)Pz)(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-Me(2)Pz)}center dotCu(3,5-Me(2)PzH)(2)(Cl)}] [Cl] (6). The ligand binds to Cu(II) utilizing the geminal [P(O)(3,5-Me(2)Pz)] coordinating unit. Similarly, the reaction of 2. with PdCl2 afforded, after a metal-assisted P-N hydrolysis, [NC(NEt)(2)}NC(3,5-Me(2)Pz)}NP(O)(3,5-Me(2)Pz)}center dotPd(3,5-Me(2)PzH)(Cl)}] (7). In the latter, the [P(O)(3,5-Me(2)Pz)] 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-Me(2)Pz)(2)}NP(O)(3,5-Me(2)Pz)}Pd(Cl)}] (8). In contrast to 7, however, in 8, the Pd(II) elicits a nongeminal eta(3) 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-Me(2)Pz)NHC(3,5-Me(2)Pz)}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)}center dotPdCl2}] (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.