title: Carbophosphazene-supported ligand systems containing pyrazole/guanidine coordinating groups.
abstract: Carbophosphazene-based coordination ligands [{NC(NMe(2))}(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(NMe(2))(2))(2)}] (4), and [{NC(p-OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}] (5) were synthesized and structurally characterized. In these compounds, the six-membered C(2)N(3)P ring is perfectly planar. The reaction of 1 with CuCl(2) afforded [{NC(NMe(2))}(2){NHP(O)(3,5-Me(2)Pz)}·{Cu(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 PdCl(2) afforded, after a metal-assisted P-N hydrolysis, [{NC(NEt)(2)}{NC(3,5-Me(2)Pz)}{NP(O)(3,5-Me(2)Pz)}·{Pd(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 PdCl(2) 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 η(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 K(2)PtCl(4). 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 PdCl(2) resulted in [{NC(OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}·{PdCl(2)}] (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.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India. vc@iitk.ac.in
authors.forename: Vadapalli
authors.initials: V
authors.lastname: Chandrasekhar
authors.forename: Venkatasubbiah
authors.initials: V
authors.lastname: Krishnan
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Azhakar
authors.forename: Tapas
authors.initials: T
authors.lastname: Senapati
authors.forename: Atanu
authors.initials: A
authors.lastname: Dey
authors.forename: R
authors.initials: R
authors.lastname: Suriya Narayanan
mesh_terms: D018360:Crystallography, X-Ray; D019791:Guanidine / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011720:Pyrazoles / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D008024:Ligands; D009943:Organophosphorus Compounds; D011720:Pyrazoles; C031280:pyrazole; D019791:Guanidine