| 20235521 |
Ledger J, Boomishankar R, Steiner A: Aqueous Chemistry of Chlorocyclophosphazenes: Phosphates {PO (2)}, Phosphamides {P (O) NHR}, and the first Phosphites {PHO} and Pyrophosphates {(PO)(2) O} of These Heterocycles. Inorg Chem. 2010 Mar 16.
Cyclotriphosphazenes have been functionalized with various oxo-groups at one of the ring phosphorus atoms. Starting from geminal dichlorides (A) which are equipped with amino groups at the other two phosphorus atoms {(Z'(2) P)(2) N (3) PCl (2) (Z' = NHCy) and (Z''P)(2) N (3) PCl (2) (Z'' = {EtN (C (3) H (6)) NEt}), respectively}, phosphate (B), pyrophosphate (C), phosphamide (D), and phosphite (E) derivatives have been prepared. The zwitterionic phosphate (Z'(2) P)(2) N (3) H (2) PO (2) B is obtained via the 4-dimethylamino pyridine (dmap)-catalyzed hydrolysis of A in a biphasic mixture of aqueous KOH and tetrahydrofuran (thf). B contains a PO (2) moiety neighboring two protonated ring nitrogen sites. It crystallizes as the tetrahydrate (Z'(2) P)(2) N (3) H (2) PO (2).4H (2) O, which consists of a double helix: A helical chain of hydrogen bonded zwitterions is intertwined with a helical chain of water molecules. The reaction of A with only dmap in CHCl (3) produces the dication [(Z'(2) P)(2) N (3) P (dmap)(2)](2+), which binds two dmap ligands at one phosphorus atom. The tetrahydrate dehydrates at 160 degrees C in vacuo under formation of the pyrophosphate {(Z'(2) P)(2) N (3) HPO}(2) O C, which contains a O horizontal lineP-O-P horizontal lineO residue linking the two phosphazene rings. When heated in a mixture of aqueous KOH, primary amine, and thf, A undergoes a concurrent aminolysis-hydrolysis reaction, which gives the phosphamide (Z (2) P)(2) N (3) HP (O) NHR D featuring a P (=O) NHR residue. The corresponding reaction of A with alpha,alpha'-diamino-p-xylene in a 2:1 ratio leads to the formation of {(Z'(2) P)(2) N (3) HP (O) NHCH (2)}(2) C (6) H (4), in which two phosphamide moieties are linked by a xylylene bridge. Phosphites E containing PHO moieties are obtained via reduction of the dichloride with potassium and subsequent treatment with KOH. The product consists of a hexameric potassium complex, which features a central K (6) O (6) double cube arrangement and contains the anionic ligand [(Z''P)(2) N (3) PHO](-) that offers two bidentate N-P-O coordination sites. Addition of NH (4) Cl yields the neutral phosphite (Z''P)(2) N (3) HPHO. The title compounds are amphiphilic featuring hydrophilic NH and PO (x) moieties and hydrophobic alkyl groups. In addition, they show amphiprotic behavior via protonation/deprotonation at ring N atoms. |
31(0,1,1,1) |