Cyclic and High Polymeric nido-Carboranylphosphazenes as Ligands for Transition Metals

Article abstract of DOI:10.1021/ja00343a040

1-Methyl-1-(2-propynyl)-3,3,5,5-tetrachlorocyclotriphosphazene (6) reacts with bis(acetonitrile)-decaborane to yield 1-methyl-1-<(o-carboranyl)methylene>-3,3,5,5-tetrachlorocyclotriphosphazene (7).Species 7 was converted by base to the nido-carboranyl anion or dianion derivatives, which react with Rh(PPh3)3Cl or with Mo(CO)6 or W(CO)6 to form the appropriate (metallocarboranyl)phosphazene derivatives (10 or 12).Compound 7 polymerizes when heated, and the high polymeric analogues (13, 14, and 16) behave in a similar manner to the cyclotriphosphazene derivatives in the formation of metallocarboranyl derivatives.Species 7 is unusual in its reaction with piperidine.The four halogen atoms are replaced by piperidino groups, and a boron atom is removed from the cage, but an internal counterion at skeletal nitrogen is generated rather than the expected piperidinium ion.An X-ray structural investigation of this species (8) confirmed the presence of a planar cyclotriphosphazene ring linked to the carboranyl unit through a methylene spacer group.A proton was connected to the phosphazene skeletal nitrogen atom furthest from the carboranyl group.The P-N bonds adjacent to the site of the carborane attachment were of normal length (1.575 Angstroem), but the two bonds furthest from this site were exceptionally long (1.68 Angstroem), presumably a consequence of ring protonation.