Phosphine-Linked Phosphazenes as Carrier Molecules for Transition-Metal Complexe

The phosphine-bearing poly((aryloxy)phosphazenes) [NP(OC6H4PPh2)x(OPh)2-I]n (la, where x =: 0.3, or lb, where x ⋍ 0.6) have been investigated as high polymeric ligands for binding to transition-metal species. The cyclic trimeric phosphazenes [NP(OPh)2]3 (2), N3P3(OC6H4PPh2)(OPh)5 (3), and [NP-(OC6H4PPh2)2]3 (4) were examined as model donors for comparisons with the high polymers. Species 1-4 were allowed to interact with AuCl, H2Os3(CO)10, Mn(CO)3(η-C5H5), Fe(C0)3(PhCH=CHC(O)CH3), and [RhCl(CO)2]2. Coordination of pendent phosphine units to all five metals occurred without interference from the skeletal nitrogen atoms. Both intra- and intermolecular complexation took place when the metal could accept two phosphine ligands. The NMR and infrared spectra of these complexes resembled those of the analogous (triphenylphosphine)metal complexes. The coordinated metals exerted a strong influence on the physical properties of the high polymers, with evidence being obtained for coordinative cross-linking. Evidence was also obtained for a facile ligand exchange process with the rhodium-bound species. The osmium-bound species N3P3(OC6H4PPh2Os3H2(CO)10)(OPh)5 (6), [NP(OC6H4PPh2Os3H2(CO)10)2]3, and [NP(OC6H4PPh2Os3H2(CO)10)o.3(OPh)li7], (11) function as catalysts for the isomerization of 1-hexene to 2-hexene.