Phosphinidine Complexes of p Block Metals; New Routes to Cyclic Ligands and Zintl Phases

Abstract In contrast to the reactions of E(NMe 2 ) 3 (E=As, Sb, Bi) with [RNHM] (M=Li–Cs) which generate stable Group 15 imido anions (such as the dianions [E 2 (NR) 4 ] 2− and trianions [E(NR) 3 ] 3− ), the phosphide analogues formed in the analogous reactions using [RPHM] decompose readily to give Zintl compounds. This process is accompanied by the formation of [RP] n rings, indicating that the alloy-forming reaction is driven thermodynamically by the bond energy of P–P bonds. The apparent intermediates in this reaction are heterocyclic anions of the type [(RP) n E] – ( n =3 or 4). The latter are interesting new ligands for a range of metals, with the potential ability to behave as sources of metal atoms (E). The anions exhibit unusual reactivity with transition metal metallocenes, adding to the cyclopentadienyl rings in preference to the attack of metal–halogen bonds. In addition, the reactions of the cyclic anions with electrophiles (R′X) furnish a simple selective route to neutral oligophosphine ligands of the type [(RP) n R′ 2 ].