Cationic Functionalisation by Phosphenium Ion Insertion

The reaction of [Cp ''' Ni(eta(3)-P-3)] (1) with in situ generated phosphenium ions [RR ' P](+) yields the unprecedented polyphosphorus cations of the type [Cp ''' Ni(eta(3)-P4R2)][X] (R=Ph (2 a), Mes (2 b), Cy (2 c), 2,2 '-biphen (2 d), Me (2 e); [X](-)=[OTf](-), [SbF6](-), [GaCl4](-), [BArF](-), [TEF](-)) and [Cp ''' Ni(eta(3)-P4RCl)][TEF] (R=Ph (2 f), tBu (2 g)). In the reaction of 1 with [Br2P](+), an analogous compound is observed only as an intermediate and the final product is an unexpected dinuclear complex [{Cp ''' Ni}(2)(mu,eta(3):eta(1):eta(1)-P4Br3)][TEF] (3 a). A similar product [{Cp ''' Ni}(2)(mu,eta(3):eta(1):eta(1)-P-4(2,2 '-biphen)Cl)][GaCl4] (3 b) is obtained, when 2 d[GaCl4] is kept in solution for prolonged times. Although the central structural motif of 2 a-g consists of a butterfly-like folded P-4 ring attached to a {Cp ''' Ni} fragment, the structures of 3 a and 3 b exhibit a unique asymmetrically substituted and distorted P-4 chain stabilised by two {Cp ''' Ni} fragments. Additional DFT calculations shed light on the reaction pathway for the formation of 2 a-2 g and the bonding situation in 3 a.