Isolation and structural characterization of [P(AuPPh(3))(5)][BF4](2) via cleavage of a P-P bond by cationic gold fragments: Direct evidence of the structure of the elusive tetrakis[phosphineaurio(I)]phosphonium(+) cation

The reaction of [(Ph(3)PAu)(3)O]BF4 with P-2(SiMe(3))(4) in a 2:1 ratio results in cleavage of the P-P bond and formation of the pentacoordinate dication [P(AuP-Ph(3))(5)](2+) in moderate yield. Low temperature P-31 NMR studies indicate that the gold atoms are equivalent in solution. However, the solid state molecular structure of this homoleptic dication is square pyramidal rather than the classically expected trigonal bipyramid.