GOLD(I) CLUSTERING AT THE TRIPHENYLPHOSPHINIMINE NITROGEN ATOM

The nitrogen atoms of phosphinimines R(3)P=NH can function as clusteri ng centers for (ligand)gold(I) units to give di- and trinuclear comple x cations. Salts containing these novel cations are best prepared from the reactions of silylated phosphinimines R(3)P=NSiR(3)' (R = Ph, R' = Me) with the corresponding aliquots of tris[(phosphine)gold] oxonium tetrafluoroborates [(Ph(3)P)Au]3O+BF4- or (phosphine)gold tetrafluoro borates [(Ph(3)P)Au](BF4-)-B-+. Attempts to use a Staudinger reaction of a mu-azido-bis [(phosphine) gold] tetrafluoroborate [(Ph(3)P)Au]2N3 +BF4- with triphenylphosphine as an alternative preparative pathway we re unsuccessful and afforded only [(Ph(3)P)(2)Au]BF4. All products hav e been characterized by analytical and spectroscopic data. The crystal structures of: (1) {Ph(3)PN [Au(PPh(3))](2)}(BF4-)-B-+ . THF; (2) {Ph (3)PN[Au(PPh(3))](2)}(3BF4-)-B-2+ . THF . 2CH(2)Cl(2); and (3) [(Ph(3) P)Au]2N3+BF4- have been determined. In all three compounds the gold at oms are in close intramolecular contacts indicating significant metal- metal interactions (auriophilicity). Accordingly, the angles at nitrog en are found to be smaller than expected for trigonal planar (1), (3) or tetrahedral (2) coordination. The dication of (2) is isoelectronic and isostructural with the triply aurated phosphonium cation {Ph(3)PC[ Au(PPh(3))](3)}(+). The isolobality concept relates the cation of comp ound (1) with standard aminophosphonium cations like Ph(3)PNH(2)(+)(H/LAu(+)). There is no isolobal analogue for the dication in (2), howev er, and this result suggests that the cluster formation of gold contri butes significantly to the stability of polyaurated species.