The solid state aggregation of two gold(I) nitrate complexes †

Abstract

(Trimethylphosphine)gold(I) nitrate was prepared from the reaction of (Me3P)AuCl and AgNO3 in MeOH–CH2Cl2. Single crystals from CH2Cl2–pentane contain trimers [(Me3P)Au(ONO2)]3 as sub-units of polymeric chains. The organization is based on short aurophilic Au–Au contacts. A discussion considering all other known (Me3P)AuX structures leads to the conclusion that small, electronegative anions X favour aurophilic multi-coordination with longer Au⋯Au contacts, while less electronegative, bulky groups X induce dimerization with short Au⋯Au contacts. In all cases neighbouring molecules are arranged with their principal axes roughly perpendicular (staggered). Crystals of (tBuNC)Au(ONO2) grown from CH2Cl2–pentane at −25 °C were shown to be a 2∶1 dichloromethane solvate with a new meander-type structure, which is stable only at low temperature and under the standard pressure of a dichloromethane atmosphere. The structure is based on aurophilic interactions of a similar nature as in the solvent-free phase (obtained at 5 °C) as judged from the bond distance parameters, but the solvent molecules are accommodated in cavities formed through a different puckering of the chains. A comparison with other structures of (RNC)AuX molecules suggests that the parallel (eclipsed) head-to-tail alignment of the molecules is the preferred organization in the absence of other structure-determining effects.