The solid state aggregation of two gold(i) nitrate complexes

(Trimethylphosphine)gold(i) nitrate was prepared from the reaction of (Me3P)AuCl and AgNO3 in MeOH-CH2Q2. Single crystals from CH2Q2-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 ('BuNC)Au(ONO2) grown from CH2CI2-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.