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-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 ((BuNC)-Bu-t)Au(ONO2) grown from CH2Cl2-pentane at -25 degreesC 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 degreesC) 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.