in methanol (N2); soln. of metal compd. in dry MeOH was added to MeOH soln. of carboxylic acid (2:1 mol) at room temp. over a period of 15 min and stirred for 1 h; solvent removed in vac.; residue suspd. in warm MeOH, filtered and dried in vac. over silicagel; stored at 0°C in total darkness; elem. anal.;