in toluene Mo4Br3(O-i-Pr)9 was dissolved in toluene under N2. At room temp. acetyl bromide was added to the solution. The flask was shaken vigorously and then allowed to stand at room temp. for 3 h.; The soln. was reduced in vol. by half and then slowly cooled to -15°C. After 2 d, crystals were obtained.;