Reaction of [fac-(CO)3(dppe)Mn(OH2)]BF4 with 13CO and conversion of the resulting tetracarbonyl to labeled isocyanato complexes

When 13CO is bubbled into a CH2Cl2 solution of [fac-(CO)3(dppe)Mn(OH2)]BF4 (dppe=Ph2PCH2CH2PPh2), the aqua ligand is replaced by the CO to give the tetracarbonyl, [(CO)3(13CO)(dppe)Mn]BF4 (1) in which the labeled CO appears exclusively at the site originally occupied by the aqua ligand. Treatment of this aqua complex with NaN3 leads to an approximate 50:50 mixture of isocyanates corresponding to attack, with equal probability, at either the labeled CO or its axial partner. Neither of the two CO groups trans to the P atoms in the tetracarbonyl are affected.