Base induced P-C bond cleavage in a coordinated bis(dimethylphosphino)methane ligand

Treatment of fac-[Mn(CNR)(CO)3{(PMe2)2CH2}]ClO4 (1a R = Ph, R = tBu) with KOH produced the cleavage of one of the P-C bonds of the coordinated dmpm ligand, resulting in the formation of phosphine-phosphinite complexes fac-[Mn(PMe2O)(CNR)(CO)3(PMe3)] (2a,b). Alkoxides such as NaOMe and NaOEt promoted similar processes in 1a,b, yielding fac-[Mn(CNR)(CO)3(PMe3)(PMe2OR')]ClO4 (3a R = tBu, R' = Me; 3b R = Ph, R' = Me; 4a R = tBu, R' = Et; 4b R = Ph, R' = Et) derivatives. The phosphinite ligand in 2a, b can be sequentially protonated by addition of 0.5 and 1 equivalent of HBF4 leading to fac-[{Mn(CNR)(CO)3(PMe3)(PMe2O)}2H]BF4 (6a,b) and fac-[Mn(CNR)(CO)3(PMe3)(PMe2OH)]BF4 (5a,b), respectively.