Kinetic Destabilization of Metal-Metal Single Bonds: Isolation of a Pentacoordinate Manganese(0) Monoradical.

The 17e(-) monoradical [Mn(CO)5 ] is widely recognized as an unstable organometallic transient and is known to dimerize rapidly with the formation of a MnMn single bond. As a result of this instability, isolable analogues of [Mn(CO)5 ] have remained elusive. Herein, we show that two sterically encumbering isocyanide ligands can destabilize the MnMn bond leading to the formation of the isolable, manganese(0) monoradical [Mn(CO)3 (CNAr(Dipp2) )2 ] (Ar(Dipp2) =2,6-(2,6-(iPr)2 C6 H3 )2 C6 H3 ). The persistence of [Mn(CO)3 (CNAr(Dipp2) )2 ] has allowed for new insights into nitrosoarene spin-trapping studies of [Mn(CO)5 ].