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 MnMn 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 MnMn bond leading to the formation of the isolable, manganese(0) monoradical [Mn(CO) 3 (CNAr Dipp2 ) 2 ] (Ar Dipp2 =2,6‐(2,6‐( i Pr) 2 C 6 H 3 ) 2 C 6 H 3 ). The persistence of [Mn(CO) 3 (CNAr Dipp2 ) 2 ] has allowed for new insights into nitrosoarene spin‐trapping studies of [Mn(CO) 5 ].