A Family of Multiply Bonded Dimolybdenum Boraamidinates with the Formal Mo−Mo Bond Orders of 3, 4, 4.5, and 5

A boraamidinato ligand [PhB( N ‐2,6‐ i Pr 2 C 6 H 3 ) 2 ] 2− was employed to stabilize a new family of multiply bonded dimolybdenum complexes [MoCl(μ‐κ 2 ‐PhB( N ‐2,6‐ i Pr 2 C 6 H 3 ) 2 )] 2 ( 4 ) and [Mo(μ‐κ 2 ‐PhB( N ‐2,6‐ i Pr 2 C 6 H 3 ) 2 )] 2 n − ( n =0 ( 5 ), 1 ( 6 ), 2 ( 7 )), with the respective formal Mo−Mo bond orders of 3, 4, 4.5, and 5. Each metal center in 5 – 7 is two‐coordinate with respect to the ligands. Of particular interest is the quadruply bonded dimolybdenum complex  5 , featuring an unprecedented angular conformation. The bent Mo 2 N 4 core of 5 distorts toward planarity upon reduction. As a result, compound  7 features a planar Mo 2 N 4 core, while that of 6 is still bent but less significantly than that of 5 . Additionally, the Mo−Mo bond lengths of 4 – 7 systematically decrease as the valency of the central Mo 2 units decreases. Complex  7 features the shortest Mo−Mo bond length (2.0106(5) Å) yet reported.