Synthesis and Reaction of Mn II Iodides Bearing the β‐Diketiminate Ligand: the First Divalent Manganese N‐Heterocyclic Carbene Complexes [{HC(CMeNAr) 2 }MnI{C[N( i Pr)CMe] 2 }] and [{HC(CMeNAr) 2 }MnNHAr{C[N( i Pr)CMe] 2 }] (Ar = 2,6‐ i Pr 2 C 6 H 3 )

The manganese mono‐iodide [HC(CMeNAr) 2 ]MnI(THF) (Ar = 2,6‐ i Pr 2 C 6 H 3 ) ( 3 ) was prepared in good yield from the reaction of [HC(CMeNAr) 2 ]K with MnI 2 in THF. Treatment of 3 under reflux in toluene and removing all the volatiles in vacuo afforded the dimeric compound [{HC(CMeNAr) 2 }Mn] 2 (μ‐I) 2 ( 4 ). Displacement of the coordinated THF in 3 by a strong Lewis base C[N( i Pr)CMe] 2 or by adding C[N( i Pr)CMe] 2 to the toluene solution of 4 readily gave the N‐heterocyclic carbene adduct [{HC(CMeNAr) 2 }]MnI{C[N( i Pr)CMe] 2 } ( 5 ). Reduction of 5 with sodium/potassium alloy at room temperature unexpectedly resulted in the formation of the monomeric compound [{HC(CMeNAr) 2 }]MnNHAr{C[N( i Pr)CMe] 2 } ( 6 ). Alternatively 6 was obtained by the salt elimination reaction of 5 with LiNHAr. Compounds 5 and 6 are the first examples of divalent manganese N‐heterocyclic carbene adducts and the first manganese non‐carbonyl carbene complexes. The single crystal X‐ray structural analyses reveal that compounds 3 and 6 are monomeric and compound 4 is dimeric in the solid state. The manganese centers in these compounds exhibit a distorted tetrahedral geometry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)