A novel dimanganese complex linked by an unusually strong hydrogen bond. X-ray structure of the hydrogen-bonded complex and ab initio calculations

In an attempt to prepare the fluoro complex (CO)3(dppe)MnF (3) by treating a CH2Cl2 solution of the aqua complex [(CO)3(dppe)Mn(OH2)]BF4 (1) with NaF(aq), we isolated instead, the dimanganese complex, [(CO)3(dppe)Mn(OH2)⋯FMn(dppe)(CO)3]BF4 (2). The two moieties, 1 and 3, are held together by an unusually strong O–H⋯F hydrogen bond (O⋯F=2.458(3) Å, H⋯F=1.52 Å) between the aqua ligand on one manganese and the fluoro atom on the other manganese. Using as a simple model the interaction between +Li(H2O) and FLi, the hydrogen bonding distance O–H⋯F was calculated to be; O⋯F=2.443 Å. Authentic 3 was prepared in a homogeneous system using CH2Cl2-soluble [Et4N]F.