The H•••H interaction in the solid state structure of HMn(CO)5

HMn(CO)(5) is an interesting complex which forms H...H bonded dimers in the crystal, with a separation of 2.292 Angstrom. In previous work, this interaction was explained on the basis of EH calculations and the geometry was partly reproduced by DFT calculations. HF and MP2 calculations were performed in several possible HMn(CO)5 dimers and led to the conclusion that the H...H bonded dimers interact more strongly than ones with a H...O close contact. The formation of the dimer was studied with the two H-Mn-C-alphax axes approaching linearly or at the experimental angle (155.8degrees), the first being more stable but exhibiting too short a H...H distance. In the geometry similar to the experimental one, the stabilization is -5.1 kcal mol(-1,) with the BSSEcorrection, and correlation effects contibute significantly to the formation of the dimer.