Isolation of fac-[Re(CO)3(HMPA)3][BF4]. Structural characterization of a key cationic intermediate in the exchange reaction between [Re(CO)6][BF4] and acetylferrocene. Implications in radiopharmaceutical chemistry

[Re(CO)6][BF4] reacts with HMPA to form [Re(CO)3(HMPA)3][BF4] (4), whose structure was determined by X-ray crystallography and proves to be a key intermediate in the ligand exchange reaction between three CO and Cp; and may be related to other cations such as [Re(CO)3(H2O)3]+, [Re(CO)3(CH3CN)3]+, [Re(CO)3(DMSO)3]+, obtained by different ways, and important in the field of organometallic radiopharmaceuticals.