Functionalised Tris(pyrazolyl)methane Ligands and Re(CO)3 Complexes Thereof

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AbstractThe synthesis of new tripodal nitrogen ligands derived from tris(pyrazolyl)methane (TpmR, R = H, tBu, Ph in 3‐position) is described. After deprotonation of the parent tris(pyrazolyl)methane TpmR, the carbanion reacts readily with ethylene oxide to yield the 3,3,3‐tris(3′‐substituted pyrazolyl)propanol ligands[(3‐Rpz)3CCH2CH2OH, R = H, tBu, Ph, 1a–c]. These ligands can be easily derivatised at the alcohol function. Microwave‐assisted reactions of these ligands and [Re(CO)5Br] yields the complex [(1a)Re(CO)3]Br (4) in the case of ligand 1a, whereas in the case of the substituted ligands 1b and 1c degradation was observed. The degradation products are identified as [(HpzR)2Re(CO)3Br] [R = tBu (7b), Ph (7c)]. These complexes were also prepared directly from [Re(CO)5Br] and the corresponding pyrazoles by microwave‐assisted synthesis. The Re(CO)3 complexes 4 and [(1a)Re(CO)3]OTf (5) are water‐soluble. The structures of 5·H2O and [{(pz)3CCH2CH3}Re(CO)3]OTf·1.5H2O·1/2CH3CN (6·1.5H2O·1/2CH3CN) as well as the structure of 7b have been elucidated by X‐ray crystallography.