Acetato-bis(pyrazole) complexes [Mo(η 3 -methallyl)(O 2 CMe)(CO) 2 (pz ∗ H) 2 ], (methallyl=CH 2 C(CH 3 )CH 2 ) and fac-[M(O 2 CMe)(CO) 3 (pz ∗ H) 2 ], (pz ∗ H=pyrazole or 3,5-dimethylpyrazole, dmpzH; M=Mn, Re) are obtained from [Mo(η 3 -methallyl)Cl(CO) 2 (NCMe) 2 ] or fac-[MBr(CO) 3 (NCMe) 2 ] [M=Mn (synthesized in situ), Re], 2equiv. of pyrazole, and 1equiv. of sodium acetate for Mo complexes, or silver acetate for Mn or Re complexes. The chlorido-complexes [Mo(η 3 -methallyl)Cl(CO) 2 L 2 ] (L=pzH, dmpzH), obtained from the same starting material by substitution of MeCN by pzH or dmpzH, are also described. The crystal structures of the fac-acetato-bis(dimethylpyrazole) complexes present the same pattern of intramolecular hydrogen bonds between the acetate and the dimetylpyrazole ligands, whereas the crystal structures of the fac-acetato-bis(pyrazole) complexes show different hydrogen bonds patterns, with intermolecular interactions. NMR data indicate that these interactions are not maintained in solution.