Synthesis and X-ray structures of manganese(I) and rhenium(I) formato complexes, fac-(CO)3(dppp)MOC(H)O

The mononuclear manganese(I) and rhenium(I) formato complexes, fac-(CO)3(dppp)MOC(H)O (M=Mn, 1; M=Re, 2), have been prepared from fac-(CO)3(dppp)MH and formic acid, and their X-ray structures determined. Compounds 1 and 2 are unusual in that the formato ligands are bound in a terminal, monodentate fashion. For Mn, only multinuclear complexes containing bridging formato ligands have been characterized previously by X-ray diffraction. The MO bond lengths and MOC bond angles are 2.043(2) Å and 124.2(2)°, respectively for 1 and 2.167(3) Å and 122.3(3)°, respectively for 2. Compounds 1 and 2 can also be decarboxylated at elevated temperatures with quantitative recovery of fac-(CO)3(dppp)MH.