Mn(CO)2 Complexes of Cyclopentadienyl/Scorpionate Hybrid Ligands

Rare examples of complexes featuring a chelating cyclopentadienyl/scorpionate hybrid ligand are reported. The compounds are obtained by photolytic decarbonylation of K[(OC) 3 Mn(C 5 H 4 -B(pz)(R)R‘)] ( 1: R = R‘ = Me; 2: R = Me, R‘ = pz; 3: R = R‘ = pz; pz = pyrazol-1-yl), which leads to the constrained-geometry complexes K[(OC) 2 Mn(C 5 H 4 -B( μ -pz)(R)R‘)] ( 4 − 6 ) in quantitative yields. In 4 − 6, the Mn-coordinating pyrazolyl ring is tethered to the cyclopentadienyl ligand via a borate bridge. According to X-ray crystallography, the molecular frameworks of 4 − 6 are largely unstrained. The ligand scaffold is thus well adapted to the coordination requirements of the Mn(I) ion. The crystal lattices of 2, 3, and Li[(OC) 3 Mn(C 5 H 4 -BPh 3 )] ( 7 ) contain dimeric aggregates held together by K + -OC σ adducts, K + -pz σ adducts, and K + -pz π interactions ( 2, 3 ) as well as Li + -OC σ adducts and Li + -phenyl π interactions ( 7 ). In none of these cases does the π-electron cloud of the cymantrenyl substituent take part in alkali metal ion complexation.