CO reduction by calcium and ytterbium hydride complexes with a bulky monodentate carbazolyl ligand

Abstract

The bulky monodentate carbazolyl ligand 1,8-bis(3,5-ditertbutylphenyl)-3,6-ditertbutylcarbazole (^dtbpCbz) was employed in the synthesis of monomeric heteroleptic amido carbazolyl complexes of Ca and Yb. For both central metal atoms, dimeric hydride complexes [(^dtbpCbz)Ca(benzene)H]₂, [(^dtbpCbz)Ca(THF)H]₂, [(^dtbpCbz)Yb(benzene)H]₂ and [(^dtbpCbz)Yb(THF)H]₂ were obtained, which show remarkably poor solubility in organic solvents. The characteristic hydride ¹H NMR resonance of [(^dtbpCbz)Ca(benzene)H]₂ was observed at 2.07 ppm, and for the first time, characteristic vibrational modes of the Ca₂H₂ and Yb₂H₂ moiety are discussed. Despite their poor solubility, the hydride complexes could be reacted with CO to yield the corresponding ethenediolate complexes.