Identification of Ge≡O Triple Bond in Ge₆O^– Cluster: Anion Photoelectron Spectroscopy and Theoretical Calculations

Unlike C -O, which is common in coordination chemistry and organometallic chemistry, little is known about Si -O or Ge-O compounds. Here we report a Ge6O- cluster featuring a Ge-O triple bond. The structural and chemical bonding properties of Ge6O-/0 are investigated using anion photoelectron spectroscopy and theoretical calculations. Two nearly degenerate isomers have been found for Ge6O-. The lowest-energy structure (6A) can be viewed as an O atom bonding with a tetragonal bipyramidal Ge6. The second one (6B) can be considered as an O atom interacting with a capped trigonal bipyramidal Ge6. Chemical bonding analyses reveal that Ge6O- (6A) can be viewed as a Ge-O unit interacting with a sigma antiaromatic C2v symmetric tetragonal pyramidal Ge53- moiety. Comparisons of the chemical bonding in Ge6O- (6A) with that in Ge5CO- and Ge5MnO- indicate the similar behavior of Ge-O to C -O and Mn-O in its bonding to the Ge53- and Ge54- moieties.