Synthesis, Structure, and Bonding of d0/fn Metallacarboranes Incorporating the η7-Carboranyl Ligand

Treatment of 1,2-(C 6 H 5 CH 2 ) 2 -1,2-C 2 B 10 H 10 with excess Na or Li metal in THF followed by reaction with MCl 3 in the presence of excess alkali metal gave novel 13-vertex closo- metallacarboranes {[(C 6 H 5 CH 2 ) 2 C 2 B 10 H 10 ]M(THF)} 2 {Na(THF) 3 } 2 ·2THF (M = Dy ( 1 ), Y ( 2 ), Er ( 3 )) or [{(C 6 H 5 CH 2 ) 2 C 2 B 10 H 10 }M(THF)] 2 [Li(THF) 4 ] 2 (M = Y ( 5 ), Er ( 6 )) in moderate to good yield, respectively. Recrystallization of 3 from a DME solution afforded DME-coordinated metallacarborane {[(C 6 H 5 CH 2 ) 2 C 2 B 10 H 10 ]Er(DME)} 2 {Na(DME) 2 } 2 ( 4 ). 2 and 5 are the first examples of d 0 metallacarboranes incorporating a η 7 -carboranyl ligand. All of these complexes have been fully characterized by various spectroscopic date, elemental analyses, and X-ray diffraction studies. Molecular orbital calculations indicate that the metal−carborane bonding is well delocalized and can be described as the orbital interactions between the metal's five d orbitals and the cage's five symmetry-adapted frontier orbitals. It is anticipated that only the d 0 /f n transition metal ion with the proper size is capable of being η 7 -bound to an arachno -carboranyl ligand.