An Alumanylyttrium Complex with an Absorption due to a Transition from the Al−Y Bond to an Unoccupied d‐Orbital

The reaction between a dialkyl‐substituted alumanyl anion and [Y(CH 2 SiMe 3 ) 2 (thf) 3 ][BPh 4 ] resulted in the formation of (dialkylalumanyl)yttrium complex  2 , which exhibits the first 2‐center–2‐electron (2 c‐2 e) Al−Y bond. The 1 H and 13 C NMR spectra of 2 together with an X‐ray crystallographic analysis indicated a C 2 v symmetrical structure. DFT calculations on 2 revealed that its LUMO consists of overlapping 3 p‐ and 4 d‐orbitals of the Al and Y atoms, respectively, and that the HOMO–LUMO gap is narrow. The UV/Vis spectrum of 2 exhibited a visible absorption at 432 nm, which suggests that the strong σ‐donating and π‐accepting character of the three‐coordinate dialkylalumanyl ligand generates a colored d 0 ‐complex that does not contain any π‐electrons.