Formation and Structure of Gas-Phase Lanthanide(III) Cyanobenzyne Complex (η²-4-CNC₆H₃)LnCl₂^–, Obtained via Both the Single- and Dual-Ligand Strategies

Abstract

The lanthanide(III) cyanobenzyne complexes (η 2 -4-CNC 6 H 3 )-LnCl 2 − (Ln = La−Lu except Eu; Pm was not examined) were generated in the gas phase using an electrospray ionization mass spectrometry coupled with collisioninduced dissociation (CID) technique. For all lanthanides except Sm, Eu, and Yb, (4-CNC 6 H 3 )LnCl 2 − can be generated either via a single-ligand strategy through consecutive CO 2 and HCl losses of ( 4-CNC 6 H 4 CO 2 )LnCl 3 − or via a dual-ligand strategy through successive CO 2 /C 6 H 5 CN or 4-CNC 6 H 4 CO 2 H and CO 2 losses of (4-CNC 6 H 4 CO 2 ) 2 LnCl 2 − . For Sm and Yb, although only reduction products LnCl 3 − were formed upon CID of (4-CNC 6 H 4 CO 2 )LnCl 3 − , (4-CNC 6 H 3 )LnCl 2 − were obtained via the dual-ligand strategy without the appearances of other products. CID of (4-CNC 6 H 4 CO 2 )EuCl 3 − and (4-CNC 6 H 4 CO 2 ) 2 EuCl 2 − gave EuCl 3− and the cyanophenyl complex (4-CNC 6 H 4 )EuCl 2 − , respectively, in both of which the +III oxidation state of Eu was reduced to +II. Density functional theory (DFT) calculations reveal that (4-CNC 6 H 3 )LnCl 2 − are formally described as Ln(III) cyanobenzyne complexes, (η 2 -4-CNC 6 H 3 )LnCl 2 − , with the dianionic cyanobenzyne ligand (4-CNC 6 H 3 2− ) coordinating to the Ln(III) centers through two Ln−C σ bonds, which is in accordance with their reactivities toward water. Benzyne and substituted benzyne complexes (XC 6 H 3 )LuCl 2 − (X = H, 3-CN, 4-F, 4-Cl, and 4-CH 3 ) were also synthesized in the gas phase via the single-and dual-ligand strategies.