Formation and Structure of Gas-Phase Lanthanide(III) Cyanobenzyne Complex (η 2 -4-CNC 6 H 3 )LnCl 2 - , Obtained via Both the Single- and Dual-Ligand Strategies.

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 collision-induced 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.