New Coordinatively Unsaturated Lutetium Mono‐ and Bis(alkyl) Complexes with a Bis( ortho )‐Chelating Aryldiamine Ligand—Crystal Structures of [LuCl 2 {2,6‐(Me 2 NCH 2 ) 2 C 6 H 3 }(μ‐Cl)(μ‐Li(thf) 2 )] 2 and [Lu(μ‐Cl){2,6‐(Me 2 NCH 2 ) 2 C 6 H 3 }(CH 2 SiMe 3 )] 2

New complexes of lutetium and yttrium containing the monoanionic, terdentate ligand [2,6‐(Me 2 NCH 2 ) 2 C 6 H 3 ] − (NCN) have been synthesized by substitution reactions starting from MCl 3 (M = Lu, Y). Reaction of MCl 3 (M = Y, Lu) with one equivalent of (NCN)Li affords the ate complexes [(NCN)MCl 2 (μ‐Cl)(μ‐Li(thf) 2 )] 2 ) (M = Lu ( 1a ), Y ( 1b )) in which the terdentate ligand is bound in mer fashion and all three chloride atoms are retained in the product. Crystals of 1a are monoclinic (space group P2 1 / n , a =10.4559(4), b = 21.6150(9), c =12.1700(7) Å, β = 105.294(4)°, Z = 2, final R = 0.039 for 3695 observed reflections [ I >2.50σ( I )]). Attempted substitution of chloride in the yttrium complex 1b by Me 3 SiCH   2 −leads to decomposition. However, reaction of 1a with Me 3 SiCH 2 Li gives the monoalkyl complex [(NCN)Lu‐(μ‐Cl)(CH 2 SiMe 3 )] 2 2 , 30% yield), in which the terdentate ligand is bound in a pseudo‐facial manner. Crystals of 2 are triclinic (space group P 1, a = 9.8575(7), b = 10.0171(7), c = 11.1460(14) Å, α = 75.096(8). β = 78.092(8), γ =77.474(6)°, Z = 1, final R 1 = 0.11 for 1361 reflections [ I 2σ( I )]). Substitution of the chloride ions in 2 by Me 3 SiCH   2 −is possible and affords quantitatively the bisalkyl complex [(NCN)Lu(CH 2 SiMe 3 ) 2 ] ( 3 ). The lutetium complexes 2 and 3 are formally coordinatively unsaturated complexes, which are moisture‐sensitive and thermally stable for several weeks when dissolved in aromatic solvents. However, they decompose rapidly in aliphatic solvents such as hexane, and a decomposition route involving the formation of carbene species is proposed.