New Coordinatively Unsaturated Lutetium Mono‐ and Bis(alkyl) Complexes with a Bis(ortho)‐Chelating Aryldiamine Ligand—Crystal Structures of [LuCl2{2,6‐(Me2NCH2)2C6H3}(μ‐Cl)(μ‐Li(thf)2)]2 and [Lu(μ‐Cl){2,6‐(Me2NCH2)2C6H3}(CH2SiMe3)]2

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AbstractNew complexes of lutetium and yttrium containing the monoanionic, terdentate ligand [2,6‐(Me2NCH2)2C6H3]− (NCN) have been synthesized by substitution reactions starting from MCl3 (M = Lu, Y). Reaction of MCl3 (M = Y, Lu) with one equivalent of (NCN)Li affords the ate complexes [(NCN)MCl2(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 P21/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 Me3SiCH leads to decomposition. However, reaction of 1a with Me3SiCH2Li gives the monoalkyl complex [(NCN)Lu‐(μ‐Cl)(CH2SiMe3)]2 2, 30% yield), in which the terdentate ligand is bound in a pseudo‐facial manner. Crystals of 2 are triclinic (space group P1, 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 R1 = 0.11 for 1361 reflections [I 2σ(I)]). Substitution of the chloride ions in 2 by Me3SiCH is possible and affords quantitatively the bisalkyl complex [(NCN)Lu(CH2SiMe3)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.