Rare‐Earth Complexes Coordinated by ansa‐Bis(amidinate) Ligands with m‐Phenylene, 2,6‐Pyridinediyl, and SiMe2 Linkers

The salt‐metathesis reactions of anhydrous LnCl3 (Ln = Y, Er) with [1,3‐C6H4{NC(Ph)NSiMe3}2Li2(thf)2]2 (1; thf = tetrahydrofuran) in a 2:1 molar ratio in thf afford tris(amidinate) complexes [(1,3‐C6H4{NC(Ph)NSiMe3}2)3Y(thf)Y(µ‐Cl)Li(thf)3] (3) and [(1,3‐C6H4{NC(Ph)NSiMe3}2)3Er2(µ‐Cl)Li(thf)3] (4), which feature bridging coordination of the amidinate ligands to two Ln3+ ions. The reactions of the dilithium derivative of the related bis(amidine) with a 2,6‐pyridinediyl linker, [2,6‐C5H3N{NC(tBu)N(2,6‐Me2C6H3)}2]2–, with LnCl3 (Ln = Y, Er) result in the formation of mononuclear chlorido bis(ligand) ate complexes [{(2,6‐C5H3N)(NC{tBu}N{2,6‐Me2C6H3})2}({2,6‐C5H3N}{NC(tBu)N(2,6‐Me2C6H3)}{NC(tBu)NH(2,6‐Me2C6H3)})LnCl][Li(dme)3] [Ln = Y (5), Er (6); dme = 1,2‐dimethoxyethane]. The Ln3+ ions in these complexes are coordinated by one dianionic tridentate amidopyridinate–amidinate ligand, and the second ligand is a monoanionic amidopyridinate. The reaction of YbCl3 with [(Me2Si{NC(Ph)N(2,6‐iPr2C6H3)}2)2Li3][Li(thf)4], which contains a short SiMe2 linker, in a 2:1 molar ratio in thf afforded the bis(amidinate)chloridoytterbium complex [(Me2Si{NC(Ph)N(2,6‐iPr2C6H3)}2)2(Yb2Cl)(µ‐Cl)2Li(thf)3] (8). The magnetic properties of 4 were investigated through superconducting quantum interference device (SQUID) magnetometry. The coordination modes of linked bis(amidinate) ligands to Ln3+ (Ln = Y, Er) ions are affected dramatically by the length and nature of the linker: m‐phenylene and SiMe2 favor the formation of dinuclear complexes featuring “spanning” coordination, whereas the ligand with a 2,6‐C5H3N linker enables the synthesis of mononuclear species.