Reactivity of Tp Me2 ‐Supported Yttrium Alkyl Complexes toward Aromatic N‐Heterocycles: Ring‐Opening or CC Bond Formation Directed by CH Activation

Unusual chemical transformations such as three‐component combination and ring‐opening of N‐heterocycles or formation of a carbon–carbon double bond through multiple C–H activation were observed in the reactions of Tp Me2 ‐supported yttrium alkyl complexes with aromatic N‐heterocycles. The scorpionate‐anchored yttrium dialkyl complex [Tp Me2 Y(CH 2 Ph) 2 (THF)] reacted with 1‐methylimidazole in 1:2 molar ratio to give a rare hexanuclear 24‐membered rare‐earth metallomacrocyclic compound [Tp Me2 Y( μ ‐ N , C ‐Im)(η 2 ‐ N , C ‐Im)] 6 ( 1 ; Im=1‐methylimidazolyl) through two kinds of C–H activations at the C2‐ and C5‐positions of the imidazole ring. However, [Tp Me2 Y(CH 2 Ph) 2 (THF)] reacted with two equivalents of 1‐methylbenzimidazole to afford a C–C coupling/ring‐opening/C–C coupling product [Tp Me2 Y{η 3 ‐( N , N , N )‐N(CH 3 )C 6 H 4 NHCHC(Ph)CN(CH 3 )C 6 H 4 NH}] ( 2 ). Further investigations indicated that [Tp Me2 Y(CH 2 Ph) 2 (THF)] reacted with benzothiazole in 1:1 or 1:2 molar ratio to produce a C–C coupling/ring‐opening product {(Tp Me2 )Y[μ‐η 2 :η 1 ‐SC 6 H 4 N(CHCHPh)](THF)} 2 ( 3 ). Moreover, the mixed Tp Me2 /Cp yttrium monoalkyl complex [(Tp Me2 )CpYCH 2 Ph(THF)] reacted with two equivalents of 1‐methylimidazole in THF at room temperature to afford a trinuclear yttrium complex [Tp Me2 CpY(μ‐ N , C ‐Im)] 3 ( 5 ), whereas when the above reaction was carried out at 55 °C for two days, two structurally characterized metal complexes [Tp Me2 Y( Im ‐Tp Me2 )] ( 7 ; Im ‐Tp Me2 =1‐methyl‐imidazolyl‐Tp Me2 ) and [Cp 3 Y(HIm)] ( 8 ; HIm=1‐methylimidazole) were obtained in 26 and 17 % isolated yields, respectively, accompanied by some unidentified materials. The formation of 7 reveals an uncommon example of construction of a CC bond through multiple C–H activations.