Alkynyl Compounds of the Rare‐earth Metals

Conversion of the rare‐earth tetramethylaluminates [ Ln (AlMe 4 ) 3 ] with phenylacetylene afforded the homoleptic alkynylaluminates [ Ln {(μ‐C≡CPh) 2 AlMe 2 } 3 ] [ Ln = Ce ( 1 ), Er( 2 )]. The reaction of five equivalents of phenylacetylene with the yttrium aluminate [Y(AlMe 4 ) 3 ] afforded [Y{(μ‐C≡CPh)AlMe 3 }{(μ‐C≡CPh) 2 AlMe 2 } 2 ] ( 3 ). The cationic yttrium complex [(TMTAC) 2 YMe 2 ][AlMe 4 ] ( 4 ) (TMTAC = 1, 3,5‐trimethyl‐1, 3,5triazacyclohexane) was reacted with phenylacetylene to give the product [(TMTAC) 2 Y(C≡CPh) 2 ][Me 2 Al(C≡CPh) 2 ] ( 5 ), in which two methyl groups of each, the cation and the anion, were substituted by phenylacetylide groups. Under the same conditions as for the synthesis of compound 5 , the holmium analogue reveals different reactivity in forming a neutral alkynyl complex [(TMTAC) 2 Ho(C≡CPh) 3 ] ( 6 ). The introduction of 1, 8‐diethynylanthracene to 4 leads to a structural very similar complex [(TMTAC) 2 Ho(μ‐1, 8‐diethynylanthracene) 3 ] ( 7 ) and offers the same reactivity as observed for the synthesis of 6 . All compounds were characterized by X‐ray diffraction experiments. Compounds 1 – 3 and 5 were also characterized by NMR and elemental analyses.