The reaction of the alkyl complexes Cp*2LnCH(SiMe 3)2 (Ln = Y 1-Y, Ce 1-Ce, La 1-La; Cp* = η5-C5Me5) and Me2Si(η 5-C5Me4)2LnCH(SiMe3) 2 (Ln = Ce 5-Ce) with 1-methylalk-2-ynes CH3C≡CR (R = Me 3a, Et 3b, nPr 3c, tBu 3d, SiMe3 3e, Ph 3f, C6H4Me-2 3g, C6H3Me 2-2,6 3h, C6H3iPr2-2,6 3i, C6F5 3j) affords the …