Heteroleptic calcium amides effect the catalytic dimerisation of the terminal alkyne CH(3)OCH(2)C[triple bond, length as m-dash]CH to the hexatriene (CH(3)OCH(2))CH[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]CH(CH(2)OCH(3)) under mild conditions; the reaction is proposed to occur via a dimeric calcium acetylide intermediate and to be promoted by polarisation of the electron density within the alkynide C[triple bond, length as m-dash]C bonds.