The tungsten benzylidyne complex [PhC≡W{OSi(OtBu)3}3] (1) efficiently catalyses the metathetic conversion between symmetrical and unsymmetrical 1,3-diynes, which provides the opportunity to prepare the latter species directly from terminal alkynes by a combination of copper-catalysed homocoupling and catalytic alkyne cross-metathesis (ACM).

The synthesis of two new unsymmetric dinucleating ligand systems, L1, combining a bidentate binding site with a tridentate binding site linked through a dibenzofuran spacer, and L2, with two tridentate binding sites bridged by an ethylene spacer, is reported. The ligands L1 and L2 were used for the preparation of the dicopper(I) complexes [Cu2(L1)(NCCH3)3](X)2, {[Cu2(L1)Cl2]}n and [Cu2(L2)(NCCH3)2](Y)2 (X = PF6, BF4, OTf; Y = ClO4, PF6, BF4), in which the two respective copper ions possess two different coordination environments. All complexes reacted with O2, but in the case of the L1 series, no primary O2 adduct could be identified by UV/Vis spectroscopy. Reaction of the [Cu2(L2)(NCCH3)2](Y)2 complexes with pure oxygen led to the formation of an O2 adduct that proved rather unstable.

Synthesis of Unsymmetrical 1,3-Diynes via Alkyne Cross-Metathesis. -(LI, S. T.; SCHNABEL, T.; LYSENKO, S.; BRANDHORST, K.; TAMM*, M.; Chem. Commun. (Cambridge) 49 (2013) 65, 7189-7191, http://dx.