2, 2-Dimethyl-and 2-benzyl-2-methyl-1-(2, 4, 6-tri-tert-butylphenyl)-1-phosphaethenes were employed as ligand of mononuclear chlorogold (I) complexes, which catalyzed cycloisomerization of 1, 6-enyne affording vinylcyclopentene exclusively in the absence of silver co-catalyst. The reaction mechanisms are discussed based on DFT calculations. In addition to the cycloisomerization, the phosphaalkene–chlorogold (I) complexes catalyzed ...