Combination of sp2- and sp3-type phosphorus atoms for gold chemistry: preparation, structure, and catalytic activity of gold complexes that bear ligated 2-silyl-1,3-diphosphapropenes.

Kinetically protected 2-silyl-1,3-diphosphapropenes that bear both sp(2)- and sp(3)-type phosphorus atoms were employed in the preparation of gold complexes. The structural properties of the 1,3-diphosphapropene digold(I) complexes were characterized by spectroscopic and crystallographic analyses, which revealed unique aurophilic interactions and conformational properties of the ligand. The 2-silyl-1,3-diphosphapropene-bis(chlorogold) complexes catalyzed cycloisomerization reactions of 1,6-enyne derivatives even in the absence of silver co-catalyst, and were able to be recovered after the reaction. The catalytic activity of the digold complexes primarily depended on the sp(2)-type phosphorus atom and the silyl group, and could be tuned by the sp(3)-phosphino group. Additionally, results on the catalytic activity of the digold complex in the presence and absence of silver salts showed considerable differences.