α-TEPHOS: a cyclodextrin-derived tetraphosphine for multiple metal binding

TLDR: The tetraphosphine 6A,6B,6D,6E-tetradeoxy (α-TEPHOS) as discussed by the authors is the first optically active tetramerine in which the four phosphine units are tethered to a cavity-shaped scaffold.

Abstract: The tetraphosphine 6A,6B,6D,6E-tetradeoxy-6A,6B,6D,6E-tetra(diphenylphosphinyl)-2A,2B,2C,2D,2E,2F,3A,3B,3C,3D,3E,3F,6C,6F-tetradeca-O-methyl-α-cyclodextrin (α-TEPHOS) has been prepared in high yield by reacting 6A,6B,6D,6E-tetra-O-methylsulfonyl-2A,2B,2C,2D, 2E,2F,3A,3B,3C,3D,3E,3F,6C,6F-tetradeca-O-methyl-α-cyclodextrin with excess PPh2Li. The product was purified in its BH3-protected form. α-TEPHOS is the first optically active tetraphosphine in which the four phosphine units are tethered to a cavity-shaped scaffold. When reacted with [AuCl(tetrahydrothiophene)], α-TEPHOS led to the corresponding tetragold complex [(α-TEPHOS)(AuCl)4] in which the four gold atoms are all located close to the primary face of the cyclodextrin. Reaction with [PdCl(o-C6H4CH2NMe2)]2 gave the C2-symmetrical complex [(α-TEPHOS){PdCl(o-C6H4CH2NMe2)}4]. Treatment of the ligand with two equiv. of [Rh(norbornadiene)(tetrahydrofuran)2]BF4 afforded selectively the bimetallic complex [(α-TEPHOS){Rh(norbornadiene)}2](BF4)2 in which each metal centre is coordinated to two phosphorus atoms belonging to adjacent glucose units.