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

The tetraphosphine 6(A),6(B),6(D),6(E)-tetradeoxy-6(A),6(B),6(D),6(E)-tetra(diphenylphosphinyl)-2(A),2(B),2(C),2(D),2(E),2(F),3(A),3(B),3(C),3(D),3(E),3(F),6(C),6(F)-tetradeca-O-methyl-alpha-cyclodextrin (alpha-TEPHOS) has been prepared in high yield by reacting 6(A),6(B),6(D),6(E)-tetra-O-methylsulfonyl-2(A),2(B),2(C),2(D), 2(E),2(F),3(A),3(B),3(C),3(D),3(E),3(F),6(C),6(F)-tetradeca-O-methyl-alpha-cyclodextrin with excess PPh(2)Li. The product was purified in its BH(3)-protected form. alpha-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)], alpha-TEPHOS led to the corresponding tetragold complex (alpha-TEPHOS)(AuCl)(4)] in which the four gold atoms are all located close to the primary face of the cyclodextrin. Reaction with PdCl(o-C(6)H(4)CH(2)NMe(2))](2) gave the C(2)-symmetrical complex (alpha-TEPHOS){PdCl(o-C(6)H(4)CH(2)NMe(2))}(4)]. Treatment of the ligand with two equiv. of Rh(norbornadiene)(tetrahydrofuran)(2)]BF(4) afforded selectively the bimetallic complex (alpha-TEPHOS){Rh(norbornadiene)}(2)](BF(4))(2) in which each metal centre is coordinated to two phosphorus atoms belonging to adjacent glucose units.