6533b823fe1ef96bd127ebdd

RESEARCH PRODUCT

Synthesis and coordinating ability of an anionic cobaltabisdicarbollide ligand geometrically analogous to BINAP.

subject

description

The anionic chelating ligand [1,1'-(PPh 2 ) 2 -3,3'-Co(1,2-C 2 B 9 H 1 0 ) 2 ] - has been synthesized from [3,3'-Co(1,2-C 2 B 4 H 1 1 ) 2 ] - in very good yield in a one-pot process with an easy work-up procedure. The coordinating ability of this ligand has been studied with Group 11 metal ions (Ag, Au) and with transition-metal ions (Pd, Rh). The two dicarbollide halves of the [1,1'-(PPh 2 ) 2 -3,3'-Co(1,2-C 2 B 9 H 1 0 ) 2 ] - ligand can swing about one axis in a manner analogous to the constituent parts of BINAP and ferrocenyl phosphine derivatives. All these ligands function as hinges, with the most important property in relation to the coordination requirements of the metal being the P...P distance. [1,1'-(PPh 2 ) 2 -3,3'-Co(1,2-C 2 B 9 H 1 0 ) 2 ] - , BINAP, ferrocenyl phosphine derivatives, and other hinge ligands present a range of different P...P separations, and consequently different coordination spheres and dispositions around metal cations. To account for these differences, the equation D q 2 = D 0 2 + 4R 2 cos 2 (90-q/2) has been developed. It relates the P...P distance (D q ) in a complex with the minimum P...P distance (D 0 ) that is characteristic of the hinge-type ligand.