MULTIDIMENSIONAL AG-109, P-31, AND H-1 HMQC AND HSQC NMR-STUDIES ON A MODEL HOMOGENEOUS CATALYST - REACTIONS OF A CHIRAL FERROCENYLPHOSPHINE WITH AG(CF3SO3)

The chiral ferrocene ligand Fe{1-(PPh(2))-2-((R)-CH(Me)N(Me)CH(2)CH(2)NMe(2))- C5H3}{C(5)H(4)PPh(2)}, 1, reacts with Ag(CF3SO3) to form a trinuclear complex Ag-3(1)(2)(CF3SO3)(3), 3, in which there are two different silver coordination spheres. In one environment two silver cations complex-to the 1-PPh(2) P atom and the two N atoms of the side chain, from two ligands 1, whereas the third silver cation coordinates to two P atoms from two C(5)H(4)PPh(2) moieties. Reaction of 3 with a 70-fold excess of the isonitrile CNCH(2)CO(2)Me, 4, affords a mononuclear complex, 5, in which both P atoms of 1 chelate to silver(I). The number of coordinated P-31 spins for 3 and 5 and the coordination of the chiral side chain in 3 were determined using HSQC and HMQC Ag-109-P-31, Ag-109-H-1, and P-31-H-1 multidimensional methods. The relevance of these observations to the Au(I)-catalyzed aldol condensation of aldehydes with isonitriles is discussed.