AQUEOUS ORGANOMETALLIC CHEMISTRY .2. H-1-NMR SPECTROSCOPIC, SYNTHETIC, AND STRUCTURAL STUDY OF THE CHEMOSELECTIVE AND DIASTEREOSELECTIVE REACTIONS OF [CP-ASTERISK-RH-(H2O)(3)](2+) WITH NITROGEN LIGANDS AS A FUNCTION OF PH

The reactions of a new CpRh aqua synthon, [Cp*Rh(H2O)(3)](2+) (1), at acidic pH values (2-6) with aniline (2), pyridine (3), and L-phenylal anine (4) have provided interesting chemo- and diastereoselectivities as studied by: H-1 NMR, FAB/MS, and single-crystal X-ray crystallograp hy. The reaction of 2 and aqua complex 1, at pH values from 4 to 6, qu antitatively provided [CpRh(eta(6)-aniline)](2+) (5); the structure o f 5 was unequivocally determined by a;single-crystal X-ray analysis, w hich also showed an approximate 25% eta(5) component. Compound 3 react ed with 1, at pH 2-6, to selectively provide [CpRh(eta(1)-pyridine)(n )(H2O)(3-n)](2+) (n = 1-3) complexes 6a-c as a function of pH. Surpris ingly, complex 1 reacted with 4, from pH 4 to 6, to provide only one d iastereomer of the known cyclic trimer )(mu-eta(1)-(OCO):eta(2)-(N,OCO )-L-phenylalanine)] (3+)(3) (7; S-C,S-C,S-C,S-Rb,S-Rh,S-Rh), an exampl e of a one-step, highly diastereoselective reaction in H2O.