Abstract
The bridge‐opening reaction of [(η^4^‐C~8~H~12~)~2~Rh~2~(μ‐Cl)~2~] with chiral and achiral β‐amino alcohol nucleophiles gave mononuclear complexes [(η^4^‐C~8~H~12~)RhCl{HN(R)∩OH‐κ__N__}] containing the amino alcohol ligands in N‐monodentate coordination; HN(R)∩OH = ethanolamine (4), 2‐amino‐2‐methyl‐1‐propanol (5), and either enantiomer of (R)‐, (S)‐2‐amino‐3‐methyl‐1‐butanol (D‐, L‐valinol) [(R)‐6, (S)‐6], (R)‐, (S)‐2‐pyrrolidinemethanol (D‐, L‐prolinol) [(R)‐7, (S)‐7], (1__S__,2__R__)‐, (1__R__,2__S__)‐2‐amino‐1‐phenyl‐1‐propanol (D‐, L‐norephedrine) [(1__S__,2__R__)‐8, (1__R__,2__S__)‐8], and (1__S__,2__R__)‐, (1__R__,2__S__)‐cis‐1‐amino‐2‐indanol [(1__S__,2__R__)‐9, (1__R__,2__S__)‐9]. Coordination of the free hydroxy function of the N,O ligands was brought about by both dehydrochlorination, which furnished the neutral valinolato chelate complex [(η^4^‐C~8~H~12~)Rh{(S)‐H~2~NCH(CHMe~2~)CH~2~O‐κ__N__,κ__O__}], (S)‐10, and by precipitation of the metal‐bound chloride with TlO~3~SCF~3~ to produce ionic chelate complexes [(η^4^‐C~8~H~12~)Rh{HN(R)∩OH‐κ__N__,κ__O__}]O~3~SCF~3~; HN(R)∩OH = 2‐amino‐2‐methyl‐1‐propanol (11), (S)‐2‐amino‐3‐methyl‐1‐butanol [(S)‐12], (S)‐2‐pyrrolidinemethanol [(S)‐13], (1__R__,2__S__)‐2‐amino‐1‐phenyl‐1‐propanol [(1__R__,2__S__)‐14], and (1__R__,2__S__)‐cis‐1‐amino‐2‐indanol [(1__R__,2__S__)‐15]. Except for only two in situ characterized [{(R)‐binap}Rh(H~2~N∩OH‐κ__N__,κ__O__)]^+^ cations, where H~2~N∩OH = L‐valinol or L‐norephedrine, no compound containing the various N,O ligands in addition to mono‐ or bidentate phosphanes could be prepared. In contrast, theP~2~/N~2~‐coordinated chelate complexes [{(R)‐binap}Rh(H~2~N∩NH~2~)]BF~4~ with H~2~N∩NH~2~ = H~2~NCMe~2~CMe~2~NH~2~ [(R)‐(16)], (R,R)‐H~2~NCH(Ph)CH(Ph)NH~2~ [(R),(R,R)‐17], and (R,R)‐1,2‐(H~2~N)~2~C~6~H~10~ [(R),(R,R)‐18] were easily obtained from [(η^4^‐C~8~H~12~)Rh{(R)‐binap}]BF~4~ and 1,2‐diamines. Oxidative addition of HCl to (R),(R,R)‐17 produced trans‐[{(R)‐binap}Rh(H)(Cl){(R,R)‐H~2~NCH(Ph)CH(Ph)NH~2~}]BF~4~ [(R),(R,R)‐19]. If activated by strong base (KOH), (R),(R,R)‐17 and (R),(R,R)‐19 acted as moderately active and enantioselective catalysts for the reduction of acetophenone by both direct and transfer hydrogenation: ee~max~: 71 % (S). The crystal structures of 4, (S)‐6, (R)‐7, (1__R__,2__S__)‐8, (S)‐10, (1__R__,2__S__)‐14, (1__R__,2__S__)‐15, (R)‐16, (R),(R,R)‐17, and two alcohol/alcoholato addition compounds, [(η^4^‐C~8~H~12~)Rh(H~2~NCMe~2~CH~2~O‐κ__N__,κ__O__)][(η^4^‐C~8~H~12~)Rh(H~2~NCMe~2~CH~2~OH‐κ__N__,κ__O__)][(η^4^‐C~8~H~12~)RhCl~2~] [1·2], and [(η^4^‐C~8~H~12~)Rh(H~2~NCMe~2~CH~2~O‐κ__N__,κ__O__)][(η^4^‐C~8~H~12~)Rh(H~2~NCMe~2~CH~2~OH‐κ__N__,κ__O__)]Cl [1·3], were determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)