DIOXOMOLYBDENUM(VI) COMPLEXES WITH NEW ENANTIOMERICALLY PURE AMINO DIOL LIGANDS

(R)-Phenylglycinol is shown to be an efficient building block for the synthesis of chiral amino diols in pure diastereomeric form by epoxide ring-opening reactions. The reaction with rac-trans-stilbene oxide gi ves [HOCH2(R)-PhCH]NH[(S)-PhCH-(R)-PhCHOH] [2(R)-3(R)-4(S)-HNO2H2] in 32% yield, which can be methylated at nitrogen to give enantiomericall y pure [HOCH2-(R)-PhCH]NCH3[(S)-PhCH-(R)-PhCHOH] [2(R)-3(R)-4(S-)MeNO( 2)H(2)]. These amino diol ligands have been used to prepare chiral dio xomolybdenyl complexes of the formula N(R)-2(R)-3(R)-4(s)-(HNO2)MoO2 ( 1) and N(R)-2(R)-3(R)-4(S)-(MeNO(2))MoO2 (2). The absolute configurati on at each stereocenter in the Mo(VI) complexes has been established b y H-1 NOESY spectroscopy. The configuration determined for 1 has been confirmed by an X-ray analysis. Crystal data: orthorhombic P2(1)2(1)2( 1), a = 7.620(3), b = 13.589(2), c = 20.339(3) Angstrom, Z = 4, R = 0. 0336. The structure consists of a polymeric chain of N(R)-2(R)3(R)-4(S )-(HNO2)MoO2 molecules connected through unsymmetrical Mo=O --> Mo bri dges. Each metal center is coordinated in a distorted octahedral geome try by a cis dioxo unit and by two trans alkoxo atoms. The coordinatio n polyhedron is completed by a nitrogen atom and by a bridging oxo oxy gen atom from an adjacent molecule. Compound 2 catalyzes the oxidation of PPh(3) to OPPh(3) by DMSO through a mechanism that involves the in termediacy of a Mo(IV) species.