Alkoxide triggered ligand substitution. Highly stereoselective formation

2131. Treatment of (L)Mo(CO), (L = v2-pyridyl dimethylphosphinite) at 0 'C in diethyl ether with 1.1 equiv of lithium alkoxides (ROLi) derived from unsaturated alcohols affords (v3-PMe20R)Mo(CO), chelates. The reaction involves nucleophilic attack at the phosphorus with cleavage of the chelate bridge and subsequent rapid extrusion of the alkoxide of 2-hydroxypyridine. The procedure is illustrated by using a number of allylic, homoallylic, l o , 2', and 3' alkoxides. When the alkoxides contain asymmetric centers, disastereofacial coordination selectivities of 3 - 30: 1 are observed. A molecular structure determination of (q3-PMe20R)Mo(CO), (10; R = 1-phenylallyl) was effected. Crystals of (PMe20CPhCH=CH2)Mo(C0), belong to the centrosymmetric triclinic space group Pi with cell parameters a = 7.416 (1) A, b = 8.649 (1) A, c = 13.572 (2) A, a = 98.48 (l)', 0 = 94.08 (l)', y = 97.29 (l)', and Z = 2. Diffraction data (Mo Ka, 26' = 4.5-45.0') were collected with a Syntex P21 automated diffractometer and the structure refined to RF = 2.3% for all 2223 reflections (RF = 1.8% for those 1984 data with IF,I > 6alF,I. The complex has a central Mo(0) atom that is octahedrally coordinated to four carbonyl ligands and with the other two (mutually cis) sites being taken up by the phosphorus atom and the terminal olefin function of the chelating PMe20CHPhCH=CH2 ligand; the Mo-P distance is 2.446 (1) A, Mo-C (olefin) distances are Mo-C(l)

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