DIASTEREOSELECTIVE LIGAND AND VERTEX SUBSTITUTIONS IN BIMETALLIC BRIDGED ALKYNE CLUSTERS - X-RAY CRYSTAL-STRUCTURE OF (MU-2-ENDO-2-PROPYNYLBORNEOL)HEXACARBONYLDICOBALT

Enantiomerically pure dicobalt μ-alkyne clusters that possess diastereotopic Co(CO)3 vertices can be synthesized by the treatment of (propargyl alcohol)Co2(CO)6 with menthol or borneol or by the reaction of Co2(CO)8 with endo-2-propynylborneol. Ligand substitution reactions with phosphines occur with some degree of diastereoselectivity to give mixtures of monosubstituted complexes. Moreover, diastereoselective replacement of a metal vertex by isolobal groups, (C5H4R)M(CO)2, where M = Mo, W, has been observed. The hexacarbonyldicobalt complex, 6, of endo-2-propynylborneol has been synthesized and characterized by X-ray crystallography. The crystals are orthorhombic of space group P212121 with a = 12.136 (3) Å, b = 12.682 (2) Å, c = 13.652 (3) Å, V = 2101 (1) Å3, Dc = 1.51 g cm-3, and Dm = 1.49 g cm-3 for Z = 4 and R1 = 0.0546 and R2 = 0.0567 for 3713 unique reflections (R1 = 0.0437 and R2 = 0.0463 for 2953 reflections with I > 2.5σ(I)). © 1990, American Chemical Society. All rights reserved.