d(3)-d(3) Diolates of dimolybdenum and ditungsten Part 4. Molybdenum derivatives of S(-)-1,1-diphenyl-1,2-propanediol, S(-)-1,1,2-triphenyl-1,2-ethanediol and (1R, 2R)-(-)-1,2-dicyclohexyl-1,2-ethanediol

From the reactions between the diols S(-)-1,1-diphenyl-1,2-propanediol, S(- )-1,1,2-triphenyl-1,2-ethanediol and (1R, 2R)-(-)-1,2dicyclohexyldiol and e ach of Mo-2((OBu)-Bu-t)(6) and Mo-2(NMe2)(6), the compounds Mo-2(O2C15H15), (1), Mo-2(O2C20H17)(3) (2) and Mo-2(O2C14H25)(4) (3) have been isolated an d characterized. In the reactions leading to the formation of 1 and 2, kine tic control leads to highly sterically congested products having six phenyl groups at one end of the Mo-Mo axis. Three methyl groups in compound 1 and three phenyl groups in compound 2 are at the other Mo centers. In compound 3, four equivalents of the diol are taken up by the Mo-2(6+) center, two s traddle the Mo-Mo triple bond and one chelates at each Mo center. Inspectio n of the Mo-O and O ... O distances in compound 3 reveals the presence of O H groups such that the compound may be considered an alcoholate Mo-2(O simi lar to similar to O)(2)(O similar to similar to OH)(2). These results are d iscussed in terms of crystals engineering an infinite chain of Mo2 units wi th parallel Mo-Mo axes wherein a chiral ligand framework imposes a C-3 scre w axis. (C) 2000 Elsevier Science Ltd All rights reserved.