Homologues of the easily ionized compound Mo2(hpp)4 containing smaller bicyclic guanidinates.
Two bicyclic guanidinate ligands consisting of 5,5-membered (tbo) and 5,6-membered (tbn) rings have been used for the preparation of dimolybdenum compounds, such as Mo2(tbo)4 and Mo2(tbo)4Cl, and species containing Mo2(tbn)4(n+) with n = 0-2. The compounds with quadruply bonded Mo2(4+) species are strong reducing agents and have potentials of about -1 V (vs Ag/AgCl) for the Mo2(5+/4+) process. The structure of the THF solvate of Mo2(tbo)4 shows the longest Mo-Mo bond distance, 2.1453(4) A, for a quadruply bonded species, and this is due to a large divergent angle induced by the geometry of the ligand. This distance increases to 2.2305(8) A upon oxidation by CH2Cl2 to Mo2(tbo)4Cl. For the 5,6-membered-ring ligand tbn, even though the divergent angle is large compared to formamidinate ligands, it is not as large as that in tbo, and the Mo-Mo distance in Mo2(tbn)4, 2.082(1) A, is in the normal range for paddlewheel Mo2(4+) compounds. This distance increases to 2.2233(8) A upon oxidation by O2 in CH2Cl2, which forms Mo2(tbn)4Cl2 x CH2Cl2.
Cotton
F Albert
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Department of Chemistry and Laboratory of Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012, USA. cotton@tamu.edu
Murillo
Carlos A
CA
Wang
Xiaoping
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Wilkinson
Chad C
CC