92763-67-2Relevant articles and documents
Correlation of Mo - Mo quadruple bond length with angle of internal rotation, using data for 10 compounds
Campbell III, Fred L.,Cotton, F. Albert,Powell, Gregory L.
, p. 4222 - 4226 (2008/10/08)
The preparation and structural characterization of two bridged Mo2X4(LL)2 compounds is reported, and their relevance to the relationship between Mo-Mo quadruple bond length and torsional angle is discussed. Mo2Br4(dppm)2·2THF (1), where dppm = bis(diphenylphosphino)methane, crystallizes in space group P21/n with a = 11.653 (2) A?, b = 17.339 (4) A?, c = 14.409 (4) A?, β = 98.07 (2)°, V = 2882 (2) A?3, and Z = 2. There is a crystallographic center of inversion at the midpoint of the Mo-Mo bond, and the rotational conformation is eclipsed. The metal-metal bond length, 2.138 (1) A?, is identical with that in the structure of Mo2Cl4(dppm)2·2C3H 6O. Mo2Cl4(tdpm)2·2CH2Cl 2 (2), where tdpm = tris(diphenylphosphino)methane, crystallizes in space group P1 with a = 15.078 (4) A?, b = 22.941 (6) A?, c = 12.380 (3) A?, α = 104.55 (2)°, β = 107.87 (2)°, γ = 92.44 (2)°, V = 3911 (4) A?3, and Z = 2. The principal molecule possesses no crystallographic symmetry, and only two of the three phosphorus atoms of each tdpm ligand are coordinated to the molybdenum atoms. The rotational conformation is partially staggered with an average torsional angle of 20 [3]°. These new data, together with data on the bond lengths and mean torsion angles for eight other compounds of the same type, are used to show that an inverse linear relationship (correlation coefficient 0.916) exists between the Mo-Mo bond distance and cos (2χ), where χ is the angle of twist away from an eclipsed conformation.
