POLYMORPHS OF TETRAKIS(GLYCINE)TETRACHLORODIMOLYBDENUM(II)

The compound Mo2(gly)4Cl4-xH20 has been obtained in two different crystalline forms, each of which has been structurally characterized by X-ray crystallography. Form 1 has x = 3 and crystallizes in the space group P2,/c with the following unit cell dimensions: a = 8.350 (3) ℨ, b = 9.346 (3) ℨ, c= 14.807 (4) ℨ, β = 103.42 (3)°, V = 1124 (1) A3, Z = 2. Form 2 has x = 2.67 and crystallizes in the space group PI with unit cell dimensions of a = 11.941 (9) ℨ, b = 12.022 (9) ℨ, c = 11.614 (9) ℨ, α = 92.42 (7)°, β = 92.04 (7)°, y = 88.94 (7)°, V= 1664.(4) A3, Z = 3. In 1 there are two equivalent Mo2(gly)44+ions per unit cell, each located on a crystallographic center of symmetry, with d(Mo-Mo) = 2.112 (1) ℨ. There is weak axial coordination of CI-, with d(Mo…Cl) = 2.882 (1) A. In 2, there are three crystallographically independent molecules, each residing on a crystallographic inversion center. These have Mo-Mo distances of 2.107 (l), 2.110 (1), and 2.103 (1) ℨ and Mo-Cl distances of 2.907 (1), 2.869 (2), and 2.829 (2) ℨ, in the same order. In all four crystallographically independent Mo2(gly)4Cl2units the dimensions are thus effectively the same, and in all four there is virtual Dihsymmetry. Those CI'ions not loosely coordinated to the Mo2(gly)44+units are hydrogen bonded to NH3+and H2O. © 1979, American Chemical Society. All rights reserved.