SET OF HOMOLOGOUS QUADRUPLY BONDED MOLECULES OF DICHROMIUM(II), DIMOLYBDENUM(II), AND DITUNGSTEN(II) WITH THE LIGAND 2,4-DIMETHYL-6-HYDROXYPYRIMIDINE

The hexacarbonyls of chromium, molybdenum, and tungsten react with 2,4-dimethyl-6-hydroxypyrimidine, Hdmhp, in refluxing diglyme to give the M2(dmhp)4 molecules. These crystallize from diglyme solution in two crystal forms. Form I crystals, obtained within the first 12 h, have the composition M2(dmhp)4.1/2(diglyme) and belong to space group P21/n with the following unit cell dimensions, where values for the Cr and W compounds are given in that order: a = 14.655 (4), 14.783 (3) Å; b= 14.881 (4), 14.929 (3) Å; c = 14.415 (4), 14.521 (4) Å; β = 90.43 (2), 90.00°. It was not possible to refine the disordered solvent molecules in these crystals. Form II crystals, obtained over a longer period of time, have the composition M2(dmhp)4-diglyme. These belong to the space group P21/c and have the following unit cell dimensions, where values for the Cr, Mo, and W compounds are given in that order: a = 1 1.502 (3), 1 1.538 (1), 1 1.544 (3) Å; b = 9.702 (2), 9.739 (1), 9.742 (2) Å; c = 31.372 (8), 31.659 (4), 31.583 (8) Å; β = 98.55 (2), 98.22 (1), 98.18 (2)°. These form II structures were refined to R1, values of 0,073, 0.049, and 0.043 for the Cr, Mo, and W compounds, respectively. The metal-metal distances are Cr-Cr = 1,907 (3) Å, Mo-Mo = 2,072 (1) Å, and W-W = 2,163 (1) Å, The M2(dmhp)4 molecules have virtual D2d symmetry, although there is no crystallographically imposed symmetry since there is one entire molecule in the asymmetric unit. © 1979, American Chemical Society. All rights reserved.