POLYMORPHS OF [Au(dppm)Cl]₂. Ju-Chun Wang, Lin-Shu Liou and Shin-Jine Chen, Department of Chemistry, Soochow University, Taipei, Taiwan 11102, Rep. Of China

Three different polymorphs of [Au(dppm)Cl]₂ have been successfully grown from dichloromethane (DCM). The only different grown condition is that the DCM solution of the title compound contains different amount of water. Polymorphs I and II were obtained from dried DCM solution. Two other polymorphs, which were co-crystallized with either acetone or acetonitrile were reported. The molecular structures of these four polymorphs were similar except that they have different co-crystallized solvents. Short Au-Au contact and terminal type of Au-Cl bond have been observed in these polymorphs. They are 2.975(3) for polymorph I and 3.007(1) for polymorph II, which are comparable to those found in the other two polymorphs. Though all of these polymorphs show similar terminal Au-Cl bond, polymorph II has exceptional short Au-Cl distance of 2.760(3). Polymorph III was crystallized from DCM solution saturated with water. The molecular structure in this polymorph is totally different from the others. One of Cl^- bridging between two Au(I) centers and the other is served as a counter ion. Two Au-Cl distances are 2.977(9) and 2.955(9) This is the first and the only polymorph of [Au(dppm)Cl]₂ with bridging Cl^-. The Au-Au separation, 2.938(2), is significant short than those found in the terminal type of polymorphs. Due to the structural difference, the luminescent maximum for polymorph III is different from the others.

Crystal Data: polymorph I, a=13.047(1), b=19.425(2), c=11.531(1), b=116.120(1)^o, V=2623.8(6)³, monoclinic, P2₁/c, R=0.0475; polymorph II, a=10.962(1), b=11.276(1), c=12.147(1), a=109.091(1), b=107.667(2), g=97.707(2)^o, V=1305.7(4)³, triclinic, P-1; R=0.0495; polymorph III, a=23.712(2), c=19.931(2), V=11206(2)³, tetragonal, I4, R=0.0549.