Di-mu-halogeno-bis[halogeno(triphenylphosphine)mercury(II)], [Ph3PHgX(mu-X)2XHgPPh3], reinvestigated at 120 K for X = Cl and Br, and a second polymorph for X = I, also at 120 K.

Di-mu-chloro-bis[chloro(triphenylphosphine)mercury(II)], [Hg2Cl4(C18H15P)2], (I), and di-mu-bromo-bis[bromo(triphenylphosphine)mercury(II)], [Hg2Br4(C18H15P)2], (II), have been reinvestigated at 120 K. The molecules of (I) lie across inversion centres in space group P2(1)/n, and in both (I) and (II) the complexes are linked into three-dimensional frameworks by a combination of C-H...X (X = Cl and Br) and C-H...pi(arene) hydrogen bonds. At 120 K, di-mu-iodo-bis[iodo(triphenylphosphine)mercury(II)], [Hg2I4(C18H15P)2], (III), crystallizes as a new polymorphic form having Z' = 1/2, where the complexes lie across inversion centres in space group P2(1)/n; the complexes are linked into sheets by a combination of C-H...I and C-H...pi(arene) hydrogen bonds. In the Z' = 1 polymorph of this compound, a single C-H...I hydrogen bond generates simple chains.