Paper Crystal packing in tetraphenylphosphonium salts of trithiocyanuric acid and its methanol solvate Philip A. W. Dean,* a Michael Jennings, a Teena M. Houle, a Donald C. Craig, b Ian G. Dance,* b James M. Hook b and Marcia L. Scudder b a Department of Chemistry, University of Western Ontario, London, ON, N6A 5B7, Canada b School of Chemistry, University of New South Wales, Sydney 2052, Australia Received 26th August 2004, Accepted 7th October 2004 First published as an Advance Article on the web 19th October 2004 Trithiocyanuric acid (1,3,5-triazine-2,4,6(1H,3H,5H)-trithione, commonly known as 2,4,6-trimercaptotriazine TMTH 3 ) is a weakly acidic planar molecule with threefold symmetry, and, at the N and S atoms, it contains three hydrogen bond donors and three acceptors, respectively. For this reason it has been used previously for the formation of crystals containing 1- or 2-D hydrogen bonded nets. In this paper we describe and discuss aspects of the crystal packing of Ph 4 P 1 salts of TMTH 2 2 and TMTH 22 (capable of forming coordination complexes). The crystals reported are (Ph 4 P 1 ) 2 TMTH 22 (H 2 O) 3 1, Ph 4 P 1 TMTH 2 2 H 2 O 2, and Ph 4 P 1 TMTH 2 2 3, together with TMTH 3 CH 3 OH 4. Standard multiple phenyl embrace motifs between Ph 4 P 1 occur in 1 and 3 as zig-zag chains of sixfold edge-to-face interactions (EF) 6 , resulting in channels containing 1-D tapes of fully hydrogen bonded TMTH 2 2 molecules in 3, while in 1 the fewer TMTH 22 ions in the channels are separated by hydrogen bonded water molecules. In 2 there are corrugated sheets of TMTH 2 2 which hydrogen bond in pairs linked by hydrogen bonded water molecules, without standard multiple phenyl embraces between Ph 4 P 1 . Unsolvated crystals of TMTH 3 are not known, but the methanol solvate 4 contains a completely hydrogen bonded net in which 1-D tapes of TMTH 3 are linked by chains of CH 3 OH. Introduction The weakly acidic molecule 1,3,5-triazine-2,4,6(1H,3H,5H)- trithione, more commonly known as trithiocyanuric acid or 2,4,6-trimercaptotriazine TMTH 3 (adopted for this paper), has been used in a number of research programs intending to design distinctive crystals. The molecule has the attributes of high symmetry and planarity, coupled with three hydrogen bond donors and three acceptors. The pK a ’s are 5.7, 8.4, 11.4, 1 allowing varying degrees of deprotonation, and the resulting anions can function as thiolate or amide ligands for metals. As illustrations of the crystal packing engendered by TMTH 3 and derivatives: (1) the crystal (TMTH 3 ) 2 (acetone) (CSD refcode NOVZUT) contains stacks of a fully hydrogen bonded pseudo-hexagonal planar 2D net as shown in Fig. 1 (a); (2) crystals containing TMTH 2 2 with the [Na(1,10-phen) 3 ] 1 cation (OLIXEM) contain a zig-zag 1-D chain of hydrogen bonded TMTH 2 2 as shown in Fig. 1 (b); (3) with a complementary ditopic hydrogen bond acceptor, 4,4’-bipyr- idine, stacks of a different 2-D pseudo-hexagonal hydrogen bonded net occur, as illustrated in Fig. 1 (c), and these include various solvent molecules (refcodes EHIRAO, EHIRES, EHIRIW, EHIROC, NOVZON). 2,3 Centrosymmetric (N–H … ) 2 connections are dominant. Ligated Cu or Au complexes of TMT 32 such as (TMT)(AuPPh 3 ) 3 are known, and condense to small luminescent clusters. 4 We have been interested in developing the coordination chemistry of TMTH x 3 2 x , and incorporating its metal com- plexes into designed crystals. Under aqueous conditions the metal salts that are formed by the acid usually have very low solubility 1,5 probably indicative of extensive networking in the solid state, a complication for crystal growth. Therefore we sought to use Ph 4 P 1 salts of TMTH x 3 2 x , in order to enable and control metal complex formation in non-aqueous solvents. We also envisaged utilisation of our knowledge of the crystal packing principles of phenyl phosphonium cations. In this paper we describe some results on the crystallisation and crystal structures of Ph 4 P 1 salts of TMTH 2 2 and TMTH 22 , and incorporate them into the crystal packing principles for TMTH 3 and its derivatives. Results Crystallisation Methanol/water solutions of Na 1 3 TMT 32 (H 2 O) 9 and Ph 4 P 1 Br 2 in molar ratios 1:2 or 1:1 have a pH of about 12, and the first product to crystallise from them is flaky (Ph 4 P 1 ) 2 TMTH 22 (H 2 O) 3 1. This compound has been recrys- tallised as such from a non-aqueous mixture of chloroform plus diethyl ether. Crystals of the same composition are obtained by allowing a methanolic solution of Na 1 3 TMT 32 (H 2 O) 9 and Ph 4 P 1 Br 2 (1:2) to diffuse into water. When methanol is allowed to evaporate slowly from the supernatant liquid from the bulk synthesis of 1, pale yellow prisms of Ph 4 P 1 TMTH 2 2 H 2 O 2 are obtained, consistent with hydrolysis of TMTH 22 to TMTH 2 2 . Crystals of 2 may also be obtained by slow evaporation of MeOH from a dilute solution of 1 in methanol/water. Attempted crystallisation of 1 (containing the DOI: 10.1039/b413145b CrystEngComm, 2004, 6(88), 543–548 543 This journal is # The Royal Society of Chemistry 2004