Diversity in the structural chemistry of (phosphine)gold(I) 1,3,4-thiadiazole-2,5-dithiolates (bismuthiolates I)

A series of dinuclear (phosphine)gold(I) complexes of the ambidentate 1,3,4 -thiadiazoledithiolate ligand (SSS) were prepared in high yield from the co rresponding (phosphine)gold(I) chlorides and K-2(SSS) in methanol. While mo nonuclear components (R3P)AuCl with R-3 = Ph-3, Ph2Py, or Me-3 (1-3) crave open-chain complexes, the dinuclear components ClAu(Ph2P-E-PPh2)AuCl with E = (CH2)(6), (C5H4)Fe(C5H4), or 1,4-CH2C6H4CH2 afforded cyclic complexes (4 -6). The products have been characterized by analytical and spectroscopic m ethods, and the crystal structures of 1-4 have been determined by single-cr ystal X-ray techniques. Crystals of 1 [(CH2Cl2)(2)] and 2 (CH2Cl2) contain the molecules aggregated in strings with long and probably very weak interm olecular Au . . .S contacts. The P-Au-S groups are aligned parallel head-to -tail and shifted in opposite directions to reduce steric conflicts, thus r uling out aurophilic Au . . . Au bonding. By contrast, in crystals of 3 (CH 2Cl2) with smaller tertiary phosphine ligands, the molecules are aggregated via short [3.0089(3) and 3.1048(5) Angstrom] and probably strong aurophili c bonding to give a two-dimensional network with tetranuclear units formed from four (Me3P)AuS moieties of four different molecules as the connecting elements. In these tetranuclear units [(Me3P)AuS-](4), the P-Au-S axes are rotated against each other ("crossed swords") by 108.5 degrees (P2-Au2 . . . Au2'-P2') or 116.9 degrees (P2-Au2 . . . Au1'-P1'), respectively, to mini mize steric conflicts. There is also significant bending of the P-Au-S axes to bring the metal atoms closer together: P1-Au1-S1 = 171.88(8)degrees and P2-Au2-S2 = 165.52(8)degrees. In the crystals of the cyclic complex 4 whic h contain no solvent molecules, the molecular units are aggregated in strin gs with short closed-shell interactions between the gold atoms of neighbori ng molecules [3.1898(3) Angstrom]. Because of the metallocyclic structure, the shielding of the gold atoms is reduced to allow aurophilic bonding as t he P-Au-S groups are rotated against each other (crossed) by a dihedral ang le P-Au . . . Au-P of 74.6 degrees.