beta-Diketonato complexes [Tl{CH{C(O)R}(2)}] or PPN[Au{CH{C(O)R}(2)}(2)] [where PPN = (Ph3P)(2)N] react with an excess of CS2 to give, respectively, [Tl-2{S2C=C{C(O)R}(2)}](n) [R = Me (1) or Ph (2)] or (PPN)(2)[Au-2{mu-kappa(2)-S2C=C{C(O)R}(2)}(2)] [R = Me (3 . PPN) or Ph (4 . PPN)]. The gold complexes 3 . PPN and 4 . PPN can also be obtained from PPN[AuCl2] and the corresponding thallium 1,1-ethylenedithiolate. PPN[AuCl4] reacts with 1 to give PPN[Au{kappa(2)-S2C=C{C(O)Me}(2)}(2)] (5) which, in turn, reacts with PhICl2, Br-2 or I-2 (1:1) to give PPN[AuX2{kappa(2)-S2C=C{C(O)Me}(2)}] [X = Cl (6), Br (7), or I (8)]. By reacting 6 with TlCF3SO3 and 1,10-phenanthroline (phen) in 1:2:1 molar ratio, the cationic complex [Au{kappa(2)-S2C=C{C(O)Me}(2)}(phen)]CF3SO3 (9) can be obtained. The crystal structures of 5 and 6 . 0.5Me(2)CO have been determined. Third-order nonlinearities of 3 . PPN, 3 . Pr4N, 5, and 6 have been evaluated by the Z-scan technique; an increase in nonlinearity upon extending the pi-system is observed, with the anionic dimetallacycle containing two gold and four sulfur atoms in 3 responsible for the largest nonlinearities (approximately 100 x 10(-36) esu).