Coordination variability of Copper(I) in multidonor heterocyclic thioamides.

The chemistry of copper(I) with scarcely studied heterocyclic thioamides, namely, 2,4,6-trimercaptotriazine, purine-6-thione, 2,4-dithiouracil, 2-thiouracil and pyrimidine-2-thione is described. The interaction of 2,4,6-trimercaptotriazine (tmtH3) with [Cu(CH3COO)(PPh3)2] gave rise to a pair of bond isomers : [Cu(κ1N-tmtH2)(PPh3)2] (6a), [Cu(κ1N,κ1S-tmtH2)(PPh3)2] (6b) and with copper(I) bromide and PPh3, it has formed a trinuclear complex, [Cu3Br2(κ1N,κ1S,κ2S-tmtH2)(PPh3)6] (7) with anionic tmtH2- in these complexes. The 2,4-dithiouracil with copper halides (CuCl, CuBr) and PPh3 yielded dinuclear complexes: [Cu2(κ2Cl)(κ1S,κ1S-dtucH)(PPh3)4] (4) and [Cu2(κ2Br)(κ1S,κ1S-dtucH)(PPh3)4] (5) with unusual eight membered metallacyclic rings. Pyrimidine-2-thione (pymSH) coordinated to CuI as N,S-chelated anion yielding mononuclear complex, [Cu(κ1N,κ1S-pymS)(PPh3)2] (1), while 2-thiouracil (tucH2) with copper(I) chloride and PPh3 yielded a tetrahedral complex, [CuCl(κ1S-tucH2)(PPh3)2] (3). Purine-6-thione (purSH2) coordinated to CuI in two different modes yielding mono- and di-nuclear complexes, [Cu(κ1N,κ1S-purS)(PPh3)2].CH3OH (2a) and [Cu2(κ1N,κ2S-purS)2(PPh3)2] (2b). The existence of bond isomers (6a and 6b), synthesis of novel dinuclear ( 4 and 5) and rare trinuclear (7) complexes with unusual bonding patterns and uncommon chelation to CuI by pymS- in 1 are the novel features of the present study. Complexes have shown intense emission bands in the visible region, λmax 490 to 495 nm.