Unprecedented Formation of Novel Phosphonodithioate Ligands from Diferrocenyldithiadiphosphetane Disulfide

The reaction of the phosphetane disulfide, FcP(S)S2P(S)Fc (1) (Fc = (η5-C5H5)Fe(η5-C5H4)), the ferrocenyl analogue of the Lawesson reagent, with gold and palladium complexes leads to the unprecedented formation of phosphonodithioate ligands upon coordination to the metal centers. The reaction of 1 with gold complexes such as [AuCl(PR3)] affords the species [Au{S2P(OH)Fc}(PR3)] (PR3 = PPh3 (2), PPh2Me (3)), in which the phosphonodithioate ligand Fc(OH)PS2− has been formed. The same ligand is present in the compound [Au2{S2P(OH)Fc}2]·[N(PPh3)2]Cl (4), obtained by reaction of 1 with [N(PPh3)2][AuCl2]. It crystallizes with one molecule of [N(PPh3)2]Cl, whereby complex 4 acts as an anion receptor and forms strong hydrogen bonds between the chloro and the hydroxyl groups. The reaction with palladium derivatives is different; two complexes, [Pd2(S4OP2Fc2)2] (5) and [Pd4Cl4(S4OP2Fc2)2] (6), are obtained in molar ratio 2:1 and 1:1, respectively. In these complexes a new phosphonodithioate ligand is present and probably arises from the condensation of two molecules of Fc(OH)PS2−. Complex 5 has also been characterized by X-ray methods.