Two tautomers of the new phosphinoaminothiazoline Ph2PNHCNCH2CH2S (1), obtained from the reaction of 2-amino-2-thiazoline (ATHZ) with Ph2PCl, have been structurally characterized and the intermediate formation of the diphosphine Ph2PNCN(PPh2)CH2CH2S (2) has been demonstrated experimentally and by DFT calculations; 2 reacts with [AuCl(THT)] to give [(AuCl)22] whereas the bidentate metalloligand cis-[Pt(1−H)2] reacts with AgOTf to form the Ag–Pt coordination polymer [Ag∞[Pt(1−H)2]∞](OTf)∞.