Platinum, polysulfide complexes

The new complex anion [PtSi8]2- gave (31) a crystalline salt with the tetraphenyl-phosphonium ion. The anions were [Pt(S6)3]2 , with three seven-membered chelate rings the angles within the rings, 8-Pt-8, were much larger than 90 . These systems containing platinum ions complexed by polysulfides are thus chemically rather more complicated than expected. 

Although inhibitors are deliberately added to the silicone formulation to control cure rate, unwanted cure inhibition can be caused by other species that react to form strong complexes with the platinum catalyst. Most notable of these undesired inhibitors include organotin and other organometallic compounds, sulfur, polysulfides, polysulfones or other sulfur-containing materials, amines, urethanes or amine-containing materials, unsaturated hydrocarbons in plasticizers, and some solder flux residues. 

Palladium and platinum have a high affinity for sulfur donors e.g., S02 and SOI are coordinated via S rather than O. Polysulfide dianions S2n form complexes with... 

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