Inducing Platinophilic Interactions in [Pt(SCN) 4 ] 2- Salts by Cation Tuning.

A series of simple [Pt(SCN) 4 ] 2- salts with a variety of cations was synthesized and characterized using X-ray crystallography to determine factors that could induce platinophilic interactions between [Pt(SCN) 4 ] 2- anions, including cation size and shape, charge, and ability to participate in hydrogen bonding. The salts [N(PPh 3 ) 2 ] 2 [Pt(SCN) 4 ], [AsPh 4 ] 2 [Pt(SCN) 4 ], and [Co(1,10-phenanthroline) 3 ][Pt(SCN) 4 ] feature bulky, noncoordinating cations where the [Pt(SCN) 4 ] 2- anions are completely separated from each other, with no Pt-Pt interactions present. Salts containing the hydrogen-bonding cations [Co(NH 3 ) 6 ] 2 [Pt(SCN) 4 ] 3 and [Co(en) 3 ] 2 [Pt(SCN) 4 ] 3 (en = 1,2-ethylenediamine) display close Pt-Pt distances, with both compounds exhibiting platinophilic interactions with distances of 3.373(2) and 3.539(8) Å, respectively, the first reported platinophilic interactions with the [Pt(SCN) 4 ] 2- unit. [Co(en) 3 ] 2 [Pt(SCN) 4 ] 3 also presents intermolecular chalcogen S···S and Pt···S interactions, resulting in increased dimensionality while also assisting in assembling the platinophilic interaction. The compounds are emissive at 77 K in the solid state, exhibiting a d-d metal-centered transition regardless of whether or not any platinophilic interactions are present. Overall, hydrogen-bonding cations are most likely to promote close proximity of the Pt(II) metal centers and induce the formation of platinophilic interactions in [Pt(SCN) 4 ] 2- .