Pt2 II and Pt2 III dimers containing a Pt2(2,2′-bipyridine)2(μ-N,N- dimethyl-guanidinato)2 unit

The syntheses and crystal structures of the title Pt2 ^II and Pt2 ^III dimers doubly bridged with N,N-dimethyl-guanidinate ligands, namely bis-(μ-N,N-dimethyl-guanidinato)bis-[(2,2′-bipyridine) platinum(II)](Pt - Pt) bis-(hexa-fluoro-phosphate) acetonitrile disolvate, [Pt2 ^II(C3H8N3)2(C10H8N2)2](PF6)2·2CH3CN, (I), and guanidinium bis-(μ-N,N-dimethyl-guanidinato)bis-[(2,2′-bipyridine) sulfatoplatinum(III)](Pt - Pt) bis-(hexa-fluoro-phosphate) nitrate hexa-hydrate, (C3H10N3)[Pt^III 2(C3H8N3)2(SO4)2(C10H8N2)2]NO3·6H2O, (II), are reported. The oxidation of the Pt2 ^II dimer into the Pt2 ^III dimer results in a marked shortening of the Pt - Pt distance from 2.8512 (6) to 2.5656 (4) Å. The change is mainly compensated for by the change in the dihedral angle between the two Pt coordination planes upon oxidation, from 21.9 (2) to 16.9 (3)°. We attribute the relatively strong one-dimensional stack of dimers achieved in the Pt2 ^II compound in part to the strong Pt^II⋯C(bpy) associations (bpy is 2,2′-bipyridine) in the crystal structure [Pt⋯C = 3.416 (10) and 3.361 (12) Å].