Dinuclear platinum(II) complexes with bridging twofold deprotonated 2,2 ': 6 ',2 ''-terpyridine. New molecules with a 3,5-diplatinated-pyridyl inner core: [Pt-2(terpy-2H)(Me)(2)(L)(2)], [Pt-2(terpy-2H)(X)(2)(L)(2)] and [Pt-2(terpy-2H)(H)(2)(L)(2)] (L = neutral ligand; X = halide) - Crystal and molecular structure of [Pt-2(terpy-2H)(Cl)(2)(PPh3)(2)] RID D-3096-2011

A series of dinuclear platinum complexes where the metal ions are linked by a twofold deprotonated 2,20:60,200-terpyridine (terpy) has been synthesized. Reaction of cis-[Pt(Me)2(DMSO)2] with terpy in toluene at 90 C (molar ratio Pt:terpy 2:1) results in activation of the C(3)- and C(5)–H bonds of the inner pyridinic ring to give the cyclometalated dinuclear derivative [Pt2(terpy-2H)(Me)2(DMSO)2] (1a), (trans Me–Pt–N). From complex 1a, substitution of DMSO with neutral two-electron donors, L, allows isolation of a number of new species [Pt2(terpy-2H)(Me)2(L)2] with the same N,CC,N bridging ligand. The ‘‘Pt2(terpy-2H)’’ fragment is very robust: it is not affected by alkylating reagents such as MeI or acids such as HPF6 or even HCl. Nevertheless the latter acid cleaves the Pt–Me bond affording another series of complexes having a chloride in place of a methyl, [Pt2(terpy-2H)(Cl)2(L)2], (trans-Cl–Pt–C). The structure of complex 7, [Pt2(terpy-2H)(Cl)2(PPh3)2], has been solved by X-ray analysis: the platinum atoms are in a tetrahedrally distorted square planar coordination. The inner framework of the molecule is not flat: the dihedral angle between the best planes of the metal ions is 37.2(1). The coordinated chlorides can be abstracted to give cationic solvento derivatives or exchanged with other anions such as iodides. Exchange with [BH4] allows to obtain the corresponding hydrides, examples of very rare C,N cyclometalated platinum(II) hydrides. Finally a two step approach allows the synthesis of unsymmetric derivatives, [Pt2(terpy-2H)(Cl)2(L)(L0)], with different ligands around each platinum atom. The surprising deprotonation of terpy, typically a neutral ligand, points to the potential of the ‘‘Pt(Me)2’’ fragment in the intramolecular C–H bond activation.