Stoccoro, Sergio and Zucca, Antonio and Petretto, Giacomo Luigi and Cinellu, Maria Agostina and Minghetti, Giovanni and Manassero, Mario (2006) Dinuclear platinum(II) complexes with bridging twofold deprotonated 2,2′:6′,2″-terpyridine: new molecules with a 3,5-diplatinated-pyridyl inner core: [Pt2(terpy-2H)(Me)2(L)2], [Pt2(terpy-2H)(X)2(L)2] and [Pt2(terpy-2H)(H)2(L)2] (L = neutral ligand; X = halide) – Crystal and molecular structure of [Pt2(terpy-2H)(Cl)2(PPh3)2]. Journal of Organometallic Chemistry, Vol. 691 (19), p. 4135-4146. ISSN 0022-328X. Article.
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A series of dinuclear platinum complexes where the metal ions are linked by a twofold deprotonated 2,2′:6′,2″-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,C^C,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)(L′)], 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.
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