First metallamacrocyclic complexes of Pt(IV) with 3,3,3′,3′- tetraalkyl-1,1′-phenylenedicarbonylbis(thioureas): Synthesis by direct or electrolytic oxidative addition of i2, Br2 and Cl 2
Elemental I2 and Br2 cleanly react with the 3 : 3 Pt(II) metallamacrocycle of 3,3,3′,3′-tetra(n-butyl)-1,1′- terephthaloylbis(thiourea) (cis-[PtII3(L p1-S,O)3] 3), in chloroform at room temperature, to yield oxidative addition products; 195Pt NMR studies reveal that a stepwise oxidative addition readily occurs to each of the Pt(II) centres in the metallamacrocycle to yield the mixed valence species cis-[PtII2PtIVI2(Lp1-S,O)3] and cis-[PtIIPtIV2I4(I p1-S,O)3], and the fully oxidised cis-[Pt IV3I6(Lp1-S,O)3] in solution, depending on the mole ratio I2 : 3. Similar results are obtained on treatment of solutions of 3 with elemental Br2. Treatment of the corresponding 2 : 2 Pt(II) complex of 3,3,3′,3′-tetraethyl- 1,1′-isophthaloylbis(thiourea) (cis-[PtII2(L ml-S,O)2] 4) with iodine, results in facile oxidative addition to yield cis-[PtIV2(Lm1-S,O) 2I4] 5, with a trans-Pt(IV)-iodo arrangement. Molecules in the crystal structure of 5 have their trans-Pt(IV)-iodo axes essentially aligned, with very close intermolecular iodide contacts (3.775(1) Å), resulting in chains of weakly bound metallamacrocycles in the solid. An alternative electrolytic synthesis method, using a simple two-compartment glass cell containing 4 and a chosen halide salt in dichloromethane, led to the formation of cis-[PtIV2(Lm1-S,O) 2Br4] 6 and cis-[PtIV2(L m1-S,O)2Cl4] 7, completing characterization of a series of first-reported trans-Pt(IV)-X (X = I, Br, Cl) metallamacrocyclic complexes. © The Royal Society of Chemistry 2005.