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 Cl2

Abstract

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-[Pt^II₃(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-[Pt^II₂Pt^IVI₂(L^p1-S,O)₃] and cis-[Pt^IIPt^IV₂I₄(L^p1-S,O)₃], and the fully oxidised cis-[Pt^IV₃I₆(L^p1-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-[Pt^II₂(L^m1-S,O)₂] 4) with iodine, results in facile oxidative addition to yield cis-[Pt^IV₂(L^m1-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-[Pt^IV₂(L^m1-S,O)₂Br₄] 6 and cis-[Pt^IV₂(L^m1-S,O)₂Cl₄] 7, completing characterization of a series of first-reported trans-Pt(IV)–X (X = I, Br, Cl) metallamacrocyclic complexes.