The syntheses, structures, and electronic and resonance-Raman spectroscopy of halogen-bridged platinum(II,IV) chain complexes involving equatorially co-ordinated terdentate amines: X- ray crystal structure of [Pt II (Me-dien)I][Pt IV (Me-dien)I3]I2, and spectroscopy of [Pt II (dien)(NO2)][Pt IV (dien)(NO2)Br2]Br2

Abstract

Three chain platinum(II,IV) complexes of the type [PtL3X][PtL3XY2]Z2(L3= terdentate ligand, X = halogen or NO2–, Y = halogen, Z = monoanion) have been synthesised. Two of these have been studied in detail, one by X-ray and the other by spectroscopic methods. The first, [Pt(Me-dien)I]-[Pt(Me-dien)I3]I2(Me-dien =N-methyldiethylenetriamine), has been found to crystallize in the monoclinic space group P21/n, with a= 19.830(8), b= 12.220(5), c= 11.079(6)A, β= 96.49(4)°, and Z= 4. Refinement on 1 543 independent reflections led to a final R value of 0.043. The Pt–I chain distances are 2.679(3) and 2.691(3)A(PtIV) and 3.443(3) and 3.560(3)A(PtII) the chain deviating substantially at iodine and platinum(II) from linearity [PtIV–I–PtII= 150.5(1) and 149.1(1)°; I–PtII-I = 162.8(1)°], but not at platinum(IV)[I–PtIV–I = 179.4(1)°]. The second complex studied in detail, [Pt(dien)(NO2)][Pt(dien)(NO2) Br2] Br2(dien = diethylenetriamine), was found to yield a very intense resonance-Raman spectrum, the principal observed progression being v1ν1, where ν1(181.5 cm–1) is the symmetric stretching mode of the chain, νsym(Br–PtIV–Br). Analysis of these data yields ω1 and x11 values of 181.9 and –0.2 cm–1, respectively. Further, much weaker, progressions of the sorts v1ν1+νsym(NO2)(to v1= 5) and v1ν1+δsym(NO2)(to v1= 4) were also detected. The results add substantially to the few previously known data on halogenbridged mixed-valence chain complexes of platinum in which each unit carries a single positive charge.