Synthesis, characterization, and photochemistry of a dinuclear cyanide-bridged iron(II)-platinum(IV) mixed-valence compound and its implications for the corresponding iron(II)-platinum(IV)-iron(II) complex
Bw. Pfennig et al., Synthesis, characterization, and photochemistry of a dinuclear cyanide-bridged iron(II)-platinum(IV) mixed-valence compound and its implications for the corresponding iron(II)-platinum(IV)-iron(II) complex, INORG CHEM, 38(12), 1999, pp. 2941-2946
The mixed-valence compound [(NH3)(5)Pt-IV(mu-NC)Fe-II(CN)(5)]. 6H(2)O was s
ynthesized by the substitution reaction of [Pt-IV(NH3)(5)OSO2CF3](OSO2CF3)(
3) and [Fe-II(CN)(6)](4-) in aqueous solution and was characterized by UV/v
is, IR, and resonance Raman spectroscopies, cyclic voltammetry, and single-
crystal X-ray diffractometry. The monoclinic crystal (space group P2(1)/m (
No. 11)) consists of a dinuclear, cyanide-bridged Fe(II)-Pt(IV) moiety with
unit cell dimensions of a = 9.3241(5) Angstrom, b = 14.0466(7) Angstrom, c
= 9.6938(4) Angstrom, beta = 111.467(2)degrees, and Z = 2. There are also
an average of six waters of hydration per unit cell. The R-factors for this
structure are R = 3.66% and R-w = 7.90%. The electronic spectrum reveals a
broad intervalent (IT) charge-transfer absorption at approximately 420 nm
(epsilon = 540 M-1 cm(-1)). Both the ground-state spectroscopy and the elec
trochemistry of this compound are very similar to those of the correspondin
g trinuclear adduct [(NC)(5)Fe-II(mu-CN)Pt-IV(NH3)(4)(mu-NC)Fe-II(CN)(5)](4
-), which has been reported previously. Classical Marcus-Hush theory has be
en applied in the analysis of the IT band of the dinuclear compound in an e
ffort to elucidate a fuller understanding of the photophysics of the trinuc
lear complex. The data suggest that this latter, centrosymmetric species ca
n be treated theoretically as two back-to-back dinuclear donor-acceptor (D-
A) compounds of the form D-A/A-D, where the Pt(IV) inversion center acts as
the acceptor for both halves of the molecule. The photochemistry of the di
nuclear complex was also investigated.