Synthesis, Spectroscopy, and Structure of [FeRu(μ-dithiolate)(CN)₂(CO)₄]^2–

Abstract

The salt [K(18-crown-6)] 2 [Ru(CN) 2 (CO) 3 ] ([K(18-crown-6)] 2 [1]) was generated by the reaction of Ru(C 2 H 4 )-(CO) 4 with [K(18-crown-6)]CN. An initial thermal reaction gives [Ru(CN)(CO) 4 ] − , which, upon ultraviolet (UV) irradiation, reacts with a second equiv of CN − . Protonation of [1] 2− gave [HRu(CN) 2 (CO) 3 ] − ([H1] − ), which was isolated as a single isomer with mutually trans cyanide ligands. The complex cis,cis,cis-[Ru(pdt)implicates intermetallic migration of CN − . In contrast, the formation of [5] 2− leaves the Ru(CN) 2 (CO) center intact, as confirmed by X-ray crystallography. The structure of [5] 2− features a "rotated" square-pyramidal Fe(CO) 2 (μ-CO) site. NMR measurements indicate that the octahedral Ru site is stereochemically rigid, whereas the Fe site dynamically undergoes turnstile rotation. 57 Fe Mossbauer spectral parameters are very similar for rotated [5] 2− and unrotated Fe 2 complex [4] 2− , indicating the insensitivity of that technique to both the geometry and the oxidation state of the Fe site. According to cyclic voltammetry, [5] 2− oxidizes at E 1/2 ∼ −0.8 V vs Fc +/0 . Electron paramagnetic resonance (EPR) measurements show that 1e − oxidation of [5] 2− gives an S = 1/2 rhombic species, consistent with the formulation Ru(II)Fe(I), related to the H ox state of the [FeFe] hydrogenases. Density functional theory (DFT) studies reproduce the structure, 1 H NMR shifts, and infrared (IR) spectra observed for [5] 2− . Related homometallic complexes with both cyanides on a single metal are predicted to not adopt rotated structures. These data suggest that [5] 2− is best described as Ru(II)Fe(0). This conclusion raises the possibility that for some reduced states of the [FeFe]-hydrogenases, the [2Fe] H site may be better described as Fe(II)Fe(0) than Fe(I)Fe(I).

[Ru3(CN)3(CO)9]3−:Building Block for Multimetallic Cages

“…The reaction is best conducted with venting to remove CO, otherwise one observes formation of [Ru(CN) n (CO) 4À n ] nÀ . [6] In this way, we obtained a good yield of orange microcrystals of (NEt 4 ) 3 [Ru 3 (CN) 3 (CO) 9 ] (eq. 1):…”

“…Treating an MeCN slurry of Ru 3 (CO) 12 with three equivalents of NEt 4 CN results in a red‐orange solution over the course of hours at room temperature. The reaction is best conducted with venting to remove CO, otherwise one observes formation of [Ru(CN) n (CO) 4−n ] n− [6] . In this way, we obtained a good yield of orange microcrystals of (NEt 4 ) 3 [Ru 3 (CN) 3 (CO) 9 ] (eq.…”