Electrochemistry of methylidyne and 1,2,3,5-dithiadiazole complexes of iron and nickel and a reinterpretation of the composition of "PhCN₂S₂Fe₂(CO)₆"

Abstract

Abstract:The title compounds have been studied in CH2CI, by cyclic voltammetry. Nonacarbonyldi(p,-methylidyne)triiron, [Fe3(CO),(p3-CX),] (X = F, CI, Br, H), undergo chemically reversible le-reduction (-0.72 to -0.88 V vs. SCE) and irreversible oxidation (+1.59 to +I .72 V); the compound for which X = F displays a second, irreversible reduction (-1.96 V). Using reduction potentials of comparable p,-E (E = S, Se, NPh, PPh) clusters, p,-methylidyne ligands are shown to be strongly basic, comparable to PPh and NPh and more basic than S or Se. The methylidyne clusters are both more difficult to oxidize and reduce than isomeric alkyne clusters [Fe3(C0),(C2R,)], indicative of greater thermodynamic stability. The complexes previously formulated as [Fe2(CO),(S2N2CC6H,X)] (X = H, CF,, OCH,) are reversibly reduced (-1.59 to -1.70 V) and irreversibly oxidized (+1.0 to 1.3 V), unlike free dithiadiazole radicals, which are reversibly oxidized around +0.8 V. This behaviour is not consistent with the ring-centered free radical claimed for the case where X = H; instead we find conclusive evidence that these are diamagnetic complexes of the 3-H-1,2,3,5-dithiadiazolines, [Fe,(CO),(S,N(NHJCC6H,X)] (vNH = 3376-3381 cm-I; fjNH = 6.55-7.1 ppm). Dicyclopentadienyldithiadiazoledinickel, [Ni2Cp2(S,N2CC6H5)], is both reversibly reduced (-0.79 V) and oxidized (+0.45 V);and irreversibly oxidized at + 1.9 V. This is consistent with an unpaired electron, and only the nickel cluster has an ESR signal (g = 2.041 0, no resolved hyperfine splitting). Extended Huckel theory locates the free electron in a SOMO restricted to Ni, C, and S atoms.Key words: electrochemistry, organometallic, methylidyne, dithiadiazole, dithiadiazoline.Received April 6, 1995.

Metal-radical coordination complexes of thiazyl and selenazyl ligands

“…It was later discovered that the orange product is actually the related diamagnetic imine Fe 2 (CO) 6 PhDTDAH (Fig. 2), bearing a hydrogen atom at one of the thiazyl N sites [22,35,36]. Reports of reactions between PhDTDA and a variety of other low valent metal precursors soon followed, illustrating a diverse series of S-coordination motifs.…”

Coordination complexes of thiazyl rings — Synthesis, structure, and density functional theory (DFT) computational analysis of CpCr(CO)x(x= 2, 3) complexes of fluorinated and nonfluorinated 1λ3-1,2,4,6-thiatriazinyls with differing Cr–S bond orders

“…Instead, it undergoes a clean insertion reaction with the Pt(0) complex (Ph 3 P) 2 Pt(C 2 H 4 ) to form the cyclo-MSN 2 C 2 (CN) 2 ring compound (II=). 31 Oxidative addition also predominates for metal complexes of 1,2,3,5-dithiadiazoyl (DTDA) radicals, RCN 2 S 2 , 30,32 although this class of thiazyl radicals affords a greater variety of adduct geometries, including metallacycles akin to II= that retain paramagnetism as well as larger clusters that are found both as diamagnetic and paramagnetic species (representative structures are shown as (A)-(E) in Chart 2 of ref. 33).…”