In:
Canadian Journal of Chemistry, Canadian Science Publishing, Vol. 73, No. 9 ( 1995-09-01), p. 1444-1453
Abstract:
The title compounds have been studied in CH 2 Cl 2 by cyclic voltammetry. Nonacarbonyldi(μ 3 -methylidyne)triiron, [Fe 3 (CO) 9 (μ 3 -CX) 2 ] (X = F, Cl, Br, H), undergo chemically reversible 1e − reduction (−0.72 to −0.88 V vs. SCE) and irreversible oxidation (+1.59 to +1.72 V); the compound for which X = F displays a second, irreversible reduction (−1.96 V). Using reduction potentials of comparable μ 3 -E (E = S, Se, NPh, PPh) clusters, μ 3 -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 [Fe 3 (CO) 9 (C 2 R 2 )], indicative of greater thermodynamic stability. The complexes previously formulated as [Fe 2 (CO) 6 (S 2 N 2 CC 6 H 4 X)] (X = H, CF 3 , OCH 3 ) 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 2 (CO) 6 (S 2 N{NH}CC 6 H 4 X)] (ν NH = 3376−3381 cm −1 ;δ NH = 6.55−7.1 ppm). Dicyclopentadienyl-dithiadiazoledinickel, [Ni 2 Cp 2 (S 2 N 2 CC 6 H 5 )], 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 = 2.0410, no resolved hyperfine splitting). Extended Hückel theory locates the free electron in a SOMO restricted to Ni, C, and S atoms. Keywords: electrochemistry, organometallic, methylidyne, dithiadiazole, dithiadiazoline.
Type of Medium:
Online Resource
ISSN:
0008-4042
,
1480-3291
Language:
English
Publisher:
Canadian Science Publishing
Publication Date:
1995
detail.hit.zdb_id:
1482256-8
