New inorganic ring system: planar Fe/sub 3/(. mu. /sub 2/-SR)/sub 3/ in (Fe/sub 3/(SR)/sub 3/X/sub 6/)/sup 3 -/ - synthesis, structures, and solution conformation and equilibrium

Anaerobic reaction of equimolar FeX/sub 2/ and RS/sup -/ in acetonitrile affords the trinuclear complexes (Fe/sub 3/(SR)/sub 3/X/sub 6/)/sup 3 -/ (with X = Cl and R = Ph (4a), p-tolyl (4b), 2,6-Me/sub 2/C/sub 6/H/sub 3/ (4d), and X = Br, R = Ph (4c)) isolated as Et/sub 4/N/sup +/ salts. These species constitute the fourth known type of discrete Fe(II) thiolates, the others being (Fe(SR)/sub 4/)/sup 2 -/, (Fe/sub 2/(SR)/sub 6/)/sup 2 -/, and (Fe/sub 4/(SR)/sub 10/)/sup 2 -/. The following crystallographic results were obtained (crystal system; space group; cell parameters; Z; unique data (I > 3sigma(I)); R (%)). (Et/sub 4/N)/sub 3/ (4a): monoclinic; C2/c; a = 24.500 (6) A, b = 13.488 (3) A, c = 18.217 (5) A, ..beta.. = 110.68 (2)/sup 0/; 4; 2679; 4.9. (Et/sub 4/N)/sub 3/ (4d) x 3MeCN: monoclinic: P2/sub 1//n; a = 15.07 (1) A, b = 22.38 (3) A, c = 20.46 (3) A, ..beta.. = 91.5 (1)/sup 0/; 4, 3311; 9.7. (Et/sub 4/N)/sub 3/ (4c) x MeCN: hexagonal, P/sup -/62c; a = b = 13.970 (4) A, c = 18.274 (3) A; 2; 890; 5.7. The reaction system FeBr/sub 2/ + NaSCH/sub 2/Ph in acetonitrile yields a different type ofmore » compound with the composition (Et/sub 4/N)/sub 2/(Fe/sub 4/(SCH/sub 2/Ph)/sub 6/Br/sub 4/) (5): triclinic; P/sup -/1; a = 12.874 (2) A, b = 13.949 (3) A, c = 43.272 (8) A, ..cap alpha.. = 94.85 (2)/sup 0/, ..beta.. = 94.07 (2)/sup 0/, ..gamma.. = 114.98 (1)/sup 0/; 4; 7402; 6.7. Anions of type 4 contain a new type of inorganic ring system, Fe/sub 3/(..mu..-SR)/sub 3/, distinguished by its nearly or exactly planar conformation and unusually large Fe-S-Fe angles of approx. 140/sup 0/, the largest values observed for this angle type.« less