SYNTHESIS AND STRUCTURES OF THE CUBOIDAL IRON-SULFUR-NITROSYL-PHOSPHINE CLUSTERS [FE4S3(NO)(4)(PR3)(3)](0,1-I, C6H11)() (R = ET, PR)

A series of cuboidal iron-sulfur clusters [Fe4S3(NO)(4)(PR3)(3)](0,1+) (R = Et, Pr-i, Cy) were synthesized by two routes: reductive desulfur ization of [Fe4S4(NO)(4)] by tertiary phosphines, and substitution of triphenylphosphine in [Fe4S3(NO)(4)(PPh3)(3)] by a more basic phosphin e. The structures of 3[Fe4S3(NO)(4)(PEt3)(3)]. 0.5Et(2)O, [Fe4S3(NO)(4 )(PEt3)(3)][Fe4S3(NO)(7)] and partially substituted [Fe4S3(NO)(4)(PPh3 )(2)-(PPr3i)] have been determined by X-ray diffraction in order to de fine the cuboidal Fe4S3 core, previously known only in Roussin's black anion and its reduced form, [Fe4S3(NO)(7)](1-2-), and as a part of th e iron-molybdenum cofactor of nitrogenase. (C) 1998 Elsevier Science S .A.