Synthesis and structures of the cuboidal iron-sulfur-nitrosyl-phosphine clusters [Fe4S3(NO)4(PR3)3]0,1+ (R = Et, Pri, C6H11)

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 desulfurization of [Fe4S4(NO)(4)] by tertiary phosphines, and substitution of triphenylphosphine in [Fe4S3(NO)(4)(PPh3)(3)] by a more basic phosphine. 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 define 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 the iron-molybdenum cofactor of nitrogenase. (C) 1998 Elsevier Science S.A.