A reaction system consisting of FeCl2, NaSC6H11, (NH4)(2)MoS4, and Et4NBF4 in methanol affords a novel Mo-Fe-S cluster [Et4N](2)[MoFe4S4(SC6H11)(7)]. 1/2CH(3)CN (1). The compound crystallizes in the monoclinic space group C-2/c, a = 50.762(5) Angstrom, b = 12.230(1) Angstrom, c = 33.228(4) Angstrom, beta = 130.428(10)degrees, V = 15703(3) Angstrom(3), and Z = 8. The structure of the anion is composed of a single MoFe3S4 cubane unit and a Fe(SC6H11)(4) subunit. All the four Fe atoms are tetrahedrally coordinated, and the Mo atom is octahedrally coordinated. The metal formal oxidation levels were deduced as 2Fe((III)) + 2Fe((II)) + Mo-(III) by structural parameters and Mossbauer effect. The effective magnetic moment of the cluster diminishes smoothly with the decreasing of temperature in the range 1.5-300 K showing an antiferromagnetic spin-exchange interaction operating in the cluster.