The crystal structure determinations of MnRe(C0)9(CNBut) (l), MnRe(CO)9P(CH2CaH5)3 (2), and MnRe-(C0)8(CNBut)(PPh3) (3) have been performed. Crystaldata: (1) monoclinic, P21/n, a = 12.030 (7) A, b = 20.834 (8) A, c = 15.22 (1) A, @ = 91.683 (a)', Z = 8, and R = 0.075; (2) triclinic, Pi, a = 12.314 (7) A, b = 14.305 (7) A, c = 19.198 (6) A, a = 68.40 ( 5 ) O , @ = 78.390 (4)O, y = 88.98 (4)O, Z = 4, and R = 0.050; (3) monoclinic, P2l/c, a = 17.841 (3) A, b = 9.616 (2) A, c = 20.505 (4) A, @ = 113.15 (l)', Z = 4, and R = 0.037. In all three structures dMn-Rc is found to be 2.963 (f7) A, suggesting that the site and degree of substitution on MnRe(CO)lo have little influence on the bond length value. The value lies midway between the metal-metal bond lengths of Mn2(CO)lo (dMn-Mn = 2.904 (1) A) and Rez(CO)lo (dRtRe = 3.041 (1) A). (10) Ingham, W. L.; Travlos, S. D.; Boeyens, J. C. A.; Berry, M.; Coville, N. J. Acta Crystallogr., Sect. C 1992, C48, 465. See references cited therein. (1 1) Kokkes,M. W.;Snoeck,T. L.;Stufkens,D. J.;Oskam,A.;Cristophersen, M.; Stam, C. H.