AN UNUSUAL TRANSITION-METAL CLUSTER CONTAINING A 7-METAL ATOM PLANE - SYNTHESES AND CRYSTAL-STRUCTURES OF [MN][MN-7(THF)(6)(CO)(12)](2), MN-3(THF)(2)(CO)(10), AND [MN(THF)(6)][MN(CO)(5)](2)

Dimanganese decacarbonyl reacts with trimethylaluminum in a mixture of hexane and tetrahydrofuran to produce [Mn][Mn-7(THF)(6)(CO)(12)](2) (1; THF = tetrahydrofuran) and the unstable compounds Mn-3(THF)(2)(CO)(10) (2) and [Mn(THF)(6)][Mn(CO)(5)](2) (3). The crystal structure of 1 is made up of two Mn-7(THF)(6)(CO)(12)(-) anions, each of which is coordinated to an isolated Mn2+ cation via three carbonyl oxygens to give an octahedral coordination geometry about the cation, The framework of each Mn-7(THF)(6)(CO)(12)(-) anion consists of a ring of six manganese atoms, all of which are attached to a seventh manganese in the center of the ring to form a planar Mn-7 unit. The six-membered ring is made up of alternating Mn(CO)(4) and Mn(THF)(2) groups, and if metal-metal bonds to the central manganese are ignored, the former have approximate octahedral coordination while the latter have somewhat distorted tetrahedral geometries. The complex crystallizes in two forms, one form that contains two molecules per formula unit of the tetrahydrofuran adduct of trimethylaluminum, and another form in which the trimethylaluminum adduct is absent. Crystal data for [Mn][Mn-7(THF)(6)(CO)(12)](2) . 2Al(CH3)(3)THF: monoclinic space group P2(1)/c (No. 14), a = 13.630(3) Angstrom, b = 24.847(5) Angstrom, c = 17.645(4) Angstrom, beta = 106.01(3)degrees, Z = 2, R = 6.56%, R(w) 6.75%. Crystal data for [Mn][Mn-7(THF)(6)(CO)(12)]2: monoclinic space group P2(1)/c (No. 14), a = 18.268(2) Angstrom, b = 20.395(4) Angstrom, c = 15.143(2) Angstrom, beta = 103.064(8)degrees, Z = 2, R = 8.75%, R(w) = 9.55%. The structure of 2 consists of two Mn(CO)(5) groups connected by metal-metal bonds to a central Mn(THF)(2) unit, and 3 consists of isolated [Mn(THF)(6)](2+) and [Mn(CD)(5)](-) ions. Crystal data for Mn-3(THF)(2)(CO)(10)(2): monoclinic space group P2(1)/n (No. 14), a = 8.9394(7) 16.038(2) Angstrom, beta = 95.239(8)degrees, Z = 4, R = 4.26%, R(w) = 3.85%. Crystal data for [Mn(THF)(6)][Mn(CO)(5)](2) (3): triclinic space group P ($) over bar 1 (No. 2), a = 10.352(1) Angstrom, b = 10.443(1) Angstrom, c = 19.552(3) Angstrom, a = 83.86(1)degrees, beta = 88.14(1)degrees, gamma = 86.037(9)degrees, Z = 2, R = 6.57%, R(w) = 9.07%.