REACTIONS OF MN2(CO)9(NCME) WITH ALKYNES CONTAINING ELECTRON-DONATING SUBSTITUENTS

The addition of the electron-rich alkynes, MeC=CX, X = NMe2 or OEt, to the dimanganese complex Mn2(CO)9(NCMe), 1, has yielded the vinylidene complexes Mn2(CO)8[mu-eta2-C=C(Me)C=O(X)], 2a, X = NMe2, and 2b, X = OEt, respectively, by an addition and a rearrangement of the alkyne that included a CO insertion step. Both products will also add 1 equiv of MeC=CNMe2 to form the complexes Mn2(CO)7[mu-eta2-CC(Me)C(NMe2)C(Me)C=O(X)], 3a, X = NMe2, and 3b, X = OEt, which contain a four-membered carbocyclic ring formed by the addition of the C-C triple bond across the C-C double bond of the vinylidene ligand. The carbocyclic ring in complex 3a was opened thermally at 80-degrees-C to yield the complex Mn2(CO)6[mu-eta5-(Me2N)CC(Me)CC(Me)C=O(NMe2)], 4, that contains a carbene center. It was also opened by treatment with acetic acid to yield the mononuclear metal complex Mn(CO)3[eta4-(Me2N)-CC(Me)C(H)C(Me)C=O(NMe2)], 5, by proton addition and the loss of a manganese carbonyl fragment. The fragment was not isolated, but when the acidification was carried out in the presence of PPh3, compound 5 and a coproduct, Mn(CO)3(PPh3)2(O2CMe), 6, were isolated. Compound 6 is slowly transformed into the known compound Mn(CO)2(PPh3)2(eta2-O2CMe), 7. Compounds 2a,b, 3a, 4, and 5 were characterized by single-crystal X-ray diffraction analyses. Crystal data for 2a: space group = P1BAR, a = 10.422(2) angstrom, b = 10.628(2) angstrom, c = 8.934(1) angstrom, alpha = 113.74(1)degrees, beta = 97.55(1)degrees, gamma = 93.27(1)degrees, Z = 2, 1931 reflections, R = 0.027. Crystal data for 2b: space group = P1BAR, a = 10.3802(8) angstrom, b = 11.852(2) angstrom, c = 7.217(1) angstrom, alpha = 91.29(1)degrees, beta = 91.16(1)degrees, gamma = 98.40(1)degrees, Z = 2, 2482 reflections, R = 0.027. Crystal data for 3a: space group = P2(1)/c, a = 11.976(2) angstrom, b = 10.092(2) angstrom, c = 18.429(3) angstrom, beta = 107.18(2)degrees, Z = 4, 2155 reflections, R = 0.027. Crystal data for 4: space group = P1BAR, a = 12.496(2) angstrom, b = 16.481(4) angstrom, c = 10.398(2) angstrom, alpha = 93.97(2)degrees, beta = 103.30(1)degrees, gamma = 95.53(2)degrees, Z = 4,4057 reflections, R = 0.043. Crystal data for 5: space group = P1BAR, a = 9.540(2) angstrom, b = 12.166(3) angstrom, c = 7.888(1) angstrom, alpha = 92.06(2)degrees, beta = 104.75(2)degrees, gamma = 111.11(2)degrees, Z = 2, 2035 reflections, R = 0.029.