Jonathan D. Tedder

Formation of N,N-Dimethylacrylamide by a Multicenter Hydrocarbamoylation of C2H2 with N,N-Dimethylformamide Activated by Ru5(μ5-C)(CO)15

Hydrocarbamoylation of C2H2 by N, N-dimethylformamide (DMF) to N, N-dimethylacrylamide was effected by a series of cluster-opening reactions with Ru5(μ5-C)(CO)15 (1). The reaction of 1 with DMF yielded the new complexes Ru5(μ5-C)(CO)14(μ-η2-O═CNMe2)(μ-H) (2) and a minor coproduct Ru5(μ5-C)(CO)13(HNMe2)(μ-η2-O═CNMe2)(μ-H) (3) by a cluster-opening activation of the formyl C-H bond of DMF. Compound 3 was obtained from 2 by a further reaction with DMF. Compound 3 reacted with C2H2 (1 atm, 70 °C) to yield Ru5(μ5-C)(CO)13(μ-η3-O═CNMe2CHCH)(μ-H) (4) by the addition and coupling of C2H2 to the bridging dimethylformamido ligand. Compound 4 contains a σ-π-coordinated, dimethylformamido-substituted vinyl ligand that bridges a Ru-Ru edge of an open Ru5C cluster. The formamido group is also coordinated to one of the metal atoms. The addition of CO (1 atm, 25 °C) to 4 yielded the CO adduct Ru5(μ5-C)(CO)14(η2-O═CNMe2CH═CH)(μ-H) (5) containing a chelating dimethylacrylamido ligand, which released dimethylacrylamide by the reductive elimination of a C-H bond upon a further addition of CO (400 psi, 125 °C) with the re-formation of 1. All of the products were characterized by single-crystal X-ray diffraction analyses.

Multiple C–H Bond Activations and Ring-Opening C–S Bond Cleavage of Thiophene by Dirhenium Carbonyl Complexes

The reaction of Re2(CO)8(μ-C6H5)(μ-H) (1) with thiophene in CH2Cl2 at 40 °C yielded the new compound Re2(CO)8(μ-η2-SC4H3)(μ-H) (2), which contains a bridging σ-π-coordinated thienyl ligand formed by the activation of the C-H bond at the 2 position of the thiophene. Compound 2 exhibits dynamical activity on the NMR time scale involving rearrangements of the bridging thienyl ligand. The reaction of compound 2 with a second 1 equiv of 1 at 45 °C yielded the doubly metalated product [Re2(CO)8(μ-H)]2(μ-η2-2,3-μ-η2-4,5-C4H2S) (3), formed by the activation of the C-H bond at the 5 position of the thienyl ligand in 2. Heating 3 in a hexane solvent to reflux transformed it into the ring-opened compound Re(CO)4[μ-η5-η2-SCC(H)C(H)C(H)][Re(CO)3][Re2(CO)8(μ-H)] (4) by the loss of one CO ligand. Compound 4 contains a doubly metalated 1-thiapentadienyl ligand formed by the cleavage of one of the C-S bonds. When heated to reflux (125 °C) in an octane solvent in the presence of H2O, the new compound Re(CO)4[η5-μ-η2-SC(H)C(H)C(H)C(H)]Re(CO)3 (5) was obtained by cleavage of the Re2(CO)8(μ-H) group from 4 with formation of the known coproduct [Re(CO)3(μ3-OH)]4. All new products were characterized by single-crystal X-ray diffraction analyses.