172537-89-2Relevant academic research and scientific papers
Prepaparion, Properties, and Reactions of Metal-Containing Heterocycles, XCI. Insertion of Activated Alkynes and Sulfur into the P-P Bond of Diphosphamolybdacyclopropanes
Lindner, Ekkehard,Kneissle, Wilfried,Fawzi, Riad,Steimann, Manfred,Mayer, A. Hermann,Gierling, Karlheinz
, p. 973 - 982 (2007/10/03)
The insertion of alkynes ZCCZ (2a-i) a), Et (b), (nPR (c), iPr (d), nBu (e), tBu (f), neo-Pent (g), cyc-Hex (h); Z = CF3 (i)> into the P1-P2 bond of the diphosphamolybdacyclopropane (1) (Mes = 2,4,6-trimethylphenyl) results in the formation of the diphosphamolybdacyclopentenes (3a-i).According to an X-ray structural analysis, 3a crystallizes in the space group P21/c with the mesityl function at P2 and the cyclopentadienyl fragment at the metal atom on the opposite side of the planar five-membered ring.The same orientation is found in solution by NMR experiments (NOE; 2D 1H, 13C HECTOR).Kinetic investigations confirm that the rate constants decrease in the sequence R = Me > Et > nPr > isoProp > Cy > nBu > neoPent > tBu.The second-order reaction and the strongly negative activation entropy which was determined in the case of the reaction 1 + 2e -> 3e are consistent with a nucleophilic attack of P2 at one of the triply bonded carbon atoms of the alkyne.The reaction of 3a, h with sulfur affords the diastereomeric compounds (4a,h).An X-ray structural analysis of the heterocycle 4h, which crystallizes in the space group , shows the presence of the enantiomeric pair SR/RS.The reaction of 1 with alkynes is hindered if this heterocycle is oxidized by sulfur to give (5).Further reaction of 5 with sulfur leads to the ring-expanded heterocyclic intermediate (6) which crystallizes in the space group .The five-membered ring in 6 has an envelope conformation.Upon thermally induced cleavage of the P2S2Mes fragment from 6 the three-membered ring (7) is formed as the final product. - Keywords: Molybdenum heterocycles / P-P bonds / Activated alkynes / Sulfur / Insertion reactions
