SYNTHESIS AND REACTIONS AT CO-CH2 AND C=C BONDS OF COBALT-PROPARGYL COMPLEXES

The first cobalt-propargyl complexes RCCCH2Co(CO)3PPh3 (1: R = Me (a), Ph (b), CH2Cl (c)) were prepared by reaction of NaCo(CO)3PPh3 with RCCCH2X (X = Cl or Br) in THF at ca. -20°C. Also synthesized, by treatment of NaCo(CO)4 in diethyl ether under CO at -20 to 0°C with one equivalent of each PPh3 and RCCCH2X in that order, were the first examples of metal acylpropargyl complexes, RCCCH2C(O)Co(CO)3PPh3 (2). Both 1 and 2 were characterized by elemental analysis and IR and NMR (1H, 13C{1H}, and 31P{1H}) spectroscopy and shown to adopt C3v structures. 1a,1b undergo carbonylation to 2a,2b in THF or CH2Cl2 solution at 0°C under 1 atm of CO; the reverse reaction occurs at room temperature when Ar is passed into solutions of 2a,2b in THF. The carbonylation reactions represent the first examples of insertion of CO into a propargyl carbon-to-metal linkage. 1a,1b undergo [3 + 2] cycloaddition reactions with (CN)2CC(CN)2 and SO2 to afford CH2C(CN)2C(CN)2C(R)CCo(CO)3PPh3 (3a,3b) and CH2OS(O)C(Me)CCo(CO)3PPh3 (4a), respectively. © 1990.