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The complexes [Mo(η3-allyl)(CO)2(S2PX2)(NCMe)] (X = OEt (1a), Ph (1b)) react with DMAD (dimethyl acetylenedicarboxylate) to give the tricarbonyl complexes [Mo(CO)3(S2PX2){OC(OMe)C(allyl)CCO2Me}] (2a,b) in a reaction involving the coupling of allyl and alkyne. Subsequent addition of PEt3 affords crystalline, air-stable dicarbonyl complexes [Mo(CO)2(PEt3)(S2PX2){OC(OMe)C(allyl)CCO2Me}] (3a,b). An X-ray structural analysis of the dithiophosphinate derivative 3b reveals that the alkenyl ligand is stabilized through intramolecular coordination of one oxygen of the ester group to the metal, forming a five-membered oxametallacycle. The alkenyl ligand shows unusual trans stereochemistry in contrast to the cis disposition usually found in previous examples of metal-mediated η3-allyl−alkyne coupling. Demetalation of the organic moiety can be easily afforded by reaction with air or HCl gas to give the corresponding 2-allyl fumarate 4 in high yield. Regioselectivity studies employing 1-methylallyl complexes reveal that the reaction is strongly influenced by the dithio ligand bonded to molybdenum. In all cases reaction at the more substituted carbon of the allyl is favored.

Several heterobinuclear cyanide-bridged cationic complexes of the type [LnM,-CN-M,Ln]+, where LnMl and LnM2 are the fragments Fe(C5H5)(dppe) or cis-or rrans-Mn(CO)z(L-L)L [L-L = dppm, dppe; L = P(OPh),, PEt3; dppe = Ph2P(CH2CHz)PPh2; dppm = Ph,P(CH2)PPhJ, have been prepared as hexafluorophosphate salts by reacting the appropriate mononuclear complexes LnM,-CN and X-MzLn (X = Br, I) in the presence of TIPF6 or (NH4)PF6 as halogen abstractors. The oxidation of these compounds have been studied electrochemically by cyclic voltammetry and chemically by infrared spectroscopy. The results indicated that the first oxidation of the cations affects the Fe or Mn fragment depending on its position relative to the cyanide bridge and the stereochemistry (cis or trans) of the dicarbonyl fragments. When the oxidation affects a cis-Mn(CO),(L-L)L moiety, a very rapid isomerization to the trans form is observed and, in the case of the cis-dicarbonyl complexes [(C5H,)(dppe)Fe-CNMn(CO),(L-L)L]', the first oxidation takes place at Fe but is followed by electron transfer to Mn with concomitant isomerization to the irons-dicarbonyl form.

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