FORMATION OF (TRIPHENYLPHOSPHINE)(ETHYLENE)-PENTAMETHYLCYCLOPENTADIENYLRHODIUM(I) IN THE REACTION OF DIIODO(TRIPHENYLPHOSPHINE)PENTAMETHYLCYCLOPENTA-DIENYLRHODIUM(III) WITH BUTANE-1,4-BIS-(MAGNESIUM BROMIDE) - EXAMPLE OF FACILE C-O CLEAVAGE OF DIETHYL-ETHER BY AN ORGANOMAGNESIUM COMPOUNDP

A study is described of the reaction between [RhI2(PPh3)(η5-C5Me5)] (I) and the alkylating reagents, BrMg(CH2)4MgBr (II) or Mg(CH2)4, in diethyl ether, which gives a mixture of the ethylenerhodium complex of formula [Rh(C2H4)(PPh3)(η5-C5Me5)] (III) and the rhodacyclopentane derivative, [Rh(CH2)4(PPh3)(η5-C5Me5)] (IV). In tetrahydrofuran these reactions give only IV. Pure IV is also obtained by treating [RhCl2(PPh3)(η5-C5Me5)] or I with 1,4-dilithiobutane. By use of deuterium-labelled alkylating reagents it has been shown that the formation of the ethylenerhodium complex IV is due to a facile diethyl ether CO cleavage by organomagnesium compounds. The mechanism of the formation of III is briefly discussed. © 1979.