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The crystalline ate complex Me4FeLi,(Et20)2 (1 d) described in the literature as well as the complexes MeFeCl (la), Me,Fe (lb), Me,FeLi (lc), nBu,Fe (2a), nBu,FeLi, (2b), nOct,Fe (3a), nOct,FeLi (3b), and nOct4FeLi2 (3c) are prepared in situ by transmetallation of MeLi, nBuLi, and nOctLi with FeCl, (readily available by in situ reduction of FeC1, with MeLi). All these complexes have been subjected to reaction with organic substrates for the first time. Evidence for this transmetallation has been furnished by a novel test (referred to as "P-bromostyreneketone test"). In this test, involving addition of P-bromostyrene (4) and 4-methylpentan-2-one (5), the alkyllithium compounds alkylate selectively only the ketone and the alkyliron compounds almost exclusively the P-bromostyrene. The high preference of the alkyliron reagents for the alkylation of the Pbromostyryl residue has been utilized for regioselective butylations and octylations of 1-{4-[(Z)-2-bromoethenyl]phenyl}-ethanone (6). Moreover, in competition reactions with benzaldehyde/4-methylpentan-2-one the alkyliron reagents have been found to react usually specifically with aldehydes. The decomposition temperatures of the reagents 1 a, b, c and 2 b in THF have been determined to be 0, -10, 25, and -2O"C, respectively.Das Collman-Reagenz (COkFeNaz und sein Halbsandwich-Analogon C5H5 (C0)

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The methyliron reagents (III) are added to mixtures of the bromostyrene (I) and the ketone (II) to yield predominantly the methylation product (IV) of (I).