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Improved Synthesis of 1,12-Dimethyl-(1,1) Ferrocenophane

IP.com Disclosure Number: IPCOM000048660D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Mueller-Westerhoff, UT: AUTHOR [+2]

Abstract

The title compound, 1,12-dimethyl-(1,1)ferrocenophane, formula 1, is one of two organo-metallic materials which have been shown to produce hydrogen from aqueous acidic media. It has previously been obtained from bis-(6-methyl-6-fulvenyl)ferrocene 2 by reduction with LiAlH(4), followed by reaction with FeCl(2). This procedure was described as giving 1 in "modest" yield. Our own experience confirms that in this way one can obtain 1 in yields rarely exceeding 5 percent. We now know that the reduction with LiAlH(4) is detrimental. Having previously synthesized the 1,1'-bis-(6-fulvenyl)ferrocene 3, we are now able to disclose an improved method for the synthesis of 1 using the fulvene 3.

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Improved Synthesis of 1,12-Dimethyl-(1,1) Ferrocenophane

The title compound, 1,12-dimethyl-(1,1)ferrocenophane, formula 1, is one of two organo-metallic materials which have been shown to produce hydrogen from aqueous acidic media. It has previously been obtained from bis-(6-methyl-6- fulvenyl)ferrocene 2 by reduction with LiAlH(4), followed by reaction with FeCl(2). This procedure was described as giving 1 in "modest" yield. Our own experience confirms that in this way one can obtain 1 in yields rarely exceeding 5 percent. We now know that the reduction with LiAlH(4) is detrimental. Having previously synthesized the 1,1'-bis-(6-fulvenyl)ferrocene 3, we are now able to disclose an improved method for the synthesis of 1 using the fulvene 3.

In the previously published procedure, the anion 4 was formed in the first reaction step. As a byproduct, AlH(3) is present in the reaction mixture, which, when the iron salt is added, will reduce the metal, leading to side reactions and decomposition. As a consequence, the yield of 1 is always low.

In our improved procedure, we add methyl lithium to the unsubstituted fulvene 3, a reaction which proceeds cleanly and rapidly in tetrahydrofurane (THF) solution. There are no byproducts to interfere with the subsequent addition of FeCl(2). We are therefore able to obtain 1 in yields consistently above 70 percent.

In our procedure as well as in the prior published one, a mixture of the two possible isomers of 1 is obtained. For most...