Preprint Article Version 1 NOT YET PEER-REVIEWED

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

  1. Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University, Humboldtstrasse 8, 07743 Jena, Germany
Version 1 : Received: 1 November 2016 / Approved: 2 November 2016 / Online: 2 November 2016 (06:47:28 CET)

A peer-reviewed article of this Preprint also exists.

Koch, A.; Krieck, S.; Görls, H.; Westerhausen, M. Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium. Inorganics 2016, 4, 39. Koch, A.; Krieck, S.; Görls, H.; Westerhausen, M. Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium. Inorganics 2016, 4, 39.

Journal reference: Inorganics 2016, 4, 39
DOI: 10.3390/inorganics4040039

Abstract

Arylmagnesium and -calcium reagents are easily accessible, however, ether degradation processes limit the storability especially of the calcium-based heavy Grignard reagents. Ortho-bound substituents with phosphanyl donor sites usually block available coordination sites and stabilize such complexes. The reaction of bromo-2,6-bis(diphenylphosphanylmethyl)benzene (1a) with magnesium in tetrahydrofuran yields [Mg{C6H3-2,6-(CH2PPh2)2}2] (2) after recrystallization from 1,2-dimethoxyethane. However, the similarly performed reduction of bromo- (1a) and iodo-2,6-bis(diphenylphosphanylmethyl)benzene (1b) with calcium leads to ether cleavage and subsequent degradation products. α-Deprotonation of THF yields 1,3-bis(diphenylphosphanylmethyl)benzene. Furthermore, the insoluble THF adducts of dimeric calcium diphenylphosphinate halides, [(thf)3Ca(X)(µ-O2PPh2)]2 [X = Br (3a), I (3b)], precipitate verifying ether decomposition and cleavage of P-C bonds. Ether adducts of calcium halides [such as [(dme)2(thf)CaBr2] (4)] form supporting the initial Grignard reaction and a subsequent Schlenk-type dismutation reaction.

Subject Areas

Grignard reagent; arylmagnesium halide; phosphinates; calcium phosphinates; direct synthesis; ether degradation; calcium bromide

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