Ferrocenylmethylation reactions with a phosphinoferrocene betaine?

Dalton Transactions Pub Date: 2015-07-08 DOI: 10.1039/C5DT01877C

Abstract

A phosphinoferrocene betaine, N-{[1′-(diphenylphosphino)ferrocenyl]methyl}-N,N-dimethyl-3-sulfo-1-propanaminium, inner salt, Ph2PfcCH2NMe2(CH2)3SO3 (2; fc = ferrocene-1,1′-diyl), was prepared by alkylation of Ph2PfcCH2NMe2 (1) with 1,3-propanesultone, and was studied as a ferrocenylmethylation agent. The treatment of 2 with NaOH in hot water–dimethyl sulfoxide produced phosphinoalcohol Ph2PfcCH2OH (3) in a 64% yield, whereas a similar reaction with MeONa in dimethylsulfoxide–methanol furnished the corresponding ether, Ph2PfcCH2OMe (4), in a 47% yield. In subsequent experiments, betaine 2 was employed in the synthesis of phosphinoferrocene sulfones, Ph2PfcCH2SO2R, where R = Me (6a), Ph (6b), and 4-tolyl (6c). Compounds 6a–c and some by-products of the ferrocenylmethylation reactions, namely alcohol 3, 1′-(diphenylphosphino)-1-methylferrocene (5), and 1-{[diphenyl(2,4-cyclopentadien-1-ylidene)phosphoranyl]methyl}-1′-(diphenylphosphino)ferrocene (7) structurally characterised. Reactions of 6a as the representative with ZnX2/NaX (X = Br and I) afforded unique coordination polymers [ZnNaX3(6a)(CH3OH)]n featuring tetrahedral Zn(II) and octahedral Na(I) centres bridged by halide ions, solvating methanol and the sulfone ligands. The reaction of 6a with ZnBr2/KBr produced an analogous product, [ZnKBr3(6a)(CH3OH)]n, while that with ZnBr2/LiBr furnished a different, pseudodimeric complex [Zn2Li2Br6(6a)2(CH3OH)4(H2O)]·CH3OH, featuring tetrahedrally coordinated Zn(II) and Li(I) centres bridged by 6a. Reactions of 6a with ZnBr2/MBr (M = Rb, Cs) and NaCl/ZnCl2 did not yield similar products because of an easy precipitation (low solubility) of the respective alkali metal halides.

Graphical abstract: Ferrocenylmethylation reactions with a phosphinoferrocene betaine
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