New Lithium Phosphonium Diylides: A Methylene and a Cyclopentadienyl Moiety as Ylidic Coordination Sites

Synthesis of a lithium–cyclopentadienide complex by addition of LiNTf2 to a zwitterionic fulvalene

LiNTf₂ adds to a zwitterionic fulvalene yielding a η⁵-CpLi complex that is in equilibrium with its lithiocene at −80 °C as revealed by ⁷Li NMR spectroscopy.

Ferrocenylmethylation reactions with a phosphinoferrocene betaine

A phosphinoferrocene betaine, N-{[1'-(diphenylphosphino)ferrocenyl]methyl}-N,N-dimethyl-3-sulfo-1-propanaminium, inner salt, Ph2PfcCH2NMe2(CH2)3SO3 (; fc = ferrocene-1,1'-diyl), was prepared by alkylation of Ph2PfcCH2NMe2 () with 1,3-propanesultone, and was studied as a ferrocenylmethylation agent. The treatment of with NaOH in hot water-dimethyl sulfoxide produced phosphinoalcohol Ph2PfcCH2OH () in a 64% yield, whereas a similar reaction with MeONa in dimethylsulfoxide-methanol furnished the corresponding ether, Ph2PfcCH2OMe (), in a 47% yield. In subsequent experiments, betaine was employed in the synthesis of phosphinoferrocene sulfones, Ph2PfcCH2SO2R, where R = Me (), Ph (), and 4-tolyl (). Compounds and some by-products of the ferrocenylmethylation reactions, namely alcohol , 1'-(diphenylphosphino)-1-methylferrocene (), and 1-{[diphenyl(2,4-cyclopentadien-1-ylidene)phosphoranyl]methyl}-1'-(diphenylphosphino)ferrocene () structurally characterised. Reactions of as the representative with ZnX2/NaX (X = Br and I) afforded unique coordination polymers [ZnNaX3()(CH3OH)]n featuring tetrahedral Zn(ii) and octahedral Na(i) centres bridged by halide ions, solvating methanol and the sulfone ligands. The reaction of with ZnBr2/KBr produced an analogous product, [ZnKBr3()(CH3OH)]n, while that with ZnBr2/LiBr furnished a different, pseudodimeric complex [Zn2Li2Br6()2(CH3OH)4(H2O)]·CH3OH, featuring tetrahedrally coordinated Zn(ii) and Li(i) centres bridged by . Reactions of 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.

Ferrocenyl-phosphonium ionic liquids - synthesis, characterisation and electrochemistry

New unsymmetrically substituted ferrocenyl-phosphonium ionic liquids (ILs) [FcPR2R']NTf2 are synthesized by two or three step syntheses starting from ferrocene, Fc = (C5H5)Fe(C5H4); R = Me, (n)Bu, (n)Hex, Ph; R' = Me, (n)Pr, (n)Bu, Ph; NTf2 = N(SO2CF3)2. The selective synthesis of alkyl phosphines FcPR2via a Friedel-Crafts phosphorylation is highlighted as an alternative for the standard protocol commonly used for ferrocenyl arylphosphines involving lithiation of FcH followed by phosphorylation. The influence of the P-substituents on thermal stability, electrochemical potential, chemical shift, and UV-Vis absorption behavior of the ILs is studied. The phosphonium group acts both as an ionic tag and as an electron-withdrawing substituent directly bound at the Cp-ring position. Therefore the title compounds are attractive for further studies to use them as tunable redox mediators for (photo)electrochemical devices such as dye sensitized solar cells (DSSCs) or redox flow batteries.