The tmbp Dianion in the Contact Ion Pair [(tmbp)Na_2(dme)_(1.5)[_n and in the Solvent-Separated Ion Pair [tmbp][(2.2.1)Li]_2

摘要

Multiple reductions of unsaturated #pi# systems generally provide important information on delocalization processes. Furthermore they often yield fascinating structures that illustrate aggregation and solvation phenomena of cations, and constitute good models for the modification of solid surfaces by adsorption of alkali metals, whereas reduction processes of unsaturated carbon and nitrogen derivatives are now well documented, that of sp~2-hybriidized phosphorus-based molecules and their related transition metal complexes constitute a new field. Recently, we have shown that 2,2'-biphosphinine dianions could be used efficiently to synthesize highly reduced transitions metal complexes through their reactions with various metal precursors; herein we shed some light on their very peculiar geometrical and electronic structures. The twofold reduction of 4,4',5,5'-tetramethyl-2,2'-biphosphinie (1; tmbp) was studied in THF and dimethoxyethane at room temperature with lithium naphthalene or sodium naphthalene with and without crypt-ands. From dimethoxyethane (DME), a polymeric structure of general formula [(tmbp)Na_2(dme)_(1.5)]_n (2) crystallized, whereas reaction with lithium in THF in the presence of cryptand (2.2.1) yielded the monomeric complex [(tmbp)][Li(2.2.1)]_2 (3; Scheme 1).