Alkali Metal-Mediated Schlenk Dimerization of a Phosphorus-Substituted Alkene. Synthesis and Crystal Structures of Li, Na, and K Derivatives of a Phosphorus-Stabilized Butane-1,4-diide Ligand

Abstract

Treatment of the vinylidene phosphine (Ph2P)2CCH2 (1) with either Li or Na in THF yields the bis(diphosphinomethanide) complexes {(THF)2Li(Ph2P)2CCH2}2 (2), {(pmdeta)2Li(Ph2P)2CCH2}2·(PhMe)3 (6), and [{(tmeda)1.5Na(Ph2P)2CCH2}2] n (3b), after recrystallization [tmeda = N,N,N‘,N‘-tetramethylethylenediamine, pmdeta = N,N,N‘,N ‘ ‘,N ‘ ‘-pentamethyldiethylenetriamine]. Treatment of 1 with K under the same conditions results in ligand degradation to give K(PPh2), which was isolated as the adduct {(pmdeta)K(PPh2)} n (4) after recrystallization from toluene/pmdeta, and unidentified organopotassium products. The potassium bis(diphosphinomethanide) [{(Ph2P)2CCH2CH2C(PPh2)2}2K4(pmdeta)(DME)3·(PhMe)2] n (5) may be accessed via a metathesis reaction between 2 and KO-t-Bu in ether, followed by recrystallization from toluene/DME in the presence of pmdeta [DME = 1,2-dimethoxyethane]. Compounds 3b, 4, 5, and 6 have been characterized by multielement NMR spectroscopy and X-ray crystallography.

Syntheses and Structures of Potassium Complexes Containing Bis(diphenylphosphanyl)methanide Anions

“…[23] 3.399 Å), whereas potassium phosphorus bonds related to the κ 3 PCP heteroallyl interaction are shortened to an average value of 3.577 Å (ref. [23] 3.837 Å).…”

“…[23] 3.399 Å), whereas potassium phosphorus bonds related to the κ 3 PCP heteroallyl interaction are shortened to an average value of 3.577 Å (ref. [23] 3.837 Å). The coordinated dimethoxyethane acts as a chelating ligand with bond lengths of 2.6623(11) (O1-K1) and 2.8587(11) Å (O2-K1).…”

“…[{(Ph 2 P) 2 CCH 2 CH 2 C(PPh 2 ) 2 } 2 K 4 (pmdta)(dme) 3 ] n · (PhMe) 2n [23] (pmdta = N,N,NЈ,NЈ,NЈЈ-pentamethyldiethylenetriamine) containing four structurally independent potassium ions, all of them in distinct environments relative to the diphosphanylmethanide ligand. The observed flexibility of the interaction between potassium and diphosphanylmethanide ligand prompted us to investigate the system [(R 2 P) 2 …”

“…In the case of the rather small s-block metal cations lithium, [14][15][16][17][18][19][20][21] sodium, [22,23] magnesium [24] and calcium, [19,24] this class of ligands prefers coordination through the phosphorus atoms in the presence of adequate amounts of neutral donor ligands. However, in the case of lithium, the absence of an excess of appropriate neutral donor ligands such as tetrahydrofuran (THF) leads to occupation of vacant coordination sites by the methanide carbon atom, as observed for instance in dinuclear [(thf)Li{(Ph 2 P) 2 CH}] 2 and related complexes.…”

Phosphanylborohydrides: First Assessment of the Relative Lewis Basicities of [BH3PPh2]–, CH3PPh2, and HPPh2

“…[16] The phosphonium iodide salts [H 2 PPh 2 ]I (6) and [CH 3 (H)PPh 2 ]I (7) were -fragment coordinates to two potassium counterions with bond lengths P(1)-K(1) and P(1)-K(1A) of 3.347(1) Å and 3.267(1) Å, respectively (sum of the ionic radius of K + and the van-der-Waals radius of phosphorus: 3.55 Å [19] ). Each potassium centre is encapsulated by one crown ether ligand; in addition, a relatively short intermolecular contact is established between K(1A) and one phenyl ring [K(1A)··· C(25A) = 3.518 (2) [20] and the 1,4-dioxane complex {K(dioxane) 2 [PPh 2 ]} n . [21] Most notably, Eaborn, Smith …”