Silyl group migration in a P-silylated phosphonium ylide derived from dppm — A combined experimental and theoretical study

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

“…It bears, however, close re-semblance to the P-silylated phosphonium ylide [Ph 2 PCHP(SiMe 3 )Ph 2 ]. [21] The latter expectedly shows differing distances of 1.747(3) and 1.693(2) Å between the methanide carbon atom and the adjacent phosphorus atoms, indicating an enhanced double bond character between the silicon-substituted phosphorus atom and the central carbon atom. In contrast, the matching distances of 1.736(4) (P1-C1) and 1.735(4) Å (P2-C1) in 2 indicate equal delocalization of the negative charge in the P-C-P fragment.…”

“…From its composition a hitherto unknown oligomeric or polymeric structure has to be assumed, in contrast to the known mononuclear lithium derivative [Li{(Ph 2 P) 2 CH}(Et 2 O) 2 ], [21] in which the diphosphanylmethanide ligand shows a κ 2 PP coordination mode. Uptake of the diethyl ether ligated potassium compound in tetrahydropyran (THP) and crystallization at -40°C resulted in formation of orange yellow crystals of the related thp ligated derivative [K{(Ph 2 P) 2 CH}(thp)] ϱ (1; Scheme 2).…”

“…Only three sharp signals were observed for the two diglyme ligands at δ = 3.12, 3.05 (CH 2 ) and 3.00 ppm (CH 3 ) in the 1 H NMR spectrum and at δ = 71.6, 70.0 (CH 2 ) and 58.6 ppm (CH 3 ) in the 13 C NMR spectrum, respectively. Whereas the signal of the P-CH-P unit is shifted to δ = 2.37 ppm in the 1 H NMR spectrum, the 13 [21] and might be an indication that this carbon atom at least partially contributes to metal binding in this fluxional complex.…”

“…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.…”

Activation of the CP bond in phosphanylphosphaalkenes (CP–P bond system) in the reaction with nucleophilic reagents: MeLi, nBuLi and tBuLi

“…Similar Li–P distances are found in the following: [(Dipp) 2 P]Li(THF) 3 , 2.482(3) Å; 38 iPrP{C 6 H 4 -2-CH(C 6 H 4 -2-CH 2 NMe 2 )NMe 2 }Li(THF) 2 , 2.509(6) Å; 39 t Bu(Ph)P–P(SiMe 3 )Li(THF) 3 , 2.518(17) Å; 40 and [(Et 2 O) 2 Li{(Ph 2 P) 2 CH}], 2.581(4) Å and 2.583(4) Å. 41 The 31 P{ 1 H} NMR spectrum conducted from the 1a* crystals revealed signals from six different phosphorus atoms: 29.07 ppm ( J PP = 247.7 Hz, J PP = 17.2 Hz), −44.57 ppm ( J PP = 73.4 Hz, J PP = 17.2 Hz), −67.56 ppm ( J PP = 247.7 Hz, J PP = 73.4 Hz), 29.45 ppm ( J PP = 239.3 Hz), −44.92 ppm ( J PP = 36.5 Hz) −82.62 ppm ( J PP = 239.3 Hz, J PP = 36.5 Hz) (see ESI, Fig. S13 and S14 † ).…”