Multidentate Phosphinoalkoxides:  Synthesis, Deprotonation, and Building Blocks in Polylithium Mixed-Anion Aggregates

Abstract

The bis((dimethylphosphino)methyl)-substituted alcohol (Me 2 PCH 2 ) 2 CHOH (1) was prepared from the respective bis(3,5-dimethylbenzyl)phosphonium dichloride by reductive elimination of mesitylene with lithium alanate in 56% yield. Deprotonation with nbutyllithium or elemental sodium gave the respective alkali metal alcoholates [(Me 2 PCH 2 ) 2 -CHOM] 6 (M ) Li (2), Na (3)). Both compounds have a core consisting of two stacked M 3 O 3 hexagons held together by short M-O bonds. In 2, in addition to three oxygen atoms, each lithium atom is coordinated by one phosphino group of an adjacent ligand in a distorted tetrahedral geometry (Li-P ) 2.60(1) Å). In 3 each sodium atom is coordinated by two phosphino groups from different ligands in addition to the oxygen atoms. The coordination geometry at the sodium atom is a distorted trigonal bipyramid (O 3 P 2 ), the two phosphine donors being in axial and equatorial positions, respectively (Na-P ) 3.083(2), 3.151(2) Å). The tris((dimethylphosphino)methyl)-substituted alcohol (Me 2 PCH 2 ) 3 COH (4) was synthesized from 1-chloro-2,3-epoxy-2-(chloromethyl)propane by reaction with 3 equiv of LiPMe 2 in 69% yield. Its crystal structure contains a O-H‚‚‚P hydrogen bond (O‚‚‚P ) 3.460(1) Å). Reaction of 4 with excess n-butyllithium in the absence of solvent gave the dimeric polylithium mixed-anion aggregate [(Me 2 PCH 2 ) 3 COLi‚2Li-n-Bu] 2 (5), the core of which consists of two stacked LiOLiCLiC hexagons. Each (Me 2 PCH 2 ) 3 COanion is coordinated to three Li + cations via O-Li and P-Li bonds. The same reaction in toluene led to further deprotonation of the methylene groups in 4, subsequent loss of Li 2 O, and formation of the symmetrically tris(phosphino)-substituted trimethylenemethane dianion. It crystallizes as the mixed-anion aggregate [(Me 2 PCH 2 ) 3 CO -‚3Li + ‚(Me 2 PCH) 3 C 2-] (6), consisting of an almost equilateral triangle of lithium atoms sandwiched between the two anions. Each lithium atom has a severly distorted tetrahedral coordination geometry consisting of two phosphino donors, one oxygen atom, and one methylene group.

Alkali Metal Complexes of a tert-Butylphosphine-Bridged Biphenolate Ligand

“…A variable-temperature 31 P{ 1 H} NMR study in toluene- d 8 at −80 °C revealed two distinct 1:1:1:1 quartet resonances at −23.3 and −30.1 ppm with coupling constants of 41 and 60 Hz, respectively, indicating the coordination of the soft phosphorus donors to hard, quadrupolar 7 Li atoms ( I = 3/2, natural abundance 92.6%). The magnitude of these coupling constants is similar to those found for other lithium phosphine complexes such as Li[N( o -C 6 H 4 PPh 2 ) 2 ](THF) 2 (34 Hz), , [Li(THF) 2 ][ o -(2,6-Me 2 C 6 H 3 N)C 6 H 4 PPh 2 ] (34 Hz), [Li(THF) 2 ][ o -(2,6- i Pr 2 C 6 H 3 N)C 6 H 4 PPh 2 ] (38 Hz), [(2,4,6-Me 3 C 6 H 2 )NLi-2-(4-MeC 6 H 3 )] 2 PPh(dioxane) (40 Hz), Li[N( o -C 6 H 4 P i Pr 2 ) 2 ](THF) (46 Hz), Li[N( o -C 6 H 4 PCy 2 ) 2 ](THF) (48 Hz), [(Me 2 PCH 2 ) 3 CO]Li 3 [C(CH P Me 2 ) 3 ] (58 Hz), and the lithium phosphide derivative [Li(tmeda)] 2 [1,2-C 6 H 4 (PPh) 2 ] (35 Hz) . Consistently, the 7 Li{ 1 H} NMR spectrum at −80 °C exhibits two doublet (3.0 ppm, 1 J PLi = 60 Hz; 1.6 ppm, 1 J PLi = 41 Hz) and two singlet (−0.8 and −0.9 ppm) resonances, confirming the phosphorus donor in each dinuclear unit is bound to one rather than two lithium centers.…”

Mixed donor-functionalised phosphinomethanide complexes of the alkali metals; synthesis, structures, and solution dynamics

“…The K-N distance of 2.862(3) A ˚is typical for such a contact; the corresponding distances in 5 range from 2.8008(16) to 2.8725(17) A ˚. As was observed for compounds 3-10, the carbanion centres in 12 and 13 are essentially planar [sum of angles at C(1) = 358.7 (12), 358.0 • (13); displacement of C(1) from the PSi 2 plane towards Na/K: 0.118 (12), 0.148 (13) A ˚]. For comparison, the sum of angles within the CSi 2 P skeletons in [[(Me 3 Si) 2 {Me 2 P(BH 3 )}C]Na(THF) 2 .1/2PhMe] • (16) and [[(Me 3 Si) 2 {Me 2 P(BH 3 )C}K] • (17), 14 which contain genuine M-C carbanion contacts, are 346.3 and 353.5/348.7 • , respectively, with corresponding displacement of the carbanion centre from the Si 2 P plane of 0.199 A ˚(16) and 0.267/0.355 A ˚ (17).…”

Synthesis, Crystal Structures and NMR Spectroscopic Studies on Ruthenium Complexes with Phosphanylacetal and Phosphanylthioacetal Ligands

“…The reaction of [RuCl 2 (PPh 3 ) 3 ] with PhPOO in methanol resulted in the formation of trans-[Ru II Cl 2 (PhP(OMe) 2 ) 2 ] (3). This complex is soluble in dichloromethane, sparingly soluble in acetonitrile and insoluble in most other solvents including diethyl ether and dimethyl sulfoxide.…”

“…[1][2][3] As part of our investigation of mixed P,Sdonor ligands [4][5][6] we have been exploring the chemistry of [2-(1,3-dioxolan-2-yl)phenyl]diphenylphosphane (1,PhPOO), [7] and [2-(1,3-dithiolan-2-yl)phenyl]diphenylphosphane (2, PhPSS) (Scheme 1). As well as possessing an enantiotopic carbon centre, these ligands have several possible binding modes, and have the potential to show hemilabile and fluxional behaviour.…”