Highly hindered γ-P^III-functionalised alkoxo–lithium complexes: syntheses and structures of [Li(µ-OCBu^t₂CH₂PR₂)]₂(R = Me or Ph) and [Li(µ-OCBu^t₂CH₂PPh₂)₂Li(OCBu^t₂)]

Abstract

Reaction of Li(CH2PR2)(tmeda) (R = M e or Ph; tmeda = N,N, N',N'-tetramethylethylenediamine); compound (2), the diphenyl analogue of ( l ) , is accessible either b y reaction of (3) and further Li(CH2PPh2)(tmeda) or b y lithiation of Ph2PCH2C(OH)Buf2: the y-P-functionalised lithium alkoxides (1 )-(3) are shown b y X-ray crystallography t o have Li-P bonds and very short Li-0 and Li --Li contacts, and compound (3) is structurally similar to the adduct proposed as an intermediate in the important carbanionic alkylation of a ketone.

Light‐Induced Rearrangement of Thioether‐Substituted Phosphanide Ligands: Scope and Limitations of a Remarkable Isomerization

“…For these compounds, the electron-withdrawing effect of the lithium cation in the phosphanide complexes [{(Me 3 Si) 2 CH}P(C 6 H 4 -2-SR 1 )]LiA C H T U N G T R E N N U N G (OEt 2 ) n is likely to be somewhat decreased and so CÀS cleavage is disfavored with respect to deprotonation at phosphorus, in spite of the large substituent at the latter site. In accord with this, treatment of either 2 P H or The 1 H, 13 C{ 1 H}, 31 P{ 1 H}, and 7 Li NMR spectra of the phosphanide complexes 1 P a-5 P a, 1 P b-5 P b, 1 P d, and 1 P e are consistent with the above formulations. The 31 P{ 1 H} and 7 Li NMR spectra of both 2 P b and 3 P b in C 6 D 6 exhibit a 1:1:1:1 quartet and a doublet, respectively, due to coupling between these two nuclei (J PLi = 63.3 (2 P b), 70.2 Hz (3 P b)), suggesting that P-Li exchange is slow on the NMR timescale for these compounds.…”

“…Synthesis of secondary phosphane precursors: The thio-A C H T U N G T R E N N U N G ethers 2-BrC 6 H 4 SR 1 (R 1 = nPr (I), Ph (II)) were prepared by the reaction of 1,2-dibromobenzene with the corresponding sodium thiolate in the polar solvent 1,3-dimethyl-2-imidazolidinone; extended reaction times (typically 24 h) and high temperatures were required to force these reactions to completion, but both I and II were isolated in good yield and purity. Lithium-halogen exchange reactions between either I or II and nBuLi at 0 8C generated the corresponding aryllithium compounds, which were reacted in situ with [(Me 3 Si) 2 CH]PCl 2 to give the chlorophosphanes [(Me 3 Si) 2 CH]P(Cl)(C 6 H 4 -2-SR 1 ) (R 1 = nPr (2 P Cl), Ph (3 P Cl)); these were shown by 1 H and 31 In contrast to the relatively straightforward syntheses of 2 P H-4 P H, reactions between PhPCl 2 and one equivalent of in situ-generated 2-LiC 6 H 4 SMe gave mixtures of the secA C H T U N G T R E N N U N G ond-A C H T U N G T R E N N U N G ary chlorophosphane PhP(Cl)(C 6 H 4 -2-SMe) and the terA C H T U N G T R E N N U N G tiary phosphane PhP(C 6 H 4 -2-SMe) 2 , along with unreacted PhPCl 2 , owing to the small size of the phenyl substituent. This difficulty was overcome by protection of one of the chloride substituents as its diisopropylamide derivative: The reaction between PhP(Cl)A C H T U N G T R E N N U N G (NiPr 2 ) and in situ-generated 2-LiC 6 H 4 SMe proceeded cleanly to give PhP(C 6 H 4 -2-SMe)-A C H T U N G T R E N N U N G (NiPr 2 ).…”

“…We have shown in our previous preliminary report, that secondary phosphanes of this type rapidly undergo deprotonation in the presence of thiolates and that the resulting phosphanide-thiolate dianions are stable towards protonation even in the presence of excess secondary phosphane (1 P H undergoes concurrent demethylation and deprotonation, leaving half of the starting phosphane intact). We therefore suggest that 2 S b' is rapidly deprotonated by 2 S b (formed simultaneously in the reaction) to give 1 PS b, yielding the tertiary phosphane-thiol [(Me 3 Si) 2 CH]PA C H T U N G T R E N N U N G (nPr)(C 6 H 4 -2-SH) (2 S H) as coproduct; we attribute one of the two peaks B and D in the 31 P{ 1 H} NMR spectrum to this latter species.…”

Synthesis and characterization of novel chelated dimethylamino lithium alkoxides: molecular structures of [1‐LiOC(C6H11)2‐2‐NMe2C6H4]2 and [1‐LiOCPh2CH2‐2‐NMe2C6H4]2

“…a THF-solvated dimer of lithium tert-butoxide. 4 Internal coordination by oxygen, 5 nitrogen, 6±13 phosphorus, 14,15 sulfur, 16 p-systems, 16±18 and cyclopropyl groups 19 have been identified in lithium alkoxides and show the diversity of the compounds. X-ray, NMR, and other techniques have confirmed a variety of different aggregate sizes of lithium alkoxides.…”

Metal-Oxygen-Metal' Ring Formation in Metal Alkoxide Systems

“…It is noteworthy that the tetraisopropoxoaluminates of lanthanides19 ' distil as monomeric species without dissociation.The basic skeleton of the structure for potassium tetraisopropoxoaluminate isopropylate as suggested by Mehrotra 1101 has again been confirmed(Fig.3)by Gilje, et al 1 "' in 1993 :…”