Synthesis and Structural Characterization of the Solvent-Free Potassium Derivative of a Terphenyl-Substituted Primary Phosphane: [(2,6-Dimesitylphenyl)P(H)K](4)

Solid-State Isolation of Cyclic Alkyl(Amino) Carbene (cAAC)-Supported Structurally Diverse Alkali Metal-Phosphinidenides

Cyclic alkyl(amino) carbene (cAAC)-supported, structurally diverse alkali metal-phosphinidenides 2-5 of general formula ((cAAC)P-M)_n (THF)_x [2: M=K, n=2, x=4; 3: M=K, n=6, x=2; 4: M=K, n=4, x=4; 5: M=Na, n=3, x=1] have been synthesized by the reduction of cAAC-stabilized chloro-phosphinidene cAAC=P-Cl (1) utilizing metallic K or KC₈ and Na-naphthalenide as reducing agents. Complexes 2-5 have been structurally characterized in solid state by NMR studies and single crystal X-ray diffraction. The proposed mechanism for the electron transfer process has been well-supported by cyclic voltammetry (CV) studies and Density Functional Theory (DFT) calculations. The solid state oligomerization process has been observed to be largely dependent on the ionic radii of alkali metal ions, steric bulk of cAAC ligands and solvation/de-solvation/recombination of the dimeric unit [(cAAC)P-M(THF)_x ]₂ .

Synthesis of Sterically Demanding Secondary Phosphides and Diphosphanes and Their Utilization in Small-Molecule Activation

Sterically demanding secondary potassium phosphides (4) were synthesized and investigated. Reaction with halophosphanes (5) yields diphosphanes (6), whereas reaction with CS₂ yields phosphanyl dithioformates (10). These can be further converted to the corresponding phosphanyl esters of dithioformic acid R₂P-C(S)S-PR₂ (8). One of these thioesters (8) was found to undergo a migration reaction, resulting in the formation of a phosphanylthioketone with an additional phosphanylthiolate group (9), which was used as a chiral ligand in gold coordination chemistry. The phosphanyl migration reaction was investigated by spectroscopic and theoretical methods, revealing a first-order reaction via a cyclic transition state. All species mentioned were fully characterized.

Lithium, sodium, potassium and calcium amine-bis(phenolate) complexes in the ring-opening polymerization of rac-lactide

Compounds of Li, Na, K and Ca of a tetradentate amino-bis(phenolato) ligand were prepared. Bimetallic compounds formulated as M₂[L](THF)_n (where M = Na, n = 1 (1·THF) or Li, n = 1 (2·THF)) were synthesized via the reaction of H₂[L] (where [L] = 2-pyridylmethylamino-N,N-bis(2-methylene-4-methoxy-6-tert-butylphenolato) with sodium hydride or n-butyllithium, respectively, in THF. Monometallic complexes MH[L](THF)_n (where M = Na, n = 1 (3·THF), Li, n = 0 (4) and K, n = 0 (5)) were obtained by reaction of H₂[L] with MN(SiMe₃)₂ where M = Na, Li, or K. Calcium complex Ca[L](THF) (6·THF) was synthesized in two ways; reaction of Na₂[L] with calcium iodide in THF, and reaction of Ca[N(SiMe₃)₂]₂ with H₂[L] in toluene. Compounds 1-6 exhibit activity for rac-lactide polymerization under melt and solution conditions. Moderate control of polymer molecular weights was achieved in toluene, whereas polydisperse polymer was obtained under solvent free conditions. MALDI-TOF MS analysis of the polymer end groups revealed a predominantly cyclic nature for the polylactides.

Desolvation and aggregation of sterically demanding alkali metal diarylphosphides

The reaction between (Dipp)₂PH and one equivalent of n-BuLi, PhCH₂Na or PhCH₂K in THF gives the complexes [(Dipp)₂P]Li(THF)₃ (2a), {[(Dipp)₂P]Na(THF)₂}₂ (3a) and [(Dipp)₂P]K(THF)₄ (4a), respectively [Dipp = 2,6-iPr₂C₆H₃]. Exposure of these compounds to vacuum yields the alternative solvates [(Dipp)₂P]Li(THF)₂ (2b), [(Dipp)₂P]Na(THF)_1.5 (3b), and [(Dipp)₂P]K (4b), respectively; the alternative adduct [(Dipp)₂P]Na(PMDETA) (3c) was prepared by treatment of 3a with PMDETA. Treatment of (Dipp)(Mes)PH or (Mes)₂PH with one equivalent of n-BuLi in THF gives the complexes [(Dipp)(Mes)P]Li(THF)₃ (7a) and [(Mes)₂P]₂Li₂(THF)₂(OEt₂) (8a) after crystallisation from diethyl ether [Mes = 2,4,6-Me₃C₆H₂]; crystallisation of 8a from hexane gives the alternative adduct [(Mes)₂P]Li(THF)₃ (8b). Exposure of 7a, 8a and 8b to vacuum leads to loss of coordinated solvent, yielding the solvates [(Dipp)(Mes)P]Li(THF)₂ (7b) and [(Mes)₂P]Li(THF) (8c). The solid-state structures of complexes 2a, 3a, 3c, 4a, 7a, 8a, and 8b have been determined by X-ray crystallography. Variable-temperature ³¹P{¹H} and ⁷Li NMR spectroscopy indicates that 2b, 3b and 7b are subject to a monomer-dimer equilibrium in solution, where the monomeric forms are favoured at low temperature. In contrast, variable-temperature ³¹P{¹H} and ⁷Li NMR spectroscopy suggests that 8c is subject to a dynamic equilibrium between a dimer and a cyclic trimer in solution, where the trimer is favoured at low temperatures.

Potassium complexes supported by monoanionic tetradentate amino-phenolate ligands: synthesis, structure and catalysis in the ring-opening polymerization of rac-lactide

A series of potassium complexes bearing monoanionic tetradentate amino-phenolate ligands, [LK]₂ (L = {(2-R¹)C₆H₄CH₂N[(CH₂)₂R²]CH₂(4-R⁴-6-R³)C₆H₂O-}, R¹ = NMe₂, R² = NEt₂, R³ = CPh₃, R⁴ = Me (1); R¹ = R² = NEt₂, R³ = CPh₃, R⁴ = Me (2); R¹ = NMe₂, R² = NEt₂, R³ = R⁴ = cumyl (4); R¹ = R² = OMe, R³ = ^tBu, R⁴ = Me (6); L = (2-NMe₂)C₆H₄CH₂N[[CH₂-(S)-1-butylpyrrolidinyl]CH₂(4-Me-6-CPh₃)C₆H₂O-] (3)), have been synthesized via reactions of KN(SiMe₃)₂ and 1 equiv. of the corresponding aminophenols. The solid-state structures of typical complexes 4 and 6 are determined via X-ray diffraction studies, which reveal the dinuclear nature of these complexes. By contrast, DOSY measurements of 1, 4 and 6 suggest that these complexes are monomeric in solution. It is noteworthy that the coordination chemistry of these potassium complexes is versatile, which is closely related to the nature of the ortho-substituent of the phenolate ring, as indicated by the results of the corresponding spectroscopic studies. In the presence of ⁱPrOH, 1-4 and 6 could initiate the polymerization of 500 equiv. of rac-lactide to achieve high monomer conversions within several minutes but afford atactic PLAs with slightly isotactic-enriched microstructures (P_m = 0.58-0.60). Experimental results also demonstrated that a bulky trityl substituent at the ortho-position of the phenolate ring of the ligand framework is beneficial for the enhancement of the activities of these potassium complexes.

A sodium ferrocenyl-phosphanide polymer based on racemic primary aminoalkyl(bisphosphanyl)ferrocene

The primary aminoalkyl(bisphosphanyl)ferrocenes 2-(N,N-dimethylaminomethyl)-1,1'-bis(phosphanyl)ferrocene (3a) and N,N-dimethyl-1-[1',2-bis(phosphanyl)ferrocenyl]ethylamine (3b) are readily available in two steps from the corresponding aminoalkylferrocenes. Deprotonation of 3a gave the first alkali metal aminoalkyl(bisphosphanido)ferrocene (4) as a one-dimensional polymer.

Synthesis and characterisation of yttrium complexes supported by the β-diketiminate ligand {ArNC(CH3)CHC(CH3)NAr}– (Ar = 2,6-Pri2C6H3)

Reaction of YI(3)(THF)(3.5) with one equivalent of the potassium beta-diketiminate (BDI) complex [HC{C(CH(3))NAr}(2)K] (Ar = 2,6-Pr(i)(2)C(6)H(3)) affords the monomeric, mono-substituted yttrium BDI complex [HC{C(CH(3))NAr}(2)YI(2)(THF)] in good yield. Reaction of with DME affords [HC{C(CH(3))NAr}(2)YI(2)(DME)] in quantitative yield, which is monomeric also. Reaction of the primary terphenyl phosphane Ar*PH(2) (Ar* = 2,6-(2,4,6-Pr(i)(3)C(6)H(2))(2)C(6)H(3)) with potassium hydride, and recrystallisation from hexane, affords the potassium primary terphenyl phosphanide complex [{Ar*P(H)K(THF)}(2)] in high yield. Compound is dimeric in the solid state, constructed around a centrosymmetric K(2)P(2) four-membered ring, the coordination sphere of potassium is supplemented with an eta(6) K[dot dot dot]C(aryl) interaction. The reaction of with one molar equivalent of in THF affords the THF ring-opened compound [HC{C(CH(3))NAr}(2)Y{O(CH(2))(4)P(H)Ar*}(I)(THF)]. Compound is formed as a mixture of endo(OR) and exo(OR) isomers (: = approximately 2 : 1) which may be separated by fractional crystallisation from hexane-toluene to give pure . Attempted alkylation of with two equivalents of KCH(2)Si(CH(3))(3) affords the potassium yttriate complex [Y{micro-eta(5):eta(1)-ArNC(CH(3))[double bond, length as m-dash]CHC([double bond, length as m-dash]CH(2))NAr}(2)K(DME)(2)] in moderate yield; contains two dianionic dianilide ligands, which are derived from C-H activation of a backbone methyl group, each bonded eta(5) to yttrium in the solid state. The reaction of with one equivalent of KC(8) affords [{HC(C[CH(3)]NAr)(2)YI(micro-OCH(3))}(2)], derived from C-O bond activation of DME, as the only isolable product in very low yield. Compounds , , , , , and have been characterised by single crystal X-ray diffraction, NMR spectroscopy and CHN microanalyses.

An N,P-disubstituted-2-aminophosphaalkene and lithium and potassium complexes of the deprotonated “phosphaamidinate” anion

The reaction of DippPH2(Dipp = 2,6-iPr2C6H3) with DippN=C(p-CH3C6H4)Cl in refluxing xylenes affords DippP=C(p-CH3C6H4)N(H)Dipp; deprotonation with alkali metal reagents produces unique lithium and potassium complexes with the ligand in a different geometry to that of the free phosphaamidine.

2,6-Diisopropylphenylphosphane: A new, bulky primary phosphane and its mono- and disilylated Si(CH3)3 and Si(CH3)2-t-Bu derivatives — A synthetic, crystallographic, and dynamic NMR investigation

The bulky primary phosphane 2,6-diisopropylphenylphosphane, DipPH2, has been prepared from 1-bromo-2,6-diisopropylbenzene via the reaction of the Grignard reagent with PCl3. The resulting mixed phosphonous dihalides DipP(Cl,Br)2 are reduced with LiAlH4 to yield the title compound in reasonable yield and on a synthetically useful scale. DipPH2 is also used to prepare the monosilylated derivatives DipPHSi(CH3)3 and DipPH{Si(CH3)2-t-Bu} as well as the disilylated compounds DipP{Si(CH3)3}2 and DipP{Si(CH3)2-t-Bu}2. All products have been fully characterized by IR, mass, and NMR spectroscopy. The crystal structure of DipPH{Si(CH3)2-t-Bu} was determined from single-crystal diffraction data: C18H33PSi, P21/c, Z = 4, a = 8.5768(10), b = 28.104(3), c = 8.1102(4) Å, β = 93.341(3)° (R = 0.0518). Changes in the NMR spectrum of DipPH{Si(CH3)2-t-Bu} were observed over the temperature range 178–380 K. Barrier heights were determined from the peak separation at low temperature and the coalescence points: ΔG‡ [Formula: see text] 40 kJ mol–1 for C(aryl)—P bond rotation and [Formula: see text] 72 kJ mol–1 for pyramidal inversion at phosphorus.Key words: crystal structure, 2,6-diisopropylphenyl, bulky substituents, steric congestion, dynamic NMR, primary phosphane, silyl phosphane.