Novel sandwich complexes of zirconium [C9H5(SiMe3)2](C5Me4R)ZrCl2 (R = CH3, CH2CH2NMe2): Synthesis and reduction behavior

Novel half-sandwich [C₉H₅(SiMe₃)₂]ZrCl₃ (3) and sandwich [C₉H₅(SiMe₃)₂](C₅Me₄R)ZrCl₂ (R = CH₃ (1), CH₂CH₂NMe₂ (2)) complexes were prepared and characterized. The reduction of 2 by Mg in THF lead to (η⁵-C₉H₅(SiMe₃)₂)[η⁵:η²(C,N)-C₅Me₄CH₂CH₂N(Me)CH₂]ZrH (7). The structure of 7 was proved by NMR spectroscopy data. Hydrolysis of 2 resulted in the binuclear complex ([C₅Me₄CH₂CH₂NMe₂]ZrCl₂)₂O (6). The crystal structures of 1 and 6 were established by X-ray diffraction analysis.     

Syntheses of rac/meso-{PhP(3-t-Bu-C5H3)2}-Zr{RN(CH2)3NR}, structural analyses of rac-{PhP(3-t-Bu-C5H3)2}Zr{RN(CH2)3NR} (where R is SiMe3 or Ph), and meso to rac isomerization

Syntheses of rac/meso-{PhP(3-t-Bu-C₅H₃)₂}Zr{Me₃SiN(CH₂)₃NSiMe₃} (rac-3/meso-3) and rac/meso-{PhP(3-t-Bu-C₅H₃)₂}Zr{PhN(CH₂)₃NPh} (rac-4/meso-4) were achieved by metallation of K₂[PhP(3-t-Bu-C₅H₃)₂] · 1.3 THF (2) with Zr{RN(CH₂)₃NR}Cl₂(THF)₂ (where R = SiMe₃ or Ph, respectively) using ethereal solvent. These isomeric pairs were characterized by ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy; rac-3 and rac-4 were also examined via single crystal X-ray crystallography. The structures of rac-3 and rac-4 are notable in the tendency of the cyclopentadienyl rings towards η³ coordination. While isolated samples of rac-3/meso-3 and rac-4/meso-4 slowly isomerize in tetrahydrofuran-d₈ to equilibrium ratios, the isomerization rate for 3 is more than 15-fold greater than that for 4. In addition, equilibrium ratios are rapidly reached when isolated samples of rac-3/meso-3 and rac-4/meso-4 are exposed to tetrabutylammonium chloride in tetrahydrofuran-d₈ solvent. We propose that a nucleophile (either chloride or the phosphine interannular linker) brings about dissociation of one cyclopentadienyl ring, thus promoting the rac/meso isomerization mechanism.     

Steric and electronic effects in stabilizing allyl-palladium complexes of “P-N-P” ligands, X2PN(Me)PX2 (X = OC6H5 or OC6H3Me2-2,6)

The chemistry of η³-allyl palladium complexes of the diphosphazane ligands, X₂PN(Me)PX₂ [X = OC₆H₅ (1) or OC₆H₃Me₂-2,6 (2)] has been investigated.The reactions of the phenoxy derivative, (PhO)₂PN(Me)P(OPh)₂ with [Pd(η³-1,3-R′,R″-C₃H₃)(μ-Cl)]₂ (R′ = R″ = H or Me; R′ = H, R″ = Me) give exclusively the palladium dimer, [Pd₂{μ-(PhO)₂PN(Me)P(OPh)₂}₂Cl₂] (3); however, the analogous reaction with [Pd(η³-1,3-R′,R″-C₃H₃)(μ-Cl)]₂ (R′ = R″ = Ph) gives the palladium dimer and the allyl palladium complex [Pd(η³-1,3-R′,R″-C₃H₃)(1)](PF₆) (R′ = R″ = Ph) (4). On the other hand, the 2,6-dimethylphenoxy substituted derivative 2 reacts with (allyl) palladium chloro dimers to give stable allyl palladium complexes, [Pd(η³-1,3-R′,R″-C₃H₃)(2)](PF₆) [R′ = R″ = H (5), Me (7) or Ph (8); R′ = H, R″ = Me (6)].Detailed NMR studies reveal that the complexes 6 and 7 exist as a mixture of isomers in solution; the relatively less favourable isomer, anti-[Pd(η³-1-Me-C₃H₄)(2)](PF₆) (6b) and syn/anti-[Pd(η³-1,3-Me₂-C₃H₃)(2)](PF₆) (7b) are present to the extent of 25% and 40%, respectively. This result can be explained on the basis of the steric congestion around the donor phosphorus atoms in 2. The structures of four complexes (4, 5, 7a and 8) have been determined by X-ray crystallography; only one isomer is observed in the solid state in each case.     

New orthopalladated complexes of phosphorus ylides: Crystal structure of [Pd{CH{P(C7H6)(p-tolyl)2}COCH3}Cl{P(p-tolyl)3}]

This work reports on the preparation of the complexes [PdCl₂(Y¹)₂], [PdCl₂(Y²)₂] (Y¹ = (p-tolyl)₃PCHCOCH₃ (1a); Y² = Ph₃PCHCO₂CH₂Ph (1b)), [Pd{CHP(C₇H₆)(p-tolyl)₂COCH₃}(μ-Cl)]₂ (2a), [Pd{CHP(C₆H₄)Ph₂CO₂CH₂Ph}(μ-Cl)]₂ (2b), [Pd{CH{P(C₇H₆)(p-tolyl)₂}COCH₃}Cl(L)] (L = PPh₃ (3a), P(p-tolyl)₃ (4a)) and [Pd{CH{P(C₆H₄)Ph₂}CO₂CH₂Ph}Cl(L)] (L = PPh₃ (3b), P(p-tolyl)₃ (4b)). Orthometallation and ylide C-coordination in complexes 2a–4b are demonstrated by an X-ray diffraction study of 4a.     

1-Methylimidazolin-2-yl functionalized cyclopentadienyl complexes of titanium and zirconium. Crystal structure of {[η:η-κN-C5H4CPh2CH2-(1-Me-C3H4N2)]ZrCl2}2(μ-Cl)2

The novel bidentate ligand, C₅H₄CPh₂CH₂-(1-Me-C₃H₄N₂) (3), has been prepared and characterized as its lithium salt LiC₅H₄CPh₂CH₂-(1-Me-C₃H₄N₂) (3-Li). Cyclopentadiene HC₅H₄CPh₂CH₂-(1-Me-C₃H₄N₂) (3-H) has been obtained from 6,6-diphenylfulvene and 1,2-dimethylimidazoline (1). In THF-d₈ solution in the presence of 1, (1-methylimidazoline-2-yl)methyllithium (2) has been proved to undergo gradual conversion into a dilithium derivative of N¹-methyl-N²-[(1E,2E)-1-methyl-2-(1-methylimidazolidine-2-idene)ethylidene]ethane-1,2-diamine (2a). In a solution, cyclopentadiene 3-H has been shown to undergo isomerization into 3-{N-[2-(N-methylamino)ethyl]amino}-1,1-diphenyl-1,2-dihydropentalene (4) and, further, into a mixture of 4 and two rotameric 3-[N-(2-aminoethyl)-N-methylamino]-1,1-diphenyl-1,2-dihydropentalenes (5a) and (5b). Treatment of the lithium salt 3-Li with Me₃SiCl has lead to 3-{N-[2-(N-trimethylsilylamino)ethyl]amino}-1,1-diphenyl-1,2-dihydropentalene (6) as the dominant component in the reaction mixture. In the latter case the expected Me₃Si-C₅H₄CPh₂CH₂-(1-Me-C₃H₄N₂) (3-Si) was not observed. Stannylation of 3-Li with 1 equiv. of Me₃SnCl has resulted in formation of a mixture of Me₃Sn-C₅H₄CPh₂CH₂-(1-Me-C₃H₄N₂) (3-Sn), (Me₃Sn)₂-C₅H₃CPh₂CH₂-(1-Me-C₃H₄N₂) (3-Sn₂), and cyclopentadiene 3-H in a ca. 2:1:1 molar ratio. Monocyclopentadienyl complexes {[η⁵:η¹-κN-C₅H₄CPh₂CH₂-(1-Me-C₃H₄N₂)]MCl₃ (M = Ti (7), Zr (8)) have been prepared starting from the organotin and organolithium compounds 3-Sn and 3-Li, respectively. The dynamic behavior of complexes 7 and 8 has been investigated by means of variable-temperature NMR spectroscopy in solutions. The molecular structures of the dihydropentalene 4, binuclear complex {[η⁵:η¹-κN-C₅H₄CPh₂CH₂-(1-Me-C₃H₄N₂)]ZrCl₂}₂(μ-Cl)₂8, and a coordination dimer of the dilithium salt 2a have been established by X-ray diffraction analysis. In the crystal structure of the 2a-dimer, the shortest known Li-Li contact has been found.     

Oxime-substituted NCN-pincer palladium and platinum halide polymers through non-covalent hydrogen bonding (NCN = [C6H2(CH2NMe2)2-2,6])

The oxime-substituted NCN-pincer molecules HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 (2a) and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (2b) were accessible by treatment of the benzaldehydes H(O)C-4-C₆H₃(CH₂NMe₂)₂-3,5 (1a) and H(O)C-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (1b) with an excess of hydroxylamine. In the solid state both compounds are forming polymers with intermolecular O-H?N connectivities between the Me₂NCH₂ substituents and the oxime entity of further molecules of 2a and 2b, respectively. Characteristic for 2a and 2b is a helically arrangement involving a crystallographic 2₁ screw axis of the HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 building blocks.The reaction of 2b with equimolar amounts of [Pd₂(dba)₃ · CHCl₃] (3) (dba = dibenzylidene acetone) or [Pt(tol)₂(SEt₂)]₂ (4) (tol = 4-tolyl) gave by an oxidative addition of the C-Br unit to M coordination polymers with a [(HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6)MBr] repeating unit (5: M = Pd, 6: M = Pt). Complexes 5 and 6 are in the solid state linear hydrogen-bridged polymers with O-H?Br contacts between the oxime entities and the metal-bonded bromide.     

Hydroxy- and boronic-acid-functionalized carbosilanes: Synthesis and solid state structure of Si(C6H4-4-SiMe2((CH2)3OH))4

Consecutive synthesis methodologies for the preparation of carbosilanes (Ph)(Me)Si((CH₂)₃B(OH)₂)₂ (2), Si(C₆H₄-4-SiMe₂((CH₂)₃B(OH)₂))₄ (5), (Ph)(Me)Si((CH₂)₃OH)₂ (3), and Si(C₆H₄-4-SiMe_3−n((CH₂)₃OH)_n)₄ (6a, n = 1; 6b, n = 2; 6c, n = 3) are reported. Boronic acids 2 and 5 are accessible by treatment of (Ph)(Me)Si(CH₂CHCH₂)₂ (1) or Si(C₆H₄-4-SiMe₂(CH₂CHCH₂))₄ (4a) with HBBr₂·SMe₂ followed by addition of water, while 3 and 6 are available by the hydroboration of 1 or Si(C₆H₄-4-SiMe_3−n(CH₂CHCH₂)_n)₄ (4a, n = 1; 4b, n = 2; 4c, n = 3) with H₃B·SMe₂ and subsequent oxidation with H₂O₂.The single molecular structure of 6a in the solid state is reported. Representative is that 6a crystallized in the chiral non-centrosymmetric space group P2₁2₁2₁ forming 2D layers due to intermolecular hydrogen bond formation of the HO functionalities along the crystallographic a and c axes.     

Simple protocol for the synthesis of the asymmetric PCP pincer ligand [C6H4-1-(CH2PPh2)-3-(CH(CH3)PPh2)] and its Pd(II) derivative [PdCl{C6H3-2-(CH2PPh2)-6-(CH(CH3)PPh2)}]

The asymmetric PCP pincer ligand [C₆H₄-1-(CH₂PPh₂)-3-(CH(CH₃)PPh₂)] (4) has been synthesized in a facile manner in three simple steps in high yield. Metallation of PCP pincer ligand (4) with [Pd(COD)Cl₂] affords complex [PdCl{C₆H₃-2-(CH₂PPh₂)-6-(CH(CH₃)PPh₂)}] (7) in good yield.     

One-pot synthesis of the new dianionic ligand [Na]2[C5H4CO2(CH2)2NTs]; preparation and structures of two rhodium derivatives

The new dianionic ligand [Na]₂[C₅H₄CO₂(CH₂)₂NTs] (1) having an alkoxycarbonyl and an amide group in the same side chain has been prepared by a single step, high yield procedure. The synthesis of the related rhodium complexes [Rh{η⁵-C₅H₄CO₂(CH₂)₂N(H)Ts}(NBD)] (3) and [Rh{η⁵-C₅H₄CO₂ (CH₂)₂N(Me)Ts}(NBD)] (4) is reported as well as their X-ray molecular structures.     

Heteroleptic tin (II) dialkoxides stabilized by intramolecular coordination Sn(OCH2CH2NMe2)(OR) (R = Me, Et, Pr, Bu, Ph). Synthesis, structure and catalytic activity in polyurethane synthesis

A straightforward method of synthesis of heteroleptic tin (II) alkoxides stabilized by one intramolecular coordination bond was developed. Addition of one equivalent of dimethylamino ethanol to diamide Sn(N(SiMe₃)₂)₂ (5) yields alkoxy-amido derivative Sn(OCH₂CH₂NMe₂)(N(SiMe₃)₂) (2). Further addition of alcohol leads to corresponding heteroleptic dialkoxides Sn(OCH₂CH₂NMe₂)(OR) (R = Me (6), Et (7), ⁱPr (8), ^tBu (9), Ph (10)). Catalytic activity of tin (II) compounds in polyurethane formation was tested.     

Syntheses of platinum(II) complexes of cyclo-octenyl group and isolation of a self-assembled oxo-bridged macrocyclic complex [Pt4(Spy)4(C8H12-O-C8H12)2]

Reactions of [Pt₂(μ-Cl)₂(C₈H₁₂OMe)₂] (1) (C₈H₁₂OMe = 8-methoxy-cyclooct-4-ene-1-yl) with various anionic chalcogenolate ligands have been investigated. The reaction of 1 with Pb(Spy)₂ (HSpy = pyridine-2-thiol) yielded a binuclear complex [Pt₂(Spy)₂(C₈H₁₂OMe)₂] (2). A trinuclear complex [Pt₃(Spy)₄(C₈H₁₂OMe)₂] (3) was isolated by a reaction between 2 and [Pt(Spy)₂]_n. The reaction of 1 with HSpy in the presence of NaOMe generated 2 and its demethylated oxo-bridged tetranuclear complex [Pt₄(Spy)₄(C₈H₁₂-O-C₈H₁₂)₂] (4). Treatment of 1 with ammonium diisopropyldithiophosphate completely replaced C₈H₁₂OMe resulting in [Pt(S₂P{OPrⁱ}₂)₂] (5), whereas non-rigid 5-membered chelating ligand, Me₂NCH₂CH₂E⁻, produced mononuclear complexes [Pt(ECH₂CH₂NMe₂)(C₈H₁₂OMe)] (E = S (6), Se (7)). These complexes have been characterized by elemental analyses, NMR (¹H, ¹³C{¹H}, ¹⁹⁵Pt{¹H}) and absorption spectroscopy. Molecular structures of 2, 3, 4, 5 and 7 were established by single crystal X-ray diffraction analyses. Thermolysis of 2, 6 and 7 in HDA gave platinum nanoparticles.     

Synthesis of aluminum alkoxide and bis-alkoxide compounds containing bidentate pyrrolyl ligands

A series of aluminum alkoxide and bis-alkoxides compounds were synthesized and characterized. Reacting 1 with 1 and 2 equiv. of t-butanol in methylene chloride generates [C₄H₃N(CH₂NMe₂)-2]₂Al(O-t-Bu) (2) and [C₄H₃N(CH₂NMe₂)-2-H-C₄H₃N(CH₂NMe₂)-2]Al(O-t-Bu)₂ (3) in 47% and 54% yield, respectively. The ¹H NMR spectrum of 2 exhibits two singlets for NMe₂ and CH₂N at δ 2.52 and 3.84, respectively, representing the symmetrical manner of molecular structure 2 in a solution. Compound 3 is not thermal stable in solution which decompose into substituted pyrrole ligand C₄H₄N(CH₂NMe₂)-2 and unknown aluminum alkoxides. Reacting 1 with 2 equiv. of triphenylsilanol in methylene chloride generates a tetra-coordinated aluminum “ate” compound [C₄H₃N(CH₂NMe₂)-2-H- C₄H₃N(CH₂NMe₂)-2]Al(OSiPh₃)₂ (4) in 49% yield. The ¹H NMR spectra of 4 at room temperature show a broad signal at δ 1.57 for NMe₂ fragments and the signals for CH₂N were not observed. VT ¹H NMR spectra of 4 show the NMe₂ fragments became two singlets (δ 1.27 and 2.12) and the CH₂N exhibited two doublets (δ 2.44 and 3.56) at 240 K. The fluxional energy barrier (ΔG^‡) is estimated at ca. 50 kJ/mol. The molecular structures of compounds 3 and 4 are determined by single-crystal X-ray diffractometer.     

Branched and dendritic metallo-carbosiloxanes with OCH2PPh2MLn end-grafted units

A straightforward method for the preparation of metallo carbosiloxanes of type Si(OCH₂CH₂CH₂SiMe₂[OCH₂PPh₂M(CO)_n])₄ (n = 3, M = Ni, 7a; n = 4, M = Fe, 7b; n = 5: M = Mo, 7c; M = W, 7d), Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₄ (8) and Me₂Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₂ (11) is described. The reaction of Si(OCH₂CH₂CH₂SiMeXCl)₄ (1: X = Me, 2: X = Cl) or Me₂Si(OCH₂CH₂CH₂SiMeCl₂)₂ (9) with HOCH₂PPh₂ (3) produces Si(OCH₂CH₂CH₂SiMe₂(OCH₂PPh₂))₄ (4), Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₄ (5) or Me₂Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₂ (10) in presence of DABCO. Treatment of the latter molecules with Ni(CO)₄ (6a), Fe₂(CO)₉ (6b), M(CO)₅(Thf) (6c: M = Mo; 6d: M = W), respectively, gives the title compounds 7a-7d, 8 and 11 in which the PPh₂ groups are datively bound to a 16-valence-electron metal carbonyl fragment.The formation of analytical pure and uniform branched and dendritic metallo carbosiloxanes is based on elemental analysis, and IR, ¹H, ¹³C{¹H}, ²⁹Si{¹H} and ³¹P{¹H} NMR spectroscopic studies. In addition, ESI-TOF mass spectrometric studies were carried out.     

Reaction of nido-1,2-(CpRuH)2B3H7 with ethynylferrocene to yield new metallacarboranes

Addition of ethynylferrocene to nido-1,2-(Cp^∗RuH)₂B₃H₇ (1) at ambient temperature leads to nido-1,2-(Cp^∗Ru)₂(1,5-μ-C{Fc}Me)B₃H₇ (2, 3) and closo-4-Fc-1,2-(Cp^∗RuH)₂-4,6-C₂B₂H₃ (4). Compounds 2 and 3 represent a pair of geometric isomers, nido-species in which the regiochemistry of the alkyne reduction conforms to the Markovnikoff rule. Compound 4 is an octahedral structure in which the inserted alkyne is on an open face of the closo cluster.     

Understanding the role of an easy-to-prepare aldimine-alkyne carboamination catalyst, [Ti(NMe2)3(NHMe2)][B(C6F5)4]

A series of reactivity studies of the carboamination pre-catalyst [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄] as well as the preparation of other catalysts are reported in this work. Treatment of [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄] with the aldimines Ar′NCHtol (Ar′ = 2,6-Me₂C₆H₃, tol = 4-MeC₆H₄), and depending on the reaction conditions, results in isolation of [Me₂NCHR′][B(C₆F₅)₄] (1) or (Me₂N)₂CHtol, as well as the asymmetric titanium dimer [(Me₂N)₂(HNMe₂)Ti(μ₂-N[2,6-Me₂C₆H₃])₂Ti(NHMe₂)(NMe₂)][B(C₆F₅)₄] (2). Protonation of CpTi(NMe₂)₃ and Cp^∗Ti(NMe₂)₃ results in isolation of the salts, [CpTi(NMe₂)₂(NHMe₂)][B(C₆F₅)₄] (3) and [Cp^∗Ti(NMe₂)₂(NHMe₂)][B(C₆F₅)₄] (4), respectively. Treatment of compounds 3 or 4 with H₂N[2,6-ⁱPr₂C₆H₃] results in formation of the imido salts [CpTi(N[2,6-ⁱPr₂C₆H₃])(NHMe₂)₂][B(C₆F₅)₄] (5) (58% yield) or [Cp^∗Ti(N[2,6-ⁱPr₂C₆H₃])(NHMe₂)₂][B(C₆F₅)₄] (6). When Ti(NMe₂)₄ is treated with [Et₃Si][B(C₆F₅)₄], the salt [Ti(NMe₂)₃(N[SiEt₃]Me₂)][B(C₆F₅)₄] (7) is obtained, and treatment of the latter with [2,6-ⁱPr₂C₆H₃]NCHtol produces the imine adduct [Ti(NMe₂)₃(κ¹-[2,6-ⁱPr₂C₆H₃]NCHtol)][B(C₆F₅)₄] (8). The carboamination catalytic activity of complexes 2-7 was investigated and compared to [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄]. Likewise, a proposed mechanism to the active carboamination catalyst stemming from [Ti(NMe₂)₃(NHMe₂)][B(C₆F₅)₄] is described.     

Reverse Kocheshkov reaction - Redistribution reactions between RSn(OCH2CH2NMe2)2Cl (R = Alk, Ar) and PhSnCl3: Experimental and DFT study

A series of organotin compounds bearing two intramolecular N → Sn coordination bonds RSn(OCH₂CH₂NMe₂)₂Cl (R = Me (4), n-Bu (5), Mes (6)) were synthesized in good yields. These compounds as well as 2 (R = Ph) react with PhSnCl₃ to give redistribution products RPhSnCl₂ and (Me₂NCH₂CH₂O)₂SnCl₂ (3). The direction of redistribution reactions is reverse to Kocheshkov reaction. DFT calculations have shown that the driving force of the reactions is formation of intramolecular N → Sn coordination bonds in (RO)₂SnCl₂ (3), the Lewis acid stronger than RSn(OR)₂Cl (2, 4-6). The mechanism of the redistribution reaction between 2 and PhSnCl₃ consists of two steps: (1) initial exchange of OCH₂CH₂NMe₂ and Cl to give PhSn(OCH₂CH₂NMe₂)Cl₂ (7) followed by (2). Ph and OCH₂CH₂NMe₂ exchange.     

Syntheses and NMR study of [(2-dimethylaminomethyl)phenyl]vinylsilane derivatives and [(2-dimethylaminomethyl)phenyl]ethylsilane derivatives

Various vinylsilanes, SiX(CHCH₂)(CH₃)[2-(CH₃)₂NCH₂C₆H₄], and ethylsilanes, SiX(CH₂CH₃)(CH₃)[2-(CH₃)₂NCH₂C₆H₄] [X=Cl (1); OMe (2); H (3); F (4); OSiMe₃ (5); NMe₂ (6); Me (7)], were synthesized in order to investigate the electronic effect of vinyl group on silicon atom having an intramolecular coordination arm. The magnitude of Δδ (ethyl→vinyl for ²⁹Si-NMR) of chlorosilane, 1, was the biggest one among 1-7. The differences of ²⁹Si chemical shifts between vinylsilanes and ethylsilanes increased in the following order: X=Me, NMe₂<H<OSiMe₃<OMe<F<Cl.     

X-ray and multinuclear NMR study of the mixed aggregate [(Ph2P(O)N(CH2Ph)CH3) · LiOC6H2-2,6-{C(CH3)3}2-4-CH3) · C7H8]2: a model for the directed metalation of phosphinamides

The addition of LiBuⁿ to a toluene solution of Ph₂P(O)N(CH₂Ph)CH₃1 and 2,6-di-tert-butyl-4-methylphenol 5 leads to the formation of the mixed dimer [(Ph₂P(O)N(CH₂Ph)CH₃) · LiOC₆H₂-2,6-{C(CH₃)₃}₂-4-CH₃) · C₇H₈]₂6. The single crystal X-ray structure shows that two lithium aryloxide moieties dimerize giving rise to a Li₂O₂ core in which each lithium atom is additionally coordinated to a phosphinamide 1 ligand. The multinuclear magnetic resonance study (¹H, ⁷Li, ¹³C, ³¹P) indicates that the solid-state structure is preserved in toluene solution. Complex 6 may be considered as a model for the pre-complexation step preceding the metalation of phosphinamides by an organolithium base.     

Convenient syntheses of fluorous phenols of the formula HOC6H5−n((CH2)3(CF2)7CF3)n (n=1, 2) and the corresponding triarylphosphites

The aldehydic benzyl ethers PhCH₂OC₆H₄CHO (2; a/b = para/meta series) are readily available from the corresponding phenols and react with Wittig reagents derived from [Ph₃PCH₂CH₂R_f8]⁺I⁻ (R_f8=(CF₂)₇CF₃) to give PhCH₂OC₆H₄CHCHCH₂R_f8 (86-93%, Z major). Reactions with H₂ over Pd/C give the fluorous phenols HOC₆H₄(CH₂)₃R_f8(4a,b; 87-91%). Condensations with PCl₃ and NEt₃ (3.0:1.0:3.3 mol ratio) give the fluorous phosphites P[OC₆H₄(CH₂)₃R_f8]₃(5a,b; 92-94%), but traces of 4a,b are difficult to remove. The phthalate-based benzyl ethers PhCH₂OC₆H₃(COOR)₂ (7; ,5/3,4 OC₆H₃-3,n-(R)₂ series) are easily accessed and reduced with LiAlH₄ to the diols PhCH₂OC₆H₃(CH₂OH)₂(8c,d; 89-90%). Diol 8c and the Dess-Martin periodinane react to give the dialdehyde PhCH₂OC₆H₃(CHO)₂ (9c; 95%). This is elaborated by a sequence analogous to 2→4→5 to the fluorous phenol HOC₆H₃((CH₂)₃R_f8)₂ (11c; 97%/96%, two steps) and phosphite P[OC₆H₃((CH₂)₃R_f8)₂]₃ (12c, 92%), from which traces of 11c are difficult to remove. Diol 8d can be similarly elaborated to 11d, but the dialdehyde 9d is labile and the combined yield of the Dess-Martin/Wittig steps is 32%. The CF₃C₆F₁₁/toluene partition coefficients of 11c,d, and 12c (two pony tails; 70:30, 72:28, 92:8) are much higher than those of 4a and b (one pony tail; 12:88, 14:86).     

Synthesis and characterization of ionic organotin compounds [R2SnCl2(2-quin)](HNEt3) and crystal structures of [(2,4-Cl2-C6H3CH2)2SnCl2(2-quin)](HNEt3)

Eight ionic organotin compounds [R₂SnCl₂(2-quin)]⁻(HNEt₃)⁺ have been synthesized by reactions of 2-quinH with R₂SnCl₂ (R = PhCH₂1, 2-Cl-C₆H₄CH₂2, 4-Cl-C₆H₄CH₂3, 2-F-C₆H₄CH₂4, 4-F-C₆H₄CH₂5, 4-CN-C₆H₄CH₂6, Ph 7, 2,4-Cl₂-C₆H₃CH₂8) in the presence of organic base NEt₃, and their structures have been characterized by elemental analysis, IR and multinuclear NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopies. The structure of [(2,4-Cl₂-C₆H₃CH₂)₂SnCl₂(2-quin)]⁻(NEt₃)⁺ (8) has been determined by X-ray diffraction study. Studies show that compound 8 has a monomeric structure with the central tin atom six-coordinate in a distorted octahedral configuration and the nitrogen atoms of the 2-quin ligands are coordinating to the tin atom in all the eight compounds.