Hydrogenation of β-Keto Sulfones to β-Hydroxy Sulfones with Alkyl Aluminum Compounds: Structure of Intermediate Hydroalumination Products

β-Hydroxy sulfones are important in organic synthesis. The simplest method of β-hydroxy sulfones synthesis is the hydrogenation of β-keto sulfones. Herein, we report the reducing properties of alkyl aluminum compounds R₃Al (R = Et, i-Bu, n-Bu, t-Bu and n-Hex); i-Bu₂AlH; Et₂AlCl and EtAlCl₂ in the hydrogenation of β-keto sulfones. The compounds i-Bu₂AlH, i-Bu₃Al and Et₃Al are the at best reducing agents of β-keto sulfones to β-hydroxy sulfones. In reactions of β-keto sulfones with aluminum trialkyls, hydroalumination products with β-hydroxy sulfone ligands [R₂AlOC(C₆H₅)CH₂S(O)₂(p-R¹C₆H₄]_n [where n = 1,2; 2aa: R = i-Bu, R¹ = CH₃; 2ab: R = i-Bu, R¹ = Cl; 2ba: R = Et, R¹ = CH₃; 2bb: R = Et, R¹ = Cl] and {[Et₂AlOC(C₆H₅)CH₂S(O)₂(p-ClC₆H₄]∙Et₃Al}_n 3bb were obtained. These complexes in the solid state have a dimeric structure, while in solutions, they appear as equilibrium monomer–dimer mixtures. The hydrolysis of both the isolated 2aa, 2ab, 2ba, 2bb and 3bb and the postreaction mixtures quantitatively leads to pure racemic β-hydroxy sulfones. Hydroalumination reaction of β-keto sulfones with alkyl aluminum compounds and subsequent hydrolysis of the complexes is a simple and very efficient method of β-hydroxy sulfones synthesis.     

Cu(II) and Pd(II) complexes of N-(2-hydroxybenzyl)aminopyridines

N-(2-Hydroxybenzyl)aminopyridines (Lⁱ) react with Cu(II) and Pd(II) ions to form complexes in the compositions Cu(Lⁱ)₂(CH₃COO)₂ · nH₂O (n = 0, 2, 4), Pd(Lⁱ)₂Cl₂ · nC₂H₅OH (n = 0, 2) and Pd(L²)₂Cl₂ · 2H₂O. In the complexes, the ligands are neutral and monodentate which coordinate through pyridinic nitrogen. Crystal data of the complexes obtained from 2-amino pyridine derivative have pointed such a coordinating route and comparison of the spectral data suggests the validity of similar complexation modes of other analog ligands. Cu(II) complex of N-(2-hydroxybenzyl)-2-aminopyridine (L¹), [Cu(L¹)₂(CH₃COO)₂] has slightly distorted square planar cis-mononuclear structure which is built by two oxygen atoms of two monodentate carboxylic groups disposed in cis-position and two nitrogen atoms of two pyridine rings. The remaining two oxygen atoms of two carboxylic groups form two Cu and H bridges containing cycles which joint at same four coordinated copper(II) ion. IR and electronic spectral data and the magnetic moments as well as the thermogravimetric analyses also specify on mononuclear octahedric structure of complexes [Cu(L²)₂(CH₃COO)₂ · 2H₂O] and [Cu(L³)₂(CH₃COO)₂ · 4H₂O] where L² and L³ are N-(2-hydroxybenzyl)-2- or 3-aminopyridines, respectively.     

Preparation and coordination chemistry of Ph2P(CH2)nNHPiPr2 (n=2, 3)

Unsymmetrical diphosphine ligands of the type Ph₂P(CH₂)_nNHPPrⁱ ₂ [n=2 (1), 3 (2)] have been obtained by reacting the appropriate (diphenylphosphino)alkylamine, Ph₂P(CH₂)_nNH₂ with chlorodi-iso-propylphosphine, in the presence of triethylamine. Reaction of Ph₂P(CH₂)₂NHPPrⁱ ₂ with PdCl₂(PhCN)₂, PtCl₂(PhCN)₂, PtMe₂(cod) and PtClMe(cod), NiCl₂·6H₂O and Fe(CO)₂(η⁵-C₅H₅)I gives the corresponding chelate complexes, PdCl₂L, PtX₂L, NiCl₂L and Fe(CO)(η⁵-C₅H₅)L. Reaction of Ph₂P(CH₂)₃NHPPrⁱ ₂ with PtCl₂(PhCN)₂, PtMe₂(cod) and PdCl₂(PhCN)₂ yields the chelate complexes and reaction with PtClMe(cod) led to a 50:50 mixture of chelate isomers.     

Halogen-magnesium exchange of m- and p-iodo or bromo-arenes bearing ortho-directing groups through ate complexes

m- or p-Iodinated, or brominated ω-phenoxyalcohols and phenols as well as halogenated indoles were subjected to halogen-magnesium exchange reactions with isopropyl magnesium bromide (ⁱPrMgBr) or isopropyl magnesium di-n-butyl lithium ate complexes (ⁱPrMgⁿBu₂Li) at −78 °C to room temperature. ⁱPrMgⁿBu₂Li proved superior to prevent ortho-metallation of these substituted arenes.     

Ring-opening polymerization of l-lactide by organotin(IV)alkoxides,R2Sn(OPr)2: Estimation of the activation parameters

The ring-opening polymerization of l-lactide, l-LA, to give poly-l-lactide by R₂Sn(OPrⁱ)₂ compounds, where R = Buⁿ and p-XC₆H₄ (X = CF₃, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in ΔH^≠ as a function of R with all the values falling within the range 11 ± 2 kcal mol⁻¹. The entropy of activation, ΔS^≠, is consistently large and negative, −50 ± 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph₂Sn(OPrⁱ)₂, (p-FC₆H₄)₂Sn(OPrⁱ)₂ and (p-Me₂NC₆H₄)₃SnOPrⁱ are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPrⁱ ligands.     

Cationic η-benzyl nickel compounds with diphosphine ligands as catalyst precursors for ethylene oligomerization/polymerization: influence of the diphosphine bite angle

The oligomerization and/or polymerization of ethylene catalyzed by the cationic η³-benzylcomplexes [Ni(η³-CH₂C₆H₄-p-CF₃)(P-P)]⁺ BPh₄⁻ (P-P=ⁱPr₂P(CH₂)_nPⁱPr₂, n=1-3) have been studied. The activity of these single component catalysts depends on the length of the (CH₂)_n bridge of the diphosphine ligand. Thus, the dippm derivative (n=1) displays higher activity than compounds of the dippe (n=2) or dippp (n=3) ligands. The molecular weight of the products is also a function of n, and varies in the order dippm > dippe > dippp, with the former two catalysts giving rise to low molecular weight polyethylenes and the latter to oligomers.     

Synthesis and structure of [Cp2Zr(OPr)(HOPr)] and its activity in the polymerisation of propene oxide

The reaction of Cp₂Zr(OPrⁱ)₂ with [H(OEt₂)₂][H₂N{B(C₆F₅)₃}₂] in dichloromethane at room temperature gives [Cp₂Zr(OPrⁱ)(HOPrⁱ)]⁺[H₂N{B(C₆F₅)₃}₂]⁻ · Et₂O in high yield. The crystal structure is reported. The complex contains a short Zr-alkoxide and a longer Zr-alcohol bond; the OH group of the coordinated isopropanol is hydrogen-bonded to a diethyl ether molecule. The complex initiates the polymerisation of propylene oxide, most probably via a cationic mechanism.     

Synthesis and characterization of some organotin(IV) adducts containing a related series of pyridines: Crystal structure of [SnMe2Cl2(bu2bpy)]

Organotin(IV) complexes of [SnR_(4−n)Cl_n] (n = 2, R = Me, ⁿBu; n = 1, R = Ph) react with the bidentate pyridyl ligand 4,4′-di-tert-butyl-2,2′-bipyridine (bu₂bpy) to give hexa-coordinated adducts with the general formula [SnR_(4−n)Cl_n(bu₂bpy)]. However, the reaction of these organotin(IV) complexes with the corresponding monodentate ligand 4-tert-butylpyridine (bupy) resulted in the formation of the hexa-coordinated complex [SnMe₂Cl₂(bupy)₂] and the penta-coordinated complexes [SnR_(4−n)Cl_n(bupy)] (n = 2, R = ⁿBu; n = 1, R = Ph). Moreover, the reaction of the above organotin(IV) complexes with 4,4′-trimethylenedipyridine (tmdp) yields hexa-coordinated adducts with the general formula [SnR₂Cl₂(tmdp)] (R = Me, ⁿBu) and the penta-coordinated complex [ClPh₃Sn-μ-(tmdp)SnPh₃Cl] in the solid state. The resulting complexes have been characterized by multinuclear NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and elemental analysis. NMR data shows that the triphenyltin(IV) adducts are not stable in solution and dissociate to give tetra-coordinated tin(IV) complexes. The X-ray crystal structure determination of [SnMe₂Cl₂(bu₂bpy)] reveals that the tin atom is hexa-coordinated in an octahedral geometry with a trans-[SnMe₂] configuration.     

Synthesis and coordination chemistry of tetrabutyldithioimidodiphosphinates

Butyl substituted imidodithiophosphinates R₂P(S)NP (S)R′₂ (R=ⁿBuⁱBu^sBuR′=ⁿBuⁱBu^sBu) have been synthesised via an HBr elimination reaction between R₂P(S)NH₂ and R′₂P(S)Br The compounds were characterised spectroscopically Crystallographic and spectroscopic studies reveal ⁿBu₂P(S)NHP(S)ⁿBu₂ and ^sBu₂P(S)NHP(S)ⁱBu₂ to be hydrogen bonded transoid dimers and ⁱBu₂P(S)NHP(S)ⁱBu₂ to be a transoid hydrogen bonded chain Reactions of the imidodithiophosphinates with ZnCl₂ or MCl₂COD gave the coordination complexes M[R₂P(S)NP (S)R′₂]₂ (R=ⁿBuⁱBu^sBuR′=ⁿBuⁱBu^sBuM=ZnPd: R=ⁿBuⁱBu^sBuPt).     

Heterobimetallic complexes of lanthanide and lithium metals with dianionic guanidinate ligands: Syntheses, structures and catalytic activity for amidation of aldehydes with amines

Reactions of triguanidinate lanthanide complexes Ln[(ⁱPrN)(NC₆H₄p-Cl)C(NHⁱPr)]₃ (Ln = Nd, Y) with 3 equiv. of n-BuLi gave [Li(THF)(DME)]₃Ln[μ-η²η¹ (ⁱPrN)₂C(NC₆H₄p-Cl)]₃, which represents the first structurally characterized complexes of lanthanide and lithium metals with dianionic guanidinate ligands. The Nd complex was found to be an effective catalyst for amidation of aldehydes with amines under mild conditions with a wide scope of substrates.     

Synthesis and structure of chiral-at-metal complexes with the ligand (S)-2-[(Sp)-2-(diphenylphosphino)ferrocenyl]-4-isopropyloxazoline

Half-sandwich complexes of formula [(ηⁿ-ring)MClL]PF₆ [L = (S)-2-[(S_p)-2-(diphenylphosphino)ferrocenyl]-4-isopropyloxazoline; (ηⁿ-ring)M = (η⁵-C₅Me₅)Rh; (η⁵-C₅Me₅)Ir; (η⁶-p-MeC₆H₄iPr)Ru; (η⁶-p-MeC₆H₄iPr)Os] have been prepared and spectroscopically characterised. The molecular structures of the rhodium and iridium compounds have been determined by X-ray crystallography. The related solvate complexes [(η⁵-C₅Me₅)ML(Me₂CO)]²⁺ (M = Rh, Ir) are active catalysts for the Diels-Alder reaction between methacrolein and cyclopentadiene.     

New effective reagent [Cp2ZrH2 · ClAlEt2]2 for alkene hydrometallation

New bimetallic complex [Cp₂ZrH₂ · ClAlEt₂]₂ (1) was synthesized, and its reactivity in hydrometallation reaction with the following alkenes was studied: hept-1-ene, okt-1-ene, α-methylstyrene, (1S)-β-pinene, (+)-camphene. Complex 1 shows the highest reactivity among the other known Al,Zr-bimetallic complexes: [Cp₂ZrH₂ · ClAlBuⁱ₂]₂ (2), [Cp₂ZrH₂ · AlEt₃]₂ (3), [Cp₂ZrH₂ · AlBuⁱ₃]₂ (4) and [Cp₂ZrH₂ · HAlBuⁱ₂] (5) as well as organoaluminium compounds (OAC): ⁱBu₂AlH, ⁱBu₃Al and ⁱBu₂AlCl in presence of Zr catalysts. Chlorine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-β-pinene ? (+)-camphene < α-methylstyrene < oct-1-ene < hept-1-ene. Hydrometallation of (1S)-β-pinene and its subsequent oxidation with I₂ run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation is less than that for (1S)-β-pinene, and the reaction gives predominately endo-camphanol.     

Ti(II)-mediated domino cyclization of 2-functionalized 1-halo-2,n-enynes (n = 7, 8) to bicyclic compounds

The reaction of 2-functionalized 1-halo-2,n-enynes (n = 7 or 8) with a divalent titanium reagent, Ti(O-i-Pr)₄/2i-PrMgCl, proceeded in a domino fashion to afford bicyclic compounds in good yields.     

Synthesis and structural characterization of gallium and indium complexes obtained from redistribution reactions of mixed chalcogen-imidodiphosphinate ligands

The ionic complex [Ga{N(SPⁱPr₂)(SePⁱPr₂)-S, Se}₂]⁺[GaCl₄]⁻ (5) was prepared by a ligand redistribution process from the mono-chelate [Cl₂Ga{N(SPⁱPr₂)(SePⁱPr₂)-S, Se}] (3) complex in benzene. A similar phenomenon was observed for the heavier indium homologues, where the neutral complexes [ClIn{N(SPⁱPr₂)(SePⁱPr₂)-S, Se}₂] (7) and [ClIn{N(OPⁱPr₂)(SPⁱPr₂)-O, S}₂] (8) were isolated along with InCl₃ as the main reaction by-product. Complexes 5, 7 and 8 were characterized by single-crystal X-ray structural analysis.     

Selective synthesis of monomeric or dimeric titanatranes via fine tuning in triethanolateamine ligand

Monomeric titanatrane i-PrOTi(OCMe₂CH₂)₃N (1) and dimeric titanatranes [i-PrOTi(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]₂ (n = 1, 2; n = 2, 3) were synthesized by the reaction of Ti(O-i-Pr)₄ with a series of triethanolateamines such as (OCH₂CH₂)_nN(CH₂CMe₂O)_3−n³⁻ (n = 0, Lig¹; n = 1, Lig²; n = 2, Lig³), which vary by the number of CMe₂ groups adjacent to a OH functionality from 3 (Lig¹H₃) to 2 (Lig²H₃) to 1 (Lig³H₃). The resultant titanatranes 1–3 have been characterized by solution ¹H and ¹³C{¹H} NMR and their solid state structures have been determined by X-ray crystallography. Whereas compound 1 is monomeric in the solid state, compounds 2 and 3 are dimeric, due to the reduction of the steric congestion in the vicinity of the Ti.     

Reaction of 1,2-dibromoethane with primary amines: formation of N,N′-disubstituted ethylenediamines RNH-CH2CH2-NHR and homologous polyamines RNH-[CH2CH2NR]n-H

The reaction of primary amines RNH₂ (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N′-disubstituted ethylenediamines R-NH-CH₂CH₂-NH-R (1) in yields ranging from 10% (1a; R=Me) to 70% (1d, R=tBu; 1e, R=Ph). Piperazines and N-substituted polyethyleneimines were identified (¹H NMR, ¹³C NMR and EI-MS) as side products of the reaction and isolated by fractional distillation. The piperazines 2 are formed in yields of 3-10% and can be separated from the diamines 1 in all cases, except for R=Me and Ph. The polyamine homologues RNH-[CH₂CH₂NR]_n-H (3-5) were isolated in yields ranging from 0.1% (n=4, R=iPr) to 14% (n=2, R=iPr). The yields of 1 increase with the size of the substituent R, no obvious trend exists for the yields of the side products.     

Palladium(I) carbonyl carboxylate clusters cyclo-[Pd2(μ-CO)2(μ-OCOR)2]n (n = 2 or 3): Structure and reactivity

The interaction of palladium(+1) cluster Pd₄(μ-CO)₄(μ-OAc)₄ with saturated and unsaturated carboxylic acids was studied. It was found, that the substitution of acetates groups on others carboxylates leads to the clusters with different nuclearity. Palladium(+1) carbonyl carboxylate complexes of composition [Pd(μ-CO)(μ-OCOR)]_n, where R = CF₃, CCl₃, CH₂Cl, MeCH = CMe, Me, Prⁱ, Bu, Buⁱ, Bu^tert, n-C₅H₁₁ and n = 4 or 6 were synthesized. According to X-ray data all clusters possess cyclic planar metal cores with alternate pairs of μ-carbonyl and μ-carboxylate ligands. The presence of bulky alkyl fragments in the carboxylate ligand increases the nuclearity of the cluster compared to that of the starting palladium(+1) carbonyl acetate of composition Pd₄(μ-CO)₄(μ-OAc)₄ due, apparently, to steric hindrance.     

Isonitrile ligand properties as studied by He I/He II photoelectron spectroscopy

A new series of isonitrile-substituted cobalt tricarbonyl nitrosyl (Co(CO)₂(NO)CNR, R = Me, Et, ⁿPr, ⁱPr, ⁿBu, ⁿPe, CH₂Si(CH₃)₃) has been synthesized, and their He I ultraviolet photoelectron spectra are reported. The assignment of the bands in the low energy part of the spectra was performed with the aid of DFT calculations. The first vertical ionization energies of the complexes were found to be 7.73 (CNMe), 7.58 (CNEt), 7.59 (CNⁿPr), 7.70 (CNⁿBu), 7.67 (CNⁿPe), 7.77 (CNⁱPr), and 7.54 ± 0.03 eV (CNCH₂Si(CH₃)₃). In the case of ⁿPr- and CH₂Si(CH₃)₃- substitutions, He II photoelectron spectra were also recorded. The relative importance of electronic and steric effects of the isonitrile ligands, as a function of the size of group –R, is discussed.     

Gallium and indium dithiocarboxylates: Synthesis, spectroscopic characterization and structure of [MeGa(S2Ctol)2]

Several gallium and indium dithiocarboxylate complexes of the type [Me_nM(S₂CR)_3−n] (M = Ga, In; n = 0, 1, 2; R = phenyl (Ph), p-tolyl (tol), mesityl (Mes)) have been synthesized. These complexes were characterized by elemental analysis, IR, UV-vis and NMR (¹H,¹³C{¹H}) spectroscopy. Structure of [MeGa(S₂Ctol)₂] was established by X-ray crystallography. The gallium atom adopts a distorted five coordinate geometry which is intermediate between trigonal bipyramidal and square pyramidal configurations. The complex [Me₂InS₂Ctol] underwent a two-step thermal decomposition leading to the formation of tetragonal β-In₂S₃.