Biotransformation of 3-azidomethyl-4-phenyl-3-buten-2-one and analogs by Saccharomyces cerevisiae: New evidence for an SN2′ mechanism

(Z)-3-XCH₂-4-(C₆H₅)-3-buten-2-one enones (X = SCN, N₃, SO₂Me, OC₆H₅) were synthesized and submitted to biotransformations using whole Saccharomyces cerevisiae cells. The enone (X = SCN) produced (R)-4-(phenyl)-3-methylbutan-2-one (R)-6 with 93% ee and enones (X = N₃, SO₂Me, OC₆H₅) yielded a mixture of (R)-6 and the corresponding CC bond reduction products. Biotransformation with enone (X = N₃) mediated by Saccharomyces cerevisiae resulted in two products via two different routes: (i) the ketone (R)-4-azido-3-benzylbutan-2-one in 28% yield and with >99% ee by CC bond reduction; (ii) ketone (R)-6 in 51% yield and with 95% ee via cascade reactions beginning with azido group displacement by the formal hydride from flavin mononucleotide in an S_N2′ type reaction followed by reduction of the newly formed CC bond.     

Supramolecular chemistry and the control of the crystallization behavior by the choice of the counter-ion. Part 11. The stereochemistry and crystallization architecture of [(tren)Co(NO2)2]A (I), [(tren)Co(ox)]A (II), [(en)2Co(ox)]A (III) and [trans-(pn)2Co(NO2)2]A (IV), with A = [trans-(NH3)2Co(NO2)4]

In continuation of studies carried out previously [I. Bernal, Inorg. Chim. Acta 96 (1985) 99; I. Bernal, Inorg. Chim. Acta (1986) 121; I. Bernal, E.O. Schlemper, C.K. Fair, Inorg. Chim. Acta 115 (1986) 25; I. Bernal, Inorg. Chim. Acta 101 (1985) 175; I. Bernal, J. Cetrullo, J. Coord. Chem. 20 (1989) 237], we have now expanded the nature and number of cations associated with the [trans-(NH₃)₂Co(NO₂)₄] anion in order to better document when, and how, this helical propeller species crystallizes as a conglomerate.[(tren)Co(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] (I) crystallizes as a racemate in space group P2₁/n with cell constants of a = 15.8900(2), b = 19.7800(3), c = 26.6200(4) Å, β = 101.970(3)°, z = 15.[(tren)Co(ox)][trans-(NH₃)₂Co(NO₂)₄] (II) crystallizes as a racemate in space group I2/a with cell constants of a = 21.592(11), b = 7.050(4), c = 26.46(2) Å, β = 93.09(6)°, z = 8.[(en)₂Co(ox)][trans-(NH₃)₂Co(NO₂)₄] (III) crystallizes as a racemate in space group P2₁/n with cell constants of a = 6.4740(1), b = 22.8950(6), c = 13.1660(3) Å, β = 97.3310(10)°, z = 4.[trans-(pn)₂Co(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] (IV) also crystallizes as a racemate in space group P(¯1; no. 2) with cell constants of a = 6.508(2), b = 8.829(5), c = 9.851(5) Å, α = 72.84(2), β = 80.15(3), and γ = 81.45(6)°, z = 1.The most notable results are as follows: (1) all four compounds studied are racemates unlike the previously studied [cis-Co(en)₂(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] [I. Bernal, Inorg Chim Acta 101 (1985) 175] (V) and K[trans-(NH₃)₂Co(NO₂)₄] (VI) that crystallize as conglomerates. Nevertheless, they share certain crystalline features, which are readily observed in their packing diagrams.In all the four cases the new data were collected at 295 K and 120 K, using Mo Kα radiation; the former with a Nonius CAD-4 diffractometer and the latter with a Nonius CCD instrument. Of primary interest to us are the changes in packing caused by repeated changes in the charge compensating cations. Comparisons with the packing observed previously in [cis-Co(en)₂(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] (V) and K[trans-(NH₃)₂Co(NO₂)₄] (VI) are made since, at the time of publications of those early papers, no detailed study of the packing characteristics of these anions was published and the existing graphic software were primitive compared with the current packages. This oversight is remedied below.     

Dimeric and monomeric palladium(II) parent-amido (NH2) complexes: Synthesis,characterization, and reactivity

The treatment of [PdL₃(NH₃)]OTf (L₃ = (PEt₃)₂(Ph) (1), (2,6-(Cy₂PCH₂)₂C₆H₃) (3)) with NaNH₂ in THF afforded dimeric and monomeric parent-amido palladium(II) complexes with bridging and terminal NH₂, respectively, anti-[Pd(PEt₃)(Ph)(μ-NH₂)]₂ (2) and Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂) (4). The dimeric complex 2 crystallizes in the space group P2₁/n with a = 13.228(2) Å, b = 18.132(2) Å, c = 24.745(2) Å, β = 101.41(1)°, and Z = 4. It has been found that there are two crystallographically independent molecules with Pd(1)–Pd(2) and Pd(3)–Pd(4) distances of 2.9594 (10) and 2.9401(9) Å, respectively. The monomeric amido complex 4 protonates from trace amounts of water to give the cationic ammine species [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₃)]⁺. Complex 4 reacts with diphenyliodonium triflate ([Ph₂I]OTf) to give aniline complex [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂Ph)]OTf (5). Reaction of 4 with dialkyl acetylenedicarboxylate (DMAD, DEAD) yields diastereospecific palladium(II) vinyl derivative (Z)–(Pd(Cy₂PCH₂)₂C₆H₃)(CR = CR(NH₂)) (R = CO₂Me (6a), CO₂Et (6b)). Reacting complexes 6a and 6b with p-nitrophenol produces (Pd(Cy₂PCH₂)₂C₆H₃)(OC₆H₄–p-NO₂) (8) and cis-CHR = CR(NH₂), exclusively.     

Effects of bulky substituent groups on the Si–Si triple bonding in RSiSiR and the short Ga–Ga distance in Na2[RGaGaR]: A theoretical study

The steric and electronic effects of bulky aryl and silyl groups on the Si–Si triple bonding in RSiSiR and the short Ga–Ga distance in Na₂[RGaGaR] are investigated by density functional calculations. As typical bulky groups, Tbt = C₆H₂-2,4,6-{CH(SiMe₃)₂}₃, Ar′ = C₆H₃-2,6-(C₆H₃-2,6-iPr₂)₂, Ar¹ = C₆H₃-2,6-(C₆H₂-2,4,6-iPr₃)₂, SiMe(SitBu₃)₂, and SiiPrDis₂ (Dis = CH(SiMe₃)₂) are investigated and characterized. The importance of large basis sets is emphasized for density functional calculations.     

Copper(I) complexes of heterocyclic thiourea ligands

The coordination of heterocyclic thiourea ligands (L = N-(2-pyridyl)-N′-phenylthiourea (1), N-(2-pyridyl)-N′-methylthiourea (2), N-(3-pyridyl)-N′-phenylthiourea (3), N-(3-pyridyl)-N′-methylthiourea (4), N-(4-pyridyl)-N′-phenylthiourea (5), N-(2-pyrimidyl)-N′-phenylthiourea (6), N-(2-pyrimidyl)-N′-methylthiourea (7), N-(2-thiazolyl)-N′-methylthiourea (8), N-(2-benzothiazolyl)-N′-methylthiourea (9), N,N′-bis(2-pyridyl)thiourea (10) and N,N′-bis(3-pyridyl)thiourea (11)) with CuX (X = Cl, Br, I, NO₃) has been investigated. CuX:L product stoichiometries of 1:1–1:5 were found, with 1:1 being most common. X-ray structures of four 3-coordinate mononuclear CuXL₂ complexes (CuCl(6)₂, CuCl(7)₂, CuBr(6)₂, and CuBr(9)₂) are reported. In contrast, CuBr(1)₂ is a 1D sulfur-bridged polymer. CuIL structures (L = 7, 8) are 1D chains with corner-sharing Cu₂(μ-I)₂ and Cu₂(μ-S)₂ units, and CuCl(10) is a 2D network having μ-Cl and N-/S-bridging L. Two [CuL₂]NO₃ structures are reported: a mononuclear 4-coordinate copper complex with chelating ligands (L = 10) and a 1D link-chain with N-/S-bridging L (L = 3). Two ligand oxidative cyclizations were encountered during crystallization. CuI crystallized with 6 to produce zigzag ladder polymer [(CuI)₂(12)]·½CH₃CN (12 = N-(pyrimidin-2-yl)benzo[d]thiazol-2-amine) and CuNO₃ crystallized with 10 to form [Cu₂(NO₃)(13)₂(MeCN)]NO₃ (13 = dipyridyltetraazathiapentalene).     

Synthesis, structural characterization of benzimidazole-functionalized Ni(II) and Hg(II) N-heterocyclic carbene complexes and their applications as efficient catalysts for Friedel-Crafts alkylations

[Ni(L₁)₂](PF₆)₂ (3a, L₁ = 3-(1-ethyl-1H-benzimidazol-2-yl)methyl)-1-((6-methylpyridin-2-yl)methyl)imidazolyl-idene), [Ni(L₂)₂(CH₃CN)](PF₆)₂ (3b, L₂ = 3-(1-ethyl-1H-benzimidazol-2-yl)methyl)-1-((6-methylpyridin-2-yl)-methyl)benzimidazolylidene), and [Hg(L₁)₂(CH₃CN)₂](PF₆)₂ (4) have been successfully prepared and fully characterized by NMR, ESI-MS spectroscopy, and X-ray diffraction analysis. The nickel complexes reveal a square-planar structure with two carbene ligands and benzimidazole groups at the cis configuration. The nickel complex 3b has been proved to be a highly efficient catalyst for Friedel-Crafts alkylation of indoles with β-nitrostyrenes at room temperature in moderate-to-excellent yields. The crystal packing structure of 4 shows that double-stranded 1D supramolecular chains are formed by inter-chain benzimidazole rings and pyridine rings face-to-face π-π stacking interactions.     

Synthesis,characterization and antibacterial activity of some new triphenyltin(IV) sulfanylcarboxylates: Crystal structure of [(SnPh3)2(p-mpspa)], [(SnPh3)2(cpa)] and [(SnPh3)2(tspa)(DMSO)]

Five new triphenyltin(IV) sulfanylcarboxylates of the general formula [(SnPh₃)₂L] (L = pspa, tspa, fspa, p-mpspa or cpa, where p = 3-(2-phenyl)-, t = 3-(2-thienyl)-, f = 3-(2-furyl)-, p-mp = 3-(4-methoxyphenyl)-, spa = 2-sulfanylpropenoato and cpa = 2-cyclopentilyden-2-sulfanylacetate) have been synthesized by reacting triphenyltin(IV) hydroxide with the corresponding acid in ethanol/acetone. The complexes have been characterized by elemental analysis and mass spectrometry and by vibrational and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopies. In the case of [(SnPh₃)₂(p-mpspa)] and [(SnPh₃)₂(cpa)], X-ray structural studies showed that in both compounds each Sn atom is coordinated to three phenyl C atoms and to one S or O atom of the bridge ligand L. All five complexes are active against strains of Staphylococcus aureus, but are inactive against Escherichia coli and Pseudomonas aeruginosa. From a solution of [(SnPh₃)₂(tspa)] in DMSO-d₆ the new complex [(SnPh₃)₂(tspa)(DMSO)] was isolated. The single-crystal X-ray diffractometric study of this complex is also reported, showing that both Sn atoms are bridged by the tspa ligand, whereas the molecule of DMSO is coordinated to one of the tin atoms via the oxygen atom.     

Synthesis, structure, and catalytic activity of organolanthanides with chiral biphenyl-based tridentate amidate ligands

Four new chiral organolanthanide amidate complexes have been readily prepared in good yields via silylamine elimination reaction between Ln[N(SiMe₃)₂]₃ (Ln = Sm, Y, Yb) and chiral amidate ligands, (R)-2-(mesitoylamino)-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl (1H) and (R)-2-(mesitoylamino)-2′-dimethylamino-6,6′-dimethyl-1,1′-biphenyl (2H). The steric effect of the ligand coupled with the size effect of the lanthanide ion plays an important role in complex formation. For example, treatment of 1H with half equiv of Sm[N(SiMe₃)₂]₃ gives the C₂-symmetric bis-ligated amidate complex (σOMe:κO:κN-1)₂SmN(SiMe₃)₂ (3) in 75% yield, while reaction of 1H or 2H with half equiv of Ln[N(SiMe₃)₂]₃ (Ln = Y, Yb) affords the C₁-symmetric bis-ligated amidate complexes [(κO:κN-1)(σOMe:κO:κN-1)]LnN(SiMe₃)₂ (Ln = Y (4), Yb (5) and the C₁-symmetric mono-ligated amidate complex (σNMe₂:κO:κN-2)Y[N(SiMe₃)₂]₂ (6), respectively, in good yields. These organolanthanide amidate complexes have been characterized by various spectroscopic techniques, elemental analyses, and X-ray diffraction analyses. They are active catalysts for asymmetric hydroamination/cyclization of aminoalkenes and ring-opening polymerization of rac-lactide, affording cyclic amines in excellent conversions with good ee values and isotactic-rich polylactides, respectively.     

Synthesis,characterization and crystal structures of 2-[(E)-2-(4-hydroxy-3,5-dimethylphenyl)-1-diazenyl]benzoic acid and its polymeric and monomeric triorganotin(IV) complexes

Three triorganotin(IV) complexes of composition R₃SnLH (R = Me, Bu and Ph and LH = 2-[(E)-2-(4-hydroxy-3,5-dimethylphenyl)-1-diazenyl]benzoate) have been synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, and IR spectroscopic techniques in combination with elemental analysis. The crystal structures of the carboxylate ligand HO₂CC₆H₄{NN(C₆H₂-4-OH-3,5-(CH₃)₂)}-o in its neutral form and three triorganotin(IV) complexes, viz., polymeric (R₃Sn[O₂CC₆H₄{N–N(H)(C₆H₂-4-O-3,5-(CH₃)₂)}-o])_n (R = Me (1) and Bu (2)) and monomeric Ph₃Sn[O₂CC₆H₄{N–N(H)(C₆H₂-4-O-3,5-(CH₃)₂)}-o] (3) complexes are reported. The polymeric complexes 1 and 2 exist as extended chains in which the LH-bridged Sn-atoms adopt a trans-R₃SnO₂ trigonal bipyramidal configuration with R groups in the equatorial positions and the axial sites occupied by an oxygen atom from the carboxylate ligand and the phenoxide O atom of the next carboxylate ligand. The Sn atom in complex 3 has a distorted tetrahedral geometry. In all three complexes, the carboxylate ligand is in the zwitterionic form with the phenolic proton moved to the nearby azo nitrogen atom, in contrast to the free carboxylic acid ligand which is in the azo form.     

Synthesis,characterization and crystal structures of 2-[(E)-2-(4-hydroxy-3,5-dimethylphenyl)-1-diazenyl]benzoic acid and its polymeric and monomeric triorganotin(IV) complexes

Three triorganotin(IV) complexes of composition R₃SnLH (R = Me, Bu and Ph and LH = 2-[(E)-2-(4-hydroxy-3,5-dimethylphenyl)-1-diazenyl]benzoate) have been synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, and IR spectroscopic techniques in combination with elemental analysis. The crystal structures of the carboxylate ligand HO₂CC₆H₄{NN(C₆H₂-4-OH-3,5-(CH₃)₂)}-o in its neutral form and three triorganotin(IV) complexes, viz., polymeric (R₃Sn[O₂CC₆H₄{N–N(H)(C₆H₂-4-O-3,5-(CH₃)₂)}-o])_n (R = Me (1) and Bu (2)) and monomeric Ph₃Sn[O₂CC₆H₄{N–N(H)(C₆H₂-4-O-3,5-(CH₃)₂)}-o] (3) complexes are reported. The polymeric complexes 1 and 2 exist as extended chains in which the LH-bridged Sn-atoms adopt a trans-R₃SnO₂ trigonal bipyramidal configuration with R groups in the equatorial positions and the axial sites occupied by an oxygen atom from the carboxylate ligand and the phenoxide O atom of the next carboxylate ligand. The Sn atom in complex 3 has a distorted tetrahedral geometry. In all three complexes, the carboxylate ligand is in the zwitterionic form with the phenolic proton moved to the nearby azo nitrogen atom, in contrast to the free carboxylic acid ligand which is in the azo form.     

Influence of multidentate N-donor ligands on highly electrophilic zinc initiator for the ring-opening polymerization of epoxides

A set of multidentate ligands have been synthesized and used to stabilize the putative highly electrophilic zinc species initiating ring-opening polymerization (ROP) of cyclohexene oxide (CHO) and propylene oxide (PO). Reaction of the bidentate C₂-chiral bis(oxazoline) ligand (^R2,R3BOX: R₂ = (4S)-tBu, R₃ = H (a); R₂ = (4S)-Ph, R₃ = H (b); R₂ = (4R)-Ph, R₃ = (5S)-Ph (c)) with Zn(R₁)₂ (R₁ = Et (1), Me (2)) led to the heteroleptic three-coordinate complexes (^R2,R3BOX)ZnR₁, 1a-c and 2a, which were isolated in 92-96% yield. Next, two pyridinyl-functionalized N-heterocyclic carbene (NHC) ligands have been designed and synthesized: the 1,3-bis(2-pyridylmethyl)imidazolinium salt (d) and the protected NHC adduct 2-(2,3,4,5,6-pentafluorophenyl)-1,3-bis(2-pyridylmethyl)imidazolidine (e). The reaction of ligands d and e with ZnEt₂ led directly to the formation of (NHC)ZnEt(Cl) 3d complex with ethane elimination and the adduct (NHC-C₆F₅(H))ZnEt₂4e, respectively, in high yield. In situ combinations of selected complexes 1a-c, 3d and 4e with B(C₆F₅)₃ (1 or 2 equivalents) give active systems for ROP, with high productivity (3.3-5.9 10⁶ g_polym. mol_Zn⁻¹ h⁻¹) and high molecular weight (M_n up to 132 10³ g mol⁻¹) for CHO polymerization. Although the in situ B(C₆F₅)₃-activated zinc species were not isolated, the sterically demanding BOX ligands (1c > 1b > 1a) and functionalized NHC ligands seem to enhance the stability of highly electrophilic zinc complexes over ligand redistribution, allowing a better control of the cationic ROP as reflected particularly for 3d and 4e complexes by their respective efficiency (42-88%).     

Formation and isomerization of cis,cis-Ir(H)2(--Ph)(CO)(PPh3)2 and cis,cis-Ir(H)(--Ph)2(CO)(PPh3)2 in oxidative addition of hydrogen and phenylacetylene to trans-Ir(CO)(--Ph)(PPh3)2

Oxidative addition of H–R (H--Ph and H₂) to trans-Ir(--Ph)(CO)(PPh₃)₂ (2) gives the initial products, cis, cis-Ir(H)(--Ph)₂(CO)(PPh₃)₂ (3a) and cis, cis-Ir(H)₂(--Ph)(CO)(PPh₃)₂ (3b), respectively. Both cis-bis(PPh₃) complexes, 3a and 3b undergo isomerization to give the trans-bis(PPh₃) complexes, trans, trans-Ir(H)(--Ph)₂(CO)(PPh₃)₂ (4a) and cis, trans-Ir(H)₂(--Ph)(CO)(PPh₃)₂ (4b). The isomerization, 3b→4b is first order with respect to 3b with k₁=6.37×10⁻⁴ s⁻¹ at 25°C under N₂ in CDCl₃. The reaction rate (k₁) seems independent of the concentration of H₂. A large negative entropy of activation (ΔS^≠=−24.9±5.7 cal deg⁻¹ mol⁻¹) and a relatively small enthalpy of activation (ΔH^≠=14.5±3.3 kcal mol⁻¹) were obtained in the temperature range 15∼35°C for the isomerization, 3b→4b under 1 atm of H₂.     

Ruthenium piano-stool complexes bearing imidazole-based PN ligands

A variety of piano-stool complexes of cyclopentadienyl ruthenium(II) with imidazole-based PN ligands have been synthesized starting from the precursor complexes [CpRu(C₁₀H₈)]PF₆, [CpRu(NCMe)₃]PF₆ and [CpRu(PPh₃)₂Cl]. PN ligands used are imidazol-2-yl, -4-yl and -5-yl phosphines.Depending on the ligand and precursor different types of coordination modes were observed; in the case of polyimidazolyl PN ligands these were κ¹P-monodentate, κ²P,N-, κ²N,N- and κ³N,N,N- chelating and μ-κP:κ²N,N-brigding. The solid-state structures of [CpRu(1a)₂Cl ]·H₂O (5^.H₂O) and [{CpRu(μ-κ²-N,N-κ’¹-P-2b)}₂](C₆H₅PO₃H)₂(C₆H₅PO₃H₂)_2, a hydrolysis product of the as well determined [{CpRu(2b)}₂](PF₆)₂^.2CH₃CN (7b^.2CH₃CN) were determined (1a = imidazol-2-yldiphenyl phosphine, 2b = bis(1-methylimidazol-2-yl)phenyl phosphine, 3a = tris(imidazol-2-yl)phosphine). Furthermore, the complexes [CpRu(L)₂]PF₆ (L = imidazol-2-yl or imidazol-4-yl phosphine) have been screened for their catalytic activity in the hydration of 1-octyne.     

The stereocontrolled synthesis of polyfunctional organosulfur compounds via chiral azetidinium salts and epoxyamines

The stereocontrolled synthesis of functionalized organosulfur compounds of a general formula: Bn₂NCH(CH₃)CH(OH)CH₂SX [where: X = SO₃Na or SP(S)(OR)₂] was achieved by a regioselective opening of enantiomerically >98% pure (2S,3R)- and (2S,3S)-N,N-dibenzyl-2-hydroxy-3-methylazetidinium bromides and/or (1R)-[1′(S)-dibenzylamino)ethyl]oxiranes with thiosulfate and dithiophosphate anions. The attack of both nucleophiles was directed exclusively at the less substituted carbon atom of the heterocyclic ring.     

Effect of ortho-substituents on the stereochemistry of 2-(o-substituted phenyl)-1H-imidazoline-palladium complexes

Palladium complexes composed of [Pd(Ln)₂Cl₂] (n = 1, 2, 3, 4, 6), [L5a]₂[PdCl₄] and [Pd(L5b)₂], where L1 = 4,5-dihydro-2-phenyl-1H-imidazole (=2-phenyl-1H-imidazoline), L2 = 2-(o-fluorophenyl)-1H-imidazoline, L3 = 2-(o-methylphenyl)-1H-imidazoline, L4 = 2-(o-tert-butylphenyl)-1H-imidazoline, L5a = 2-(o-hydroxyphenyl)-1H-imidazolinium, L5b = 2-(1H-imidazolin-2-yl)phenolate, and L6 = 2-(o-methylphenyl)-1H-imidazole, were synthesized. Molecular structures of the isolated palladium complexes were characterized by single crystal X-ray diffraction analysis. The effect of ortho-substituents on the phenyl ring on trans-chlorine geometry was noted for complexes [Pd(L1)₂Cl₂] 1a and 1b, [Pd(L2)₂Cl₂] 2 and [Pd(L6)₂Cl₂] 6, whereas cis-chlorine geometry was observed for [Pd(L3)₂Cl₂] 3 and [Pd(L4)₂Cl₂] 4. PdCl₂ reacts with 2-(o-hydroxyphenyl)-1H-imidazoline in DMF to give [L5a]⁺ and [L5b]^- so that [L5a]₂[PdCl₄] 5a and [Pd(L5b)₂] 5b were obtained. In complex 5b, as an N,O-bidentate ligand, two ligands L5b coordinated with the central Pd(II) ion in the trans-form. The coordination of PdCl₂ with 2-(o-hydroxyphenyl)-1H-imidazolines in solution was investigated by NMR spectroscopy.     

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.     

Six-coordinate uranium complexes featuring a bidentate anilide ligand

The synthesis of a new bidentate anilide ligand and four uranium amide complexes utilizing the ligand are reported. The secondary aniline HN[R]Ar_MeL (R = C(CD₃)₂CH₃, Ar_MeL = 2-NMe₂-5-MeC₆H₃) is prepared by condensation of H₂NAr_MeL and acetone-d₆ followed by alkylation of the resulting imine with MeLi. The ligand precursors (Et₂O)Li(N[R]Ar_MeL) and K(N[R]Ar_MeL) are prepared through deprotonation of HN[R]Ar_MeL with n-BuLi and KH, respectively. Treatment of UI₃(THF)₄ with (Et₂O)Li(N[R]Ar_MeL) (2 equiv) provides the uranium(III) -ate complex Li[I₂U(N[R]Ar_MeL)₂] (Li[1]), while treatment of UI₃ with three equiv. of K(N[R]Ar_MeL) provides the neutral uranium(III) complex U(N[R]Ar_MeL)₃ (2). Both uranium(III) complexes are susceptible to 1e oxidation, as is demonstrated by the syntheses of the uranium(IV) derivatives I₂U(N[R]Ar_MeL)₂ (1) and [U(N[R]Ar_MeL)₃][OTf] ([2][OTf]; OTf = CF₃SO₃). The spectroscopic and X-ray structural characterization of all four uranium complexes is described. The structures of 2 and [2][OTf] exhibit a large degree of steric pressure about the uranium center, effectively preventing the [2]⁺ ion from achieving a seven-coordinate structure.     

Cationic iridium complexes of the Xantphos ligand. Flexible coordination modes and the isolation of the hydride insertion product with an alkene

Reaction of the Ir(I)-Xantphos complex [Ir(κ²-Xantphos)(COD)][BAr^F₄] (Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, Ar^F = C₆H₃(CF₃)₂) with H₂ in acetone or CH₂Cl₂/MeCN affords the Ir(III)-hydrido complexes [Ir(κ³-Xantphos)(H)₂(L)][BAr^F₄], L = acetone or MeCN, whereas in non-coordinating CH₂Cl₂ solvent dimeric [Ir(κ³-Xantphos)(H)(μ-H)]₂[BAr^F₄]₂ is formed. A common intermediate in these reactions that invokes a (σ, η²-C₈H₁₃) ligand is reported. Addition of excess tert-butylethene (tbe) to [Ir(κ³-Xantphos)(H)₂(MeCN)][BAr^F₄] results in insertion of a hydride into the alkene to form [Ir(κ³-Xantphos)(MeCN)(CH₂CH₂C(CH₃)₃)(H)][BAr^F₄], an Ir(III) alkyl-hydrido-Xantphos complex. This reaction is reversible, and heating (80 °C) results in the reformation of [Ir(κ³-Xantphos)(H)₂(MeCN)][BAr^F₄] and tbe. These complexes have been characterised by NMR spectroscopy, ESI-MS and single-crystal X-ray diffraction. They show variable coordination modes of the Xantphos ligand: cis-κ²-P,P, fac-κ³-P,O,P and mer-κ³-P,O,P with the later coordination mode like that found in related PNP-pincer complexes.     

Synthesis and structure of new compounds with Pt-Ga bonds: Insertion of the bulky gallium (I) bisimidinate Ga(DDP) into Pt-Cl bond

Reactions of the sterically bulky mono-valent group 13 bisimidinate gallium(I), Ga(DDP) (1) (DDP = 2-{(2, 6-diisopropylphenyl)amino}-4-{(2, 6-diisopropylphenyl)imino}-2-pentene, HC(CMeNC₆H₃-2,6-ⁱPr₂)₂) with olefin supported group 10 complexes, [(diene)PtCl₂] [diene = 1,5-cyclooctadiene (COD), endo-dicyclopentadiene (dcy)] and [(COD)Pd(Me)(OTf)] (OTf = O₃SCF₃) are reported. These reactions afforded [(COD)Pt(Cl){ClGa(DDP)}] (2), [(dcy)Pt(Cl){ClGa(DDP)}] (3) and [(DDP)Ga(Me)(OTf)] (4) in moderate yields. Compounds 2-4 were characterized by elemental analysis, NMR (¹H, ¹³C) spectroscopy and also by single crystal X-ray structural analysis. The solid state structures of complexes 2 and 3 reveal the oxidative insertion of Ga(DDP) into the Pt-Cl bond without altering the π-coordinated double bonds in the olefin.