Syntheses, X-ray structures and CVD studies of diorganoalkoxogallanes

Structural studies by X-ray crystallography have been carried out for a range of diorganoalkoxogallanes incorporating donor-functionalized ligands. The compounds [Et₂Ga(μ-OR)]₂ (1, R = CH₂CH₂NMe₂; 2, R = CH(CH₃)CH₂NMe₂; 3, C(CH₃)₂CH₂OMe; 4, R = CH(CH₂NMe₂)₂) adopt dimeric structures with a planar Ga₂O₂ ring, and each gallium atom is coordinated in a distorted trigonal bipyramidal geometry. Low pressure chemical vapor deposition (CVD) of 2 and 4 resulted in the formation of oxygen deficient gallium oxide thin films on glass. However, the reaction of Et₃Ga and ROH (R = CH₂CH₂NMe₂, CH(CH₃)CH₂NMe₂, C(CH₃)₂CH₂OMe, CH(CH₂NMe₂)₂) in toluene under aerosol assisted (AA)CVD conditions afforded stoichiometric Ga₂O₃ thin films on glass. This CVD technique offers a rapid, convenient route to Ga₂O₃, which involves the in situ formation of diethylalkoxogallanes, of the type [Et₂Ga(μ-OR)]₂, the structures of which are described in this paper. The gallium oxide films were deposited at 450 °C and analyzed by scanning electron microscopy (SEM), X-ray powder diffraction, wavelength dispersive analysis of X-rays (WDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.     

Syntheses and structures of non-symmetric guanidinato zirconium and hafnium complexes and their catalytic behavior for ethylene polymerization

Equivalent addition reactions of PhN(Li)SiMe₃ to nitriles, RCN (R = dimethylamido, 1-piperidino), generated non-symmetric guanidinato lithium [(Et₂O)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (1) or [(THF)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (2) and [(Et₂O)LiN(SiMe₃)C(N(CH₂)₅)N(Ph)]₂ (5) which further reacted with zirconium or hafnium tetrachloride to form Zr and Hf guanidinato complexes with the general formula [PhNC(R)NSiMe₃]₃MCl (R = dimethylamido, M = Zr (3), Hf (4); R = 1-piperidino, M = Zr (6), Hf (7)). Complexes 1-4, 6 and 7 were well characterized by ¹H, ¹³C NMR and microanalysis, the single crystal X-ray diffraction analysis data for complexes 1, 3, 4 and 7 were also provided. Furthermore, complexes 3, 4, 6 and 7 were found to be active for ethylene polymerization. The influences of cocatalyst, pressure, reaction temperature and Al/M ratio on activity were investigated.     

Synthesis, characterization, and reactivity of new types of constrained geometry group 4 metal complexes derived from picolyl-substituted dicarbollide ligand systems

The syntheses of group 4 metal complexes containing the picolyldicarbollyl ligand Dcab^PyH [nido-7-HNC₅H₄(CH₂)-8-R-7,8-C₂B₉H₁₀] (2) are reported. New types of constrained geometry group 4 metal complexes (Dcab^Py)MCl₂, [{(η⁵-RC₂B₉H₉)(CH₂)(η¹-NC₅H₄)}MCl₂] (M = Ti, 3; Zr, 4; R = H, a; Me, b), were prepared by the reaction of 2 with M(NMe₂)₂Cl₂ (M = Ti, Zr). The reaction of 2 with M(NMe₂)₄ in toluene afforded (Dcab^Py)M(NMe₂)₂, [{(η⁵-RC₂B₉H₉)(CH₂)(η¹-NC₅H₄)}M(NMe₂)₂] (M = Ti, 5; Zr, 6; R = H, a; Me, b), which readily reacted with Me₃SiCl to yield the corresponding chloride complexes (Dcab^Py)MCl₂ (M = Ti, 3; Zr, 4; R = H, a; Me, b). The structures of the diamido complexes (Dcab^Py)M(NMe₂)₂ (M = Ti, 5; Zr, 6) were established by X-ray diffraction studies of 5a, 5b, and 6a, which verified an η⁵:η¹-bonding mode derived from the dicarbollylamino ligand. Related constrained geometry catalyst CGC-type alkoxy titanium complexes, (Dcab^Py)Ti(OⁱPr)₂ (7), were synthesized by the reaction of 2 with Ti(OⁱPr)₄. Sterically less demanding phenols such as 2-Me-C₆H₄OH replaced the coordinated amido ligands on (Dcab^Py)Ti(NMe₂)₂ (5a) to yield aryloxy stabilized CGC complexes (Dcab^Py)Ti(OPh^Me)₂(Ph^Me  =  2- Me-C₆H₄, 8). NMR spectral data suggested that an intramolecular Ti-N coordination was intact in solution, resulting in a stable piano-stool structure with two aryloxy ligands residing in two of the leg positions. The aryloxy coordinations were further confirmed by single crystal X-ray diffraction studies on complexes (Dcab^Py)Ti(OPh^Me)₂ (8).     

Synthesis and structures of zinc alkoxo,aryloxo and hydroxo complexes with an amidodiamine ligand

The synthesis and characterization of zinc complexes bearing an amidodiamine ligand, (EtO)₄Zn₃[N(CH₂CH₂NMe₂)₂]₂ (1), [(Et₃CO)ZnN(CH₂CH₂NMe₂)₂]₂ (2) and [(2,6-ⁱPr₂C₆H₃O)ZnN(CH₂CH₂NMe₂)₂]₂ (3), [(Me₃Si)₂N]Zn[N(CH₂CH₂NMe₂)₂] (4) and [(Me₃Si)₂N]₂Zn₂(OH)[N(CH₂CH₂NMe₂)₂] (5), are reported. Compounds 1–3 are synthesised in the reactions of {Zn[N(CH₂CH₂NMe₂)₂]₂}₂ with 2 equiv. of ethanol, 3-ethyl-3-pentanol and 2,6-diisopropylphenol, respectively. Compound 4 is obtained by the reaction of Zn[N(SiMe₃)₂]₂ with HN(CH₂CH₂NMe₂)₂, and compound 5 is synthesised by reacting 4 with 1 equiv. of H₂O. Compound 4 is characterized by NMR and MS while all of the other compounds are characterized with NMR, MS, elemental analysis and single-crystal X-ray diffraction. Compound 1 is a trinuclear species containing a Zn₃N₂O₂ core. Compounds 2 and 3 are dimeric with planar Zn₂N₂ rings. Compound 5 is dimeric with a planar Zn₂NO ring.     

Group 4 metal complexes bearing new tridentate (NNO) ligands: Benzyl migration and formation of unusual C-C coupled products

Group 4 metal complexes bearing new phenoxy(benzimidazolyl)-imine, -amine and -amide ligands have been synthesized. A series of metal chloride derivatives has been prepared via treatment of MCl₄(THF)₂ (M = Ti, Zr, Hf) with the in situ generated sodium salt of the (benzimidazolyl)imine phenol 1. Reaction of the pro-ligand 2 with TiCl₄(THF)₂ afforded the corresponding complex 8 in which the amine proton remains bound to the nitrogen donor. Benzyl complexes of zirconium and hafnium were synthesized via treatment of pro-ligands 1 and 2 with M(CH₂Ph)₄ precursors. The complexes [NNO]M(CH₂Ph)₃ (6 M = Zr, 7 M = Hf) were found to undergo benzyl migration from the metal centre to the imine carbon of the ligand backbone giving complexes 11 and 12; the migration follows first order kinetics. The reaction of 1 with Ti(NMe₂)₄ led to the formation of an unusual C-C coupled product in which a new piperazine ring has formed. Complexes 11 and 12 undergo related transformations, leading to analogous C-C coupled products which were characterized by X-ray crystallography. Deuterium labelling experiments were carried out to determine the mechanistic pathway of the reactions. Chloride and benzyl complexes 3-12 were screened as pre-catalysts for olefin polymerization.     

Reactivity of silyl-substituted heterobimetallic iron-platinum hydride complexes towards unsaturated molecules: Part II. Insertion of trifluoropropyne and hexafluorobutyne into the platinum-hydride bond

Insertion of hexafluorobutyne into the Pt-H bond of the heterobimetallic complexes [(OC)₃Fe{Si(OMe)₃}(μ-Ph₂PXPPh₂)Pt(H)(PPh₃)] (1a X = CH₂; 1b X = NH) yields the σ-alkenyl complexes [(OC)₃Fe{μ-Si(OMe)₂(OMe)}(μ-Ph₂PXPPh₂)Pt{C(CF₃)C(H)CF₃}] (3a X = CH₂; 3b X = NH). This insertion reaction is accompanied by dissociation of the platinum bound PPh₃ ligand and saturation of the vacant coordination site by a dative μ−η²-Si-O → Pt interaction. Addition of the Pt-H bond of 1a across the triple bond of 3,3,3-trifluoropropyne affords in a regiospecific manner [(OC)₃Fe{μ-Si(OMe)₂(OMe)}(μ-dppm)Pt{C(CF₃)CH₂}] (2) having the trifluoromethyl substituent on the α-carbon. Addition of RNC to 3 affords the isocyanide adducts [(OC)₃Fe{Si(OMe)₃}(μ-Ph₂PXPPh₂)Pt(CNR){C(CF₃)C(H)CF₃}] (4a R = t-Bu, X = CH₂; 4b R = 2,6-xylyl, X = CH₂; 4c R = 2,6-xylyl, X = NH). In dichloromethane solution 3a is gradually transformed into the C₄F₆-bridged compound [(OC)₃Fe(μ-dppm)(μ-CF₃CCCF₃)Pt(CO)] 5. The Pt-bound carbonyl ligand of 5 is displaced by xylylisocyanide or trimethylphosphite affording the derivatives [(OC)₃Fe(μ-dppm)(μ-CF₃CCCF₃)Pt(CNxylyl)] 6 and [(OC)₃Fe(μ-dppm)(μ-CF₃CCCF₃)Pt{P(OMe)₃}] 7. The molecular structures of 4a, 5 and 6 have been determined by X-ray diffraction studies.     

Synthesis, structure, and catalytic activity of titanium complexes with new chiral 11,12-diamino-9,10-dihydro-9,10-ethanoanthracene-based ligands

A new series of organo-titanium complexes have been prepared from the reaction between Ti(NMe₂)₄ and C₂-symmetric ligands, (R,R)-11,12-bis(pyrrol-2-ylmethyleneamino)-9,10-dihydro-9,10-ethanoanthracene (1H₂), and (R,R)-bis(diphenylthiophosphoramino)-9,10-dihydro-9,10-ethanoanthracene (2H₂), (R,R)-11,12-bis(mesitylenesulphonylamino)-9,10-dihydro-9,10-ethanoanthracene (3H₂) and (R,R)-bis(diphenylthiophosphoramino)-1,2-cyclohexane (4H₂). Treatment of Ti(NMe₂)₄ with 1 equiv of 1H₂ gives, after recrystallization from a benzene solution, the binuclear double helicate titanium amide (1)₂[Ti(NMe₂)₂]₂⋅(5) in 71% yield. While under similar reaction conditions, reaction of Ti(NMe₂)₄ with 1 equiv of 2H₂, 3H₂ or 4H₂ gives, after recrystallization from a toluene or benzene solution, the mononuclear single helicate titanium amides (2)Ti(NMe₂)₂ (6), (3)Ti(NMe₂)₂ (7) and (4)Ti(NMe₂)₂ (8), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 5-8 have further been confirmed by X-ray diffraction analyses. The titanium amides are active catalysts for the polymerization of rac-lactide, leading to the isotactic-rich polylactides.     

F NMR spectroscopy as useful tool for determining the structure in solution of coordination compounds of MF5 (M = Nb, Ta)

The salts [S(NMe₂)₃][MF₆] (M = Nb, 2a; M = Ta, 2b) and [S(NMe₂)₃][M₂F₁₁] (M = Nb, 2c; M = Ta, 2d) have been prepared by reacting MF₅ (M = Nb, 1a; M = Ta, 1b) with [S(NMe₂)₃][SiMe₃F₂] (TASF reagent) in the appropriate molar ratio. The solid state structure of 2b has been ascertained by X-ray diffraction. The 1:1 molar ratio reactions of 1a with a variety of organic compounds (L) give the neutral adducts NbF₅L [L = Me₂CO, 3a; L = MeCHO, 3b; L = Ph₂CO, 3c; L = tetrahydrofuran (thf), 3d; L = MeOH, 3e; L = EtOH, 3f; L = HOCH₂CH₂OMe, 3g; L = Ph₃PO, 3h; L = NCMe, 3i] in good yields. The complexes MF₅L [M = Nb, L = HCONMe₂, 3j; M = Nb, L = (NMe₂)₂CO, 3k; M = Ta, L = (NMe₂)₂CO, 3l; M = Nb, L = OC(Me)CHCMe₂, 3m] have been detected in solution in admixture with other unidentified products, upon 2:1 molar reaction of 1 with the appropriate reagent L. The ionic complexes [NbF₄(tht)₂][NbF₆], 4a, and [NbF₄(tht)₂][Nb₂F₁₁], 4b, have been obtained by combination of tetrahydrothiophene (tht) and 1a, in 1:1 and 2:3 molar ratios, respectively. The treatment of 1 with a two-fold excess of L leads to the species [MF₄L₄][MF₆] [M = Nb, L = HCONMe₂, 5a; M = Ta, L = HCONMe₂, 5b; M = Nb, L = thf, 5c; M = Ta, L = thf, 5d; M = Nb, L = OEt₂, 5e]. The new complexes have been fully characterised by NMR spectroscopy. Moreover, the revised ¹⁹F NMR features of the known compounds MF₅L [M = Ta, L = Me₂CO, 3n; M = Ta, L = Ph₂CO, 3o; M = Ta, L = MePhCO, 3p; M = Ta, L = thf, 3q; M = Nb, L = CH₃CO₂H, 3r; M = Nb, L = CH₂ClCO₂H, 3s; M = Ta, L = CH₂ClCO₂H, 3t], TaF₄(acac), TaF₄(Me-acac) and [TaF(Me-acac)₃][TaF₆] (Me-acac = methylacetylacetonato anion) are reported.     

Synthesis and structural characterization of (COT)Pr(C13H8CH2CH2OMe)(THF) containing the chelating 9-(2-methoxyethyl)fluorenyl ligand

Treatment of 9-(2-methoxyethyl)fluorene, C₁₃H₉CH₂CH₂OMe (1), with potassium hydride in THF/toluene in the presence of 18-crown-6 afforded orange-red crystalline K(18-crown-6)C₁₃H₈CH₂CH₂OMe (2) in 59% yield. A “constrained geometry”-type praseodymium complex containing the 9-(2-methoxyethyl)fluorenyl ligand, (COT)Pr(C₁₃H₈CH₂CH₂OMe)(THF) (3), was prepared by treatment of dimeric [(COT)Pr(μ-Cl)(THF)₂]₂ (COT = η⁸-cyclooctatetraenyl) with in situ prepared KC₁₃H₈CH₂CH₂OMe. The molecular structures of 1, 2, and 3 were determined by single-crystal X-ray diffraction.     

Synthesis and crystal structures of boratranes with methyl substituents on the atrane cage

Three monomeric boratranes B[(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n] (n = 0, 1; n = 1, 2; n = 2, 3) have been synthesized by the reaction of B(OMe)₃ with a series of triethanolateamines such as [(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]³⁻ (n = 0, L1; n = 1, L2; n = 2, L3), where the number of CMe₂ groups adjacent to the OH functionality varied from 3 (L1H₃) to 2 (L2H₃) to 1 (L3H₃). These boratranes 1-3 have been characterized by solution ¹H, ¹³C{¹H} and ¹¹B NMR, and the crystal structures of 1 and 2 have been determined by single crystal X-ray diffraction.     

Synthesis and protonolysis of neutral aluminum dihydride compounds stabilized by tridentate-substituted pyrrolyl ligands: Synthesis, structural characterization and ring-opening polymerization of ?-caprolactone

A series of aluminum compounds containing tridentate pyrrolyl ligands were obtained from related aluminum dihydride compounds via protonolysis. Treatment of tetranuclear aluminum compound [C₄H₂N{2,5-(CH₂NMe₂)₂}Al₂H₅]₂ (1) with two equivalents of [C₄H₃N{2,5-(CH₂NMe₂)₂}] in methylene chloride at 0 °C led to the formation of [C₄H₂N{2,5-(CH₂NMe₂)₂}]AlH₂ (2). Similarly, when the deuterated aluminum compound 1D was used, the corresponding aluminum compound [C₄H₂N{2,5-(CH₂NMe₂)₂}]AlD₂ (2D) could be isolated. The reaction of 2 with one or two equivalents of phenylethyne, triphenylmethanethiol, 2,6-diisopropylaniline, or triphenylsilanol generated mononuclear aluminum compounds [[C₄H₂N{2,5-(CH₂NMe₂)₂}]AlRR′ (3, R = -CCPh, R′ = H; 4, R = R′ = -CCPh; 5, R = -SCPh₃, R′ = H; 6, R = R′ = -SCPh₃; 7, R = -NH(2,6-ⁱPr₂Ph), R′ = H; 8, R = R′ = -NH(2,6-ⁱPr₂Ph); 9, R = -OSiPh₃, R′ = H; 10, R = R′ = -OSiPh₃). Related Al-D compounds of 3, 5, 7 and 9 were also synthesized and corresponding IR spectroscopic data well matched in comparison of the stretching frequencies of Al-H and Al-D. The molecular structures of 2D, 4, 5, 5D, 7, and 10 have been determined by X-ray crystallography. Compounds 2, 5, and 7 initiated the ring-opening polymerization of ?-caprolactone and produced high-molecular weight of poly-?-caprolactone.     

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.     

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.     

Organometallic SERMs (selective estrogen receptor modulators): Cobaltifens, the (cyclobutadiene)cobalt analogues of hydroxytamoxifen

The McMurry coupling of (tetraphenylcyclobutadiene)cobalt(cyclopentadienyl) ketones, (C₄Ph₄)Co[C₅H₄C(O)R], where R = Me, 3a, or Et, 3b, with a range of substituted benzophenones furnished a series of cobaltifens, organometallic analogues of tamoxifen whereby a phenyl ring has been replaced by an organo-cobalt sandwich moiety. These systems of the general formula (η⁴-C₄Ph₄)Co[η⁵-C₅H₄C(R)C(Ar)Ar′], where R = Me or Et, and Ar = Ar′ = p-C₆H₄X where X is OH, 2a and 2b, OMe, 2c and 2d, OBn, 2e and 2f, or O(CH₂)₂NMe₂, 12a and 12b, and where Ar = C₆H₄OH and Ar′ = C₆H₄O(CH₂)₂NMe₂, 2g and 2h, have been characterised by NMR spectroscopy and/or X-ray crystallography. The effect of 2a and 2b, 2g and 2h, and 12a and 12b on the growth of MCF-7 (hormone-dependent) and MDA-MB-231 (hormone-independent breast cancer cells) was studied. The dihydroxycobaltifens 2a and 2b exhibit a strong estrogenic effect on MCF-7 cells while the aminoalkyl-hydroxycobaltifens, 2g and 2h, were found to be only slightly cytotoxic on MDA-MB-231 cells (IC₅₀ = 27.5 and 17 μM); surprisingly, however, the bis-(dimethylaminoethoxy)cobaltifens, 12a and 12b were shown to be highly cytotoxic towards both cell lines (IC₅₀ = 3.8 and 2.5 μM).     

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, structure, and catalytic activity of titanium(IV) and zirconium(IV) amides with chiral biphenyldiamine-based ligands

A new series of titanium(IV) and zirconium(IV) amides have been prepared from the reaction between M(NMe₂)₄ (M = Ti, Zr) and C₂-symmetric ligands, (R)-2,2′-bis(pyridin-2-ylmethylamino)-6,6′-dimethyl-1,1′-biphenyl (2H₂), (R)-2,2′-bis(pyrrol-2-ylmethyleneamino)-6,6′-dimethyl-1,1′-biphenyl (3H₂), (R)-2,2′-bis(diphenylphosphinoylamino)-6,6′-dimethyl-1,1′-biphenyl (4H₂), (R)-2,2′-bis(methanesulphonylamino)-6,6′-dimethyl-1,1′-biphenyl (5H₂), (R)-2,2′-bis(p-toluenesulphonylamino)-6,6′-dimethyl-1,1′-biphenyl (6H₂), and C₁-symmetric ligands, (R)-2-(diphenylthiophosphoramino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (7H) and (R)-2-(pyridin-2-ylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (8H), which are derived from (R)-2,2′-diamino-6,6′-dimethyl-1,1′-biphenyl. Treatment of M(NMe₂)₄ with 1 equiv. of N₄-ligand, 2H₂ or 3H₂ gives, after recrystallization from an n-hexane solution, the chiral zirconium amides (2)Zr(NMe₂)₂ (9), (3)Zr(NMe₂)₂ (11), and titanium amide (3)Ti(NMe₂)₂ (10), respectively, in good yields. Reaction of Zr(NMe₂)₄ with 1 equiv of diphenylphosphoramide 4H₂ affords the chiral zirconium amide (4)Zr(NMe₂)₂ (12) in 85% yield. Under similar reaction conditions, treatment of Ti(NMe₂)₄ with 1 equiv. of sulphonylamide ligand, 5H₂ or 6H₂ gives, after recrystallization from a toluene solution, the chiral titanium amides (5)Ti(NMe₂)₂·0.5C₇H₈ (13·0.5C₇H₈) and (6)Ti(NMe₂)₂ (15), respectively, in good yields, while reaction of Zr(NMe₂)₄ with 1 equiv. of 5H₂ or 6H₂ gives the bis-ligated complexes, (5)₂Zr (14) and (6)₂Zr (16). Treatment of M(NMe₂)₄ with 2 equiv. of diphenylthiophosphoramide ligand 7H or N₃-ligand 8H gives, after recrystallization from a benzene solution, the bis-ligated chiral zirconium amides (7)₂Zr(NMe₂)₂ (17) and (8)₂Zr(NMe₂)₂ (19), and bis-ligated chiral titanium amide (8)₂Ti(NMe₂)₂ (18), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 10, 12, 13, and 17-19 have further been confirmed by X-ray diffraction analyses. The zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in good to excellent yields with moderate ee values, while the titanium amides are not.     

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.     

Synthesis and structural characterization of organotin(IV) carboxylates based on different heterocyclic substituents

Six novel organotin(IV) carboxylates have been successfully synthesized, namely, the polymer (C₆H₅)₃Sn(L1)_∞ (1) [HL1 = 4-imidazolyl benzoic acid], the mononuclear (C₆H₅)₃Sn(L2) (2) [HL2 = 4-pyrazolylbenzoic acid], (C₆H₅)₃Sn(L3)·CH₃OH (3) [HL3 = 4-triazolylbenzoic acid] and (C₆H₅)₃Sn(L4) (4) [HL4 = 4-tetrazolyl benzoic acid] and the tetranuclear [(n-Bu₂Sn)₄(L2)₂O₂(OCH₃)₂] (5) and [(n-Bu₂Sn)₄(L3)₂O₂(OCH₃)₂] (6). X-ray diffraction analyses show 1D infinite chain of polymer 1, single molecular structures of isomorphous complexes 2 and 4, single molecule structures of complex 3 containing solvent CH₃OH molecule and similar ladder-type structures of complexes 5 and 6. The photoluminescence of ligands and 1-6 were also measured in the solid state at room temperature.     

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.     

Mono and dinuclear half-sandwich platinum group metal complexes bearing pyrazolyl-pyrimidine ligands: Syntheses and structural studies

Reactions of 0.5 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = η⁶-C₆H₆, η⁶-p-ⁱPrC₆H₄Me) and [(Cp∗)M(μ-Cl)Cl]₂ (M = Rh, Ir; Cp∗ = η⁵-C₅Me₅) with 4,6-disubstituted pyrazolyl-pyrimidine ligands (L) viz. 4,6-bis(pyrazolyl)pyrimidine (L1), 4,6-bis(3-methyl-pyrazolyl)pyrimidine (L2), 4,6-bis(3,5-dimethyl-pyrazolyl)pyrimidine (L3) lead to the formation of the cationic mononuclear complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ (L = L1, 1; L2, 2; L3, 3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ (L = L1, 4; L2, 5; L3, 6), [(Cp∗)Rh(L)Cl]⁺ (L = L1, 7; L2, 8; L3, 9) and [(Cp∗)Ir(L)Cl]⁺ (L = L1, 10; L2, 11; L3, 12), while reactions with 1.0 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ and [(Cp∗)M(μ-Cl)Cl]₂ give rise to the dicationic dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(L)]²⁺ (L = L1, 13; L2, 14; L3, 15), [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(L)]²⁺ (L = L1, 16; L2, 17; L3, 18), [{(Cp∗)RhCl}₂(L)]²⁺ (L = L1, 19; L2, 20; L3, 21) and [{(Cp∗)IrCl}₂(L)]²⁺ (L = L1 22; L2, 23; L3 24). The molecular structures of [3]PF₆, [6]PF₆, [7]PF₆ and [18](PF₆)₂ have been established by single crystal X-ray structure analysis.