Platinum-catalyzed double silylations of alkynes with bis(dichlorosilyl)methanes

Bis(dichlorosilyl)methanes 1 undergo the two kind reactions of a double hydrosilylation and a dehydrogenative double silylation with alkynes 2 such as acetylene and activated phenyl-substituted acetylenes in the presence of Speier’s catalyst to give 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 and 1,1,3,3-tetrachloro-1,3-disilacyclopent-4-enes 4 as cyclic products, respectively, depending upon the molecular structures of both bis(dichlorosilyl)methanes (1) and alkynes (2). Simple bis(dichlorosilyl)methane (1a) reacted with alkynes [R¹-CC-R²: R¹ = H, R² = H (2a), Ph (2b); R¹ = R² = Ph (2c)] at 80 °C to afford 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 as the double hydrosilylation products in fair to good yields (33-84%). Among these reactions, the reaction with 2c gave a trans-4,5-diphenyl-1,1,3,3-tetrachloro-1,3-disilacyclopentane 3ac in the highest yield (84%). When a variety of bis(dichlorosilyl)(silyl)methanes [(Me_nCl_3 − nSi)CH(SiHCl₂)₂: n = 0 (1b), 1 (1c), 2 (1d), 3 (1e)] were applied in the reaction with alkyne (2c) under the same reaction conditions. The double hydrosilylation products, 2-silyl-1,1,3,3-tetrachloro-1,3-disilacyclopentanes (3), were obtained in fair to excellent yields (38-98%). The yields of compound 3 deceased as follows: n = 1 > 2 > 3 > 0. The reaction of alkynes (2a-c) with 1c under the same conditions gave one of two type products of 1,1,3,3-tetrachloro-1,3-disilacyclopentanes 3 and 1,1,3,3-tetrachloro-1,3-disilacyclopent-4-enes (4): simple alkyne 2a and terminal 2b gave the latter products 4ca and 4cb in 91% and 57% yields, respectively, while internal alkyne 2c afforded the former cyclic products 3cc with trans form between two phenyl groups at the 3- and 4-carbon atoms in 98% yield, respectively. Among platinum compounds such as Speier’s catalyst, PtCl₂(PEt₃)₂, Pt(PPh₃)₂(C₂H₄), Pt(PPh₃)₄, Pt[ViMeSiO]₄, and Pt/C, Speier’s catalyst was the best catalyst for such silylation reactions.     

1-Methyl-4-ferrocenylmethyl-3,5-diphenylpyrazole: A versatile ligand for palladium(II) and platinum(II)

The syntheses and characterization of two novel ferrocene derivatives containing 3,5-diphenylpyrazole units of general formula [1-R-3,5-Ph₂-(C₃N₂)-CH₂-Fc] {Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄) and R = H (2) or Me (3)} together with a study of their reactivity with palladium(II) and platinum(II) salts or complexes under different experimental conditions is described. These studies have allowed us to isolate and characterize trans-[Pd{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}₂Cl₂] (4a) and three different types of heterodimetallic complexes: cis-[M{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}Cl₂(dmso)] {M = Pd (5a) or Pt (5b)}, the cyclometallated products [M{κ²-C,N-[3-(C₆H₄)-1-Me-5-Ph-(C₃N₂)]-CH₂-Fc}Cl(L)] with L = PPh₃ and M = Pd (6a) or Pt (6b) or L = dmso and M = Pt (8b) and the trans-isomer of [Pt{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}Cl₂(dmso)] (7b). In compounds 4a, 5a, 5b and 7b, the ligand behaves as a neutral N-donor group; while in 6a, 6b and 8b it acts as a bidentate [C(sp²,phenyl),N(pyrazole)]⁻ group. A comparative study of the spectroscopic properties of the compounds, based on NMR, IR and UV-Visible experiments, is also reported.     

Synthesis,structure and reactivity of novel palladiumdichloride-2,2′-bipyridine with 4,4′-bis(fluorous-ponytail)

With the readily available fluorous alkanols R_fCH₂OH, a series of novel fluorous-ponytailed bpy ligands, 4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy (1a–e), were prepared and treated with [PdCl₂(CH₃CN)₂] to result in the corresponding novel Pd complexes [PdCl₂(4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy)] (2a–e) where R_f = n-C₃F₇ (a), HCF₂(CF₂)₃ (b), HCF₂(CF₂)₇ (c), n-C₈F₁₇ (d), n-C₁₀F₂₁ (e). The new ligands and Pd complexes were spectroscopically characterized by multi-nuclei NMR (¹H, ¹⁹F and ¹³C), FTIR and high resolution mass (FAB). The structure for the Pd complex 2b, the first with fluorinated ponytails on bpy and not on phosphine, was also established by a single crystal X-ray diffraction study. The TGA data of both ligands and Pd complexes indicated that the Pd-complexes were resistant to higher temperatures than the corresponding ligands. The Pd catalysts derived from 2a–c showed an almost quantitative conversion and could be reused for eight runs with Heck reactions, in that the products and unspent reactants were directly removed by distillation. With the highest fluorine content in the series, Pd complex 2e was successfully applied in the Heck reaction using the fluorous biphasic catalysis strategy.     

Preparation of chelate bis(imine)nickel allyl systems by reaction of their corresponding butadiene complexes with electrophiles

The chelate 1,2-bis(imine)nickel(butadiene) complex 4a (chelate ligand derived from condensation of biacetyl with 2,6-diisopropylaniline) adds the strong Lewis acid B(C₆F₅)₃ at the terminal carbon atom of the butadiene ligand to yield the dipolar substituted π-allyl-type betaine complex (lig)Ni[η³-C₃H₄-CH₂B(C₆F₅)₃] (Z-6a). At 90 °C the kinetically formed product equilibrated with its E-6a isomer. Similarly, 4a adds the boron Lewis acid (pyrrolyl)B(C₆F₅)₂ to yield the corresponding neutral dipolar π-allyl betaine complex Z-7a, that slowly equilibrated with E-7a over several hours at ambient temperature. Protonation of the butadiene ligand of complex 4a was achieved by treatment with the neutral Brønsted acid (2H-pyrrol)B(C₆F₅)₃ to yield the [(lig)Ni(η³-crotyl)⁺][(pyrrolyl)B(C₆F₅)₃⁻] salt 9a (Z-/E-9a ratio=90:10 upon preparation). At 298 K this salt rearranged to a 5:95 mixture of Z-9a/E-9a with a Gibbs activation energy of ΔG^‡ (298 K)=22.3±0.2 kcal mol⁻¹. Complex 4a added [Ph₃C⁺] to the butadiene ligand to yield the salt [(lig)Ni(η³-C₃H₄-CH₂CPh₃)⁺][B(C₆F₅)₄⁻] (Z-12a), that proved isomerically stable under the applied reaction conditions. Similar reactions were carried out starting from the acenaphthylene 1,2-dione derived chelate bis(imine)Ni(butadiene) complex 4b. The systems 6, 7, 9 and 12 were found to be active ethene polymerization catalysts in the presence of Al(i-Bu)₃.     

Novel hydridotris(pyrazolyl)borate ruthenium(II) complexes containing the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane: Synthesis and evaluation of DNA binding properties

A series of half-sandwich ruthenium(II) complexes containing κ³(N,N,N)-hydridotris(pyrazolyl)borate (κ³(N,N,N)-Tp) and the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA) [RuX{κ³(N,N,N)-Tp}(PPh₃)_2−n(PTA)_n] (n = 2, X = Cl (1), n = 1, X = Cl (2), I (3), NCS (4), H (5)) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)L][PF₆] (L = NCMe (6), PTA (7)) have been synthesized. Complexes containing 1-methyl-3,5-diaza-1-azonia-7-phosphaadamantane(m-PTA) triflate [RuCl{κ³(N,N,N)-Tp}(m-PTA)₂][CF₃SO₃]₂ (8) and [RuX{κ³(N,N,N)-Tp}(PPh₃)(m-PTA)][CF₃SO₃] (X = Cl (9), H (10)) have been obtained by treatment, respectively, of complexes 1, 2 and 5 with methyl triflate. Single crystal X-ray diffraction analysis for complexes 1, 2 and 4 have been carried out. DNA binding properties by using a mobility shift assay and antimicrobial activity of selected complexes have been evaluated.     

New synthesis and thermal studies of palladacycloalkanes and their precursors

A series of new palladacycloalkanes of formula cis-[PdL₂(CH₂)_n] (9. n = 6, L = PPh₃; 10. n = 6, L₂ = dppe; 11. n = 8, L = PPh₃; 12. n = 8, L₂ = dppe) have been prepared by two routes. In the first route, the precursor bis(1-alkenyl) complexes cis-[PdL₂((CH₂)_nCHCH₂)₂] (1. n = 2, L = PPh₃, 2. n = 2, L₂ = dppe, 3. n = 3, L = PPh₃, 4. n = 3, L₂ = dppe) were allowed to react with Grubb’s 2nd generation catalyst to give the palladacycloalkenes, cis-[PdL₂(CH₂)_nCHCH(CH₂)_n] (5. n = 2, L = PPh₃, 6. n = 2, L₂ = dppe, 7. n = 3, L = PPh₃, 8. n = 3, L₂ = dppe), which were then hydrogenated to the palladacycloalkanes, 9-12. In the second route, the di-Grignard reagents BrMg(CH₂)_nMgBr (n = 6, 8) were reacted with the palladium complex [PdCl₂(COD)] followed by immediate ligand displacement to form the respective palladacycloalkanes 10 and 12. The complexes obtained were characterized by a range of spectroscopic and analytical techniques. Thermal decomposition studies were carried out on the palladacycloalkanes 9-12 and the main organic products shown to be 1-alkenes and 2-alkenes.     

Syntheses, structural and spectroscopic characterization of novel zinc(II)-bis(trithiocarbimato) complexes and bis(N-methylsulfonyldithiocarbimate)-sulfide

Four zinc(II)-bis(trithiocarbimato) complexes with the general formula A₂[Zn(RSO₂NCS₃)₂] [A = Ph₄P⁺: R = CH₃ (1), 4-CH₃C₆H₄ (2); A = Bu₄N⁺: R = CH₃ (3), 4-CH₃C₆H₄ (4)] were obtained by the reaction of sulfur with the correspondent zinc(II)-bis(dithiocarbimato) complexes. Additionally, the compound (Ph₄P)₂[(CH₃SO₂NCS₂)₂S)] (5) was prepared from the potassium methylsulfonildithiocarbimate by oxidation with iodine. The compounds were characterized by elemental analyses and IR, ¹H NMR and ¹³C NMR spectroscopies. The compounds 4 and 5 were also characterized by X-ray diffraction techniques. The compound 4 crystallizes in the centrosymmetric space group C2/c of the monoclinic system. The Zn(II) is in a distorted tetrahedral environment (ZnS₄) in compound 4, and differ from the coordination mode observed in compound 1, which involves one sulfur and one nitrogen atom of each trithiocarbimate ligand. Compound 5 is the first example of a compound containing a bis(N-alkylsulfonyldithiocarbimate)-sulfide dianion and crystallises in the non-centrosymmetric space group P4₁2₁2 of the tetragonal system.     

Syntheses, structures and magnetic properties of five iron(II) coordination polymers with flexible bis(imidazole) and bis(triazole) ligands

Five iron(II) coordination polymers, {[Fe(bte)₂(NCS)₂][Fe(bte)(H₂O)₂(NCS)₂]}_n (1), [Fe(bime)(NCS)₂]_n (2), [Fe(bime)(dca)₂]_n (3), [Fe(bime)₂(N₃)₂]_n (4) and [Fe(btb)₂(NCS)₂]_n (5), were synthesized using the flexible ligands 1,2-bis(1,2,4-triazol-1-yl)ethane (bte), 1,2-bis(imidazol-1-yl)ethane (bime) and 1,4-bis(1,2,4-triazol-1-yl)butane (btb), together with NCS⁻, dicyanamide (dca) and N₃⁻. The compound 1 contains two kinds of motifs (double chain and single chain) and forms a three-dimensional hydrogen bonded network; 2 and 3 contain one-dimensional triple chains; and 4 and 5 form two-dimensional (4, 4) networks. The coordination anions (NCS⁻, dca and N₃⁻) and the structural characteristics of the ligands (bte, bime and btb) play an important role in the assembly of the topologies. Magnetic studies reveal that 1-5 remain in the high-spin state over the whole temperature range 2-300 K and no detectable spin-crossover is observed.     

The (phosphino)tetraphenylborate ligand in ruthenium-arene chemistry

The synthesis of a series of anionic half-sandwich ruthenium-arene complexes [E][RuCl₂(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (E = Bu₄N⁺: R = Ph, 1a, ⁱPr, 1b or Cy, 1c; E = bis(triphenylphosphine)iminium or PNP⁺: R = Ph, 1a′, ⁱPr, 1b′ or Cy, 1c′) are reported. X-ray crystallographic studies of 1a′ and 1b′ confirmed the three-legged piano-stool coordination geometry. In solution, complexes 1a-c and 1a′-c′ are proposed to form monomer-dimer equilibria as a result of chloride ligand dissociation. Complexes 1a-c and 1a′-c′ also form the formally neutral zwitterionic complexes [RuCl(L)(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (L = pyridine: R = Ph, 2a, ⁱPr, 2b or Cy, 2c; L = MeCN: R = Ph, 3a, ⁱPr, 3b or Cy, 3c) via chloride ligand abstraction using AgNO₃ or MeOTf.     

Palladium(II)-allyl complexes containing chiral N-donor ferrocenyl ligands

A study of the reactivity of enantiopure ferrocenylimine (S_C)-[FcCHN-CH(Me)(Ph)] {Fc =  (η⁵-C₅H₅)Fe{(η⁵-C₅H₄)-} (1a) with palladium(II)-allyl complexes [Pd(η³-1R¹,3R²-C₃H₃)(μ-Cl)]₂ {R¹ = H and R² = H (2), Ph (3) or R¹ = R² = Ph (4)} is reported. Treatment of 1a with 2 or 3 {in a molar ratio Pd(II):1a = 1} in CH₂Cl₂ at 298 K produced [Pd(η³-3R²-C₃H₄){FcCHN-CH(Me)(Ph)}Cl] {R² = H (5a) or Ph (6a)}. When the reaction was carried out under identical experimental conditions using complex 4 as starting material no evidence for the formation of [Pd(η³-1,3-Ph₂-C₃H₃){FcCHN-CH(Me)(Ph)}Cl] (7a) was found. Additional studies on the reactivity of (S_C)-[FcCHN-CH(R³)(CH₂OH)] {R³ = Me (1b) or CHMe₂ (1c)} with complex 4 showed the importance of the bulk of the substituents on the palladium(II) allyl-complex (2-4) or on the ferrocenylimines (1) in this type of reaction. The crystal structure of 5a showed that: (a) the ferrocenylimine adopts an anti-(E) conformation and behaves as an N-donor ligand, (b) the chloride is in acis-arrangement to the nitrogen and (c) the allyl group binds to the palladium(II) in a η³-fashion. Solution NMR studies of 5a and 6a and [Pd(η³-1,3-Ph₂-C₃H₃){FcCHN-CH(Me)(CH₂OH)}Cl] (7b) revealed the coexistence of several isomers in solution. The stoichiometric reaction between 6a and sodium diethyl 2-methylmalonate reveals that the formation of the achiral linear trans-(E) isomer of Ph-CHCH-CH₂Nu (8) was preferred over the branched derivative (9). A comparative study of the potential utility of ligand 1a, complex 5a and the amine (S_C)-H₂N-CH(Me)(Ph) (11) as catalysts in the allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with the nucleophile diethyl 2-methylmalonate (Nu⁻) is reported.     

Novel (η-arene)-ruthenium(II) complexes containing bis(iminophosphorano)methanide and methandiide ligands

The novel bis(iminophosphorano)methanes CH₂[P{NP(S)(OR)₂}Ph₂]₂ (R = Ph (1a), Et (1b)) have been obtained by oxydation of dppm with the corresponding thiophosphorylated azides (RO)₂P(S)N₃. Deprotonation of 1a,b with KH generates the methanide species KCH[P{NP(S)(OR)₂}Ph₂]₂ (R = Ph (2a), Et (2b)). The ruthenium(II) dimer [{Ru(η⁶-p-cymene)(μ-Cl)Cl}₂] reacts with 2a,b to afford the cationic complexes [Ru(η⁶-p-cymene)(κ³-C,N,S-CH[P{NP(S)(OR)₂}Ph₂]₂)]⁺ (R = Ph (3a), Et (3b)), via selective κ³-C,N,S-coordination of the bis(iminophosphorano)methanide anions to ruthenium. The structure of [Ru(η⁶-p-cymene)(κ³-C,N,S-CH[P{NP(S)(OEt)₂}Ph₂]₂)][PF₆] (3b) has been confirmed by single-crystal X-ray crystallography. Deprotonation of complexes 3a,b with NaH leads to the neutral carbene derivatives [Ru(η⁶-p-cymene)(κ²-C,N-C[P{NP(S)(OR)₂}Ph₂]₂)] (R = Ph (4a), Et (4b)).     

Si-C coupling reaction of polychloromethanes with HSiCl3 in the presence of Bu4PCl: Convenient synthetic method for bis(chlorosilyl)methanes

Coupling reaction of polychloromethanes CH_4−nCl_n (n = 2-4) with HSiCl₃ in the presence of tetrabutylphosphonium chloride (Bu₄PCl) as a catalyst occurred at temperatures ranging from 30 °C to 150 °C. The reactivity of polychloromethanes increases as the number of chlorine-substituents on the carbon increases. In the reactions of CCl₄ with HSiCl₃, a variety of coupling products such as bis(chlorosilyl)methanes CH₂(SiCl₃)(SiXCl₂) [X = Cl (1a), H (1b)], (chlorosilyl)trichloromthanes Cl₃CSiXCl₂ [X = Cl (2a), H (2b)], and (chlorosilyl)dichloromthanes Cl₂HCSiXCl₂ [X = Cl (3a), H (3b)] were obtained along with reductive dechlorination products such as CHCl₃ and CH₂Cl₂ depending on the reaction temperature. In the reaction of CCl₄, 2a is formed at the initial stage of the coupling reaction and converted to give CHCl₃ at low temperature of 30 °C, to give 1a, 3a, and CHCl₃ at 60 °C, and to afford 1a as major product and CH₂Cl₂ in competition above 100 °C. Si-H bond containing silylmethanes can be formed by the H-Cl exchange reaction with HSiCl₃. Reaction of CHCl₃ with HSiCl₃ took placed at 80 °C to give three compounds 1a, 3a, and CH₂Cl₂, and finally 3a was converted to give 1a and CH₂Cl₂ at longer reaction time. While the condition for the reaction of CH₂Cl₂ with HSiCl₃ required a much higher temperature of 150 °C. Under the optimized conditions for synthesizing bis(chlorosilyl)methanes 1a,b, a mixture of 1a and 1b were obtained as major products in 65% (1a:1b = 64:1) and 47% (42:5) yields from the reaction of CCl₄ and CHCl₃ at 100 °C for 8 h, respectively, and in 41% (34:7) yield from that of CH₂Cl₂ at 170 °C for 12 h. In the Si-C coupling reaction of polychloromethanes with HSiCl₃, it seems likely that a trichlorosilyl anion generated from the reaction of HSiCl₃ with Bu₄PCl is an important key intermediate.     

Synthesis, characterization, and ethylene polymerization behavior of [(RR′-admpzp)2Ti(OPr)2] complexes (RR′-admpzp = 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-olate)

[(RR′-admpzp)₂Ti(OPrⁱ)₂] complexes (2a-c), synthesized from reaction of Ti(OPrⁱ)₃Cl (0.5 equiv) with 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-ol compounds in the presence of triethylamine (0.5 equiv), are pseudo-octahedral with each RR′-admpzp ligand κ²-O,N(pyrazolyl) coordinated to the titanium center. In solution, 2a-c adopt isomeric structures that are in dynamic equilibrium. At 23 °C, 2a-c/1000 MAO catalyst systems furnished high molecular weight polymers with narrow molecular weight distributions (M_w/M_n = 2.7-2.8). At 100 °C, 2a-c/MAO catalyst systems exhibited increased polymerization activity and 2c/1000 MAO system furnished high molecular weight polyethylene with a molecular weight distribution (M_w/M_n = 2.1) that is close to that found for single-site catalysts.     

Ruthenium complexes of aminophosphine ligands and their use as pre-catalysts in the transfer hydrogenation of aromatic ketones: X-ray crystal structure of thiophene-2-(N-diphenylthiophosphino)methylamine

Reaction of thiophene-2-methylamine with one or two equivalents of PPh₂Cl in the presence of NEt₃, proceeds in thf to give thiophene-2-(N-diphenylphosphino)methylamine, 1a and thiophene-2-(N,N-bis(diphenylphosphino))methylamine, 2a respectively, under anaerobic conditions. Oxidations of 1a and 2a with aqueous hydrogen peroxide, elemental sulfur or gray selenium in thf gives the corresponding oxides, sulfides and selenides [Ph₂P(E)NHCH₂-C₄H₃S] (E: O 1b, S 1c, Se 1d) and [(Ph₂P(E))₂NCH₂-C₄H₃S], (E: O 2b, S 2c, Se 2d) respectively, in high yield. Furthermore, two novel Ru(II) complexes with the P-N ligands 1a and 2a were synthesized starting with the complex [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂. The complexes were fully characterized by analytical and spectroscopic methods. ³¹P-{¹H} NMR, DEPT, ¹H-¹³C HETCOR or ¹H-¹H COSY correlation experiments were used to confirm the spectral assignments. The molecular structure of thiophene-2-(N-diphenylthiophosphino)methylamine was also elucidated by single-crystal X-ray crystallography. Following activation by NaOH, compounds 3 and 4 catalyze the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of iso-PrOH as the hydrogen source. [Ru(Ph₂PNHCH₂-C₄H₃S)(η⁶-p-cymene)Cl₂], 3 and [Ru((PPh₂)₂NCH₂-C₄H₃S)(η⁶-p-cymene)Cl]Cl, 4 complexes are suitable catalyst precursors for the transfer hydrogenation of acetophenone derivatives in 0.1 M iso-PrOH solution. Notably 4 acts as an excellent catalyst giving the corresponding alcohols in excellent conversions up to 99% (TOF ? 744 h⁻¹). This transfer hydrogenation is characterized by low reversibility under the experimental conditions.     

Synthesis and properties of novel fluorinated polynaphthalimides derived from 1,4,5,8-naphthalenetetracarboxylic dianhydride and trifluoromethyl-substituted aromatic bis(ether amine)s

A series of novel fluorinated polynaphthalimides (PNIs) (2a-g) were synthesized from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and trifluoromethyl (CF₃)-substituted aromatic bis(ether amine)s (1a-g) by high-temperature solution polycondensation in m-cresol using isoquinoline as catalyst. Almost all the PNIs were readily soluble in polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) and could be solution-cast to transparent and tough films with high tensile strengths. The PNIs exhibited high thermal stability, with glass-transition temperatures of 262-383 °C, 10% weight loss temperatures above 528 °C in nitrogen or air, and char yields at 800 °C in nitrogen higher than 50%. In comparison with analogous PNIs without the -CF₃ substituents, these fluorinated PNIs revealed an enhanced solubility and better film-forming capability.     

Alkyne activation by half-sandwich ruthenium(II) complexes bearing the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA)

Complex [RuCl{κ³(N,N,N)-Tp}(PPh₃)(PTA)] (κ³(N,N,N)-Tp = hydridotris(pyrazolyl)borate) containing the water-soluble phosphane 1,3,5-triaza-7-phosphatricyclo[3.3.1.1^3,7]decane (PTA) reacts with terminal alkynes producing to the corresponding neutral alkynyl complexes [Ru(CCR){κ³(N,N,N)-Tp}(PPh₃)(PTA)] (R = Ph (1a), ⁿBu (1b), 1-cyclopentenyl (1c), p-methoxyphenyl (1d), 6-methoxynaft-2-yl (1e)). When halide is extracted from complex [RuCl{κ³(N,N,N)-Tp}(PPh₃)(PTA)] followed by treatment with propargyl alcohols, the corresponding allenylidene complexes [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)(CCCPh₂)][X] (X = PF₆ (2a), CF₃SO₃ (2b)) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)(CCCC₁₂H₈)][PF₆] (3) result. Electrophilic attack on the complexes thus obtained leads chemoselectively to the alkynyl complexes [Ru(CCR){κ³(N,N,N)-Tp}(PPh₃)(1-CH₃-PTA)][CF₃SO₃] (R = Ph (4a), ⁿBu (4b), and 1-cyclopentenyl (4c)) and to the dicationic allenylidene complexes [Ru{κ³(N,N,N)-Tp}(PPh₃)(1-H-PTA)(CCCC₁₂H₈)][PF₆]₂ (5) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(1-CH₃-PTA)(CCCPh₂)][CF₃SO₃]₂ (6).     

Schiff bases containing ferrocenyl and thienyl units and their utility in the palladium catalyzed allylic alkylation of cinnamyl acetate

The synthesis and characterization of two new ferrocenyl Schiff bases: [Fc-CHN-(CH₂)_n-(C₄H₃S)] (2) {Fc represents (η⁵-C₅H₅)Fe(η⁵-C₅H₄)- and n = 1(2a) or 2(2b)} containing the thienyl (C₄H₃S) group are reported. NMR studies indicate that 2 have the anti-(E) conformation in solution and the X-ray crystal structure of 2a confirms that it also adopts the anti-(E) form in the solid state. Ligands 2 have been tested in the palladium catalyzed allylic alkylation of (E)-3-phenyl-2-propen-1-yl (cinnamyl) acetate using sodium diethyl 2-methylmalonate as nucleophile. The reaction of 2 with [Pd(η³-1-Ph-C₃H₄)(μ-Cl)]₂ in the presence of a slight excess K[PF₆] produced [Pd(η³-1-Ph-C₃H₄){Fc-CHN-(CH₂)_n-(C₄H₃S)}][PF₆] {n = 1(5a) or 2(5b)}, which are the intermediates of this catalytic process. NMR studies of 5 reveal the coexistence of several isomers in solution. The stoichiometric reactions of 5 with the nucleophile are also reported. The comparison of the results obtained for 2, [Fc-CHN-(C₆H₄-2SMe)] (1a) and [(2,4,6-Me₃-C₆H₂)-CHN-(C₆H₄-2SMe)] (1b) has allowed to establish the importance of the nature of the substituents on the imine group on the regioselectivity of the process.     

Greener fluorous chemistry: Convenient preparation of new types of ‘CF3-rich’ secondary alkyl mesylates and their use for the synthesis of azides, amines, imidazoles and imidazolium salts

2,2,2-Trifluoroethanol, 1,1,1,3,3,3-hexafluoro-2-propanol, and nonafluoro-tert-butyl alcohol were used as precursors for the preparation of the appropriate bis(polyfluoroalkoxymethyl)carbinols [(R_FHOCH₂)₂CHOH, 1a-c, R_FH = (a) CF₃CH₂, (b) (CF₃)₂CH, and (c) (CF₃)₃C] and the corresponding mesylates [(R_FHOCH₂)₂CHOSO₂CH₃, 2a-c]. This novel design paradigm is introduced to eliminate the persistence and bioaccumulation problems of fluorous chemistry, which are associated with the use of longer linear perfluoroalkyl groups (e.g. R_fn ≥ n-C₈F₁₇, n-C₇F₁₅). Secondary mesylates 2a,b and the primary tosylate [(CF₃)₃COCH₂CH₂OTs, 2d] displayed acceptable reactivity towards azide and imidazole nucleophiles to allow the syntheses of novel fluorous azides, which on hydrogenolysis with H₂/Pd-C offered fluorous amines [(R_FHOCH₂)₂CHNH₂, 8a,b], and 1-(polyfluoroalkyl)imidazoles (5a,b,d), respectively, while 2c showed no reactivity due to steric hindrance. The reaction of 8a,b with formaline, glyoxal and hydrochloric acid gave symmetrical 1,3-dialkylated imidazolium chlorides (9a,b), while 5a,b,d were effectively alkylated using n-C₈F₁₇(CH₂)₃I, methyl iodide, 2-bromoethanol, and 2d to yield the corresponding 1,3-dialkylimidazolium iodides, bromides, and tosylates (7aa-ec). Some physical properties of new compounds including mp, bp and solubility patterns were also analyzed; and the fluorophilicity values of 1a-c, and 2a-c were experimentally determined by GC and/or ¹⁹F NMR spectroscopy.     

Structure of N,C,N-chelated organotin(IV) fluorides

The set of starting tri-, di- and monoorganotin(IV) halides containing N,C,N-chelating ligand (L^NCN = {1,3-[(CH₃)₂NCH₂]₂C₆H₃}⁻) has been prepared (1-5) and two compounds structurally characterized ([L^NCNPh₂Sn]⁺I₃⁻ (1c), L^NCNSnBr₃ (5)) in the solid state. These compounds were reacted with KF with 18-crown-6, NH₄F or L^CNnBu₂SnF to give derivatives containing fluorine atom(s). Triorganotin(IV) fluorides L^NCNMe₂SnF (2a) and L^NCNnBu₂SnF (3a) revealed monomeric structural arrangement with covalent Sn-F bond both in the coordinating and non-coordinating solvents, except the behaviour of 3a that was ionized in the methanol solution at low temperature. The products of fluorination of L^NCNSnPhCl₂ (4) and 5 were described by NMR in solution as the ionic hypervalent fluorostannates or the oligomeric species reacting with chloroform, methanol or moisture to zwitterionic monomeric stannate L^NCN(H)⁺SnF₄⁻ (5c), which was confirmed by XRD analysis in the solid state.     

Syntheses and characterization of mono and dinuclear complexes of platinum group metals bearing benzene-linked bis(pyrazolyl)methane ligands

Reaction of the benzene-linked bis(pyrazolyl)methane ligands, 1,4-bis{bis(pyrazolyl)-methyl}benzene (L1) and 1,4-bis{bis(3-methylpyrazolyl)methyl}benzene (L2), with pentamethylcyclopentadienyl rhodium and iridium complexes [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh and Ir) in the presence of NH₄PF₆ results under stoichiometric control in both, mono and dinuclear complexes, [(η⁵-C₅Me₅)RhCl(L)]⁺ {L = L1 (1); L2 (2)}, [(η⁵-C₅Me₅)IrCl(L)]⁺ {L = L1 (3); L2 (4)} and [{(η⁵-C₅Me₅)RhCl}₂(μ-L)]²⁺ {L = L1 (5); L2 (6)}, [{(η⁵-C₅Me₅)IrCl}₂(μ-L)]²⁺ {L = L1 (7); L2 (8)}. In contrast, reaction of arene ruthenium complexes [(η⁶­arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me and C₆Me₆) with the same ligands (L1 or L2) gives only the dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(μ-L)]²⁺ {L = L1 (9); L2 (10)}, [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(μ-L)]²⁺ {L = L1 (11); L2 (12)} and [{(η⁶-C₆Me₆)RuCl}₂(μ-L)]²⁺ {L = L1 (13); L2 (14)}. All complexes were isolated as their hexafluorophosphate salts. The single-crystal X-ray crystal structure analyses of [7](PF₆)₂, [9](PF₆)₂ and [11](PF₆)₂ reveal a typical piano-stool geometry around the metal centers with six-membered metallo-cycle in which the 1,4-bis{bis(pyrazolyl)-methyl}benzene acts as a bis-bidentate chelating ligand.