78752-23-5

Upstream product

• 16395-67-8 tris-(chloromethyl)amine 
• 829-85-6 diphenylphosphane 
• 5958-44-1 diphenylphosphinomethanol 
• 96776-80-6 diphenyl-bis(hydroxymethyl)phosphonium chloride 
• 183268-31-7 bis(3,5-difluorophenyl)phosphine 
• 50-00-0 formaldehyd 

Relevant academic research and scientific papers

Synthesis and crystallographic characterisation of a homologous series of bis-tridentate phosphine oxide NP3O3 Fe(II), Co(II), Ni(II) and Cu(II) complexes

Despite the large numbers of mono- and bidentate phosphine oxide complexes, examples of well characterised discrete multidentate phosphine oxide transition metal complexes are relatively rare. Herein, we report the coordination chemistry of the triphosphine oxide ligand N{CH2P(O)Ph2}3 (NP3O3, 1) with a series of first row transition metals. Ligand 1 was found to form a series of bis-tridentate homoleptic complexes with Fe(II), Co(II), Ni(II) and Cu(II) salts of the type M(BF4)2·6H2O. The anion exchange reaction of BF4— for BPh4— aided in the crystallisation of three of the four complexes. X-Ray crystallographic analysis of this series: [Fe(N{CH2P(O)Ph2}3)2](BPh4)2 (2), [Co(N{CH2P(O)Ph2}3)2](BPh4)2 (3), [Ni(N{CH2P(O)Ph2}3)2](BPh4)2 (4) and [Cu(N{CH2P(O)Ph2}3)2](BF4)2 (5) confirmed either almost idealised octahedral or distorted octahedral structures and tridentate coordination of 1. Complex 5, Cu(II) d9, displayed a classic Jahn-Teller distortion showing a prominent elongation of the axial M–O bonds. All complexes were found to be paramagnetic which precluded NMR spectroscopy analysis. Magnetic susceptibility measurements on solid samples of the complexes confirmed their number of unpaired electrons and high spin states.

Synthesis and characterisation of a range of Fe, Co, Ru and Rh triphos complexes and investigations into the catalytic hydrogenation of levulinic acid

The coordination chemistry of the N-triphos ligand (NP3Ph, 1b) has been investigated with a range of Fe, Co and Rh precursors and found to form either tridentate or bidentate complexes. Reaction of NP3Ph with [Rh(COD)(CH3CN)2]BF4 resulted in the formation of the tridentate complex [Rh(COD)(κ3-NP3Ph)]BF4 (3) in the solid state, however, in solution a bidentate complex predominates in more polar solvents. Reaction of NP3Ph with Fe carbonyl precursors revealed the formation of the bidentate complexes [Fe(CO)3(κ1,κ2-NP3Ph)Fe(CO)4] (4) and [Fe(CO)3(κ2-NP3Ph)] (5), while reaction with FeBr2 resulted in the paramagnetic bidentate complex [Fe(Br)2(κ2-NP3Ph)] (6). Reaction of NP3Ph with CoCl2 gave a dimeric Co species [(κ2-NP3Ph)CoCl(κ1,κ2-NP3Ph)CoCl3] (7), while Zn powder reduction of NP3Ph Co halides resulted in the formation of the tridentate complexes of the type: [Co(X)(κ3-NP3Ph)]. The related triphos Ru complex, [Ru(CO3)(CO)(κ3-CP3Ph)] (2), has also been isolated and characterised. Preliminary catalytic hydrogenation of levulinic acid (LA) was conducted with 2 and 3. The Ru complex was found to be catalytically active, giving high conversions of LA to form gamma-vvvalerolactone (GVL) and 1,4-pentanediol (1,4-PDO), while 3 was found to be catalytically inactive. In situ catalytic testing with 1b and Fe(BF4)2.6H2O resulted in low conversions of LA while a combination of 1b and Co(BF4)2.6H2O gave high conversions to GVL.

Selective Ruthenium-Catalyzed Transformation of Carbon Dioxide: An Alternative Approach toward Formaldehyde

Formaldehyde is an important precursor to numerous industrial processes and is produced in multimillion ton scale every year by catalytic oxidation of methanol in an energetically unfavorable and atom-inefficient industrial process. In this work, we present a highly selective one-step synthesis of a formaldehyde derivative starting from carbon dioxide and hydrogen gas utilizing a homogeneous ruthenium catalyst. Here, formaldehyde is obtained as dimethoxymethane, its dimethyl acetal, by selective reduction of carbon dioxide at moderate temperatures (90 °C) and partial pressures (90 bar H2/20 bar CO2) in the presence of methanol. Besides the desired product, only methyl formate is formed, which can be transformed to dimethoxymethane in a consecutive catalytic step. By comprehensive screening of the catalytic system, maximum turnover numbers of 786 for dimethoxymethane and 1290 for methyl formate were achieved with remarkable selectivities of over 90% for dimethoxymethane.

Base-Free Hydrogenation of Carbon Dioxide to Methyl Formate with a Molecular Ruthenium-Phosphine Catalyst

Herein, a molecular ruthenium-phosphine catalyst system for the effective base-free methyl formate production from carbon dioxide is described. In detail, the novel [Ru(N-triphosCy)(tmm)] complex, bearing sterically demanding cyclohexyl groups in the triphos-ligand structure, enabled in combination with the Lewis acid Al(OTf)3 the selective transformation of carbon dioxide to methyl formate with unprecedented activity. From a mechanistic perspective, in the initial step formic acid is formed, undergoing a consecutive Lewis acid promoted esterification with methanol to methyl formate. This selective transformation with carbon dioxide paves the way to versatile processes for important C1 building blocks.

Branched-Selective Hydroformylation of Nonactivated Olefins Using an N-Triphos/Rh Catalyst

We report a catalytic system comprised of nitrogen-centered di- or triphosphine ligands in conjunction with rhodium that is capable of delivering branched aldehydes from terminal olefin substrates which commonly give more linear aldehydes than branched. The incorporation of an apical nitrogen atom into the ligand backbone dramatically improves the reaction rate. Mechanistic and labeling studies suggest the unusual selectivity is due to the irreversible trapping of the Rh-alkyl species along the branched pathway, in comparison to the more reversible linear pathway. A precatalytic equilibrium mixture of rhodium species was observed by high-pressure in situ NMR spectroscopy, suggesting this equilibrium is the catalytic resting state.

Insight into the stereoelectronic parameters of N-triphos ligands via coordination to tungsten(0)

A series of new N-triphos tungsten complexes have been synthesised and structurally characterised. The coordination behaviour of a range of N-triphos (N(CH2PR2)3, NP3R) ligands, and a mixed-arm diphosphine-pyridyl (PPNCyh) ligand were explored. The steric and electronic parameters of five N-triphos ligands: NP3Ph, NP3iPr, NP3Cyp, NP3Cyh and NP3 PhF2, and the carbon-centred triphos ligand, CH3C(CH2PPh2)3 (MeCP3Ph), were established. Steric parameters were evaluated by analysing the cone angles calculated from X-ray crystal structures, whilst the electron-donating ability of the ligands was determined from 31P-77Se NMR coupling constants of selenium derivatives and the IR carbonyl stretching frequencies across a series of tungsten-carbonyl complexes. In general, electron-rich phosphines formed bidentate complexes while less electron-rich ligands coordinated in a tridentate mode, regardless of steric bulk. An indirect interaction between the apical nitrogen of the ligand and metal centre is implicated for tridentate complexes and is supported through DFT calculations and analysis of N-protonated complexes. Complexes 1, 3, 4, 6-8 and 10 were characterised by single-crystal X-ray crystallography.

Synthesis, characterization, and reactivity of ruthenium hydride complexes of N-centered triphosphine ligands

The reactivity of the novel tridentate phosphine ligand N(CH 2PCyp2)3 (N-triphosCyp, 2; Cyp = cyclopentyl) with various ruthenium complexes was investigated and compared that of to the less sterically bulky and less electron donating phenyl derivative N(CH2PPh2)3 (N-triphosPh, 1). One of these complexes was subsequently investigated for reactivity toward levulinic acid, a potentially important biorenewable feedstock. Reaction of ligands 1 and 2 with the precursors [Ru(COD)(methylallyl)2] (COD = 1,5-cycloocatadiene) and [RuH2(PPh3)4] gave the tridentate coordination complexes [Ru(tmm){N(CH2PR2) 3-δ3P}] (R = Ph (3), Cyp (4); tmm = trimethylenemethane) and [RuH2(PPh3){N(CH 2PR2)3-δ3P}] (R = Ph (5), Cyp (6)), respectively. Ligands 1 and 2 displayed different reactivities with [Ru3(CO)12]. Ligand 1 gave the tridentate dicarbonyl complex [Ru(CO)2{N(CH2PPh2)3- δ3P}] (7), while 2 gave the bidentate, tricarbonyl [Ru(CO) 3{N(CH2PCyp2)3-δ2P} ] (8). This was attributed to the greater electron-donating characteristics of 2, requiring further stabilization on coordination to the electron-rich Ru(0) center by more CO ligands. Complex 7 was activated via oxidation using AgOTf and O2, giving the Ru(II) complexes [Ru(CO)2(OTf){N(CH 2PPh2)3-δ3P}](OTf) (9) and [Ru(CO3)(CO){N(CH2PPh2)3- δ3P}] (11), respectively. Hydrogenation of these complexes under hydrogen pressures of 3-15 bar gave the monohydride and dihydride complexes [RuH(CO)2{N(CH2PPh2) 3-δ3P}] (10) and [RuH2(CO){N(CH 2PPh2)3-δ3P}] (12), respectively. Complex 12 was found to be unreactive toward levulinic acid (LA) unless activated by reaction with NH4PF6 in acetonitrile, forming [RuH(CO)(MeCN){N(CH2PPh2)3- δ3P}](PF6) (13), which reacted cleanly with LA to form [Ru(CO){N(CH2PPh2)3-δ3P} {CH3CO(CH2)2CO2H- δ2O}](PF6) (14). Complexes 3, 5, 7, 8, 11, and 12 were characterized by single-crystal X-ray crystallography.

Ruthenium-catalysed hydrogenation of esters using tripodal phosphine ligands

The synthesis of a new tripodal phosphine ligand, N(CH2PEt 2)3, N-TriPhosEt is reported, and the use of tripodal ligands of this type, N(CH2PR2)3 (R = Ph, Et), in conjunction with ruthenium for the catalysed hydrogenation of dimethyl oxalate (DMO) is reported and contrasted with catalysis using the MeC(CH2PPh2)3 (TriPhosPh) ligand. A different order of reaction with respect to the DMO substrate is found, and the rate is slower. A study of the kinetics and mechanism of the hydrogenation of DMO with Ru(acac)3/TriPhosPh is described, along with the effect of different additives to the system. The performance of Ru(acac) 3/TriPhosPh/Zn system with unactivated ester substrates is probed and found to proceed significantly slower. Finally, based upon experimental observations, a mechanism is proposed for ester hydrogenation using ruthenium catalysts with tripodal phosphine ligands.

The preparation of multimetallic complexes using sterically bulky N-centred tripodal dialkyl phosphino ligands

Sterically bulky monodentate and bidentate phosphines have been widely used as ligands for metal complexation and catalyst formation. Bulky tridentate phosphine ligands are however much rarer and have not been widely investigated even though they may be considered attractive ligands for coordination chemistry studies and catalysis. Here we report the synthesis of two new N-centred tripodal phosphine ligands bearing bulky cyclohexyl and tert-butyl groups. The coordination chemistry of the cyclohexyl triphosphine ligand N(CH2PCy2)3 (4) was investigated and found to react with Mo and W hexacarbonyls preferentially forming bidentate metal tetracarbonyl complexes [Mo(CO)4{N(CH2PCy2)3-κ2P}] (6) and [W(CO)4{N(CH2PCy2)3-κ2P}] (7) over the expected facial capping tridentate complexes. The steric bulk of the cyclohexyl groups on the phosphorus atoms is sufficient to prevent the third arm of the ligand from coordinating and adopting the required geometry for facial coordination. This 'steric control' at the metal centre results in the third arm remaining freely available for further metal coordination. The coordination chemistry of this free phosphine arm on complexes 6 and 7 was investigated further and used to prepare a series of gold, platinum and silver multimetallic complexes. The X-ray crystal structures of the resulting mixed bi and trimetallic complexes [W(CO)4{N(CH2PCy2)3-κ2P}AuCl] (8), [[Mo(CO)4{N(CH2PCy2)3-κ2P}]2(μ-PtCl2)] (9) and [[W(CO)4{N(CH2PCy2)3-κ2P}]2(μ-Ag)]ClO4 (11) are reported.

Preparation and characterisation of N(CH2PPh2)3, N(CH2PPh2)3Mo(CO)3 and [HN(CH2PPh2)3Mo(CO)3]BF4

The synthesis of N(CH2PPh2)3 (1) and its spectroscopic properties are reported. Reaction of N(CH2PPh2)3 with (CH3CN)3Mo(CO)3 leads to N(CH2PPh2)3Mo(CO)3 (2). The cationic complex [HN(CH2PPh2)3Mo(CO)3]+ (3) is obtained by protonating the N atom of 2 with aqueous HBF4. The spectroscopic and structural properties of 2 and the cation 3 are compared. The results indicate an interaction of the ligand N atom and the Mo atom through space over more than 350 pm. It is shown from IR data that 2 is fixed on silicagel by hydrogen bonding.