47899-53-6Relevant academic research and scientific papers
A Study of the Mechanism of Platinum(II)/Tin(II) Dichloride Mediated Hydrogenation of Alkynes and Alkenes Employing Parahydrogen-Induced Polarization
Deibele, Christina,Permin, Alexei B.,Petrosyan, Valery S.,Bargon, Joachim
, p. 1915 - 1923 (2008/10/08)
The mechanism of hydrogenation of alkynes catalyzed by the [(PR3)2PtHX]/SnX2 system (PR3 = PPh3, PMePh2; X = Cl, Br) has been studied by means of parahydrogen-induced polarization of 1H spectra (PHIP). Dihydride intermediates confirming the stepwise hydrogenation at room temperature were observed when the reaction was run in acetone. The obtained 1H-PHIP spectra, together with NMR data for related species, are consistent with the formulation of these intermediates as cis-[H2Pt(PR3)(SnX 3)(σ-alkenyl)(acetone)], where the σ-alkenyl ligand originates from an insertion reaction of the alkyne (1-phenyl-1-propyne, 1-phenyl-1-butyne, diphenylacetylene, 3,3-dimethylbutyne). At elevated temperatures, the hydrogenation in acetone proceeds as a cis-synchronous transfer of the two hydrogen atoms of parahydrogen to the substrate molecule. A mechanism for this synchronous hydrogenation is suggested.
Stoichiometric model reactions in olefin hydroformylation by platinum-tin systems
Gómez, Montserrat,Muller, Guillermo,Sainz, Daniel,Sales, Joaquim,Solans, Xavier
, p. 4036 - 4045 (2008/10/08)
The three independent steps involved in the hydroformylation process, insertion of the olefin, insertion of carbon monoxide, and hydrogenolysis, have been investigated with use of platinum-tin catalysts and 1-pentene as olefin at low pressure and temperature in CH2Cl2. In the temperature range 198-308 K, the three reactions can be studied consecutively. All the intermediates observed were prepared and characterized separately. The complex trans-[PtH(SnCl3) (PPh3)2] was used as the initial compound for this sequence. The hydrido complex crystallized in the monoclinic space group C2/c, with a = 31.345 (5) ?, b = 12.716 (3) ?, c = 18.135 (3) ?, β = 96.5 (2)°, Z = 8, and R (Rw) = 0.056 (0.060) for 3235 independent reflections having I > 2.56σ(I). The large Pt-Sn bond (2.601 (1) ?) distance correlates satisfactorily with the low 1J(Pt-Sn) value. The Pt-Sn bond is necessary for the insertion of 1-pentene in the hydrido-platinum complex and for the hydrogenolysis of the acyl compounds under these mild conditions. The insertion of 1-pentene was observed at 198 K, giving the cis-alkyl complex; CO insertion took place after isomerization to the trans-alkyl complex. The instability of Pt-Sn and Pt-C bonds in the trans-acyl complex favors easy decarbonylation or loss of SnCl2, so any other platinum complex without tin accepts SnCl2 from the acyl complex. The hydrogenolysis of trans-[Pt(SnCl3) (COC5H11) (PPh3)2] under 1.5 bar of H2-CO (1:1) did not yield n-hexanal quantitatively; only 12% of n-hexanal was formed. Thus, decarbonylation was the main process observed. From the reactions studied, it is possible to propose the following order of Pt-Sn bond stability: trans-[Pt(SnCl3)(COC5H11)(PPh3) 2] 3)(C5H11)(PPh3)2] 3)(PPh3)2] 3)(CO)(PPh3)2] 3)(PPh3)]2 3)(PPh3)]- 2(SnCl3)2]2-. The insertion reactions studied with cis-[PtCl2(olefin)(PR3)] as an olefin carrier and the hydrido-platinum complexes trans-[PtHCl(PPh3)2], trans-[PtH(SnCl3)(PPh3)2], and [PtH(SnCl3)-(CO)(PPh3)2] as hydrogen carriers exclude the participation of intermolecular steps by reaction of two different platinum complexes under the experimental conditions described.
Formation of cationic MPt heterobimetallic μ-phosphido μ-hydrido complexes
Powell,Fuchs,Gregg,Phillips,Stainer
, p. 387 - 393 (2008/10/08)
The cationic secondary phosphine complexes [CpM(CO)(L)(PR2H)]+X- (M = Ru, PR2H = PPh2H, PPhH2, L = CO; M = Fe, PR2H = PPh2H, L = CO, MeC≡CMe, C2H4; M = Mn PR2H = PCy2H, PPr2H, L = NO; X- = BF4-, PF6-) and [(η7-C7H7)(CO)2Mo(PCy2H]PF6, prepared by following literature procedures for the synthesis of their PPh3 analogues, react with Pt(C2H4)(PPh3)2 to give [Cp(L)M(μ-PR2)(μ-H)Pt(PPh3)2]X and [(η7-C7H7)(CO)Mo(μ-PCy2) (μ-H)Pt(PPh3)2]X as the final products. The reactions proceed by one or both, of two possible reaction pathways. One pathway involves the initial oxidative addition of a P-H bond to the Pt(0) complex to give [Cp(CO)LM(μ-PR2)PtH(PPh3)2]X followed by PPh3 loss from Pt and CO transfer from M to Pt (via a bridging CO). The rate of this CO-transfer step is sterically driven, in a manner similar to that observed for ortho-metalation reactions. The more acidic (P-H) secondary phosphine complexes react with Pt(0) complexes by a route that involves deprotonation of the coordinated secondary phosphine to give a phosphidometal complex, which then substitutes a ligand from Pt(0) followed by CO transfer to Pt. Several complexes of this type (PR3 = PCy3) were prepared and studied from the reaction of [CpM(CO)(L)(PR2H)]+ with Pt(C2H4)2(PCy3).
CO labilization and hydrogen-transfer pathways in cationic phosphido-bridged Re-Pt heterobimetallic systems and the molecular structures of [η5-Cp(ON)Re(μ-PR2)(μ-H)Pt(PPh3) 2]X (R = Cy, X- = PF6-; R = Ph, X- = BF4-) and [η5-Cp(ON)HRe(μ-PCy ...
Powell, John,Sawyer, Jeffery F.,Stainer, Matthew V. R.
, p. 4461 - 4470 (2008/10/08)
Full title: CO labilization and hydrogen-transfer pathways in cationic phosphido-bridged Re-Pt heterobimetallic systems and the molecular structures of [η5-Cp(ON)Re(μ-PR2)(μ-H)Pt(PPh3) 2]X (R = Cy, X- = PF6-; R = Ph, X- = BF4-) and [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3) 2]BF4, a rare example of bridging- and terminal-hydrido geometric isomers. Oxidative addition of the cationic secondary phosphine complexes [η5-Cp(OC)(ON)Re(PR2H)]+ (6) (R = Ph, Cy, Pr) to Pt(C2H4)(PPh3)2 gives [η5-Cp(OC)(ON)Re(μ-PR2)PtH(PPh3) 2]+ (7). In contrast, reaction of 6 with Pt(PPh3)4 leads to CO loss and the formation of the terminal rhenium hydride derivative [η5-Cp(ON)HRe(μ-PR2)Pt(PPh3) 2]+ (8) as the kinetic product. On standing, 8 slowly transforms into the thermodynamically preferred bridging-hydrido isomer [η5-Cp(ON)Re(μ-PR2)(μ-H)-Pt(PPh 3)2]+ (9). The cations 7 will undergo slow CO loss to form 8 in the presence of base (e.g. F-, proton sponge), and the isomerization of 8 to 9 is promoted by added chloride ion with -d[8]/dt = k[8][Cl-]2. Complex 7 (R = Cy) reacts with added Cl- to give [η5-Cp(OC)(ON)Re(μ-PCy2)PtHCl(PPh3)] (10b), which reacts with Cl- abstractors (Ag+ or NaBPh4) to give an equilibrium mixture of [η5-Cp(ON)Re(μ-PCy2)(μ-H)Pt(PPh 3)(CO)]+ (11b) and [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3)(CO)] +, (12b) (PPh3 trans to μ-PCy2), which slowly transform to give [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3)(CO)] + (13b) (PPh3 cis to μ-PCy2). Cations 12b and 13b react rapidly with PPh3 to give 8 while 11b reacts with PPh3 to give 9b. The mechanism of formation of 7 and 8 from 6 and the mechanism of the base-promoted 7 to 8 rearrangement and the Cl--catalyzed 8 to 9 isomerization process are discussed. The molecular structures of [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3) 2]BF4 ((8b)BF4) and [η5-Cp(ON)Re(μ-PCy2)(μ-H)Pt(PPh 3)2]PF6 ((9b)PF6) (a rare example of terminal- and bridging-hydrido isomers) and [η5-Cp(ON)Re(μ-PPh2)(μ-H)Pt-(PPh 3)2]BF4 ((9a)BF4) have been determined. Crystal data for (8b)BF4: C53H58BF4NOP3PtRe·CH 2Cl2 crystallizes in space group P21/n with a = 11.031 (2) A?, b = 22.391 (5) A?, c = 21.603 (7) A?, β = 94.04 (2)°, V = 5322 A?3, and Z = 4. The structure was refined to R = 0.0407 and Rw = 0.0419. Crystal data for (9a)BF4: C53H46BF4NOP3PtRe, space group P1 with a = 12.563 (2) A?, b = 12.896 (1) A?, c = 15.024 (2) A?, α = 94.14 (1)°, β = 96.93 (2)°, γ = 92.01 (1)°, V = 2407 A°3, and Z = 2. The structure was refined to R = 0.0310 and Rw = 0.0325. Crystal data for (9b)PF6: C53H58F6NOP4PtRe·2.5CH 2Cl2, space group P1, a = 12.532 (2) A?, b = 13.077 (2) A?, c = 19.101 (2) A?, α = 94.85 (1)°, β = 105.40 (1)°, γ = 91.23 (1)°, V = 3004 A?3, and Z = 2. The structure was refined to R = 0.0471 and Rw = 0.0508. Cations 9a and 9b contain a planar "Re(μ-PR2)(μ-H)Pt" unit, the bridging hydrogen atom being located in both structures from difference Fourier maps, refined by least squares. The cation 8b contains a planar "HRe(μ-PCy2)Pt" unit. The position of the terminal hydride is inferred to be bonded to Re (confirmed by 1H NMR) in a position approximately trans to the Pt-Re bond by using (i) the approach of Orpen for the calculation of minimization of van der Waals repulsion energies and (ii) EHMO calculations. In contrast to previous studies a good correlation between 1J195Pt-31P and Pt-P bond lengths is observed for the complexes 8b, 9a, and 9b.
