59328-99-3Relevant academic research and scientific papers
Pt-Me bond cleavage in the reactions of dimethylplatinum(II) complexes containing chelating phosphine ligands with organotin(IV) chlorides
Momeni, Badri Z.,Eatezadi, Sedigheh
, p. 1288 - 1291 (2013)
Selective Pt-Me bond activation of dimethylplatinum(II) complexes [PtMe2(PP)] (PP = dppm (bis(diphenylphosphino)methane), dppe (1,2-bis(diphenylphosphino)ethane), dppp (1,3-bis(diphenylphosphino)propane)) was achieved by SnMe2Cl2 to yield the corresponding platinum(II) complexes [PtMeCl(PP)] (PP = dppm, dppe, dppp) and cis-[PtCl 2(PP)] (PP = dppm, dppp). On the other hand, the reactions of complexes [PtMe2(PP)] (PP = dppm, dppe, dppp) with SnPh3Cl resulted in the selective cleavage of the Pt-Me bond to afford the methylplatinum(II) complexes [PtMeCl(PP)]. Notably, the reaction of [PtMe 2(dppm)] with SnMe2Cl2 and SnPh3Cl also gave the ionic A-frame complex [Pt2Me2(μ-Cl)(μ- dppm)2]Cl. The variable-temperature 1H and 31P NMR spectroscopy shows that the cleavage of the Pt-Me bond occurs very rapidly and the short-lived platinum(IV) intermediate is difficult to detect during the reaction. An explanation is presented on the basis of the nature of the strong π-acceptance of the phosphine ligand, which resulted in the formation of a very unstable platinum(IV) intermediate.
Mechanistic insight into the protonolysis of the Pt-C bond as a model for C-H bond activation by platinum(II) complexes
Romeo, Raffaello,D'Amico, Giuseppina
, p. 3435 - 3446 (2008/10/09)
The kinetic and NMR features of the protonolysis reactions on platinum(II) alkyl complexes of the types cis-[PtMe2L2], [PtMe 2(L-L)], cis-[PtMeClL2], and [PtMeCl(L-L)] (L = PEt 3, P(Pri)3, PCy3, P(4-MePh) 3, L-L = dppm, dppe, dppp, dppb) in methanol suggest a rate-determining proton attack at the Pt - C bond. In contrast, a multistep oxidative-addition - reductive-elimination mechanism characterizes the methane loss on protonation of the corresponding trans-[PtMeClL2] species. Tools that were particularly diagnostic in suggesting different reaction pathways for the two systems were (i) the different results of kinetic deuterium isotope experiments, (ii) the detection or absence of Pt(IV) hydrido alkyl intermediate species by low-temperature 1H NMR experiments, and (iii) the detection or absence of isotope scrambling and incorporation of deuterium into Pt - CH3, combined with the loss of a range of CH nDn-4 isotopomers. For all systems, the rates of protonolysis are retarded by ligand steric congestion, accelerated by ligand electron donation, and almost unaffected by the chain length along the series of chelate complexes. A straight line correlates the rates of protonolysis of cis-dialkyl and cis-monoalkyl complexes, the difference in reactivity between the two systems being almost 5 orders of magnitude (slope of the line = 6 × 104). Factors controlling the dichotomy of behavior between complexes of different geometry have been taken into consideration. Application of the principle of microscopic reversibility suggests the reason why platinum complexes with nitrogen donor ligands appear to be far more efficient than platinum phosphane complexes in activating the C-H bond.
High-pressure NMR investigation of the intermediates of platinum-phosphine hydroformylation catalysts
Kegl, Tamas,Kollar, Laszlo,Radics, Lajos
, p. 249 - 254 (2008/10/08)
The reactions of square-planar alkylplatinum-diphosphine complexes, Pt(Me)(Cl)(bdpp) (1) and Pt(Me)(SnCl3)(bdpp) (2), as well as Pt{CH(COOEt)CH3}(Cl)(dppp) (3) (where bdpp=(2S,4S)-2,4-bis(diphenylphosphino)pentane, dppp=1,3-bis(diphenylphosphino)propane) with carbon monoxide and carbon monoxide/hydrogen mixture have been studied by high pressure NMR. Carrying out the pressurization at 273 K and the measurement of a sample containing 2 at 173 K, a methylplatinum-hydride was detected under 50 bar CO/H2=1/1 pressure in CD2Cl2 which was transferred to [Pt(CH3)(CO)(bdpp]+SnCl3- (2a) and [Pt(COCH3)(CO)(bdpp]+SnCl3- (2b) at room temperature. The platinum complex containing an alkyl stable to β-hydride elimination Pt{CH(COOEt)CH3} (Cl) (dppp) (3) was reacted with carbon monoxide resulting mainly in Pt(dppp)Cl2 and an ionic intermediate analogous to 2a, [Pt{CH(COOEt)CH3}(CO) (dppp)] +Cl- (3a). However, the same reaction with the in situ formed SnCl2-inserted product, Pt{CH(COOEt)CH3}(SnCl3) (dppp) yielded [Pt(CH3) (CO) (dppp)] +SnCl3- (4a) as a minor component besides PtCl2(dppp) and the decomposition product Pt(Me) (Cl) (dppp) (1′).
