199061-82-0Relevant academic research and scientific papers
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.
Probing the bonding of phosphines and phosphites to platinum by NMR. Correlations of 1J(PtP) and Hammett substituent constants for phosphites and phosphines coordinated to platinum(II) and platinum(0)
Cobley, Christopher J.,Pringle, Paul G.
, p. 107 - 115 (2008/10/08)
The values of 1J(PtP) have been measured for the platinum(II) complexes cis-[PtCl2L2] and cis-[PtMeClL2] and the platinum(0) complexes [PtL(norbornene)2] and [PtL2(norbornene)] where L = P(C6H4Z-4)3 and [PtL2(norbornene)], [PtL3] and [PtL4] where L = P(OC6H4Z-4)3 and Z = NMe2, OMe, Me, H, Cl, CF3. When 1J(PtP) is plotted against the Hammett substituent constant two distinct trends emerge: for platinum(II) the more electron-withdrawing the substituent the smaller the 1J(PtP), while for platinum(0) the more electron-withdrawing the substituent the larger the 1J(PtP). These observations are rationalised in terms of the σ and π-bonding components of the platinum-phosphorus bonds.
