15702-94-0Relevant academic research and scientific papers
High quantum yield molecular bromine photoelimination from mononuclear platinum(IV) complexes
Raphael Karikachery, Alice,Lee, Han Baek,Masjedi, Mehdi,Ross, Andreas,Moody, Morgan A.,Cai, Xiaochen,Chui, Megan,Hoff, Carl D.,Sharp, Paul R.
, p. 4113 - 4119 (2013/05/09)
Pt(IV) complexes trans-Pt(PEt3)2(R)(Br)3 (R = Br, aryl and polycyclic aromatic fragments) photoeliminate molecular bromine with quantum yields as high as 82%. Photoelimination occurs both in the solid state and in solution. Calorimetry measurements and DFT calculations (PMe3 analogs) indicate endothermic and endergonic photoeliminations with free energies from 2 to 22 kcal/mol of Br2. Solution trapping experiments with high concentrations of 2,3-dimethyl-2-butene suggest a radical-like excited state precursor to bromine elimination.
From azobenzene coordination to aryl-halide bond activation by platinum
Zenkina, Olena,Altman, Marc,Leitus, Gregory,Shimon, Linda J.W.,Cohen, Revital,Van Der Boom, Milko E.
, p. 4528 - 4534 (2008/10/09)
This contribution describes the reactivity of Pt(PEt3) 4 with (4-bromo-phenyl)-pyridin-4-yl-diazene. η2- Coordination of Pt(PEt3)2 to the N=N moiety is kinetically preferable and followed by an aryl-halide bond activation process. This quantitative transformation proceeds under mild reaction conditions in solution and in the solid state. Mechanistic studies in solution indicate that the metal insertion into the aryl-halide bond is the rate-determining step. The reaction obeys first-order kinetics in the η2-coordination complex with ΔG?298K = 24.6 ± 1.6 kcal/mol, ΔH? = 26.5 ± 1.6 kcal/mol, and ΔS ? = 6.6 ± 5.0 eu. No effect on the reaction progress and NMR line shape has been observed in the presence of excess PEt3. However, competition experiments with the η-coordination complex and PhBr reveal that the product ratio can be altered by the presence of PEt3, indicating that the two aryl-halide bond activation processes proceed via different mechanistic pathways. Numerical analysis of a series of competition experiments fits a reaction scheme involving a unimolecular transformation from the η2-coordination complex to the product of aryl-halide oxidative addition. This ring-walking process is kinetically accessible as shown by density functional theory (DFT) calculations at the PCM:PBEO/SDB-cc-pVDZ/PBE0/SDD level of theory.
195Pt, 119Sn AND 31P NMR STUDIES OF ALKYL, ARYL AND ACYL TRICHLOROSTANNATE COMPLEXES OF PLATINUM(II). THE CRYSTAL STRUCTURE OF trans-
Albinati, Alberto,Gunten, Urs von,Pregosin, Paul S.,Ruegg, Hubert J.
, p. 239 - 256 (2007/10/02)
195Pt, 119Sn and 31P NMR characteristics of the complexes tans-).The values of 1J(195Pt, 119Sn) vary from 2376 to 11895 Hz with the COPh ligand having the smallest and the C6H5 ligand the largest value, making a total range for this coupling constant, when the dimer syn-trans-2 is includeed, of ca. 33000 Hz.In the meta- and para-substituted phenyl complexes 1J(195Pt, 119Sn) (a) is greater for electron withdrawing substituents, (b) varies more for the meta-substituted derivatives (5634 to 7906 Hz) than for the para analogues (6088 to 7644 Hz) and (c) has the lowest values when the group is the meta- or para-substituent.The direction of the change in 1J(195Pt, 119Sn) is opposite to that found for 1J(195Pt, 31P).For the aryl complexes linear correlations are observed between δ(119Sn),1J(195Pt, 119Sn), 1J(195Pt, 31P), 2J(119Sn, 31P) and the Hamett substituent consatnt ?n. δ(119Sn) and 1J(195Pt,119Sn) are related linearly to ν(Pt-H) in the complexes trans-; δ(119Sn) and δ(1H) (hydride) are also linearly related.Based on 1J(195Pt,119Sn), the acyl ligand is suggested to have a very large NMR trans influence.The differences in the NMR parameters for (1a-e) are rationalized in terms of differing ?- and ?-bonding abilities of the carbon ligands.The structure of 1c has been determined by crystallographic methods.The complex has a slightly distorted square planar geomety with trans-PEt3 ligands.Relevant bond lengths (Angstroem) and bond angles (deg) are: Pt-Sn, 2.634(1), Pt-P, 2.324(4) and 2,329(4), Pt-C, 2.05(1); P-Pt-P, 170.7(6), Sn-Pt-C, 173.0(3), Sn-Pt-P, 92.1(19, 91.7(1), P-Pt-C, 88.8(4) and 88.3(4).The Pt-Sn bond separation is the longest yet observed for square-planar platinum trichlorostannate complexes, and would be consistent with a large crystallographic trans influence of the benzoyl ligand.The Pt-Sn bond separation is shown to correlate with 1J(195Pt, 119Sn).
Normal- and high-pressure kinetics and mechanism of the cis-trans isomerization of PtXR(PEt3)2 complexes. Evidence for an initial solvolysis step
Kelm, Hartwig,Louw, Wynand J.,Palmer, Donald A.
, p. 843 - 847 (2008/10/08)
It has been previously postulated that the spontaneous cis-trans isomerization of PtXR(PEt3)2, where R = alkyl or aryl groups and X = halides, occurs through the three-coordinate intermediate PtR(PEt3)2+, which is in a steady state during the reaction. High-pressure kinetics have now revealed a ΔV≠ value of-12 cm3 mol-1 for the first step in this mechanism. Therefore this step must be considered to be associative. Kinetics at atmospheric pressure show that the intermediate species is not in a steady state, but rather a preequilibrium exists. These data are consistent with an initial solvolysis step and also establish that the rate of solvolysis of cis-PtXR(PEt3)2 is faster than the rate of the subsequent isomerization reaction. A ΔV≠ value of +7.7 cm3 mol-1 was found for the isomerization reaction. This can be interpreted either as a dissociation of the intermediate cis-PtR(MeOH)(PEt3)2 or as an intramolecular rearrangement of this species.
