Rate and Mechanism of the Oxidative Addition of a Silylborane to Pt⁰ Complexes – Mechanism for the Pt‐Catalyzed Silaboration of 1,3‐Cyclohexadiene

Abstract

The chemical reduction of Pt(acac) 2 by DIBALH in the presence of phosphanes, which is used to generate active Pt 0 complexes in the Pt-catalyzed silaboration of cyclohexadiene by 2-(dimethylphenylsilyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1) leading to the 1,4-silaborated product, was mimicked by the electrochemical reduction of Pt(acac) 2 in the presence of 2 equiv. of PR 3 (R = Ph, nBu). The electrochemical reduction generates free acac anions and neutral Pt 0 -(PR 3 ) 2 complexes. The kinetics of the oxidative addition of bromobenzene (used first as a model molecule) and silylborane 1 to the Pt 0 complexes was investigated and the rate constants determined. Pt 0 (PnBu 3 ) 2 is much more reactive than Pt 0 (PPh 3 ) 2 towards 1. From the electrochemical study, it emerges that the acac anions released in the reduction of Pt(acac) 2 do not coordinate to the Pt 0 (PR 3 ) 2 complexes. Consequently, the rate of the oxidative addition of 1 to Pt 0 (PR 3 ) 2 , generated either by the electrochemical reduction or by the

Facile One-Pot Synthesis of Pd@Pt1L Octahedra with Enhanced Activity and Durability toward Oxygen Reduction

“…However, because the initial reduction rates of the two metal precursors only differed by about 10 times, it was difficult to obtain Pd@Pt core–shell nanocrystals with a monolayer or submonolayer coverage for the Pt shells. In separate studies, it was established that Pt­(acac) 2 could be reduced at a much slower rate relative to that of PtCl 4 2– owing to a relatively strong complexation of the acac ligand to Pt 2+ . , As such, it is interesting to examine if one can generate Pt monolayer coating by replacing PtCl 4 2– with Pt­(acac) 2 . In addition, it is more attractive to use Pt­(acac) 2 rather than PtCl 4 2– as the Cl – ions contained in the latter complex can facilitate oxidative etching, leading to a detrimental interdiffusion process between Pd and Pt atoms and thus the formation of alloys .…”

Wet chemical synthesis of intermetallic Pt3Zn nanocrystals via weak reduction reaction together with UPD process and their excellent electrocatalytic performances

“…can be 1.44 V more positive than that of Zn 2+ /Zn, and the calculated value is 0.58 V. 26 On the other hand, when platinum(II) acetylacetonate (Pt(acac) 2 ) was employed as a Pt precursor, the existence of acetylacetone ligands might help to keep a consistent supply of free Pt 2+ via the complexation and lower the reduction potential. 27 Once the Pt 2+ is reduced to Pt, the Zn 2+ would be reduced subsequently through a quick UPD process. Note that the UPD is a sub-monoatomic layer deposition, which is blocked automatically when the whole surface is properly covered with sub-monoatomic layer of foreign metal atoms (e.g.…”

“…It should be pointed that the Pt(acac) 2 is necessary in the present case because it can not only keep a consistent supply of free Pt 2+ for the slow reducing rate of Pt 2+ to metallic Pt via the complexation of Pt 2+ ions with acetylacetone ligands, but also lower the reduction potential. 27 By replacing Pt(acac) 2 with H 2 PtCl 6 or K 2 PtCl 4 , all products are Pt NCs (see corresponding XRD patterns and TEM images in Fig. S5 in the ESI †), which could be due to a relatively positive reduction potential and fast reducing rate of H 2 PtCl 6 or K 2 PtCl 4 to metallic Pt.…”

Copper-Catalyzed Stereo- and Enantioselective 1,4-Protosilylation of α,β-Unsaturated Ketimines To Synthesize Functionalized Allylsilanes

“…Tremendous efforts have been devoted to discovering new methodologies for the synthesis of allylic silanes because of their broad applications in organic synthesis and materials science . Among them, transition-metal reactions such as Ni, Pd, and Pt catalyzed silaborations of 1,3-dienes or allenes and Cu-catalyzed allylic substitution with use of Suginome silaboronate reagent have emerged as very powerful tools for the preparation of these compounds. Nevertheless, to access the multisubstituted functionalized allylsilanes, the development of practical and efficient methods still remains highly desirable.…”