A new approach to light-gated Pt catalysts for the hydrosilylation

Platinum(II) Phenylpyridyl Schiff Base Complexes as Latent, Photoactivated, Alkene Hydrosilylation Catalysts

Photoactivated catalysts for the hydrosilylation of alkenes with silanes offer temporal control in manufacturing processes that require silicone curing. We report the development of a range of air-stable Pt(II) (salicylaldimine)(phenylpyridyl), [Pt(sal)(ppy)], complexes as photoinitiated hydrosilylation catalysts. Some of these catalysts show appreciable latency in thermal catalysis and can also be rapidly (10 s) activated by a LED UV-light source (365 nm), to give systems that selectively couple trimethylvinylsilane and hexamethylsiloxymethylsilane to give the linear hydrosilylation product. Although an undetectable (by NMR spectroscopy) amount of precatalyst is converted to the active form under UV-irradiation in the timescale required to initiate hydrosilylation, clean and reliable kinetics can be measured for these systems that allow for a detailed mechanism to be developed for Pt(sal)(ppy)-based photoactivated hydrosilylation. The suggested mechanism is shown to have close parallels with, but also subtle differences from, those previously proposed for thermally-activated Karstedt-type Pt(0) systems.

Evaluation of Heteroleptic Pt (II) β-Diketonate Complexes as Precatalysts for the Photoactivated Curing of Silicone Resins

A library of platinum (II) complexes of general formula (O,O′-β-diketonate)PtLX (L = dimethylsulfoxide, pyridine, triphenylphosphine; X = chloride, γ-acetylacetonate) has been prepared, using synthetic methodologies available in the literature. The library has been supplemented with a novel platinum (II) complex bearing a triazenido N-oxide ligand. The complexes have been characterized and tested as precatalysts for the photoactivated curing of silicone resins. Correlations have been established between the nature of the employed ligands, the ultraviolet-visible (UV-Vis) absorption spectrum of the complexes and their catalytic performance, which enable the tailored preparation of complexes with improved performance in view of possible technological applications.

Platinum thiolate complexes supported by PBP and POCOP pincer ligands as efficient catalysts for the hydrosilylation of carbonyl compounds

Diphosphino-boryl-based PBP pincer platinum thiolate complexes, [Pt(SR){B(NCH₂P^tBu₂)₂-1,2-C₆H₄}] (R = H, 1a; Ph, 1b), and benzene-based bisphosphinite POCOP pincer platinum thiolate complexes, [Pt(SR)(^tBu₂PO)₂-1,3-C₆H₃] (R = H, 2a; Ph, 2b), were prepared and fully characterized by multinuclear NMR, X-ray crystallography, HRMS and elemental analyses. The application of these complexes in the catalytic hydrosilylation of aldehydes and ketones was investigated. It was found that these platinum thiolate complexes are efficient catalysts for the hydrosilylation of aldehydes and ketones at 65-75 °C. Comparatively, the PBP complexes are more active than the corresponding POCOP complexes. Both phenylsilane and polymethylhydrosiloxane (PMHS) can be used as silyl reagents. The expected alcohols were obtained in good to excellent yields after the basic hydrolysis of the hydrosilylation products and many functional groups were not affected. With turnover frequencies (TOFs) of up to 67 000 h^-1, the present catalytic system represents the most effective platinum catalytic system for the hydrosilylation of carbonyl compounds. The reactions were likely catalysed by the in situ generated platinum hydride species.

Photoswitchable catalysis using organometallic complexes

Photoswitchable catalysis using organometallic complexes: a ligand design perspective.

Fifty Years of Hydrosilylation in Polymer Science: A Review of Current Trends of Low-Cost Transition-Metal and Metal-Free Catalysts, Non-Thermally Triggered Hydrosilylation Reactions, and Industrial Applications

Hydrosilylation reactions, the (commonly) anti-Markovnikov additions of silanes to unsaturated bonds present in compounds such as alkenes and alkynes, offer numerous unique and advantageous properties for the preparation of polymeric materials, such as high yields and stereoselectivity. These reactions require to be catalyzed, for which platinum compounds were used in the initial stages. Celebrating the 50th anniversary of hydrosilylations in polymer science and, concomitantly, five decades of continuously growing research, hydrosilylation reactions have advanced to a level that renders them predestined for transfer into commercial products on the large scale. Facing this potential transfer, this review addresses and discusses selected current trends of the scientific research in the area, namely low-cost transition metal catalysts (focusing on iron, cobalt, and nickel complexes), metal-free catalysts, non-thermally triggered hydrosilylation reactions (highlighting stimuli such as (UV-)light), and (potential) industrial applications (highlighting the catalysts used and products manufactured). This review focuses on the hydrosilylation reactions involving alkene reactants.