Hydrosilylation of Aldehydes and Ketones Catalysed by Bis(phosphinite) Pincer Platinum Hydride Complexes

Abstract

Bis(phosphinite) pincer platinum hydride complexes, [2,6‐(R2PO)2C6H3]PtH (R=tBu, iPr), were synthesized, characterized and applied to the hydrosilylation of aldehydes and ketones. NMR study and single crystal X‐ray diffraction analysis indicated that the hydrides in these two platinum complexes are comparatively less hydridic: down‐field 1H NMR resonances (0.71 and 0.98 ppm) and weak Pt−H interactions were observed. Both the platinum complexes were found to be good catalysts for the hydrosilylation of aldehydes and ketones with phenylsilane. The corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the resultant hydrosilylation products and turnover frequencies (TOFs) up to 3200 h−1 were achieved at 60 °C in toluene, which are much higher than those of the hydrosilylation catalysed by the corresponding nickel pincer hydride complexes. A possible mechanism for the present hydrosilylation process was discussed.magnified image

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

“…This specific type of reaction can effectively reduce the carbonyl groups in an organic molecule without affecting other functional groups in the same molecule. 11 In the last two decades, in order to apply this type of reaction in a more cost-effective and environmentally benign manner, great efforts have been made to develop first-row transition metal catalysts, 12 explore more efficient catalytic systems based on precious metals 13 and find new protocols to utilize inexpensive silyl reagents such as polymethylhydrosiloxane (PMHS). 14 Ptbased catalysts have been extensively used in the hydrosilylation of olefins.…”

“…15 However, they have far less been applied to catalyse the hydrosilylation of carbonyl compounds. 13,16 The main efforts of the limited reports in this area were focused on the chemo/stereo-selectivity or methodology 16 with very little attention being paid to the catalytic activity. 13 Recently, we found that POCOP-type pincer platinum hydride complexes are effective catalysts for the hydrosilylation of aldehydes and ketones.…”

“…13,16 The main efforts of the limited reports in this area were focused on the chemo/stereo-selectivity or methodology 16 with very little attention being paid to the catalytic activity. 13 Recently, we found that POCOP-type pincer platinum hydride complexes are effective catalysts for the hydrosilylation of aldehydes and ketones. 13 In order to find more efficient platinum catalysts for this type of reaction, we synthesized several platinum thiolate complexes supported by PBP and POCOP pincer ligands and explored their catalytic activity.…”

The Stability of Diphosphino‐Boryl PBP Pincer Backbone: PBP to POP Ligand Hydrolysis

“…However, in the absence of oxygen, only hydrolysis would occur to produce multidentate phosphine ligands. Because of the different steric and electronic effects, substituents on the phosphorus atoms can sometimes significantly influence the properties of the resulting transition metal complexes especially for PXP type pincer complexes [9f,12] . The metal center in a Ph−PBP complex is easier to be accessed by other reagents due to the flat and less bulky Ph substituents.…”

Hydrosilylation and hydroboration in a sustainable manner: from Earth-abundant catalysts to catalyst-free solutions

“…Undoubtedly, hydrosilylation is to the most useful and applicable reaction in organosilicon chemistry, being simultaneously one of the most important homogeneous processes in industry. 28 In spite of a multitude of efforts to replace noble metals as catalysts, it should be made clear that platinumbased systems are still the most useful for both large 29 and small-scale [30][31][32][33][34][35][36][37] productions of organosilicon derivatives, which were quite nicely summarized by Marciniec and coworkers. 38 However, an extremely high price of these catalysts and often also harsh reaction conditions have caused an extensive exploration of less expensive and milder alternatives.…”