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(NCH2PtBu2)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.

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

Since moisture may frequently be present in many solvents, it is important to know the reactivity of a catalyst against water for catalytic reactions. In order to explore the stability and understand the transformation process of diphosphino-boryl-based PBP pincer platform, [PdCl{B(NCH2 Pt Bu2 )2 -o-C6 H4 }] (1) was treated with PdCl2 , HB(NCH2 PPh2 )2 -o-C6 H4 was reacted with [PdCl2 (cod)] (cod=cyclo-octa-1,5-diene) and [Pd2 (dba)3 ] (dba=dibenzylideneacetone), respectively, in the presence of water. Some novel palladium POP complexes, [Pd2 Cl2 (µ-Cl){µ-κ3 -P,O,P-OB(NCH2 Pt Bu2 )2 -o-C6 H4 }] (2 a), [Pd4 (µ-Cl)2 (µ-O)2 {µ-κ3 -P,O,P-OB(NCH2 PPh2 )2 -o-C6 H4 }2 ] (2 b), [Pd2 {µ-κ4 -P,P,P,P-O(B(NCH2 PPh2 )2 -o-C6 H4 )2 }{µ-κ2 -P,P-(NHCH2 PPh2 )2 -o-C6 H4 }] (3), were obtained. It was found that the PBP pincer backbone can easily be converted into a POP backbone in the presence of water. From the crystal structures of the resultant palladium complexes, possible pincer backbone transformation pathways were discussed.