Triangular Triplatinum Complex with Four Bridging Si Ligands: Dynamic Behavior of the Molecule and Catalysis

A triangular triplatinum(0) complex with bridging diphenylsilylene ligands, [{(Pt­(PMe₃)}₃(μ-SiPh₂)₃] (<b>1a</b>), reacts with H₂SiPh₂ to produce the 1:1 adduct, [{Pt­(PMe₃)}₃(H)₂(μ-SiPh₂)₄] (<b>2a</b>), which was isolated and characterized by X-ray crystallography. Two Pt–Pt bonds of the triangular Pt₃ core are bridged by a diphenylsilylene ligand, while the remaining Pt–Pt bond has two unsymmetrical bridging Si ligands. Dissolution of <b>1a</b> and H₂SiPh₂ at a 1:3 molar ratio forms a mixture of complex <b>2a</b> and unreacted <b>1a</b>. NMR measurement of the solution at −90 °C revealed the structure of <b>2a</b> as having two hydride ligands and four bridging silylene ligands. Two ³¹P­{¹H} NMR signals of <b>2a</b> at −90 °C coalesce on warming to −50 °C owing to facile exchange of the four Si ligands. Reversible addition of H₂SiPh₂ to <b>1a</b> yielded <b>2a</b> with Δ<i>G</i>° = −8.0 kJ mol^–1, Δ<i>H</i>° = −51.7 kJ mol^–1, and Δ<i>S</i>° = −146 J mol^–1 K^–1. Addition of bis­(4-fluorophenyl)­silane and bis­(4-methylphenyl)­silane to the complexes, which have three bis­(4-fluorophenyl)­silylene and bis­(4-methylphenyl)­silylene ligands, respectively, also occurs reversibly in the solution, and the diarylsilane with an electron-withdrawing substituent is favored for the formation of Pt₃Si₄ complexes. Complex <b>1a</b> catalyzes hydrosilyation of benzaldehyde with H₂SiPh₂ to produce diphenyl­(benzyloxy)­silane along with concurrent hydrosilyation and dehydrosilyation of phenyl­(methyl)­ketone. Dehydrogenative coupling of H₂SiPh₂ and phenol is also catalyzed to yield diphenyl­(phenoxy)­silane. The ³¹P­{¹H} NMR spectra of the mixtures during the catalytic reaction show <b>2a</b> as the major Pt-containing species

Triangular Triplatinum Complex with Four Bridging Si Ligands: Dynamic Behavior of the Molecule and Catalysis

A triangular triplatinum(0) complex with bridging diphenylsilylene ligands, [{(Pt­(PMe₃)}₃(μ-SiPh₂)₃] (<b>1a</b>), reacts with H₂SiPh₂ to produce the 1:1 adduct, [{Pt­(PMe₃)}₃(H)₂(μ-SiPh₂)₄] (<b>2a</b>), which was isolated and characterized by X-ray crystallography. Two Pt–Pt bonds of the triangular Pt₃ core are bridged by a diphenylsilylene ligand, while the remaining Pt–Pt bond has two unsymmetrical bridging Si ligands. Dissolution of <b>1a</b> and H₂SiPh₂ at a 1:3 molar ratio forms a mixture of complex <b>2a</b> and unreacted <b>1a</b>. NMR measurement of the solution at −90 °C revealed the structure of <b>2a</b> as having two hydride ligands and four bridging silylene ligands. Two ³¹P­{¹H} NMR signals of <b>2a</b> at −90 °C coalesce on warming to −50 °C owing to facile exchange of the four Si ligands. Reversible addition of H₂SiPh₂ to <b>1a</b> yielded <b>2a</b> with Δ<i>G</i>° = −8.0 kJ mol^–1, Δ<i>H</i>° = −51.7 kJ mol^–1, and Δ<i>S</i>° = −146 J mol^–1 K^–1. Addition of bis­(4-fluorophenyl)­silane and bis­(4-methylphenyl)­silane to the complexes, which have three bis­(4-fluorophenyl)­silylene and bis­(4-methylphenyl)­silylene ligands, respectively, also occurs reversibly in the solution, and the diarylsilane with an electron-withdrawing substituent is favored for the formation of Pt₃Si₄ complexes. Complex <b>1a</b> catalyzes hydrosilyation of benzaldehyde with H₂SiPh₂ to produce diphenyl­(benzyloxy)­silane along with concurrent hydrosilyation and dehydrosilyation of phenyl­(methyl)­ketone. Dehydrogenative coupling of H₂SiPh₂ and phenol is also catalyzed to yield diphenyl­(phenoxy)­silane. The ³¹P­{¹H} NMR spectra of the mixtures during the catalytic reaction show <b>2a</b> as the major Pt-containing species

Triangular Triplatinum Complex with Four Bridging Si Ligands: Dynamic Behavior of the Molecule and Catalysis

A triangular triplatinum(0) complex with bridging diphenylsilylene ligands, [{(Pt­(PMe₃)}₃(μ-SiPh₂)₃] (<b>1a</b>), reacts with H₂SiPh₂ to produce the 1:1 adduct, [{Pt­(PMe₃)}₃(H)₂(μ-SiPh₂)₄] (<b>2a</b>), which was isolated and characterized by X-ray crystallography. Two Pt–Pt bonds of the triangular Pt₃ core are bridged by a diphenylsilylene ligand, while the remaining Pt–Pt bond has two unsymmetrical bridging Si ligands. Dissolution of <b>1a</b> and H₂SiPh₂ at a 1:3 molar ratio forms a mixture of complex <b>2a</b> and unreacted <b>1a</b>. NMR measurement of the solution at −90 °C revealed the structure of <b>2a</b> as having two hydride ligands and four bridging silylene ligands. Two ³¹P­{¹H} NMR signals of <b>2a</b> at −90 °C coalesce on warming to −50 °C owing to facile exchange of the four Si ligands. Reversible addition of H₂SiPh₂ to <b>1a</b> yielded <b>2a</b> with Δ<i>G</i>° = −8.0 kJ mol^–1, Δ<i>H</i>° = −51.7 kJ mol^–1, and Δ<i>S</i>° = −146 J mol^–1 K^–1. Addition of bis­(4-fluorophenyl)­silane and bis­(4-methylphenyl)­silane to the complexes, which have three bis­(4-fluorophenyl)­silylene and bis­(4-methylphenyl)­silylene ligands, respectively, also occurs reversibly in the solution, and the diarylsilane with an electron-withdrawing substituent is favored for the formation of Pt₃Si₄ complexes. Complex <b>1a</b> catalyzes hydrosilyation of benzaldehyde with H₂SiPh₂ to produce diphenyl­(benzyloxy)­silane along with concurrent hydrosilyation and dehydrosilyation of phenyl­(methyl)­ketone. Dehydrogenative coupling of H₂SiPh₂ and phenol is also catalyzed to yield diphenyl­(phenoxy)­silane. The ³¹P­{¹H} NMR spectra of the mixtures during the catalytic reaction show <b>2a</b> as the major Pt-containing species

Cationic Hydridotriplatinum Complex with Bridging Germylene Ligands

Triplatinum complexes with bridging secondary germylene ligands, [{Pt­(PMe₃)}₃(μ-GeR₂)₃] (R = Ph, ^<i>n</i>Bu), were prepared from the reaction of H₂GeR₂ with [Pt­(PMe₃)₄] in a 1:1 ratio. Protonation of the triplatinum complexes with HBF₄ led to formation of the cationic hydride complexes [{Pt­(PMe₃)}₃(μ-GeR₂)₃(μ₃-H)]­BF₄ (R = Ph, ^<i>n</i>Bu). The results of multinuclear NMR spectra and DFT calculations of the cationic complexes revealed that the Pt₃H core has a trigonal-pyramidal structure with rapid exchange of the μ₃-hydride ligand position between the two possible positions on the opposite side of the Pt₃ plane

Ring Expansion of Cyclic Triplatinum(0) Silylene Complexes Induced by Insertion of Alkyne into a Si–Pt Bond

Triangular triplatinum(0) complexes with bridging diarylsilylene ligands, [{Pt­(PMe₃)}₃(μ-SiAr₂)₃] (<b>1</b>: Ar = Ph, <b>2</b>: Ar = C₆H₄F-4), reacted with dimethyl acetylenedicarboxylate to afford new Pt₃ complexes. The equimolar reaction of complex <b>1</b> produced a linear triplatinum complex with μ₂-diphenylsilylene and μ₃-phenyl­(vinylene)­silylene ligands. The latter ligand was formed via migration of a Ph group of the bis­(diphenylsilyl)­ethylene ligand. The reaction of <b>2</b> with the alkyne in a 1:3 molar ratio yielded the product having a disilaplatinacyclic moiety and a Pt center with the donor-stabilized silylene ligand, and they were separated by the coordinated alkyne molecule. A common intermediate having a disilaplatinacyclopentene group was converted into the respective triplatinum complexes, depending on the substituents of the silylene ligand

Cyclic Platina(borasiloxane)s and Platina(siloxane)s and Their Chemical Properties

[Pt­(SiHPh₂)₂(dmpe)] (dmpe = 1,2-bis­(dimethylphosphino)­ethane) reacts with arylboronic acids to produce six-membered platinacycles [Pt­(SiPh₂-O-BAr-O-SiPh₂)­(dmpe)] (Ar = C₆H₄-4-COMe (<b>1a</b>), C₆H₄-4-CF₃ (<b>1b</b>)). X-ray crystallography of <b>1a</b> revealed the structure having a planar six-membered ring, composed of Pt, O, B, and Si atoms. Reaction of H₂O with [Pt­(SiHPh₂)₂(dmpe)] formed a four-membered cyclic complex, [Pt­(SiPh₂-O-SiPh₂)­(dmpe)] (<b>2</b>), which was observed in the initial reaction mixture of 4-acetylphenylboronic acid with [Pt­(SiHPh₂)₂(dmpe)]. Exposure of solutions of [Pt­(SiHPh₂)₂(dmpe)] and of [Pt­(SiHAr₂)₂(PMe₃)₂] (Ar = Ph, C₆H₄-4-Me) to air resulted in the formation of the cyclic platina­(siloxane)­s, [Pt­(O-SiPh₂-O-SiPh₂-O)(dmpe)] (<b>3</b>) and [Pt­(O-SiAr₂-O-SiAr₂-O)­(PMe₃)₂] (<b>4</b>: Ar = Ph; <b>5</b>: Ar = C₆H₄-4-Me), respectively. The six-membered platina­(borasiloxane) <b>1a</b> reacts with H₂GePh₂ and with CF₃CO₂H to release the cyclic borasiloxanes as the products. The former reaction affords [Pt­(GeHPh₂)₂(dmpe)], while the latter produces [Pt­(OCOCF₃)₂(dmpe)] as the Pt-containing products. A similar reaction of HCl with platina­(siloxane) <b>4</b> gives a disiloxanediol via cleavage of the Pt–O bonds. Complex <b>4</b> reacts with H₂SiPh₂ to form a triplatinum complex, [{Pt­(PMe₃)}₃(μ-SiPh₂)₃] (<b>15</b>), which is obtained under milder conditions than the previously reported reaction starting from [Pt­(SiHPh₂)₂(PMe₃)₂]