6 research outputs found
Triangular Triplatinum Complex with Four Bridging Si Ligands: Dynamic Behavior of the Molecule and Catalysis
A triangular
triplatinum(0) complex with bridging diphenylsilylene
ligands, [{(PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(μ-SiPh<sub>2</sub>)<sub>3</sub>] (<b>1a</b>), reacts with H<sub>2</sub>SiPh<sub>2</sub> to produce the 1:1 adduct, [{PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(H)<sub>2</sub>(μ-SiPh<sub>2</sub>)<sub>4</sub>] (<b>2a</b>), which was isolated and characterized by X-ray crystallography.
Two Pt–Pt bonds of the triangular Pt<sub>3</sub> 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 H<sub>2</sub>SiPh<sub>2</sub> 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 <sup>31</sup>PÂ{<sup>1</sup>H} 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 H<sub>2</sub>SiPh<sub>2</sub> to <b>1a</b> yielded <b>2a</b> with Δ<i>G</i>° = −8.0 kJ mol<sup>–1</sup>, Δ<i>H</i>° = −51.7 kJ
mol<sup>–1</sup>, and Δ<i>S</i>° = −146
J mol<sup>–1</sup> K<sup>–1</sup>. Addition of bisÂ(4-fluorophenyl)Âsilane
and bisÂ(4-methylphenyl)Âsilane to the complexes, which have three bisÂ(4-fluorophenyl)Âsilylene
and bisÂ(4-methylphenyl)Âsilylene ligands, respectively, also occurs
reversibly in the solution, and the diarylsilane with an electron-withdrawing
substituent is favored for the formation of Pt<sub>3</sub>Si<sub>4</sub> complexes. Complex <b>1a</b> catalyzes hydrosilyation of benzaldehyde
with H<sub>2</sub>SiPh<sub>2</sub> to produce diphenylÂ(benzyloxy)Âsilane
along with concurrent hydrosilyation and dehydrosilyation of phenylÂ(methyl)Âketone.
Dehydrogenative coupling of H<sub>2</sub>SiPh<sub>2</sub> and phenol
is also catalyzed to yield diphenylÂ(phenoxy)Âsilane. The <sup>31</sup>PÂ{<sup>1</sup>H} 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, [{(PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(μ-SiPh<sub>2</sub>)<sub>3</sub>] (<b>1a</b>), reacts with H<sub>2</sub>SiPh<sub>2</sub> to produce the 1:1 adduct, [{PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(H)<sub>2</sub>(μ-SiPh<sub>2</sub>)<sub>4</sub>] (<b>2a</b>), which was isolated and characterized by X-ray crystallography.
Two Pt–Pt bonds of the triangular Pt<sub>3</sub> 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 H<sub>2</sub>SiPh<sub>2</sub> 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 <sup>31</sup>PÂ{<sup>1</sup>H} 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 H<sub>2</sub>SiPh<sub>2</sub> to <b>1a</b> yielded <b>2a</b> with Δ<i>G</i>° = −8.0 kJ mol<sup>–1</sup>, Δ<i>H</i>° = −51.7 kJ
mol<sup>–1</sup>, and Δ<i>S</i>° = −146
J mol<sup>–1</sup> K<sup>–1</sup>. Addition of bisÂ(4-fluorophenyl)Âsilane
and bisÂ(4-methylphenyl)Âsilane to the complexes, which have three bisÂ(4-fluorophenyl)Âsilylene
and bisÂ(4-methylphenyl)Âsilylene ligands, respectively, also occurs
reversibly in the solution, and the diarylsilane with an electron-withdrawing
substituent is favored for the formation of Pt<sub>3</sub>Si<sub>4</sub> complexes. Complex <b>1a</b> catalyzes hydrosilyation of benzaldehyde
with H<sub>2</sub>SiPh<sub>2</sub> to produce diphenylÂ(benzyloxy)Âsilane
along with concurrent hydrosilyation and dehydrosilyation of phenylÂ(methyl)Âketone.
Dehydrogenative coupling of H<sub>2</sub>SiPh<sub>2</sub> and phenol
is also catalyzed to yield diphenylÂ(phenoxy)Âsilane. The <sup>31</sup>PÂ{<sup>1</sup>H} 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, [{(PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(μ-SiPh<sub>2</sub>)<sub>3</sub>] (<b>1a</b>), reacts with H<sub>2</sub>SiPh<sub>2</sub> to produce the 1:1 adduct, [{PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(H)<sub>2</sub>(μ-SiPh<sub>2</sub>)<sub>4</sub>] (<b>2a</b>), which was isolated and characterized by X-ray crystallography.
Two Pt–Pt bonds of the triangular Pt<sub>3</sub> 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 H<sub>2</sub>SiPh<sub>2</sub> 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 <sup>31</sup>PÂ{<sup>1</sup>H} 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 H<sub>2</sub>SiPh<sub>2</sub> to <b>1a</b> yielded <b>2a</b> with Δ<i>G</i>° = −8.0 kJ mol<sup>–1</sup>, Δ<i>H</i>° = −51.7 kJ
mol<sup>–1</sup>, and Δ<i>S</i>° = −146
J mol<sup>–1</sup> K<sup>–1</sup>. Addition of bisÂ(4-fluorophenyl)Âsilane
and bisÂ(4-methylphenyl)Âsilane to the complexes, which have three bisÂ(4-fluorophenyl)Âsilylene
and bisÂ(4-methylphenyl)Âsilylene ligands, respectively, also occurs
reversibly in the solution, and the diarylsilane with an electron-withdrawing
substituent is favored for the formation of Pt<sub>3</sub>Si<sub>4</sub> complexes. Complex <b>1a</b> catalyzes hydrosilyation of benzaldehyde
with H<sub>2</sub>SiPh<sub>2</sub> to produce diphenylÂ(benzyloxy)Âsilane
along with concurrent hydrosilyation and dehydrosilyation of phenylÂ(methyl)Âketone.
Dehydrogenative coupling of H<sub>2</sub>SiPh<sub>2</sub> and phenol
is also catalyzed to yield diphenylÂ(phenoxy)Âsilane. The <sup>31</sup>PÂ{<sup>1</sup>H} 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,
[{PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(μ-GeR<sub>2</sub>)<sub>3</sub>] (R = Ph, <sup><i>n</i></sup>Bu), were prepared from the
reaction of H<sub>2</sub>GeR<sub>2</sub> with [PtÂ(PMe<sub>3</sub>)<sub>4</sub>] in a 1:1 ratio. Protonation of the triplatinum complexes
with HBF<sub>4</sub> led to formation of the cationic hydride complexes
[{PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(μ-GeR<sub>2</sub>)<sub>3</sub>(μ<sub>3</sub>-H)]ÂBF<sub>4</sub> (R = Ph, <sup><i>n</i></sup>Bu). The results of multinuclear NMR spectra and DFT calculations
of the cationic complexes revealed that the Pt<sub>3</sub>H core has
a trigonal-pyramidal structure with rapid exchange of the μ<sub>3</sub>-hydride ligand position between the two possible positions
on the opposite side of the Pt<sub>3</sub> 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, [{PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(μ-SiAr<sub>2</sub>)<sub>3</sub>] (<b>1</b>: Ar = Ph, <b>2</b>: Ar = C<sub>6</sub>H<sub>4</sub>F-4), reacted with dimethyl
acetylenedicarboxylate to afford new Pt<sub>3</sub> complexes. The
equimolar reaction of complex <b>1</b> produced a linear triplatinum
complex with μ<sub>2</sub>-diphenylsilylene and μ<sub>3</sub>-phenylÂ(vinylene)Âsilylene ligands. The latter ligand was formed
via migration of a Ph group of the bisÂ(diphenylsilyl)Âethylene 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
[PtÂ(SiHPh<sub>2</sub>)<sub>2</sub>(dmpe)] (dmpe = 1,2-bisÂ(dimethylphosphino)Âethane)
reacts with arylboronic acids to produce six-membered platinacycles
[PtÂ(SiPh<sub>2</sub>-O-BAr-O-SiPh<sub>2</sub>)Â(dmpe)]
(Ar = C<sub>6</sub>H<sub>4</sub>-4-COMe (<b>1a</b>), C<sub>6</sub>H<sub>4</sub>-4-CF<sub>3</sub> (<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 H<sub>2</sub>O with [PtÂ(SiHPh<sub>2</sub>)<sub>2</sub>(dmpe)] formed a four-membered
cyclic complex, [PtÂ(SiPh<sub>2</sub>-O-SiPh<sub>2</sub>)Â(dmpe)]
(<b>2</b>), which was observed in the initial reaction mixture
of 4-acetylphenylboronic acid with [PtÂ(SiHPh<sub>2</sub>)<sub>2</sub>(dmpe)]. Exposure of solutions of [PtÂ(SiHPh<sub>2</sub>)<sub>2</sub>(dmpe)] and of [PtÂ(SiHAr<sub>2</sub>)<sub>2</sub>(PMe<sub>3</sub>)<sub>2</sub>] (Ar = Ph, C<sub>6</sub>H<sub>4</sub>-4-Me) to air
resulted in the formation of the cyclic platinaÂ(siloxane)Âs, [PtÂ(O-SiPh<sub>2</sub>-O-SiPh<sub>2</sub>-O)(dmpe)] (<b>3</b>) and [PtÂ(O-SiAr<sub>2</sub>-O-SiAr<sub>2</sub>-O)Â(PMe<sub>3</sub>)<sub>2</sub>]
(<b>4</b>: Ar = Ph; <b>5</b>: Ar = C<sub>6</sub>H<sub>4</sub>-4-Me), respectively. The six-membered platinaÂ(borasiloxane) <b>1a</b> reacts with H<sub>2</sub>GePh<sub>2</sub> and with CF<sub>3</sub>CO<sub>2</sub>H to release the cyclic borasiloxanes as the
products. The former reaction affords [PtÂ(GeHPh<sub>2</sub>)<sub>2</sub>(dmpe)], while the latter produces [PtÂ(OCOCF<sub>3</sub>)<sub>2</sub>(dmpe)] as the Pt-containing products. A similar reaction of HCl
with platinaÂ(siloxane) <b>4</b> gives a disiloxanediol via cleavage
of the Pt–O bonds. Complex <b>4</b> reacts with H<sub>2</sub>SiPh<sub>2</sub> to form a triplatinum complex, [{PtÂ(PMe<sub>3</sub>)}<sub>3</sub>(μ-SiPh<sub>2</sub>)<sub>3</sub>] (<b>15</b>), which is obtained under milder conditions than the previously
reported reaction starting from [PtÂ(SiHPh<sub>2</sub>)<sub>2</sub>(PMe<sub>3</sub>)<sub>2</sub>]