Kinetics and mechanism of the reaction of methyl acrylate with trans-bis(triethylphosphine)hydridoplatinum(II) nitrate

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The reactions of trans-[PtH(PEt3)2(acetone)]+ and trans-[PtH(PEt3)2(CO)]+ with a variety of acetylenes are described. The geometries of the products with respect to the platinum centre and to the stereochemistry of the alkenyl group have been determined on the basis of their 1H nmr parameters. For reactions with the cation containing acetone, and particularly from a variable temperature 1H nmr study of its reaction with 2-butyne in the presence of water, the insertion pathway is shown to be entirely analogous to that for olefin insertion, involving an initial displacement of the trans ligand by acetylene, isomerization to a cis-like intermediate, migratory insertion rearrangement, and re-combination with an appropriate ligand to give either cis or trans platinum products. The insertion pathway with the carbonyl cation is dependent on the nature of the acetylene; for non-activated or weakly activated acetylenes insertion occurs via five-coordinate intermediates, but with strongly activated acetylenes, the same mechanism as with the acetone cation appears to occur, involving reversible loss of carbon monoxide.

Section: Stereochemistry Of Reaction Productssupporting

confidence: 69%

Section: Introductionmentioning

confidence: 86%

See 1 more Smart Citation

Chemistry of metal hydrides. Part XIX. Stereochemical changes at platinum during the insertion of acetylenes with platinum(II) hydrides

Clark¹,

Fiess²,

Wong³

1977

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“…Thus, it represents a rare and important class of compounds ( 1 (1, 26) which contain both olefin and hydride bonded to the metal. It has been demonstrated (13,14,27) that insertion of an olefin or diene into a transition metal -hydride bond proceeds via coordination of the C=C bond to the metal in a position tt.~tzs to the hydride ligand.…”

Section: Facile Deproto17atiotz Ofmentioning

confidence: 99%

Preparation, characterization, and some reactions of hydridobis(tri-tert- butyl)phosphineplatinum(II) cation containing three-coordinate platinum

Goel¹,

Srivastava²

1983

Removal of the chloride ligand from trans-PtHCl[P(t-Bu)3]2 by a noncoordinating anion affords the complexes trans-[PtH{P(t-Bu)3}2]X (X = PF6, BF4, ClO4, SO3CF3), 1a, 1b, 1c, and 1d respectively, which contain the cationic hydride in which platinum is formally three-coordinate. Complexes 1 react with several σ-donor neutral ligands, L, to give the square-planar complexes trans-[PtHL{P(t-Bu)3}2]X. No reaction occurs with H2C=CH2 or F2C=CF2 but (NC)2C=C(CN)2 reacts with 1c to give an air-stable complex trans-[PtH{(NC)2C=C(CN)2}{P(t-Bu)3}2]ClO4 which is indicated to contain π-bonded (NC)2C=C(CN)2. Neither PhC≡CPh nor MeO2CC≡CCO2 reacts with 1 but HC≡CH seems to react reversibly to form the four-coordinate species trans-[PtH(HC≡CH){P(t-Bu)3}2]+, which could not be isolated. In marked contrast to the behaviour of previously reported cationic platinum(II) hydrides, addition of an equivalent of PCy3 of P(t-Bu)3 to an acetone solution of 1 results in its deprotonation and gives the platinum(0) complex Pt[P(t-Bu)3]2 quantitatively. Deprotonation of 1 also occurs upon treatment with NH3, Me2S, and NaOMe in acetone.

“…Recent semiempirical SCF-MO calculations ( 5 ) appear to be consistent with this, although unfortunately many of the models used for these calculations are inconsistent with recent experimental work (2,6). The purpose of this paper is to present and discuss evidence concerning the nature of the actual insertion step and of the transition states that may be involved.…”

Section: Introductionmentioning

confidence: 90%

Chemistry of metal hydrides. Part XX. The nature of the insertion rearrangement of acetylenes with platinum(II) hydrides

Attig¹,

Clark²,

Wong³

1977

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. Can. J. Chem. 55, 189 (1977). The reactions of platinum(I1) hydrides, trans-PtHXL,, where X = NO3, Cl or CH,OH, and L = PEt, or tricyclohexylphosphine, with disubstituted acetylenes, R,C=CR,, have been examined under a variety of conditions. From spectroscopic parameters, the gross geometry at platinum as well as the geometry of the resulting alkenyl groups in the products have been determined. The observation that all alkenyl groups have a cis geometry is consistent with a migratory insertion step involving a four-centred transition state, in which the disposition of the acetylene relative to the Pt-H bond appears to be dependent on the Pt-H bond polarity. Evidence is presented to demonstrate that this polarity depends on several factors including solvent, and ligands on Pt(I1). For L = tricyclohexylphosphine, the occurrence of a side reaction which competes with insertion and which leads to a Pt(0) acetylene complex is also demonstrated, and other interesting reactions are described.T. G. ATTIG, H. C. CLARK et C. S. WONG. Can. J. Chem. 55, 189(1977). On a etudie, dans diverses conditions, les reactions des hydrures de platine(II), PtHXL, trnns (ou X = NO,, C1 ou CH,OH et L = PEt, ou tricyclohexylphosphine) avec les acetylenes disubstitues R,C-=CR,. En se basant sur des parametres spectroscopiques, on a determine, pour les produits, la geometrie globale au niveau du platine de mtme que la geometrie des groupes alkenyles rPsultants. Le fait que tous les groupes alkenyles possedent une geometrie cis est en accord avec une etape d'insertion migratoire impliquant un Ctat de transition a quatre centres dans lequel l'orientation de l'acetylene par rapport au lien Pt-H semble dependre de la polarite du lien Pt-H. On presente des donnees pour dimontrer que cette polarite depend de plusieurs facteurs incluant le solvant et les ligands attaches au Pt(1I). Pour L = tricyclohexylphosphine, l'existence d'une rCaction secondaire qui est en competition avec l'insertion et qui conduit a un complexe Pt(0) acktylene peut aussi ttre demontree et on decrit d'autres reactions intkressantes.[Traduit par le journal]