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

Abstract

. 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]

Synthesis of a Novel Volatile Platinum Complex for Use in CVD and a Study of the Mechanism of Its Thermal Decomposition in Solution

“…Each Pt is essentially square-planar coordinate in which the two σ-bound carbons are oriented cis to one another and each is trans to a coordinated π-bond. The stereochemistry about the terminal double bond of the tetraphenylbutadienyl ligand is trans. −

4 ORTEP drawing of one of the two independent molecules in the asymmetric unit of 8 .

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Hydrido Complexes of Palladium

“…In contrast, the vinylic complexes derived from the cis addition of similar Pt hydrides to acetylenes often incorporated the more electron-withdrawing substituent of the acetylene on the α-carbon atom …”

“…In contrast, the vinylic complexes derived from the cis addition of similar Pt hydrides to acetylenes often incorporated the more electron-withdrawing substituent of the acetylene on the R-carbon atom. 221 No firm conclusion was drawn regarding mechanisms of the Pd-H bond addition to the triple bond. However, it was demonstrated that the insertion occurred via an intermediate in which the hydrido ligand remained on the metal.…”