Transformation of a Trialkynylphosphine Oxide to a 2-Alkylidene-1,2 dihydro-3-phosphete P-Oxide Ligand by Pt-H Addition and Rearrangement Reactions. Activation of Molecular Hydrogen by a Platinum(II) Complex

Addition of the Pt—H bond of [trans-Pt(H)(PEt3)2(THF)]+ to the C≡C triple bond of the alkynyl substituent of O=PPh2(C≡CPh) occurs regioselectively to give a Pt, P μ-alkenylidene complex. Similar addition of a Pt—H bond to the trialkynylphosphine oxide O=P(C≡CCMe3)3 presumably occurs also, but a facile insertion rearrangement takes place to form a novel 2-alkylidene-1,2-dihydro-3-phosphete P-oxide ligand. Complexes containing this heterocyclic alkenyl ligand react with molecular hydrogen at -78 °C and at atmospheric pressure to give neutral monohydride complexes. The X-ray structure of one such complex has been determined: {trans-Pt[C=C(CMe3)P(OBF3)(C≡CCMe3)C==C(CMe3)(H)][P(n-Pr)3]2(H)}; monoclinic; P21/c; Z = 4;a = 11.006 (4) Å, b = 21.435 (5) Å, c = 19.518 (5) Å; β= 100.72 (3)°. Other reaction chemistry and a discussion of proposed mechanisms for the formation of these unusual complexes are reported. © 1989, American Chemical Society. All rights reserved.

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Author Andrew T. McPhail Chemistry