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

Article abstract of DOI:10.1021/om00106a022

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≡CCMe ₃)C=C(CMe₃)(H)][P(n-Pr)₃]₂(H)}; monoclinic; P2₁/c; Z = 4; a = 11.006 (4) A?, b = 21.435 (5) A?, c = 19.518 (5) A?; β = 100.72 (3)°. Other reaction chemistry and a discussion of proposed mechanisms for the formation of these unusual complexes are reported.