The reaction of the dinuclear phosphinito bridged complex [(PHCy2)Pt(mu-PCy2){kappa P-2,O-mu-P(O)Cy-2}Pt(PHCy2)](Pt-Pt) (1) with phenylacetylene affords the eta(1)-alkenyl-mu,eta(1):eta(2)-alkynyl complex [(eta(1)-trans-(Ph)HC=CH)(PHCy2)Pt(mu-PCy2)(mu,eta(1):eta(2)-PhC?C)Pt{kappa P-P(O)Cy-2}(PHCy2)] (4) displaying a sigma-bonded 2-phenylethenyl ligand and an alkynyl (mu-kappa C-alpha:eta(2)) bridge between the platinum atoms. Complex 4 was shown to form in two steps: initially, the attack of the first molecule of phenylacetylene gives the sigma-acetylide complex [(PHCy2)(eta(1)-PhC=C)Pt-1(mu-PCy2)Pt-2(PHCy2){kappa P-P(OH)Cy-2}](Pt-Pt) (5) featuring an intramolecular pi-type hydrogen bond between the POH and the C?C triple bond; fast reaction of 5 with a second molecule of phenylacetylene results in the oxidative addition of the terminal C-H bond of the second alkyne to Pt-1 that, after rearrangements, leads to 4. When left in solution for two weeks, complex 4 spontaneously isomerizes completely to [(PHCy2)(eta(1)-trans-(Ph)HC=CH)Pt(mu-PCy2){kappa P-2,O-mu-P(O)Cy-2}Pt(eta(1)-PhC=C)(PHCy2)] (7) displaying a 2-phenylethenyl ligand and a phenylethynyl group both sigma-bonded to the metal. Density functional calculations at the B3LYP/LACV3P++**//DFT/LACVP* level were carried out to study the thermodynamics of the formation of all considered complexes and to trace the mechanism of formation of the observed products.
Double addition of phenylacetylene onto the mixed bridge phosphinito–phosphanido Pt(i) complex [(PHCy2)Pt(μ-PCy2){κ2P,O-μ-P(O)Cy2}Pt(PHCy2)](Pt–Pt)
Tolbatov, Iogann;
2020
Abstract
The reaction of the dinuclear phosphinito bridged complex [(PHCy2)Pt(mu-PCy2){kappa P-2,O-mu-P(O)Cy-2}Pt(PHCy2)](Pt-Pt) (1) with phenylacetylene affords the eta(1)-alkenyl-mu,eta(1):eta(2)-alkynyl complex [(eta(1)-trans-(Ph)HC=CH)(PHCy2)Pt(mu-PCy2)(mu,eta(1):eta(2)-PhC?C)Pt{kappa P-P(O)Cy-2}(PHCy2)] (4) displaying a sigma-bonded 2-phenylethenyl ligand and an alkynyl (mu-kappa C-alpha:eta(2)) bridge between the platinum atoms. Complex 4 was shown to form in two steps: initially, the attack of the first molecule of phenylacetylene gives the sigma-acetylide complex [(PHCy2)(eta(1)-PhC=C)Pt-1(mu-PCy2)Pt-2(PHCy2){kappa P-P(OH)Cy-2}](Pt-Pt) (5) featuring an intramolecular pi-type hydrogen bond between the POH and the C?C triple bond; fast reaction of 5 with a second molecule of phenylacetylene results in the oxidative addition of the terminal C-H bond of the second alkyne to Pt-1 that, after rearrangements, leads to 4. When left in solution for two weeks, complex 4 spontaneously isomerizes completely to [(PHCy2)(eta(1)-trans-(Ph)HC=CH)Pt(mu-PCy2){kappa P-2,O-mu-P(O)Cy-2}Pt(eta(1)-PhC=C)(PHCy2)] (7) displaying a 2-phenylethenyl ligand and a phenylethynyl group both sigma-bonded to the metal. Density functional calculations at the B3LYP/LACV3P++**//DFT/LACVP* level were carried out to study the thermodynamics of the formation of all considered complexes and to trace the mechanism of formation of the observed products.
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