Thermodynamic studies of [HPt(EtXantphos) 2] + and [(H) 2Pt(EtXantphos) 2] 2 +

Alex Miedaner; James W. Raebiger; Calvin J. Curtis; Susie M. Miller; Daniel L. DuBois

doi:10.1021/om034238i

Thermodynamic studies of [HPt(EtXantphos) ₂] ⁺ and [(H) ₂Pt(EtXantphos) ₂] ₂ ⁺

Alex Miedaner, James W. Raebiger, Calvin J. Curtis, Susie M. Miller, Daniel L. DuBois

Pacific Northwest National Laboratory

Research output: Contribution to journal › Article

52 Citations (Scopus)

Abstract

[HPt(EtXantphos) ₂](PF ₆) (where EtXantphos is 9,9-dimethyl-4,5-bis(diethylphosphino)xanthene) can be prepared by the reduction of Pt(COD)Cl ₂ (where COD is 1,4-cyclooctadiene) with hydrazine in the presence of 2 equiv of the diphosphine ligand followed by exchange of Cl ^- with PF ₆ ^-. Deprotonation of [HPt(EtXantphos) ₂](PF ₆) (pK _a = 27.3 in acetonitrile) leads to the formation of Pt(EtXantphos) ₂, which has been characterized by an X-ray diffraction study. Pt(EtXantphos) ₂ has a distorted tetrahedral geometry. The average chelate bite angle is 108.2°, and the dihedral angle between the two planes formed by the phophorus atoms of each diphophine ligand and platinum is 80.4°. Protonation of [HPt(EtXantphos) ₂] ^- results in the formation of [(H) ₂Pt(EtXantphos ₂] ²⁺, which has a pK _a of 6.8 in acetonitrile. Oxidation of Pt(EtXantphos) ₂ with ferrocenium tetrafluoroborate produces [Pt(EtXantphos) ₂] ²⁺. Pt(EtXantphos ₂] ^2- undergoes two reversible one-electron reductions (E _1/2/II/I) = -0.81 V versus ferrocene and E _1/2(I/0) = ∼0.97 V), and HPt(EtXantphos ₂] ^- undergoes a reversible one-electron oxidation E _1/2(II/III) = -0.23 V). These half-wave potentials and the pK _a values of [HPt(EtXantphos ₂] ^- and [(H) ₂Pt(EtXantphos ₂] ^2- have been used to calculate five additional homolytic and heterolytic bond-dissociation free energies for these two hydride species and for [HPt(EtXantphos ₂] ^2- The extensive thermodynamic characterization of this hydride system provides useful insights into the factors controlling the reactivity of these complexes.

Original language	English
Pages (from-to)	2670-2679
Number of pages	10
Journal	Organometallics
Volume	23
Issue number	11
DOIs	https://doi.org/10.1021/om034238i
Publication status	Published - May 24 2004

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ASJC Scopus subject areas

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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Miedaner, A., Raebiger, J. W., Curtis, C. J., Miller, S. M., & DuBois, D. L. (2004). Thermodynamic studies of [HPt(EtXantphos) ₂] ⁺ and [(H) ₂Pt(EtXantphos) ₂] ₂ ⁺ Organometallics, 23(11), 2670-2679. https://doi.org/10.1021/om034238i

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title = "Thermodynamic studies of [HPt(EtXantphos) 2] + and [(H) 2Pt(EtXantphos) 2] 2 + ",

abstract = "[HPt(EtXantphos) 2](PF 6) (where EtXantphos is 9,9-dimethyl-4,5-bis(diethylphosphino)xanthene) can be prepared by the reduction of Pt(COD)Cl 2 (where COD is 1,4-cyclooctadiene) with hydrazine in the presence of 2 equiv of the diphosphine ligand followed by exchange of Cl - with PF 6 -. Deprotonation of [HPt(EtXantphos) 2](PF 6) (pK a = 27.3 in acetonitrile) leads to the formation of Pt(EtXantphos) 2, which has been characterized by an X-ray diffraction study. Pt(EtXantphos) 2 has a distorted tetrahedral geometry. The average chelate bite angle is 108.2°, and the dihedral angle between the two planes formed by the phophorus atoms of each diphophine ligand and platinum is 80.4°. Protonation of [HPt(EtXantphos) 2] - results in the formation of [(H) 2Pt(EtXantphos 2] 2+, which has a pK a of 6.8 in acetonitrile. Oxidation of Pt(EtXantphos) 2 with ferrocenium tetrafluoroborate produces [Pt(EtXantphos) 2] 2+. Pt(EtXantphos 2] 2- undergoes two reversible one-electron reductions (E 1/2/II/I) = -0.81 V versus ferrocene and E 1/2(I/0) = ∼0.97 V), and HPt(EtXantphos 2] - undergoes a reversible one-electron oxidation E 1/2(II/III) = -0.23 V). These half-wave potentials and the pK a values of [HPt(EtXantphos 2] - and [(H) 2Pt(EtXantphos 2] 2- have been used to calculate five additional homolytic and heterolytic bond-dissociation free energies for these two hydride species and for [HPt(EtXantphos 2] 2- The extensive thermodynamic characterization of this hydride system provides useful insights into the factors controlling the reactivity of these complexes.",

author = "Alex Miedaner and Raebiger, {James W.} and Curtis, {Calvin J.} and Miller, {Susie M.} and DuBois, {Daniel L.}",

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T1 - Thermodynamic studies of [HPt(EtXantphos) 2] + and [(H) 2Pt(EtXantphos) 2] 2 +

AU - Miedaner, Alex

AU - Raebiger, James W.

AU - Curtis, Calvin J.

AU - Miller, Susie M.

AU - DuBois, Daniel L.

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N2 - [HPt(EtXantphos) 2](PF 6) (where EtXantphos is 9,9-dimethyl-4,5-bis(diethylphosphino)xanthene) can be prepared by the reduction of Pt(COD)Cl 2 (where COD is 1,4-cyclooctadiene) with hydrazine in the presence of 2 equiv of the diphosphine ligand followed by exchange of Cl - with PF 6 -. Deprotonation of [HPt(EtXantphos) 2](PF 6) (pK a = 27.3 in acetonitrile) leads to the formation of Pt(EtXantphos) 2, which has been characterized by an X-ray diffraction study. Pt(EtXantphos) 2 has a distorted tetrahedral geometry. The average chelate bite angle is 108.2°, and the dihedral angle between the two planes formed by the phophorus atoms of each diphophine ligand and platinum is 80.4°. Protonation of [HPt(EtXantphos) 2] - results in the formation of [(H) 2Pt(EtXantphos 2] 2+, which has a pK a of 6.8 in acetonitrile. Oxidation of Pt(EtXantphos) 2 with ferrocenium tetrafluoroborate produces [Pt(EtXantphos) 2] 2+. Pt(EtXantphos 2] 2- undergoes two reversible one-electron reductions (E 1/2/II/I) = -0.81 V versus ferrocene and E 1/2(I/0) = ∼0.97 V), and HPt(EtXantphos 2] - undergoes a reversible one-electron oxidation E 1/2(II/III) = -0.23 V). These half-wave potentials and the pK a values of [HPt(EtXantphos 2] - and [(H) 2Pt(EtXantphos 2] 2- have been used to calculate five additional homolytic and heterolytic bond-dissociation free energies for these two hydride species and for [HPt(EtXantphos 2] 2- The extensive thermodynamic characterization of this hydride system provides useful insights into the factors controlling the reactivity of these complexes.

AB - [HPt(EtXantphos) 2](PF 6) (where EtXantphos is 9,9-dimethyl-4,5-bis(diethylphosphino)xanthene) can be prepared by the reduction of Pt(COD)Cl 2 (where COD is 1,4-cyclooctadiene) with hydrazine in the presence of 2 equiv of the diphosphine ligand followed by exchange of Cl - with PF 6 -. Deprotonation of [HPt(EtXantphos) 2](PF 6) (pK a = 27.3 in acetonitrile) leads to the formation of Pt(EtXantphos) 2, which has been characterized by an X-ray diffraction study. Pt(EtXantphos) 2 has a distorted tetrahedral geometry. The average chelate bite angle is 108.2°, and the dihedral angle between the two planes formed by the phophorus atoms of each diphophine ligand and platinum is 80.4°. Protonation of [HPt(EtXantphos) 2] - results in the formation of [(H) 2Pt(EtXantphos 2] 2+, which has a pK a of 6.8 in acetonitrile. Oxidation of Pt(EtXantphos) 2 with ferrocenium tetrafluoroborate produces [Pt(EtXantphos) 2] 2+. Pt(EtXantphos 2] 2- undergoes two reversible one-electron reductions (E 1/2/II/I) = -0.81 V versus ferrocene and E 1/2(I/0) = ∼0.97 V), and HPt(EtXantphos 2] - undergoes a reversible one-electron oxidation E 1/2(II/III) = -0.23 V). These half-wave potentials and the pK a values of [HPt(EtXantphos 2] - and [(H) 2Pt(EtXantphos 2] 2- have been used to calculate five additional homolytic and heterolytic bond-dissociation free energies for these two hydride species and for [HPt(EtXantphos 2] 2- The extensive thermodynamic characterization of this hydride system provides useful insights into the factors controlling the reactivity of these complexes.

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10.1021/om034238i