Comparison of [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ as electrocatalysts for H2 production

Eric Wiedner; Monte Helm

doi:10.1021/om4010669

Comparison of [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺ as electrocatalysts for H₂ production

Eric Wiedner, Monte Helm

Pacific Northwest National Laboratory

Research output: Contribution to journal › Article

8 Citations (Scopus)

Abstract

The complexes [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺, where P^Ph₂N^Ph₂ is 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane, are compared as electro-catalysts for H₂ production under identical experimental conditions. With [(DMF)H]⁺ as the acid in acetonitrile solution, [Pd(P^Ph₂N^Ph₂)₂]²⁺ afforded a turnover frequency (TOF) of 230 s^-1 for formation of H₂ under dry conditions and a TOF of 640 s^-1 when H₂O was added. These rates are similar to the TOFs of 590 s^-1 (dry) and 720 s^-1 (wet) that were previously measured for [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ using [(DMF)H]⁺. The [Ni-(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺ complexes both exhibited large current enhancements when treated with trifluoroacetic acid (TFA). At a TFA concentration of 1.8 M, TOF values of 5670 and 2060 s^-1 were measured for [Ni(P^P ₂N^P ₂)2(CH₃CN)]²⁺ and [Pd(P^Ph ₂N^P 2)₂]²⁺, respectively. The fast rates observed using TFA are, in part, attributed to homoconjugation of TFA in acetonitrile solutions, which decreases the effective pK_a^e of the acid. In support of this hypothesis, dramatically lower rates of H₂ production were observed using p-anisidinium, which has a pK_a^Me value comparable to that of TFA but does not homoconjugate significantly in acetonitrile solutions. (Figure Presented)

Original language	English
Pages (from-to)	4617-4620
Number of pages	4
Journal	Organometallics
Volume	33
Issue number	18
DOIs	https://doi.org/10.1021/om4010669
Publication status	Published - Sep 22 2014

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Trifluoroacetic Acid

electrocatalysts

Electrocatalysts

acids

acetonitrile

Acids

Catalysts

catalysts

augmentation

ASJC Scopus subject areas

Organic Chemistry
Physical and Theoretical Chemistry
Inorganic Chemistry

Cite this

Wiedner, E., & Helm, M. (2014). Comparison of [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺ as electrocatalysts for H₂ production. Organometallics, 33(18), 4617-4620. https://doi.org/10.1021/om4010669

Comparison of [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺ as electrocatalysts for H₂ production. / Wiedner, Eric ; Helm, Monte.

In: Organometallics, Vol. 33, No. 18, 22.09.2014, p. 4617-4620.

Research output: Contribution to journal › Article

Wiedner, E & Helm, M 2014, 'Comparison of [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺ as electrocatalysts for H₂ production', Organometallics, vol. 33, no. 18, pp. 4617-4620. https://doi.org/10.1021/om4010669

Wiedner E , Helm M. Comparison of [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺ as electrocatalysts for H₂ production. Organometallics. 2014 Sep 22;33(18):4617-4620. https://doi.org/10.1021/om4010669

Wiedner, Eric ; Helm, Monte. / Comparison of [Ni(P^Ph₂N^Ph₂)₂(CH₃CN)]²⁺ and [Pd(P^Ph₂N^Ph₂)₂]²⁺ as electrocatalysts for H₂ production. In: Organometallics. 2014 ; Vol. 33, No. 18. pp. 4617-4620.

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title = "Comparison of [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ as electrocatalysts for H2 production",

abstract = "The complexes [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+, where PPh2NPh2 is 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane, are compared as electro-catalysts for H2 production under identical experimental conditions. With [(DMF)H]+ as the acid in acetonitrile solution, [Pd(PPh2NPh2)2]2+ afforded a turnover frequency (TOF) of 230 s-1 for formation of H2 under dry conditions and a TOF of 640 s-1 when H2O was added. These rates are similar to the TOFs of 590 s-1 (dry) and 720 s-1 (wet) that were previously measured for [Ni(PPh2NPh2)2(CH3CN)]2+ using [(DMF)H]+. The [Ni-(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ complexes both exhibited large current enhancements when treated with trifluoroacetic acid (TFA). At a TFA concentration of 1.8 M, TOF values of 5670 and 2060 s-1 were measured for [Ni(PP 2NP 2)2(CH3CN)]2+ and [Pd(PPh 2NP 2)2]2+, respectively. The fast rates observed using TFA are, in part, attributed to homoconjugation of TFA in acetonitrile solutions, which decreases the effective pKae of the acid. In support of this hypothesis, dramatically lower rates of H2 production were observed using p-anisidinium, which has a pKaMe value comparable to that of TFA but does not homoconjugate significantly in acetonitrile solutions. (Figure Presented)",

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N2 - The complexes [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+, where PPh2NPh2 is 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane, are compared as electro-catalysts for H2 production under identical experimental conditions. With [(DMF)H]+ as the acid in acetonitrile solution, [Pd(PPh2NPh2)2]2+ afforded a turnover frequency (TOF) of 230 s-1 for formation of H2 under dry conditions and a TOF of 640 s-1 when H2O was added. These rates are similar to the TOFs of 590 s-1 (dry) and 720 s-1 (wet) that were previously measured for [Ni(PPh2NPh2)2(CH3CN)]2+ using [(DMF)H]+. The [Ni-(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ complexes both exhibited large current enhancements when treated with trifluoroacetic acid (TFA). At a TFA concentration of 1.8 M, TOF values of 5670 and 2060 s-1 were measured for [Ni(PP 2NP 2)2(CH3CN)]2+ and [Pd(PPh 2NP 2)2]2+, respectively. The fast rates observed using TFA are, in part, attributed to homoconjugation of TFA in acetonitrile solutions, which decreases the effective pKae of the acid. In support of this hypothesis, dramatically lower rates of H2 production were observed using p-anisidinium, which has a pKaMe value comparable to that of TFA but does not homoconjugate significantly in acetonitrile solutions. (Figure Presented)

AB - The complexes [Ni(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+, where PPh2NPh2 is 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane, are compared as electro-catalysts for H2 production under identical experimental conditions. With [(DMF)H]+ as the acid in acetonitrile solution, [Pd(PPh2NPh2)2]2+ afforded a turnover frequency (TOF) of 230 s-1 for formation of H2 under dry conditions and a TOF of 640 s-1 when H2O was added. These rates are similar to the TOFs of 590 s-1 (dry) and 720 s-1 (wet) that were previously measured for [Ni(PPh2NPh2)2(CH3CN)]2+ using [(DMF)H]+. The [Ni-(PPh2NPh2)2(CH3CN)]2+ and [Pd(PPh2NPh2)2]2+ complexes both exhibited large current enhancements when treated with trifluoroacetic acid (TFA). At a TFA concentration of 1.8 M, TOF values of 5670 and 2060 s-1 were measured for [Ni(PP 2NP 2)2(CH3CN)]2+ and [Pd(PPh 2NP 2)2]2+, respectively. The fast rates observed using TFA are, in part, attributed to homoconjugation of TFA in acetonitrile solutions, which decreases the effective pKae of the acid. In support of this hypothesis, dramatically lower rates of H2 production were observed using p-anisidinium, which has a pKaMe value comparable to that of TFA but does not homoconjugate significantly in acetonitrile solutions. (Figure Presented)

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10.1021/om4010669