Limits...
Homolytic N-H activation of ammonia: hydrogen transfer of parent iridium ammine, amide, imide, and nitride species.

Scheibel MG, Abbenseth J, Kinauer M, Heinemann FW, Würtele C, de Bruin B, Schneider S - Inorg Chem (2015)

Bottom Line: The redox series [Ir(n)(NHx)(PNP)] (n = II-IV, x = 3-0; PNP = N(CHCHPtBu2)2) was examined with respect to electron, proton, and hydrogen atom transfer steps.The experimental and computational results suggest that the Ir(III) imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective Ir(II) amido and Ir(IV) nitrido species.N-H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E-H bond activation.

View Article: PubMed Central - PubMed

Affiliation: Institut für Anorganische Chemie, Georg-August-Universität , Tammannstraße 4, 37077 Göttingen, Germany.

ABSTRACT
The redox series [Ir(n)(NHx)(PNP)] (n = II-IV, x = 3-0; PNP = N(CHCHPtBu2)2) was examined with respect to electron, proton, and hydrogen atom transfer steps. The experimental and computational results suggest that the Ir(III) imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective Ir(II) amido and Ir(IV) nitrido species. N-H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E-H bond activation.

No MeSH data available.


Molecular structures of 6 (top), 7 (center),and 8 (bottom) from X-ray diffraction with thermal ellipsoidsat the 50% probability level (carbon bound hydrogen atoms and onemolecule of THF in 7 are omitted for clarity).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4597254&req=5

fig4: Molecular structures of 6 (top), 7 (center),and 8 (bottom) from X-ray diffraction with thermal ellipsoidsat the 50% probability level (carbon bound hydrogen atoms and onemolecule of THF in 7 are omitted for clarity).

Mentions: The molecular structures of 6–8 in the solid state were derived by single crystal X-ray diffraction(Figure 4), confirming square-planar coordinationof the Ir ions in all cases. The structural features within the PNPpincer backbones of iridium(II) complexes 6 and 7, such as C–N and C–C bond lengths (Table 1), strongly resemble those of the chloro analogue 5. Similarly, oxidation to iridium(III) exhibits the sametrends for 8 and chloro complex 9, i.e.shortening of Ir–N and C–C bonds and lengthening ofC–N bonds. This trend indicates increased N to Ir π-donationupon oxidation of iridium(II) (S = 1/2) to iridium(III)(S = 0) as a result of the π*-antibonding characterof the SOMO (see Supporting Information). The Ir–NH2 distance of 6 (1.9521(17)Å) compares well with other parent iridium amido complexes witha nitrogen donor ligand in the trans position (1.92–1.95Å)29 and is significantly shorterthan examples with C-donor ligands trans to amide (2.00–2.19Å).14,47,50 The Irn+–NHx distancedecreases within the series 7 (x = 3, n = 2), 6 (x = 2, n = 2), and 8 (x = 2, n = 3) by more than 0.2 Å due to increasingly covalentσ- and π-bonding with the metal ion, resulting in a particularlyshort bond for 8 (1.900(2) Å). In comparison, theIr–N triple bond length of [Ir(N)(PNP)]+ (1) was reported to be at 1.678(4) Å.31


Homolytic N-H activation of ammonia: hydrogen transfer of parent iridium ammine, amide, imide, and nitride species.

Scheibel MG, Abbenseth J, Kinauer M, Heinemann FW, Würtele C, de Bruin B, Schneider S - Inorg Chem (2015)

Molecular structures of 6 (top), 7 (center),and 8 (bottom) from X-ray diffraction with thermal ellipsoidsat the 50% probability level (carbon bound hydrogen atoms and onemolecule of THF in 7 are omitted for clarity).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4597254&req=5

fig4: Molecular structures of 6 (top), 7 (center),and 8 (bottom) from X-ray diffraction with thermal ellipsoidsat the 50% probability level (carbon bound hydrogen atoms and onemolecule of THF in 7 are omitted for clarity).
Mentions: The molecular structures of 6–8 in the solid state were derived by single crystal X-ray diffraction(Figure 4), confirming square-planar coordinationof the Ir ions in all cases. The structural features within the PNPpincer backbones of iridium(II) complexes 6 and 7, such as C–N and C–C bond lengths (Table 1), strongly resemble those of the chloro analogue 5. Similarly, oxidation to iridium(III) exhibits the sametrends for 8 and chloro complex 9, i.e.shortening of Ir–N and C–C bonds and lengthening ofC–N bonds. This trend indicates increased N to Ir π-donationupon oxidation of iridium(II) (S = 1/2) to iridium(III)(S = 0) as a result of the π*-antibonding characterof the SOMO (see Supporting Information). The Ir–NH2 distance of 6 (1.9521(17)Å) compares well with other parent iridium amido complexes witha nitrogen donor ligand in the trans position (1.92–1.95Å)29 and is significantly shorterthan examples with C-donor ligands trans to amide (2.00–2.19Å).14,47,50 The Irn+–NHx distancedecreases within the series 7 (x = 3, n = 2), 6 (x = 2, n = 2), and 8 (x = 2, n = 3) by more than 0.2 Å due to increasingly covalentσ- and π-bonding with the metal ion, resulting in a particularlyshort bond for 8 (1.900(2) Å). In comparison, theIr–N triple bond length of [Ir(N)(PNP)]+ (1) was reported to be at 1.678(4) Å.31

Bottom Line: The redox series [Ir(n)(NHx)(PNP)] (n = II-IV, x = 3-0; PNP = N(CHCHPtBu2)2) was examined with respect to electron, proton, and hydrogen atom transfer steps.The experimental and computational results suggest that the Ir(III) imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective Ir(II) amido and Ir(IV) nitrido species.N-H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E-H bond activation.

View Article: PubMed Central - PubMed

Affiliation: Institut für Anorganische Chemie, Georg-August-Universität , Tammannstraße 4, 37077 Göttingen, Germany.

ABSTRACT
The redox series [Ir(n)(NHx)(PNP)] (n = II-IV, x = 3-0; PNP = N(CHCHPtBu2)2) was examined with respect to electron, proton, and hydrogen atom transfer steps. The experimental and computational results suggest that the Ir(III) imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective Ir(II) amido and Ir(IV) nitrido species. N-H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E-H bond activation.

No MeSH data available.