Synthesis, Characterization, and Interconversion of the Rhenium Polyhydrides [ReH3(η4-NP3)] and [ReH4(η4-NP3)]+ {NP3 = tris[2-(diphenylphosphanyl)ethyl]amine}

Abstract

The rhenium(III) dichloride complex [ReCl 2 (η 4 -NP 3 )]Cl (1) was prepared from [ReCl 3 (CH 3 CN)(PPh 3 ) 2 ] by treatment with the tripodal tetradentate ligand N(CH 2 CH 2 PPh 2 ) 3 (NP 3 ) in ethanol. The reaction of 1 with LiAlH 4 in THF gave the rhenium(III) trihydride [ReH 3 (η 4 -NP 3 )] (2), which was converted into the rhenium(V) tetrahydride [ReH 4 (η 4 -NP 3 )]BPh 4 (3) by protonation in CH 2 Cl 2 with HBF 4 ·OMe 2 , followed by a metathetical reaction with NaBPh 4 . The classical polyhydride nature of 2 and 3, as well as the overall molecular structures in solution, were determined by NMR spectroscopy, 1 H NMR relaxation, and IR spectroscopy. The polyhydride complexes 2 and 3 are stereochemically nonrigid in solution, and the thermodynamic parameters associated with the fluxional processes were determined by variable-temperature NMR

Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides

“…When the M···HO interaction has a large influence on dihydrogen bonding, direct proton transfer to the metal becomes possible, such that a classical hydride is afforded without the formation of an η 2 -H 2 intermediate (pathway b, Scheme ). ,,, The spectroscopic data obtained for Cp*WH 3 (dppe) , and (κ 4 -NP 3 )­ReH 3 [κ 4 -NP 3 = κ 3 - P , P , P , N -N­(CH 2 CH 2 PPh 2 ) 3 ] interacting with fluorinated alcohols evidence the formation of hydrogen bonding to the metal, whereas DFT calculations on Cp*WH 3 (dppe)·HOR F suggested the formation of bifurcated dihydrogen-bonded complexes featuring simultaneous H M ···HO and M···HO interactions but no η 2 -H 2 species on the reaction pathway . In a similar situation, low-temperature proton transfer within the bifurcated dihydrogen-bonded complex Cp*OsH­(dppe)·HOR F yields cis dihydride [Cp*Os­(H) 2 (dppe)] + , which transforms into the trans isomer above 230 K. , …”

Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides

“…When the M···HO interaction has a large influence on dihydrogen bonding, direct proton transfer to the metal becomes possible, such that a classical hydride is afforded without the formation of an η 2 -H 2 intermediate (pathway b, Scheme ). ,,, The spectroscopic data obtained for Cp*WH 3 (dppe) , and (κ 4 -NP 3 )­ReH 3 [κ 4 -NP 3 = κ 3 - P , P , P , N -N­(CH 2 CH 2 PPh 2 ) 3 ] interacting with fluorinated alcohols evidence the formation of hydrogen bonding to the metal, whereas DFT calculations on Cp*WH 3 (dppe)·HOR F suggested the formation of bifurcated dihydrogen-bonded complexes featuring simultaneous H M ···HO and M···HO interactions but no η 2 -H 2 species on the reaction pathway . In a similar situation, low-temperature proton transfer within the bifurcated dihydrogen-bonded complex Cp*OsH­(dppe)·HOR F yields cis dihydride [Cp*Os­(H) 2 (dppe)] + , which transforms into the trans isomer above 230 K. , …”

Selectivity for HCO2– over H2 in the Electrochemical Catalytic Reduction of CO2 by (POCOP)IrH2

“…Figures along this pathway can be seen in Figure S2 in the Supporting Information. The equilibrium between dihydride and dihydrogen has been seen in other organometallic compounds, − with certain Fe compounds similarly preferring dihydride formation . A transition state utilizing the Y-shaped cluster can be seen in Scheme S3 in the Supporting Information, with a higher barrier of 12.8 kcal/mol.…”

Describing Polytopal Rearrangement Processes of Octacoordinate Structures. I. Renewed Insights into Fluxionality of the Rhenium Polyhydride Complex ReH5(PPh3)2(Pyridine)

“…We believe that the lateral and basal three-arm turnstile mechanisms proposed in this work may exist not only in the rhenium polyhydride complexes ,− ,− which are structurally similar to ReH 5 (PPh 3 ) 2 (pyridine) but also in the other metal polyhydride complexes of the high coordination number. ,, This work fills a gap in the fluxionality of octacoordinate compounds ,, which are less explored compared with the fluxionality in the compounds with a lower coordination number, and more work is planned in this direction.…”

“…It features an octacoordinate dodecahedral structure as shown in Figure . Unlike most transition-metal polyhydride complexes with high coordination numbers being nonrigid even at the lowest attainable temperature, ReH 5 (PPh 3 ) 2 (pyridine) and its derivatives along with other rhenium polyhydrides ,,− have shown high conformational rigidity at low temperatures permitting the 1 H NMR characterization of their fluxionality. In 1996, Crabtree, Rüegger, and co-workers observed two consecutive coalescence events in the variable-temperature NMR spectra of ReH 5 (PPh 3 ) 2 (pyridine) and proposed two fluxional mechanisms (see Figure ) to account for this interesting coalescence behavior in the hydride region of the spectra .…”

Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides

“…When the M···HO interaction has a large influence on dihydrogen bonding, direct proton transfer to the metal becomes possible, such that a classical hydride is afforded without the formation of an η 2 -H 2 intermediate (pathway b, Scheme ). ,,, The spectroscopic data obtained for Cp*WH 3 (dppe) , and (κ 4 -NP 3 )­ReH 3 [κ 4 -NP 3 = κ 3 - P , P , P , N -N­(CH 2 CH 2 PPh 2 ) 3 ] interacting with fluorinated alcohols evidence the formation of hydrogen bonding to the metal, whereas DFT calculations on Cp*WH 3 (dppe)·HOR F suggested the formation of bifurcated dihydrogen-bonded complexes featuring simultaneous H M ···HO and M···HO interactions but no η 2 -H 2 species on the reaction pathway . In a similar situation, low-temperature proton transfer within the bifurcated dihydrogen-bonded complex Cp*OsH­(dppe)·HOR F yields cis dihydride [Cp*Os­(H) 2 (dppe)] + , which transforms into the trans isomer above 230 K. , …”

Selectivity for HCO2– over H2 in the Electrochemical Catalytic Reduction of CO2 by (POCOP)IrH2

“…Figures along this pathway can be seen in Figure S2 in the Supporting Information. The equilibrium between dihydride and dihydrogen has been seen in other organometallic compounds, − with certain Fe compounds similarly preferring dihydride formation . A transition state utilizing the Y-shaped cluster can be seen in Scheme S3 in the Supporting Information, with a higher barrier of 12.8 kcal/mol.…”

Describing Polytopal Rearrangement Processes of Octacoordinate Structures. I. Renewed Insights into Fluxionality of the Rhenium Polyhydride Complex ReH5(PPh3)2(Pyridine)

“…We believe that the lateral and basal three-arm turnstile mechanisms proposed in this work may exist not only in the rhenium polyhydride complexes ,− ,− which are structurally similar to ReH 5 (PPh 3 ) 2 (pyridine) but also in the other metal polyhydride complexes of the high coordination number. ,, This work fills a gap in the fluxionality of octacoordinate compounds ,, which are less explored compared with the fluxionality in the compounds with a lower coordination number, and more work is planned in this direction.…”

“…It features an octacoordinate dodecahedral structure as shown in Figure . Unlike most transition-metal polyhydride complexes with high coordination numbers being nonrigid even at the lowest attainable temperature, ReH 5 (PPh 3 ) 2 (pyridine) and its derivatives along with other rhenium polyhydrides ,,− have shown high conformational rigidity at low temperatures permitting the 1 H NMR characterization of their fluxionality. In 1996, Crabtree, Rüegger, and co-workers observed two consecutive coalescence events in the variable-temperature NMR spectra of ReH 5 (PPh 3 ) 2 (pyridine) and proposed two fluxional mechanisms (see Figure ) to account for this interesting coalescence behavior in the hydride region of the spectra .…”

Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides

“…When the M···HO interaction has a large influence on dihydrogen bonding, direct proton transfer to the metal becomes possible, such that a classical hydride is afforded without the formation of an η 2 -H 2 intermediate (pathway b, Scheme ). ,,, The spectroscopic data obtained for Cp*WH 3 (dppe) , and (κ 4 -NP 3 )­ReH 3 [κ 4 -NP 3 = κ 3 - P , P , P , N -N­(CH 2 CH 2 PPh 2 ) 3 ] interacting with fluorinated alcohols evidence the formation of hydrogen bonding to the metal, whereas DFT calculations on Cp*WH 3 (dppe)·HOR F suggested the formation of bifurcated dihydrogen-bonded complexes featuring simultaneous H M ···HO and M···HO interactions but no η 2 -H 2 species on the reaction pathway . In a similar situation, low-temperature proton transfer within the bifurcated dihydrogen-bonded complex Cp*OsH­(dppe)·HOR F yields cis dihydride [Cp*Os­(H) 2 (dppe)] + , which transforms into the trans isomer above 230 K. , …”

Selectivity for HCO2– over H2 in the Electrochemical Catalytic Reduction of CO2 by (POCOP)IrH2

“…Figures along this pathway can be seen in Figure S2 in the Supporting Information. The equilibrium between dihydride and dihydrogen has been seen in other organometallic compounds, − with certain Fe compounds similarly preferring dihydride formation . A transition state utilizing the Y-shaped cluster can be seen in Scheme S3 in the Supporting Information, with a higher barrier of 12.8 kcal/mol.…”

Describing Polytopal Rearrangement Processes of Octacoordinate Structures. I. Renewed Insights into Fluxionality of the Rhenium Polyhydride Complex ReH5(PPh3)2(Pyridine)

“…We believe that the lateral and basal three-arm turnstile mechanisms proposed in this work may exist not only in the rhenium polyhydride complexes ,− ,− which are structurally similar to ReH 5 (PPh 3 ) 2 (pyridine) but also in the other metal polyhydride complexes of the high coordination number. ,, This work fills a gap in the fluxionality of octacoordinate compounds ,, which are less explored compared with the fluxionality in the compounds with a lower coordination number, and more work is planned in this direction.…”

“…It features an octacoordinate dodecahedral structure as shown in Figure . Unlike most transition-metal polyhydride complexes with high coordination numbers being nonrigid even at the lowest attainable temperature, ReH 5 (PPh 3 ) 2 (pyridine) and its derivatives along with other rhenium polyhydrides ,,− have shown high conformational rigidity at low temperatures permitting the 1 H NMR characterization of their fluxionality. In 1996, Crabtree, Rüegger, and co-workers observed two consecutive coalescence events in the variable-temperature NMR spectra of ReH 5 (PPh 3 ) 2 (pyridine) and proposed two fluxional mechanisms (see Figure ) to account for this interesting coalescence behavior in the hydride region of the spectra .…”