Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh₆(PCy₃)₆H₁₂]⁺and [Rh₆(PCy₃)₆H₁₄]⁺

Abstract

A combined structural/EPR/computational chemistry investigation is reported on the two paramagnetic hydrido-cluster salts [Rh 6 4 ] EPR measurements indicate two isomers, the proportion of which change with temperature and deuteration-one axial isomer and one rhombic isomer. DFT calculations on a number of plausible isomers give EPR parameters which fit the experimentally determined rhombic isomer to one in which there is an interstitial hydride in the cluster and thirteen hydride ligands on the surface, while the axial isomer has two dihydrogen-like ligands on the cluster surface. That these isomers lie close in energy comes from both the EPR measurements (as measured from equilibrium constants over a variable temperature range) and DFT calculations. Deuteration of the hydrides should favour the isomer with the lowest zero-point energy and this is the case, with the axial isomer (two D 2 ligands on the surface) being favoured over the rhombic.

Studies on the Reactivity of [Ge9]4− towards [Fe(cot)(CO)3]: Synthesis and Characterization of [Ge8Fe(CO)3]3− and of the Anionic Organometallic Species [Fe(cot)(CO)3]−

“…The relatively small calculated energy gaps between the frontier orbitals of [Ge 8 Fe(CO) 3 ] 3− are consistent with the latter hypothesis (SOMO/SOMO−1: 0.68 eV, and SOMO/LUMO: 1.72 eV). Similar phenomena have recently been reported for other metal cluster species 24. The g factor for 1 is 2.0200, a value, which is very close to that of the free electron.…”

“…Similar phenomena have recently been reported for other metal cluster species. [24] The g factor for 1 is 2.0200, a value, which is very close to that of the free electron.…”

Theoretical and DFT Study of Atypical Pentanuclear [(iPr3P)Ni]5Hn (n = 4, 6, 8) Clusters: What are the Rules?

“…This 76-electron complex reversibly adds two equivalents of H2 to give the 80-electron [{( i Pr3P)Rh]6H16] 2+ system without any gross distortion of the cluster core. 12,[14][15][16][17][18][19][20][21][22][23] Furthermore, the neutral cluster [( i Pr3P)Rh]6H12 adopt a spin-triplet electron configuration. DFT calculations have been used to examine the electronic properties of these Rh clusters.…”

Theoretical and DFT Study of Atypical Pentanuclear [(iPr3P)Ni]5Hn (n = 4, 6, 8) Clusters: What are the Rules?

“…A common feature of these exceptions is that many are supported by a single bulky phosphine donor per metal and hydrides as the remaining ligands; examples are shown in Figure a. − Among them, Weller’s group has reported the chemistry of the [{( i Pr 3 P)­Rh} 6 H 12 ] 2+ cluster, where the 12 hydrides bridge the edges of a Rh 6 octahedron. This 76-electron complex reversibly adds 2 equiv of H 2 to give the 80-electron [{( i Pr 3 P)­Rh] 6 H 16 ] 2+ system without any gross distortion of the cluster core. ,− Furthermore, the neutral cluster [( i Pr 3 P)­Rh] 6 H 12 adopts a spin-triplet electron configuration. DFT calculations have been used to examine the electronic properties of these Rh clusters .…”