The water-soluble cluster cation [H3Ru3(C6H6)(C6Me6)2(O)]+: Improved synthesis, aerobic oxidation, electrochemical properties and ligand exchange studies

Abstract

The synthesis of the trinuclear cluster cation [H 3 Ru 3 (C 6 H 6 )(C 6 Me 6 ) 2 (O)] + (1) has been considerably improved by changes in the NaBH 4 addition step and by introducing chromatographic methods; in addition, the redox and ligand exchange properties of 1 have been studied. Although exposure of an aqueous solution of 1 to air yields the oxidised cluster [H 2 Ru 3 (C 6 H 6 )(C 6 Me 6 ) 2

High Hydride Count Rhodium Octahedra, [Rh6(PR3)6H12][BArF4]2: Synthesis, Structures, and Reversible Hydrogen Uptake under Mild Conditions

“…Both complexes are stable in CD 2 Cl 2 solutions for weeks under rigorous exclusion of air and moisture. The 31 broad resonance at δ -25.44 ppm (fwhm ) 46 Hz) that integrates to 12 H relative to both the i Pr protons and the [BAr F 4 ]aromatic protons. Correct integration of hydride signals can often be problematic due to slow relaxation, and long delays between pulses (5 s) and a large number of scans were used to ensure that the true integral value was obtained.…”

“…Of course, in the absence of a neutron diffraction study, the assignment of an interstitial hydride must remain plausible but tentative, especially as examples exist of instances where interstitial hydrides have been originally proposed but later proven to be, in fact, located on the cluster surface. 71 The room-temperature 31 P{ 1 H} NMR spectra for both 1b and 2b show broad environments, which for 1b resolves into a doublet J(RhP) ) 140 Hz. Within error, the hydrodynamic radii of 1b and 2b as calculated using PGSE in CD 2 Cl 2 solutions are the same as for 1a/2a [9.5(3) and 10.3(5) Å, 3 respectively].…”

“…As discussed in the Introduction, clusters that form under kinetic conditions are relatively unusual, and the attractive time scales (5 days) and moderate temperatures involved (313-323 K) in the formation of 1a and 2a afford a rare opportunity to probe a cluster selfassembly process using NMR spectroscopy. Addition of H 2 (∼4 atm) to a fluorobenzene solution of [Rh(P i Pr 3 ) 2 (nbd)][BAr F 4 ] in a sealed J. Youngs tube initially results in the formation of the almost colorless dihydrogen/dihydride complexes [Rh-(P i Pr 3 ) 2 (H) 2 (η 2 -H 2 ) x ][BAr F 4 ] (x ) 1 or 2), as shown by a broad 31 P{ 1 H} NMR resonance at δ 63 ppm and a very broad signal at δ -5.8 ppm in the 1 H NMR spectrum at high field. 39 Following the reaction by NMR spectroscopy during gentle heating at 313 K over 5 days revealed a number of intermediate species, along with the final product 1b that forms from addition of H 2 to 1a.…”

“…An alternative method is to reduce a mononuclear transition metal halide with a hydride source such as HSnBu 3 or H 3 SiPh to afford compounds such as Zr 6 (PR 3 ) 4 Cl 14 H 4 , and [(η 5 -C 5 Me 4 SiMe 3 )LuH 2 ] 6 , , respectively. Kinetic routes to related metallaborane cluster species through reduction of mononuclear cyclopentadienyl halides have also been developed, and hydrido clusters can also be synthesized under kinetic conditions from condensation of bimetallic hydride complexes with monometallic fragments. −

2 Examples of Cluster Buildup under Kinetic Conditions

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“…Kinetic routes to related metallaborane cluster species through reduction of mononuclear cyclopentadienyl halides have also been developed, 28 and hydrido clusters can also be synthesized under kinetic conditions from condensation of bimetallic hydride complexes with monometallic fragments. [29][30][31] We report in this paper the synthesis under mild conditions of a new class of octahedral cluster, [Rh 6 (PR 3 ) 6 H 12 ] 2+ . Such clusters bridge the gap between early and later transition metals inasmuch as they are composed of late transition metal fragments {Rh(PR 3 )} but have molecular geometries and electronic structures that are more closely related to those of the early octahedral transition metal clusters.…”