The aquorhodium(II) ion

Spectroscopic and structural investigation of the unbridged dirhodium cation [Rh2(CH3CN)10]4+

“…Further proton inventory studies with various substrates and with modified and mutant enzymes will be important, as has been suggested by Schowen.1 23 of the dirhodium aquo species [Rh2(H2O)10]4+ from a reduction of [Rh(H20)5Cl]2+ by [Cr(H20)6]2+.1 Subsequent claims2 that the Rh2(aq)4+ species could also be prepared by the action of strong acids on solutions of dirhodium tetraacetate remain unsubstantiated,3 although the reverse reaction of Rh24+(aq) with sodium acetate to produce Rh2(02CCH3)4(H20)2 proceeds in fairly high yield.1 The dimeric formulation of the aquo cation is based upon solution spectroscopic and magnetic properties as well as by its ion exchange behavior, but attempts to precipitate or crystallize the material have failed to produce a solid form of [Rh2-(H2O)10]4+. 1,4 Since this early work, numerous binuclear rhodium(II) compounds have been prepared and studied in solution as well as by X-ray crystallography.5 Among these are the partially solvated Communications to the Editor reagents.7 Several laboratories have reported parallel chemistry for Mo2(02CCH3)4.6a'10 Structural determinations of [M2-(02CCH3)2(L)4(L')2](BF4)2 (M = Rh, Mo, L = L' = CH3CN; M = Rh, L = CHjCN, V = py) revealed that the dinuclear cations possess a cisoid arrangement of bridging acetate groups and six molecules of coordinated solvent; two are axially ligated, and four occupy the remaining equatorial positions.8 The solvent ligands are easily displaced as demonstrated by NMR studies7 and substitution reactions." One of our current interests is the preparation of heteronuclear coordination and carbonyl cluster compounds by ion-molecule reactions and by condensation of pairs of activated binuclear metal complexes, especially charged species that may undergo clusterification by cation-anion annihilation.…”

“…1984Chem. , 23, 1798 (b) Baranovskii,1. B.; Golubnichaya, M. A.; Dikareva, L. M.; Shchelokov, R. N. Russ. J. Inorg.…”

“…A point of considerable interest in the structure of the new compound is the value of 2.624 (1) A for the Rh-Rh separation. This distance is much shorter than the unsupported Rh-Rh bonds found in Rh2(dmg)4(PPh3)2 (2.936 (2) A)20 gI2]2+ (2.785 (2) A)21 but somewhat longer than (17) (a) Bino, A.; Cotton, F. A.; Fanwick, P. E. Inorg.…”

“…The heterogeneous oxidation of propylene by 02 in the presence of ammonia to yield acrylonitrile (i.e., the "ammoxidation" of propylene) constitutes the largest volume example of an allylic oxidation process in industrial practice.1 This process, developed by SOHIO,2 now accounts for virtually all of the approximately 4000000 tons of acrylonitrile produced annually worldwide. The reaction (eq 1) is typically carried out at temperatures of 400-500 CH2=CH-CH3 + NH3 + 3/2o2 -CH2=CH-C=N + 3H20 (1) °C with a catalyst of the minimal composition (Bi203*nMo03); under these conditions, the yield of acrylonitrile is ca. 65%.…”

Homoleptic Rhodium Pyridine Complexes for Catalytic Hydrogen Oxidation

“…A crystal of [Rh­( tBu py) 4 (thf) 2 ]­[BAr F 4 ] 2 was characterized by X-ray diffraction (Figure ). The complex is monomeric, as opposed to other Rh­(II)­L 4 complexes of simple ligands (L = RNC, RCN, and H 2 O). − Monomeric Rh­(II) species typically require complicated ligands. − The resistance of [Rh­( R py) 4 ] 2+ toward dimerization highlights the steric protection afforded by the four pyridine ligands, which form a sort of picket fence.…”