97112-48-6Relevant academic research and scientific papers
Synthesis, structural characterization, and reactions of closo-rhodacarborane anions containing a formal d8 metal vertex
Walker, John A.,Knobler, Carolyn B.,Hawthorne, M. Frederick
, p. 2688 - 2697 (2008/10/08)
Deprotonation of three neutral closo hydrido complexes [(L)2-H-RhC2B9H11] under carefully controlled reaction conditions yields the corresponding isomeric [closo-L2RhC2B9H11]- species. Two of these have been structurally characterized. K[18-crown-6][closo-3,3-(PPh3)2-3,1,2-RhC 2B9H11]·C4H 8O·H2O (2a) crystallized in the monoclinic space group P21/c with a = 13.931 (4) A?, b = 19.954 (5) A?, c = 21.665 (7) A?, β = 100.97 (2)°, V = 5913 A?3, and Z = 4. Data were collected on a Syntex P1 diffractometer (Mo Ka radiation) to a maximum 2θ = 50°, giving 10521 unique reflections, and the structure was solved by conventional heavy-atom techniques. The final discrepancy index was R = 0.062, Rw = 0.072 for 6149 independent reflections. The d8-rhodacarborane anion adopts a closo structure similar to that found in the parent hydrido complex. The Rh-P2 plane lies almost perpendicular to the least-squares plane that passes through the bonding face of the carborane ligand and lies parallel to a line joining the two ortho carbon atoms of this ligand, in accord with theoretical studies. [Me4N][closo-2,2-(PPh3)2-2,1,7-RhC 2B9H11] (2b) crystallized in the triclinic space group P1 with a = 12.355 (13) A?, b = 14.896 (16) A?, c = 15.186 (22) A?, α = 68.00 (9)°, β = 102.86 (6)°, γ = 112.17(5)°, V = 2389 A?3, and Z = 2. Data were collected on a Picker FACS-1 diffractometer (Mo Ka radiation) to a maximum in 2θ of 45°, giving 6180 unique reflections, and the structure was solved by conventional heavy-atom techniques. The final discrepancy index was R = 0.063, Rw = 0.067 for 4761 independent reflections. Unlike 2a, this d8-rhodacarborane anion adopts a significantly distorted icosahedral structure. Carbon atoms of the significantly nonplanar C2B3 face are bent back into the cage and away from the metal. Rh-C bonds in 2b are 2.340 (9) and 2.442 (9) A?, while those in 2a are 2.314 (8) and 2.301 (7) A?. The plane containing RhP2 is nearly perpendicular to the C2B3 face and nearly parallel to the noncrystallographic mirror plane in the carborane ligand (the calculated preferred conformation). Salts of 2a-, 2b-, and [closo-2,2-(PPh3)2-2,1,12-RhC2B 9H11]- (2c) were treated with dilute mineral acids in ethanol to produce the neutral hydrido closo complexes and with π-acceptor ligands L = CO or C2H4 to produce the corresponding [closo-(PPh3)(L)-RhC2B9H11] salts. Anions [closo-3,3-(PPh3)2-3,1,2-IrC2B 9H11]-, [closo-3-(PPh3)-3,3-(H)2-3,1,2-IrC2B 9H11]-, and [closo-3-(PPh3)-3-(CO)-3,1,2-IrC2B9H 11]- have also been prepared.
Reactions at the metal vertex of a monometal metallacarborane cluster. Chemistry of [closo-3,3-(PPh3)2-3-HSO4-3,1,2-RhC 2B9H11] and [coso-3-PPh3-3,3-NO3-3,1,2-RhC2B 9Hn]
Kalb, William C.,Demidowicz, Zenon,Speckman, Donna M.,Knobler, Carolyn,Teller, Raymond G.,Hawthorne, M. Frederick
, p. 4027 - 4036 (2008/10/08)
Reaction of [closo-3,3-(PPh3)2-3-H-3,1,2-RhC2B 9H11] (1) with sulfuric or nitric acid affords [closo-3,3-(PPh3)2-3-HSO4-3,1,2-RhC 2B9H11] (2) or [closo-3-PPh3-3,3-NO3-3,1,2-RhC 2B9H11] (3), respectively. Compound 3 can also be prepared from nitric acid and the dimeric metallacarborane [{closo-Rh(PPh3)(C2B9H11)} 2] or from NO2/N2O4 and 1. Complexes 2 and 3 have been used to prepare other new metallacarboranes, namely, [closo-3-PPh3-3,3-{C(Ph)-C(PPh 3)-C(H)-C-(Ph)}-3,1,2-RhC2B9H11] (5), [{closo-3-PPh3-3-(μ-CN)-3,1,2-RhC 2B9H11}4] (7), [closo-3-PPh3-3-L-3-NO3-3,NO3-3,1,2-RhC 2B9H11] (L = CO (8); L = PPh3 (9)), [closo-3,3-(PMe2Ph)2)2-3-NO 3-3,1,2-RhC2B9H11] (10), and [closo-3-PPh3-3-CO-3-Cl-3,1,2-RhC2B9H11] (11). Complexes 5 and 7 have been characterized by X-ray crystallography. The reactions of these new metallacarboranes described herein are representative of interconversions carried out at a discrete transition-metal vertex of a cluster species. Complex 5 crystallizes in space group P1 with 2 formula units in a cell of dimensions a = 12.763 (6) A?, b = 13.348 (5) A?, c = 14.561 (7) A?, α = 91.58 (3)°, β = 93.72 (3)°, and γ = 74.64 (3)°. Data were collected at -154 °C on a Picker FACS-1 diffractometer with the θ-20 scan method. Least-squares refinement, including anisotropic vibration parameters for Rh and P and isotropic vibration parameters for other non-hydrogen atoms, with each phenyl group described as a rigid group having a single isotropic vibration parameter, led to final conventional agreement indices (on F) of R = 0.048 and Rw = 0.051, based on 4493 unique reflections having I > 3σ(I). The molecule consists of a [C2B9H11]2- cage and a triphenylphosphine ligand bound to the metal atom of the trisubstituted metallapentacycle Rh-C(Ph)-C-(PPh3)-C(H)-C(Ph). Rh-C, Rh-B, B-B, B-C, and C-C distances are normal for a 3,1,2-RhC2B9 closo rhodacarborane fragment, and the pattern of short-long-short C-C bond lengths in the RhC4 ring is reminiscent of a pentasubstituted cis-butadiene. The complex 7-5C6H6 crystallizes in space group P2/a with 4 formula units in a cell of dimensions a = 26.046 (8) A?, b = 15.626 (3) A?, c = 30.355 (8) A?, and β = 106.71 (2)°. Data were collected at -154 °C on a Syntex P1 diffractometer with the θ-20 scan method. Least-squares refinement, including vibration parameters and rigid-group assignments as described above, led to final conventional agreement indices (on F) of R = 0.063 and Rw = 0.078, based on 9732 unique reflections having I > 3σ(I). The molecules consist of four discrete closo phosphinorhodacarborane moieties joined together through their respective metal vertices by cyano ligand bridges. Each tetramer possesses a crystallographic 2-fold axis; the two noncrystallographically equivalent tetramers are very similar. The Rh-Rh separation is approximately 5 A?. Bond distances within each icosahedral fragment are normal for such a closo Rh(III) metallacarborane.
