Crystal and molecular structure of chloro(dioxygen)tris(triphenylphosphine)rhodium(I)

Abstract

The compound chloro(dioxygen)tris(triphenylphosphine)rhodium(I), RhCl(02)(P(C6H5)3)3-2CH2Cl2, has been identified as one of the species formed by the oxygenation of RhCl(P(C6H5)3)3. The crystal structure of this compound has been determined from three-dimensional x-ray data collected on a manual four-circle diffractometer at room temperature. The compound crystallizes in the orthorhombic space group Pbca with 8 molecules per unit cell (pobsd = 1.411, pcalcd = 1.416 g cm"3). The axial parameters are a = 24.817 (4), b = 18.359 (2), c = 23.200 (4) A. Least-squares refinement of absorptionand decomposition-corrected intensity data converged at a conventional R factor of 0.049 based on 2073 significant reflections. The geometry about the rhodium atom may be described as a trigonal bipyramid with three phosphine ligands occupying one equatorial (Rh-P(2) = 2.357 (3) Á) and the two axial positions (Rh-P(l) = 2.365 (4), Rh-P(3) = 2.391 (4) Á). The remaining equatorial sites are occupied by the chlorine (Rh-Cl(l) = 2.401 (3) Á) and the dioxygen molecule. The dioxygen molecule is tt bonded and a slight asymmetry in the rhodium-oxygen bond lengths (Rh-O(l) = 2.081 (8), Rh-0(2) = 2.005 (8) Á) is observed. One of the dichloromethanes of crystallization appears to be hydrogen bonded to the coordinated dioxygen.

Rhodium‐103 NMR of [Rh(X)(PPh3)3] [X = Cl, N3, NCO, NCS, N(CN)2, NCBPh3, CNBPh3, CN] and derivatives containing CO, isocyanide, pyridine, H2 and O2. Ligand, solvent and temperature effects

“…The complexes [Rh(X) PPh 3 3 2 , NCS, NCO, N 3 , Cl 25 and the trans isomer with X D CN, CNBPh 3 ] was prepared by dissolving [Rh(X) PPh 3 3 ] (7-11 mg giving 0.010-0.020 M in 0.6 ml) in the NMR solvent (toluene-d 8 /toluene or CDCl 3 ) containing ¾10% (v/v) of pyridine; the dihydro complexes 26 were prepared by bubbling H 2 through solutions containing [Rh(X) PPh 3 3 ] or [Rh(X) PPh 3 2 (py)] for 1-2 min; the O 2 complexes 27 were prepared by filling the NMR tube above the solution (of [Rh(X) PPh 3 3 ] (with ¾0.06 M PPh 3 to enhance stability) or [Rh(X) Ph 3 2 (py)]) with O 2 and shaking for 10-20 s. The coordination geometry of the dihydro complexes [Rh(X) H 2 PPh 3 2 (py)] was established to be trans (i.e. phosphines in axial positions, hydrides trans to X and pyridine) and of the dioxygen complexes [Rh(X) O 2 PPh 3 2 (py)] was established to be cis (one phosphine axial, one equatorial, positioned trans to oxygen) by 31 P NMR, which showed a single doublet for the dihydro complexes and two doublets of doublets for the dioxygen complexes (see Table 1 …”

Rhodium complexes with N-phenyl anthranilic acid ligands as catalysts for hydrogenation

“…The results obtained with the complex in silicon grease seem to suggest that indeed air induces the formation of metal particles and that in the complexes that are well kept under N 2 no Rh(0) is present. The formation of Rh(0) might be explained by the assumption that in contact with air by the catalytic action of Rh the PAA is oxidised and that the oxidised ligand subsequently reduces the Rh [25][26][27][28][29]. The oxidation of the amine group to a nitro group is most likely.…”

Hydroboration, Diboration, Silylboration, and Stannylboration

“…Thus, handling the catalyst under argon or air results in different regioselectivity (entries 1 and 2) [19,20]. The changes in regioselectivity resulted from lowering the triphenylphosphine-to-rhodium ratio via oxidation of phosphine to the oxide (Scheme 1-3) [21]. Thus, the in situ preparation of the catalyst from [RhCl(cod)] 2 and a limited amount of phosphine (entries 3-7) [19][20][21][22][23] or the use of an air stable π-allylrhodium complex (entry 8) [24] is a convenient alternative, but the use of a large excess of the ligand should be avoided because of its higher coordination ability to the metal than that of alkenes.…”

“…The changes in regioselectivity resulted from lowering the triphenylphosphine-to-rhodium ratio via oxidation of phosphine to the oxide (Scheme 1-3) [21]. Thus, the in situ preparation of the catalyst from [RhCl(cod)] 2 and a limited amount of phosphine (entries 3-7) [19][20][21][22][23] or the use of an air stable π-allylrhodium complex (entry 8) [24] is a convenient alternative, but the use of a large excess of the ligand should be avoided because of its higher coordination ability to the metal than that of alkenes. An addition of phosphine to [Rh(cod) 2 ]BF 4 generates a highly active species to catalyze hydroboration even at temperatures lower than 0°C (entries 9 and 10) [22,25].…”

“…The rhodium complex gives a complex mixture for alicyclic dienes, but Rh 4 (CO) 12 is recognized to be the best catalyst for 1,4-hydroboration of 1,3-cyclohexadiene (92%). The uncatalyzed hydroboration of allenes suffers from the formation of a mixture of monohydroboration and dihydroboration products or a mixture of four possible regioisomers (19)(20)(21)(22) [48]; however, the phosphine ligand on the platinum(0) catalyst controls the regio-and stereoselectivity so as to provide 21 or 22 for alkoxyallenes, and 20 or 22 for aliphatic and aromatic allenes (Scheme 1-7) [49]. The addition to aliphatic and aromatic allenes with Pt(dba) 2 /2P t Bu 3 occurs at the internal double bond to selectively provide 20, whereas the electronic effect of MeO or TBSO play a major role in influencing the course of the reaction as evidenced by the preferential formation of the terminal cis-isomer (21) by way of attack from the less-hindered side of the allenes (Z>84-91%).…”