Rhodium triphenylphosphine oxide

Mitsubishi Kasei introduced a process to manufacture isononyl alcohol, an important PVC (polyvinyl chloride) plasticizer, via the hydroformylation of octenes (a mixture of isomers produced by dimerization of the C4 cut of naphtha cracker or FCC processes).95 First a nonmodified rhodium complex exhibiting high activity and selectivity in the formation of the branched aldehyde is used. After the oxo reaction, before separation of the catalyst, triphenylphosphine is added to the reaction mixture and the recovered rhodium-triphenylphosphine is oxidized under controlled conditions. The resulting rhodium-triphenylphosphine oxide with an activity and selectivity similar to those of the original complex, is recycled and used again to produce isononanal. 

In 1987 Mitsubishi Kasei launched a 30000 tons/year plant for the production of isononanol by hydroformylation of octenes [37]. The catalyst is based on a rhodium-triphenylphosphine oxide (TPPO) complex which is stabilized after the 0x0 reaction by addition of triphenylphosphine (TPP) to avoid decomposition during the distillation of product. The rhodium-(TPP)complex formed together with excess of TPPO in the high-boiling residue is oxidized to the rhodium-TPPO... 

Rhodium(III) chloride trihydrate (2 g.) is dissolved in 70 ml. of ethanol (95%) in a 500-ml. round-bottomed flask fitted with gas inlet tube, reflux condenser, and gas exit bubbler. A solution of 12 g. of triphenylphosphine (freshly crystallized from ethanol to remove triphenylphosphine oxide) in 350 ml. of hot ethanol is added and the flask purged with nitrogen. The solution is refluxed for about 2 hours, and the crystalline product which forms is collected from the hot solution on a Buchner funnel or sintered-glass filter. The product is washed with small portions of 50 ml. of anhydrous ether yield 6.25 g. (88% based on Rh). This crystalline product is deep red in color. 

Mitsubishi has patented a triphenylphosphine oxide-modified rhodium catalyst for the hydroformylation of higher alkenes with both alkyl branches and internal bonds. [19] Reaction conditions are 50-300 kg/cm2 of CO/H2 and 100-150 degrees C. The high CO/H2 partial pressures provide stabilization for rhodium in the reactor, but rhodium stability in the vaporizer separation system is a different matter. Mitsubishi adds triphenylphosphine to stabilize rhodium in the vaporizer. After separation, triphenylphosphine is converted to its oxide before the catalyst is returned to the reactor. 

In the spectra of the various solutions containing excess triphenylphosphine, the expected singlet signal at 7.2 ppm appeared. Also present in all of the solutions was a sharp singlet signal at +22.1 ppm, due to triphenylphosphine oxide, which always was formed due to oxidation by the traces of molecular oxygen present. The present rhodium complex system is a very effective catalyst for such oxidations. 

The well-known rhodium (136) and iridium 137) peroxo complexes (PhgPlaRhCKOa) (40), [(PhgPlaRhCKOalJa (41), and (Ph3P)2(C0)IrCl(02) (42) have been investigated for their reactivity with acetylacetone, acacH 138). Only the former complex, 40, exhibited any reactivity (in the presence of two equivalents of triphenylphosphine), yielding the hydroperoxo complex (43), (see Scheme 8). Complex 43 reacts with PPhg to form triphenylphosphine oxide, but does not react with any active methylene compounds (methyl acetoacetate, diethyl malonate, or acetone) save for cyclopentadiene. In the last instance, a poorly characterized, unstable system tentatively formulated as 44 may have been formed. In refluxing benzene, 43 did react with excess acacH to form the bis(acac) complex 45. 

Form Supplied in burgundy-red powder, possibly containing excess triphenylphosphine, triphenylphosphine oxide, and traces of rhodium(II) and -(III) complexes. 

Rhodium complexes are also active catalysts for phosphine oxidation. For example, Poddar and Agarwal [120] report that when air was bubbled through a solution of [Rh(PPh3)301] (0.05 g) and triphenylphosphine (0.50 g) in refluxing toluene for 4 hr, a quantitative yield of triphenylphosphine oxide was obtained. Blank experiments carried out in the absence of the rhodium complex gave negative results. 

The rhodium (triphenylphosphine)(ethene) complex CpRh(PPh3)(C2H4) 349, was synthesized by the reaction of [RhCl(G2H4)2]2 with triphenylphosphine and thallium cyclopentadienide. As in CpRh(PMe3)(C2H4), the coordinated ethene ligand may be displaced photochemically, affording a series of oxidative addition reactions.Complexes of the type Cp Rh(olefin)2 are found to be excellent catalysts for the isomerization of aldehydes or transfer formylation reactions." Divinyl disiloxane or divinyl disilazane afforded the preparation of several complexes of Rh-Cp, such as 350, 351, and 352. ... 

The avermectins also possess a number of aUyflc positions that are susceptible to oxidative modification. In particular the 8a-methylene group, which is both aUyflc and alpha to an ether oxygen, is susceptible to radical oxidation. The primary product is the 8a-hydroperoxide, which has been isolated occasionally as an impurity of an avermectin B reaction (such as the catalytic hydrogenation of avermectin B with Wilkinson s rhodium chloride-triphenylphosphine catalyst to obtain ivermectin). An 8a-hydroxy derivative can also be detected occasionally as a metaboUte (42) or as an impurity arising presumably by air oxidation. An 8a-oxo-derivative can be obtained by oxidizing 5-0-protected avermectins with pyridinium dichromate (43). This also can arise by treating the 8a-hydroperoxide with base. 

The use of a catalyst such as cadmium oxide increases the yield of dibasic acids to about 51% of theoretical. The composition of the mixed acids is about 75% C-11 and 25% C-12 dibasic acids (73). Reaction of undecylenic acid with carbon monoxide using a triphenylphosphine—rhodium complex as catalyst gives 11-formylundecanoic acid, which, upon reaction with oxygen in the presence of Co(II) salts, gives 1,12-dodecanedioic acid in 70% yield (74). 

A 500-ml rcund-bottom flask is equipped with a reflux condenser, a gas inlet tube, and a gas outlet leading to a bubbler. The flask is charged with a solution of rhodium (III) chloride trihydrate (2 g) in 70 ml of 95 % ethanol. A solution of triphenylphosphine (12 g, freshly recrystallized from ethanol to remove the oxide) in 350 ml of hot ethanol is added to the flask, and the system is flushed with nitrogen. The mixture is refluxed for 2 hours, following which the hot solution is filtered by suction to obtain the product. The crystalline residue is washed with several small portions of anhydrous ether (50 ml total) affording the deep red crystalline product in about 85% yield. 

This burgundy-red compound can be easily prepared by reacting RhCl3-3H20 with triphenylphosphine in refluxing ethanol. In this reaction, rhodium(III) is reduced to the rhodium(I) complex RhCl(PPh3)3, whilst the phosphine is oxidized to phosphine oxide according to Eq. (3). 

---