Rhodium(I) and (III) Complexes of Some Phospholes and Their Behavior as Homogeneous Hydrogenation Catalysts

Abstract

Reactions between rhodium(I11) chloride hydrate and certain phospholes are described; these result in the formation of both Rh(II1) and Rh(1) complexes. The phospholes also react with Rh(1) carbonyl and ethylene complexes. The products of these reactions were investigated as homogeneous catalysts in the hydrogenation of I-hexene, and some show relative rates of hydrogenation comparable with that of hydridocarbonyltris(triphenylphosphine)rhodium(I) but slower than that of tris(triphenylphosphine)rhodium (I) chloride.

Phosphole-based ligands in catalysis

“…The use of a monophosphole ligand in hydrogenation was first reported in 1972 by Hui et al in Rh-catalyzed reactions but very few applications have been subsequently developed. 33 The [RhHCl 2 ( TPP ) 2 ] complex showed its ability to hydrogenate 1-hexene 1b at 20 °C under 1 bar of H 2 in the presence of Et 3 N (Scheme 8). [RhCl( TPP ) 3 ] also catalyzed the same hydrogenation reaction but was found to be less active than [RhCl(PPh 3 ) 3 ] (for the same reaction).…”

Polycyclic carbon-phosphorus heterocycles

“…Some novel chemistry of organophosphorus-metal complexes has been recently investigated (ref 7, 8, 62,106,165,214,215,258,315,360). Some phosphinic acid-metal complexes, of the type 494, have been prepared and studies involving thermochemical properties discussed.214 A subsequent report by the same authors275 presented related complexes of 494 involving chromium as the chelating metal.…”

An Efficient and Selective Monohydrido Rhodium(I) Homogeneous Hydrogenation Catalyst Containing a Cyclic Phosphine

“…Additional The air stable, bright orange complex RhH-olefin can be reduced by introduction of more of (DBP), can be prepared either by reduction of the olefin and readjustment of hydrogen pressure RhCl,(DBP), (3) with NaBH, or by reaction at the end of a run. of the latter with RhCl(CO),(DBP) (3) phosphine catalysts are listed in Table 2 and it can be seen that RhH(DBP), is about 7 times as active as Wilkinson's catalyst, RhCl(PPh,),, under similar conditions. Hydrido-tetrakis (triphenylphosphine)rhodium(I), RhH(PPh,),, is also an efficient catalyst under similar conditions (rate = 1.2 x M s-' for a 0.5 mM catalyst solution, 0.5 M 1-hexene, 60 cm partial pressure of H, at 20") although at a rate -8 times slower than the DBP analog.…”

“…signal at viously noted that rhodium complexes of cyclic r20.6 corresponding to the proton attached to phosphines also catalyze the homogeneous the rhodium atom. Recrystallization of RhHhydrogenation of 1-hexene (3) although, so far, (DBP), from benzenelethano1 results in the loss these systems have not been as effective as the of a ligand and the formation of RhH(DBP), triphenylphosphine analogs. Hydrido complexes which has no detectable band in the 2000 cm-' of rhodium are known to be intermediates in region of the i.r.…”