Catalysis by Phosphines

Under catalysis by phosphines (e. g., triphenylphosphine), alkynones can be isomerized into dienones [50] (eq. (23)). 

Matsumoto H, Nakano T, Nagai Y et al (1978) Catalysis by phosphine complexes of silylruthenium hydrides of the addition of carbon tetrachloride to 1-octene. Bull Chem Soc Jap 51(8) 2445-2446... 

The early development of aromatic phosphine chemistry took place during the last quarter of the nineteenth century mainly in Michaelis s school.He prepared dichloro(phenyl)phosphine by the passage of the mixed vapours of benzene and phosphorus trichloride through a red hot porcelain tube. This was quickly followed by the preparation of phenylphosphine, dialkylphenylphosphines, and triphenylphosphine. This latter phosphine was destined some 75 years later to become one of the most important phosphines in the development of homogeneous catalysis by phosphine metal complexes. Michaelis obtained it by the reaction of sodium with dichloro(phenyl)phosphine or phosphorus trichloride and bromobenzene in boiling ether.The development of aromatic phosphorus chemistry rapidly overtook that of their intractable aliphatic analogs. It was well established by the 1920s whereas the aliphatic had to await the... 

On the other hand, the halohydrin (chloro and bromo) 908 is converted into a ketone via oxidative addition and //-elimination in boiling benzene with catalysis by Pd(OAc)2 and tri(o-tolyl)phosphine in the presence of K2C03[765,766],... 

This H-transfer reduction with sodium formate and employing catalysis by a water-soluble rhodium-phosphine catalyst yields dimethyl methylsuccinate [117]. 

Miscellaneous Reactions of Phosphines.- The role of chiral phosphines as ligands in the catalysis of reactions leading to the formation of chiral products has been reviewed.1111 A procedure for the determination of the enantiomeric excess in chiral phosphines has been developed, based on 13C n.m.r. studies of the diastereoisomeric complexes formed by phosphines with the chiral pinenyl nickel bromide complex. 111 Studies of the sulphonation of triphenylphosphine and of chiral arylphosphines have been reported in attempts to prepare water soluble ligands which aid... 

Platinum(O) phosphine complexes undergo a variety of oxidative addition reactions with compounds containing Group 14 elements. These reactions are of widespread interest because similar processes are probably involved in the catalysis by platinum complexes of reactions such as the hydrosilation of alkenes and the disilylation of dienes and alkenes. 

The need for higher product specificity and milder reaction conditions (see also Section IX) has led to extensive research in hydroformylation technology. This research, as reported in technical journals, patent literature, and commercial practice has been primarily concerned with catalysis by rhodium, in addition to the traditional cobalt, and with catalyst modification by trialkyl or triaryl phosphines. These catalyst systems form the basis for the major portion of the discussion in this chapter some other catalyst systems are discussed in Section VIII. 

Some general reviews on hydrogenation using transition metal complexes that have appeared within the last five years are listed (4-7), as well as general reviews on asymmetric hydrogenation (8-10) and some dealing specifically with chiral rhodium-phosphine catalysts (11-13). The topic of catalysis by supported transition metal complexes has also been well reviewed (6, 14-29), and reviews on molecular metal cluster systems, that include aspects of catalytic hydrogenations, have appeared (30-34). 

Electron spin resonance (ESR) signals, detected from phosphinated polystyrene-supported cationic rhodium catalysts both before and after use (for olefinic and ketonic substrates), have been attributed to the presence of rhodium(II) species (348). The extent of catalysis by such species generally is uncertain, although the activity of one system involving RhCls /phosphinated polystyrene has been attributed to rho-dium(II) (349). Rhodium(II) phosphine complexes have been stabilized by steric effects (350), which could pertain to the polymer alternatively (351), disproportionation of rhodium(I) could lead to rhodium(II) [Eq. (61)]. The accompanying isolated metal atoms in this case offer a potential source of ESR signals as well as the catalysis. 

Asymmetric catalysis by chiral rhodium complexes in both hydrogenation and hydrosilation have been found. Kagan (42) recently reported that the chiral phosphine rhodium complex [(—)-DIOPRhCl]2 gave the most efficient asymmetric syntheses observed to date. This complex is ... 

The wide apphcation of NHCs to catalysis places them along with phosphines and cyclopentadienyls in their utility for organometaUic catalysis. Being much more donor in nature than phosphines, the NHCs occupy a distinct region of the Tolman ligand map [32]. A number of pincer NHC derivatives are catalyticaUy active, but are not discussed here because they have been fully described elsewhere [33]. Some other important recent reviews discuss catalysis by NHC complexes in general [10, 34, 35]. 

We discussed this catalysis recently (141st National Meeting of the American Chemical Society, March 1962) in terms of an olefin insertion reaction involving a Pt(II) olefin complex (3). We found that catalysis was only accomplished by platinum compounds capable of coordinating olefins. For example, substitution by tertiary phosphines blocks coordination by olefins and greatly reduces the catalytic activity of Pt(II). The substitution by phosphines does not affect the ability of the complexes to cleave the Si—H bond, however. The hindering of a catalytic reaction by blocking coordination sites is a common occurrence and is, I think, a persuasive... 

Hydrides of Ni(I) and Ni(II) are known (37). A Ni(II) hydride appears to be an intermediate in the catalysis of olefin isomerization by phosphine complexes of nickel (61). Dilworth (62) has pointed out that stable hydride species are not obtained in model complexes with sulfur ligands. However, they may be possible within the confines of a protein chelate. 

The effects of added triphenylphosphine and changing temperature on ligand dissociation and equilibria were studied also. The above dimer was an active hydrogenation catalyst. The equilibrium concentration of the dimer and the rate of olefin hydrogenation catalysis by the system depend inversely on the concentration of excess phosphine ligand. 

Under catalysis by a Pd complex with homochiral phosphine ligand 19, silaboration of terminal allenes with homochiral silylborane 18 shows high enantioface-selectivity by double asymmetric induction (Equation (25)).lls The resultant /3-borylated allylsilanes can be used for asymmetric carbonyl allylation. 

---