Triphenylphosphine complex with halogens

However, if the phenol is first treated with the complex formed from triphenylphosphine and a halogen in acetonitrile solution, an aryloxytriphenylphosphonium halide is formed which on thermal decomposition yields the aryl halide in good yield (e.g. the preparation of p-bromochlorobenzene, Expt 6.30). 

Direct halogenation of sucrose has also been achieved using a combination of DMF—methanesulfonyl chloride (88), sulfuryl chloride—pyridine (89), carbon tetrachloride—triphenylphosphine—pyridine (90), and thionyl chloride—pyridine—1,1,2-trichloroethane (91). Treatment of sucrose with carbon tetrachloride—triphenylphosphine—pyridine at 70°C for 2 h gave 6,6 -dichloro-6,6 -dideoxysucrose in 92% yield. The greater reactivity of the 6 and 6 primary hydroxyl groups has been associated with a bulky halogenating complex formed from triphenylphosphine dihaUde ((CgH )2P=CX2) and pyridine (90). 

The metal-metal bonds in the complexes [M(CO)4(Sime3)]2 are readily attacked by halogens, triphenylphosphine, trimethylsilane, and sodium amalgam. Sodium amalgam produces the anion [M(CO)4(Sime3)] which reacts with main-group or transition-metal halide species to give a series of new complexes,74, 160>161) e.g. 

Bromonaphthalene has been prepared from 2-aminonaphtha-lene by the reaction of mercuric bromide with the diazonaphtha-lene. The reaction described in this preparation appears to be fairly general and provides a useful alternative method for introducing bromine into the aromatic nucleus. Using conditions similar to those outlined, the following have been prepared from the corresponding aryl alcohols a-bromonaphthalene (72%), 3-bromopyridine (76%), 2-bromopyridine (61%), 8-bro-moquinoline (48)%, o-bromotoluene (72%), />-chlorobromo-benzene (90%), -nitrobromobenzene (60%), and />-methoxy-bromobenzene (59%). The use of the triphenylphosphine-halogen complex to convert alcohols to alkylhalides is described elsewhere in this series. ... 

In addition to the sulfonyloxy displacement reaction which may occur on halogenation with triphenyl phosphite complexes, the possibility of acetal migration (with appropriate structure) should not be overlooked. Thus, 1,2 5,6-di-O-isopropylidene-a-D-glucofuranose with triphenyl phosphite dibromide in benzene for 48 hours afforded " (presumably) 6-bromo-6-deoxy-l,2 3,5-di-O-isopropylidene-a-D-glucofiiranose, which was hydrolyzed to 6-bromo-6-deoxy-D-glucose in 10% overall yield. In some compounds, steric factors may prevent the introduction of halogen. With vicinal glycols and triphenyl phosphite methiodide, phosphonic ester formation occurs instead of halide production, but this reaction may be eliminated by use of triphenylphosphine in carbon tetrachloride. 

The reactions of allyliron tricarbonyl halides with donor molecules were studied. Triphenylphosphine substituted only one carbonyl, that trans-oriented with respect to the halogen of the form (XIX) [432). The phosphine derivatives of (XX) were not isolated as pure compounds. The complexes were decomposed entirely by dimethyl sulfoxide, giving [(0113)280] jFeX2 [435). Thermal decomposition of C3H5Fe(CO)3X depended on the medium and gave either diallyl, or diallyl ketone, together with propene, allyl ether, Fe(CO)5, and FeX2 [436). 

Clark and his co-workers have shown that water will provide a convenient source of the hydro ligand in reactions with cationic platinum(II) complexes (Eq. 40). Reaction occurs when L is triethylphosphine or triphenylphosphine 93, 81), when X is a halogen, and also when L is an alkylarsine 80). The mechanism has been studied and is considered to proceed via an intermediate carboxylate 95, 96). 

Recently Blum reported that chlorotris(triphenylphosphine) rhodium (XI) is an active catalyst for the decarbonylation of aroyl halides and showed several examples (2). But in this case too, the real catalyst seems to be chlorocarbonylbis(triphenylphosphine)rhodium (XII), which is formed in situ from XI by the stoichiometric reaction with acyl halides. Formation of alkyl halides by decarbonylation of acyl halides can be carried out by the Hunsdiecker reaction, but the reaction is unsatisfactory when applied to aroyl halides. Therefore, the decarbonylation reaction of aroyl halides by the rhodium complex is a new and useful means of introducing halogen onto the aromatic ring. 

Under remarkably mild conditions aromatic cyanides can be prepared from halogen compounds with alkali metal cyanides in the presence of transition metal complexes. Complexes of palladium and nickel are particularly useful, for instance tetrakis(triphenylphosphine)palladium(0) (6), tris(triphe-nylphosphine)nickel(O) (7) or trun -dichlorobis(triphenylphosphine)nickel(II) (8 Scheme 7). 

---