The monomeric rhenium(ll1) complexes, ReX,(RCN)(PPh,), (R = alkyl; X = CI or Br) have been prepared in high yield by heating trans-ReOX,( PPh,), with triphenylphosphine and an alkanonitrile other monomeric Re(ll1) complexes may be obtained from them by ligand substitution, while aerial oxidation gives ReOCI,( PPh,O) PPh,. The nitrite complexes are oxidised rapidly by halogenated compounds of the type R'CY, (R' = any group; Y = CI or Br) to ReX,Y(PPh,), or ReX2Y,(PPh,),.The properties and structures of the new compounds and the mechanisms of the reactions are discussed.
~YLUZS-~XOTRIHALOGENOBIS(TRIPHENYLPHOSPHIXE)-RHENIUM(V), trans-ReOX,(PPh,), (x = c1 or Br), are readily available and versatile intermediates in preparative rhenium chemistry, and have been used to prepare rhenium compounds in several oxidat ion states.1 By heating tvans-ReOC13(PPli,), with alkanonitriles (RCN) under nitrogen we have now obtained a series of complexes ReCl,(RCN) (PPh,), in 30-35:/6 yield, and we have isolated ReOCl,(PPh,O) (PPh,) from the (aerially osidised) mother-liquors. lilien the reaction was carried out in the presence of additional free triphenylphosphine, the yield of ReCl,( RCN) (PPh3)2 rose to 90"/. The compounds, which are crystalline and easily purified, are thus readily available in SOo/, yield from the metal, and provide the most direct route to rnonomeric complexes of rhenium(rI1). The other such complexes definitely characterised to date are the phosphine complexes ReCI,( PEt,Ph), and KeCl,( PEt,Pli) (diphos) (diphos = Ph2P*CH,-CH2*PPh2),2 salts of the cations ReCl,(diph~s),-,~ ReX,(diar~),~ [diars = o-C,H,(AsMe,),; X = C1, Br, or I],, and Ke(CO)X,(diars), (X = Br or I),* and the p-diketone complexes ReX,(DD') (PPh,), and ReX(DD'),(PPh,) (DD' = $-diketone; S = C1, Br, or I).5 Compounds of stoicheiometry ReCI,(PPh,O), and ReCl,(R*CO,H), of uncertain structure, the complexes ReI,[P(OR'),], (R' = aryl),* Re(CQ-,9 and Re(OH),(CN)2-,l0 and various hyrides are also claimed.By ligand substitution reactions of ReCl,(RCN) (PPh,), we obtained the monomeric complexes ReCl,py,(PPh,) , ReCl,py3, and ReCl,(LL')(PPh,) (py = pyridine; LL' = benzil, 9,10-phenanthraquinone, 2,2'-bipyridyl). The bromo-complexes ReBr,( RCN) (PPh,), could be obtained from tvn~zs-ReOBr,(PPh,), in the same way as the chloro-complexes, but the ethoxo-compound ReOCl,(OEt) (PPh,), was not reduced, and ReCl,(RCh') (PPh,), did not react with alcohols. ReCl,(PhCN) (PPh,), was formed by exchange from benzonitrile and the acetonitrile complex.
