Cyclopentadienyl-ruthenium and -osmium complexes: VI. Formation and properties of dihydrido-(η-cyclopentadienyl)bis(triphenylphosphine)osmium(IV) cation. Reaction of hydrido(η-cyclopentadienyl)bis(triphenylphosphine)osmium(II) and dihydrido(η-cyclopentadienyl)bis(triphenylphosphine)osmium(IV) halogenates with HX acids, X 2 dihalogeno and halogenated hydrocarbons

Abstract

Several new compounds of the type [CpOsH 2(PPh 3) 2] + X −, where X = Cl, Br, I, I 3, BPh 4, p-toluenesulphonate, d(+)-campho-10-sulphonate, have been obtained in the form of ion pairs or salts. The above compounds form during oxidative addition by HX acids to CpOsH(PPh) 3) 2. The reactions are complete after several seconds, with a quantitative yield. This is in contrast to the behaviour of CpRuH(PPh 3) 2, where covalent CpRuX(PPh 3) 2 forms. Reactions of CpOsH(PPh 3) 2 with DCl acid (excess) gives [CpOsD 2(PPh 3) 2]Cl, but no [CpOsHD(PPh 3) 2]Cl is formed. Refluxing CpOsBr(PPh 3) 2, in ethylene glycol for instance, gives a [CpOsH 2(PPh 3) 2] + cation as a result of the dehydrogenation of the glycol. Compounds of the type, [CpOsH 2(PPh 3) 2]X, in solutions of polar solvents (MeOH) or halogenated hydrocarbons (e.g. CH 2X 2) undergo transformation to CpOsX(PPh 3) 2 during the reductive elimination process. In this way novel CpOsI(PPh 3) 2 has been obtained. In the case of the reaction of a mixture of HX + X 2 with CpOsH(PPh 3) 2, [CpOsHBr(PPh 3) 2]Br 3 (for Br 2) and [CpOsH 2(PPh 3) 2]I 3 (for I 2) have been obtained in the form of sparingly soluble ion pairs with yields of about 90%.