Synthesis and reactivity of [OsH{C6H4(CH=CHH)}(CO)(PPr3i)(2)] and the formato compounds [Os{(E)-CH=CHPh}(eta(2)-O2CH)(CO)(PPr3i)(2)] and [OsH(eta(2)-O2CH)(CO)(PPr3i)(2)]

The complex [OsH{C6H4(CH=CHH)}(CO)(PPr3i)(2)] has been prepared by reaction of the five-co-ordinate [Os{(E)-CH=CHPh}Cl(CO)(PPr3i)(2)] with LiBu(n) in hexane. It reacts with P(OMe)(3) and CO to give [OsH{(E)-CH=CHPh}(CO){P(OMe)(3)}(PPr3i)(2)] and [OsH{(E)-CH=CHPh}(CO)(2)(PPr3i)(2)], while under a CO2 atmosphere the formato derivative [Os{(E)-CH=CHPh}(eta(2)-O2CH)(CO)(PPr3i)(2)] is obtained. Carbonylation of the latter leads to the monodentate formato complex [Os{(E)-CH=CHPh}{eta(1)-OC(O)H}(CO)(2)(PPr3i)(2)] and under a hydrogen atmosphere it affords styrene and [OsH(eta(2)-O2CH)(CO)(PPr3i)(2)], which can be also prepared by reaction of [OsH2(eta(2)-CH2=CHEt)(CO)(PPr3i)(2)] with CO2. The complex [OsH(eta(2)-O2CH)(CO)(PPr3i)(2)] reacts with CO, P(OMe)(3) and MeO(3)CC=CCO(2)Me to give [OsH{eta(1)-OC(O)H}(CO)L(PPr3i)(2)][L = CO, P(OMe), or MeO(2)CC=CCO(2)Me]; the carbon atom of its formate ligand is attacked by NEt(2)H leading to the carbamato compound [OsH(eta(2)-O(2)CNEt(2))(CO)(PPr3i)(2)] and molecular hydrogen. Similarly treatment of [Os{(E)-CH=CHPh}(eta(2)-O2CH)(CO)(PPr3i)(2)] with NEt(2)H afforded [Os{(E)-CH=CHPh}(eta(2)-O(2)CNEt(2))(CO)(PPr3i)(2)]. The former complex also reacts with HBF4 . OEt(2), giving two different,derivatives depending upon the conditions: in diethyl ether as solvent and in the presence of acetonitrile the vinyl complex [Os{(E). CH=CHPh}(CO)(MeCN)(2)-(PPr3i)(2)]BF4 is formed, while the carbene derivative [Os(eta(2)-O2CH)(=CHCH(2)Ph)(CO)(PPr3i)(2)]BF4 is obtained in chloroform. The products formed by reaction of [OsH(eta(2)-O2CH)(CO)(PPr3i)(2)] with HBF4 . OEt(2) also depend upon the reaction conditions: in diethyl ether and in the presence of MeCN the hydride compound [OsH(CO)-(MeCN)(2)(PPr3i)(2)]BF4 is obtained; however a mixture of products, mainly dihydrogen derivatives, is formed in CDCl3. On the basis of theoretical calculations and T-1 measurements, the nature and structure of these dihydrogen compounds are discussed.