REACTION OF OSHCL(CO)(PIPR(3))(2) WITH CYCLOHEXYLACETYLENE - FORMATION OF A HYDRIDO-VINYLIDENE COMPLEX VIA A 1,3-HYDROGEN SHIFT

The complex OsHCl(CO)(PiPr(3))(2) (1) reacts with cyclohexylacetylene to give OsHCl(=C=CHCy)(CO)(PiPr(3))(2) (2), which evolves in solution to OsCl((E)CH=CHCy)(CO)(PiPr(3))2 (3). Complex 3 reacts with HCl to afford OsCl2(=CHCH(2)Cy)(CO)(PiPr(3))(2) (4). The reaction of OsDCl(CO)(PiPr(3))(2) (1-d) with cyclohexylacetylene leads to a mixture of OsDCl(=C=CHCy)(CO)(PiPr(3))(2) (2-d(a)) and OsHCl(=C=CDCy)(CO)(PiPr(3))(2) (2-d(b)) in a ca. 1:1 molar ratio, indicating that the formation of 2 involves a 1,3-hydrogen shift via an alkynyl intermediate. The dihydrogen, or dihydride nature of this alkynyl intermediate is discussed.