Reactivity of the heterobinuclear phenylacetylide-bridged A-frame [RhIr(CO)(2)(mu-CCPh)(Ph2PCH2PPh2)(2)][O3SCF3] with small molecules

摘要

The compound [RhIr(CO)(2)(mu-CCPh)(dppm)(2)][O3SCF3] (2, dppm = Ph2PCH2PPh2) is an "A-frame" species in which the bridging phenylacetylide group is sigma-bound to iridium and functioning as a pi donor to rhodium. Compound 2 reacts with CO and SO2 to give the carbonyl-and sulfur dioxide-bridged products [RhIr(CO)(2)(mu-CCPh)(mu-L)(dppm)(2)][O3SCF3] (L = CO (1), SO2 (5)), respectively. Reaction of 2 with a hydride source yields [RbIr(H)(CO)(2)(mu-CCPh)(dppm)(2)] (6), having the hydride terminally bound to iridium, and this product rearranges at room temperature to give the phenylvinylidene complex [RhIr(CO)(2)(mu-CC(H)Ph)(dppm)(2)] (7). Phosphines, olefins, and alkynes also bind terminally to iridium, yielding [RhIr(L)(CO)(2)(mu-CCPh)(dppm)(2)][O3SCF3] (L = PR3, olefin, alkyne). In the case of dimethyl acetylenedicarboxylate, rearrangement of the initial alkyne adduct occurs to give the alkyne-bridged product [RhIr(CO)(2)(mu-CCPh)(mu-CH3O2CC=CCO2CH3)(dppm)(2)][O3SCF3] (18). In addition, the initial adducts of terminal alkynes also rearrange by an oxidative addition reaction to give the bis(acetylide) hydride species [RhIr(CCPh)(CO)(2)(mu-H)(mu-CCR)(dppm)(2)][O3SCF3] (R = Ph (19), CH3 (20)). Compound 2 also undergoes oxidative addition with dihydrogen to give [RhIr(H)(Co)(2)(mu-H)(mu-CCPh)(dppm)(2)][O3SCF3] (21), in which the terminal (on Ir) and the bridging hydrides are in the A-frame pocket. It appears that SO2 and H-2 attack on the inside of the A-frame pocket, whereas all other substrates attack on the outside of the pocket, at iridium. [References: 75]