Abstract
The preparation and reactivity of some Ir-Zn and Ir-Cd heterometallic hydride complexes are described. Treatment of [Ir(IPr)(2)H(2)][BAr(F)(4)] (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; Ar(F) = 3,5-C(6)H(3)(CF(3))(2)) with M'R(2) (M' = Zn; R = Ph, Me, Et; M' = Cd, R = Me) and Me(3)SiCH=CH(2) results in dehydrogenation of an IPr isopropyl substituent, along with R-H elimination, to form square-pyramidal [Ir(IPr)(IPr″)(M'R)H][BAr(F)(4)] (M'R = ZnPh (4a); ZnMe (4b); ZnEt (4c); CdMe (8); IPr″ = dehydrogenated IPr) featuring apical M'R ligands. Heating 1 with 2 equiv ZnPh(2) under H(2) forms [Ir(IPr)(2)(ZnPh)(2)H(4)][BAr(F)(4)] (5) featuring trans ZnPh ligands. Exposure of 4b-c and 8 to H(2) yields [Ir(IPr)(IPr″)(M'R)H(3)][BAr(F)(4)] (9b-c, 10) as intermediates to highly fluxional [Ir(IPr)(2)(M'R)(η(2)-H(2))H(3)][BAr(F)(4)] (11b-c, 12). Reacting 11b-c with Lewis bases (L) effects [ZnR](+) abstraction to give pentahydride Ir(IPr)(2)H(5) (13); with 11c and L = IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), [L(2)ZnEt][BAr(F)(4)] was characterized, whereas with L = PMe(3), both 13 and [Ir(IPr)(2)(ZnEt)(PMe(3))H(3)][BAr(F)(4)] (14c) were formed. Reactions of 13 with M'R(2) similarly proceed with R-H elimination to form Ir(IPr)(2)(M'R)H(4) (15a-c, 16). Crystallographic and computational analyses characterize a range of hydride ligands, the nature of which depends subtly on the surrounding coordination environment. The new polyhydride complexes reported here add to the small number of such species featuring N-heterocyclic carbene ligands.