Cationic and Neutral Heterometallic Ir-Group 12 Element Polyhydride Compounds: Synthesis, Structure and Reactivity

High Resolution Image Download MS PowerPoint Slide 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.