Selective deprotonation and decarbonylation from hydridocarbonyl-iridium(III) compounds with trimethylamine N-oxide

Me3NO selectively abstracts the proton from [IrH(CO)(PPh3)(2)L(A)](0,1+,2+) (1) (A: -CCPh, Cl-, CH3CN and L: CH3CN, Cl-, ClO4-) to give the trans-elim ination products, Ir(CO)(PPh3)(2)(A) (2). The reductive elimination of H+ a nd Cl- from Ir(H)Cl-2(CO)(PPh3)(2) (1b) to give IrCl(CO)(PPh3)(2) (2b) is f irst order in both 1b and Me3NO. The rate law d[2b]/dt=k(obs)[1b]=k(2)[1b][ Me3NO] suggests the formation of (PPh3)(2)(Cl)(2)(CO)Ir-H-ON+Me3 in the rat e determining step (k(2)) followed by the fast dissociation of both H-ON+Me 3 and the trans ligand Cl-. The rate significantly varies with the cis liga nd A and the trans ligand L and is slower with both A and L being Cl- than other ligands. Me3NO selectively eliminates CO from [Ir(H)(2)(CO)(PPh3)(2)L ](0,+) (3) (L=CH3CN, ClO4-) to produce [Ir(H)(2)(PPh3)(2)L'(CH3CN)](+) (4) (L'=CH3CN, PPh3) in the presence of L. Me3NO does not readily remove either H+ or CO from cis, trans- and trans, trans-Ir(H)(-CCPh)(2)(CO)(PPh3)(2) an d cis, trans-Ir(H)(2)Cl(CO)(PPh3)(2). The choice whether hydridocarbonyls, 1 and 3 undergo the deprotonation or decarbonylation may be understood most ly in terms of thermodynamic stability of the products and partly by kineti c preference of Me3NO on proton and CO.