Reactivity and chemical exchange processes of bis(ether-phosphine) iridium(III) complexes

Article abstract of DOI:10.1016/S0020-1693(97)05769-1

The orthometalated iridium(III) complex ClIrH(P OCH₂) (P O) (P OCH₂=η² (P,OCH₂) coordination of Cy₂PCH₂CH₂OCH₂, P O =η²(P,O) coordination of Cy₂PCH₂CH₂OCH₃) (1) reacts with CS₂, HCl, and H₂ under re-formation of the methoxy group to give ClIr(η²-CS₂)(P～O)₂ (3) (P～O=η¹(P) coordination of Cy₂PCH₂CH₂OCH₃), trans-( P O )(P～O)Ir(H)Cl₂ (4a) and ClIrH₂( P O )(P～O) (5), respectively. Upon the reaction of 1 with CO the orthometalation is maintained to yield the carbonyl adduct ClIrH(CO)(P OCH₂)(P～O) (2). Compounds 4a and 5 represent potentially unsaturated species weakly protected by the ether moiety which acts as an intramolecular solvent. The chelated five-membered ring in 4a, cis-( P O ) (P～O)Ir(H)Cl₂ (4b) and 5 can easily be cleaved by carbon monoxide, pyridine and CS₂ whereby the complexes Cl₂IrH(CO)(P～O)₂ (7), ClIrH₂(C₅H₅N)(P～O)₂ (10), ClIrH₂(CO) (P～O)₂ (11) and the dithioformato complex cis-(P～O)₂Ir(H)Cl(S₂CH) (13a) are formed. In toluene 13a isomerizes to give the trans-product 13b. Comparative NMR studies on the fluxional behavior of the ether phosphine ligands of the five monochelated complexes 4a,b, 5, IrH₃(P～O)₂(6) and Cl₃Ir( P O ) (P～O) (9a) were performed to determine the dependence of the exchange rates on the strength of the iridium-(ether) oxygen bond. Complex 9b, the phenyl congener of 9a, crystallizes in the orthorhombic space group Pna2₁ with Z=4. The cell dimensions arc a= 1695.2(3), b= 1093.4(2), c= 1621.5(9) pm, R₁=0.018 and wR₂=0.042.