Ligand effects upon deuterium exchange in arenes mediated by [Ir(PR₃)₂(cod)]⁺.BF₄⁻

Abstract

SummaryA series of complexes of general form [Ir(PR 3 ) 2 (cod)] + has been prepared and used, without isolation, to mediate deuteration of a range of model substrates. The data suggest that, with many substrates, basicity of the phosphine ligands bound to iridium is an important factor influencing substrate selectivity and the efficiency of deuteration. In addition, the spectrum of activity of iridium complexes bearing pure donor ligands is different in many cases to that of complexes where the ligands are known to be p-acids.

An improved bidentate complex of iridium as a catalyst for hydrogen isotope exchange

“…We have already demonstrated that the effect of the phosphine cone angle in 2 and its analogues is small so that, in this series, the principal effect of changing the nature of the arsine ligand should be electronic. 11 However, exchange into phenylacetone in the presence of complexes 3 was not improved by modifying the ligands, systems other than 3a mediating no more than 25% of the theoretical maximum level of exchange.…”

“…Electronic effects will also be different to those observed in complexes of simple phosphines; the distortion caused by chelate formation increases the basicity of the metal centre, 10 this effect increasing as the size of the chelate ring decreases. Since iridium complexes of the most basic phosphines are of limited value, 11 it was expected that the best results would be obtained using complexes with bis(phosphines) of moderate basicity. Indeed, the results presented in Table 1 are broadly in line with this expectation.…”

Catalyst stability as a factor in iridium‐mediated ortho‐deuteration

“…Early catalyst inactivation would explain the poor correlation between ligand properties and the level of isotopic exchange for substrates whose binding kinetics are unfavourable or where initial exchange is slow. 7 …”

The effect of adding Crabtree's catalyst to rhodium black in direct hydrogen isotope exchange reactions

“…The same deuteration pattern has earlier been reported using rhodium(III) hydride complexes but with lower level of deuterium incorporation (9%) in the pyridine ring. 11 Ellames et al 12 has investigated the use of iridium based catalysts of the general form [Ir(PR 3 ) 2 (COD)]…”