Relative dioxygenation rates of some trans-Ir(CO)X(PR3)2 complexes: The effect of phosphine and halogen changes

Platinum group metal complexes of arylphosphine ligands containing perfluoroalkyl ponytails; crystal structures of [RhCl2(η5-C5Me5){P(C6H4C6F13-4)3}] and cis- and trans-[PtCl2{P(C6H4C6F13-4)3}2]

“…8) indicate a sequential drop in the rate of oxidation with the stepwise introduction of pairs of ponytails. The half-lives are calculated to be PPh 3 62 min (which is comparable to that observed previously 45 solely to the electronic influence of the perfluoroalkyl substituents. However, the spectroscopic and structural data (see above) suggest that the introduction of the ponytails in these aryl ligands has a limited effect; the IR data for [IrCl(CO)(O 2 ){P(C 6 H 4 -C 6 F 13 -4) 3 } 2 ] [(ν(CO) 2025 and ν(O-O) 861 cm Ϫ1 )] are very similar to those for the PPh 3 complex (2015 and 858 cm Ϫ1 respectively).…”

“…Here, we have, initially, chosen to use the well established rate of O 2 addition to the [IrCl(CO)L 2 ] 7-9 complexes as a probe. 45 For comparison purposes we have also investigated the rates for the analogous PPh 3 and P(C 6 H 4 CF 3 -4) 3 10 complexes under the same conditions. In these studies we have examined the variation in substrate/ product concentrations using IR spectroscopy in the carbonyl stretching region and have chosen chloroform as the solvent.…”

Transition-metal fluoro compounds containing carbonyl, phosphine, arsine, and stibine ligands

“…The carbonyl stretching frequencies of MX(CO)-(PPh^i n various solvents are found to follow the order X = F < Cl < Br < I (Table XII) with increasing tr-acceptor strength of the halides along this series.64 These IR data have been used to explain the observed trend in halide affinity for [Rh(CO)-(PPh3)2]+, with fluoride most preferred, on the basis of minimizing competition between the halide and the trans carbon monoxide for electron density in the filled rhodium dT orbitals (Figure l). 19 Analogous trends in i»co with variation of X are observed for RhX(CO)L2, (L -AsPh3, SbPh3)76 and IrX(CO)(PEtPh2)2.74 However, vqo values do not follow a readily interpretable pattern with variation of L. 74 This indicates that carbonyl stretching frequencies are not necessarily a simple measure of the <r-donor or ir-acceptor capabilities of ligands attached to the metal in the MX(CO)L2 system.…”

Influence of Ligand Polarizability on the Reversible Binding of O2bytrans-[Rh(X)(XNC)(PPh3)2] (X = Cl, Br, SC6F5, C2Ph; XNC = Xylyl Isocyanide). Structures and a Kinetic Study

“…A stable O 2 adduct is also found for X = CN indicating that an appropriate position for the CN ion in the above sequence is to the right of Br (i.e., Cl < Br < CN). The sequence of anionic ligands given above clearly reflects variations in an electronic property of the ligands X but does not match the ordering (taken in either direction) of the spectrochemical (Br < Cl < NCO < CN) or nephelauxetic (CN ∼ Cl < Br) series; neither is there agreement with the ordering of ν co for the complexes trans -[Rh(X)(CO)(PPh 3 ) 2 ] (C 2 Ph < Cl, Br < SC 6 F 5 ) − where a low wavenumber is generally taken to indicate the presence of a good σ donor and/or poor π acceptor (but see also ref ). The ordering of the anionic ligands derived from the data in Figure can, however, be readily accounted for qualitatively in terms of their relative polarizability.…”