The neutral Rh(I)–Xantphos complex [Rh(κ3-P,O,P-Xantphos)Cl] n , 4, and cationic Rh(III) [Rh(κ3-P,O,P-Xantphos)(H)2][BArF 4], 2a, and [Rh(κ3-P,O,P-Xantphos-3,5-C6H3(CF3)2)(H)2][BArF 4], 2b, are described [ArF = 3,5-(CF3)2C6H3; Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; Xantphos-3,5-C6H3(CF3)2 = 9,9-dimethylxanthene-4,5-bis(bis(3,5-bis(trifluoromethyl)phenyl)phosphine]. A solid-state structure of 2b isolated from C6H5Cl solution shows a κ1-chlorobenzene adduct, [Rh(κ3-P,O,P-Xantphos-3,5-C6H3(CF3)2)(H)2(κ1-ClC6H5)][BArF 4], 3. Addition of H2 to 4 affords, crystallographically characterized, [Rh(κ3-P,O,P-Xantphos)(H)2Cl], 5. Addition of diphenyl acetylene to 2a results in the formation of the C–H activated metallacyclopentadiene [Rh(κ3-P,O,P-Xantphos)(ClCH2Cl)(σ,σ-(C6H4)C(H)CPh)][BArF 4], 7, a rare example of a crystallographically characterized Rh–dichloromethane complex, alongside the Rh(I) complex mer-[Rh(κ3-P,O,P-Xantphos)(η2-PhCCPh)][BArF 4], 6. Halide abstraction from [Rh(κ3-P,O,P-Xantphos)Cl] n in the presence of diphenylacetylene affords 6 as the only product, which in the solid state shows that the alkyne binds perpendicular to the κ3-POP Xantphos ligand plane. This complex acts as a latent source of the [Rh(κ3-P,O,P-Xantphos)]+ fragment and facilitates ortho-directed C–S activation in a number of 2-arylsulfides to give mer-[Rh(κ3-P,O,P-Xantphos)(σ,κ1-Ar)(SMe)][BArF 4] (Ar = C6H4COMe, 8; C6H4(CO)OMe, 9; C6H4NO2, 10; C6H4CNCH2CH2O, 11; C6H4C5H4N, 12). Similar C–S bond cleavage is observed with allyl sulfide, to give fac-[Rh(κ3-P,O,P-Xantphos)(η3-C3H5)(SPh)][BArF 4], 13. These products of C–S activation have been crystallographically characterized. For 8 in situ monitoring of the reaction by NMR spectroscopy reveals the initial formation of fac-κ3-8, which then proceeds to isomerize to the mer-isomer. With the para-ketone aryl sulfide, 4-SMeC 6H4COMe, C–H activation ortho to the ketone occurs to give mer-[Rh(κ3-P,O,P-Xantphos)(σ,κ1-4-(COMe)C6H3SMe)(H)][BArF 4], 14. The temporal evolution of carbothiolation catalysis using mer-κ3-8, and phenyl acetylene and 2-(methylthio)acetophenone substrates shows initial fast catalysis and then a considerably slower evolution of the product. We suggest that the initially formed fac-isomer of the C–S activation product is considerably more active than the mer-isomer (i.e., mer-8), the latter of which is formed rapidly by isomerization, and this accounts for the observed difference in rates. A likely mechanism is proposed based upon these data.
Key indicatorsSingle-crystal X-ray study T = 293 K Mean (C-C) = 0.004 Å R factor = 0.039 wR factor = 0.108 Data-to-parameter ratio = 8.4For details of how these key indicators were automatically derived from the article, see
I n this paper complexes D (Figure 2), 1a,b (Scheme 2), fac-8, and associated derived structures (Schemes 6 and 10), and 13 (Scheme 8) were drawn incorrectly, showing the wrong isomer for the fac-Xantphos ligand. The incorrect and correct isomers are shown in Scheme 1. This change in no way leads to different conclusions for the work presented or any other discussion of the data. The authors apologize for this mistake and any confusion caused and thank Dr. James Morris (University of East Anglia, U.K.) for bringing it to our attention.
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