Rhodium‐103 NMR of [Rh(X)(PPh 3 ) 3 ] [X = Cl, N 3 , NCO, NCS, N(CN) 2 , NCBPh 3 , CNBPh 3 , CN] and derivatives containing CO, isocyanide, pyridine, H 2 and O 2 . Ligand, solvent and temperature effects

Rhodium‐103 chemical shifts are reported for 62 compounds, namely [Rh(X)(PPh 3 ) 3 ] [X = Cl, N 3 , NCO, NCS, N(CN) 2 , NCBPh 3 , CNBPh 3 , CN] and derivatives formed by replacement of a phosphine by CO, xylyl isocyanide (XNC) and pyridine and/or by oxidative addition of H 2 or O 2 to give trans ‐[Rh(X)(PPh 3 ) 2 (CO)] (δ in the range −816 to −368 ppm) trans ‐[Rh(X)(PPh 3 ) 2 (XNC)] (δ −817 to −250 ppm), cis ‐[Rh(X)(PPh 3 ) 2 (py)] (the trans isomer is formed with X = CN, CNBPh 3 ) (δ −233 to 170 ppm), [Rh(X)(H) 2 (PPh 3 ) 3 ] (δ −611 to 119), trans ‐[Rh(X)(H) 2 (PPh 3 ) 2 (py)] (δ −30 to 566 ppm), [Rh(X)(O 2 )(PPh 3 ) 3 ] (δ 1393 to 3273 ppm) and cis ‐[Rh(X)(O 2 )(PPh 3 ) 2 (py)] (δ 1949 to 3374 ppm). For the majority of these compounds data were obtained from solutions in chloroform and in toluene at temperatures of 247 and 300 K; for [Rh(X)(PPh 3 ) 3 ] (δ −562 to −4 ppm) data are reported at a number of temperatures in the range 195–300 K for solutions in chloroform, toluene and dichloromethane and at 300 K for solutions in DMSO. The expected trend to lower δ( 103 Rh) with decreasing temperature (vibrational shielding) is observed for the dichloromethane data, but data from solutions {of [Rh(X)(PPh 3 ) 3 ]} in chloroform and toluene show a number of features which diverge from this pattern, i.e. shifts to higher δ are found to accompany a decrease in temperature, most noticeably where X = CN and Cl [on changing the solvent from dichloromethane to chloroform changes in δ( 103 Rh) of up to 172 ppm are observed]. These results are interpreted in terms of a hydrogen‐bonded interaction with the solvent that is enhanced by the presence of a polarizable ligand (CN, Cl). With a ligand (O 2 CCF 3 ) that is only weakly polarizable the solvent dependence of δ( 103 Rh) is minimal. Copyright © 2004 John Wiley & Sons, Ltd.