13 C and proton nuclear magnetic resonance spectra of trans ‐[arylbromobis(triethyl phosphine)palladium(II)] and related compounds. The π‐donor ability of the Ni(PEt 3 ) 2 X, Pd(PEt 3 ) 2 X and Pt(PEt 3 ) 2 X groups

13 C and proton NMR spectra of several arylpalladium and some arylnickel and arylplatinum complexes have been compared. The Ni(PEt 3 ) 2 X and Pd(PEt 3 ) 2 X substituents induce a paramagnetic shift of C ipso (of the phenyl ring) which is much larger than that induced by Pt(PEt 3 ) 2 X. However, there are no significant differences along the Ni/Pd/Pt series for the ortho, meta and para positions. For the six compounds of general formula trans ‐[ArPdBr(PEt 3 ) 2 ] reported here, the mean Δ(δ) C values induced on the ArH by the introduction of the PdBr(PEt 3 ) 2 substituent are found to be 26.9 (C ipso ), 7.2 (C ortho ), −1.1 (C meta ), −5.5 (C para ), −0.03 (H ortho ), −0.28 (H meta ) and −0.38 ppm (H para ).