An Investigation of 1:1 Adducts of Gallium Trihalides with Triarylphosphines by Solid‐State 69/71 Ga and 31 P NMR Spectroscopy

Several 1:1 adducts of gallium trihalides with triarylphosphines, X 3 Ga(PR 3 ) (X=Cl, Br, and I; PR 3 =triarylphosphine ligand), were investigated by using solid‐state 69/71 Ga and 31 P NMR spectroscopy at different magnetic‐field strengths. The 69/71 Ga nuclear quadrupolar coupling parameters, as well as the gallium and phosphorus magnetic shielding tensors, were determined. The magnitude of the 71 Ga quadrupolar coupling constants ( C Q ( 71 Ga)) range from approximately 0.9 to 11.0  MHz . The spans of the gallium magnetic shielding tensors for these complexes, δ 11 − δ 33 , range from approximately 30 to 380 ppm; those determined for phosphorus range from 10 to 40 ppm. For any given phosphine ligand, the gallium nuclei are most shielded for X=I and least shielded for X=Cl, a trend previously observed for In III –phosphine complexes. This experimental trend, attributed to spin‐orbit effects of the halogen ligands, is reproduced by DFT calculations. The signs of C Q ( 69/71 Ga) for some of the adducts were determined from the analysis of the 31 P NMR spectra acquired with magic angle spinning (MAS). The 1 J ( 69/71 Ga, 31 P) and Δ J ( 69/71 Ga, 31 P) values, as well as their signs, were also determined; values of 1 J ( 71 Ga, 31 P) range from approximately 380 to 1590 Hz. Values of 1 J ( 69/71 Ga, 31 P) and Δ J ( 69/71 Ga, 31 P) calculated by using DFT have comparable magnitudes and generally reproduce experimental trends. Both the Fermi‐contact and spin‐dipolar Fermi‐contact mechanisms make important contributions to the 1 J ( 69/71 Ga, 31 P) tensors. The 31 P NMR spectra of several adducts in solution, obtained as a function of temperature, are contrasted with those obtained in the solid state. Finally, to complement the analysis of NMR spectra for these adducts, single‐crystal X‐ray diffraction data for Br 3 Ga[P( p ‐Anis) 3 ] and I 3 Ga[P( p ‐Anis) 3 ] were obtained.