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

Several 1:1 adducts of galli- um trihalides with triarylphosphines, X3GaA3 )( X= Cl, Br, and I; PR3 = triarylphosphine ligand), were investi- gated by using solid-state 69/71 Ga and 31 P NMR spectroscopy at different magnetic-field strengths. The 69/71 Ga nuclear quadrupolar coupling parame- ters, as well as the gallium and phos- phorus magnetic shielding tensors, were determined. The magnitude of the 71 Ga quadrupolar coupling con- stants (CQA 71 Ga)) range from approxi- mately 0.9 to 11.0 MHz. The spans of the gallium magnetic shielding tensors for these complexes, d11� d33, range from approximately 30 to 380 ppm; those determined for phosphorus range from 10 to 40 ppm. For any given phos- phine ligand, the gallium nuclei are most shielded for X = I and least shielded for X = Cl, a trend previously observed for In III -phosphine com- plexes. This experimental trend, attrib- uted to spin-orbit effects of the halogen ligands, is reproduced by DFT calcula- tions. The signs of CQA 69/71 Ga) for some of the adducts were determined from the analysis of the 31 P NMR spectra ac- quired with magic angle spinning (MAS). The 1 J( 69/71 Ga, 31 P) and DJ( 69/71 Ga, 31 P) values, as well as their signs, were also determined; values of 1 JA 71 Ga, 31 P) range from approximately 380 to 1590 Hz. Values of 1 J( 69/71 Ga, 31 P) and DJ( 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 diffrac- tion data for Br3Ga(PAp-Anis)3) and I3Ga(PAp-Anis)3) were obtained.