Higher coordinate gold(I) complexes with the weak Lewis base tri(4-fluorophenyl) phosphine. Synthesis, structural, luminescence, and DFT studies

• Three- and four-coordinate gold(I) complexes are described.
• H-bonding and enhanced p-interaction causes structural transformation.
• Metal perturbed ligand based emission is observed.

The structures and spectroscopic properties of two high coordinate gold(I) phosphine complexes with the TFFPP=tri(4-fluorophenyl)phosphine ligand are reported. Synthesis in a 1:3 metal to ligand ratio provided the compound [AuCl(TFFPP)3] (2) that crystallize in the P1¯ space group, where the asymmetric unit consists of three independent molecules. In all three sites, two sets of bond angles display distinctly different ranges. The three P–Au–P angles have average values of 117.92°, 117.57°, and 114.78° for sites A, B, and C, with the corresponding P–Au–Cl angles of 98.31°, 99.05°, and 103.38°, respectively. The chloride ion coordinates as the fourth ligand, at the corresponding Au–Cl distance of 2.7337, 2.6825, and 2.6951 Å for the three sites. This distance is longer by 0.40–0.45 Å than the Au–Cl distance found in the mono TFFPP complex 1 (2.285 Å) indicating a weakening of the Au–Cl interaction as the coordination number increases. In compound 3, [Au(TFFPP)3]Cl·½CH2Cl2·H2O, the structure consists of three phosphine ligands bound to the gold(I) atom, but the Cl− exists as uncoordinated counter anion. The structural differences observed in the two complexes are attributable to crystal-packing effects caused by the introduction of H-bonding as well as enhanced intra and inter-molecular π-interaction in 3. The photoluminescence of the complexes compared with that of the ligand show ligand centered emission perturbed by the metal coordination. Theoretical DFT studies conducted on these complexes supports assignments of the electronic transitions observed in these systems.

Crystal-packing effects caused by the introduction of H-bonding as well as enhanced intra and inter-molecular π-interaction influences the extent of inner sphere complexation.Figure optionsDownload as PowerPoint slide