Syntheses and Structural Characterization of Tetrahedral Four-Coordinate Gold(I) Complexes of 1,3,5-Triaza-7-phosphaadamantane. An Example of a Hydrogen-Bond-Directed Supramolecular Assembly

The synthesis and structural characterization of water-soluble four-coordinate gold(I) complexes containing monodentate phosphine ligands are described. The ligands used are 1,3,5-triaza-7-phosphaadamantane (TPA) and its protonated and methylated derivatives, [HTPA]Cl and [MeTPA]I. Formation of the four-coordinate gold(I) species is favored by the small cone angle of the phosphine (102°) and its ability to form a hydrogen-bonded network between the nitrogen atoms of the ligand and solvent water molecules. The gold center in all four complexes has a nearly regular tetrahedral geometry with an average P−Au−P angle of 109.5°. [(HTPA)₃(TPA)Au](PF₆)₄·4H₂O·CH₃CN (1) crystallizes in the monoclinic space group P2₁/c (No. 14) with cell constants a = 20.719(3) Å, b = 15.606(2) Å, c = 17.854(2) Å, β = 114.03(1)°, and Z = 4. Refinement of 4977 reflections and 650 parameters yields R = 0.0396 and R_w = 0.0500. [(TPA)₄Au]PF₆·1.5HCl·H₂O (2), crystallizes in the monoclinic space group C2/c (No. 15) with cell constants a = 33.036(7) Å, b = 11.212(2) Å, c = 31.503(5) Å, b = 137.58(1)°, and Z = 8. Refinement of 3835 reflections and 470 parameters yields R = 0.0351 and R_w = 0.0403. [(TPA)₄Au]Cl₄·6H₂O (3) was characterized structurally in the cubic space group Fdm (No. 227) with cell constants a = b = c = 20.020(2) Å and Z = 8. Refinement of 290 reflections and 28 parameters yields R = 0.0624 and R_w = 0.1291. [(MeTPA)₄Au](PF₆)₅·2CH₃CN (4) crystallizes in the monoclinic space group C2/c (No. 15) with cell constants a = 23.337(3) Å, b = 14.855(3) Å, c = 35.317(5) Å, b = 97.95(1)°, and Z = 8. Refinement of 7840 reflections and 621 parameters yields R = 0.0493 and R_w = 0.0698.