Syntheses of mixed-ligand tetranuclear gold(I)-nitrogen clusters by ligand exchange reactions with the dinuclear gold(I) formamidinate complex Au2(2,6-Me2Ph-form)2

The reaction of the sterically crowded dinuclear gold(I) amidinate complex Au-2(2,6-Me2Ph-form)(2), 1, with the less bulky bidentate nitrogen ligands results in the formation of tetranuclear gold(I) complexes. When the less bulky amidinate, K(4-MePh-form), A, was reacted with 1 in a 1:1 stoichiometric ratio, crystals containing equal amounts of the tetranuclear and dinuclear gold(I) aryl formamidinates, Au-4(4-MePh-form)(4) and Au-2(2,6-Me2Ph-form)(2), where 2,6-Me2Ph-form = B, were found in the same unit cell, 2 center dot 2THF: space group P(1) over bar, a = 10.794(11) angstrom, b = 14.392(15) angstrom, c = 25.75(3)degrees, alpha = 82.564(17)degrees, beta = 85.443(18)degrees, gamma = 82.614(19)degrees. The reaction of K(4-MePh-form), A, and 1 in a 1:2 ratio (excess) produced the tetranuclear complex only, 3. The potassium salt of the exchanged bulky ligand, K(2,6-Me2Ph-form), formed as a byproduct. The reaction of the dinuclear gold(I) complex Au-2(2,6-Me2Ph-form)(2) with the 3,5-diphenylpyrazolate salt, K(3,5-Ph(2)pz), resulted in the formation of two tetranuclear mixed-ligand complexes, Au-4(3,5-Ph(2)pz)(2)(2,6-Me2Ph-form)(2)center dot 2THF, 4 center dot 2THF (space group P2(1)/c, a = 11.5747(19) angstrom, b = 25.497(4) angstrom, c = 21.221(3) angstrom, beta = 96.979(3)degrees) and Au-4(3,5-Ph(2)pz)(3)(2,6-Me2Ph-form)center dot THF, 5 center dot THF (space group P2(1)/c, a = 23.058(5) angstrom, b = 14.314(3) angstrom, c = 18.528(4) angstrom, beta = 90.94(3)degrees. The block crystals from the tetranuclear complex, 4 center dot 2THF, contain mixed ligands with each pyrazolate ring facing an amidinate ring. The tetranuclear mixed ligand complex, 5 center dot THF, was isolated as needles with ligands alternating above and below the Au-4 plane. The two tetranuclear mixed-ligand complexes emit at 490 and 530 nm, respectively, under UV excitation.