Phosphinogold(I) complexes and methods of treating cancer

A gold(I) complex of formula (I)

• or a salt thereof, a solvate thereof, a tautomer thereof, a stereoisomer thereof, or a mixture thereof,
• wherein:
• R1 and R2 are each independently an optionally substituted aryl;
• R3 is selected from the group consisting of —OH, —OCH3, —NH2, and —N(CH3)2;
• R4 is a halogen or
• and
• n is an integer in a range of 1-3,
• wherein R5 and R6 are each independently selected from the group consisting of a hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, an optionally substituted arylalkyl, and an optionally substituted aryl.