Synthesis and Reactivity of Multinuclear Gold Complexes with (Diphenylphosphanyl)ferrocene and Oxygen Ligands

Abstract

Au^I complexes combining hard oxygen and soft (diphenylphosphanyl)ferrocene (L) ligands in their molecules were synthesized, viz. the gold hydroxides [Au(OH)(L-κP)] (5) and [{Au(L-κP)}₂ (μ-OH)][BF₄ ] (4), and the oxonium cluster [{Au(L-κP)}₃ (μ₃ -O)][BF₄ ] (1). In-situ auration of 1 produced [{Au(L-κP)}₄ (μ₄ -O)][BF₄ ]₂ (2), which spontaneously converted into a dimeric tetragold complex featuring bridging phosphanylferrocenyl groups geminally diaurated in position 2 of the ferrocene scaffold. The same complex and its isomer incorporating ferrocene-1,1'-diyl bridges resulted similarly from 4. Upon crystallization, compound 5 underwent a redox reaction, producing a structurally unique, crown-like, mixed-valent Au⁰ /Au^I cluster, [Au₇ (L-κP)₆ ]OH. Compounds 1 and 5 were used to prepare the analogous, N-bridged complexes, [{Au(L-κP)}₃ (μ₃ -NFc)][BF₄ ] (Fc=ferrocenyl) and [{Au(L-κP)}₄ (μ₄ -N)][BF₄ ]. The compounds were structurally characterized and further studied by DFT calculations.

Keywords: aurophilicity; cluster compounds; gold; metallocenes; phosphane ligands.