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Coordination chemistry of gold(II) complexes
The number of complexes with gold in a formal oxidation state of two have increased considerably and nowadays this oxidation state can be considered nearly as a common state in gold chemistry. This review covers the evolution of the knowledge of this oxidation state from the first dithiocarbamate derivatives [Au2(S2CNR2)2X2], stable only at very low temperature, to the room temperature stable dinuclear gold complexes [Au2(L–L)2X2] (L–L=CH2PPh2CH2, CH2PPh2S, C5H4PPh2-2; X=halogen). Although a dinuclear structure with a gold(II)–gold(II) bond supported by two equal bridging ligands were the first and most common, this review shows the present diversity as mononuclear, [Au([9]aneS3)2](BF4)2, dinuclear with two different bridging ligands, [Au2(S2CNR2)(CH2PPh2CH2)X2], with a non-supported metal–metal bond, [Au2(Ph2PC8H6PPh2)2Cl2](PF6)2, and polynuclear gold(II) complexes either with chains of only gold centers or with other metals, such as [{(C6F3H2)Au(CH2PPh2CH2)2Au}2Au2(CH2PPh2CH2)2]ClO4 or [Au2Pt(CH2PPh2S)4X2]
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