Reactions of 1,4-benzoquinones with s^2 reducing centers

Aqueous solutions of Sn(II) and Ge(II)(in chloride media) and In(I)(in perchlorate media) react quantitatively with 1,4-benzoquinone and its 2,5-(OH)2 and 2,5-Cl2-3,6-(OH)2 derivatives, reducing the oxo-functions to 1,4-(OH)2. For Sn(II) and Ge(II), reaction is accelerated by incorporation of 2,5-(OH)2 substituents and by chloroanation of the s2 center. The most reactive reducing Sn(II) species are SnCl3for benzoquinone and dihydroxyquinone but SnCl2(aq)x for the dichloroquinone. Reductions by Ge(II) proceed mainly through a species (probably GeCl42-) having one more chloride than the predominant form. The activated complex for the (OH)2bzq-Ge(II) reaction features two germanium centers, only one of which is involved in the reduction act. Reductions of these quinones by In(I) proceed 10^2-10^3 times as rapidly as those by Sn(II) and Ge(II) and are not accelerated by hydroxylation of the quinone ring.