氯化铜的少溶剂固态连串配位化学反应

Less solvent solid‑state consecutive coordination reaction of copper chloride

在少量水的存在下,由于NH_(4)[CuCl_(3)]对水不稳定,CuCl_(2)·2H_(2)O与氯化铵的配位化学反应只能得到1∶2产物(NH_(4))_(2)[CuCl_(4)(H_(2)O)_(2)];但在无水乙醇中,无水CuCl_(2)与氯化铵按1∶1或1∶2的物质的量之比混合时,能相应地得到NH4[CuCl_(3)]或(NH_(4))_(2)[CuCl_(4)]。CuCl_(2)·2H_(2)O与2,2′-联吡啶(bipy)的少溶剂固态化学反应仍能像固态化学反应一样,根据反应物的配比生成相应的唯一产物,但在物质的量之比为1∶1的反应中发现1∶2产物曾经形成。热力学分析说明,如果连串反应的后一步的ΔrG大于前一步的,则上述反应现象是可能的。

The less solvent solid-state reaction(LSR)between CuCl_(2)·2H_(2)O and NH_(4)Cl in a little water produced only(NH_(4))_(2)[CuCl_(4)(H_(2)O)_(2)]since NH_(4)[CuCl_(3)]was not stable in water;however,in a little absolute ethanol at 60℃,the LSR produced NH_(4)[CuCl_(3)],or(NH_(4))_(2)[CuCl_(4)]according to the mixed stoichiometric ratio.The LSR of CuCl_(2) and NH4Cl in a 1∶2 molar ratio proceeds in two steps:the formation of NH_(4)[CuCl_(3)]at an early stage and a further reac-tion between NH4[CuCl_(3)]and remaining NH_(4)Cl to form the final product(NH_(4))_(2)[CuCl_(4)].In contrast,the LSR of CuCl_(2)·2H_(2)O and 2,2′-bipyridine(bipy)in 1∶1 molar ratio in a little water produced solely[Cu(bipy)Cl_(2)],but the 1∶2 product,[Cu(bipy)_(2)Cl_(2)]·2H_(2)O did appear in its early stage.The reason may be that the structure of the solid CuCl_(2)·2H_(2)O,which is polymerized planer trans-[CuCl_(2)(H_(2)O)_(2)],converts to molecular trans-[CuCl_(2)(H_(2)O)_(4)]in water,and the latter makes the activation energy of successive substitution of two H_(2)O molecules by bipy closer.Thus,bipy rapidly and successively replaces four water molecules in trans-[CuCl_(2)(H_(2)O)_(4)]to form a 1∶2 product.This surprising result indicates that the LSR of[Cu(bipy)_(2)Cl_(2)]·2H_(2)O and CuCl_(2)·2H_(2)O is also spontaneous,and according to thermodynam-ics,it is possible if the Δr G⊖of the second reaction is bigger than that of the first one of the consecutive reactions.Therefore,the LSR could also proceed stepwise,which is hard to find in solution reactions.