and the alkali cations when both of them are present resulted in the inhibition of the formation of metallic rhodium and retarded the growth of the clusters. These results correlate with the enhanced rhodium solubility noted for some catalytic systems that are based on rhodium carbonyl clusters with amines and cesium salts added, and which are used to convert H2/CO mixtures into polyalcohols.
阴离子羰基
铑铑在热解条件下的生长取决于抗衡离子。遵循以下趋势,
铯盐对核原子较高的配合物的出现最不利,而
铵盐则更容易出现:[R 4 N] +(R =烷基)<[R 3 R'N] +(R' =苄基)<[R 3 NH] + <[R 2 NH 2 ] +。羰基铑阴离子和铵阳离子之间的氧化还原反应与簇的热生长有关。这两个部分之间的电子转移过程可能涉及簇的初始断裂,从而形成[Rh(CO)4] -和[Rh(CO)4 ] -还原铵抗衡离子在高温下,尽管还不能排除从多核物质到阳离子的直接电子转移。看起来电子转移先于簇的碎裂,或者平行于簇的碎裂,而所得碎片的聚集反应给出了观察到的产物。由单核或多核络合物形成金属铑,以及为这些物种发现的顺序转变与对高核物种的预期热力学偏好相符。当胺和碱阳离子同时存在时,它们的独立作用的存在导致金属
铑的形成受到抑制并阻碍了簇的生长。2 / CO混合成多元醇。