Bis(2,6-dinitroaryl)platinum(II) Complexes. Cis/Trans Isomerization†

The complexes cis-[Pt(κ2-Aryl)(κ1-Aryl)L] (κ2-Aryl = κ2-(C,O)-C6(NO2)2-2,6-(OMe)3, κ1-Aryl = κ1(C)-C6(NO2)2-2,6-(OMe)3, L = S-dmso (2cis), XyNC (4cis; Xy = 2,6-Me2C6H4), CO (5cis), PPh3 (7cis))
have been obtained by reacting at room temperature cis-[Pt(κ2-Aryl)(κ1-Aryl)(OH2)] (1cis) with dimethyl
sulfoxide (dmso; 1:1 or excess), XyNC (1:1), or CO (excess) or cis-(Me4N)[Pt(κ2-Aryl)(κ1-Aryl)Cl] with
PPh3 (1:1), respectively. The room-temperature reaction of 1cis with XyNC (1:2), of 5cis with PPh3
(1:1), or of cis-(Me4N)[Pt(κ2-Aryl)(κ1-Aryl)Cl] with PPh3 (1:2) gives cis-[Pt(κ1-Aryl)2LL‘] (L = L‘ =
XyNC (3cis), PPh3 (8cis); L = CO, L‘ = PPh3 (6cis)). Complexes 3cis, 4cis, and 5cis isomerize on
heating in solution or in the solid state to give 3trans, 4trans, and 5trans, respectively, while 6cis and
8cis decompose to give 7cis instead of their trans isomers; these, however, can be prepared by reacting
5trans or 6trans with PPh3 in molar ratios of 1:1 or 1:2, respectively. When they are heated, 6trans and
8trans also descompose to 7cis, while 2cis and cis-[Pt(κ2-Aryl)(κ1-Aryl)L] (L = H2O (1cis), PhCN, tht)
decompose to a mixture of unidentified products (1cis) or are recovered unchanged. These results, and
others reported in the literature, on the stability of cis- and trans-diaryl complexes of platinum or palladium
can be explained as the result of two competing factors, transphobia and the steric requirements of the
ligands. The X-ray crystal structures of 2cis, 3cis, 3trans, 4trans·CHCl3, 5cis·CH2Cl2, 5cis·0.5hexane,
6cis, 6trans·CHCl3, 7cis·Me2CO, and 8trans·0.5CHCl3 have been determined.

通过室温下将cis-[Pt(κ2-芳基)(κ1-芳基)(OH2)] (1cis) 与二甲基亚砜 (dmso; 摩尔比为1:1或过量)、XyNC (摩尔比为1:1) 或CO (过量) 反应，或分别与cis-(Me4N)[Pt(κ2-芳基)(κ1-芳基)Cl] 与PPh3 (摩尔比为1:1) 反应，获得了cis-[Pt(κ2-芳基)(κ1-芳基)L] (κ2-芳基 = κ2-(C,O)-C6(NO2)2-2,6-(OMe)3, κ1-芳基 = κ1(C)-C6(NO2)2-2,6-(OMe)3, L = S-dmso (2cis), XyNC (4cis; Xy = 2,6-Me2C6H4), CO (5cis), PPh3 (7cis))的复合物。1cis与XyNC在摩尔比为1:2的条件下反应，5cis与PPh3在摩尔比为1:1的条件下反应，或cis-(Me4N)[Pt(κ2-芳基)(κ1-芳基)Cl] 与PPh3在摩尔比为1:2的条件下反应，均能得到cis-[Pt(κ1-芳基)2LL‘] (L = L‘ = XyNC (3cis), PPh3 (8cis); L = CO, L‘ = PPh3 (6cis))。复合物3cis、4cis和5cis在溶液或固态加热时发生异构化，分别生成3trans、4trans和5trans，而6cis和8cis则分解生成7cis，而非其反式异构体；然而，通过将5trans或6trans与PPh3以摩尔比为1:1或1:2反应，可以制备这些反式异构体。加热6trans和8trans时，它们也会分解为7cis，而2cis和cis-[Pt(κ2-芳基)(κ1-芳基)L] (L = H2O (1cis), PhCN, tht) 则分解为未知的产物混合物（1cis）或无变化地回收。这些结果，以及其他文献中报道的关于铂或钯的cis-和trans-二芳基复合物的稳定性结果，可以归因于两个相互竞争的因素：反式恐惧和配体的空间需求。已确定了2cis、3cis、3trans、4trans·CHCl3、5cis·CH2Cl2、5cis·0.5hexane、6cis、6trans·CHCl3、7cis·Me2CO和8trans·0.5CHCl3的X射线晶体结构。