Tuning the properties of the osmium nitrido group in TpOs(N)X2 by changing the ancillary ligand
Tuning the properties of the osmium nitrido group in TpOs(N)X2 by changing the ancillary ligand
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DOI：
10.1021/ic0260264
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发表时间：
2003-01-27
影响因子：
4.6
通讯作者：
Mayer, JM
中科院分区：
文献类型：
--
作者：
Dehestani, A;Kaminsky, W;Mayer, JM
TpOs(N)Cl-2(1)与过量的乙酸银（Tp =三吡唑酸氢酯）反应形成TpOs(N)(OAc)(2)(2)。用质子酸HX处理2得到锇（VI）配合物TpOs(N)X-2，其中X =三氟乙酸（TFA, 3）、三氯乙酸（TCA, 4）、三溴乙酸（TBA, 5）、溴化物(6)、草酸（X2 = O2C2O2, 7）或硝酸盐（ONO2, 8）。1-8的循环伏安法研究表明，Os-VI到Os-V的不可逆还原在0.63 V范围内变化。在N-15核磁共振化学位移、v（OsdropN）拉伸频率和光学吸光度方面观察到的相对变化要小得多。化合物1-8均与PPh3发生亲核攻击，生成TpOs(NPPh3)X-2。更多的吸电子配体x加速了反应，尽管影响很小，但相对速率与峰还原电位相关：速率变化仅为10(2)，而E-p，E-c的0.63 V变化对应于电子转移平衡常数的变化类似于10（11）。化合物1-8也与三苯硼BPh3反应，生成硼酰苯胺配合物TpOs[N(Ph)BPh2]X-2。然而，与BPh3反应生成Os-IV硼酰氨基配合物的速率常数通常与单电子还原电位无关。这可能是由于BPh3反应的机制是一个两步过程，而不是简单的亲核攻击。
TpOs(N)(OAc)(2) (2) is formed upon reaction of TpOs(N)Cl-2 (1) with excess silver acetate (Tp = hydrotrispyrazolylborate). Treatment of 2 with protic acids HX gives the osmium(VI) complexes TpOs(N)X-2, where X = trifluoroacetate (TFA, 3), trichloroacetate (TCA, 4), tribromoacetate (TBA, 5), bromide (6), oxalate (X2 = O2C2O2, 7), or nitrate (ONO2, 8). Cyclic voltammetry studies of 1-8 show irreversible reductions of Os-VI to Os-V, varying over a range of 0.63 V. Much smaller relative variations are observed in N-15 NMR chemical shifts, v(OsdropN) stretching frequencies, and optical absorbances. Compounds 1-8 all react with PPh3 by nucleophilic attack at the nitride ligand, yielding TpOs(NPPh3)X-2. The reactions are accelerated by more electron withdrawing ligands X. The relative rates correlate with the peak reduction potentials although the effect is small: the rates vary by only 10(2) while the 0.63 V change in E-p,E-c corresponds to a change in equilibrium constant for electron transfer of similar to10(11). Compounds 1-8 also react with triphenylboron, BPh3, with formation of borylanilido complexes TpOs[N(Ph)BPh2]X-2. However, rate constants for reactions with BPh3 to yield Os-IV boryl-amido complexes do not in general correlate with one-electron-reduction potentials. This is likely due to the mechanism of the BPh3 reactions being a two-step process and not simply nucleophilic attack.