Lambic Nikola S, Sommer Roger D, Ison Elon A
Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204, USA.
Dalton Trans. 2018 Jan 15;47(3):758-768. doi: 10.1039/c7dt03615a.
The synthesis of (PNP)Re(N)X (PNP = [2-P(CHMe)-4-MeCH]N, X = Cl and Me) complexes is described. The methylnitridorhenium complex 3 was found to react differently with CO and isocyanides, leading to the isolation of a Re(v) acyl complex 4 and an isocyanide adduct 6. Two parallel pathways were observed for the reaction of 3 with CO: (1) CO inserts into the Re-Me bond to afford 4, and (2) 3 isomerizes by distortion of the aryl backbone of the PNP ligand to afford the isomer 3'. This is followed by the reaction of 3' with CO to afford the tricarbonyl complex 5, which was fully characterized. The contrasting reaction of 3 with 2,6-dimethylphenyl isocyanide lends further support for the proposed isomerization pathway. DFT (M06) calculations suggest that insertion of CNR into the Re-Me bond (27.2 kcal mol) is inaccessible at room temperature. Instead the substrate adds to the metal center via the most accessible face i.e. syn to the rhenium-nitrido bond, to afford 6. The addition of CO to isomer 3' is proposed to proceed with a similar mechanism to 2,6-dimethylphenyl isocyanide.
描述了(PNP)Re(N)X（PNP = [2-P(CHMe)-4-MeCH]N，X = Cl和Me）配合物的合成。发现甲基亚硝基铼配合物3与CO和异腈反应不同，分别得到铼(V)酰基配合物4和异腈加合物6。观察到3与CO反应有两条平行途径：(1) CO插入Re-Me键生成4，(2) 3通过PNP配体芳基主链的扭曲异构化为异构体3'。随后3'与CO反应生成三羰基配合物5，并对其进行了全面表征。3与2,6-二甲基苯基异腈的不同反应进一步支持了所提出的异构化途径。DFT（M06）计算表明，室温下CNR插入Re-Me键（27.2 kcal mol）是不可行的。相反，底物通过最容易接近的面，即与铼-亚硝基键同向，加到金属中心，生成6。3'与CO的加成反应被认为与2,6-二甲基苯基异腈的反应机制相似。
