The synthesis of macrocyclic variants of commonly employed phosphine-based pincer ligands derived from lutidine (PNP-14) and 2,6-dihydroxypyridine (PONOP-14) is described, where the P-donors are trans-substituted with a tetradecamethylene linker. This was accomplished using an eight-step procedure involving borane protection, ring-closing olefin metathesis, chromatographic separation from the cis-substituted diastereomers, and borane deprotection. The rhodium coordination chemistry of these ligands has been explored, aided by the facile synthesis of 2,2'-biphenyl (biph) adducts [Rh(PNP-14)(biph)][BArF4] and [Rh(PONOP-14)(biph)][BArF4] (ArF = 3,5-(CF3)2C6H3). Subsequent hydrogenolysis enabled generation of dihydrogen, ethylene and carbonyl derivatives; notably the ν(CO) bands of the carbonyl complexes provide a means to compare the donor properties of the new pincer ligands with established acyclic congeners.

中文翻译：

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大环PNP和PONOP钳形配体的合成和铑配合物。

描述了衍生自二甲基吡啶（PNP-14）和2,6-二羟基吡啶（PONOP-14）的常用的基于膦的钳形配体的大环变体的合成，其中P-供体被十四亚甲基连接基反式取代。这是通过八步程序完成的，该程序涉及硼烷保护，闭环烯烃复分解，从顺式取代的非对映异构体进行色谱分离以及硼烷脱保护。通过容易地合成2,2'-联苯（biph）加合物[Rh（PNP-14）（biph）] [BArF4]和[Rh（PONOP-14）（ biph）] [BArF4]（ArF = 3,5-（CF3）2C6H3）。随后的氢解使得能够产生二氢，乙烯和羰基衍生物。