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Synthesis, Characterization, and Electrochemical Analyses of Vanadocene Tetrametaphosphate and Phosphinate Derivatives
Organometallics ( IF 2.5 ) Pub Date : 2018-02-21 00:00:00 , DOI: 10.1021/acs.organomet.7b00797
Timothy G. Carroll 1 , Rachel Garwick 1 , Joshua Telser 2 , Guang Wu 1 , Gabriel Ménard 1
Affiliation  

The synthesis and characterization of a series of new vanadocene-derived tetrametaphosphate or diphenylphosphinate complexes, [PPN]2[CpV(P4O12)] (1), [Cp2VOP(O)Ph2] (2), [CpV(μ2-O2PPh2)4VCp] (3), and [Cp2V(μ2-O2PPh2)2VCp2][PF6]2 (4), is reported ([PPN]+ = bis(triphenylphosphoranylidene)ammonium; Cp = η5-cyclopentadienyl). The complexes were synthesized from the methyl vanadocene (Cp2VMe) precursor, through protonation of the Me or Cp linkages using the tetrametaphosphate or phosphinate acid precursors [PPN]2[P4O12H2] (for 1) and Ph2P(O)OH (for 2 and 3). Oxidation of 2 with [Fc][PF6] resulted in dimerization, yielding the bimetallic 4 ([Fc]+ = ferrocenium). Electrochemical analysis of this reaction revealed a possible ECE mechanism that includes prior and subsequent electron transfer to this dimerization. The electronic structure of the dimer 4 was probed by SQUID magnetommetry and X-band EPR spectroscopy (100 and 4 K). The dimer was found to contain two antiferromagnetically coupled VIV centers, as well as a small portion of monomeric VIV species, 2+. In contrast to 2, oxidation of 1 resulted in an EC mechanism, the product of which remains unknown. Preliminary reactions with compounds 1 and 2 bearing free P═O groups were performed using H atom donors to test their ability to undergo H atom transfer in the context of the proposed “reduction-coupled oxo activation” mechanism; however, no clear reaction pathway supporting this mechanism has yet been observed.

中文翻译:

钒二烯四偏磷酸盐和膦酸酯衍生物的合成,表征和电化学分析

一系列新的钒钒烯衍生的四偏磷酸盐或二苯基次膦酸酯络合物[PPN] 2 [CpV(P 4 O 12)](1),[Cp 2 VOP(O)Ph 2 ](2),[CpV (μ 2 -O 2 PPH 24 VCP](3),和混合[Cp 2 V(μ 2 -O 2 PPH 22 VCP 2 ] [PF 6 ] 24),则报告([PPN] +=双(三苯基亚正膦基)铵;CP =η 5 -环戊二烯基)。通过使用四偏磷酸盐或次膦酸前体[PPN] 2 [P 4 O 12 H 2 ](用于1)和Ph 2 P通过Me或Cp键的质子化反应,由甲基钒二烯(Cp 2 VMe)前体合成配合物。(O)OH(用于23)。用[Fc] [PF 6 ]氧化2导致二聚,产生双金属4([Fc] +=二茂铁)。该反应的电化学分析揭示了可能的ECE机理,该机理包括先前和随后的电子转移至该二聚体。二聚体4的电子结构通过SQUID磁测法和X带EPR光谱法(100和4K)探测。发现该二聚体包含两个反铁磁耦​​合的V IV中心,以及一小部分单体V IV物质2 +。在对比2中,氧化1导致的EC机制,该机制的产品仍然是未知的。与化合物12的初步反应在提出的“还原偶联的羰基活化”机制的背景下,使用H原子供体进行了带有游离P═O基团的测试,以测试它们的H原子转移能力;然而,尚未观察到支持该机制的明确反应途径。
更新日期:2018-02-22
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