Macdonald Charles L B, Binder Justin F, Swidan Ala'aeddeen, Nguyen Jennifer H, Kosnik Stephanie C, Ellis Bobby D
Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.
Inorg Chem. 2016 Jul 18;55(14):7152-66. doi: 10.1021/acs.inorgchem.6b01163. Epub 2016 Jun 29.
A safe, convenient, and P-atom-efficient synthesis of N-heterocyclic-carbene- (NHC-) stabilized phosphorus(I) bromide salts is reported that involves P(+) transfer from an easily prepared triphosphenium precursor. The resulting family of phosphamethine cyanine dyes featuring N,N'-dialkyl-substituted 4,5-dimethylimidazole-2-ylidenes ((R)NHC(Me)) and benzimidazole-2-ylidenes ((R)NHC(B)) (R = Me, Et, iPr) have been fully characterized. We found that increasing N-alkyl group size causes increased twisting of the carbene fragments from the C-P-C plane, which decreases the magnitude of hyperconjugation between the π-type lone pair on phosphorus and the carbene fragments. This decrease is manifested as changes in the (31)P NMR chemical shifts, magnitudes of the P-C coupling constants, and electronic spectra of the cations. The reactivities of these ions toward various oxidants are reported: Oxidation by sulfur generates dithiophosphinium salts, protonation or methylation gives dicationic phosphines, and coordination to 1 or 2 equiv of gold(I) chloride results in mono or bimetallic complexes, respectively.
报道了一种安全、便捷且磷原子高效的N-杂环卡宾（NHC）稳定的溴化磷（I）盐的合成方法，该方法涉及从易于制备的三膦鎓前体进行P(+)转移。所得的磷甲亚胺菁染料家族，其特征在于N,N'-二烷基取代的4,5-二甲基咪唑-2-亚基（(R)NHC(Me)）和苯并咪唑-2-亚基（(R)NHC(B)）（R = 甲基、乙基、异丙基）已得到充分表征。我们发现，N-烷基基团尺寸的增加会导致卡宾片段从C-P-C平面发生更大程度的扭曲，这会降低磷上的π型孤对与卡宾片段之间的超共轭程度。这种降低表现为(31)P NMR化学位移、P-C耦合常数的大小以及阳离子电子光谱的变化。报道了这些离子对各种氧化剂的反应性：被硫氧化生成二硫代膦鎓盐，质子化或甲基化生成二价阳离子膦，与1或2当量的氯化金（I）配位分别生成单金属或双金属配合物。
