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Deoxygenation of phosphole oxide dimers with HSiCl3–C5H5N, but not HSiCl3 alone, gives stable diphosphines whose phosphorus atoms in the syn-7-phosphanorbornene position have the most deshielded 31P n.m.r. shifts ever reported for tertiary phosphines.
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Quin et al. (1980) studied this question.
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