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This topic is large and complex but it might be worthwhile trying to reorganize it so that it emphasized the most significant species and distributed space vaguely in proportion to the "real world." One possible outline for the article:
Phosphorus(III) species: phosphine (PH2-nRn, including PM2-nRn where M = Li, Na); phosphinites (P(OR)R2); phosphonite (P(OR)2R); brief mention of phosphites (P(OR)3) (brief since these are not really organophosphorus - or again should we not worry about that formality?)
Phosphorus(I) species: mainly (PR)n and RP=PR
Other mixed valence species (a potentially sprawling theme, which could get large)
for each of the above sections, we could include something on "related species," e.g. PXR2, X = NR2, Cl; and EPR3 (E = S, NR)
for each of the sections above we could include subsections on "synthesis," "applications," and possibly "new developments" (to cover the researchy themes in the current article). Editors are welcome to disagree with the above or whatever.