Phosphides 61 coordination complexes

Phosphines readily form phosphine sulphides, they react vigorously with halogens to form halo-phosphines, and with alkali metals to form metal phosphides. Because of their unshared electron pairs, organophosphines can form a great variety of coordination complexes with metals (Chapter 8). Phosphines are bases their base strengths depend on the degree and nature of substitution to a... 

Whilst almost all metals are included here in the treatment of metal phosphides (Sections 8.1 through 8.7), the treatment of metallophosphorus coordination complexes (Sections 8.9 through 8.20) deals mostly with transition metals. The discussion of metal phosphines and metal phosphites (Section 8.8) is largely confined to metals from Groups I through in while compounds with p-block metals are dealt with in Chapter 9 (Eigure 8.1). 

Early studies of metal phosphides were carried out by Pelletier [1] in 1789, and the first metallq)hospho-rus coordination complex (M-P-E type with E=H), was reported by Rose [2] in 1832. The first M-P-E type with E=C was a tertiary phosphine complex made by Hoffmann [3] in 1857. Although this was followed by the synthesis of a few other complexes of this type by Cahors and Gal in 1870, it was not until after the pioneering work of Mann, Chatt [4] and Jensen [5] in the field of organometallic chemistry during the 1930-1960, that the exponential rise of metallophosphorus chemistry was to begin. 

In accordance with the electropositive nature of the bridgehead atoms, all di(pyridyl) substituted anions behave like amides with the electron density accumulated at the ring nitrogen atoms rather than carbanions, phosphides or arsenides. The divalent bridging atoms (N, P, As) in the related complexes should in principle be able to coordinate either one or even two further Lewis acidic metals to form heterobimetallic derivatives. According to the mesomeric structures, (Scheme 7), it can act as a 2e- or even a 4e-donor. However, theoretical calculations, supported by experiments, have shown that while in the amides (E = N) the amido nitrogen does function as... 

More recently this same phosphide has been structurally characterized as the LiCl adduct, [(THF)LiCl (THF)2Li(PBu2)]2 (34). Again the structure takes the form of a four-rung ladder however, the central two rungs are now part of a Li2Cl2 cycle and the two terminal Li atoms are each coordinated by two molecules of THF. The ladder motif is broken down by the addition of the bidentate ligand DME The recently reported complex [Li(PBu2)(DME)]2 (DME = 1,2-dimethoxy-... 

Bun, Bus, Bu1) (99). The complex with R = Me crystallizes as the THF solvate [MeCu(PBu2)Li(THF)3] in which the phosphide ligand bridges the two-coordinate Cu and four-coordinate Li centers. These cuprates were found to be more thermally stable than other phosphido(alkyl)-cuprates but less reactive toward electrophiles than related cyanocu-prates. 

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