Phosphide ions

Self-Test 2.2A Predict the chemical formula and electron configuration of the phosphide ion. 

D.12 Write formulas for the ionic compounds formed from (a) calcium and chloride ions (b) iron(III) and sulfate ions (c) ammonium and iodide ions (d) lithium and sulfide ions (e) calcium and phosphide ions. 

Because PH3 is the very weak parent acid of the strong Bronsted base P3, we can form phosphine by protonating phosphide ions with a Bronsted acid. Even water is a sufficiently strong proton donor ... 

White phosphorus, a strained tricyclic system has a low nucleophilic reactivity but is highly electrophilic. 2) Attack by a nucleophile produces a reactive phosphide ion which is rapidly protonated in hydroxylic media. For high yields of a required product it is essential to trap this ion with a suitable electrophile. 3) Owing to the mutual reaction of nucleophile and electrophile the number of useful combinations is limited. In principle a combination of hard nucleophile and soft electrophile is preferred. 

What charge ion is sodium likely to form How about a phosphide ion How about a barium ion ... 

The name of a simple anion is also formed from the name of the element, but it ends in -ide. Thus, Cr is the chloride ion, 0 is the oxide ion, and is the phosphide ion. 

Recall from Section 8.2 that a sample of an ionic compound contains crystals formed from many ions arranged in a pattern. Because no single particle of an ionic compound exists, ionic compounds are represented by a formula that provides the simplest ratio of the ions involved. The simplest ratio of the ions represented in an ionic compound is called a formula unit. For example, the formula KBr represents a formula unit for potassium bromide because potassium and bromide ions are in a one-to-one ratio in the compound. A formula unit of magnesium chloride is MgCl2 because two chloride ions exist for each magnesium ion in the compound. In the compound sodium phosphide, three sodium ions exist for every phosphide ion. What is the formula unit for sodium phosphide ... 

Write out complete electron configurations for the atoms of the Group VA elements nitride ion, N and phosphide ion,... 

The red metastable product, produced from P4 and KOH or KOEt, does not appear to be an intermediate in these, tertiary phosphine oxide syntheses, since when separately prepared, gave only minor amounts of phosphine oxide. This result indicates that the olefinic compounds must attack an earlier intermediate. The initial step was thought to involve nucleophilic attack of hydroxide ion on tetrahedral white phosphorus to give a phosphide ion that subsequently underwent a Michael-Addition to the electrophilic unsaturated compounds present (Rauhut, Bemheimer and Semsel). 

Write formulas that correspond to the following names for monatomic ions (a) phosphide ion, (h) lithium ion, and (c) cohalt(ll) ion. 

The reactions of nucleophiles with elemental phosphorus usually lead to complex mixtures derived from the intermediate phosphide ion, which is captured by a proton or Lewis acid to give mixtures of products derived from phosphorous acid and phosphine.2... 

DePuy and coworkers have studied the gas-phase ion-molecule reactions of the phosphide ion. A number of reactions were observed which result in phosphorus-carbon bond formation, including Sn2 reactions (equation 60), adduct formation (equation 61) and the formation of the low-valent ions PCO (equation 62) and PCS (equation 63). The latter ion is also formed in a reaction between HP=F and CS2, for which the mechanism shown in Scheme 2 has been proposed ... 

Nonmetal ions As shown in Table 7.3, nonmetals gain the number of electrons that, when added to their valence electrons, equals 8. For example, consider phosphorus, with five valence electrons. To form a stable octet, the atom gains three electrons and forms a phosphide ion with a 3- charge. Likewise, oxygen, with six valence electrons, gains two electrons and forms a oxide ion with a 2- charge. 

Dramatic downfield shifts accompany the cleavage of P-substituents with formation of phospholide ions. These shifts are considerably further downfield than those for simpler phosphide ions, and have been taken to be a reflection of strong electron delocalization in the phospholide ion (see Section 2.15.2). Data are collected in Table 6, where it will be seen that typical shifts fall in the region -t-70 to -t-100. Once again the 3,4-dimethyl shielding effect is present and indeed is of the largest size (A 21.4 ppm) of all families examined. Phospholide ions with this substitution have shifts in the range -t- 50 to -t- 60. 

Compared to noncyclic phosphide ions, phospholide ions show a definite decrease in basicity that is consistent with the high degree of electron delocalization evident from other properties (see Sections 2.15.2 and 2.15.3.2). The ions (56) and (57) in THF solution were found not to be protonated by ethanol, implying an acidity for the conjugate acid (the 1 fl-phosphole) greater than that of ethanol, pi a 15.9 in water <79CC40l>. 

Reaction 15.10 yields Li2Pi6, while Li3P2i and Li4P26 can be obtained by altering the ratio of P4 LiPH2. The structures of the phosphide ions [Pie], 15.9, [P2i], 15.10, and [P26] are related to one chain in Hittorf s and fibrous red phosphorus (Figure 15.3b). 

Examples of stable phosphide ions are in compounds such as (K 18-crown)+ P(CN)2 and (Figure 6.15). The P(Cp3)2 anion decomposes above -30°C in CHCI3 solution, but is stabilised in the form of the complex (18 crown K)+ [P(CF3)2 82] . The bis trifluoromethyl phosphide anion is present in the stable salt Et4N+ P(Cp3)2 and is a useful phosphide transfer agent [71]. 

From the name, we know that barium phosphide is composed of barium and phosphide ions. First write down the formulas of these ions ... 

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