Phosphorus donors, comparison

A number of candidates from our ligand library have been employed in this survey, bearing aliphatic as well as aromatic substituents on the phosphorus donor atoms, together with the benchmark ligands Josiphos and BINAP, which were included in this examination for comparison purposes. The results are collected in Table 1.4.3. 

It is instructive to compare phospholes to other structurally similar phosphorus donors. The most appropriate ligands with which comparisons should be made are phenyldivinylphosphine (I) and dimethylphenylphosphine (II). 

Behrens C, Cichon MK, Grolle F, Hennecke U, Carell T (2004) Excess Electron Transfer in Defined Donor-Nucleobase and Donor-DNA-Acceptor Systems. 236 187-204 Bertrand G, Bourissou D (2002) Diphosphorus-Containing Unsaturated Three-Menbered Rings Comparison of Carbon, Nitrogen, and Phosphorus Chemistry. 220 1-25 Betzemeier B, Knochel P (1999) Perfluorinated Solvents - a Novel Reaction Medium in Organic Chemistry. 206 61-78 Bibette J, see Schmitt V (2003) 227 195-215 Blais J-C, see Astruc D (2000) 210 229-259 Bogar F, see Pipek J (1999) 203 43-61 Bohme DK, see Petrie S (2003) 225 35-73 Bourissou D, see Bertrand G (2002) 220 1-25 Bowers MT, see Wyttenbach T (2003) 225 201-226 Brand SC, see Haley MM (1999) 201 81-129... 

Aminomethylphosphines are convenient objects for a comparison of phosphorus and nitrogen donor ability in complexation reactions. Coordination compounds of heterocyclic aminomethylphosphines with metals are discussed in Section VII. In this section we present reactions of aminomethylphosphines with boranes (BH3). 

Fig. 33. Comparisons of the pseudo-solubility data of Figs. 31 and 29 with model calculations assuming various values of parameter A DH, the binding energy of a positive donor D + and H into DH, AE2, the binding energy of 2H° into H2, and eA, the position of the hydrogen acceptor level relative to midgap. Plots (a) and (b) correspond respectively to the values 1.8 and 1.4 eV for A E2- In each of these, curves are shown for four combinations of the other parameters full curves, AEDH = 0.435 eV, eA = 0 dashed curves, AEDH = 0.835 eV, ea = 0 dotted curves AEDH = 0.435 eV, eA = 0.4eV dot-dash curves, A DH = 0.835 eV, eA = 0.4 eV. The chemical potential fi is constant on each curve and has been chosen to make the model curve pass through one of the experimental points of donor doping near 1017 cm-3, as shown. The solid circles are experimental points for arsenic obtained from Fig. 29 as described in the text. The other points are extrapolations of the phosphorus curves of Fig. 31 to zero depth, as described for Fig. 32, with open circles for the newer data and crosses for the older.

Dopants that donate electrons are termed donors or n-type dopants (e.g. phosphorus atoms in sihcon), since the negatively charged electrons become the majority carrier. By comparison, impurities that accept electrons (boron atoms in silicon), creating holes, ate termed acceptors or p-type dopants, since the positively charged holes become the... 

In Fig. 2.9, we see a moderate downfield shift for the formation of a donor bond upon coordination, almost irrespective of the Lewis acid involved. It is the almost that interests us greatly. We use two phosphanes for comparison, PMe and PPh and note that the downfield shift for PPh upon coordination ranges from A< =21-40ppm, and that for PMOj is in an even narrower band of AJ=46-60ppm. In each case, the actual downfield shift depends on the Lewis base. Defining factors are the geometry around the metal (cis or trans), and the substituents on phosphorus (P or PPh ). Both factors are explainable and will be treated in the respective chapters. 

Deactivating nucleophiles Anomeric effect shows how to activate electrophiles. The opposite side of n o hyperconjugation is that it can decrease donor ability of the lone pair and deactivate the nucleophile. For example, the reactivity of cyclic phosphites where the lone pair of phosphorus is aligned with the acceptor 0-C bonds is drastically decreased in comparison with triethyl phosphite. The bicyclic phosphite was also found to be less donating than PMCj, PPhj, and P(OMe) in Ru(ll) complexes (Figure 11.42). ... 

---