Phosphine bond angle

Whereas the barrier for pyramidal inversion is low for second-row elements, the heavier elements have much higher barriers to inversion. The preferred bonding angle at trivalent phosphorus and sulfur is about 100°, and thus a greater distortion is required to reach a planar transition state. Typical barriers for trisubstituted phosphines are BOSS kcal/mol, whereas for sulfoxides the barriers are about 35-45 kcal/mol. Many phosphines and sulfoxides have been isolated in enantiomerically enriched form, and they undergo racemization by pyramidal inversion only at high temperature. ... 

Phosphine is a coioriess, highiy toxic gas with bond angles of 93.6°. Describe the bonding in PH3. ... 

When bond angles are close to 90°, as in phosphine, it is sensible to describe the bonding using atomic orbitals that point at right angles to one another in other words, the valence p orbitals. 

The dipole moment of tributylpliosphine varies from 1.49 to 2.4 D according to the solvent used. Inductive effects in phosphines have been estimated by comparing the calculated and observed dipole moments, and the apparent dipole moment due to the lone electron pair on phosphorus has been estimated. A method of calculating the hybridization of the phosphorus atom in terms of bond angles is suggested which leads to a linear relationship between hybridization ratio and lone electron pair moment. The difference between experimental and calculated dipole moments for para-substitued arylphosphines, phosphine sulphides, and phosphinimines has been used to estimate mesomeric transfer of electrons to phosphorus. 

The stability of Ni-C02 complexes is related to the basicity of ancillary phosphines and to the P—Ni—P bond angle. For example, it was calculated that the total energy for the complex... 

The structure of dimethylberyllium is similar to that of trimethylaluminum except for the fact that the beryllium compound forms chains, whereas the aluminum compound forms dimers. Dimethylberyllium has the structure shown in Figure 12.3. The bridges involve an orbital on the methyl groups overlapping an orbital (probably best regarded as sp3) on the beryllium atoms to give two-electron three-center bonds. Note, however, that the bond angle Be-C-Be is unusually small. Because beryllium is a Lewis acid, the polymeric [Be(CH3)2] is separated when a Lewis base is added and adducts form. For example, with phosphine the reaction is... 

Imino-fe(phosphine chalcogenide)s can in theory exist in two different tautomeric states an N-H tautomer 41a and a E-H tautomer 41b. However, extensive studies in both solution and the solid state have shown that in all cases (with the exception of some dioxo E = O species) the N-H tautomer predominates.75 Structural studies have revealed the N(PE)2 group in 41a to be planar or close to planar, with P-N-P bond angles in the range 122-133°, indicative of substantial sp2 character at the nitrogen centre. Planarity of the nitrogen is also observed in the anionic dichalcogenoimidodiphosph(in)ates 42. 

Table 4.22. Geometrical and NBO parameters for ammine, phosphine, and carbonyl coordination complexes of Os and Re hydrides, showing bond angles, valence Lewis accuracy (%p ), and metal bond hybrid (Iim) and polarization (%cm2) of oml and omh NBOs...

The values obtained for the P—H bond lengths and H-P-H bond angles by different methods are collected together in Table 1. Calculations on the bond lengths in PH3, PHJ and PH have been made by Banyard and Hake Ab initio SCF—LCAO-MO calculations for the phosphine molecule have been made recently by various workers and the results compared with the experimentally determined physical quantities for the molecule 346,34 )... 

In hydrogen sulfide, phosphine, and the hydrides of their heavier congeners, in which the bonds are nearly normal covalent bonds, the bond angles are observed to be close to 90° (Table 4-1). The values given in the table apply to the deuterium compounds as well as to the protium compounds. 

Also, we can explain on the basis of electron repulsions why the bond angle in phosphine, PH3 (93°), is less than that in ammonia, NH3 (107.3°),... 

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