B—P Bonds

Compounds containing B—P Bonds.—CNDO/2 calculations on Me3P,BH3 lead to a minimum energy in the staggered conformation, with rotational barriers about the P—B and P—C bonds of 4.09, 3.83 kcal mol-1, respectively.180 

A similar calculation for H3B—P(NH2)3 suggests that there is little it-bonding in the P—B bond.181 

Detailed studies have been made on the vibrational spectra of F3P—BH3 and F3P—BD3.18Z A force constant of 2.46 mdyn A-1 was calculated for the P—B bond stretching, while assignments of 224 cm-1 and 167 cm-1 were made for the torsional modes of the H and D compounds, respectively. These are consistent with barriers to rotation of 4.15(H), 4.31(D) kcal mol-1. 

and Raman spectra of H3P,BX3 and D3P,BX3 (X = Cl, Br, or I) have been reported and assigned.183 A normal-co-ordinate analysis, (modified Urey-Bradley force field) confirmed the assignments. All the adducts gave a best frequency fit for an assumed value for the HPH bond angle of ca. 105—106°. 

The reaction of PMe2Cl+B2H6 yields the new adduct ClMe2P-BH3.185 A complete vibrational assignment has been proposed for this, and some H and nB n.m.r. data have also been reported. 

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B-C bonds, 3, 97 B-N bonds, 3, 97 B-O bonds, 3,94 B-P bonds, 3, 97 B-Si bonds, 3, 97 oxo acid anion complexes, 3, 96 Borates, alkoxo-, 3, 94 Borates, amidotrihydro-, 3,92 Borates, aryloxo-, 3, 94 Borates, carboxylato-, 3,96 Borates, catechol, 3,95 Borates, chlorosulfato-, 3,97 Borates, dicarboxylato-, 3,96 Borates, dipyrazol-l-yl-, 3, 92 Borates, halogeno-, 3,92 Borates, halogenohydro-, 3,90 Borates, hydro-, 3,90 Borates, hydrohydroxo-, 3,90 Borates, hydropyrazol-l-yl-, 3, 92 Borates, hydroxo-, 3,94 Borates, hydroxycarboxylato-, 3,96 Borates, inositol, 3, 95 Borates, monoalkyl-, 3, 92 Borates, monophosphido-, 3, 92 Borates, peroxohydroxo-, 3, 94 Borates, polyol, 3, 95 Borates, pyrrol-l-yl-, 3, 92 Borates, sulfato-, 3, 97 Borates, tetrabromo-, 3, 92 Borates, tetrachloro-, 3, 92 Borates, tetrafluoro-, 3, 92 minerals, 6, 847 Borates, tetrahalogeno-mixed, 3, 93 nB NMR, 3, 92 Borates, tetraiodo-, 3, 92 Borates, tetranitrato-, 3, 96 Borates, tetraperchlorato-, 3, 97 Borates, tripyrazol-l-yl-, 3, 92 Borax, 3,101 Borazines... 

Adducts of secondary phosphines have also been studied in the context of MO VCD precursors,29 as well as the dehydrocoupling of borane and phosphines to form B-P bond-based polymers.158 Low to medium molecular weight poly(phenylphosphino-boranes) were isolated in the B(C6F5)3 catalyzed dehydrocoupling of PhPH2 BH3. 

Table 2. The observed B-P distances vary over a small range of 2.07-2.14A. However, compound 88 has a longer B-P bond (2.07 A) than does its six-membered ring analog (2.02 A) <1997JOM323>. Like C3BN rings, the formation of C3BP rings is sensitive to the substituents on boron. Thus compound 101 which is the bis(methoxy) derivative of 90 fails to form a B-P ring <1997ZFA1093>.

The formation of heterocycles 25-35, which are internal Lewis base-borane complexes, is dependent on the borane substituents. An increase in the Lewis acidity of the borane can result in ring formation. For example, bis(methoxy)borane 101 has no B-P bond, but treatment with boron trichloride results in the formation of 1,2-phosphoniaboratole 156, presumably via 155 (Scheme 12) <1997ZFA1093>. 

The chemistry of inorganic polymers containing B—and B— P bonds, other than the well-known cyclotriborazenes, has been reviewed. 

A dipole moment of 4.00(3) D was calculated and the barrier to internal rotation assessed at 2.47(5) kcal mol. The relationship between B—P bond length and the stability of the borane adduct is also discussed. 

The linear [BP2] " anion (9.62a) is present in K3PB2, which can be formed from the elements at high temperatures. Other compounds which have been shown to contain a B=P bond are (9.62b,c) as well as the anion in Figure 9.1 [27,31]. 

Some structural anomalies of the H3B adducts of F3P and R3P (R = H or alkyl) are also of interest. Microwave studies by Kucdcowski and lide (14) on F3PBH3 showed that the B-P bond is the shortest yet recorded for complexes containing 4-coordinate boron and phosphorus (1.836 . 012... 

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