Boron trifluoride orbital structure

In this case, there are three equivalent hybrid orbitals, each called sp (trigonal hybridization). This method of designating hybrid orbitals is perhaps unfortunate since nonhybrid orbitals are designated by single letters, but it must be kept in mind that each of the three orbitals is called sp. These orbitals are shown in Figure 1.4. The three axes are all in one plane and point to the comers of an equilateral triangle. This accords with the known structure of boron trifluoride (BF3), a planar molecule with angles of 120°. 

Such a bond, in which the donor molecule (or anion) provides both bonding electrons and the acceptor cation provides the empty orbital, is called a coordinate or dative bond. The resulting aggregation is called a complex. Actually, any molecule with an empty orbital in its valence shell, such as the gas boron trifluoride, can in principle act as an electron pair acceptor, and indeed BF3 reacts with ammonia (which has a lone pair, NH3) to form a complex H3N ->BF3. Our concern here, however, is with metal cations, and these usually form complexes with from 2 to 12 donor molecules at once, depending on the sizes and electronic structures of the cation and donor molecules. The bound donor molecules are called ligands (from the Latin ligare, to bind), and the acceptor and donor species may be regarded as Lewis acids and Lewis bases, respectively. 

There are some molecules in which the fourth orbital of boron is used for formation of another bond and is not available to permit double-bond character to be assumed by the B—X bonds. In these molecides the bond lengths should approximate the values calculated for B—X single bonds (Table 9-1 column 2). An example is ammonia-boron trifluoride, with the structure... 

Boron trifluoride has a trigonal-planar structure. Formulate the bonding in terms of molecular orbitals for the Dsjj symmetry. In addition, construct wave functions for three equivalent sp2 hybrid orbitals, using the 2px, 2p, and 2s boron valence orbitals, which may be used to form three localized bonds with the three fluorines. Compare and contrast the molecular-orbital and the hybrid-orbital descriptions. 

Boron is a group IIIA element. Open the molecular model for boron trifluoride from the 3D Molecular Models section of the book s website. Near the boron atom, above and below the plane of the atoms in BF3, are two relatively large lobes. Considering the position of boron in the periodic table and the three-dimensional and electronic structure of BF3, what type of orbital does this lobe represent Is it a hybridized orbital or not ... 

Boron trifluoride has a trigonal-planar structure, with all F——F bond angles 120°. Boron has Is and 2 orbitals that bond with the fluorine Is and Ip orbitals. A convenient coordinate system for a discussion of bonding in BFj is shown in Fig. 4-1. 

The highest occupied molecular orbital (HOMO) of ammonia, where the nonbonding pair resides, is shown by red and blue lobes in its structure. When the reaction occurs, the electron density from the HOMO of ammonia is transferred to the LUMO of boron trifluoride. This interaction... 

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