Pyramidal structure, trigonal

In 62, two zincate ions of different composition, namely [Zn(CCPh)3] 62a and its THF adduct [Zn(CCPh)3(THF)] 62b, co-crystallized (Figure 31). Both, the coordination of only one zincate ion with THF and the trigonal-pyramidal structure of 62b, show that the interaction between zinc and the THF molecule in 62b must be weak. The zinc-carbon bonds in 62a and 62b are 1.967(7) and 2.003(5) A long, respectively. 

The NH3 molecule is generally agreed to have a trigonal pyramidal structure, characterized by three internal parameters d = 101 pm, z0 = 38 pm, a = 68°, and with nitrogen at the apex, over a trigonal array of hydrogen atoms. 

Thus, according to this alternate approach, NH3 belongs to the VSEPR class AX3E. Molecules of this type adopt a trigonal pyramidal structure. 

Cuj-O 1.922(8), Cu2-02 = 1.922(9), Cu3-03 = 1.933(6)). The CO(j ion coordinates to the copper ions along the axis of the trigonal pyramidal structure. This differs from other cases in which C03 coordinates to copper ions along the basal plane of the SQPY (33a,33b,55-58). 

Solid state spectra (Nujol or KBr). bSquare pyramidal structure. Trigonal pyramidal structure. X-ray... 

Phosphine Phosphine (PH3), a colorless, extremely poisonous gas, is the most important hydride of phosphorus. Like NH3, phosphine has a trigonal pyramidal structure and has the group 5A atom in the —3 oxidation state. Unlike NH3, however, its aqueous solutions are neutral, indicating that PH3 is a poor proton acceptor. In accord with the low electronegativity of phosphorus, phosphine is easily oxidized, burning in air to form phosphoric acid ... 

The most common valence states of arsenic are —3, 0, +3, and +5 (Shih, 2005), 86. The —3 valence state forms through the addition of three more electrons to fill the 4p orbital. In the most common form of elemental arsenic (As(0)), which is the rhombohedral or gray form, each arsenic atom equally shares its 4p valence electrons with three neighboring arsenic atoms in a trigonal pyramid structure ((Klein, 2002), 336-337 Figure 2.1). The rhombohedral structure produces two sets of distances between closest arsenic atoms, which are 2.51 and 3.15 A (Baur and Onishi, 1978), 33-A-2. The +3 valence state results when the three electrons in the 4p orbital become more attracted to bonded nonmetals, which under natural conditions are usually sulfur or oxygen. When the electrons in both the 4s and 4p orbitals tend to be associated more with bonded nonmetals (such as oxygen or sulfur), the arsenic atom has a +5 valence state. 

Figure 2.1 The trigonal pyramidal structure of gray elemental arsenic. Each arsenic atom shares its valence electrons with three other arsenic atoms through covalent bonds.

Iminodiacetonitrile HN(CH2CN)2 forms [NiL2Cl2], which from the similarity of its properties to those of [CuL2C12] is assumed to have a similar structure (q.v.). 9S An X-ray structural investigation of Bu N(7t-CpNi)3 (/teff = 1.68 BM) has revealed a trigonal-pyramidal structure (96)499... 

Pt(PPh3)3(S02)]. C6H6 0.067 trigonal-pyramidal structure with Pt—S = 2.399 A. Oxygen atoms of S02 are disordered about the three-fold axis d... 

Inversion is also used to describe the oscillation of the central atom of a trigonal pyramidal structure through the plane formed by the groups attached to this atom. 

U CH(SiMe3)2 3] has a trigonal pyramidal structure, like the corresponding lanthanide alkyls (Section 6.2.1) and also like the isoelectronic amides [M N(SiMe3)2 3] (M = U,... 

Being such a famous performer, the shape and size of the hydronium ion have been determined by NMR and other methods. The HjO ion has a rather flat trigonal-pyramidal structure with the hydrogen at the comers of the pyramid and the oxygen in the middle, as shown in Fig. 4.118. Its structure resembles that of the ammonia molecule. 

The first secondary stibine, the structure of which was elucidated by X-ray diffraction, was MeSjSbH . This hydride is exceptionally stable and possesses (as expected) a trigonal pyramidal structure (CSbC, 101.7°). Reaction according to equation 26 formed the planar (X-ray) Cu2Sb2 heterocycle containing essentially identical Cu-Sb distances of 270 pm in agreement with a real Cu-Sb single bond (sum of covalent radii = 268 pm) . 

---