Ammonia bond length

Scheme 7. Enthalpies (kcal mor ) of formation and Si-Si bond cleavage reactions of some coordinated disilenes, calculated at the B3LYP/6-31 l+G //B3LYP/6-31 l+G level values in parentheses refer to the reaction enthalpy of the formation of the coordinated disilene from disilene and 1 or 2 molecules of ammonia bond lengths in pm.

In general, we know bond lengths to within an uncertainty of 0.00.5 A — 0.5 pm. Bond angles are reliably known only to one or twx) degrees, and there arc many instances of more serious angle enxirs. Tn addition to experimental uncertainties and inaccuracies due to the model (lack of coincidence between model and molecule), some models present special problems unique to their geometry. For example, some force fields calculate the ammonia molecule. Nlln to be planar when there is abundant ex p er i m en ta I evidence th at N H is a 11 i g o n a I pyramid. 

The tetramethylammonium salt [Me4N][NSO] is obtained by cation exchange between M[NSO] (M = Rb, Cs) and tetramethylammonium chloride in liquid ammonia. An X-ray structural determination reveals approximately equal bond lengths of 1.43 and 1.44 A for the S-N and S-O bonds, respectively, and a bond angle characteristic bands in the IR spectrum at ca. 1270-1280, 985-1000 and 505-530 cm , corresponding to o(S-N), o(S-O) and (5(NSO), respectively. Ab initio molecular orbital calculations, including a correlation energy correction, indicate that the [NSO] anion is more stable than the isomer [SNO] by at least 9.1 kcal mol . ... 

TABLE 1. Calculated (MM2, MM3 and ab initio) and observed structural parameters for ammonia and methylamines (bond lengths in A, bond angles and tilt angles in degrees, dipole moments in Debye)5,6. Reprinted with permission from Refs. 5 and 6. Copyright (1985, 1990) American Chemical Society... 

The parent compound of all amines, ammonia, has a pyramidal structure with N—H bond lengths of 101.5 pm and H—N—H bond angles of 106.6°. The electronic structure of the ground state may be represented as... 

K3[V(catecholate)3]-1.5H20 has been synthesized from VC13 and catechol in ammonia solution, on adding a solution of KOH. The vanadium is surrounded by six oxygen atoms of catecholate ions the average V—O bond length is 2.013(9) A.256 A tris(o-semiquinone)vanadium(III) complex257 from V(CO)6 and quinone was better formulated as bis(catecholate)(o-semiquinone)vanadium(V).256... 

Cadmium Halides. Cadmium halides show a steadily increasing covalency of the metal—halide bond proceeding from fluoride through to iodide. Bond lengths increase through the series F, 0.197 nm Cl, 0.221 nm Br, 0.237 nm I, 0.255 nm. The fluoride is much less soluble in water than the others (see Table 1) and the Cl, Br, and I compounds dissolve to a significant extent in alcohols, ethers, acetone, and liquid ammonia. Boiling points and... 

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... 

Tetrakis adducts of ammonia, [NiX2(NH3)4] (X = NCS,MS NO2646), have been reported with tetragonal octahedral geometry and Ni—N(NH2) bond lengths in the range 215-210 pm. 

Silver tricyanomethide, AgC(CN)3, has been prepared by precipitation from a mixture of solutions of AgN03 and KC(CN)3. Flat needles could be obtained by recrystallization from dilute ammonia solution. The X-ray structure was undertaken to determine whether a planar three-coordinate species was formed. The results suggested that a distorted layer arrangement existed with three non-equivalent Ag—N bond lengths of between 211 and 226 pm. 

Potential, N-H Bond Length, and Inverse Vibration Frequencies as Functions of Intrinsic Reaction Coordinate for Inversion of the Ammonia Molecule... 

The Co(III)—C bond in the natural coenzymes is resistant to cleavage in protic solvents. However, the bond length [20] is similar to that in models. Indeed, there appear to be no special corrin ring electronic properties necessary for such water-stable Co—C bonds even Co(III)—CH3 compounds with classical ligands such as ammonia or ethylenediamine have now been discovered [21], Although such non-Bi2-related systems are outside the scope of this review, I believe that the main reason that few such compounds are known lies in the paucity of synthetic routes. Since the Co—C bond, once formed, is relatively inert, such compounds could be used for multiple types of applications such as in molecular assemblies or devices [22], The natural compounds and some models are photosensitive, however [23]. It is this photosensitivity that delayed the discovery of the coenzymes, leading instead to the isolation and characterization of the vitamin [1]. 

Very recently, various DHB complexes were analyzed [39].12 The complexes of ammonia and hydronium ions were included in this analysis, in addition to the complexes with acetylene and methane, and their derivatives. Generally, in such complexes, lithium hydride and berylium hydride (and its fluorine derivative) act as the Lewis bases (proton acceptors) while hydronium ion, ammonia ion, methane, acetylene, and their simple derivatives act as the proton donors. Therefore, it was possible to investigate the wide spectrum of DHB interactions, starting from those that possess the covalent character and extending to the systems that are difficult to classify as DHBs (since they rather possess the characteristics of the van der Waals interactions). Figure 12.8 displays the relationship between H—H distance and the electron density at H—H BCP.13 One can observe the H—H distances close to 1 A, (as for the covalent bond lengths) and also the distances of about 2.2—2.5 A, typical for the van der Waals contacts. This also holds for the pc-values - of the order of 0.1 a.u. as for the covalent bonds and much smaller values as for the HBs and weaker interactions. 

Alkilidine tantalum complexes have also been utilized for the preparation of ni-trido Tav. Reaction of ammonia with 31 or 32 afforded nitride 33 in moderate yields [14]. The structure of 33 has been determined by single-crystal X-ray crystallography and shown to consist of a pentameric complex, as depicted in Eq. (9). All of the Ta-N bond lengths are equivalent (2.00 A), suggesting a structure with extensive delocalization of the multiple bonds. 

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