Secondary bonding complexes

S.2.2.2. Composite adherends. Composite adherends are bonded in both the cured and uncured states. Wherever possible the adhesive and all adherends are cured simultaneously to avoid the added cost of additional autoclave cure cycles. In many cases this is not practical due to part size and complexity. Cured parts can be bonded to uncured parts, which is known as cobonding, and fully cured parts can be bonded together, which is known as secondary bonding. Adhesives for composites are formulated to be compatible with matrix resins in either cured or uncured states. 

The reaction is generally believed to proceed via the formation of ionic acylam-monium intermediate compounds (Reaction 1, Scheme 2.27). The equilibrium constant of the acylammonium formation depends mostly on steric and resonance factors, while the basicity of the tertiary amine seems to play a secondary role.297 In die case of the less basic compounds, such as acidic phenols, and of strong tertiary amines, such as Uialkylamines, the reaction has been reported to proceed through a general base mechanism via the formation of hydroxy-amine H-bonded complexes (Reaction 2, Scheme 2.27).297... 

With simple Hg thiolates the structures of bis(ethanethiolato)mercury Hg(SEt)2321 and of the cysteamine complex [Hg S(CH2)2NH3 2]Cl2322 have reference character, as only weak or no secondary bonds are present, and therefore the central S—Hg—S entities can be considered to be unperturbed. In mercury bis(tri-t-butoxysilanethiolate) Hg[SSi(o-t-Bu)3], with a strictly linear S—Hg—S unit, two weak intramolecular O II g interactions obviously do not affect the bonding in this unit.323... 

From Carbyne Complexes. Addition of HC1 across the metal-carbon triple bonds of Ru and Os d8 arylcarbyne complexes yield stable, neutral secondary alkylidene complexes ... 

The sections below review the coordination chemistry of the most important classes of extractants used commercially. Particular attention is paid to the importance of secondary bonding between extractant components. This facilitates the assembly of ligating packages which match the coordination requirements of particular metal cations or their complexes and enhances both the selectivity and strength of extraction. Flydrogen bonding between ligands—e.g., esters of phosphorus(V) acids (see Section 9.17.4.3)—is particularly prevalent in the hydrocarbon solvents commonly used in industrial processes. 

A wide range of complexes involving acceptors from the p-block, e.g. T1(I), Sn(IY), As(III), Sb(III), Bi(III), Pb(II) c., 13 148 has also been characterized (Figure 7). These species display a surprisingly diverse structural chemistry, in which secondary bonding plays a significant role in determining the final structure. 

Monodentate (monometallic monoconnective) phosphor-1,1-dithiolato ligands are rare. Bidentate (monometallic biconnective) form chelate rings and three sub-types can be distinguished according to the degree of asymmetry (Scheme 2). The most asymmetric type (anisobidentate) occurs when a covalent bond is associated with a secondary bond this takes place mostly in main-group metal complexes. The second type is rare and is the result of the association between a covalent and a dative coordinate bond. The symmetric bidentate bonding (isobidentate) is found mainly in transition metal complexes. 

The structural chemistry of some metal dithiocarbamates, i.e. systematics, coordination modes, crystal packing, and supramolecular self-assembly patterns of nickel, zinc, cadmium, mercury,363 organotin,364 and tellurium,365 366 complexes has been thoroughly analyzed and discussed in detail. Supramolecular self-assembly frequently occurs in non-transition heavier soft metal dithiocarbamates. Thus, lead(II),367 bismuth(III)368 zinc,369 cadmium,370 and (organo)mercury371 dithiocarbamates are associated through M- S secondary bonds, to form either dimeric supermolecules or chain-like supramolecular arrays. The arsenic(III)372 and antimony(III)373 dithiocarbamates are... 

Nickel(II) dithiocarbamates, Ni(S2CNRR )2, are monomeric, square planar complexes. A less common dinuclear complex is the thiolato bridged [Ni(S2CNHMe)(p-SMe)]2, in which the dimers are self-assembled into tetra-meric supermolecules through weak axial Ni- S secondary bonds.397... 

As an example he referred to "psuedo-high molecular weight" inorganic complexes. In a similar fashion, Pringsheim discussed the nature of inulin and other polysaccharides. Bergmann and Pringsheim cited the work of P. Karrer, K. Hess, and R. Pummerer and referred to primary and secondary bonding as proposed by Werner. 

Phenylarsine bis (diethyl dithiocarbamate), secondary bonding by, 15 30-31 Phenylazidosilanes, properties, 9 141 (Phenylazo)acetaldoxime complexes, osmium, 37 270... 

Pyridinium tetrachloroantimonite, secondary bonding by, 15 32-33 p-Pyrimidine complexes, osmium, 37 307 2-Pyrimidinethiolato complexes, osmium, 37 295-296... 

Selenotrithionates, 2 256 Selenous acid, secondary bonding by, 15 19 Self-assembling metal complexes, 46 174-175, xee also Supramolecular copper (l)/silver (I) complexes... 

Jorgensen WL, Pranata J. Importance of secondary interactions in triply hydrogen bonded complexes guanine-cytosine vs uracil-2,6-diaminopvridine. J Am Chem Soc 1990 12 2008-2010. 

Examples of the various helical forms found in nature are the single helix (RNA), the double helix (DNA), the triple helix (collagen fibrils), and complex multiple helices (myosin, F-actin). Generally, these single and double helices are fairly readily soluble in dilute aqueous salt solution. The triple and complex helices are soluble only if the secondary bonds are broken. 

A secondary bond , as defined by Alcock [6-8], is an interaction between two atoms characterized by a distance longer than the sum of the covalent radii but shorter than the sum of the van der Waals radii of the corresponding atoms. Such secondary interactions are weaker than normal covalent or dative bonds, but strong enough to connect individual molecules and to modify the coordination geometry of the atoms involved. They are often present in a crystal, thus resulting in self-assembled supermolecules or supramolecular architectures. For gold complexes,... 

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