Coordinates coordinate triples

Since activation of the N-H bond of PhNHj by Ru3(CO)i2 has been reported to take place under similar conditions [306], it has been proposed that the reaction mechanism involves (i) generation of an anUido ruthenium hydride, (ii) coordination of the alkyne, (iii) intramolecular nucleophilic attack of the nitrogen lone pair on the coordinated triple bond, and (iv) reductive ehmination of the enamine with regeneration of the active Ru(0) center [305]. 

In the case of acetylenic amides, the carbonyl oxygen atom turned out to be nucleoplilic enough to directly attack the coordinated triple bond, owing to the conjugation with the amide moiety. Thus, cGa-dialkyl substituted 2-ynylamides smoothly underwent oxidative cyclization-alkoxycarbonylation to afford new oxazoline derivatives in good yields (Eq. 44) [102,113]. 

KINETIC ISOTOPE EEEECT REACTION COORDINATE DIAGRAM Triose-phosphate isomerase energetics, REACTION COORDINATE DIAGRAM TRIPLE-COMPETITIVE METHOD TRIPLET STATE FLUORESCENCE TRIPLET-TRIPLET ANNIHILATION ANNIHILATION... 

Coordinates of molecules may be represented in a global or in an internal coordinate system. In a global coordinate system each atom is defined with a triplet of numbers. These might be the three distances x,, y,-, z, in a crystal coordinate system defined by the three vectors a, b, c and the three angles a, / , y or by a, b, c, a, P, y with dimensions of 1,1,1,90°, 90°, 90° in a cartesian, i. e. an orthonormalized coordinate system. Other common global coordinate systems are cylindrical coordinates (Fig. 3.1) with the coordinate triples r, 6, z and spherical coordinates (Fig. 3.2) with the triples p, 9, . 

The ketenimine complex is unusual in that angle y for the complex is 11.9(10)° and the average S is 174°. These angles are indicative of a coordinated triple bond, rather than the expected double bond. This seemingly anomalous result can be rationalized on the basis of a large contribution of resonance form B to the structure of the ketenimine. This... 

A paramagnetic vanadium-benzyne complex (112) has been synthesized by thermolysis of CpVPh2(PMe3)2 (111) at 50°C tia = 3-4 h) [Eq. (18)].64 An X-ray crystal structure was reported for 112. Bond lengths for the benzyne ligand are given in Table III. The C1-C2 distance [1.368(5) A] is similar to those in the other structurally characterized benzyne complexes. A band in the IR spectrum of 112 at 1547 cm"1 was assigned to the coordinated triple bond. 

Distances and angles. Structures can be presented in an internal coordinate system (symmetry adapted coordinates used in spectroscopy or Z-matrices, that is interatomic distances, three center angles and four center angles) instead of a global coordinate system (coordinate triples, for example cartesian, crystal, cylindrical or spherical coordinates). 

Scheme 35 Yet another access to ring-annelated cyclohexadienes involving cyclization by intramolecular nucleophilic attack on a palladium-coordinated triple bond [115]...

The three-dimensional model of cephalosporin (Figure 6.38, upper left) is based on Cartesian coordinates (xyz-triples) for each atom. It is usually calculated by force-field methods that take the repulsion of the atoms magnetic fields into account. 

UCBHKK (solid, 12 coordinate, 4 triple hydrogen bridge bonds)... 

The next step is to come up with a bookkeeping scheme to keep all the (x, y, z) coordinate information connected to the identity of each atom. The easiest approach may be to write the (x, y, z) value as a coordinate triple on the same pieces of paper used for the two-dimensional sketch of the biopolymer, right next to each atom. This associates the (x, y, z) value with the atom it is attached to. 

Definition (The barycenter of a molecule) Assume that the molecule is placed in 3D space and that the coordinate triples of the atoms are the triples... 

The corresponding coordinate triples y, now considered as points in 3D space, describe a new placement obtained by a translation of the molecule by x. This new placement of the molecule has its barycenter at the origin. For this reason we call such a placement a barycentricplacement. 

Hydrothiolation of 1-alkynylphosphines was catalyzed by P(OAc)2 in EtOH and gave Z-l-phosphino-2-thio-l-alkene as product (Scheme 3.87) [156]. Surprisingly, the addition reaction took place in the anti-fashion, which probably means an external nucleophilic attack on the coordinated triple bond as a key-step instead of the alkyne insertion observed in the other examples. 

Kim SH, Cha EJ, Lee KM, Kim HJ, Kwon OS, Lee J. Simultaneous ionization and analysis of 84 anabolic androgenic steroids in human urine using liquid ehromatography-silver ion coordination ionspray/triple-quadrupole mass spectrometry. Drug Test Anal. 2014 6 1174-85. 

Corresponding relations for the other diagonal components can be obtained by cyclic permutations of the coordinate triple xyz to yzx or zxy. Since the quadrupole moment of a polar molecule depends on the origin of the coordinate system it is important to remember that the centre of nuclear masses is automatically chosen as the origin in Eq. (6.41). Similar to the previously derived relations between the rotational g tensor and other molecular properties, Eqs. (6.30) and (6.38), one has to take care of vibrational corrections to the properties in Eq. (6.41), when it is applied to measured rotational g tensors and magnetizabilities. 

Under oxidative conditions, acyclic [75a,b] and cyclic [75c] 4-yn-l-ols react via a cyclization-methoxycarbonylation pathway to afford ( )-cyclic-P-alkoxyacrylates 2E-[(methoxycarbonyl)methylene]tetrahydrofurans in good yields under mild conditions (Equations 10.37 and 10.38). The stereochemical outcome is entirely consistent with a reaction initiated by intramolecular nucleophilic attack of the hydroxy group on the palladium-coordinated triple bond to generate a vinylpalladiumiodide intermediate that undergoes methoxycarbonylation to afford the P-alkoxyacrylate. The ketopyranose subunit can also be constructed via a palladium-catalyzed oxidative cyclocarbonylation of substituted 5-yn-l-ols, which occurs with excellent stereose-... 

A. Reactions in Which the Coordinated Triple Bond Is Unaffected... 

B. Reactions Which Occur at the Coordinated Triple Bond... 

Alkyne complexes of low oxidation state metals react with electrophiles generally to produce alkene derivatives resulting from addition of the electrophilic species to the coordinated triple bond. These reactions often proceed by way of (x-vinyl-metal derivatives, and in several cases such intermediates have been isolated. The vinyl complexes, in turn, may be cleaved in a subsequent reaction to afford substituted alkenes [Eq. (29)]. 

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