Open ligand

Zinc ethanoate behaves similarly to mercury(II) ethanoate on reaction with 2-(2-pyridyl)benzothiazole and gives complexes of a ring-opened ligand.928... 

There are two major classes of ion channels defined by the way the channel opens ligand-gated and voltage-gated. Ligand-gated ion channels... 

Figure 2.3 Orientations of ligands and d orbitals of a transition metal ion in octahedral coordination, (a) Orientation of ligands with respect to the cartesian axes (b) the x-y plane of a transition metal ion in an octahedral crystal field. The orbital is cross-hatched the dx2 y2 orbital is open ligands are black circles.

Acetylcholine receptors on the motor end plate bind acetylcholine, which opens ligand-gated ion channels. This allows movement of Na into and K out of the myocyte, producing a local depolarisation of the motor end plate (the end-plate potential). 

Even closed Even open Even open Ligands... 

Rule 3 considers the regiochemistry of attack of the nucleophile. For even, open ligands, the nucleophile tends to attack at the terminal position of the ligand. Consider 1,3-butadiene as a typical example. The LUMO of butadiene, ( 3),49 has larger lobes at the termini of the orbital than in the middle (Figure 8-6). The incoming nucleophile (if it is reasonably soft) will be attracted to that part of the orbital with the biggest lobe.50... 

The picture is more complicated when we apply Rule 3 to odd, open ligands. Attack may occur at the termini or internal positions depending on the electron richness of the attached metal fragment. Usually attack occurs at the terminal carbons of irf-allyl ligands, but for relatively electron-rich metal complexes such as [Cp2Mo(in3-allyl)]+ (equation 8.3551) and [Cp (PMe3)Rh(iq3-allyl)]+ (equation 8.3652), addition occurs at C-2 to form metallacyclic products. 

The kinetic analysis demonstrated an unusual dependence of the cyclization rate on the rare-earth metal ion size, with maximum turnover rates observed for the medium-sized yttrium and slower rates for the larger lanthanum and smaller lutetium [144]. Similar to aminoalkynes, catalysts with more open ligand frameworks are less active. DFT calculations indicate that protonolysis is the ratedetermining step of the process [113], although this notion is contrary to some experimental observations [143,144]. 

In 2009, Xiao employed a half sandwich Cp lr(l 11) complex with different chiral monosulfonated OPEN ligands (Figure 7.2), earlier developed for imine reduction by the same group, in combination with a BINOL based chiral phosphate counteranion (TRIP anion), to reductively aminate 24 acetophenone derivatives (1.2 equiv) with p anisidine (limiting reagent) under the conditions of 1.0 mol% of the indicated Ir catalyst (Table 7.1), 5 bar (73 psi) H2, toluene, 35 °C, and 15 24h [14]. 

Uniiganded Closed Unliganded Open Liganded Open Llgonded Closed... 

Fig. 3. The active site of K. aerogenes urease. The two Ni ion have different coordinations. Nil has an open ligand site that may be instrumental in catalysis (see Fig. 9). This figure was adapted from [16]...

The regioselectivity of olefin insertion varies with the complex used in the reaction [27, 34]. In the hydrosilylation of a monosubstituted olefin, the use of complexes with larger metals and more open ligands provide increased yields of the product derived from reversed ( 2,1 ) insertion (Eq. 16). These results reveal that a variety of complexes give excellent selectivity for terminal insertion, but the conditions to elevate the amount of 2,1 insertion remain elusive. 

The reduced cytochrome P450 has been determined to be high spin in the case of the camphor-5-exo-monooxygenase Its coordination sphere is probably 5-coor-dinated, but there is no definite proof that the mercaptide ligand is still in the fifth position. Like all ferrous hemoproteins with an open ligand position cytochrome P450 reacts rapidly and with a value of about 10 M with dioxygen to form... 

V. To know the best conformation, open ligand.dlg with WordPad and search the RMSD table. The conformation with least-binding energy is ranked first which is most of the times the best-fitting conformation. 

Examples of the DGM rules at work—nucleophilic attack occurs preferentially at even hapticity and open ligands. 

Nucieophiiic addition L M(Y) DGM rules (even, open) ligands M in high OS acceptor... 

Rule 2. Open ligands react before closed. 

The molecular recognition of these barrels has been broadly studied and is the basis of most of their applications. For example, lipocaline mimics based on j6-barrels that are able to host carotenoids in water have been prepared. In a similar way, pores have also been designed that open (ligand gating) and close (blockage) in response to chemical stimulation. A clever modification allowed the development of synthetic ion channels with a rigid-rod architecture that opens in response to charge-transfer... 

Open ligands are attacked preferably to cyclic ligands. 

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