Five‐Coordinated Structures

Holmes, Robert R.

doi:10.1002/9780470166338.ch2

Cited by 126 publications

(8 citation statements)

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“…The pseudorotation proceeds by the initial trigonal bipyramid (TBP) passing through a square pyramid (SP) to a rearranged TBP. The X-ray results have shown that anionic five-coordinated silicon derivatives are nonrigid and display progressive distortions between the TBP and SP. − The second one, an alternative retention mechanism (Scheme b) proposed by Corriu, does not require a pseudorotation step. In our study, it is found that the S N 2(Si) reactions with retention of configuration also have a double-well potential energy surface (PES).…”

Section: Introductionmentioning

confidence: 99%

“…The S N 2 reactions at silicon (S N 2(Si)) have been investigated in both experimental work − and theoretical calculations. − For an S N 2(Si) reaction with retention of configuration, previous studies have proposed two possible retention mechanisms. The first one, illustrated in Scheme a, is the same mechanism as that for the retention mechanism in nucleophilic substitution reactions of phosphorus. , It involves axial entry and axial departure accompanied by Berry pseudorotation of the initially formed five-coordinate activated state.…”

Section: Introductionmentioning

confidence: 99%

“…The S N 2 reactions at silicon (S N 2(Si)) have been investigated in both experimental work [14][15][16][17][18][19] and theoretical calculations. [20][21][22][23][24][25][26] For an S N 2(Si) reaction with retention of configuration, previous studies have proposed two possible retention mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Analysis of Gas-Phase Front-Side Attack Identity S_N2(C) and S_N2(Si) Reactions with Retention of Configuration

2009

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Gas-phase front-side attack identity S(N)2(C) and S(N)2(Si) reactions, CH(3)X1 + X2(-) --> CH(3)X2 + X1(-) and SiH(3)X1 + X2(-) --> SiH(3)X2 + X1(-) (X = F, Cl), are investigated by the ab initio method and molecular face (MF) theory. The computations have been performed at the CCSD(T)/aug-cc-pVTZ//MP2/6-311++G(3df,3pd) and CISD/aug-cc-pVDZ levels. Front-side attack identity S(N)2 reactions for both SiH(3)X and CH(3)X have double-well potential energy surfaces (PESs), but their transition-state positions are different relative to the positions of reactants and products: it is lower for SiH(3)X, and it is higher for CH(3)X. The minimum energy path for an S(N)2(Si) reaction with retention of configuration proceeds from a stable pentacoordinated anion intermediate of C(s) symmetry (TBP) via a C(s) transition state (SP) to a complementary pentacoordinated intermediate (TBP) and finally up to separate products. Berry pseudorotation has been observed in the front-side attack identity S(N)2(Si) reactions with F(-) and Cl(-) along the intrinsic reaction coordinate (IRC) routes. In addition, the geometrical transformations of front-side attack identity S(N)2(C) and S(N)2(Si) reactions based on the IRC calculations at the MP2/6-311++G(3df, 3pd) level of theory are described compared with those of corresponding back-side attack reactions. The difference between front-side attack identity S(N)2(C) and S(N)2(Si) reactions has been demonstrated. In MF theory, the potential acting on an electron in a molecule (PAEM) is an important quantity; in particular, its D(pb) can measure the strength of a chemical bond in a molecule. It is found that the difference between D(pb) values of reactant and transition state may be related to the activation energy for front-side and back-side attack S(N)2(C) and S(N)2(Si) reactions, and the D(pb) curves along the IRC routes have features similar to those of the potential energy profiles for all of the back-side attack S(N)2 reactions and front-side attack S(N)2(Si) reaction with F(-). Furthermore, according to the MF theory, the spatial dynamic changing features of the molecular shapes and the face electron density are vividly depicted for the course of the reactions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Theoretical Analysis of Gas-Phase Front-Side Attack Identity S_N2(C) and S_N2(Si) Reactions with Retention of Configuration

2009

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“…The coordination sphere around the central atom is constructed by two molecules of PPh 3 ,t wo chlorido and one nitrido ligand. The resulting coordination polyhedron is square-pyramidal but shows ad istortion by 39.2°to-wards at rigonalb ipyramid on the Berry pseudorotation coordinate [5]. The Re-N bond length is found at 1.648(3) Å which is longer than the value of 1.60 Åreported for the structure determination at room temperature without localized hydrogen atoms [3].…”

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confidence: 58%

Redetermination of the crystal structure of nitridodichlorido bis(triphenylphosphane) rhenium(V), at 200 K – Localization of hydrogen atoms, C36H30Cl2NP2Re

Schoultz

Gerber

Hosten

et al. 2015

Zeitschrift Für Kristallographie - New Crystal Structures

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C 36 H 30 Cl 2 NP 2 Re,monoclinic, I2/a (no.15), a =15.5631(4)Å, b=9.5180(3) Å, c =22.0872(9)Å,b=103.237(1)°, V =3184.9 Å 3 , Z =4,R gt (F) =0.0203, wR ref (F 2 ) =0.0419, T =200 K. Source of materialThec ompound has been already reported [3].C rystals suitable for the diffraction study were obtained upon recrystallization of the compound from boiling toluene. Experimental detailsCarbon-bound Hatomswere placed in calculated positions (C-H 0.95 Å) and were included in the refinementinthe riding model approximation, with U iso (H) setto1.2U eq (C). DiscussionNext to cardiovascular diseases, cancer has become one of the main fatal diseases in industrialized countries. Apart from classical surgery,chemo-and radiotherapeutic treatments have entered the arsenal of possible cures for certain types of cancer. All methods, however, suffer from their own set of problematic sideeffects and, as aconsequence, the development of radiopharmaceuticals -combining the advantages of chemotherapy as well as radiation methods while at the sametimeavoiding their unique respectiveundesiredside-effects -has been atopic of research [1,2].T ailoring andf ine-tuning of thee nvisionedr adiopharmaceuticals' properties such as lipophilicityand,inparticular, inertness is of paramountimportancewithrespect to possible future in vivo applications in contemporary medicine and requires sound knowledge about structural parameters of the ligands applied if a more heuristic approach in the synthesis is to triumph over pure trial-and-error as it is encountered in this specific field of coordination chemistry up to the present day. In addition, the spatial requirements of pharmaceuticalsa re of importance as this factor influences on their interaction with enzymatic systems and, as a consequence,t he pathway andr ateo fc onjugation, functionalizationand secretionfrom the body. At thebeginning of astudy aboutnitrido-supported rhenium(V) coordination compounds the starting material was chosen as aversatile starting point for synthesizing the desired compounds. The molecular and crystal structureofthis starting material have been reported once already [3], however, at room temperature and without the localization of hydrogen atoms. As this is an unacceptable starting point for the intended study, the crystal structure of the starting compound was redeterminedtoallow for the direct comparison of metrical parameters.S tructurali nformation is also available for ab oraneadduct of thetitle compound [4].The title compound is apentacoordinated rhenium(V) coordination compound. The asymmetric unit contains half amolecule. The coordination sphere around the central atom is constructed by two molecules of PPh 3 ,t wo chlorido and one nitrido ligand. The resulting coordination polyhedron is square-pyramidal but shows ad istortion by 39.2°to-wards at rigonalb ipyramid on the Berry pseudorotation coordinate [5]. The Re-N bond length is found at 1.648(3) Å which is longer than the value of 1.60 Åreported for the structure determination at room temperature with...

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“…The Sn-C axial distances are not significantly longer than the Sn-C equatorial distances; however, the axial Sn-N bonds are much longer, and the tin atoms are displaced out of the equatorial planes in the direction of the axial carbon atoms. For both molecules, the tbp-sqp Berry pseudorotation pathway as calculated by PLATON [18] on the basis of dihedral angles [19] is 29 % displaced towards a square pyramid (C1 and C28 are the pivot atoms). One of the axial sites is occupied by the nitrogen atom of the ligand; the small bite results in a somewhat longer tin-nitrogen bond as well as a bent nitrogen-tin-nitrogen skeleton.…”

Section: Resultsmentioning

confidence: 99%

Crystal structure of triphenyl(quinolin-8-olato)tin(IV)

Amini

Azadmeher

Khavasi

et al. 2009

Maced. J. Chem. Chem. Eng.

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Triphenyl(quinolin-8-olato)tin crystallizes as two symmetry-independent molecules whose metal atoms both exist in a cis-C3SnNO trigonal bipyramidal coordination polyhedron that is 29 % distorted toward a square pyramid. The crystal structure [orthorhombic Pbcn space group], with a 26.701(2), b 10.3555(6), c 31.322(2) Å; V 8660.5(9) Å3] is refined from 5950 I > 2σ(I) Mo–Kα reflections measured at 200 K to an R-index of 0.050.

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Five‐Coordinated Structures

Cited by 126 publications

References 292 publications

Theoretical Analysis of Gas-Phase Front-Side Attack Identity S_N2(C) and S_N2(Si) Reactions with Retention of Configuration

Theoretical Analysis of Gas-Phase Front-Side Attack Identity S_N2(C) and S_N2(Si) Reactions with Retention of Configuration

Redetermination of the crystal structure of nitridodichlorido bis(triphenylphosphane) rhenium(V), at 200 K – Localization of hydrogen atoms, C36H30Cl2NP2Re

Crystal structure of triphenyl(quinolin-8-olato)tin(IV)

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Five‐Coordinated Structures

Cited by 126 publications

References 292 publications

Theoretical Analysis of Gas-Phase Front-Side Attack Identity SN2(C) and SN2(Si) Reactions with Retention of Configuration

Theoretical Analysis of Gas-Phase Front-Side Attack Identity SN2(C) and SN2(Si) Reactions with Retention of Configuration

Redetermination of the crystal structure of nitridodichlorido bis(triphenylphosphane) rhenium(V), at 200 K – Localization of hydrogen atoms, C36H30Cl2NP2Re

Crystal structure of triphenyl(quinolin-8-olato)tin(IV)

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Theoretical Analysis of Gas-Phase Front-Side Attack Identity S_N2(C) and S_N2(Si) Reactions with Retention of Configuration

Theoretical Analysis of Gas-Phase Front-Side Attack Identity S_N2(C) and S_N2(Si) Reactions with Retention of Configuration