Crystal structure of the pyridine–diiodine (1/1) adduct

Tuikka, Matti; Haukka, Matti

doi:10.1107/s2056989015010518

“…[46] Similarly the iodine IÀ I bond length was found to be 2.810(1) Å, which is much longer than that of free iodine (2.715 Å) in solid-state, and in-line to those previously reported for the analogous pyridine•I 2 halogen-bonded complexes. [46] In addition to structural studies the halogen-bonded complex 6•I 2 was further studied with UV-Vis and fluorescence spectroscopy due to the fascinating photophysical properties ligand 6 has previously revealed upon protonation. [47] In the protonation experiments of 6, [47] the protonation was found to decrease the energy of the placement of the pyridyl unit out of the plane making the molecular rotation more accessible, as well as change the lowest lying electronic transition, which resulted in quenching of the fluorescence.…”

Section: Resultssupporting

confidence: 83%

“…However, whilst attempting to crystallize [6-I-6]I 3 in the presence of excess I 2 , a neutral halogen-bonded complex 6•I 2 was observed, where the I 2 is directly bonded to the ligand's nitrogen atom (Figure 8). For this complex, the NÀ I bond length was found to be similar (2.397(9) [46] Å, R XB = 0.68, Table S3) to other aromatic amine-I 2 complexes. [46] Similarly the iodine IÀ I bond length was found to be 2.810(1) Å, which is much longer than that of free iodine (2.715 Å) in solid-state, and in-line to those previously reported for the analogous pyridine•I 2 halogen-bonded complexes.…”

Section: Resultsmentioning

confidence: 58%

“…For this complex, the NÀ I bond length was found to be similar (2.397(9) [46] Å, R XB = 0.68, Table S3) to other aromatic amine-I 2 complexes. [46] Similarly the iodine IÀ I bond length was found to be 2.810(1) Å, which is much longer than that of free iodine (2.715 Å) in solid-state, and in-line to those previously reported for the analogous pyridine•I 2 halogen-bonded complexes. [46] In addition to structural studies the halogen-bonded complex 6•I 2 was further studied with UV-Vis and fluorescence spectroscopy due to the fascinating photophysical properties ligand 6 has previously revealed upon protonation.…”

Section: Resultsmentioning

confidence: 58%

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Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives

Taipale

¹

,

Siepmann

²

,

Truong

³

2021

Chemistry A European J

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The synthesis of iodine(I) complexes with either benzoimidazole or carbazole-derived sp 2 N-containing Lewis bases is described, as well as their corresponding silver(I) complexes. The addition of elemental iodine to the linear two-coordinate Ag(I) complexes produces iodine(I) complexes with a three-center four-electron (3c-4e) [NÀ IÀ N] + bond. The 1 H and 1 H-15 N HMBC NMR studies unambiguously confirm the formation of the complexes in all cases via the [NÀ AgÀ N] + ![NÀ IÀ N] + cation exchange, with the 15 N NMR chemical shift change between 94 to 111 ppm when compared to the free ligand. The single crystal X-ray crystallographic studies on eight I + complexes revealed highly symmetrical [NÀ IÀ N] + bonds with IÀ N bond distances of 2.21-2.26 Å and NÀ IÀ N angles of 177-180°, whilst some of the corresponding Ag + complexes showed a clear deviation from linearity with NÀ AgÀ N angles of ca. 150°and AgÀ N bond distances of 2.09-2.18 Å.

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“…Hypervalent bonding (more specifically: 3c-4e bonding) in the I2-pyridine-adduct. The experimental I-I bond length shows weakening compared to free I2 but to a lesser extent than in I3 - 22. …”

mentioning

confidence: 73%

Covalent d-Block Organometallics: Teaching Lewis Structures and sd/sd2 Hybridization Gives Students Additional Explanations and Powerful Predictive Tools

Fekl

¹

2021

Preprint

0

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Despite tremendous efforts by instructors and textbook authors, students find it difficult to develop useful chemical intuitions about preferred structures, structural trends, and properties of even the most common d-block element organometallic species, that is d6, d8, and d10 systems. A full molecular orbital analysis of a transition metal species is not always feasible or desirable, and crystal field theory, while generally useful, is often too simplistic and limited. It would be helpful to give students of organometallic chemistry an additional toolkit that helps them to understand d-block compounds, in particular highly covalent ones. It is well known in the research literature in organometallic chemistry that hybridization arguments involving s and d orbitals (such as sd and sd2 hybridization for d8 and d6 systems, respectively) provides useful insight. However, this knowledge is much underused in undergraduate teaching and not taught in undergraduate textbooks. The purpose of this article is to make descriptions of bonding that are based on s,d-hybridized orbitals more accessible in a way that is directly useful for undergraduate teaching. Geometries of unusual low-coordinate structures can be successfully predicted. An in-depth physical explanation for the trans-influence, the weakening of a bond due to a strong bond trans to it, is provided. A clear explanation is given for why the cis isomer normally more stable than the trans isomer in square-planar d8 complexes of the type MR2L2 (R = alkyl/aryl, L = relatively weakly bonded neutral ligand). Similarly, the relative stability of fac versus mer isomers in octahedral d6 complexes of the type MR3L3 is explained. Relevant to catalysis, the method explains why strongly donating ligands do not always facilitate oxidative addition and why 12-electron and 14-electron Pd(0) species are thermodynamically much more accessible than one might expect. The method capitalizes on 1st year knowledge such as the ability to write Lewis structures and to use hybridization arguments. It also ties into the upper-year experience, including graduate school, where covalent d-block complexes may be encountered in research and where the hybridization schemes described here naturally emerge from using the NBO formalism. It is discussed where the method might fit into the inorganic curriculum.<br>

show abstract

“…Hypervalent bonding (more specifically: 3c-4e bonding) in the I2-pyridine-adduct. The experimental I-I bond length shows weakening compared to free I2 but to a lesser extent than in I3 - 22. 355…”

mentioning

confidence: 91%

Covalent d-Block Organometallics: Teaching Lewis Structures and sd/sd2 Hybridization Gives Students Additional Explanations and Powerful Predictive Tools

Fekl

¹

2021

Preprint

0

View full text Add to dashboard Cite

Despite tremendous efforts by instructors and textbook authors, students find it difficult to develop useful chemical intuitions about preferred structures, structural trends, and properties of even the most common d-block element organometallic species, that is d6, d8, and d10 systems. A full molecular orbital analysis of a transition metal species is not always feasible or desirable, and crystal field theory, while generally useful, is often too simplistic and limited. It would be helpful to give students of organometallic chemistry an additional toolkit that helps them to understand d-block compounds, in particular highly covalent ones. It is well known in the research literature in organometallic chemistry that hybridization arguments involving s and d orbitals (such as sd and sd2 hybridization for d8 and d6 systems, respectively) provides useful insight. However, this knowledge is much underused in undergraduate teaching and not taught in undergraduate textbooks. The purpose of this article is to make descriptions of bonding that are based on s,d-hybridized orbitals more accessible in a way that is directly useful for undergraduate teaching. Geometries of unusual low-coordinate structures can be successfully predicted. An in-depth physical explanation for the trans-influence, the weakening of a bond due to a strong bond trans to it, is provided. A clear explanation is given for why the cis isomer normally more stable than the trans isomer in square-planar d8 complexes of the type MR2L2 (R = alkyl/aryl, L = relatively weakly bonded neutral ligand). Similarly, the relative stability of fac versus mer isomers in octahedral d6 complexes of the type MR3L3 is explained. Relevant to catalysis, the method explains why strongly donating ligands do not always facilitate oxidative addition and why 12-electron and 14-electron Pd(0) species are thermodynamically much more accessible than one might expect. The method capitalizes on 1st year knowledge such as the ability to write Lewis structures and to use hybridization arguments. It also ties into the upper-year experience, including graduate school, where covalent d-block complexes may be encountered in research and where the hybridization schemes described here naturally emerge from using the NBO formalism. It is discussed where the method might fit into the inorganic curriculum.<br>

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Crystal structure of the pyridine–diiodine (1/1) adduct

Abstract: In the title adduct, C5H5N·I2, the N—I distance [2.424 (8) Å] is remarkably shorter than the sum of the van der Waals radii. The line through the I atoms forms an angle of 78.39 (16)° with the normal to the pyridine ring.

Cited by 18 publications

References 10 publications

Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives

Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives

Covalent d-Block Organometallics: Teaching Lewis Structures and sd/sd2 Hybridization Gives Students Additional Explanations and Powerful Predictive Tools

Covalent d-Block Organometallics: Teaching Lewis Structures and sd/sd2 Hybridization Gives Students Additional Explanations and Powerful Predictive Tools

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