Five- and Six-Coordinate Nitrogen in Azaborane Clusters

Paetzold, Peter

doi:10.1002/(sici)1099-0682(199802)1998:2<143::aid-ejic143>3.3.co;2-w

Cited by 6 publications

(9 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Suitable crystals of 4 d for single‐crystal X‐ray analysis were obtained by vacuum sublimation (Figure 10; Tables 1 and 2). Expectedly, the B atom in 4 d is trigonal planar coordinated (angle sum of 360°; Figure 10) and the short BN bond of 1.387(6) Å indicates the presence of a double bond ( i Pr 2 NBfc:25 1.371(6) and 1.384(6) Å) 30. As mentioned before, boron‐bridged [1]FCPs are the strained sandwich compounds with the highest known α angles.…”

Section: Resultsmentioning

confidence: 75%

A Flexible Approach to Strained Sandwich Compounds: Chiral [1]Ferrocenophanes with Boron, Gallium, Silicon, and Tin in Bridging Positions

Sadeh¹,

Schatte²,

Müller³

2013

Chemistry A European J

View full text Add to dashboard Cite

The enantiomerically pure dibromoferrocene 3 [(Sp,Sp )-1,1'-dibromo-2,2'-di(isopropyl)ferrocene], equipped with two iPr groups in α positions, was prepared using known "Ugi amine" chemistry. Species 3 was targeted in order to gain access to new [1]ferrocenophanes ([1]FCPs) to be used as monomers for ring-opening polymerization. The iPr groups on the sandwich unit were introduced to stabilize bridging moieties, as well as to increase solubilities of targeted metallopolymers. The planar chiral dibromide 3 can quantitatively be lithiated at 0°C [2 equiv nBuLi, hexanes/thf (9:1), 30 min]. Salt-metathesis reactions with respective element dichloride species gave chiral [1]FCPs with a variety of bridging moieties [ERx =Ga[2-(Me2NCH2)C6H4] (4 a), SiMe2 (4 b), SntBu2 (4 c), BNiPr2 (4 d)]. The new [1]FCPs were fully characterized including single-crystal X-ray analysis. The stabilizing iPr groups on the Cp rings increase the thermal stabilities of 4 b-d compared to known [1]FCPs, equipped with the same bridging moieties. All three compounds 4 b-d are volatile and could be isolated by vacuum sublimation. Our new approach to [1]FCPs has the potential to overcome many of the existing difficulties in ferrocenophane chemistry, such as limited stability of starting monomers and low solubilities of resulting polyferrocenes.

show abstract

Section: Resultsmentioning

confidence: 75%

A Flexible Approach to Strained Sandwich Compounds: Chiral [1]Ferrocenophanes with Boron, Gallium, Silicon, and Tin in Bridging Positions

Sadeh¹,

Schatte²,

Müller³

2013

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Significant backbonding interactions from π-donating substituents on polyborane cages have been previously observed in both halogenated and amino-substituted derivatives. ,, Backbonding from O to B in the decaboranyl ethers was evidenced by shortened B−O bonds and an sp 2 hybridized oxygen. Table compares the values for the B−O bonds lengths and the B−O−C angles in the decaboranyl ethers with those found in B(OCH 3 ) 3 , where π-backbonding is strong, and in B(OCH 3 ) 4 − , where π-backbonding is impossible.…”

Section: Resultsmentioning

confidence: 77%

Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

2011

View full text Add to dashboard Cite

The selective syntheses of new classes of decaboranyl ethers containing a range of functional groups substituted at the B5 or B6 positions were achieved through the reaction of alcohols with halodecaboranes. The surprising regioselectivity of the reaction, where the reaction of the 6-halodecaboranes (6-X-B(10)H(13)) with alcohols yielded the 5-substituted decaboranyl ethers (5-RO-B(10)H(13)) and the reaction with 5-halodecaboranes (5-X-B(10)H(13)) gave the 6-substituted decaboranyl ethers (6-RO-B(10)H(13)), was confirmed by NMR and X-ray crystallographic analyses. The crystallographic determinations also showed that the decaboranyl ethers had shortened B-O bonds and apparent sp(2) hybridization at oxygen indicating significant π-backbonding from oxygen to the cage boron. A possible substitution mechanism was computationally identified involving: (1) initial nucleophilic attack by the alcohol-oxygen at a site adjacent to the 5- or 6-halo-substituted boron, (2) movement of the terminal hydrogen at the point of attack to a bridging position, (3) formation of a 5-membered (B-O-H-Cl-B) cyclic transition state allowing the acidic methanolic-hydrogen to bond to the halogen, (4) release of HX, and finally (5) movement of a bridging hydrogen into the vacated terminal position. Deuterium labeling studies confirmed the movement of hydrogen from a bridging position of the halodecaborane into the halogen-vacated terminal position on the decaboranyl ether product. The relative reaction rates of the 6-X-B(10)H(13) compounds (X = F, Cl, Br, I) with alcohols were likewise found to be consistent with this mechanism.

show abstract

“…1. 7 The 10-vertex azaborane B 9 H 9 NH has the nitrogen atom at a degree 4 rather than a degree 5 vertex of the bicapped square antiprismatic B 9 N cage. 2).…”

Section: Introductionmentioning

confidence: 99%

Cyclopentadienylcobalt azaboranes violating the Wade–Mingos rules: a degree 3 vertex for the nitrogen atom

2015

View full text Add to dashboard Cite

The experimentally realized chemistry of polyhedral azaboranes includes the very stable cobalt derivative CpCoNHB 9 H 9 , which has been synthesized and structurally characterized by X-ray crystallography. The structures and energetics of the complete series of cobaltaazaboranes CpCoNHB nÀ2 H nÀ2 have now been studied by density functional theory. Low-energy structures are found for the 8-and 9-vertex systems based on non-spherical deltahedra providing a degree 3 vertex for the nitrogen atom and thus violating expectations from the Wade-Mingos rules. Thus the lowest energy CpCoNHB 6 H 6 structure is an antipodally bicapped octahedron with the nitrogen atom at a degree 3 vertex rather than the most spherical bisdisphenoid. For the 9-vertex CpCoNHB 7 H 7 system the lowest energy structures are based on the most spherical tricapped trigonal prism. However, isomeric CpCoNHB 7 H 7 structures at $13 kcal mol À1 in energy above these structures are found with a central capped bisdisphenoid having the nitrogen atom at the degree 3 capping vertex. In contrast to the 8-and 9-vertex systems, the lowenergy CpCoNHB nÀ2 H nÀ2 structures for the 10 to 12 vertex systems are based on the most spherical deltahedra. For the 10-and 11-vertex systems all of the low-energy structures have the nitrogen atom at a degree 4 vertex. The predicted Co-N and Co-B distances in the lowest energy CpCoNHB 9 H 9 structure are very close to the experimental values.

show abstract

Five- and Six-Coordinate Nitrogen in Azaborane Clusters

Cited by 6 publications

References 25 publications

A Flexible Approach to Strained Sandwich Compounds: Chiral [1]Ferrocenophanes with Boron, Gallium, Silicon, and Tin in Bridging Positions

A Flexible Approach to Strained Sandwich Compounds: Chiral [1]Ferrocenophanes with Boron, Gallium, Silicon, and Tin in Bridging Positions

Syntheses and Surprising Regioselectivity of 5- and 6-Substituted Decaboranyl Ethers via the Nucleophilic Attack of Alcohols on 6- and 5-Halodecaboranes

Cyclopentadienylcobalt azaboranes violating the Wade–Mingos rules: a degree 3 vertex for the nitrogen atom

Contact Info

Product

Resources

About