Boronates nuclear magnetic resonance spectroscopy

Boron s electron deficiency does not permit conventional two-electron bonds. Boron can form multicenter bonds. Thus the boron hydrides have stmctures quite unlike hydrocarbons. The B nucleus, which has a spin of 3/2, which has been employed in boron nuclear magnetic resonance spectroscopy. 

Noth, H., and Wrackmeyer, B. (1978) Nuclear Magnetic Resonance Spectroscopy of Boron Compounds, Springer-Verlag, New York. 

H. Noth, B. Wrackmeyer, Nuclear Magnetic Resonance Spectroscopy of Boron Compounds, in NMR - Basic Principles and Progress, P. Diehl, E. Fluck, R. Kosfeld, eds., Vol. 14, Springer Verlag, Berlin-Heidelberg-New York, 1978. 

Nuclear Magnetic Resonance Spectroscopy of Boron Compounds... 

B-1978MI417-01 H. Noth and B. Wrackmeyer Nuclear magnetic resonance spectroscopy of boron compounds, in NMR- Basic Principles... 

Crystalline borosilicate molecular sieves have been the object of an intensive investigation effort since they were reported in the open literature at the Fifth International Conference on Zeolites by Taramasso, et al. (1) A wide range of structures containing framework boron have been synthesized. The physical properties of these borosilicate molecular sieves have been studied by such techniques as X-ray diffraction, infrared and nuclear magnetic resonance spectroscopies, and temperature programmed desorption of ammonia. In addition, the catalytic performance of borosilicate molecular sieves has been reported for such reactions as xylene isomerization, benzene alkylation, butane dehydroisomerization, and methanol conversion. This paper will review currently available information about the synthesis, characterization, and catalytic performance of borosilicate molecular sieves. 

Nuclear Magnetic Resonance Spectroscopy. The use of 11B NMR spectroscopy to examine the state of boron in borosilicate molecular sieves has been reported (21.22.24-26.43.441. Scholle and Veeman (43) reported that the boron resonance is characteristic of tetrahedral boron when the samples are hydrated. Dehydration of a borosilicate sample results in a shift to a trigonal environment, as evidenced by the lineshape and peak position. The trigonal boron remains in the framework, and the change between trigonal and tetrahedral environments is reversible. Boron NMR has also been used to show that boron from Pyrex liners can be incorporated in molecular sieve frameworks during synthesis of MFI and MOR structure types (21.44). 

B. Wrackmeyer, Nuclear magnetic resonance spectroscopy of boron compounds containing two-, three- and four-coordinate boron, Annual Reports on NMR Spectroscopy 1988, 20, 61. 

Boron forms a range of compounds with elements that are less electronegative than itself, called BORIDES. Natural boron consists of two isotopes, B (18.83%), used in steel alloys for control rods in nuclear reactors, and B (81.17%). These percentages are sufficiently high for their detection by splitting of infrared absorption or by nuclear magnetic resonance spectroscopy. 

The Pd(MeCN)4(BF4)2-catalysed conversion of allylic alcohols into allylic silanes and boronates has been investigated by product studies, kinetic studies, and H, B, F, and Si NMR (nuclear magnetic resonance) spectroscopy. The two reactions that occur by the same mechanism involve the formation of a palladium allylic alcohol [(a -allyl) palladium] complex after the alcohol is activated by BF3 formed from a BF4 ion of the catalyst. Then, a rate-determining, stereoselective transmetalation with Si(Me)2 and a reductive elimination of the palladium gives the linear silane. B2pin2 replaces Si(Me)2 in the borylation reaction. 

N6th, H., Wrackmeyer, B. Nuclear Magnetic Resonance Spectroscopy of Boron Compounds . In NMR, Basic Principles and Progress Diehl, P., Fluck, E., Kosfeld, R., Eds. Springer-Verlag Berlin, 1978 Vol. 14. 

The section on Spectroscopy has been retained but with some revisions and expansion. The section includes ultraviolet-visible spectroscopy, fluorescence, infrared and Raman spectroscopy, and X-ray spectrometry. Detection limits are listed for the elements when using flame emission, flame atomic absorption, electrothermal atomic absorption, argon induction coupled plasma, and flame atomic fluorescence. Nuclear magnetic resonance embraces tables for the nuclear properties of the elements, proton chemical shifts and coupling constants, and similar material for carbon-13, boron-11, nitrogen-15, fluorine-19, silicon-19, and phosphoms-31. 

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