Diborane spectra

The compound C13CH=NBH2 is obtained upon reaction of trichloroaceton-itrile with diborane during the synthesis of 1,3,5-trichloroethylborazine (Eq. (13) 16)) it is undoubtedly not monomeric as indicated by its i.r. spectrum (v BH2 cm-1, v C=N 1705 cm-1 22>) Most likely the material is dimeric and it is difficult to isolate in pure form due to the ready conversion to the bor-azine derivative. 

It should be noted that as of now there is no direct physical evidence (e. g., ESR spectrum) for the existence of the B2 H5 radical and much of the mechanistic discussion of the photochemistry of diborane(6) is speculative. If Eqs. (1) and (2) represent the correct mechanisms the rate of the quantum yields for H2 to B4H10 production would be unity. Although this ratio tends towards unity at lower pressures, this simple mechanism did not explain the ratio of two approached at-higher pressures. In order to explain this, an additional primary process was proposed, i. e., a disproportionation of two B2H5 radicals ... 

The density of liquid l-methyldiborane(6) at -126° is 0.546 g/mL, or 13.1 mmole/mL.s Its vapor pressure is 55 torr at -78.5° the compound is thermally unstable at this temperature and slowly disproportionates to diborane(6) and l,l-dimethyldiborane(6).1,6 Although the infrared spectrum can be used to identify this compound, similarities to the spectra of the disproportionation products present difficulties in assaying purity.7 The nB NMR spectrum is useful for identifying and assaying 1-CH3B2H5. At -110°, the "B NMR... 

Tetrakis(acetato)di- U-amido-diborane is a white crystalline compound which is not too sensitive to moisture. It can be stored in a nitrogen atmosphere in a refrigerator for long periods without decomposition. It is sparingly soluble in most organic solvents and slowly dissolves in glacial acetic acid and acetic anhydride. Monoclinic and triclinic crystalline forms were obtained by recrystallization from acetic anhydride and glacial acetic acid, respectively.1 The infrared spectrum recorded (Beckman i.r.-12) by the KBr pellet technique contains major absorption bands (at frequencies cm.-1) 3280(s), 3230(s), 3100(s), 1740(w,sh),... 

However, the boron-11 nmr spectrum of (C4He)B2H4 116-117> clearly shows that it has structure 1 below, not structure a. Moreover, the chemical properties reported for (C4He)2B2H2 115> are not consistent with those of known tetraalkyl derivatives of diborane(6), e.g. at room temperature it does not hydroborate terminal olefins nor react with methanol. Brown and coworkers therefore proposed 114> structure 2 for (C4H6) 2B2H2. 

Sodium cyanide and diborane react in the presence of ether to give NaH3BCNBH3 2R20. The cyanide bridged structure is assigned on the basis of two quadruplets of equal intensity in the B11 n. m. r. spectrum [Aftandilian, Miller and Mutterties, 1961). 

Nevertheless the correspondence of diborane with ethylene was found from extensive investigations on the infra-red absorption spectrum and the Raman spectrum to be greater than with ethane. There is also a correspondence in the Raman spectrum with A12C16 which is built up of two tetra-hedra with a common edge. 

The B resonance spectra have been used to follow the deuteration of tetraborane by fully deuterated diborane. The spectra of the two deuterated tetraboranes B4H8D2 and B4D8H2 have been discussed it was reported that the former compound quickly reverted to normal tetraborane. The spectra of the two complexes of tetraborane with carbon monoxide and phosphorus trifluoride were described by the same authors. The B spectrum confirmed the structure of the g-deuterotetraborane-10 with a bridging deuterium atom. ° ... 

Reduction of 20 with diborane in bis(2-methoxyethyl)ether 3delds the bis(cyclam) derivative (21) 48). Addition of one equivalent of nickeUII) nitrate to an aqueous solution of 21 at pH 7, followed by one equivalent of copperdi) nitrate, is expected to result in a mixture of complexes in the proportion of 1 1 2 [di-Cu(II) complex dirNidl) complex Cu(II)/Ni(II) complex] (provided the two rings behave independently toward both metals). Separation of these three species was achieved by ion-exchange chromatography. Spectral and electrochemical investigations on the above binuclear complexes were undertaken. The visible spectra are very similar to those of the corresponding (mononuclear) cyclam complexes and, for example, the spectrum of the binuclear complex is virtually equal to the sum of the spectra of [Cu(cyclam)] and [Ni(cyclam]. Despite this, electrochemical studies confirm the presence of a weak interaction between the coordinated metals in each dinuclear complex. This is manifested by a shift in the second oxidation potential [M(II) M(IID] to a more positive value in each case. 

When 348 was treated with acetic anhydride in the presence of a trace of sulfuric acid, a product (C20H22N2O3) was formed. The PMR spectrum lacked both the hydroxyl absorption and the methyl singlet. The loss of 60 mass units compared to 348 indicated the enamide structure 349 as the most likely. Attempts to reduce 349 failed, but alkaline hydrolysis and diborane reduction afforded a mixture, the major component of which was identified as TV-deacetyl-20-deethylaspidospermine (350). The stereochemistry at C-21 and C-20 were not determined, but the three minor products were isomers of the major product showing a base peak in the mass spectrum at m/e 96 (351). 

Due to the hydrolysis of diborane, the experimental investigation of the H3B 0H2 complex is difficult and introduces some uncertainty about whether the observed features in the Hel spectrum really are due to H3B OH2 or something else. The agreement between the calculated (EP2) peaks and the UPS spectrum is as expected except for the observed feature at 14.4 eV. This is not consistent with the theoretical result, but before suggesting that this feature... 

The shapes of the bonding 0 g and b3 MOs clearly show that the electron pairs occupying these MOs are delocalized over all three nuclei. Because of the small size of the H atoms, there also exists a certain amount of direct B-B bonding in diborane that helps to stabilize the molecule. The MO diagram is also consistent with the PES spectrum of diborane, which shows six peaks of comparable intensity at 11.8, 13.3, 13.9, 14.7, 16.1, and 21.4 eV. Four of these peaks are due to ionization from the four terminal B-H bonding MOs (not shown in the figure), while the two peaks at 13.3 and 14.7 eV correspond with the and 0 g MOs, respectively, on the B-H-B bridges. 

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