BORINE CARBONYL

Four studies of the thermal decomposition of borine carbonyl have been made1-4. In the absence of a radical scavenger, Burg1 proposed a two-step mechanism 

Combining this equation with standard entropy and enthalpy data, they estimate AJA-i = 2.63 x 10s moled-1, A2 = 1.45 x 10 l.mole-1.sec-1, A 2 = 2.09x10 l.mole-1.sec-1, 2 2 = 17.7 kcal.mole-1. Assuming = 10 -109 Lmole-1. sec-1 gave A = 2.5 x 1013-2.5 x 1014 sec-1. Based on the observed value jfc2/fc i 10-3 they calculate E2—E-1 3.02 kcal.mole-1 and hence El 23.7 kcal.mole-1. 

Felhner and Koski3 tried to isolate reaction (1) by studying the decomposition in a fast flow system coupled to a mass spectrometer. Using the mean of Garabedian and Benson s estimate3 of At, 8.0 x 1013 sec-1, they obtain Et = 23.1+2 kcal.mole-1. Because of the experimental difficulties encountered, the significance of this result is questionable. 

Grotewold et al4 determined kt by studying the decomposition of borine carbonyl in the presence of triethylamine. At constant total pressure the process may be described by reactions (1), (3) and (4) 

The first-order experimental rate coefficient, k = k1+k4[Et3N], was found to be independent of the triethylamine concentration indicating that the contribution of reaction (4) is negligible. A previous study using trimethylamine6 showed that the analogue of reaction (4) was much faster than reaction (1). 

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Simple tetrahedral molecules include H3B. N(CH3)3, borine carbonyl, H3B.C0, (a), the numerous adducts of BF3, and the remarkable molecule B4F6. Pp3, (b). This compound is formed as a very reactive colourless solid when the high-temperature species BF is condensed on to a cold surface with PF3. 

Preparation. The reagent is prepared by reaction of trimethylamine with diborane or with borine carbonyl (BHjCO). In a new procedure developed by Ethyl Corp, an activated aluminum powder and aluminum chloride are added to a solution of triphenyl borate in trimethylamine and the mixture is agitated at 180° under 2,000 p.s.i. of hydrogen. 

Boric acid, 63-66,202,394,1102 Borine carbonyl, 1230 Bomadiene, 1056 Bomene, 1056 Bomyl chloride, 1056 Boroacetic anhydride, 63 Boron tribromide, 66-57 Boron trichloride, 43, 67-68 Boron triiluoride, 68-69,221,369,387,395, 677,701... 

BH2C0 BORINE CARBONYL -2.568 1.7067E-01 -6.8997E-05 1.2108E-08 -7.6892E-13 298 1500 gas... 

Compounds containing B—C Bonds.—High-resolution i.r. spectra of BDsCO and BD3CO were obtained in the region of the X = 0 sub-bands of the Vj and 2+vg-v8 bands.It was not possible, however, to determine the borine carbonyl structure accurately using only the Bq rotational constants. 

A detailed high-resolution i.r. study of specific vibrations of the borine carbonyl species BH3—CO has been undertaken in an attempt to further an understanding of the bonding in the molecule. 

Only a minimum of mechanistic attention has been paid to the catalytic effect that ethers have on the hydroboration reaction. After determining that the hydroboration of olefins with l,2-bis(3-methyl-2-butyl)diborane is first order in olefin and also first order in the substituted diborane, it was suggested that the role of the solvent is to coordinate with the dialkylborane monomer, the leaving group in this particular reaction 101). However, the room temperature hydroboration of ethylene with borine carbonyl 102) intimates, by analogy, that a rather loosely held adduct may account for acceleration of B—H addition to unsaturated systems in ether solvents. The use of a molybdena-aluminum catalyst has been moderately effective in converting an ethylene-diborane mixture to a mixture of ethyldiboranes at room temperature 103). 

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