Synthesis and structural elucidation of some new heterocyclic β-diketone derivatives of boron

Some new β-diketone derivatives of boron having the general formula B₂O(OAc)_4?n[OC(R)$\text{C:CON(Ph)N:C}$ CH₃]_n (where n = 1 or 2; R = CH₃, C₂H₅, C₆H₅ and p-ClC₆H₄) have been synthesised by the reactions of oxy-bis(diacetatoborane) and substituted pyrazolones, such as 4-acyl-3-methyl-1-phenyl-2-pyrazolin-5-ones (acyl = acetyl, propionyl, benzoyl and p-chlorobenzoyl) in dry toluene solution in 1:1 and 1:2 molar ratios. These derivatives have been characterised by elemental analysis, molecular weight measurements. Structures have been proposed on the basis of chemical reactions, IR, ¹H and ¹¹B NMR spectral studies.In the derivatives B₂O(OAc)₃[OC(R)$\text{C:CON(Ph)N:C}$ CH₃] two of the three acetate groups are unidentate and the third is bridged between two boron atoms along with BOB linkage. Whereas the derivatives B₂O(OAc)₂[OC(R)$\text{C:CON(Ph)N:C}$ CH₃]₂ are the mixture of geometrical isomers.