Methanes dibenzoylmethane

The displacement of the heavy ligand by the lighter molecule HCN yields an increase in the sensitivity, a concept identified as "mass amplification", and was not applied to piezoelectric detectors before. As mass is lost from the coated crystal when exposed to HCN, the frequency increases whereas a decrease in frequency is expected if moisture is absorbed by the coating. The effect of humidity was studied over the range of 40-92% RH, and it was shown that humidity plays a part in the reacation. Since the reaction is irreversible and the nickel complex is prone to hydrolysis, the coated crystal could be used once only. Substitution of other ligands in nickel complexes, including dibenzoylmethane, dipivaloyl-methane, formate and acetate, did not improve the selectivity towards HCN. 

Dibenzoylmethane (l,3-diphenyl-l,3-propanedione) [120-46-7] methane from petroleum ether or MeOH. [Beilstein 7IV 2512.]... 

Condensation reactions on nickel(II) matrices are sensitive to steric effects. X-Ray structm analysis showed [310, 320-328] that H2L263 and its metal complexes are saddle-like, rather than planar. The sources of structural nonplanarity are steric repulsions between methyl groups R, 4 and orr/K>-aromatic protons of the Schiff bases. The increase in the bulk of the groups in these positions hinders macrocyclisation. For example, 3,5-heptanedione, 4,6-nonanedione and 1-phenyl-2,4-pentanedione form cyclic products [Ni(L274)]-[Ni(L276)J, whereas dibenzoyl-methane, 2,6-dimethyl-3,5-heptanedione and 2,2,6,6-tetramethyl-2,5-heptanedione do not give macrocyclic compounds in the presence of nickel(II) and o-phda [300, 320]. In the case of dibenzoylmethane, the nickel(II) )ff-diketonate bis-diamine adduct is isolated (Eq. 2.164) [319]. 

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