Bis(3,5-dimethylpyrazol-1-yl)alkanones and their reactivity with [PdCl2(NCMe)2]: Isolation of bis(3,5-dimethylpyrazol-1-yl)propan-1-one palladium(II) chloride and C–H activation of propanone linker

Four new bis(3,5-dimethylpyrazol-1-yl)alkanones were prepared by the reaction of the respective alkanoyl chloride with 3,5-dimethylpyrazole: L1 from chloropropionyl chloride, L2 from 4-chlorobutyryl chloride, L3 from oxalyl chloride and L4 from adipoyl dichloride; all in moderate yields. Of the four compounds only L1 successfully reacts with [PdCl2(NCMe)2] to yield [PdCl2(L1)] in 41% yield, which on heating in toluene leads to C–H activation to produce [PdCl(L1′)], where L1′ is deprotonated L1, in very low yield.