While in 1 the dianionic charge was delocalised across but confined within the pentalenide core, in 2 and 3 more than half of the overall negative charge was delocalised into the four aryl substituents. This correlated with a 1 ppm downfield shift of the two equivalent wingtip protons in 2 (6.79 ppm) and 3 (6.66 ppm) compared to those of 1 (5.76 ppm). The slightly higher shielding of the wingtip protons of 3 with respect to those of 2 can be ascribed to the +I effect of the p-tolyl groups leading to slightly less effective charge delocalisation in this case.