η 2 character while 2 demonstrated a more ambiguous pattern with a larger coordination preference towards the C-C bridge (58% η 5 and 42% η 2 character). In addition to this bend, the aryl substituents were twisted by 20°─24° (2) and 15°─26° (3) relative to the planar Pn 2-core in the XRD structures, but only one set of magnetically equivalent aryl protons were observed in their room temperature NMR spectra, suggesting a rapid (likely concerted) flip in solution. This flexible, pairwise substituent bend and twist found in these tetra-substituted pentalenides is likely to relieve steric repulsion between the aryl groups in 1,3 and 4,6 positions and has implications for electronic substituent effects by affecting the degree of π overlap between the aryl groups and the Pn 2-core (see below). As previously found for 2, the use of a heterobimetallic combination of two different alkali metals improved the solubility further: subjecting m Xyl4PnH2 (4H2) to sequential deprotonation with first KHMDS and then LiNEt2 cleanly furnished K•Li [4], which did not precipitate from THF for more than 12 months and allowed solution phase analysis at variable temperature. Cooling a sample of K•Li [4] yield and characterised by 1 H NMR and IR spectroscopy. To the best of our knowledge, no method for accessing pentalenides with different substituents on each ring in synthetically useful yields has ever been reported. Independent control over the steric and electronic properties of each ring of the fused pentalenide core promises access to well-defined heterobimetallic complexes with potentially interesting electrochemical, photophysical and catalytic properties. We thus investigated the deprotonation of Ph2 p Tol2PnH2 (5H2) and Ph2 m Xyl2PnH2 (6H2) as their respective double bond isomer mixtures with LiNEt2 in THF (Scheme 2). Pleasingly, Li2[Ph2 p Tol2Pn] (Li2 [5]) and Li2[Ph2 m Xyl2Pn] (Li2 [6])