Pentalenides have been intriguing organic and organometallic chemists ever since Katz and Rosenberger reported the first example of the planar 10π aromatic bicyclic Pn 2-(1; C8H6 2-) in 1962. Unlike its monocyclic congener COT 2-(C8H8 2-), pentalenide ligands can access a variety of bonding modes from η 1 to η 8 that allow them to fold around a single metal centre or link two metals together. This ligand manifold has thus been utilised in several mono-and bimetallic d-or f-block Pn 2-complexes which have found applications in the activation of small molecules such as N2 or CO2 and in olefin polymerisation catalysis. Compared to the monocyclic Cp -(C5H5 -) ligand class it has remained a rare and rather exotic ligand due to the difficulty of its preparation, hampering further studies of its organometallic chemistry and utilisation in cooperative bond activation strategies based on multimetallic complexes. No general synthetic protocol which would allow the controlled variation of substituents is known, and to date only eight derivatives of this ligand architecture have been reported (Scheme 1): Knox, Stone et al. described four Pn 2-variants obtained via thermal rearrangement of substituted cyclooctatetraenes and cyclooctatrienes; Cloke et al. subjected unsubstituted Pn 2-to two successive nucleophilic substitution reactions at the 1-and 4-position, creating two variants; Ashley et al. developed a multi-step synthesis of a permethylated Pn 2-; and we recently reported the synthesis of 1,3,4,6-Ph4Pn 2-(2) via a two-step solution-phase synthesis from 1,4-Ph2CpH and chalcone. Again contrary to the ubiquitous cyclopentadienides, no systematic investigation of substituent effects exists, meaning that we currently don't understand the extent and nature of electronic variation possible within pentalenides. Here we report the deprotonative metalation chemistry of several substituted dihydropentalenes (PnH2) § to yield nine new alkali metal pentalenides with symmetrical and unsymmetrical substitution patterns in 1,3-and 1,3,4,6-positions, and for the first time investigate their electronic effects on the dianionic Pn 2-core by NMR spectroscopy and DFT calculations, including charge distribution analyses, nucleus-independent chemical shift (NICS) scans as well as anisotropy of the induced current density (ACID) calculations. § Remarks regarding the access of multisubstituted dihydropentalenes can be found in the corresponding literature. 4 Scheme 1: Substituted pentalenides reported to date (left) and contribution of the work reported here (right). Since the homobimetallic s-block salts of the symmetrically tetraphenyl-substituted 2 displayed poor solubility in a range of organic solvents, we investigated the possibility of enhancing solubility via the synthesis of the corresponding p-tolyl and m-xylyl analogues, dilithium 1,3,4,6-tetra-ptolylpentalenide Li2[ p Tol4Pn] (Li2 [3]) and dilithium 1,3,4,6-tetrakis(3,5-dimethylphenyl)pentalenide Li2[ m Xyl4Pn] (Li2 [4]). Both compounds could be readily synthesised within a few hours at ambient temperatures in spectroscopically quantitative yield via double deprotonation of the corresponding dihydropentalenes with LiNEt2 in tetrahydrofuran (Scheme 2). Indeed, their much improved solubilities allowed for full characterisation by multi-nuclear NMR spectroscopy as well as mass spectrometry. As was the case for 2, the 1 H and C NMR spectra of 3 and 4 indicated D2h symmetry, and their Li NMR chemical shifts between 0.7 and -3.8 ppm suggested solvent-separated ion pairs (SSIP) in THF solution at room temperature. The 1 H NMR signals for the wingtip protons in 2-and 5position (denoted H 2 and H 5 ) displayed slight upfield shifts of 0.06 ppm in 4 and 0.13 ppm in 3 compared to 2, demonstrating a rather small influence of the meta-and para-methyl groups on the electronics of the pentalenide core (see also Figures S11─S18). While both 3 and 4 showed markedly higher solubility in THF than 2, some precipitation of microcrystalline material started to occur within 24 hours. The crystal structure of [Na(THF)3]2[3] obtained using 2.1 equivalent NaNH2 as the base (Scheme 2) was found to be iso-structural to that of [Na(THF)3]2 [2], both containing solvated sodium in anti configuration (Figure ). In both molecules, the aryl substituents were bent away from the Pn 2-plane by 14─19°, with a pair at one ring pointing upwards and the other pair downwards. As no significant aryl-metal interactions were found in the XRD data, and the 1 H and C NMR chemical shifts of 2 and 3 were similar in solution (Tables and, chapter 3.1 in the supporting information), the observation that their substituents had opposite configuration in the solid state (bent towards the metals in 2 but bent away from the metals in 3) can be ascribed to packing effects that suggest a degree of flexibility in these molecules.