The high abundance of magnesium in the Earth's crust, coupled with its low toxicity, has driven considerable interest in exploring the potential of Mg-based complexes for various applications. Extending beyond the well-established organomagnesium chemistry pioneered by Mg complexes have demonstrated utility in diverse reactions, including hydroelementation, Lewis-acid catalysis, 9,10 polymerisation, and dehydrocoupling. These complexes are often stabilised by anionic diketiminate (NacNac) ligands, which employ hard nitrogen donors to support the Mg centres. The propensity for dimerisation (resulting in a Mg 2 X 2 "diamond core") in such systems is well-documented, with a variety of bridging ligands, such as halides, hydrides, amidoboranes, and alkyl groups, forming dimers that mitigate the electronic and coordinative unsaturation of monomeric species. The nuclearity of Mg complexes, influenced by factors such as steric strain, the presence of coordinating solvents or co-ligands, and co-ligand size, significantly impacts their reactivity. For example, computational studies by Garcia et al. on Mg-catalysed hydrosilylation of alkenes have shown that dinuclear complexes can retain their nuclearity during alkene insertion, whilst subsequent steps involve monomeric species. The cooperative reactivity of these dinuclear complexes has been highlighted in work by Spielmann et al., where dimagnesium complexes based on dinucleating (bis-NacNac) ligands were shown to result in an alternative mechanistic pathway and decreased onset-temperatures for the dehydrocoupling of amidoborane complexes. Additionally, Kember et al. have demonstrated that a dimagnesium complex bound to a macrocyclic ligand is highly active towards epoxide/CO 2 ring-opening copolymerisation (ROCOP). Despite these advantages, the flexibility of the ligands in these examples often allows the Mg centres to adopt variable distances, complicating efforts to study the intrinsic reactivity of the dimagnesium core. To address this challenge and harness the advantages of enforced nuclearity, we aimed to synthesise dimagnesium complexes within a rigid, dinucleating framework. We chose the 1,8naphthyridine motif as the basis for our ligands, as this framework provides a constrained environment to enforce close proximity between the Mg centres and suppresses monomerdimer equilibria that could alter reactivity. Previous work has shown that the phosphine donors of the naphthyridine-based t-Bu PNNP ligand developed by our group can be a poor match for hard metals. As such, in this work, we introduce the Di-Amino-Methylene-Naphthyridine ( dipp DAMN) and Naphthyridine Di-Carboxylamide ( dipp NDC) ligands. Both ligands feature anionic flanking donors, making them more suitable for stabilising dinuclear cores of harder metals such as Mg. We report the deprotonation chemistry of both ligands and detail the synthesis and characterisation of various dimagnesium complexes supported by these ligands and quantify their steric profiles. These studies expand the library of dimagnesium complexes and offer insights into how nuclearity and ligand design influence magnesium-based coordination chemistry and reactivity, displaying markedly divergent behaviour even upon seemingly subtle changes in ligand architecture. The dipp DAMN ligand (Scheme 2, left) was synthesised as a slightly air-sensitive white solid in three steps from 2,7-dimethyl-1,8-naphthyridine in a 32% overall yield (see ESI Section 1.2). We envisioned that isolation of the dipotassium salt of the ligand would allow access to complexes of metals where internal base precursors are not available, similar as demonstrated for the related t-Bu PNNP ligand. Accordingly, the dipp DAMN ligand was treated with two equiv of KOt-Bu in THF, which led to a dark orange solution. Analysis of the reaction mixture by 1 H-NMR (toluene-d 8 , 298 K) spectroscopy revealed broad resonances, which we attributed to fluxional binding of K + . Using VT-NMR spectroscopy, no decoalescence was observed down to 193 K (toluene-d 8 , see ESI Figure ). Notably, the addition of 1 equiv 18crown-6 to this mixture resulted in a colour change to dark green and the concomitant formation of 1. The 1 H-and 13 C{ 1 H}-NMR spectra (C 6 D 6 , 298 K) showed a number of resonances indicative of the loss of the C 2v -symmetry (see ESI Section 1.4). The 1 H-NMR spectrum revealed four equally integrating naphthyridine resonances (δ = 6.34-5.78 ppm) at a more upfield shift compared to the free ligand, which agrees with partial dearomatisation of the naphthyridine core. This is further confirmed by the observation of a singlet at δ = 5.46 ppm which we attribute to the methine proton. The presence of a broader apparent singlet at δ = 4.84 ppm (attributed to N-H) and a doublet ( 3 J H,H = 4.8 Hz) at δ = 3.98 ppm (attributed to -CH 2 ) integrating in a 1:2 ratio is consistent with one side of the naphthyridine motif being doubly deprotonated and the other side being left intact. One N-H proton being still present in 1 could be additionally confirmed through the observation of a weak intensity vibration at 3502 cm -1 in the ATR-IR spectrum. Deprotonation of the free ligand in the related t-Bu PNNP ligand can result in either the cis-isomer (i.e. the donor arm pointing towards the binding pocket) or the trans-isomer. To gauge which of the isomers was obtained in this case, a 2D-NOESY spectrum was recorded of 1. The antiphase cross-peak between the methine resonance and one the naphthyridine resonances at δ = 6.02 ppm confirmed the formation of the cis-isomer (see ESI Figure ). The same 2D-NOESY however also showed an in-phase cross-peak (EXSY) between the methine resonance and a very broad resonance at δ = 6.63 ppm. Recording VT 1 H-NMR spectra of a toluene-d 8 solution of 1 at lower temperatures revealed sharpening of this resonance with a clear peak being visible at temperatures below 233 K (see ESI Figure ). This allowed for integration, showing a 1:1 ratio with the methine resonance.