The interesting redox chemistry of manganese (Mn), its high abundancy in Earth's crust and its known properties in electron transfer processes make manganese-based materials like its oxides, nitrides or the sulfides suitable for a broad range of applications. Especially, when applied as thin films, these materials can function in a variety of applications that includes amongst others, cathodes in alkali-metal ion batteries , electrocatalysts for oxygen evolution reaction (OER) or dilute magnetic semiconductors (DMS) in spintronics . When utilized as a thin film, the quality and functionality of Mn-based layered materials are strongly dependent on the deposition method. While several deposition methods have been used for growing thin films of Mn-based materials such as solution based methods (e.g. dipcoating , sol-gel , electro-deposition ) physical vapor deposition (e.g. pulsed laser deposition , molecular beam epitaxy ), chemical gas phase deposition techniques such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) are favored for depositing thin films. Both these methods can deliver thin films with very good control over homogeneity and uniformity on large area substrates and on complex geometries and they are industry compatible. 10] For successful materials processing development using these two technologies, the precursors employed play an important role. An overview of the Mn precursor classes reported are illustrated in Table . Interestingly, in contrast to the general wide range of oxidation states for known Mn compounds of -III up to +VII , the known Mn precursors are limited to the oxidation states 0,+I, +III and dominantly +II. To the best of our knowledge the only known precursor with the oxidation state 0 is the homoleptic [Mn2(CO)10]. The precursor class of manganese carbonyls additionally include the three known Mn +I precursors [Mn(CO)5Me] , [Mn(CO)5(COMe)] and a hybrid between carbonyl and cyclopentadienyl precursor, [Mn(MeCp)(CO)3] (Figure ). The limited reactivity towards common co-reactants such as H2O and the need for high deposition temperatures led to the consideration of another carbon coordinated precursor class, namely manganese cyclopentadienyls for ALD of Mn oxides. The predominantly used and commercially available Mn complexes for use in CVD and ALD include the three homoleptic derivates, namely, [Mn(Cp)2] , [Mn(MeCp)2] and [Mn(EtCp)2] (Figure ). These low melting and highly volatile precursors can be obtained using straightforward synthetic routes, but lack stability under ambient conditions which can lead to carbon impurity inclusion during thin film growth. Precursors which are able to overcome these drawbacks are the oxygen coordinated Mn-tris-ß-diketonates (e.g., [Mn(thd)3] and [Mn(acac)3] (Figure )) (thd =2,2,6,6tetramethyl-3,5-heptanedionate; acac = pentane-2,4-dionate). The most commonly studied ALD precursor for manganese based oxides , [Mn(thd)3] as representative for the Mn +III ß-diketonates enables the deposition of high purity manganese oxides, but needs high process temperatures and a strong oxidant like ozone. Further modification on this precursor class resulted in the Mn +II ß-diketonates which are stabilized by TMEDA (N,N,N`,N`tetramethylethane-1,2-diamine) coordination [Mn(hfa)2•TMEDA], and [Mn(tfa)2•TMEDA](tfac = 1,1,1-trifluoro-2,4-pentanedionate; hfac = 1,1,1,5,5,5-hexafluoro-2-4-pentanedionate) Figure )). These precursors have been only used for plasma enhanced-CVD (PECVD), so there is little knowledge on their wider use in thin film deposition. However, the potential fluorine incorporation into the resulting thin films, due to the fluorinated ligands, can be a disadvantage. Another interesting but rarely studied precursor is the mixed O-/N-coordinated [Mn(( t Bu)2COCN t Bu)2] ( t Bu2COCN t Bu = 3-((tert-butyliminomethyl)-2,2,4,4tetramethylpentane-3-oxidinate) which was reported by Kalutarage et.al. in 2013. (Figure )) However, no ALD or CVD application was demonstrated. One other class of precursors which potentially overcomes the above-mentioned drawbacks are the all-nitrogen coordinated precursors. (Figure )) The first study was performed by Lim et.al. who reported two Mn based amidinate (AMD) precursors; [Mn2(μ-i Pr2-MeAMD)2(η 2 -i Pr2-MeAMD)2] and [Mn( t Bu2AMD)2] (Figure )). Following the successful implementation of the mononuclear tert-butyl derivative in ALD, and the general success of amidinate based precursors also for other transition metals , further similar derivates with different substituents were developed. While [Mn( i Pr2-n-pentylAMD)2] (Figure )) was tested for manganese metal CVD , the application of the silicon substituted aminopyridinato manganese precursor, [Mn(TMS-APy)2] (Figure )) (TMS-APy = N-(trimethylsilyl)pyridin-2-aminate) in CVD process resulted in manganese silicates (MnSiyOx). Among other all N-coordinated precursors reported, neither [Mn( t Bu2DAD)2] (Figure ))(DAD = 1,3-diazadienate) nor [Mn(R2NacNac)2] (Figure ))( NacNac = N,N′-dialkyl-βdiketiminate) or the structurally similar [Mn( t BuNNCHCHN t Bu)2] [31] (Figure ))( t BuNNCHCHN t Bu = 1,5-di-tert-butyl-1,2,5triazapentadienate) were so far employed in ALD or CVD processing, although they possess promising thermal properties as reported in the corresponding studies. As shown in the table, there are several precursors that have been explored, but most of them do not meet the necessary requirements for ALD and CVD processing of Mn containing materials. Thus, this study focused on the exploration of new Mn complexes through a systematic study combining organometallic synthesis using a range of new ligand systems, compound characterization, and theoretical studies. Motivated by the promising initial findings on the amidinates (Figure )), we explored this class of Mn precursors by systematically introducing the structurally related guanidinates and formamidinate ligand systems. The structural variance in the ligand backbone significantly shapes the electronic structure, while also exerting a notable influence on the steric properties of the ligands. This can influence the coordination chemistry and consequently the physico-chemical properties based on which the correlation between the properties can be established. A series of new Mn complexes were synthesized and were analyzed thoroughly via spectroscopy, structural investigations, and thermal analysis. The high reactivity of these compounds towards moisture and oxygen were assessed via density functional theory (DFT) calculations to validate the origin of the pronounced reactivity. Based on the interesting results from the DFT studies, we investigated the influence of the manganese coordination sphere moving from all-nitrogen to mixed O/N coordinated complexes, to further tune the physico-chemical properties. The resulting Mn-ketoiminate class of compounds were successfully isolated and characterized in detail. A direct comparison of the all N-with the mixed O-/N-coordinated Mn precursors in terms of the precursor characteristics closes the gap between the less studied O-/N-coordinated manganese precursors. Such a detailed and comparative study gives valuable input for improvement and development of new ALD and CVD processes and their chemistry for Mn-based materials.