Alkyl derivatives of alkaline earth (AE) and rare earth metals (RE) are highly desirable synthons of great utility in synthetic transformations and as organometallic starting materials. The chemistry of AE and RE alkyl is dominated by the high polarization of the M-C interaction, which makes the carbanion extremely nucleophilic. This aspect, combined with the high electropositive character of the AE and RE metals, has a detrimental effect on the stability of alkyl derivatives, leading often to facile decomposition via inter-and intramolecular C-H activation, αand β-hydride elimination, solvent degradation and more. To counter these drawbacks, several strategies can be employed, which include: 1) kinetic saturation of the metal coordination sphere; 2) chelation; 3) hyperconjugation to stabilize the methanide carbanion, {CR3} -. Iminophosphoranomethanide ligands of the type (R-N=P(Ph)2)2CH -( R BIPM-H -, R = trimethylsilyl, iso-propyl, cyclohexyl, aryl) combine all of these aspects, and as a result have been used extensively to prepare alkaline earth (AE) and rare earth (RE) methanide complexes (Figure ), e.g. [Ba( TMS BIPM-H)2] and [Dy( TMS BIPM)( TMS BIPM-H)]. These species have been investigated for their reactivity, and have also been employed as precursors towards the stabilisation of alkylidene complexes. Le Floch and Mézailles developed an analogous ligand, {(S=PPh2)2CH} -, which was used in a similar fashion for the synthesis of homoleptic bis-methanide complexes for divalent metals or methanide/methanediide species (Figure ). Typical synthetic routes to these compound include protonolysis of the proligand with Ln tribenzyl or tris-amido precursors. Alternatively, salt metathesis of a Group 1 salt of the ligand with a metal halide typically yields the halide-bridged or monomeric heteroleptic species. Moreover, Chen and co-workers prepared an asymmetric analogue of Le Floch's thiophosphoranomethanide ligand (Figure ), S=P(Ph)2CHSiR3 (R = Me, Ph). This ligand was used to prepare heteroleptic complexes supported by a tethered bis-diketiminate ligand, NacNac NMe2 (NacNac NMe2 = {N(Dipp)C(Me)CC(Me)N(CH2CH2NMe2)} -), such as [Sc(NacNac NMe2 ){C(SiMe3)PPh2Sκ 2 S,C}]. This ligand system was used with several other rare earths, including Y, La, Sm, and Lu, forming a suite of compounds whose reactivity with small molecules was investigated in detail. Gessner and co-workers used a thiophosphoranomethanide ligand similar to Chen's, {S=P(Ph)2CHSiMe3} -, with palladium and isolated the heteroleptic complex [Pd(κ 2 C,S-{S-P(Ph)2CHSiMe3})(PPh3)2]. Furthermore, Grévy and co-workers employed a similar ligand, . However, the latter could not be isolated due to hydrolysis by adventitious oxygen and moisture. Lappert silylated the methyl group of Grévy's ligand, yielding Me3SiN=P(Ph)2CH2SiMe3 (NPC-H2). The methanide form of NPC-H2, i.e.