Monomeric, early-transition-metal imide complexes [M = NR], which mediate numerous catalytic and stoichiometric nitrogen-transfer reactions, [1a] can be prepared by a abstraction and extrusion of a good leaving group (e.g. alkane or amine) from a metal amide species [X À M À NHR].[1] These aabstraction reactions are thought to be concerted, [1] but in a hypothetical stepwise process, a potential intermediate is an imidate complex [MÀNR] À [Eq.(1)]. The ease with which such imidate species can be observed and isolated depends upon the absence of a good leaving group on the metal and on the acidity of the N À H proton. There are few reports of such deprotonation reactions in the literature; [2] the resultant imidates are either stabilized by adjacent conjugating groups [2a-c] or readily undergo subsequent reactions, thus preventing their structural characterization.[2d] We report herein the formation and structural characterization of monomeric, nonconjugatively stabilized lithium zirconocene imidate complexes.In our ongoing studies on early-metal imide complexes, we became interested in preparing a series of substituted zirconocene methyl amide complexes as precursors to imidozirconocene complexes.[1] In systems with relatively small ancillary ligands on zirconium, such as Cp*Cp (Cp = h 5 -C 5 H 5 , Cp* = h 5 -C 5 Me 5 ), methyl amide complexes such as 2 a could be accessed through salt metathesis [Eq. (2)]. When [Cp* 2 Zr(Me)(Cl)] (1 b) was subjected to the same reaction conditions, however, incomplete consumption of 1 b and a mixture of two new products were observed (75 % conversion based on 1 b). These products were tentatively assigned as methyl amide complex 2 b (48 % conversion based on 1 b) and lithium zirconimidate complex 3 b (27 % conversion based on 1 b). Upon addition of a second equivalent of tBuNHLi, only complex 3 b was observed and subsequently isolated in 74 % yield (Scheme 1).The identity and structural features of complex 3 b were elucidated by NMR spectroscopy and X-ray crystallography. The 1 H NMR spectrum of complex 3 b lacks a diagnostic N À H peak, and the zirconium methyl signal is shifted upfield (d = À0.75 ppm) relative to the corresponding signal in complex 2 b (d = À0.19 ppm). Further 7 Li-13 C and 6 Li-1 H NMR correlation experiments yielded measurable coupling constants (12 Hz [3] and 2.3 Hz, respectively), thus indicating that the {Me À Li} fragment is intact in solution.X-ray crystallography revealed that the atoms comprising the metallacycle (Zr-N-Li-C) are coplanar (Figure 1).[4] The ZrÀC bond length of 2.36 is consistent with a ZrÀC single bond, [5] and the positions of the hydrogen atoms on C1 were calculated. The Zr À N bond length (r ZrÀN ) of 1.91 indicates a high bond order, suggesting that zirconimidate 3 b could be an intermediate structure between a zirconocene amide (r ZrÀN = 2.05-2.08 , R = alkyl) [6] and a zirconocene imide (r Zr=N = 1.85-1.88 , R = alkyl).[1b] Both NMR spectroscopic and crystallographic data indicate a bond between the {ZrÀCH 3 } moiety and ...