Imido complexes solid state structure

In 2011, Cramer and Jenkins synthesised dicationic octahedral Fe" complex 10 that featured a macrocyclic tetracarbene ligand and two molecules of acetonitrile in its solid-state structure. This compound, reminiscent of an iron porphyrin, catalysed the aziridination of simple di-, tri-, and even tetrasubsti-tuted alkenes and cycloalkenes with aryl azides [eqn (7.8)]. The reaction most likely proceeded via the intermediacy of a highly reactive Fe imido species. 

To date, no terminal unsupported Ln-imido complexes, Ln=NR, (Ln=Ce-Lu) have been isolated and characterized in the solid state, despite the comparative fertility of this area for related early TMs [83]. Structurally authenticated Ln-imido and -phos-phinidene complexes in the literature, typically prepared by the deprotonation of Ln—NHR and Ln—PHR precursors, form dimers in the solid state with bridging NR and PR fragments [84]. It is noteworthy that the transient existence of unsupported Ln=NR and Ln=PR linkages had previously been observed, though could not be isolated [95]. In the case of the RE, the first terminal Sc-imido complex, [Sc(=NDipp)(T -NacNac-K -A, A, A ")(DMAP)] (T -NacNac = (N(Dipp)C(Me) CHC(Me)N(CH2CH2NMe2) DMAP = 4-dimethylaminopyridine, 45), was recently prepared, which is stabilized by a bespoke tri-coordinate variant of the ubiquitous NacNac ligand [96]. 

In THE solution, lithium diphenyl phosphide exists as [Li(THF)4]+[PPh2], whereas in Et20 solution it is dimeric [64], and in the solid state probably polymeric as (8.46c). In [Li(12-crown-4)]+[PPh2] the Li+ cation is completely enclosed by the crown ether, allowing a free phosphide anion to exist in the crystal structure (8.46d). A similar discrete phosphide anion is found in the pyridyl phosphide (8.46e) and in (8.46g). Lithium forms covalent-type complexes with imido analogues of P oxo-anions (Chapter 7.4). 

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