Scandium complexes, carbene

The first example of a group 3 NHC complex was reported by Arduengo et al. in 1994 with yttrium (Scheme 14.1) [12]. The seven-coordinate yttrium carbene complex 1 was obtained from the direct reaction of the free carbene 1,3-dimethyl-4,5-dimethylimidazol-2-ylidene with tris(2,2,6,6-tetramethylheptane-3,5-dionato)yttrium, Y(thd)3 and features a NMR doublet resonance for the carbene atom (d 199.4 ppm) with a coupling constant of 33 Hz to the nucleus. The first scandium NHC complexes were only recently described. Cui and coworkers prepared indenyl-functionaUzed NHC carbene scandium complex 2 in 2007 [13,14]. Complex 2 could be structurally characterized by X-ray... 

Complexes Containing Metal-Carbon a-Bonds of the Groups Scandium to Manganese, Including Carbenes and Carbynes ... 

Sc-P bonds of a four-coordinate scandium phosphinidene complex has been determined (13JA14784). Reactions of electrophilic carbenes with white phosphorus in benzene afforded Pg clusters supported by four carbenes or a carbene—P4 adduct (13CC4486). A mechanistic insight into CO capture by amidophosphoranes which contain a highly reactive P—N bond within a four-membered ring, has been published (13CAJ3147). 

This chapter is devoted to the most significant developments of early-transition metal compounds ligated by N-heterocyclic carbene ligands (from group 3 to group 7 scandium to rhenium) [10]. When appropriate and available, the structural features of these metal complexes will be discussed. The synthetic pathways, bonding nature of the Ccarbene-M> reactivity, and applications of such derivatives (with a special emphasis on their use in catalysis) will be discussed [11]. 

The limited number of RE carbene complexes reported to date have established two principal types of reactivity. Complexes such as (8), the scandium analog of (8), (9), and (10) exhibit metallo-Wittig reactivity with benzophenone via [2 -F 2]-cycloaddition followed by a-bond... 

Reactivity studies on other rare earth methanediide complexes are scarce. Complex [(8a)Nd(8aH)] showed some activity in ring-opening polymerization of rac-lactide [69]. Scandium carbene complex [(7)ScCl(Py)2] has been used as a ligand transfer reagent for the synthesis of a new dimeric, dimetalhc iron complex featuring two bridging methanediide ligands (Scheme 18) [70]. 

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