Beryllium carbene complexes

Figure 8 The structure of the beryllium carbene complex [(1,3-Me2-C3N2H2)3BeCI]+CI 19.

Nucleophilic carbene 4 (R = Me, R = H) has been shown to disrupt the polymeric structure of beryllium dichloride to form an ionic carbene complex, 10 (15). The crystal structure of 10 revealed that the cation possesses a distorted tetrahedral coordination geometry at the beryllium center. The average Be-Cl bond distance (2.083(7) A) is... 

That this is so can be seen from the investigation of some beryllium NHC complexes [13,134] where the carbene was seen to replace bridging chloride hgands and coordinate to the Be cation despite the lack of suitable electrons for jt-backbonding on the beryllium atom. 

The reaction of polymeric beryllium chloride (BeCl2) with nucleophilic carbene (1) (R = Me, R = H) is reported (equation 2) to yield a cationic carbene complex (10). The structure of the cation in (10) consists of the beryllimn center adopting a distorted tetrahedral coordination. Although... 

The metal-donor bonds are predominantly ionic and become more labile for calcium, strontium, and barium compared to beryllium and magnesium. The solubility and stability of the complexes decrease from calcium to barium. The 1 1 adducts of NHCs with BH3 or BF3 (28 and 29) are thermally stable and can be sublimed without decomposition. This is in sharp contrast to the properties of conventional carbenes, which rely on a pronounced metal-to-ligand back donation and are, thus, not suited to forming adducts with electron-poor fragments such as... 

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