Ambiphilic Behavior of Ge(II)-Pseudohalides in Inter- and Intramolecular Frustrated Lewis Pair Alkyne Addition Reactions.

The reaction of the germylene chloride (NacNac)GeCl (, NacNac = CH{(CMe)(2,6-PrCHN)}), phenylacetylene, and B(CF) gives the intermolecular frustrated Lewis pair (FLP) addition product . In this case, the Ge(II) center acts as a base. In contrast, the analogous reaction of germylene thiocyanate reacts independently with B(CF) to give the germylene cation salt [(NacNac)Ge][SCNB(CF)] . Subsequent in the presence of alkynes, the Ge(II) cation and γ-C of act as a Lewis acidic and basic center, respectively, to affect the addition of alkynes, affording products [(NacNac)Ge(RCCR')][SCNB(CF)] and . Compound also reacts with MeSiCN to give the cyanide-bridged Ge/B species , which also reacts with phenylacetylene to give CN abstraction and intramolecular addition yielding the salt [(NacNac)Ge(PhCCH)][NCB(CF)] . Despite the similarity of and , DFT calculations show that the highest occupied molecular orbital (HOMO) of is mainly located at the more sterically hindered germylene center, while the HOMO of is located on the less sterically hindered NCS group, prompting markedly different FLP addition products.