Insights into Frustrated and Regular peri-Substituted (Ace-)Naphthylaminoboranes and (Ace-)Naphthylphosphinoboranes

Four peri-substituted acenaphthylphosphinoboranes 5-Ph2P-Ace-6-BRR' (R = R' = H; R = H, R' = C6F5; R = Cl, R' = C6F5; R = R' = C6F5), possessing functionality at the B atoms, were prepared and fully characterized. A quantum-chemical analysis of these and previously known (ace-)naphthylaminoboranes and (ace-)naphthylphosphinoboranes revealed that these compound classes can be divided into three subclasses, namely: regular Lewis pairs (LPs) with predominately attractive peri interactions; frustrated Lewis pairs (FLPs) with predominately repulsive peri interactions; and regular Lewis pairs with predominately repulsive peri interactions. The latter subclass is a straightforward example of the enforced proximity donor concept. A detailed bond analysis showed no principal difference between attractive and enforced B-P bonds in (ace-) naphthylphosphinoboranes.