Promoting π-Facial Interactions in Phenyl-Substituted 1,8-Bis(silylamido)naphthalene Alkaline Earth Complexes.

Bimetallic 1,8-bis(silylamido)naphthalene alkaline earth complexes [( L)Ae] ([ L] = [1,8-{(RSi)N}CH)], where R = PhMe, Ae = Ca (), Sr (), and Ba (); R = Ph, Ae = Ca (), Sr (), and Ba () were prepared protonolysis reactions of the phenyl-substituted proligands LH and LH with [AeN″] (N″ = [N(SiMe)]) in benzene. X-ray crystallographic analysis showed that , , and crystallize as nitrogen-bridged dimers. Conversely, and display a naphthalene-bridged motif, while the structure of is intermediate between the two distinct classes. NMR spectroscopic analysis of isolated samples of - in thf- confirmed their conversion into the monomeric thf- adducts [( L)Ae(thf- ) ]; crystallographic verification of the structural motif was provided by the X-ray crystal structure of [( L)Sr(thf)] (). The structural range of dimers - was influenced by the electron-withdrawing nature of the phenyl substituents of the ligand and the ability to form "soft" multihaptic π-facial interactions with the metal ions, which was preferential for the larger Sr and Ba cations as well as the relative strength of the metal-N bonds. This has been rationalized through complementary computational studies. This work provides insight into the structure and bonding preferences of heavy alkaline earth complexes with rigid bis(amido) ligands.