Charge-assisted hydrogen bonding and other noncovalent interactions in the self-assembly of the organometallic building block [(η6-hydroquinone)Rh (P(OPh)3)2]+ with a range of counteranions

The synthesis and X-ray structures are reported for [(eta(6)-hydroquinone)Rh(P(OPh)(3))(2)]X-+(-)(X = BF4, ClO4, SbF6, OTf, OTs, OPf), [(eta(6)-resorcinol)Rh(P(OPh)(3))(2)]+BF4-, and [(eta(6)-4,4'-biphenol) Rh(P(OPh)(3))(2)]+BF4-. In these complexes, the -OH groups are activated by the electrophilic rhodium moiety to participate in charge-assisted hydrogen bonding to the anionic counterion. The crystal structures feature three kinds of noncovalent interactions-hydrogen bonding, Coulombic attraction, and pi-pi stacking, which result in an intriguing array of architectures: dimeric, 1-D chain, C-2 helical, and C-3 helical. The nature of the charge-assisted hydrogen bonding and the resulting 3-D structure in these systems are remarkably dependent on the identity of the anion. Robust porous networks are formed rapidly (minutes or less) with [(eta(6)-hydroquinone) Rh(P(OPh)(3))(2)](+) X- (X = BF4, ClO4) and [(eta(6)-resorcinol)Rh(P(OPh)(3))(2)](+) BF4-. The hydrophobic pores in [(eta(6)-hydroquinone)Rh(P(OPh)(3))(2)](+) ClO4- bind toluene reversibly. This work demonstrates that self-assembly of well-designed organometallic building blocks via charge-assisted hydrogen bonding is an effective strategy for the construction of robust porous networks. With counterions containing both oxygen and fluorine, it was found that the former is invariably the hydrogen bond acceptor, a result in agreement with atomic charge calculations. It is anticipated that self-assembly via charge-assisted hydrogen bonding is an approach applicable in many organometallic systems.