The Influence of Secondary Interactions on the [N-I-N]+ Halogen Bond.

[Bis(pyridine)iodine(I)]+ complexes offer controlled access to halonium ions under mild conditions. The reactivity of such stabilized halonium ions is primarily determined by their three-center, four-electron [N-I-N]+ halogen bond. We studied the importance of chelation, strain, steric hindrance and electrostatic interaction for the structure and reactivity of halogen bonded halonium ions by acquiring their 15 N NMR coordination shifts and measuring their iodenium release rates, and interpreted the data with the support of DFT computations. A bidentate ligand stabilizes the [N-I-N]+ halogen bond, decreasing the halenium transfer rate. Strain weakens the bond and accordingly increases the release rate. Remote modifications in the backbone do not influence the stability as long as the effect is entirely steric. Incorporating an electron-rich moiety close by the [N-I-N]+ motif increases the iodenium release rate. The analysis of the iodine(I) transfer mechanism highlights the impact of secondary interactions, and may provide a handle on the induction of stereoselectivity in electrophilic halogenations.

The mental health review board: a new concept for difficult clients.

1. The Mental Health Review Board concept is a hospital systems approach to the difficult client. Board membership varies with each case and includes representation from all areas of the hospital. 2. The Review Board deals with clients who have exhausted the system, are threatening or abusive to staff, and noncompliant with treatment recommendations. 3. The Review Board contract is the "final offer" for treatment and is without input from the client. Terms of the contract are nonegotiable. Noncompliance results in discharge and referral elsewhere.