Mixed-Metal Metallocryptands. Short Metal−Metal Separations Strengthened by a Dipolar Interaction

2004-06-02T00:00:00Z (GMT) by Vincent J. Catalano Mark A. Malwitz
The deep-red, air-stable mixed-metal metallocryptands, [AuPdTl(P<sub>2</sub>phen)<sub>3</sub>](PF<sub>6</sub>)<sub>2</sub>, <b>1</b>·(PF<sub>6</sub>)<sub>2</sub>, and [AuPtTl(P<sub>2</sub>phen)<sub>3</sub>](PF<sub>6</sub>)<sub>2</sub>, <b>2</b>·(PF<sub>6</sub>)<sub>2</sub>, are easily prepared in good yield (60−70%) by reacting 3 equiv of P<sub>2</sub>phen with 1 equiv of Au(THT)Cl, excess thallous acetate, and the appropriate amount of either Pd<sub>2</sub>(dba)<sub>3</sub> for <b>1</b> or Pt(dba)<sub>2</sub> for <b>2</b> in acetonitrile where P<sub>2</sub>phen is 2,9-bis(diphenylphosphino)-1,10-phenanthroline, THT is tetrahydrothiophene, and dba is dibenzylidineacetone. Compared to the more symmetrical bimetallic metallocryptands, these trimetallic species show shorter than expected Au(I)−Tl(I), Pt(0)−Tl(I), and Pd(0)−Tl(I) separations. The enhanced bonding interaction is attributed to the incorporation of the dissimilar capping metals introducing dipole moments that strengthen the dispersion forces responsible for maintaining the metallophilic interactions.