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

The deep-red, air-stable mixed-metal metallocryptands, [AuPdTl(P2phen)3](PF6)2, 1·(PF6)2, and [AuPtTl(P2phen)3](PF6)2, 2·(PF6)2, are easily prepared in good yield (60−70%) by reacting 3 equiv of P2phen with 1 equiv of Au(THT)Cl, excess thallous acetate, and the appropriate amount of either Pd2(dba)3 for 1 or Pt(dba)2 for 2 in acetonitrile where P2phen 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.