Evaluation of the σ‑Donation from Group 11 Metals (Cu, Ag, Au) to Silane, Germane, and Stannane Based on the Experimental/Theoretical Systematic Approach

Reactions of group 11 metal chlorides
(CuCl, AgCl, AuCl) with {(o-Ph2P)­C6H4}3E­(F) (E = Si (1), Ge
(2), Sn (3)) provide a complete series of
metallasilatrane [{(o-Ph2P)­C6H4}3(F)­Si]­MCl
(E = Cu (4), Ag (5), Au (6)),
metallagermatrane [{(o-Ph2P)­C6H4}3(F)­Ge]­MCl (E = Cu (7), Ag
(8), Au (9)), and metallastannatrane [{(o-Ph2P)­C6H4}3(F)­Sn]­MCl (E = Cu (10), Ag (11), Au (12)) complexes. Structural analyses clearly show the presence
of M→E interactions in all of these complexes and establish
the presence of periodicity; heavier group 14 elements E act as stronger
electron acceptor ligands, and heavier group 11 metals exhibit higher
donor ability toward ER4. Density functional theory calculations
fully support these trends and suggest that σ-acceptor ability
of saturated (four-coordinate) heavier group 14 element compounds
toward group 11 metals is related to σ*­(E–F) molecular
orbital levels, which mainly depend on the deviation of the geometry
around E from tetrahedral geometry to trigonal bipyramidal.