Heavier Group 13 Metal(I) Heterocycles Stabilized by Sterically Demanding Diiminophosphinates: A Structurally Characterized Monomer-Dimer Pair For Gallium.

We have synthesized and characterized the monomeric diiminophosphinate-stabilized Group 13 metal(I) complexes [Dip LE:], Dip L=Ph2 P(NDip)2 , Dip=2,6-iPr2 C6 H3 ; E=Ga (1), In (2) and Tl (3). In addition, we structurally characterized the dimeric complex [(Dip LGa)2 ], 12 . Similar synthetic attempts using Mes L=Ph2 P(NMes)2 , Mes=2,4,6-Me3 C6 H2 afforded product mixtures from which the mixed oxidation state species [(Mes L)3 Ga4 I3 ] 4 was isolated. [Dip LGa:] 1 is converted with dry air to the gallium(III) oxide species [(Dip LGaO)2 ] 5. Density Functional Theory studies on [Dip LE:] and [(Dip LE)2 ], E=Al-Tl, shed light on the bonding in these compounds and show that the newly formed E-E bonding interactions can be described as weak single σ-bond with no significant π-bonding contribution for E=Al, Ga. A large contribution to the dimer binding enthalpies results from London dispersion forces.