Dimeric (Tris(<i>tert</i>-butyl)silyl)phosphanyl (Tris(<i>tert</i>-butyl)silyl)phosphanediyl Gallane: A Molecule with a Ga−P−Ga Heteroallyl System

The metathesis reaction of potassium (tris(tert-butyl)silyl)phosphanide with GaCl3 in a molar ratio of 1:1 leads to the formation of [Cl2GaP(H)SitBu3]2 (1) as a mixture of cis and trans isomers with very large 1J(P,H) and 2J(P,P) coupling constants. The molecular structure of 1 shows a Ga2P2 cycle with nearly planar coordinated phosphorus atoms under neglection of the hydrogen atoms and Ga−P distances of 239 pm. The reaction of GaCl3 with 3 equiv of potassium (tris(tert-butyl)silyl)phosphanide as well as the reaction of 1 with 2 equiv of KP(H)SitBu3 yields [tBu3SiP(H)Ga(μ-PSitBu3)]2 (2). The central moiety comprises a four-membered Ga2P2 cycle with one planar P atom and extremely short Ga−P bonds of approximately 226 pm, the other being in a pyramidal environment with an angle sum of 298.4°. The structure of 2 can be described as a GaPGa heteroallyl system which is bonded to a phosphanidyl substituent. This idea and its dependency on the steric demand of the trialkylsilyl groups are investigated by DFT calculations on different isomers of 2.