Synthesis and Reactivity of Germyl-Substituted Gallapnictenes

Abstract

Decarbonylation of the phospha- and arsaketenyl germylenes (L)GeECO (E = P, As; L = CH[C(Me)NAr]₂, Ar = 2,6-iPr₂C₆H₃) in the presence of the Ga(I) precursor (L)Ga afforded the corresponding germyl-substituted gallaphosphene 1 and gallaarsene 3, respectively. Both 1 and 3 are examples of unsaturated chains with heavier group 13/15/14 elements. The germylene center and the polarized Pn = Ga (Pn = P or As) double bond provide multiple sites for small-molecule activation. For example, gallaarsene 3 reacted with adamantyl azide in a formal [3 + 2]-cyclization to give 4 containing a GaAsN₃ heterocycle, clearly underlining the analogy between the As = Ga and C–C multiple bonds. By contrast, the reaction of 3 with Me–I afforded the 1,3-addition product 5, which indicates frustrated Lewis pair character in 3. DFT calculations indicate that the Ga–P/As bonds are highly polarized toward the pnictogen center. EDA-NOCV calculations further support this description and additionally shed light on ambiguous bonding scenarios in 4 and 5. These calculations prove that orbital interactions are outweighed by electrostatic interactions, resulting in polar bonds with significant ionic character.