An N‐Heterocyclic Boryloxy Ligand Isoelectronic with N‐Heterocyclic Imines: Access to an Acyclic Dioxysilylene and its Heavier Congeners

New O‐donor ligand: By exploiting the isoelectronic relationship with N‐heterocyclic imines (NHIs), a new class of N‐heterocyclic boryloxy (NHBO) ligand, which is a strong O‐donor, is introduced. The NHBO ligand is used to generate the first acyclic two‐coordinate dioxysilylene and its heavier (Ge, Sn, Pb) congeners, which represent the first complete series of heavier group 14 dioxycarbene analogues.

Abstract

Introduced here is a new type of strongly donating N‐heterocyclic boryloxy (NHBO) ligand, [(HCDippN)₂BO]⁻ (Dipp=2,6‐diisopropylphenyl), which is isoelectronic with the well‐known N‐heterocyclic iminato (NHI) donor class. This 1,3,2‐diazaborole functionalized oxy ligand has been used to stabilize the first acyclic two‐coordinate dioxysilylene and its Ge, Sn, and Pb congeners, thereby presenting the first complete series of heavier group 14 dioxycarbene analogues. All four compounds have been characterized by X‐ray crystallography and density‐functional theory, enabling analysis of periodic trends: the potential for the [(HCDippN)₂BO]⁻ ligand to subtly vary its electronic‐donor capabilities is revealed by snapshots showing the gradual evolution of arene π coordination on going from Si to Pb.

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