Zero-valent isocyanides of nickel, palladium and platinum as transition metal σ-type Lewis bases.
Transition metal complexes that contain metal-to-ligand retrodative σ-bonds have become the subject of increasing studies over the last decade. Lewis acidic "Z-type ligands" can modulate the electronic structure of their resultant complexes in a manner distinct from 2e-donor ligands, and can also engage in cooperative reactivity with a Lewis basic transition metal. In this Feature article, we summarize our work with transition metal isocyanide complexes of group 10 metals that have exploited metal-based σ-type Lewis basicity. While the complexes Ni(CNArMes2)3, Pd(CNArDipp2)2and Pt(CNArDipp2)2were initially targeted as analogues to unstable, low-coordinate metal carbonyls, it soon became apparent that these zero-valent metal centers bore appreciable Lewis basic qualities due largely to the enhanced σ-donor/π-acid ratio of isocyanides compared to CO. Detailed spectroscopic and structural studies of metal-only Lewis pairs (MOLPs) formed from these complexes have furthered our understanding of the electronic structure perturbations effected by Z-type ligand binding. In addition, the platinum (boryl)iminomethane (BIM) complex Pt(κ2-N,B-Cy2BIM)(CNArDipp2) has illuminated a general ligand design strategy that can engender significant reverse-dative interactions with buttressed Lewis acids, and also has expanded the known scope of cooperative reactivity that can be realized at a transition metal-borane linkage.
Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive MC 0358, La Jolla, California 92093, USA. jsfig@ucsd.edu.
Brandon R
BR
Barnett
Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive MC 0358, La Jolla, California 92093, USA. jsfig@ucsd.edu.
Joshua S
JS
Figueroa