Isocyanide and Phosphine Oxide Coordination in Binuclear Chromium Pacman Complexes.

Charlotte J Stevens,Polly L Arnold,Jason B Love,Gary S Nichol

doi:10.1021/om4009313

Abstract

The new binuclear chromium Pacman complex [Cr2(L)] of the Schiff base pyrrole macrocycle H4L has been synthesized and structurally characterized. Addition of isocyanide, C≡NR (R = xylyl, tBu), or triphenylphosphine oxide donors to [Cr2(L)] gives contrasting chemistry with the formation of the new coordination compounds [Cr2(μ-CNR)(L)], in which the isocyanides bridge the two Cr(II) centers, and [Cr2(OPPh3)2(L)], a Cr(II) phosphine oxide adduct with the ligands exogenous to the cleft.

Highlights

Group, late-transition-metal, lanthanide, and actinide complexes of these macrocycles have been synthesized,[8] of which cobalt complexes were found to be effective as catalysts for the reduction of dioxygen to water.[9]
Isocyanide ligands C NR are isoelectronic with carbon monoxide but are better σ donors and generally poorer π acceptors.[15]
One of the protons bound to C7 is oriented toward the electron-rich π system of the isocyanide ligand (C7··· C44 = 3.349(3) Å, C7···N9 = 3.568(3) Å) indicating that intramolecular hydrogen bonding occurs, similar to that seen in the related complex [Cu2(μ-py)(L)]

Summary

Introduction

Group, late-transition-metal, lanthanide, and actinide complexes of these macrocycles have been synthesized,[8] of which cobalt complexes were found to be effective as catalysts for the reduction of dioxygen to water.[9]. The new binuclear chromium complex of the Pacman macrocycle [Cr2(L)] can be prepared either by addition of [Cr{N(SiMe3)2}2(THF)2] to H4L or by reaction of K4L with CrCl2 (Scheme 1).

Results

Conclusion