Abstract
The synthesis and isolation of stable bimetallic complexes that contain formally quintuply bonded transition metals is a novel and emerging field of science. Efforts have been undertaken in designing and tuning the ligands to achieve a very short (actually the shortest) metal-metal bond. The motivation for these efforts arose from the expectation that an increasing bond order may go along with a shortening of the bond length. In consequence, formally quintuply bonded bimetallics could have shorter metal-metal distances than quadruply bonded ones. A chromium homo-bimetallic complex with a Cr-Cr bond length of 1.7293(12) angstrom has been synthesized, and a formal bond order of five was assigned. This compound holds the record for the shortest metal-metal bond in a stable molecule to date. At this stage, there is no evidence that additional shortening is impossible. (C) 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 10: 413-416; 2010: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.201000028