Organometallic Osmium(II) and Ruthenium(II) Biphenyl Sandwich Complexes: X‐ray Crystal Structures and ¹⁸⁷Os NMR Spectroscopic Studies in Solution

Abstract

Abstract We report the synthesis of the ruthenium(II) and osmium(II) organometallic sandwich complexes [Ru(η 6 ‐bip) 2 ](OTf) 2 ( 1 ) and [Os(η 6 ‐bip) 2 ](OTf) 2 ( 2 ) containing biphenyl (bip) as the arene ligand, and the X‐ray crystal structures of 1· MeOH and 2 . The unit cell of the osmium complex contains molecules in which the unbound phenyl ring of the biphenyl ligands exists in both staggered and eclipsed configurations, whereas for the ruthenium complex the rings are only eclipsed. Both crystal structures possess CH/π and π–π stacking interactions. 187 Os (nuclear spin 1/2, natural abundance of 1.64 %) has a very low gyromagnetic ratio and is one of the most insensitive nuclei in the periodic table. We show that inverse NMR spectroscopic detection by the use of 1 H/ 187 Os heteronuclear multiple bond correlation (HMBC) spectroscopy allows the ready observation of the 187 Os resonance of complex 2 via couplings to arene ring protons. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)