1,8-Bis(dimethylamino)-2-(4-methoxyphenyl)naphthalene: An electrospray-active analogue for η6-coordinating ligands

1,8-Bis(dimethylamino)-2-(4-methoxyphenyl)naphthalene (1) was synthesized for use as an η6-coordinating ligand with a chargeable tag for ESI-MS analysis. The pKa of the proton sponge moiety was essentially unaffected by addition of the anisole group (pKa = 18.2 ± 0.7 at 297 K in CD3CN). Cr(η6-1)(CO)3 (2) was prepared to demonstrate the utility of (1) as an ESI tag and 2 was easily visible by ESI(+)-MS. A single crystal structure of the complex showed η6-binding of the ligand as expected with the charged moiety being far removed from the metal centre. The gas-phase reactivity of 2 was found to match that of the analogous uncharged chromium carbonyl complex Cr(C6H5OCH3)(CO)3 indicating that 1 has potential as a chargeable tag for the study of organometallic complexes and their reactions by ESI-MS.

Graphical abstractIncorporating a chargeable ESI tag into a standard η6-arene type ligand allows for the investigation of otherwise neutral metal–arene complexes by mass spectrometry.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A chargeable ESI tag was incorporated into a standard η6-arene type ligand. ► Behaviour of the chargeable tag was tested under typical ESI-MS conditions. ► The tag was found to be effective for studying metal–arene complexes by ESI-MS.