Hetero-carbolong chemistry: experimental and theoretical studies of diaza-metallapentalenes.

Four diaza-osmapentalenes were prepared by two-step reactions, through the treatment of an alkyne-coordinated osmium complex with azo compounds, followed by the addition of AgSbF 6 /CO. Their aromaticity was confirmed by crystal parameters, NMR spectra and theoretical calculations. These complexes are the first diaza-metallapentalenes representing a new class of metallaaromatics.