Coordination chemistry of 9-sila- and 9-germa-phenanthrenes — unique coordination modes in their metallene complexes

Ligand exchange reactions of 9-sila- and 9-germa-phenathrenes with chromium carbonyl complexes, [Cr(CH3CN)3(CO)3] and [Cr(η6-benzene)(CO)3], were performed. Their reactions with [Cr(CH3CN)3(CO)3] afforded the corresponding η6-complexes, in which Cr(CO)3 moieties coordinated to the C6-rings. However, those with [Cr(η6-benzene)(CO)3] gave unique four-membered complexes bearing semibridging carbonyl ligands. All the structures of novel complexes were determined by NMR and X-ray crystallographic analysis.