Synthesis and structural investigation of tricarbonylchromium mono-complexes, bis-complexes and tris-complexes of triptindan

The reaction of 9H,10H-4b,9a([1,2]benzenomethano)indeno[l,2-a]indene (triptindan, TRIP) with Cr(CO)6 in Bu2O/THF (9:1) affords a monocomplex (A) together with two bis-Cr(CO)3 complexes (B and C) and one tris-Cr(CO)3 complex (D). The relative yields of the four complexes as well as their tendency to lose Cr(CO)3 are related to stabilizing intramolecular factors. All the Cr(CO)3 units of the complexes A, B, and D are coordinated in the isoclined orientation with respect to the polar axis of the ligand, whereas complex C bears one isoclined and one anticlined Cr(CO)3 unit. The results of X-ray measurements support the hypothesis of weak attractive electronic interactions bonds between the oxygen atoms of the carbonyl groups and polarized faces of benzene rings.