First hyperpolarizabilities of manganese(I)-chromium(0) sesquifulvalene complexes

The synthesis of monometallic manganese and bimetallic manganese-chromium c omplexes incorporating the sesquifulvalene derivatives 2-(2,4,6-cycloheptat rien-2-ylidene)indene (VI) and [(2,4,6-cycloheptatrien-1-ylidene)ethenyl-id ene]cyclopentadiene (VII) is reported. Charge separation is observed upon c omplexation and stabilization of VI and VII by metal centers, and the spect roscopic and structural properties of [(VI)Mn(CO)(3)]BF4 (6), [(OC)(3)Mn(mu -VI)Cr(CO)(3)]BF4 (8), [(VII)Mn(CO)(3)]BF4 (13), and [(OC)(3)Mn(mu-VII)Mn(C O)(3)]BF4 (15) are clearly indicative of sesquifulvalene ligands coordinate d in a dipolar eta(5) or mu-eta(5):eta(7) fashion, respectively. The coplan ar cyclopentadienyl and cycloheptatrienyl fragments act as strongly coupled electron-donating and -accepting groups and strong negative solvatochromis m is observed for complexes 6, 8, 13, and 15. Accordingly, exceptionally la rge first molecular hyperpolarizabilities beta have been determined by mean s of hyper Raleigh scattering for the bimetallic species 8 and 15, as well as for some related compounds. The X-ray crystal structures of anti-[(OC)(3 )Mn(mu-eta(5):eta(7)-VI)Cr(CO)(3)] (8) and syn-[(OC)(3)Mn(mu-eta(5):eta(7)- VI)Cr(CO)(3)] (15) are reported.