title: η6-Cycloparaphenylene transition metal complexes: synthesis, structure, photophysical properties, and application to the selective monofunctionalization of cycloparaphenylenes.
abstract: The synthesis, structure, photophysical properties, and reactivity of cycloparaphenylenes (CPPs) coordinated to group 6 transition metal fragments are described. The η(6)-coordination of [9]CPP or [12]CPP with M(CO)6 (M = Cr, Mo, W) afforded the corresponding [n]CPP-M(CO)3 complexes (n = 9, 12; M = Cr, Mo, W). In the (1)H NMR spectra of these complexes, characteristic upfield-shifted singlet signals corresponding to the four hydrogen atoms attached to the coordinated C6H4 ring of the CPPs were observed at 5.4-5.9 ppm. The complex [9]CPP-Cr(CO)3 could be successfully isolated in spite of its instability. X-ray crystallographic analysis and computational studies of [9]CPP-Cr(CO)3 revealed that chromium-CPP coordination occurs at the convex surface of [9]CPP both in the solid state and in solution. TD-DFT calculations suggested that the emerging high-wavenumber absorption peak upon coordination of [9]CPP to Cr(CO)3 should be assigned to a weak HOMO-LUMO transition. Moreover, by using the complex [9]CPP-Cr(CO)3, a rapid and highly monoselective CPP functionalization has been achieved. The established one-pot method, consisting of complexation, deprotonation, nucleophilic substitution, and decomplexation steps, yielded silyl-, boryl-, and methoxycarbonyl-substituted CPPs in up to 93% yield relative to reacted starting material.
authors.affiliation: Graduate School of Science, Nagoya University , Chikusa, Nagoya 464-8602, Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Kubota
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Segawa
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Itami
mesh_terms: D001555:Benzene Derivatives / Q000138:chemical synthesis / Q000737:chemistry*; D001952:Bridged-Ring Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D055668:Photochemical Processes; D011789:Quantum Theory; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D001952:Bridged-Ring Compounds; D009942:Organometallic Compounds; D028561:Transition Elements