Observing a Homogeneous Ziegler Catalyst Precursor at Work: Insertion Reactions into the Zirconium – Carbon Bond of the (Butadiene)ZrCp2/B(C6F5)3 Addition Product

The Coordination Chemistry of Fluorocarbons: Difluoro-m-cyclophane-Based Fluorocryptands and Their Group I and II Metal Ion Complexes

The reactions of 1,3-bis(bromomethyl)-2-fluorobenzene with the bis(trifluoroacetamides) of 1,3-bis(aminomethyl)-2-fluorobenzene and 1,3-bis(aminomethyl)benzene yield the respective 1+1-condensed [3.3]-m-cyclophanes, respectively termed F(2)-phane (yield 39%) and HF-phane (yield 48%) without trifluoroacetamide groups. The reactions of F(2)-phane with 1,8-diiodo-3,6-dioxaoctane and 1,11-diiodo-3,6,9-trioxaundecane result in the respective 1+1-addition products 1,10-diaza-25,26-difluoro-4,7-dioxatetracyclo[8.7.7.1(12,16).1(19,23)]hexaeicosa-12,14,16(25),19,21,23(26)-hexene (= F(2)-[2.1.1]-cryptand) (yield 5%) and 1,13-diaza-28,29-difluoro-4,7,10-trioxatetracyclo[11.7.7.1(15,19).1(22,26)]nonaeicosa-15,17,19(28),22,24,26(29)-hexene (= F(2)-[3.1.1]-cryptand) (yield 39%). Analogous reactions of the HF-phane give the related macrocycles HF-[2.1.1]-cryptand (yield 68%) and HF-[3.1.1]-cryptand (yield 76%). The coordination of alkali and alkaline earth metal ions by these fluorophane cryptands results in significant shifts of the (19)F NMR resonances: F(2)-[2.1.1]-cryptand, delta -100.70 ppm; its Li(+) complex, delta -129.23 ppm. The (1)J(CF) coupling constant for such complexes is correlated with the degree of interaction between CF units and metal ions, and the most pronounced decrease (262 Hz to 232 Hz) is found for the lithium complex of the F(2)-[2.1.1]-cryptand. Competition experiments show the difluoro F(2)-[3.1.1]-cryptand to form significantly stronger complexes with Na(+) than the monofluoro HF-[3.1.1]-cryptand. In the crystal structure of F(2)-[2.1.1]-cryptand.NaCF(3)SO(3), the sodium ion displays an unusual F(2)O(4)N coordination sphere with extremely short sodium-fluorine distances: CF.Na(+) = 229.8(3), 235.7(4) pm; O-Na(+) = 228.5(4), 242.0(4), 243.8(4), 247.6(4) pm; N-Na(+) = 285.1(7) pm. In the closely related crystal structure of HF-[3.1.1]-cryptand.NaClO(4), the metal has an FO(5)N coordination sphere: CF.Na(+) = 236.0(4) pm; O-Na(+) = 234.8(6), 239.3(6), 240.3(12), 240.6(6), 285.7(17) pm; N-Na(+) = 272.3(6) pm. In the crystal structure of F(2)-[3.1.1]-cryptand.HCF(3)SO(3), the proton is in a pseudotetrahedral environment: N-H = 84 pm; O.HN = (216 pm; CF.HN = 224, 236 pm. This, however, is not considered indicative of significant CF.HN hydrogen bonding.