Octahedral Gyroscope-like Molecules Consisting of Rhenium Rotators within Cage-like Dibridgehead Diphosphine Stators: Syntheses, Substitution Reactions, Structures, and Dynamic Properties

Reactions of Re(CO)(5)(X) (X = Cl, Br) or [Re-2(CO)(4)(NO)(2),(mu-Cl)(2)(Cl)(2)] and the phosphines P((CH2)(m)CH=CH2)(3) (m = 6, a; 7, b; 8, c) give mer,trans-Re(CO)(3) (X)(P((CH2)(m)CH=CH2)(3))(2) (53-95%) or cis,trans-Re(CO) (No) (Cl)(2)(P((CH2)(6)CH=CH2)(3))(2) (57%), respectively. Additions of Grubbs' catalyst (5-10 mol %, 0.0010-0.0012 M) and subsequent hydrogenations (PtO2, <= 5 bar) yield the gyroscope-like complexes mer,trans-R(sic)e(CO)(3)(X)(P- ((CH2)(n))(3)P) (n = 2m + 2; X = Cl, 7a,c; Br, 8a,c; 18-61%) or cis,trans-R(sic)e(CO)(NO)(Cl)(2)(P((CH2)(14))(3)P) (14%), respectively, and/or the isomers mer,trans-R(sic)e(CO)(3)(X)((sic)P(CH2)(n-1)CH2)((CH2)(n))((sic)P(CH2)(n-1)CH2) (X = Cl, 7' a-c; Br, 8'b; 6-27%). The latter are derived from a combination of interligand and intraligand metatheses. Reactions of 7a or 8a with NaI, Ph2Zn, or MeLi give mer,trans-R(sic)e(CO)(3)(X)(p((CH2)(14))(3)P) (X = I, 11a; Ph, 12a; Me, 13a; 34-87%). The C-13 NMR spectra of 7a-c, 8a-c, 11a, and 13a show rotation of the Re(CO)(3)(X) moieties to be fast on the NMR time scale at room temperature (and at -90 degrees C for 8a). In contrast, the phenyl group in 12a acts as a brake, and two sets Of C-13 NMR signals (2:1) are observed for the methylene chains. The crystal structures of 7a, 8a, 12a, and 13a are analyzed with respect to Re(CO)(3)(X) rotation in solution and the solid state.