Octahedral Gyroscope-like Molecules Consisting of Rhenium Rotators within Cage-like Dibridgehead Diphosphine Stators: Syntheses, Substitution Reactions, Structures, and Dynamic Properties
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Reactions of Re(CO)5(X) (X = Cl, Br) or [Re2(CO)4(NO)2(μ-Cl)2(Cl)2] and the phosphines P((CH2)mCH═CH2)3 (m = 6, a; 7, b; 8, c) give mer,trans-Re(CO)3(X)(P((CH2)mCH═CH2)3)2 (53-95%) or cis,trans-Re(CO) (NO) (Cl)2(P((CH2)6CH═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 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 e(CO)(NO)(Cl)2(P((CH2)14)3 P) (14%), respectively, and/or the isomers mer,trans-R e(CO)3(X)( P(CH2)n-1 CH2)((CH2)n)( 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 e(CO)3(X)(P((CH2)14)3 P) (X = I, 11a; Ph, 12a; Me, 13a; 34-87%). The 13C 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 °C for 8a). In contrast, the phenyl group in 12a acts as a brake, and two sets of 13C 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.
author list (cited authors)
Hess, G. D., Fiedler, T., Hampel, F., & Gladysz, J. A.