American Chemical Society
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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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journal contribution
posted on 2017-06-09, 17:48 authored by Gisela D. Hess, Tobias Fiedler, Frank Hampel, John A. Gladysz
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-Re­(CO)3(X)­(P­((CH2)n)3P) (n = 2m + 2; X = Cl, 7a,c; Br, 8a,c; 18–61%) or cis,trans-Re­(CO)(NO)(Cl)2(P­((CH2)14)3P) (14%), respectively, and/or the isomers mer,trans-Re­(CO)3(X)­(P­(CH2)n−1CH2)­((CH2)n)­(P­(CH2)n−1CH2) (X = Cl, 7′ac; 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-Re­(CO)3(X)­(P­((CH2)14)3P) (X = I, 11a; Ph, 12a; Me, 13a; 34–87%). The 13C NMR spectra of 7ac, 8ac, 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.