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(-Cl)2(Cl)2] and the phosphines P((CH2)mCHCH2)3 (m = 6, a; 7, b; 8, c) give mer,trans-Re(CO)3(X)(P((CH2)mCHCH2)3)2 (53-95%) or cis,trans-Re(CO) (NO) (Cl)2(P((CH2)6CHCH2)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.
