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Issue 16, 2016
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Gyroscope like molecules consisting of trigonal or square planar osmium rotators within three-spoked dibridgehead diphosphine stators: syntheses, substitution reactions, structures, and dynamic properties

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Abstract

Reactions of (NH4)2OsX6 (X = Cl, Br) with CO and the phosphines P((CH2)mCH[double bond, length as m-dash]CH2)3 (m = 6, a; 7, b; 8, c) give cis,cis,trans-Os(CO)2(X)2(P((CH2)mCH[double bond, length as m-dash]CH2)3)2 (46–73%). These are treated with Grubbs’ catalyst (7 mol%, 0.0010 M, C6H5Cl). Subsequent hydrogenations (PtO2) yield the gyroscope like complexes cis,cis,trans-Os(CO)2(X)2(P((CH2)n)3P) (n = 2m + 2; X = Cl, 6a–c; Br, 7a–c; 5–31%) and the isomers cis,cis,trans-Os(CO)2(X)2(P(CH2)n−1CH2)((CH2)n)(P(CH2)n−1CH2) (X = Cl, 6′a–c; Br, 7′a–c; 12–51%) derived from a combination of interligand and intraligand metatheses. Reductions of 6a,c, 6′b, and 7′b with C8K under CO atmospheres afford trans-Os(CO)3(P((CH2)n)3P) (9a,c, 79–82%) and trans-Os(CO)3(P(CH2)15CH2)((CH2)16)(P(CH2)15CH2) (9′b, 53–84%). Reaction of 9a and CF3SO3H yields the cationic hydride complex mer,trans-[Os(H)(CO)3(P((CH2)14)3P)]+ CF3SO3 (9a-H+ CF3SO3; quantitative by NMR). Preparative reactions of 9a,c or 9′b and [H(OEt2)2]+ BArf (BArf = B(3,5-C6H3(CF3)2)4) afford 9a,c-H+ BArf (80%) or 9′b-H+ BArf (68%). Reactions of 6a, 6′b, and 7a with MeLi or PhLi give cis,cis,trans-Os(CO)2(Me)2(P((CH2)14)3P) (11a, 98%), cis,cis,trans-Os(CO)2(Me)2(P(CH2)15CH2)((CH2)16)(P(CH2)15CH2) (98%), and cis,cis,trans-Os(CO)2(Ph)2(P((CH2)14)3P) (12a, 58%). NMR data for 6a–c, 7a–c, 9a,c, 9a,c-H+ X, and 11a indicate that rotation of the OsLy moieties is fast on the NMR time scale at room temperature. In contrast, the phenyl groups in 12a act as “brakes” and two sets of 13C NMR signals are observed for the methylene chains (2 : 1). The crystal structures of 6a–c, 7b,c, 7′a, 9a, 9a-H+ BArf, 11a, and 12a are analyzed with respect to OsLy rotation in solution and the solid state.

Graphical abstract: Gyroscope like molecules consisting of trigonal or square planar osmium rotators within three-spoked dibridgehead diphosphine stators: syntheses, substitution reactions, structures, and dynamic properties

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Publication details

The article was received on 22 Feb 2016, accepted on 15 Mar 2016 and first published on 16 Mar 2016


Article type: Paper
DOI: 10.1039/C6DT00692B
Dalton Trans., 2016,45, 7131-7147

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    Gyroscope like molecules consisting of trigonal or square planar osmium rotators within three-spoked dibridgehead diphosphine stators: syntheses, substitution reactions, structures, and dynamic properties

    T. Fiedler, N. Bhuvanesh, F. Hampel, J. H. Reibenspies and J. A. Gladysz, Dalton Trans., 2016, 45, 7131
    DOI: 10.1039/C6DT00692B

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