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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Gyroscope like molecules consisting of trigonal or square planar osmium rotators within three-spoked dibridgehead
Tobias Fiedler1, Nattamai Bhuvanesh2, Frank Hampel3
1Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas 77842-3012, USA. gladysz@mail.chem.tamu.edu and Institut für Organische Chemie and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestraße 42, 91054 Erlangen, Germany.
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'ac; 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 (13)C 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.
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