~~The synthesis of 36 [Fe(C0)2L1(q4-diene)], three [Fe(CO)2L'(q4-enone)], and five [Ru(CO),L'(q4-diene)] complexes (L' = Ph,P, Et,P, (EtO),P, (MeO),P, C6HIINC) by thermal, selective CO ligand displacement in the corresponding tricarbonyl precursor complexes is described. In a second step, photochemical CO displacement by another phosphorus ligand L2 leads to a new type of q4-diene complexes with a centre of chirality at the metal atom (Fe, Ru). 23 Fe and three Ru complexes of this type have been prepared and characterized. In the case ofcomplexes with unsymmetrical dienes, racemic diastereoisomers are formed which can be separated by chromatographic methods. The molecular structures of [Fe(CO)(Ph3P)((MeO),P)(buta-l,3-diene)] (52), [Fe(CO)(Ph,P)((MeO),P) (isoprene)] (58) and [Fe(CO)(Et,P)(EtO),P)(hexa-2,4-dienal)] (62a) were determined by X-ray diffraction. AllComplexes were investigated by I3C-, ,'P-and, in part, 'H-NMR spectroscopy. At low temperatures, conformational isomers (rotamers) can be differentiated which probably arise from v/ rotation at the coordinated metal centre.
Enantiomerically enriched (q4-benzylideneacetone)Fe(C0)2(L) complexes (L = trimethoxyphosphine, tributylphosphine) have been obtained by decarbonylation of racemic (q2-benzylideneacetone)Fe(C0)3(L) with brucine N-oxide as the decarbonylating agent. Single-crystal X-ray diffraction has been used to c o n f i i the absolute configuration of ~R)-[Fe(CO)z((MeO)3P)((E)-4-phenylbut-3-en-2-one)] ((-)-3) and (pR)-[Fe(CO),( (Bu3P)((E)-4-phen lbut-3-en-2-one)l ((-)-7). (-)-3 c stallized in the orthorhombic space group P212121 with a = 15.165 (1) 1, b = 15.558 (2) A, c = 7.174 (2)x, and 2 = 4, and (-)-7 crystallized in the same space group with a = 12.036 (1) A, b = 24.087 (2) A, c = 8.609 (1) A, and 2 = 4. Several otherenantiomerically enriched compounds of this type have been obtained by the same method. Moreover, four configurationally pure (q4-enone)Ru(C0),(L) complexes have been prepared either by use of a chiral enone or by substitution via an optically active phosphine. Circular dichroism (CD) spectra of the complexes have been measured, and a general rule for predicting the absolute configuration of (~~-enone)Fe(CO)~(L) and (q4-enone)Ru(C0),(L) complexes is presented. IntroductionMany optically active (q4-diene)iron carbonyl complexes have been prepared and reported in the literature.' In most cases, they have been obtained by classical resolution methods such as separation of diastereomeric derivatives. Other methods have successfully resolved racemic mixtures with good results including stereoselective decomposition with circularly polarized light,lb HPLC separation using a chiral column,lC kinetic resolution via stereoselective allylborat,ion,ld and enzymatic hydrolysis of racemic ester complexes.le Surprisingly, fewer reported examples of optically active (q4-enone)iron carbonyl complexes appear in the literature? even though such complexes have proved to be much more versatile and synthetically useful sources of the Fe(CO), moiety. These complexes, which behave as optically active transfer reagents,2b have also been obtained via classical methods such as complexation with chiral enone ligands, e.g. (+)-pulegone and (+) -pinocarvone followed by separation of the diastereomers.2a-c Diastereocontrolled Fe-(CO), complexation of a simple heterodiene via an adjacent Cr(CO)3-bearing chiral center has also been reported.2d We have recently obtained (q4-benzylideneacetone)Fe(C0)3 (1) highly enriched in one enantiomer by first treating racemic 1 with 1 equiv of (+)-neomenthyldiphenylphosphine, (+)-NMDPP, separating the diastereomers, and then treating a single diastereomer with CO to re-form the tricarbonyl ~omplex.~ Here we present a novel stereoselective decarbonylation of (q2-enone)Fe(C0)3(L) complexes (L = phosphines, phosphites) using a chiral amine oxide
A variety of [Ru(CO)2L(q4-enone)] complexes (L = phosphines, phosphites, and arsines, enone = (E)-4-phenylbut-3-en-2-one) have been synthesized. 'H-, I3C-, and 31P-NMR spectra are reported and the X-ray structures of two Ru complexes with L = Ph3P (7), Et3P (10) and one Fe complex with L = Ph3P (14) are presented.All three compounds crystallize in the same monoclinic space group P2,/n with a = 10.575 (2) The structures of the Ru complexes are compared with the Fe analogues. In the case of M = Ru and L = (EtO),P, (MeO),P, and (i-PrO),P (9, 11, and 13, respectively) stereoisomers could be detected by 31P-NMR at room temperature, which arise from rotation at the coordinated metal centre.
ChemInform Abstract The synthesis of 36 complexes of type (III), three of type (IX) and five of type (XII) by thermal, selective CO ligand displacement in the corresponding tricarbonyl precursors is described as demonstrated for the examples given in the scheme. In a second step, photochemical CO displacement by another phosphorus ligand leads to a new type of η4 complexes with a center of chirality at the metal atom. Twenty-three Fe and 3 Ru complexes of this type such as (V), (VI) and (XIII) are prepared and characterized. In the case of complexes with unsymmetrical dienes, racemic diastereoisomers are formed which can be separated by chromatography. The molecular structures of the compounds (V) and of (VI) are determined by X-ray diffraction (crystallographic data given).
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