Chromium-amine complexes

Unlike the corresponding 1 1 chromium complexes, the stability of 1 1 cobalt-dye complexes is inadequate for them to be obtained in acceptable yield at low pH. However, advantage can be taken of the strong affinity for cobalt ions of ammonia or amines as... 

The chromium complexes of some azomethine derivatives are used as solvent dyes. Cl Solvent Yellow 32 (6.231) is an example, obtained by condensing one mole of salicyl-aldehyde with the appropriate amine, followed by treatment with one equivalent of chromium. 

The reaction is catalyzed by a group VIII metal species, particularly that of rhodium or palladium. The initial metal species may be any variety of complexes (e.g., PdCl2 Pd acetate, etc.). A source of halide is necessary iodide is especially effective. The most convenient source is methyl iodide, since it is likely a reaction intermediate. In addition, an organic promoter must be included for catalytic activity. These promoters are generally tertiary phosphines or amines. Also, chromium complexes were found to have an important promotional effect. 

Some further examples of stereoselective deprotonation/alkylation reactions of tricarbonyl-chromium complexed (V-methyl tetrahydroisoquinolines have been reported27. Starting with the enantiomerically pure (35)-methyl tetrahydroisoquinoline reaction with hexacarbonyl-chromium led to a mixture of endo- (40%) and exo- (60%) complexes, which were deprotonated with butyllithium and subsequently methylated with iodomethane. In this way methylation occurred firstly at the 4- and secondly at the 1-position. In all cases, the methyl group entered anti to the chromium complexed face. After separation of the alkylated complexes by chromatography and oxidative decomplexation, the enantiomerically pure diastereomers (—)-(l 5,35,47 )-and ( + )-(17 ,35,45)-1,2,3,4-tetrahydro-l,2,3,4-tetramethylisoquinolme were obtained, benzylic amines such as tetrahydroisoquinoline to 2-amino-4,5-dihydrooxazoles. Deprotona... 

The three different tetranuclear structures which have been observed in the crystalline state are the two compact structures 6 and 8 and the chain structure 7a. Structure 6 is found in [Co4(NH3),2(OH)6]C16-8H20 and its amine analogs (52 59). The analogous ammonia and ethylenediamine chromium(III) complexes Cr4(NH3)12(OH)66+ and Cr4(en)6(0H)66+ have been characterized quite recently (40, 41, 42, 60). Structure 7a has so far been observed (42) only in a chromium(III) amine complex, Cr4(en)6(OH)66+, but, as discussed in Section IV, both structures 7b and 7c are possible structures for the tetranuclear aqua chromium(III) species. Structure 8 is known from the so-called rhodoso complex, Cr4N12(OH)66+ [N12 = (NH3)12 or (en6] (61, 62). 

Bis(phosphoranimine) ligands, chromium complexes, 5, 359 Bis(pinacolato)diboranes activated alkene additions, 10, 731—732 for alkyl group functionalization, 10, 110 alkyne additions, 10, 728 allene additions, 10, 730 carbenoid additions, 10, 733 diazoalkane additions, 10, 733 imine additions, 10, 733 methylenecyclopropane additions, 10, 733 Bisporphyrins, in organometallic synthesis, 1, 71 Bis(pyrazol-l-yl)borane acetyl complexes, with iron, 6, 88 Bis(pyrazolyl)borates, in platinum(II) complexes, 8, 503 Bispyrazolyl-methane rhodium complex, preparation, 7, 185 Bis(pyrazolyl)methanes, in platinum(II) complexes, 8, 503 Bis(3-pyrazolyl)nickel complexes, preparation, 8, 80-81 Bis(2-pyridyl)amines... 

An alternative procedure starts from a metal complex of o-phenylenedi-amine. For example, the bis(o-phenylenediamine) complex of nickel(II) chloride reacts with acetylacetone to give a mixture of a nickel complex of the diamine and diketone together with 2,4-dimethylbenzodiazepinium chloride (76CPB1934 91JPR327). Chromium complexes have been used in the same way [91JCS(D)2045]. 

Other ligands giving >90% ee for the alkylation or amination of 19 have been reported but will not be described in detail. They include derivatives of 3 [36], ferrocene-based ligands [54-57], l.l -binaphthyl-based ligands [58-60], natural product-based ligands such as fenchone [61], cholesterol [62], or carbohydrates [63,64], chiral aryl chromium complexes [65,66], chiral sulfimides [67], newP,N-ligands [19,22,52,53,68-78], and others [79-82]. 

REDUCTION, REAGENTS Bis(triphenyl-phosphine)copper tetrahydroborate. Borane-Pyridine. Calcium-Methylamine/ ethylenediaminc. Chlorobis(cyclopenta-dienyl)tetrahydroboratozirconium(IV). Chromium(II)-Amine complexes. Copper(0)-lsonitrile complexes. 2,2-Dihydroxy-l, 1-binaphthyl-Lithium aluminum hydride. Di-iododimethylsilane. Diisobutyl-aluminum 2,6-di-/-butylphenoxide. Diisobutyl aluminum hydride. Dimethyl sulfide-Trifluoroacetic anhydride. Disodium tetracarbonylferrate. Lithium-Ammonia. Lithium-Ethylenediamine. Lithium bronze. Lithium aluminum hydride. Lithium triethylborohydride. Potassium-Graphite. 1,3-Propanedithiol. Pyridine-Sulfur trioxide complex. 

The same chiral auxiliary has also been used for the stereoselective synthesis of arene-chromium complexes treatment of an aromatic aminal with chromium hexacarbonyl gives the corresponding complex with high diastereomeric excess. This protocol was recently applied in a total synthesis of (—)-lasubine (eq 4). A successful application of 1,2-diaminocyclohexane (as its IR,2R enantiomer) as a chiral auxiliary is illustrated by the di-astereoselective alkylation of the potassium enolate of bis-amide (3) with electrophiles such as benzyl bromide to give bis-alkylated products with excellent diastereoselectivity (eq 5). Lower levels... 

Two other groups investigated P,N ligands for amination chemistry with secondary amines. Uemura and coworkers have prepared ligands similar to those of Kumada, but based on arene chromium complexes rather than ferrocenes64. Catalysts containing ligand... 

A4 -Cholestcne-3-one, 269 As-Cholestene-3-one, 380 A4-Cholestenyl acetate, 265 A9( 1 )-Cholestenylacetate, 265 Cholesteryl acetate, 51 Cholesteryl phosphorodichtoridate, 390 Cholic add, 252,416 Chromic acid, 95-96 Chromic anhydride, 96-97 Chromic anhydride in graphite, 97 Chromic anhydride-Pyridine, 96, 304 Chromium(II)-amine complexes, 97 Chromium(lll) chloride, 162 Chromium hexacarbonyl, 346 Ouomium(II) perchlorate, 97 Chromous acetate, 97-98 Chromous chloride, 506 Chromyl chloride, 98-99 Qnnamaldehyde, 97,269,406 Cinnamic alcohol, 97 Cinnamyl acetate, 322... 

Similarly, the pentacarbonyl[(2-cyclopropyl-2-dimethylaminovinyl)ethoxycarbene]chromium complex 27, prepared from pentacarbonyl[cyclopropylethynyl(ethoxy)carbene]chromium 19 and dimethylamine (or other secondary amines), reacted with pent-l-yne or phenylethyne to give 1-propyl- or 1-phenyl-substituted 5-cyclopropyl-5-dimethylamino-3-ethoxycyclopenta-1,3-diene in 62-77% yield.With substituents other than cyclopropyl yields were drastically lower unless the reaction of the carbene complex was performed in pyridine or acetonitrile. 

---