摘要:

(Butadiene)(cyclopentadienyl)niobium ComplexesThe known bis(butadiene)(cyclopentadienyl)niobium complex (C5H4R)Nb(C4H6)2(1, RH) exists in solution as a 1 : 1 mixture of a bis(cis‐butadiene) isomer1aand a (cis‐butadiene)(trans‐butadiene) isomer1b. In solution the barrier to isomerisation is 80 ± 2 kJ/mol. New derivatives2(RMe) and3(RSiMe3) of1are described. One of the butadiene ligands in1–3is readily substituted with CO, CNtBu, P(OMe)3, and PMe3. CpNb(PMe3)2(C4H6) (7) reacts with disubstituted acetylenes to form acetylene complexes CpNb(PMe3)(C4H6)(RCCR') (8: R, R'=Ph,9: RMe, R'=Ph, and10: RPh, R'=SiMe3), The structure of9resembles that of bent metallocene derivatives with the acetylene ac

ISSN:0009-2940    

DOI:10.1002/cber.19911240502

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Vinylcyclopropane Complexes and Vinylcyclopropanes from Benzylidene Complexes and 1,3‐DienesBenzylidenepentacarbonyl complexes (CO)5M[C(C6H4R‐p)H] (1) [M – W:RH (a), OMe (b); MCr: R – H (c), OMe (d)], react with cyclopentadiene by stereospecific transfer of the benzylidene ligand to one CC bond of the diene and coordination of the resultingendo;‐6‐arylbicyclo[3.1.0]hex‐2‐ene (4) to the metal. The [CO]5M fragment occupies theexo‐position. Addition of bromide liberates4from the metal. The reaction of1awith 1,3‐cyclohexadiene gives the corresponding (endo;‐7‐phenylbicyclo[4.1.0]hept‐2‐ene)tungsten complex (6) and, after addition of Br−, the free bicyclic compound. The sequential reaction of1awith 1,2,3,4,5‐pentamethylcyclopentadiene and Br−affords theendo;‐6‐phenyl‐exo;‐4‐methyl isomer of pentamethylphenylbicyclo[3.1.0]hex‐2‐ene9with more than 85% stereoselectivity. The benzylidene transfer from1atocis‐andtrans‐pentadiene, isoprene, and 2‐chloro‐1,3‐butadiene proceeds regiospecifically to the more electron‐rich CC bond to give (E)‐ and (Z)‐phenylvinylcyclopropanes. TheE/Zratio ranges from 0.52 to 2.2.

ISSN:0009-2940    

DOI:10.1002/cber.19911240503

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Transition‐Metal‐Substituted Acylphosphanes and Phosphaalkenes, XV. – Reaction of the Phosphaallyl Complex (η5‐C5Me5)(CO)Fe{η3‐P[CH(SiMe33)2](CHCO}} with Chalcogenes as well as with Fe2(CO)9The (η3‐phoshaalyl)iron complex (η5‐C5Me5)(CO)Fe{η3‐P(CH(SiMe3)2](CHCO)} (1) is oxidized by sulfur and selenium to afford the methylenethioxo‐ and methyleneselenoxophosphorane complexes4and5with ananti‐configuration of the CH(SiMe3)2substituent relative to iron. The chalcogene atoms are attached to the phosphorus atom of the ligand and do not participate in the bonding to the metal Equivalent amounts of1and Fe2(CO)9lead to the phosphaalkenyl complex6with an Fe – C σ bond. On the other hand, a large excess of Fe2(CO)9converts1as well as6into the cluster compound7featuring the bridging 1‐oxa‐4‐phosphabutadiene ligand (η5‐C2Me5)(CO)2Fe—C(O)—CHP—CH(SiMe3)2. Constitution and configuration of all compounds have been elucidated by spectroscopic methods (IR,1H,13C,31P NMR, and MS). In addition complexes5and7have been characteri

ISSN:0009-2940    

DOI:10.1002/cber.19911240504

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Heterocycles as Ligands, XI. – Octamethyl‐1,1′‐diazaferrocene as a Bifunctional Nitrogen Base(C4Me4N)2Fe·2 HNC4Me4(3) reacts with Brønstedt and Lewis acids to give the adducts [(C4Me4N·E)2Fe]n+[4–6,11–13;n=2, EH, CH3, CH3C(O);n=O, EBH3, BF3, Fe(CO)4]. The stepwise substitution of the tetramethylpyrrole molecules in3leads to the complexes [(C4Me4N·E)(C4Me4N·E')Fe]n+[16, 17, 19;n– O, EC4Me4NH, E'=Fe(CO)4;n=1, EBH3, E'=H;n=2, EH, E'=CH3]. Similarly, the complexes [{(C4Me4N)C(O)CH2CH2C(O)(NC4me4}Fe]Cl2(9) and [Ag2{μMe4N)2Fe}2Fe}2](BF4)2·2 MeOH (15) are obtained. Reaction of [(C4Me4NH)2Fe](BF4)2(4) withnBuLi gives the protonated diazaferrocene [(C4Me4NH)(C4Me4N)Fe]BF4(18) from which the dimeric iron diamide {(C4Me4N)2Fe}2(20) is obt

ISSN:0009-2940    

DOI:10.1002/cber.19911240505

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Organosubstituted 2,5‐Dihydro‐1,2,5‐oxoniasilaboratoles – Characterization and Reactivity.The potassium salts of the anions (2a−d,a: R2,3= CH3;b: R2= C2H5, R3= CH3;c: R2= C6H5, R3= CH3;d: R3= C6H5), prepared from the organosubstitutedcis;‐2‐boryl‐1‐silylalkenes1a–dand KOH, react with the electrophiles R1Hal [R1= H: HCl, (CH3)3NHCl; R1= CH3: (CH3)I, (CH3)4NCl; or (CH3)3ElIV(CH3)3, ElIV=Si, Ge, Sn, Pb] to give the neutral five‐membered ring compounds [R1= H:3H; CH3;3Me; ElIV(CH3)3:3ElIV]. On heating of 3H or 3Sn either ethyl migration occurs to yield the saturated diastereomers (4) [4/4′: R3′= H;4Sn/4′Sn: R3′= Sn(CH3)3], or elimination of ethane takes place to give the unsaturated compounds (5). The reaction of2with ClPb(CH3)3leads to 3Pb [R1=Pb(CH3)3] (11B‐NMR), which exclusively form5w

ISSN:0009-2940    

DOI:10.1002/cber.19911240506

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

OrganosubstitutedBicyclic andMonocyclic Compounds from 2,5‐Dihydro‐1,2,5‐oxasilaboratolates1a)The potassium salts of the cyclic anions of (A: R, R′ = CH3;B: R = C2H5, R′ = CH3;C: R = C6H5, R′ = CH3react with [(CH3)2NCH2]Br in THF to yield the bicyclic compounds1a(X‐ray crystal structure analysis),1b/1b' (endo/exo‐C2H5), and1c/1c' (endo/exo‐C6H5).D(RCH3, R'=C6H5) reacts with [(CH)32NCH2]Br to form a 1:4 mixture of1dtogether with the heterocycle (3d) with elimination of (CH3)2N‐C3H7. – FromA–Dand CIP(C6H5)2the six‐membered heterocycles (2a−d) are

ISSN:0009-2940    

DOI:10.1002/cber.19911240507

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Addition of Inorganic and Organic Nucleophiles to the Vinylidene Ligand of the Cluster FeCo2(CO)9(μ3‐CCH2)The CCH2ligand of the cluster FeCo2(CO)9(μ3‐CCH2) (1) is electrophilic at the terminal C atom. Soft inorganic nucleophiles [Nu – PR3, (CH3)2SO, CN−, SCN−] are added to form the zwitterionic complexes FeCo2(CO)9(μ3‐C–CH2–Nu) (4, 7, 8), as proved by the structure determination of FeCo2(CO)9(μ3‐CCH2– PMe3) (4a). The products are of low thermal stability. Upon heating, the PR3derivatives rearrange to the CO substitution products FeCo2(CO)8(PR3)(μ3‐CCH2) (5, 6). C–C coupling is achieved by addition of malonic ester anion derivatives [X – CH – CO2Me] (XMeO2C, CN, Br). The anionic addition product for XMeO2C (10a) can be protonated to form HFeCo2(CO)9[μ3CCH2– CH(COOMe)2] (11) which liberates H2upon warming resulting in FeCo2(CO)9[μ3‐CCH – CH(COOMe)2] (12). Thus, a substitution of a vinylidene H atom has been performed by an HX addition/H2elimination sequence. Phosphorus ylides R3PCHX [XH, SiMe3, Cl, CHO, C(O)Ph, COOR] are also added with CC coupling to yield the complexes FeCo2(CO)9(μ3‐CCH2– CHX – PR3) (15, 16). The structure determination of the compound with XEtO2C and RPh (16c) proves that thes

ISSN:0009-2940    

DOI:10.1002/cber.19911240508

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Diazadiene Complexes of Electron‐Deficient Transition Metals: Synthesis, Properties, and Structure of CpTi(diazadiene)ClThe electron‐deficient 1,4‐diazadiene (DAD) complex CpTi‐(DAD)Cl (3), [DAD=1],4‐bis(4‐methoxyphenyl)‐2,3‐dimethyl‐1,4‐diazabutadiene]is prepared either by reduction of CpTiCl3(1) with magnesium in the presence of free DAD (2) or by the reaction of1with Na2DAD. NMR spectroscopic and X‐ray diffraction analysis of3indicate that the bonding of the DAD ligand has σ2,π‐metallacyclopentene rather than η4;‐π character. As a result of steric repulsion between the Cp ring and methyl groups of the DAD ligand3exhibits a supine (exo) geometry for DAD coordination is solid state. Substitution reaction of3affords the novel

ISSN:0009-2940    

DOI:10.1002/cber.19911240509

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

Upon hydrogenation of magnesium in THF using homogeneous magnesium‐anthracene transition‐metal halide catalysts in the presence of small amounts of MgCl2and solubilizing agents L, a dissolved form of magnesium hydride (MgH'2) is produced. The preferred L's are quinuclidine (QC) or organomagnesium compounds; however, organoaluminium and ‐boron compounds can also be used. The fractionnof magnesium hydride produced in the dissolved form and the stability of the MgH'2solutions are investigated as a function of the kind and the amount of solubilizing agents and catalysts. The optimized method for the preparation of MgH'2is described. The magnesium hydride dissolved in THF is characterized by IR spectroscopy. In order to elucidate the role of the solubilizing agents, THF‐soluble MgCl2‐containing stoichiometric MgH2· QC model complexes are also prepared and characterized by IR spectra. Advantages and disadvantages of using MgH'2for synthetic purposes instead of catalytically prepared suspensions of magnesium hydride (MgH2) are

ISSN:0009-2940    

DOI:10.1002/cber.19911240510

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

The synthesis of new zirconium and hafnium bisporphyrinate double deckers M(P)2(MZr, Hf; POEP, TPP)2,3)is described. The complexes are characterized by UV/Vis/NIR and1H‐NMR spectroscopy and cyclic voltammetry. As compared with MCe, the redox potentials or the energies of the nearinfrared absorption bands of the corresponding radical cations [M(P)2]+are lower by ≈︁ 0.2 V or higher by ≈︁ 2000 cm−1, respectively, Hence, there is a stronger π‐π interaction between the porphyrin ligands as compared with the cerium analogues due to the smaller ionic radii of Zr(IV) and Hf(IV). X‐ray crystallography of Zr(TPP)2confirms the sandwich‐like structure of the compound and the close proximity

ISSN:0009-2940    

DOI:10.1002/cber.19911240511

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY