摘要:

AbstractThe development of new preparative and analytical techniques that allow appropriate handling and characterizations of the capricious halogen oxides have initiated a revival of their chemistry. Due to these recent activities, the amount of well‐confirmed knowledge about such oxides has considerably increased. This is especially valid for the structural chemistry in the solid state, which (among other topics) has greatly benefitted from developments in the techniques of in situ crystal growth of low melting substances on a diffractometer. As a consequence, some general crystal chemical features have become apparent: The coordination polyhedra of the halogen oxides can be readily understood in terms of the qualitative VSEPR concept, and there is a pronounced tendency to form mixed valence compounds where the respective valence states can be easily deduced from the coordination polyhedra. Furthermore, intermolecular or interionic bonds are significant, with increasing importance when moving from chlorine to iodine. Finally, ClO2appears to be the only representative with the halogen in an even oxidation stat

ISSN:0009-2940    

DOI:10.1002/cber.19971300302

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe activation of the three classes of ribonucleotide reductases as free radical enzymes is reviewed. Class I uses O2and a diferric μ‐oxo center to generate a stable tyrosyl protein radical. Class II operates with adensoyl cobalamin as the precursor of a putative transient thiyl protein glycyl radical by the concerted forms an O2‐sensitive protein glycyl radical by the concerted action of an iron–sulfur cluster and (S)‐adensoyl me

ISSN:0009-2940    

DOI:10.1002/cber.19971300303

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

Abstract[Tris(dimethylamino)phosphane]gold(I) chloride, μ‐tris‐{[tris(dimethylamino)phosphane]gold(I)}oxonium tetrafluoroborate, {μ3‐tris(dimethylamino)phosphaneimidotris[tris(dimethylamino)phosphane]gold(I)}(2+) bis(tetrafluoroborate) andN‐trimethylsilyltris(dimethylamino)phosphaneimine were prepared using modifications of established procedures. Their structures were determined in single‐crystal X‐ray diffraction studies. The ligand (Me2N)3P, here introduced into gold(I) chemistry for the first time, lends high stability to these compounds through efficient steric shielding of the reaction sites and through a balanced electronic substituent effect. The structural details of the (Mr2N)3P groups are of current interest because of the unusual nonequivalent configuration of the nitrogen atoms in the dimethylamino groups. This behaviour has been observed for most of the (Me2N)3P units in the compounds studied

ISSN:0009-2940    

DOI:10.1002/cber.19971300304

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe three‐component reaction of [(η5‐C5H5)Co(η5‐(CEt)2(BEt)2CMe)]−, CoCl2and B9H−14(7) yields the triple‐decker complex [(η5‐C5H5)Co{μ,η5‐(CEt)2(BEt)2CMe}‐6‐Co(B9H13)] (8) with a terminal B9H13ligand contaning two cobalt–boron‐bridging hydrogen atoms. Analogously, (6‐H)−, CoCl2, andarachno‐6‐SB9H−12(10) react to give the triple‐decker [(η5‐C5H5)Co{μ,η5‐(CEt)2(BEt)2CMe}‐1‐Co‐2‐(SB9H9)] (11). The analogous reaction with the heteroboranyl anion arachno‐6,8‐S2B7H8−leads to the loss of one boron atom, forming the air‐stable triple‐decker complex [(η5‐ C5H5)Co{μ,η5‐(CEt)2(BEt)2CMe}‐7‐Co‐6,8‐(S2B6H8)] (12). The X‐ray structure determination shows that the dithiacobaltaborane fragment in12has an arachno cluster geometry. The three‐component reaction of (6‐H, CoCl2, and arachno‐2,3‐S2B9H10−yields the expected triple‐decker [(η5‐C5H5)Co{μ,η5‐(CEt)2(BEt)CMe}Co‐6,8‐(S2B9H9)] (15), and surprisingly the sandwich complex (η5‐C5H5)Co‐6,8‐(S2B9H9) (16). The constitutions of the new compounds are based on NMR and

ISSN:0009-2940    

DOI:10.1002/cber.19971300305

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractWhen treated with two equivalents of a butyllithium/potassiumtert‐butoxide mixture, terminal olefins carrying unprotected hydroxy or carboxy groups generate allylmetal intermediates which can be trapped with chlorotrimethylsilane to afford functionalized (Z)‐2‐alkenyltrimethylsilanes. One equivalent of the superbasic reagent suffices if the unsaturated alcohols are first protected as acetals before being subjected to the metalation/silylation/hydrolysis seq

ISSN:0009-2940    

DOI:10.1002/cber.19971300306

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe dichotomy between concerted cyclopropanation and carbolithiation pathways on intramolecular carbenoid cyclopropanation reactions has been studied. These studies have been extended to the intramolecular carbenoid/aldehyde addition reaction.

ISSN:0009-2940    

DOI:10.1002/cber.19971300307

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe reaction of the bis(triflates) [F3CSO3‐(CH)m‐O3SCF3] [m = 5–10, 12, 14, 16 (1a–i) with Na2[Os(CO)4] in dimethyl either affords the osmacycloalkanes2a,2band2f–i(m= 5, 6, 10, 12, 14, 16), diosmacycloalkanes3a–i(m= 5‐10, 12, 14, 16), and triosmacycloalkanes4a–i(m= 5–10, 12, 14, 16). The structure of3fwas investigated by an X‐ray structural analysis. This 22‐membered disomacycle crystallizes in the space groupPā withZ= 1. If the unsaturatedcis‐4‐octen‐1,8‐diyl bis(trifluoromethanesulfonate) (5) is treated with Na2[Os(CO)4] the diosmacyclooctadeca‐5,14‐diene6is obtained. By treating the bis(triflates)1a,bwith Na2[Fe(CO)4] the corresponding ferracycloalkanes are formed only in situ. Insertion of carbon monoxide into the M–C σ bonds leads to the cy

ISSN:0009-2940    

DOI:10.1002/cber.19971300308

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractNeutral oxorhenium(V) complexes of the general formula ReO(L)Cl2are obtained by reaction of [ReO4]−or [ReOCl4]−with functionalized dithiaalcohols (L) containing the donor atom sequences S, S, O−and S, O−, S. Ligand exchange reaction of [ReOCl4]−with HO(CH2)2S(CH2)2S(CH2)2O (R = H, Et ) leads to the formation of ReOCl2[O(CH2)2S(CH2)2‐S(CH2)2OEt] (1b). Reduction of [ReO4]−with a 1:1 mixture of concentrated HCl and glacial acetic acid in the presence ofnBuSCH2‐CH(OH)CH2S‐nBu yield ReOCl2[OCH(CH2S–nBu)2) (4). X‐ray structure analysis of1a,1band4shows distorted octahedral coordination with the chlorine and sulfur atoms in the equatorial plane. The oxygen of the hydroxyl group coordinates in atransposition with respect to the ReO core.1areacts with an excess of acetyl chloride in an unexpected way, resulting in cleavage of thetransRe–O bond and acylation of both of the hydroxyl groups to form the μ‐oxo bridged complex [ReOCl2{CH3COO

ISSN:0009-2940    

DOI:10.1002/cber.19971300309

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractNew and stable bis(organyloxy)boranes, 1,3,2‐dioxaborolanes and 1,3,2‐dixoaborinanes have been prepared (i) from the corresponding diol and BH3·THF and (ii) from 1,2‐diketones and BH3·THF. They were characterized by spectroscopic techniques. The BH stretching frequency seems to be a measure of ring strain and Lewis acidity. The compounds have been qualitatively tested in the transition‐metal‐catalysed hydroboration of cyclopentene, and the dioxaborinane11proved to be superior to the 1,3,2‐dioxabo

ISSN:0009-2940    

DOI:10.1002/cber.19971300310

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractIn complexes of ethylcycloarsoxane (C2H3AsO)n, the oligomer sizenis influenced by the coordinated metal atom. Cyclic tetramers are observed in the porous sheet structures of ∞2[Cu2Br2{cyclo‐(C2H5AsO)4}3] (1) and2∞ [Cu3I3{cyclo‐(C2H5As0)4)2] (2), prepared by the reaction of the appropriate copper(I) halide with (C2H5AsO)nin acetonitrile. Both complexes contain μ1κAs1:2κAs3‐coordinated (C2H5AsO)4ligands as molecular bridging units between individual copper(I) centres leading to large respectively 36‐ and 40‐membered rings. An analogous bridging mode is found in the cyclic oligomers [cyclo‐(ReBr(CO)3{μ‐[cyclo‐(C2H5AsO)}}4](3) formed by reacting {ReBr(CO)5] with (C2H5AsO)nin refluxing toluene. – In contrast both [(NH4){cyclo‐ (C2H5AsO)5}2][Ag(SCN)]2(4) and2∞[(Cs(cyclo‐(C2H5‐AsO)3]2} Cu2(μ‐I)I2] (5) contain pentamers (C2H5AsO)5, which coordinate the NH+4and Cs+cations κ5Oin a pentagonal antiprismatic fashion. In5, prepared by self‐assembly from CsI, CuI, and (C2H5AsO)nin acetonitrile, [Cs[cyclo‐{C2H5AsO}5)2]+sandwich cations are linked thorough μ‐1κAs1:2κAs2‐coordinated [Cu2l3]−units into polymeric chains. This coordination pattern reflects the unique ring siz

ISSN:0009-2940    

DOI:10.1002/cber.19971300311

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY