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Über π-Allyl-Komplexe des Molybdäns II. Die bildung von π-Allyldicarbonylmolybdän-Komplexen aus Molybdän-hexacarbonyl und seinen Derivaten☆

π-Allyldicarbonylmolybdenum compounds are obtained from molybdenum hexacarbonyl and allylic compounds in the presence of n-donors. Preparations and reactions of several new mono- and binuclear π-allylmolybdenum complexes are described. A scheme for the formation and interconversion of the four possible π-allyldicarbonylmolybdenum complex types is presented.

Diazadiene complexes of Group 4 metals. I. Synthesis of mono-, bis- and tris(diazadiene)titanium complexes and the structure of diazadienedichlorotitanium

Abstract Exhaustive reduction of diazadienes (dad=R-N=CH-CH=N-R, R=But, Pri) with lithium and sub- sequent addition of titanium tetrachloride yields the homoleptic diazadiene-titanium complexes [(dad)2Ti] (1, 2) and (dad)3Ti (3) (R=Pri). Complexes (dad)TiCl2(4, 5) are similarly formed from a 1:1 reaction of Li2[dad] with TiCl4. Substitution reaction of 4 (R=But) afford complexes (dad)TiCl(X) (6–8) (X=N(SiMe3)2, C5H5, CH2CMe3). All compounds are volatile, soluble in unpolar solvents, and intensely coloured. A structure investigation by X-ray diffraction was performed for (Butdad)TiCl2 (4): space group P42/n, a=14.774(3), b=14.792(4), c= 13.322(2) A. It shows a five-coordinate chloro-bridged dimer. The Ti2Cl2 ring is folded along a line through the chlorine atoms, the TiNCCN chelate is folded along a line through the nitrogen atoms, which do not deviate strongly from sp2 geometry. The bond lengths within the chelate indicate only a partial reduction of the dad. Symmetry arguments and data from the NMR and electronic spectra give indications as to the oxidation state of the metal and dad in the homoleptic complexes as well.

Diazadien-nickel-alkyle☆

Abstract Low temperature reactions of diazadienes (DAD), R′NC(R)C(R)NR′, and nickel halides or complexes (DAD)NiX 2 with CH 3 MgI yield deep green solutions of (DAD)Ni(CH 3 ) 2 which decompose readily on warming except in cases of 2,6-disubstituted N -aryl groups R′. The thermal stability and spectroscopic properties of these potentially interesting precursors in catalytic reactions are compared with those of (dipy)Ni-alkyls.

Intramolekularer ligandenaustausch in einkernigen heterodien-eisentricarbonylkomplexen

Abstract The intramolecular CO-exchange in several dieneiron tricarbonyls with heteroatoms in 1- and/or 4-position is studied by temperature dependent 13C NMR spectroscopy. π, π-Bonded polar dienes show the highest barriers (10–14 kcal mol−1, while the investigated σ,π- and σ,σ-diazadiene chelates have barriers of activation

Diazadienes as control ligands in homogeneous catalysis XVIII. Palladacyclopentadienes and platinacyclopentadienes and the co-cyclotrimerization of various alkynes☆

Bis(dibenzylidene acetone)palladium reacts readily with N-aryl diazadienes (dad  ArNCRCRNAr) and two moles of dialkyl acetylenedicarboxylates ECCE (E  COOR) to form the palladacyclopentadienes (dad)PdCECECECE (2a–h). With a propiolic ester HCCE the corresponding complex (dad)PdCHCECECH 3 is also formed in small yield. An η2-alkyne complex 4 is obtained from the very bulky dad tBuNCHCHNtBu. The platinacyclopentadiene analogues of 2, (dad)PtCECECECE (5) have been prepared, but unlike the others are inactive in catalysis. The acetylenic diesters readily undergo cyclotrimerization with 2 as catalyst. Depending on the nature of the substituents, numerous alkynes R′CCR″ undergo a catalytic cyclo-cotrimerization with two moles of the diester ECCE to form a number of interestingly substituted benzenes. In the case of propargylic alcohols benzolactones are formed via a transesterification reaction during the catalysis. For phenylacetylene and ECCE not only the corresponding biphenyl derivative 8 but also the linear Z and E 1:2-addition products have been isolated.

Komplexchemie von vierzentren-π-systemen IV. Synthese und eigenschaften hochsubstituierter molybdän-carbonyl-derivate

Abstract Reaction of π-allyldicarbonylmolybdenum complexes with triphenyl- or tributylphosphine gives, along with corresponding phosphonium salts, tetrasubstituted molybdenum carbonyls (PR3)2L2Mo(CO)2 (I), (II); ligand substitution yields the sensitive dicarbonyls (V)-(XXXVI), whose CO stretching frequencies depend on the relative donor and acceptor strength of the ligands characteristically. Disproportionation reactions yield some molybdenum tricarbonyls which are otherwise difficult to prepare. The mechanism of allyl elimination is discussed briefly.

Rhodium(I)-mono- und -diazadienkomplexe, synthese, spektroskopische charakterisierung, oxidative additionsreaktionen und einsatz in der homogenen katalyse zur hydrosilylierung

Abstract The reaction of [Rh(CO) 2 Cl) 2 with di- and monoazadienes gives planar, four-coordinated rhodium(I) complexes Rh(CO)Cl(DAD) (III) and Rh(CO)Cl(MAD) 2 (V), respectively, which catalyse the hydrosilylation of alkenes and alkynes. In a stereoselective cis -addition symmetric internal alkynes give the corresponding silyl alkenes, while the catalytic addition of silane to terminal alkynes leads to the 2-silyl and cis - and trans -1-silyl-alkenes; their ratio depends on the controlling ligand and on the reaction conditions. With a stoichiometric amount of the silane the complexes III react under oxidative addition to give the rhodium(III) complexes Rh(H)(SiR 3 )(DAD)Cl (VI), which also catalyse the hydrosilylation.

Copper(I) complexes with unsaturated nitrogen ligands. Part III. Copper(I) diazadiene complexes with carbon monoxide, olefins and acetylenes

Abstract Diazadienes, RNCR′CR′NR, a versatile chelating ligand system similar to 2,2′-bipyridine or 1,10-phenanthroline, readily form 1:1 complexes with copper(I) trifluorsulfonate. By the addition of small organic ligands like carbon monoxide, ethylene or other olefins, and alkynes twenty-four new compounds of stoichiometry (diazadiene)Cu(L)O3SCF3 are obtained. Even the very electron-poor acetylene dicarboxylic acid esters can be coordinated to copper(I). The crystal and molecular structures of one cyclohexene complex (6) and one carbonyl complex (9) have been determined by X-ray diffraction techniques. (6: monoclinic, space group Cc, a = 17.1181(58), b = 12.8755(54), c = 17.2138(77) A, β = 108.060(33)°, Z = 4; final R = 0.0676, Rw = 0.054. 9: orthorhombic, space group P212121, a = 11.2226(18), b = 12.0142(30), c = 18.4974(34) A, Z = 4; final R = 0.057, Rw = 0.036). Both structures indicate a tendency of copper(I) to adopt trigonal planar coordination geometry, this tendency being more pronounced in the olefin complex. There is still some interaction with one oxygen atom of the triflate anion. Most complexes dissociate in dilute solution, while in concentrated solutions it was possible to obtain 1H NMR spectra and in some cases even 13C NMR spectra, which show an averaged C2υ symmetry. It was not possible by NMR to distinguish between dissociation and non-rigidity processes.

Elektronenreiche übergangsmetallkomplexe : I. Nitril-phosphin-molybdändicarbonyle: Synthese und schwingungsspektren

Abstract Acetonitrile (AN) is substituted under very mild conditions in (AN) 2 - [P(C 6 H 5 ) 3 ] 2 Mo(CO) 2 , (AN) 2 [P(n-C 4 H 9 ) 3 ] 2 Mo(CO) 2 and AN[P(n-C 4 H 9 ) 3 ] 3 - Mo(CO) 2 by aromatic and α,β-unsaturated nitriles. In more than 60 new, highly coloured compounds the nitriles show solvent dependent π-acceptor properties. The nitrile stretching frequencies are substantially lowered and are split in cis -dinitrile complexes by π-coupling. Band position and splitting are opposite to corresponding parameters in the cis -dicarbonyl group. Structural peculiarities are discussed for isonicotinonitrile, acrylonitrile and benzodinitriles.

Regio- und stereoselektive hydrosilylierung von isopren mit rhodium(I)- und rhuthenium(II)-komplexen ungesättigter N-haltiger steuerliganden

Abstract The catalysis of isoprene hydrosilylation with different silanes HSiR 3 ″ (R″ = Et, Ome, OEt), in the presence of rhodium(I) or ruthenium(II) complexes with unsaturated N -containing controlling ligands as co-catalysts, occurs under mild conditions and gives with high selectivity ( Z )-2-methyl-1-silyl-2-butenes (VI), 2-methyl-4-silyl-2-butenes (VIII), 2-methyl-4-silyl-1-butenes (IX) or the 3-methyl-4-silyl-1-butenes (X). Thus four out of five possible isomers of the Si addition to a terminal sp 2 -C atom can be obtained as the main products of catalysis (51–87%) by changing the metal and the controlling ligand. Chiral X is obtained for the first time via catalysis. Full 1 H NMR assignment is given for compounds VIII–X.