Wolfgang Imhof

Stabile bis(alkinyl)-titanocen-komplexverbindungen von FeCl2 und CuCl

The application of (η5-C5H4SiMe3)2Ti(CC-SiMe3)2 as an organometallic bidentate chelate ligand for MCl2 building blocks (M = Fe, Co, Ni) is discussed. Reaction of the organometallic substituted alkyne Me3Si-CC-(η5-C5H4SiMe3)2Ti-CC-SiMe3, I, with FeCl2 affords in high yields the dinuclear complex {(η5-C5H4SiMe3)2Ti(CC-SiMe3)2}FeCl2, II. The identy of compound II is confirmed by analytical and spectroscopic data as well as by an X-ray diffraction study. Structural data for L2Ti(CC-SiMe3)2, I, {L2Ti(CC-SiMe3)2}FeCl2, II, and {L2Ti(CC-SiMe3)2}CuCl, III, (L = η5-C5H4SiMe3) are discussed.

Zur reaktivität von komplexen [LnMXMLn] (X = Ge, Sn, Pb; Ln M = Cp′(CO)2Mn) mit chelatliganden: synthese und charakterisierung der derivate [{LnM}2XDipy]

Abstract The compounds [Cp′(CO) 2 MnXMn(CO) 2 Cp′] (X = Ge, Sn, Pb), obtained from Na[{Cp′(CO) 2 Mn} 2 H}] ( 1 ) and GeCl 4 , SnCl 2 or PbCl 2 , respectively, react with dipyridine to yield the chelate derivatives [{Cp′(CO) 2 Mn} 2 Xdipy] (X = Ge: 3 ; Sn: 5 ; Pb: 7 ). The structures of the compounds 3 and 5 are similar to the one reported for 7 [1]. The species 3, 5 , and 7 , which contain the main-group elements in a formal oxidation state of zero have an idealized tetrahedral ( C 2ν ) coordination around the maingroup bridging atom X, which tends to deviate towards a pseudo trigonal-bi-pyramidal coordination for 7 (X = Pb). This observation together with other relevant structural (bondlengths XMn/XN: X = Ge: 234/213pm; X = Sn: 247/233pm; X = Pb: 253/256pm) and spectroscopical data indicates a rather weak interaction between the parent cumulene and the chelate ligand.

Neue methoden zur einführung von μ3-chalkogenbausteinen in carbonylmetallcluster; XCN− (X = S, Se, Te) und R′XXR′ (X = Se, Te) als selektive reagenzien

Abstract The RP-bridged clusters Fe3(CO)10(μ3-RP) (1) (A) when treated with XCN− (X = S, Se, Te) yield the anionic addition products (D). Reaction of these adducts with Et3OBF4 leads to the high yield formation (90%) of Fe3(CO)9(μ3-RP)(μ3-X) (2). The compounds 2 are also obtained from 1 and R′XXR′ (X = Se, Te), albeit less selectively (≈ 60%). In addition the binuclear species Fe2(CO)6(μ2-R′X)(μ2-RPXR′) (3) are obtained (≈ 30%). In the case of R′TeTeR′ Fe3(CO)8(μ3-RP)(μ2-R′Te)2 (4) is formed as an additional product. The structures of the compounds 2, 3 and 4 are documented by X-ray analysis. The geometry of 2 is analysed in terms of a metallaheterocyclobutadiene model, η4-[F R]Fe(CO)3, in comparison with known structural analogues. NMR data (1H, 13C, 31P, 77Se, 125Te) are reported for all new compounds.

Mechanistical studies on C–H activation reactions of benzaldimines using selectively deuterated ligands: synthesis and crystal structures of [μ2-η3-(R)N–CH2–(H)]Fe2(CO)6

Abstract The reaction of Fe2(CO)9 with imine ligands derived from benzaldehyde leads to the formation of dinuclear iron cluster compounds of the general formula [μ2-η3-N–CH2– CC–C(H)C(H)–C(H)C (H)]Fe2(CO)6 by a C–H activation/1,3-hydrogen shift reaction sequence. Six cluster compounds with alkyl and aryl substituents bound to nitrogen have been synthesised and characterised, five of them also by means of X-ray crystallography. The mechanism of the reaction has been investigated by the use of ligands being selectively deuterated in the 2-position. By several NMR experiments including deuterium spectra it can be demonstrated that the hydrogen/deuterium atom of the activated aromatic C–H bond is transferred to the former imine carbon atom producing a methylene group instead and that this reaction strictly follows an intramolecular pathway.

Controlled synthesis of (1,3-tBu2-C5H3)2TiCl2 and (1,3-tBu2-C5H 3)TiCl3. Crystal structure and reactions of (1,3-tBu2-C5H3)TiCl3

The compounds (1,3-tBu2C5H3)2TiCl2 (I) and (1,3-tBu2C5H3)TiCl3 (II) were prepared in good yields from TiCl4 and (1,3-tBu2-C5H3)Li. Reactions of II with methanol, ethane-1,2-diol, sodium oxalate, and 2-pyrazine carboxylic acid afforded various organotitanium complexes. The crystal structure of II was determined.

Monomere alkin-stabilisierte kupfer(I)-halogenid-und kupfer(I)-pseudohalogenid-verbindungen; kristallstruktur von [(η5-C5H4SiMe3)2Ti(CCPh)2]CuCl

The reaction of Me3SiCCSiMe3 (bd1}), LnMCSiMe3 (4a, LnMCp(CO)2Fe; 4b, LnMCp(CO)3Mo] and E(CCR)2 (6, EMe2Si; 8, E(η5-C5H4SiMe3)2Ti; R is a singly bonded organic ligand) with CuX (2) (X is a halide or pseudohalide) is described. 1 and 4 react CuX (2a, XCl; 2b, XBr; 2c, XI; 2d, XOSO2CF3) to yield the dimeric compounds [(η2-Me3SiCCSiMe3)CuX]2 (3a, XCl 3b, XBr; 3c, XI; 3d, XOSO2CF3) or [(η2-LnMCCSiMe3)CuX]2 (5a, LnMCp(CO)2Fe, XCl; 5b, LnMCp(CO)3Mo, XCl) respectively. In these compounds the C2 building block is η2-coordinated to a CuX moiety and by the formation of copper-X-bridges (Cu2X2) a dimer is formed. However, the reaction of Me2Si(CCSiMe3) (CCR) (6a, RSiMe3; 6b, RH) with CuX (2) (XCl, Br, OSO2CF3, O2CMe) affords polymeric Me2Si[η2-CCSiMe3})(η2-CCRCu2X2]n (7a RSiMe3, XCl; 7b, RSiMe3, XBr; 7c, RH, XCl; 7d, RH, XBr; 7e, RSiMe3, XOSO2CF3; 7f, RSiMe3, XO2CMe) in high yields. In 7a–7f each alkynyl fragment is η2-coordinated to a CuX unit. While the reaction of 6a or 6b with CuX yields polymeric 7a–7f, the organometallic 1,4-diyne RCC-[Ti]-CCR ([Ti](η5-C5H4SiMe3)2Ti; 8a, RPh; 8b, RSiMe3) affords with CuX (2a, XCl; 2b, XBr; 2c, XI; 2e, XCN; 2f, XSCN) the dinuclear compounds [(η5-C5H4SiMe3)2Ti(CCR)2]CuX (9a, RPh, XCl; 9b RSiMe3, XCl; 9c, RSiMe3, XBr; 9d, RSiMe3, XI; 9e, RSiMe3, XCN; 9f, RSiMe3, XSCN). Compounds 9a–9f feature a monomeric copper(I) halide or copper(I) pseudohalide moiety, which is stabilized by the chelating effect of the alkynyl ligands in [Ti](CCR)2. [(η5-C5H4SiMe3)2Ti(CCSiMe3)2]CuCl (9b) reacts with AgX (XCN, SCN, O2CMe, O2CPh) to yield [(η5-C5H4SiMe3)2Ti(CCSiMe3)2CuX (9e, XCN; 9f, XSCN; 9g, XOC(O)Me; 9h, XOC(O)Ph) by precipitation of AgCl. In addition, the bis(alkynyl)-ansa-titanocene [(η5-C5H4)Me2Si(η5-C5H3SiMe3)]Ti(CCSiMe3)2 (10) yields with CuCl (2a) the dinuclear species {[η5-C5H4)Me2Si(η5-C5H3SiMe3})]Ti(CCSiMe3)2CuCl (11). The identity of compounds 3, 5, 7, 9 and 11 is confirmed by analytical and spectroscopic (IR, MS, 1H, 13C NMR) data, and that of [(η5-C5H4SiMe3)2Ti(CCPh)2]CuCl (9a) is confirmed by X-ray analysis. Crystals of 9a are monoclinic, space group Pc with cell constant a = 992.6(7), b = 1210(1), c = 1335.5(7) pm, β = 105.75(5)°, V = 1543(2) × 106 pm3 and Z = 2.

The mutual influence of the imine substituents of terephthal-bis-imines concerning their reactivity towards Fe2(CO)9

Abstract The reaction of terephthal-bis-imines with Fe2(CO)9 proceeds via a CH activation reaction in the ortho position with respect to one of the imine functions. The corresponding hydrogen atom is shifted towards the former imine carbon atom producing a methylene group instead. The dinuclear iron complexes formed by this reaction sequence and showing no coordination of the second imine group were isolated from reactions of bis-imines with both phenyl and cyclohexyl substituents at the imine nitrogen atoms. In addition, we observed three different reaction pathways of the second imine substituent of the starting material which is obviously thus influenced by the fact that the first one is coordinating an Fe2(CO)6 moiety. If the organic substituent at the imine nitrogen atoms is a phenyl group the formation of a trinuclear complex is achieved in which an additional Fe(CO)3 group is coordinating the CN double bond and one of the carboncarbon bonds of the central phenyl ring in an η4-fashion. The same reaction leads to the isolation of a tetranuclear ironcarbonyl compound in which both imine substituents were transformed via the pathway described above, each building up dinuclear subunits. In contrast to this the reaction of a bis-imine with cyclohexyl groups at the imine nitrogen and thus an enhanced nucleophilicity leads to the formation of a tetranuclear complex in which only one imine group reacts under CH activation with subsequent hydrogen migration towards the former imine carbon atom. The second imine substituent also shows a CH activation reaction in the ortho position with respect to the imine group but the corresponding hydrogen atom is transferred to one of the aromatic carbon atom of the central phenyl ring of the ligand. The CN double bond remains unreacted and only coordinates the second Fe2(CO)6 moiety via the nitrogen lone pair.

nido- und closo-Cluster als Halbsandwich- und Tripeldeckerkomplexe: ein einfaches MO-Modell zur Deutung des Redoxverhaltens von Clustern

Abstract The halfsandwich-type compounds η4-[R (CO)3]Fe(CO)3, (X = Se, Te) 1a, 1b (type A), may be stacked to the tripeldecker-type compounds μ2-η4-[R (CO)3]Fe2(CO)5, 2a (X = Se), 2b (X = Te) (X-ray analysis) (type B). The relation between the compounds 1 and 2 is the same as the one between the nido pentagonal pyramidal clusters η5-[R (CO)3]Fe(CO)3, 3 (type C) and their closo derivatives μ2-η5-[R , 4 (type D). The analysis of a specific dynamic behaviour of compounds 3 is reported. In addition a model is proposed, which explains the observed pairwise relation in the redox potentials of structurally related nido and closo compounds in a simple manner.

Triphenylphosphanchalkogenide als selektive Reagentien zum Aufbau von μ3-Chalkogenverbrückten Eisencarbonylclustern

Abstract Irradiation of the tetrahedral clusters Fe 3 (CO) 10 (μ 3 -P t Bu), 1 , in the presence of Ph 3 PX (X  S, Se) leads to the formation of the square-pyramidal clusters Fe 3 (CO) 9 (μ 3 -P t Bu)(μ 3 -X) ( 2a : X  S; 2b : X  Se) and Fe 3 (CO) 8 (PPh 3 )(μ 3 -P t Bu)(μ 3 -X) ( 3a : X  S; 3b : X  Se). In this reaction the Ph 3 PX-ligands are split into a μ 3 -X-fragment as well as a PPh 3 -ligand, which are both integrated into the product clusters. In addition Fe 3 (CO) 9 (PPh 3 )(μ 3 -P t Bu), 5 , a substitution product of the starting cluster 1 , is isolated. During the reaction of 1 with Ph 3 PSe the cluster Fe 3 (CO) 7 (PPh 3 ) 2 (μ 3 -P t Bu)(μ 3 -Se), 4 , is formed as a further product.

Übergangsmetall-Carbin-Komplexe: XCIX. Synthese und röntgenstruktur von (η5-C5Me5)(CO)2MOCNEt2, dem ersten niedervalenten Diethylaminocarbin-Komplex von Molybdän mit einem Pentamethylcyclopentadienyl-Liganden

Abstract Activation of the ethylisocyanide ligand for an electrophilic attack at nitrogen is induced in Na[(η5-C5Me5)(CO)2Mo(EtNC)] (2) by the electron rich Mo0 center. Thus complex 2, which is quantitatively obtained by reduction of cis, trans-(η5-C5Me5)Mo(CO)2(EtNC)I (1a, 1b) with two equivalents of Na, reacts with Et3OBF4 in THF to give as the major product (η5-C5Me5(CO)2MoCNEt2 (3. A minor product, the iminoacyl complex (η5-C5Me5)(CO)2Mo[η2-C(NEt)Et] (4) is also obtained in this reaction. Formation of 4 is explained by a concomitant attack of the electrophile Et3OBF4 on the metal center of 2 followed by a migratory insertion of the metal bonded ethyl group to the ethylisocyanide ligand. 3 represents the only hitherto known low valent molybdenum diethylaminocarbyne complex with a pentamethylcyclopentadienyl ligand and the first example in the class of the compounds (π-arene)(CO)2MCNR2 to be structurally characterized by a single X-ray crystallographic study. 3 crystallizes in the monoclinic space group P21/c. The unit cell with a = 966.1(3), b = 1240.1(4), c = 1550.2(6) pm and β = 102.34(3)° contains four molecules. Striking features of the structure are the short CcarbyneN bond distance (129.9(6) pm) and the planarity of the three bonds around the nitrogen atom indicating a strong π interaction of the diethylaminogroup with the carbyne carbon. Moreover the amino plane of the carbyne ligand and the mirror plane of the (η5-C5Me5)(CO)2Mo fragment are almost perpendicular to each other.