Heike Pfisterer

Übergangsmetall—methylen-komplexe : XXXI. Primärkomplexierung von diazoalkanen an metall—metall-mehrfachbindungen; ein weiterer koordinationstyp

Abstract An unexpected novel coordination mode of diazoalkanes has been verified via addition of 2-diazopropane to the metal—metal triple bond of bis[dicarbonyl(η5-pentamethylcyclopentadienyl)molybdenum] (MoMo). The dinuclear 1:1 addition product isolated in nearly quantitative yield is structurally characterized by a bent, 4-electron type η1:η2-diazoalkane ligand, with the terminal nitrogen atom symmetrically bridging the metal-metal “single bond” (d(MoMo) 305.0(2) pm; d(MoN(1)) 212.0(12) and 212.6(10) pm, respectively) and the second nitrogen atom being bonded to one molybdenum atom only (d(MoN(2)) 213.4(13) pm).

Übergangsmetall-methylen-komplexe: IXL. Über metallzentrierte umlagerungsreaktionen von diazoalkanen und die einfache synthese von alkylidenamido- sowie isocyanato-komplexen

Abstract The dinuclear 2-diazopropane complex 1 undergoes a novel type of fragmentation upon heating in boiling toluene: irreversible nitrogennitrogen bond cleavage of the metal-coordinated heterocumulene with subsequent rearrangement of the intermediate nitrido(carbonyl)metal species yields a terminal isocyanato ligand while the remaining 2-propylidene amido fragment symmetrically bridges the metalmetal double bond ( d (MoMo) 274.5(2) pm) of the reaction product 2 . This unexpected rearrangement reaction is to be considered as a further variant of the “Hieber base reaction”. A chemical test of the multiple bond character of the molybdenummolybdenum bond present in compound 2 was provided by the reversible addition of carbon monoxide which reaction yields compound 3 . Insertion of a nitrido metal moiety into a methylene bridge was observed, for the first time, in the case of the methodologically related rearrangement process of the diazomethane derivative 4 ; the resulting dinuclear bis(methylene amido) derivative 5 was again characterized by means of X-ray diffraction techniques.

Übergangsmetall—methylen-komplexe IL. Alkyliden-cobalt-komplexe:synthese, konstitution, struktur und folgereaktionen☆

Abstract The dinuclear cobalt complex [(η 5 -C 5 Me 5 )Co(η-(CO)] 2 (Me  CH 3 ; 1 ) adds, when treated with the diazoalkanes 2a – 2n , under mild reaction conditions (−80… + 25°C), (CRR′) of different structures to the metal-metal double bond. The novel η-alkylidene complexes 3c – 3l , 4a , b , e , n and 5m are formed in mostly quantitative yields following elimination of nitrogen. The triply bridged derivatives 3 are generally more stable than in the series of the analogous rhodium compounds described earlier; usually they form at room temperature the isolated final products. Consecutive structural isomerization and/or decarbonylation yield the secondary products of type 4 and 5 . The η-alkylidene complexes 5 open the hitherto best and most straightforward method for the stepwise construction of multiply alkylidene-bridged organometallics: for example, this bis(μ-alkylidene) derivatives 6 and 7 are quantitatively formed when the precursors 5a and 5c , respectively, are treated with diazomethane or diazoethane. The first phosphorylmethylene complex 4n has been obtained by reaction of the cobalt complex 1 with the argentio diazohydrocarbon 2n via elimination of dinitrogen and hydrolysis. The μ-methylene complex (μ-CH 2 )[(η 5 -C 5 Me 5 )Co(CO)] 2 occurs as a mixture of the singly- and the triply-bridged isomers 4a and 3a , both in the solid state and in solution (IR evidence). According to a single-crystal X-ray analysis, trans -oriented sets of equivalent ligands (CO/CO) and C 5 Me 5 /C 5 Me 5 ) are present in the molecule. The dicobaltacyclopropane geometry is characterized by a nearly equilateral Co(1),C,Co(2) triangle having the following bond parameters: d (COC) 190.7(10) and 194.3(8) pm, d (CoCo) 250.2(2) pm (crystal data for 4a : monoclinic, C 5 2h - P 2 1 / c ; a 966.9(4), b 1688.2(7), c 1419.9(6) pm, β 109.86(3)°; Z  4).

Komplexchemie reaktiver organischer verbindungen: XLVII. Synthese, strukturchemie und druckcarbonylierung von metallcarben-komplexen

Abstract The diazoalkane route has been used for the clean incorporation of diarylcarbene ligands into the organomanganese complexes of composition (η 5 -C 5 H 4 R)Mn(CO) 2− thf ( 1 , R = H; 2 , R = CH 3 ; thf = tetrahydrofuran), whose precursors are labile to substitution. The structure of the complex 4b derived from diazosuberon ( 3b ) and exhibiting a seven-membered carbocyclic carbene ligand has been established by virtue of a single-crystal X-ray diffraction study (monoclinic, space group C 2h 5 - P 2/n; a 1045.6(4), b 789.9(4), c 2153.6(4) pm; β 101.56(3)°; Z = 4; R = 0.075, R w = 0.059). Using the same synthetic approach, the dinuclear compound 4d containing an ω,ω′-biscarbene bridge is accessible in 52% yield starting from 1,4-bis(diazobenzyl)benzene ( 3d ). A methodologically simple procedure for the synthesis of η 2 -ketene complexes emerges from high-pressure carbonylation of the metal carbenes 4b and 5b . The geometry of the benzannelated cycloheptanylidenketene derivative 7b has also been elucidated by X-ray diffraction techniques (monoclinic, space group P 2 1 /n; a 998.9(3), b 1302.3(4), c 1466.6(4) pm; β 91.33(4)°; Z = 4; R = 0.057; R w = 0.062).

Übergangsmetall—methylen-komplexe

Abstract A simple, high-yield synthetic route to otherwise inaccessible multiply bridged organometallic compounds having carbonyl, alkylidene and sulfur dioxide bridges is exemplified by the reactivity of bis[μ-carbonyl(η 5 -pentamethylcyclopentadienyl)cobalt] ( Co-Co ) towards diazoalkanes and sulfur-dioxide

Cyclisierung und fragmentierung aliphatischer azide an metall-metall-dreifachbindungen: Neuartige reaktionswege gegenüber ihrer thermischen zersetzung ln der gasphase [1,2]

Abstract The organoazides 4a–4c react with the dinuclear molybdenum and tungsten compounds of composition [(η 5 -C 5 R 5 )M(CO) 2 ] 2 (R = H, M = Mo: 1 ; CH 3 , Mo: 2 ; CH 3 , W: 3 ) at temperatures between 200 and 300 K to yield the novel organoimido derivatives 5–7 in quantitative yields. The dominating structural characteristics of the products are fused 3 5 -membered metallacycles that originate from addition of the aliphatic azides to the metal-metal multiple bonds of the precursor organometallics 1-3 with consecutive ring closure via nucleophilic attack of the coordinated azide upon one of the metalcarbonyl ligands. Another azide molecule undergoes metal-induced nitrogen elimination, with the remaining organoimido fragment being coordinated as a linear terminal ligand through a molybdenum-nitrogen triple bond (172.6(9) pm). The thermal decomposition of allyl azides monitored in the gas phase by the changes in photo-electron spectroscopic ionization patterns, underlines the dominating effect of the multiply bonded metalmetal coordination sphere: N 2 is eliminated only at temperatures above 650 K. As exemplified for allyl azide, the red-hot tube pyrolysis is dominated by a 1,2-hydrogen shift accompanying the N 2 elimination and yields the corresponding imine, H 2 CCHC(H)NH.

Übergangsmetall—methylen-komplexe: LIII. Synthese und struktur eines dreifach verbrückten cobalt-komplexes der μ-alkyliden-reihe

Abstract The μ-ethylidene complex (μ-CHCH3)[(η5-C5Me5)Co(μ-CO)]2 (Me  CH3) accessible along the diazoalkane route from [(η5-C5Me5)Co(μ-CO)]2 and diazoethane exhibits both in solution (IR spectroscopy) and in the crystalline state (X-Ray diffraction) a nearly Cs-symmetrical structure with a triply bridged metal—metal bond. This compound thus differs from the parent μ-methylene complex of analogous composition, which latter compound exists as a mixture of the isomers A and B with terminal and edge-bridging carbonyl ligands, respectively (IR spectra, X-Ray diffraction). A structural comparison with closely related alkylidene- and carbonyl-bridged derivatives reveals a striking lack of correlation between metal—metal bond lengths and formal bond orders as they result from the EAN rule.

Übergangsmetallmethylen-komplexe. ☆: XL. Ketocarben-addition an eine metallcarbonyl-brücke; eine neue CC-verknüpfung

Abstract The cyclic diazoketone diazodimedon ( 2 ) reacts with the dinuclear rhodium complex [(η 5 -C 5 Me 5 )Rh(μ-CO)] 2 ( 1 ) in boiling tetrahydrofuran with elimination of dinitrogen to yield the unusual cycloadduct 3 which arises from addition of the ketocarbene moiety derived from the diazo precursor 2 to the bridging metal carbonyl frame of the metalmetal doubly bonded organometallic metallic species 1 (X-ray diffraction). One interesting structural aspect is the formation of a ketene unit resulting from carboncarbon coupling.

Darstellung und Charakterisierung von Eisenkomplexen, entstanden aus der Reaktion von [(C5R5)Fe(CO)2]2 (R = H, Me) mit Phosphoryliden

Abstract Reaction of [Cp′Fe(CO) 2 ] 2 ( 1b (Cp′ = MeC 5 H 4 ) with the phosphorus ylide Ph 3 PCH 2 yields two products. {μ-CH 2 )(μ-CO)[Cp′Fe(CO)] 2 } ( 2b ) and Cp′(CO)(PPh 3 )Fe(COCH 3 ) ( 4 ). The crystal structure analysis of 2b is reported. It is shown, that with different phosphorus ylides the reaction of [CpFe(CO) 2 ] 2 ( 1a ) (CP = C 5 H 5 ) proceeds differently depending also on the amount of n-butyllithium present. So a threefold excess of the LiX adducts (X = Cl, Br) of the ylides Ph 3 PCHR in the presence of a large excess of n-butyllithium gives metallacyclic compounds of composition Cp(CO)Fe{HRCP(C 6 H 4 )Ph 2 } (R = H ( 3a ), R = CH 3 ( 3b ), R = C 2 H 5 ( 3c )) in the case of alkylidene ylides and Cp(CO)(PPh 3 )FeCH 2 Ph ( 5 ) with the benzylidene ylide (R = C 6 H 5 ). In the presence of a large excess of n-butyllithium, a twofold excess of Ph 3 PCHPh reacts with 1a to give the compound C 32 H 23 FeO 2 P ( 6 ) characterized by spectroscopic data and an X-ray diffraction study. In 6 an η 3 -cyclopentyl ring is coordinated to the iron atom together with two CO ligands, a phenyl ring and an ylidic carbon atom. Also characterized by an X-ray diffraction study was 3c , which was found to have a metallacycle containing an iron and a phosphorous atom, the ylidic carbon and two carbon atoms from one “phenyl” ring of the PPh 3 group as ring members. Reaction of (CH 3 ) 2 PhPCH 2 ·LiI with 1a gives extremely air-sensitive monophosphonioalkyl complex {(ηCo) 2 [CpFe(CO)][CpFeL]} ( 8 ) (L = Me 3 PCH 2 ). Some mechanistic considerations on the various reaction types of 1a based on the data obtained are presented.