Michael Creswick

Übergangsmetall-methylen-komplexe : IX. Molekülstruktur von μ-methylen-bis[dicarbonyl(η5-methylcyclopentadienyl)mangan](MnMn), μCH2[(η5-CH3C5H4)Mn(CO)2]2

Abstract The structure of μ-methylenebis[dicarbonyl(η5-methylcyclopentadienyl)-manganese](MnMn) has been established by means of X-ray diffraction techniques to consist of two (η5-C5H4CH3)Mn(CO)2 fragments which are linked by a bridging CH2 ligand and a metal to metal bond. Dimetallacyclopropanes of this type can easily be distinguished from the related Fischer-type carbenes as well as from μ-alkylidene complexes without metalmetal bonds by 13C NMR spectroscopy.

The preparation und unusual rearrangement of triply bridged μ-heteromethylenecobalt complexes. Molecular structure of μ-ethoxycarbonylmethylenebis[carbonyl-(η5-cyclopentadienyl)cobalt] (CoCo)

Abstract the μ-heteromethylenecobalt complexes, which have been synthesized by photolysis of (η5-C5H5)Co(CO)2 in the presence of the corresponding diazoacetates at

The absolute configurations of organometallic compounds. XX. The conformations and absolute configurations of four preferred and non-preferred diastereoisomers having composition (R″-C5H4)Mo(CO)2[(HCPhR)N(CPh)N(HCPhR′)]

Abstract The structures and absolute configurations of four optically resolved compounds having composition (R″-C5H4)Mo(CO)2[(HCPhR)N(HCPh-R′)] were established by X-ray diffraction methods. Benz I [R″ = R′ = H, R = −CH3]: triclinic, space group P1; a = 9.792(3), b = 11. 875(4), c = 11.885(3) A, α = 88.27(2), β = 67.42(2) and γ = 83.71°. Cell volume = 1268.21 A3, Z = 2 molecules/unit cell. Benz II [R″ = R′ = H, R = −CH3]: orthorhombic, space group P212121; a = 9.885(3), b = 11.550(5), c = 22.620(9) A Cell volume = 2623.67 A3, Z = 4 molecules/unit cell. Benz I and II are of identical composition and differ only in conformation at the (−CH(CH3)Ph) substituent of the benzamidine ligand, the former being the thermodynamically preffered stereoisomer. Benz III differs from Benz I and Benz II in that both nitrogens of the benzamidine ligand bear optically active substituents of composition (−CH(CH3)Ph); therefor R″ = H and R′ = R = −Ch3. The substance crystallizes in the space group P212121 with a = 9.656(2), b = 11.691(7) and c= 23.562(6) A. Cell volume = 2660.08 A3 and Z =4 molecules/unit cell. Like Benz II, this is also a non-preferred stereoisomer. Finally, Benz IV, like Benz III, has optically active substituents at both benzamidine ligand nitrogens, but also bears a methyl substituent at Cp; i.e., R″ = R′ = R = CH3. Orthorhombic, P212121; a= 9.737(7), b = 11.716(4) and c = 23.661(9) A. Cell volume = 2698.96 A3, Z = 4 molecules/unit cell. This is also a non-preferred stereoisomer. For the convenience of the reader, all of this terminology is reviewed in the Introduction. The two independent molecules in the asymmetric unit of Benz I (Benz Ia and Benz Ib) have essentially identical bond lengths and angels and slightly different inter-planar angels associated with the phenyl rings, which have large areas over which packing forces can exert substantial torsional pressures. Benz II, III and IV also have few differences among themselves or with Benz Ia and Benz Ib insofar as bond lengths and angels are concerned, but differ somewhat in their interplanar angels in the same manner described for Benz I. Details of conformational and configurational problems in this series are given in the text.

Ring contraction and double α-addition of cationic (C5H5)Mo(CO)2 (Schiff Base Chelate) complexes: The crystal and molecular structures of (η-5C5H5)Mo(CO)[η2-NH(CH3)C(NC5H4)C6H5] [η2-OCH(C6H5]

Abstract The structure of racemic [η5-C5H5)]Mo(CO)[η2-NH(CH3)C(NC5H4)C6H5] [η2-OCH6H5] was determined from single crystal X-ray diffraction data. The compound crystallizes in space group P 1 (z = 2) with a = 9.035(6), b = 12.314(6), c = 13.220(5) A, α = 65.91(4), β = 71.40(4), γ = 72.42(4)°; cell volume 1246.97 A3. The Mo atom sits at the center of a Cp-capped trigonal pyramid with a terminal carbonyl group, an η2-aminomethylene and an η2-benzaldehyde moiety as basal ligands. Structural features indicate that both η2-ligands act as π-acids, accepting Mo electron density through their hetero atoms.

On the absolute configuration of organometallic compounds. X. A comparison of structures for racemic (η5-C5H5)Mo(CO)2SC(CH3)N[CH(C2H5)C6H5] and (+)579-(η5-C5H5)Mo(CO)2SC(α-C10H7)N[(S)-CH(CH3)C6H5] ☆

Abstract The crystal and molecular structures of two compounds of composition (η-C 5 H 5 )Mo(CO 2 SC(R)N(R′) were determined by X-ray diffraction (MoKα) measurements carried out at room temperature. Compound (I), the racemic compound, with R = CH 3 and R′ = CH(C 2 H 5 )C 6 H 5 , crystallizes in space group P 1 (Z = 2) and cell parameters: a = 9.264(2), b = 9.350(2), c = 12.592(5) A , α = 76.24(3), β = 77.11(3) and γ = 58.83(2)°; V = 899.84 A 3 . A refinement of 284 parameters, using 3415 observed [I > 2σ(I)], gave the conventional agreement factors R = 0.028 and R ω = 0.035. The two enantiomers in the unit cell are assigned chirality indicators ( vide infra ) of (S; Mo)(S; C) and (R; Mo)(R; C). Compound (II), an optically pure diastereoisomer characterized by a (+) rotational strength at 578 nm, has R = α-C 10 H 7 -(naphthyl) and R′ = ( S )-CH(CH 3 )C 6 H 5 . It crystallizes in the space group P2 1 2 1 2 1 (Z = 4) with a = 10.028(3), b = 12.532(7) and c = 17.774(6) A ; V = 2236.46 A 3 . Refinement (171 variables using 3160 reflections having I > 2σ(I) gave R = 0.018 and R w = 0.019. The absolute configuration, determined by the Bijvoet method, assigns chirality indicators of ( R ; Mo)( S ; C) to the two sites of this, non- preferred, diastereoisomer.

Conformational analysis and chirality transmission in organometallic compounds: X-ray structure analysis of C5H5(CO)2MoN(CH2C6H5)C(C6H5)N[CH(CH3)(C6H5)]

Abstract The structure and absolute configuration of C 5 H 5 (CO) 2 MoN(CH 2 C 6 H 5 )- C(C 6 H 5 )N[CH(CH 3 )(C 6 H 5 )] was determined to establish the rules governing the conformation of chiral substituents on chelate rings.

Notizen: Studies on Metal-Metal Bonds, VI /Observations on the EAN Rule and Bond Orders for Mn-Mn Compounds

The metal metal distances of a representative number of organometallic manganese complexes vary from 2.50 Å to 3.23 Å, although all these compounds are predicted by the EAN Rule to possess single metal to metal bonds. It is no longer acceptable to predict bond orders from bond lengths, and vice versa.

Übergangsmetall-Methylen-Komplexe, X [1] Methylen-und Alkyl-Eisen-Komplexe aus Diazoalkanen. Molekülstruktur von μ-Carbonyl-μ-tert-butoxycarbonyl-methylen- bis [carbonyl(η5 -cyclopentadienyl)eisen] (Fe-Fe)/Transition Metal Methylene Complexes, X [1] Methylene and Alkyl Iron Complexes from Diazoalkanes. Molecular Structure of μ-Carbonyl-μ-tert-butoxycarbonyl-methylene- bis[carbonyl(η5-cyclopentadienyl)iron] (Fe-Fe)

Abstract The novel doubly bridged μ-methylene iron complexes μ-[C(H)CO2R]-μ-CO[(η5-C5H5)Fe(CO)]2 (R = C2H5: 3a; R = tC4H9: 3b) have been synthesized by low-temperature photolysis of the corresponding alkyldiazoacetates 2a and 2b, resp., in the presence of [(η5-C5H5)Fe(CO)2]2 (1) and characterized by means of their analytical data and IR, 1H NMR and mass spectroscopy. The geometry of 3b has been established by single crystal X-ray diffraction techniques. δ-Alkyl iron complexes of the type (η5-C5H5)Fe(CO)2[CHRRʹ] are accessible from the corresponding diazoalkanes N2 = CRRʹ.