lron(ii) complexes of the pentadentate ligand N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-l,2diamine ( L2) and the potentially hexadentate ligand N.N'-bis(6-methyl-2-pyridylmethyl) -N,N'-bis(2pyridylmethyl)ethane-1,2-diamine (L') have been isolated. Both ligands behave as pentadentate ligands in their iron(ii) complexes with the general formulation [FeL(X)]"+ (L = L' or L2, n = 1 or 2) with the sixth co-ordination site (X) occupied by an auxiliary ligand e.g. H20, CI, SCN or CN. The crystal structure of [FeL1(H,0)][PF,],=H20 1 shows that the nitrogen atom of one of the 6-methyl-2pyridylmethyl groups of the formally hexadentate ligand is not co-ordinated to the iron atom. Instead a water molecu_le occupies the sixth co-ordination position. Complex 1 crystallizes in the triclinic space group P1, with a = 10.485(2), b = 13.161 (5), c = 14.853(6) A, a = 69.31 (4), p = 74.42(3), y = 66.37(3)O and Z = 2. The structure refined to a final R value of 0.052 for 2531 reflections. The complexes show peroxidase activity, the availability of a labile site on the relatively stable iron(I1) complexes, along with no apparent tendency to form 0x0-bridged diiron(ll1) species, which are likely to be crucial factors in the mechanism of the oxidation reactions. Efforts to isolate a complex with a co-ordinated peroxide in the sixth position were unsuccessful. However, we have spectroscopic evidence that peroxide reacts with the iron(I1) complexes to form an unstable species, probably of the form [Fe"'L(OOR)]2+ ( L = L1 or L2, R = H or But). The peroxide ligand in this iron(ll1) complex is likely to be forced into an 'end-on' co-ordination mode.

. Can. J. Chem. 53,1622Chem. 53, (1975. The crystal and molecular structure of bis(n-cyc1opentadienyl)titanium dichloride, (C5H5)?-TiCI,, has been determined from three dimensional X-ray data. The crystals are triclin~c with a = 7.882(5), b = 19.478(10), c = 12.156(9) A, a = 90.46(2), a = 102.58(2), y = 143.49(2)". Intensity data (3742 reflections above background) were collected by the 8-20 scan method using an automated counter diffractometer. The structure was refined in space group PI by block-diagonal least squares methods to a conventional R of 0.032. Since Z = 4, there are two symmetry independent molecules per unit cell. However, these two molecules are almost identical structurally. The coordination about the titanium atom formed by the two chlorine atoms and the centroids of the cyclopentadiene rings is that of a distorted tetrahedron. The average Ti-Cl bond distance is 2.364(3) A and Ti-Cp-(centroid) 2.058 A. The C--C distances vary from 1.339(11) to 1.419(9) A. The structural results are compared to those for similar type molecules.ABRAHAM CLEARFIELD, DAVID KEITH WARNER, CARLOS HERMAN SALDARRIAGA-MOLINA, RAMANATHAN ROPAL et IVAN BERNAL. Can. J. Chem. 53,1622 (1975.On a determine la structure cristalline et molkulaire du dichlorure de bis (n-cyclopentadiknyl) Introduction Bis(n-cyclopentadienyl)titanium(IV)dichloride, hereafter referred to as either titanocene dichloride or Cp2TiC12, was prepared in 1954 by Wilkinson and Birmingham (I), who suggested from infrared studies that the molecule contains n-bonds between the Ti and the two cyclopentadienyl moieties. In 1957, Natta et al.(2) isolated the adduct of titanocene dichloride with diethyl aluminum as part of their studies 'Portions of this paper are based on the M.S. Thesis of D. K. Warner, presented to the Chemistry Department, Ohio University, Athens, Ohio, March, 1969. of the mechanism of Ziegler catalysis in the polymerization of ethylene. The isolation of this compound was an important achievement since Natta and his associates were attempting then to show that the Ziegler catalysts for the polymerization of ethylene are, in general, bimetallic compounds containing organometallic bonds.In 1966, an electron diffraction study was reported (3) in which Cp2TiC12 was described as a prismatic sandwich in which the Cp rings are inclined towards each other at an angle of 58.5". The Ti-Cl and Cl-Ti-Cl parameters were listed as 2.24 A and 100°, respectively. 1623These results are significantly different from those obtained in single crystal, X-ray (4), and neutron (5) diffraction studies of closely related substances.In the solid state, titanocene dichloride has been studied twice by single crystal X-ray diffraction methods (6, 7). In the first report (6) no positional parameters were given. The second one (7) gives positional parameters but the results are not very accurate. For example, the C-C distances range from 1.32(4) to 1.50(4) A.Thus, for the purposes of more accurate comparisons (4, 5, 8-10) these results are not very useful. Since, at th...

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Photolysis of the manganese half‐sandwich complex (η5‐C5Me5)Mn(CO)3 (1) in tetrahydrofuran (thf) cleanly yields the solvent complex (η5‐C5Me5)Mn(CO)2(thf) (2). Compound 2 is stable as solid at temperatures well below 0°C but undergoes spontaneous elimination of carbon monoxide at ambient temperature with concomitant formation of the novel dinuclear complex (η5‐C5Me5)2‐Mn2(μ‐CO)3 (3). While elemental analysis, infrared and mass spectroscopy as well as the 1H NMR and 13C NMR spectra unequivocally demonstrate this compound to adopt a highly symmetrical triply carbonyl‐bridged structure, a single‐crystal X‐ray diffraction study supports the presence of the first triple bond between manganese atoms (dMn – Mn 217.0(1) pm). An improved synthesis of tricarbonyl(η5‐pentamethylclopentadienyl)manganese (1) is also described.

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SiHC13-reduction of ( + )-and ( -)-NorphosO, respectively, afford neutral and cationic Rh-complexes which, with H, at room temperature and atmospheric pressure within a few hours, give quantitative hydrogenation of u-(acety1amino)cinnamic acid, u-(acety1amino)acrylic acid and Dopa precursors. The optical yields vary between 79 and 97%.Chern. Ber . I I4 ( 1 98 1)

Die Halbsandwich‐Komplexe (η‐5C5H4CH3)Nb(CO)4 (3a), [η5‐C5(CH3)5]Nb(CO)4 (3b), (η5‐C5H4CH3)Ta(CO)4 (3c) und [η5‐C5(CH3)5]Ta(CO)4 (3d) sind durch reduzierende Hochdruckcarbonylierung der entsprechenden NbV‐bzw. TaV‐vorstufen (η5‐C5R4R′)MCl4 (2a‐d) synthetisierbar. Die Reduzierbarkeit der Halogeno‐Komplexe, 2a–d, wird durch sukzessive Einführung von Methyl‐Substituenten in den Cyclopentadienyl‐Ring erleichtert und ist bei den Niob‐Verbindungen mit milderen Reduktionsmitteln als bei den analogen Tantal‐Komplexen möglich. Bei der Photolyse von 3a–d in Tetrahydrofuran entstehen die Solvens‐Komplexe (η5‐C5R4R′)M(CO)3(THF) (4a–d). Die Stammsubstanz (η5‐C5H5)Nb(CO)4 (1) wurde röntgenstrukturanalytisch untersucht und besitzt eine unverzerrt tetragonal‐pyramidale Molekülstruktur.