| | 1 | Author
| Dieter Rehder, Hans-Christoph Bechthold, Ahmet Keçeci, Hartwig Schmidt, Michael Siewing | Requires cookie* | | | Title
| A Comparative Study of Metal Shielding in Low Valent Vanadium, Niobium and Manganese Complexes  | | | | Abstract
| Variations of the metal chemical shifts <5(51 V), <5(55 Mn) and <S(93 Nb) with the para-magnetic deshielding contribution to the overall shielding are discussed in terms of influences imposed by the ligand field splitting, the nephelauxetic effect and the covalency of the metal-to-ligand bond. Complexes under investigation are isoelectronic and/or iso-structural series [M(CO)6_nL"]<i (M = V, Nb: q = —1; M = Mn: q = + 1; n = 0-6), 7? 5 -C5H5M(CO)4-KLn (M = V, Nb; n = 0-4) and r? 5 -C5H5M(L /)2L (M = V, L' = NO; M = Mn, L' = CO). L is a monodentate or l/n oligodentate phosphine. <5 varies with the point symmetry of the complex, and with ligand parameters of primarily electronic or steric origin. Generally, for weak to medium ^-interaction, there is a decrease of shielding with decreasing yr-acceptor power of the ligand, increasing ligand bulkiness, increasing ring strains in chelate structures and increasing degree of substitution. For strong ^-inter-action, the trends may be interconverted. PF3 is shown to be a slightly weaker 7r-acceptor than CO. Selected results on nuclear-spin spin coupling constants, 13 C and 31 P shielding are also presented. | | | |
Reference
| Z. Naturforsch. 37b, 631—645 (1982); eingegangen am 25. November 1981 | | | |
Published
| 1982 | | | |
Keywords
| Carbonylphosphinevanadium, Carbonylphosphineniobium, Carbonylphosphinemanganese, NMR Spectra | | | |
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| default:Reihe_B/37/ZNB-1982-37b-0631.pdf | | | | Identifier
| ZNB-1982-37b-0631 | | | | Volume
| 37 | |
| 2 | Author
| Ahmet Keçeci, Dieter Rehder | Requires cookie* | | | Title
| IR, 31 P-, 55 Mn-und 185 187 Re-NMR spektroskopische Untersuchungen an einigen Carbonylmangan-und -rhenium-Komplexen | | | | Abstract
| The IR and NMR spectra of the complexes [M(CO)e]Cl • HCl (M = Mn: 1, M = Re: 2), M(C0)5C02Et (M = Mn: 3, M = Re: 4), [Mn(CO)5PR3][PF6] (5; PR3 = PPh(OPh)2: a, P(n-Pr)3: b, PHPh2: c, PPh(NEt2)2: d, P(p-C6H4F)3: e), [Be(CO)5PHPh8][FF6] (6 c), Mn2(CO)s(PR3)2 (7) and Re2(CO)g(PHPh2)2 (8c) are discussed in the context of a-and ^-interactions in the metal-ligand system and compared with 51 V NMR data of the analogous isoelectronic and isostructural carbonylvanadates (—I). On the basis of these results, the phosphines are arranged in the order of decreasing integral ligand strength according to a>b>c>d. The 55 Mn shielding of 5 is greater than that of 1, which is explained by strong (x-interactions and correspondingly large e-ai* splitting dominating the paramagnetic deshielding term in the pseudooctahedral complexes of type 5. The only rhenium compound accessible to NMR is 2, for which the 185 Re and 187 Re resonances were obtained. 31 P coordination shifts are positive for all complexes. Spectroscopic data for 7c show that this complex presumably has the structure (CO)sMn-Mn(CO)3(PHPh2)2, contrasting 7 a, 7 b, 7d and 7e (local D4d symmetry). | | | |
Reference
| (Z. Naturforsch. 36b, 20—26 [1981]; eingegangen am 6. Oktober 1980) | | | |
Published
| 1981 | | | |
Keywords
| Carbonylphosphinemanganese, Car bony lphosphinerhenium, IR Spectra, Manganese NMR Spectra, Rhenium NMR Spectra | | | |
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| default:Reihe_B/36/ZNB-1981-36b-0020.pdf | | | | Identifier
| ZNB-1981-36b-0020 | | | | Volume
| 36 | |
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