Carbonyliron-Lead Complexes: Multinuclear Magnetic Resonance Study in Solution and X-Ray Structure Determination of [Et2PbFe(CO)4]2

1994 ◽  
Vol 49 (12) ◽  
pp. 1781-1788 ◽  
Author(s):  
Max Herberhold ◽  
Volker Tröbs ◽  
Wolfgang Milius ◽  
Bernd Wrackmeyer
Keyword(s):  
Magnetic Resonance ◽  
Structure Determination ◽  
2D Nmr ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Geminal Coupling ◽  
Multinuclear Magnetic Resonance

Complexes of the types R3Pb-Fe(CO)2Cp [R=Me (a). Et (1b), iPr (lc), iBu (Id)]. R2Pb[Fe(CO)2Cp]2 [R=Me (2a), Et (2b)], iPr2(Br)Pb-Fe(CO)2Cp (3c) and [R2PbFe(CO)4]2 [R=Me (4a), Et (4b). iPr (4c)], as well as the spiro-complexes Pb[Fe(CO)4PbR2]2 [R = Me (5a). Et (5b). iPr (5c)] and Pb[Fe(CO)4]4 (6) were studied by multinuclear magnetic resonance spectroscopy (1H. 13C, 207Pb NMR). For the first time, coupling constants 1J(207Pb57Fe) were determined, covering a range between 33.5 (6) and 117 Hz (4a). The magnitude of the geminal coupling constants ∣2J(207Pb207Pb) ∣ in the spiro-compounds 5 decreases from 1090.0 Hz (5a) to 377.0 Hz (5c). The signs of the coupling constants nJ(207Pb13C(R)) (n = 1, 2) and nJ(207Pb1H(R)) (n = 2, 3) were determined by various 2D NMR experiments. Among all known Pb(IV) compounds the lowest 207Pb nuclear magnetic shielding was found in Pb[Fe(CO)4]4 (6): δ207Pb +3586.6. According to the single crystal X-ray structure determination of 4b (orthorhombic; space group Pbca; a = 967.4, b = 1367.7, c = 1772.4 pm), the Pb2Fe2 ring is planar with bond angles FePbFe = 102.8° and PbFePb = 77.2°, and there is a relatively short transannular distance of 340.8 pm between the two lead atoms.

Étude conformationnelle de cétopipérazines: (I) 3R-méthyl-6-carbéthoxy-2 oxopipérazine, (II) 3R-[p-hydroxybenzyl]-6-carbéthoxy-2 oxopipérazine: I, II en solution et structure cristalline de II

1987 ◽  
Vol 65 (6) ◽  
pp. 1308-1312 ◽  
Author(s):  
André Michel ◽  
Guy Evrard ◽  
B. Norberg
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Absolute Configuration ◽  
Structure Determination ◽  
Opiate Receptor ◽  
Receptor Level ◽  
X Ray ◽  
Diastereomeric Mixture ◽  
The Absolute

The synthesis of the title compounds has been described recently. It was anticipated that the product would be a diastereomeric mixture. Surprisingly, only one isomer was obtained. The present work is an attempt to find the conformationnal properties accounting for those observations. X-ray structure determination of 3R-[p-hydroxybenzyl]-6-carbethoxy-2-oxopiperazine shows that the molecule adopts a folded conformation and that the absolute configuration at C6 is [R]. Investigation in solution using 1H nuclear magnetic resonance shows the existence of three conformers and discusses the relative populations. Those findings are also relevant in terms of the activity of such compounds at the opiate receptor level.

Kristallstruktur von Cs2[B6H5(SCN)]/ Crystal Structure of Cs2[B6H5(SCN)]

1998 ◽  
Vol 53 (8) ◽  
pp. 816-818 ◽  
Author(s):  
W. Preetz ◽  
S. Zander ◽  
C. Bruhn
Keyword(s):  
Crystal Structure ◽  
Ion Exchange ◽  
Structure Determination ◽  
Deae Cellulose ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray

Abstract By reaction of [B6H6]2-with (SCN)2 in dichloromethane at -80 C° the thiocyanatohexaborate anion is formed and can be isolated by ion exchange chromatography on diethylaminoethyl (DEAE) cellulose. The X-ray structure determination of Cs2[B6H5(SCN)] (orthorhombic, space group Pbca with a = 9.506(5), b = 10.644(5), c = 21.857(5) Å, Z = 8) reveals that the SCN substituent is bonded via the S atom with the B-S distance of 1.885(9) Å and the B-S-C angle of 99.8(5)°. The SCN group is nearly linear (179.9(9)°).

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