Chemical shift coordinate derivatives

The six-coordinate [RTp]SnR Cl3 n derivatives are typically characterized by 119Sn NMR signals in the range -195 to - 670 ppm (relative to Me4Sn) (115,118,120,121), while five-coordinate [RBp]SnR Cl3 n complexes exhibit shifts to lower field in the range -103 to -182 ppm (115). For [Tp lSnR derivatives, the 119Sn chemical shift was also determined to be a linear function of n (120). 

Phospha(thia)zenes with four coordinate sulfur atoms continue to exhibit interesting chemical and biological properties. The reactions of NPC12(NSOX)2 (X=Ph,Cl,F) with the aliphatic difunctional reagents NH2(CH2)2 3YH (y=NH, O) give the spirocyclic derivatives NP[NH(CH2)2 3Y] (NSOX) 2. The " P nmr chemical shifts of... 

The derivatives 15a-i exhibit characteristic 31P NMR spectroscopic data (see Table I), which are distinctly different from those observed for the P-organo-substituted derivatives 12 and 13 (8(3IP) = 65.8-136.0).27 However, the similar Si chemical shifts and. /(Si, P) coupling constants observed for 12,13, and 15 clearly show the identical electronic nature of the low-coordinate silicon centers in these derivatives. 

In addition to these low field resonances the chemical shift of the coordinated methyl group falls at —0.19 and the methyl portion of the coordinated ethyl group has a chemical shift of —0.61. By comparing these numbers with the chemical shifts of the ethyl protons in the analogous ethyl porphyrin derivative (129), in which the resonance positions are all above —5, it has been concluded that there is little or no ring current in the corrin ligand system. 

In Sn(II) complexes, the tin atom was located above the di-Schiff base coordination plane, while in Sn(IV) complexes, it was coplanar with the imine coordination framework. The position of the metal was supported by X-ray data. For the compounds studied, the 119Sn chemical shift values varied from 501.4 to —1015.9 ppm. Increase in the coordination number from Sn(II) to Sn(IV) led to an increase in the tin shielding. The differences of up to 3.0 ppm between 5119Sn values for the complexes, being derivatives of R,R and S,S 1,2-diaminocyclohexane, were observed. 

For the tin(II) complexes of the fluorinated Schiff bases derived from amino acids, [47] the 5119Sn chemical shifts in the range from -575 to 582 ppm suggested the four-coordinate square-planar geometry.111... 

Analysis of the 27A1 NMR spectra has confirmed the structure of the aluminium di-Schiff bases complexes being derivatives of trans-1,2-dia-minocyclohexane. The A1 chemical shift values of 6.57 and 39.48 ppm indicated the presence of dynamic equilibrium between five- and six-coordinated states in CDC13 solution. 

These shifts are similar to the 29Si chemical shifts in the spectra of silyl derivatives of analogous oximes. This is evidence for the absence of essential additional coordination of silicon in SENAs. The qualitative and quantitative analyses of the 29Si NMR signal can be considered as a simple method of NMR monitoring of SENAs in solution. 

In particular, in Cd(II)-Thermolysin derivative (a zinc metaUoprotease with proteolytic activity similar to carboxypeptidase A), the X-ray structure has provided evidence for isostructural replacement of Zn(II) by Cd(II). In general, the " Cd chemical shift is very sensitive to the nature, number and coordination type of the amino acid ligands and " Cd resonances are commonly detected by direct observation (/ = V2, and 63% sensitivity compared with C) or by inverse detection of Cd scalar-coupled to H. 

Different behavior was found for the p-toluenesulfonate and chloride derivatives containing ligands derived from pyrimidine. This could be due to a competitive coordination of these anions against the heterocyclic ligands. For the chloride complexes, a clear resonance broadening is observed at room temperature. Considering the chemical shifts it must be accepted that the free ligand is the dominant species. 

Chiral Metal Atoms in Optically Active Organo-Transition-Metal Compounds, 18, 151 13C NMR Chemical Shifts and Coupling Constants of Organometallic Compounds, 12, 135 Compounds Derived from Alkynes and Carbonyl Complexes of Cobalt, 12, 323 Conjugate Addition of Grignard Reagents to Aromatic Systems, I, 221 Coordination of Unsaturated Molecules to Transition Metals, 14, 33 Cyclobutadiene Metal Complexes, 4, 95 Cyclopentadienyl Metal Compounds, 2, 365... 

In the case of cobalt substituted Zn-fingers [102], the differences between the chemical shifts for corresponding resonances in the Co(II) and Zn(II) complexes allow the determination of the orientation and anisotropy of the magnetic susceptibility tensor [103]. Similar studies are available for pseudotetrahedral Co(II) in the zinc site of superoxide dismutase [104] and five coordinated carbonic anhydrase derivatives [105]. 

Chemical interactions with solvents Various workers have observed (1, 4, 7) that five- and six-coordinate organotin compounds show U9Sn signals which occur at much lower frequencies than those of the four-coordinate derivatives. For this reason, the choice of solvent in preparing samples for NMR measurements may affect the value of the observed u9Sn chemical shift. 

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