Phosphorus-31, mercury-199 and selenium-77 n.m.r. studies of ligand exchange reactions in mercury(II) halide complexes

1980 ◽  
Vol 33 (7) ◽  
pp. 1463 ◽  
Author(s):  
R Colton ◽  
D Dakternieks
Keyword(s):  
Time Scale ◽  
Ligand Exchange ◽  
Room Temperature ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Exchange Reactions ◽  
Halogen Exchange ◽  
Redistribution Reactions ◽  
Halide Complexes

Mercury(II) halide complexes of tris(4-methoxyphenyl)phosphine have been investigated by 31P and 199Hg n.m.r. spectroscopy of CH2Cl2 solutions. At room temperature the phosphine exchanges at an appreciable rate and halogen exchange is fast. At -50°C both phosphine and halogen exchange are slow on the n.m.r. time scale and halogen redistribution reactions are observed. ��� Mercury(II) halide complexes with tributylphosphine selenide have been investigated by 31P, 199Hg and 77Se n.m.r. methods. This ligand is labile and exchanges rapidly on the n.m.r. time scale at room temperature, although the exchange can be slowed down at about -100°C. Halogen exchange is also fast at room temperature. ��� Ligand exchange reactions between tributylphosphine and either tris(4-methoxyphenyl)phosphine or tributylphosphine selenide were investigated and redistribution reactions to give mixed ligand complexes were observed.

Phosphorus-31, cadmium-111, cadmium-113 and mercury-199 N.M.R. studies of cadmium(II) halide and mixed cadmium(II)-mercury(II) halide complexes with tributylphosphine

1980 ◽  
Vol 33 (8) ◽  
pp. 1677 ◽  
Author(s):  
R Colton ◽  
D Dakternieks
Keyword(s):  
Metal Complexes ◽  
Time Scale ◽  
Room Temperature ◽  
Chemical Shifts ◽  
Coupling Constant ◽  
Mixed Metal ◽  
Redistribution Reactions ◽  
Halide Complexes ◽  
Mixed Metal Complexes ◽  
And Shifts

Phosphorus-31, cadmium-111 and cadmium-113 n.m.r, studies have been carried out on CdX2(PBu3)2 (where X = Cl, Br, I). The results are consistent with exchange of both phosphine and halogen. Phosphine exchange becomes slow on the N.M.R. time scale in all cases by -40°C. Mixtures of CdX2(PBu3)2 with different halogens give averaged signals at room temperature, but below about -80°C exchange becomes slow and halogen redistribution reactions can be observed. ��� Reaction of CdX2 and PBu3 in 1 : 1 proportions in ethanol gives Cd2X4(PBu3)3 as the isolated product, not Cd2X4(PBu3)2. It is shown that ethanol is an effective ligand to cadmium and redistribution reactions between coordinated ethanol and the phosphine occur. ��� The mixed metal complexes CdHgX4(PBu3)2 have been shown by phosphorus-31, cadmium-113 and mercury-199 n.m.r, studies to have all the phosphine coordinated to mercury. ��� Cadmium-111 and cadmium-113 chemical shifts in these compounds span a range of over 500 ppm and shifts have been correlated with 31P chemical shifts and the coupling constant JP,Cd.

Darstellung und Schwingungsspektren von Chloro-Bromo-Platinaten(IV) einschließlich der Stereoisomeren / Preparation and Vibrational Spectra of Chloro-Bromo-Platinates(IV) Including Stereoisomers

1982 ◽  
Vol 37 (5) ◽  
pp. 579-586 ◽  
Author(s):  
W. Preetz ◽  
G. Rimkus
Keyword(s):  
Vibrational Spectra ◽  
Ligand Exchange ◽  
Critical Discussion ◽  
Exchange Chromatography ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Exchange Reactions ◽  
Separation Processes ◽  
Point Groups ◽  
Better Than

The mixed chloro-bromo complexes [PtClnBr6-n]2-, n = 1-5, are separated by ion exchange chromatography on diethylaminoethylcellulose. The separation of corresponding stereoisomers for n = 2, 3, 4 is not possible. Due to the stronger trans-effect of Br compared with Cl, on treatment of [PtBrß]2- with Cl- in the presence of Br2 nearly pure cis-isomers, and by reaction of [PtClsBr]2- and cis-fPtC^Bro]2- with Br~/Br2 completely pure transisomers are formed. The stereoselectivity of the successive ligand exchange reactions is better than in corresponding series of Re, Os and Ir. The highly resolved vibrational spectra allow the distinction of the mixed ligand complexes as well as the estimation of purity of the isomers. All allowed stretching frequencies are observed and assigned according to point groups D4h, C4V, C3V and C2V. Especially in the ν(Pt-Br) region it is possible to distinguish bands arising either from symmetric Br-Pt-Br or asymmetric Cl-Pt-Br axes. The UV/VIS spectra exhibit systematic hypsochromic shifts on the successive exchange of Br-ligands by Cl. A critical discussion of the literature concerning chloro-bromo-platinates- (IV) shows the importance of effective separation processes for the isolation of pure mixed ligand complexes

Tieftemperatur-Raman-Messungen an bewegten Proben bei 10 K am Beispiel der Isotopomeren Cs2[Pt35Cln37Cl6-n, n = 0-6 / Low-Temperature Raman Measurements on Moved Samples at 10 K Exemplified by the Isotopomers Cs2[Pt35Cln 37Cl6-n], n = 0-6

1993 ◽  
Vol 48 (12) ◽  
pp. 1737-1741 ◽  
Author(s):  
W. Preetz ◽  
E. Parzich
Keyword(s):  
Low Temperature ◽  
Ligand Exchange ◽  
Room Temperature ◽  
Valence Vibration ◽  
Closed Cycle ◽  
Exchange Reactions ◽  
Normal Coordinate ◽  
Point Groups ◽  
Isotopic Effects ◽  
Good Agreement

A technique to record Raman spectra of deeply coloured solids at low temperature (10 K) is described, using a closed cycle He-cryogenerator and moving the cell by an excentric attachment. The spectroscopic resolution is considerably enhanced as compared to room temperature or 80 K measurements. This is obvious from splittings of Raman lines observed at 10 K on the isotopomers Cs2[Pt35Cln37Cl6-n], n = 1 -5, which have been prepared by stereospecific ligand exchange reactions. As a consequence of lowered symmetry the degenerate valence vibration v2(Eg, Oh) is split into two lines for the isotopomers belonging to the point groups D4h, C4v and C2v. The isotopic effects calculated by normal coordinate analysis are in good agreement with the observed frequencies.

Darstellung und Charakterisierung der Chloro-Bromo-Iridate(III) und -(IV) einschließlich der Stereoisomeren / Preparation and Characterisation of Chloro-Bromo-Iridates(III) and -(IV) Including Stereoisomers

1985 ◽  
Vol 40 (6) ◽  
pp. 745-754 ◽  
Author(s):  
W. Preetz ◽  
H.-J. Steinebach
Keyword(s):  
Ligand Exchange ◽  
Redox Reactions ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Mixed Ligand ◽  
Redox Potentials ◽  
Exchange Reactions ◽  
Cyclic Voltammetric ◽  
Point Groups ◽  
Voltammetric Measurements

AbstractThe mixed chloro-bromo complexes [IrClnBr6-n]2- and [IrClnBr6-n]3-, n = 1 - 5. were separated by ion exchange chromatography on diethylaminoethylcellulose. Due to the stronger trans-effect of Br compared with Cl, on treatment of [IrBr6]2- 3- with Cl- nearly pure cis/fac-isomers and by reaction of [IrCl6]2,3- with Br- trans/mer-isomers for n = 2,3,4 were formed. The stereoselectivi­ty of successive ligand exchange reactions is better for the Ir(III) than for the Ir(IV) system. The diamagnetic Ir(III) and the paramagnetic Ir(IV) complexes can be interconverted reversibly by redox reactions at low temperature. As shown by cyclic voltammetric measurements, the redox potentials within the series [IrClnBr6-n]2- 3- are linearly dependent on n. In aqueous solution the normal potentials are in the range of Eo = 0.838 V ([IrBr6]2-,3-) to Eo = 0.908 V ([IrCl6]2-,3-). The vibrational spectra of the mixed ligand complexes are assigned according to point groups D4h, C4v, C3v and C2v. They are similar for corresponding chloro-bromo-iridates, but distinguished by a shift of 10-25 cm-1 to higher wave numbers for most of the stretching vibrations going from Ir(III) to Ir(IV).

Phosphorus-31 and Mercury-199 N.M.R. studies on mercury(II) halidetributylphosphine complexes

1980 ◽  
Vol 33 (5) ◽  
pp. 955 ◽  
Author(s):  
R Colton ◽  
D Dakternieks
Keyword(s):  
Low Temperature ◽  
Time Scale ◽  
Slow Rate ◽  
Room Temperature ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Slowing Down ◽  
Halogen Exchange ◽  
And Shifts

Phosphorus-31 and mercury-199 N.M.R. studies have been carried out on HgX2P2,Hg2X4P2, mixtures thereof and the oligomers Hg2X4P3, Hg3X6P2 and Hg4X8P2 where X = Cl, Br, I and P = tributyl-phosphine. The results are consistent with exchange of both phosphine and halogen. The phosphine exchanges slowly on the N.M.R. time scale at room temperature, but rapidly on the preparative time scale. Halogen exchange is fast on both the N.M.R. and preparative time scales at room temperature; cooling to -120°C reduces exchange of terminal halogens to a slow rate on the n.m.r. time scale. Increase in the coupling constant JP,Hg at low temperature is attributed to the slowing down of halogen exchange. Exchange of bridging halogens is still fast at -120°C. ��� Mercury-199 chemical shifts span a range of over 3000 ppm and shifts have been correlated with 31P chemical shifts and with the coupling constants JP,Hg The 199Hg n.m.r. data confirm the existence of an asymmetrical isomer of Hg2I4(PBu3)2.

CYCLOBUTADIENE–METAL COMPLEXES: PART VIII. SYNTHESIS OF TETRAPHENYLCYCLOBUTADIENE NICKEL HALIDES BY LIGAND-EXCHANGE REACTIONS

1966 ◽  
Vol 44 (22) ◽  
pp. 2673-2677 ◽  
Author(s):  
D. F. Pollock ◽  
P. M. Maitlis
Keyword(s):  
Metal Complex ◽  
Metal Complexes ◽  
Ligand Exchange ◽  
Palladium Complexes ◽  
Exchange Reactions ◽  
Reaction Proceeds ◽  
Halide Complexes

The preparation of cyclobutadiene nickel halide complexes (R4C4NiX2)2, where R is phenyl or substituted phenyl, by reaction of the palladium complexes, [R4C4PdX2]2, with a tert-phosphine metal complex, e.g. (n-Bu3P)2NiX2, is described. The reaction proceeds according to the equation[Formula: see text]Possible mechanisms are suggested.

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