Liquid ammonia coordination complexes

A novel cadmate complex has been formed by the reaction of Cd(NH2>2 with I C=CH in the presence of acetylene in liquid ammonia.250 The potassium salt, K2Gd(CCH)4-2NH3 191, has been structurally characterized. The cadmium center is tetrahedrally coordinated to four acetylide units with which it forms Cd-C bonds of 2.23-2.25 A (Figure 29). The acetylide ligands are 7r-coordinated to two crystallographically distinct potassium ions whose coordination sphere is completed by two ammonia molecules. 

A type of deprotonation reaction that takes place in liquid ammonia but not in water occurs because it is possible to utilize the base strength of the amide ion. The reaction involves removing H+ from a molecule of ethylenediamine, H2NCH2CH2NH2 (written as en), that is coordinated to Pt2+ in the complex [Pt(en)2]2+. 

Several lanthanide cyclooctatetraene complexes have been synthesized, including both the divalent metal complexes Eu(CgHg) and Yb(CgH8) 44), and the trivalent complexes [M(CgH8)2] (M =Ce, Pr, Nd, SmorTb) 35). The former were preprired by direct reaction of the metal with cyclooctatetraene in liquid ammonia. No structural data exist for these divalent compounds, but they probably involve some kind of bridging interaction since, even with coordinated solvent, one COT... 

Whilst what has been termed the real scientific advancement in this area took place in 1967,5 complexes of alkali and alkaline earth metal cations (M"+) with simple monodentate ligands can be traced back, through the metal-ammonias , to Faraday.10 It was not until almost a century later, however, that precise determinations of the stoichiometries of the M"+—NH3 products were realized and the term coordination was introduced to describe the bonding mode of the ligand.11"13 The alkali metals themselves were first noted to dissolve in liquid ammonia in 186314 and since that time it has been found that the metals also dissolve in amines and ethers.15... 

Deprotonation reactions. Ethylenediamine, H2NCH2CH2NH2, (abbreviated as en in writing formulas for complexes) forms many stable complexes with metal ions. One such complex is [Pt(en)2]2+. The amide ion will remove protons from the coordinated en so in liquid ammonia the reaction... 

Decaborate complexes of Yb(II), Eu(II) and Sm(II) of the formula [CH3CN)6Yb-(B10H14)] have been synthesized [266] by the reduction of B10H14 by lanthanides in liquid ammonia. The product is extracted with CH3CN. The boron cage is bound to lanthanide through Ln-H-B bonds. The synthetic scheme is shown below. The Yb complex has been shown to be 8-coordinate in the solid state and its molecular structure has been determined. 

Some typical complexes are noted in Table 6.3. COT ligands can in principle stabilize Ln(II), Ln(III) and Ln(IV) ions. The first complexes characterized were Ln(COT), where Ln = Eu(II), Yb(II) prepared by the reaction of metals with COT in liquid ammonia [227], The complex (COT)Yb(Py)3 0.5Py has a structure consisting of a three-legged stool for the coordinated ligands [228], Other Ln(II) complexes are given below. 

Certain bivalent tin salts have solubilities in nonaqueous solvents, e.g. tin(ll) chloride is soluble in many organic solvents, including alcohols, acetone, THF, and pyridine, probably to give rise to three-coordinate pyramidal [SnCl2-L]-type complexes. Other selected solubilities are SnBr2 in methanol, pyridine, or THF and tin(II) formate in H0(CH2)30H. Bivalent tin species are also solnble in acetonitrile solution, to give [Sn(MeCN) ] + (n = 2, 3, or 6), and in liquid ammonia, to give [Sn(NH2)3] . 

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