Indium cyclopentadienyls

Very recently, the synthesis and structure of pentamethylcyclopenta-dienylindium(I) have been reported (277). The golden yellow, very air-sensitive compound (CII) crystallizes in the form of monomeric units (indium-cyclopentadienyl centroid distance, 2.3 A) which are held together by an octahedral arrangement of indium atoms indicating weak indium-indium interactions (3.96 A). 

Stannous bis-cyclopentadienyl [26078-96-6] M 248.9. Purified by vacuum sublimation, and stored under dry N2. The related thallium and indium compounds are similarly prepared. 

The coordination chemistry of indium(I) received little or no attention for many years, largely no doubt because of the lack of suitable starting materials. The indium(I) halides can be easily prepared,1 but are intractable materials which readily undergo hydrolysis and disproportionation (but see Section 25.2.2.1). The only known organoindium(I) compounds are the cyclopentadienyl and methycyclopentadienyl derivatives,8 and the former has proven a useful starting point for some synthetic work. Electrochemical methods have been used either to reduce higher states, or to oxidize the metal in the presence of suitable ligands, in order to produce indium(I) species. 

In another theoretical study on metal-metal interactions in indium(I) and thallium(I) cyclopentadienyls (178), the authors interpret the short M—M contacts in the above dimers as weak donor-acceptor interactions, similar to the Sn—Sn bond in dimeric stannylenes (12) (163,175). However, they also attribute the general structural arrangement as being determined by crystal packing forces. ... 

Sodium cyclopentadienyl reacts with indium trichloride in ether, tetrahydrofuran, or dioxan, forming the volatile compound InCsHs, which may be obtained as pale yellow needles by sublimation (56). This substance does not melt sharply, but slowly decomposes and darkens at 110°. It is very sensitive to oxidation and is slightly soluble in benzene, in which decomposition takes place it is, however, rather less soluble in ether and petroleiun ether. Water has no action on the compound, but on addition of a little sulfuric acid it is vigorously decomposed. The crystals are slightly sensitive to light. In the preparation of InCsHs an intermediate product, InlCsHsls, can be isolated in very small yield as golden crystals. On sublimation at above 160° it decomposes to form the monocyclopentadienyl compound. 

Methyllithium (1.15 g, 52.2 mmole) in ether (25 mL) was added to freshly distilled cyclopentadiene (4.2 g, 63.7 mmol) in ether (30 mL) at 0 C, and the mixture was refluxed for 1 h. Indium trichloride (3.60 g, 16.3 mmol) was added to the resultant heavy white precipitate of cyclopentadienyllithium, and the mixture again refluxed (4 h), after which ether was removed under vacuum and the resultant solid dried (0.01 mmHg, 2 h). Benzene (90 mL) was added to this solid and the mixture heated to reflux. The hot solution was decanted from undissolved solid, and on cooling bright yellow crystals of tris(cyclopentadienyl)indium(III) (1.72 g) deposited. Further crystallization raised the final total yield to 65% (3.28 g)... 

While numerous homoscorpionate complexes of indium have been previously reported,578 in the last period only a limited number of papers appeared. The reaction between [InCl2(Tp )(NCMe)] and (L = cyclopentadienyl)-tris(diorganylphosphi(ni)to-P)cobaltate(l-),... 

Treatment of InClj with excess of sodium cyclopentadienide in THF, followed by sublimation affords Cpin rather than Cpjin, which is formed in very low yield as a by-product. Cpjin can be prepared using LiCp and InClj, but it is rather unstable. The indium atom in CpIn has a non-bonding pair of electrons and hence forms a 1 1 adduct with boron trifiuoride. (cf. p. 292). In the vapour it is monomeric, and has symmetry. In the solid, however, it polymerizes into chains via bridging cyclopentadienyl groups. 

Yb (OT 1)3(10 mol%) was recently used to catalyze the cycloaddition of alkylated cyclopen-tadienes, obtained as intermediates in the addition reaction of aldehydes to cyclopentadienyl indium(I) in aqueous medium, with dimethylacetyleneolicerboxylate. ... 

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