Preparation group hydrides

Our attempts to prepare chromium hydrides and to evaluate their role in polymerization catalysis eventually led to the isolation of a series of alkyls and hydrides lacking any ancillary ligands besides the cyclopentadienyl moiety (see below).[6] Reduced to the essence of alkyls, these complexes provided another piece of evidence in the growing case against polymerization activity of divalent chromium none of the alkyls even reacted with ethylene. The hydride underwent one insertion and stopped at the stage of an ethyl group. 

The properties of some rare-earth binary alloys with platinum group metals are also important in view of the role they can play in the chain of preparing ternary hydrides. Many of the alloys of the series R-M, where R is a rare earth element and M is a Group VIIIB metal, have been investigated structurally and magnetically. The alloys with iridium all have cubic structures, whereas those... 

Main group hydrides are of particular interest in themselves but are relevant to coordination chemistry only to the extent that they are used to prepare transition metal hydrides or act as ligands. 

The 2-methyl-2-butyl cation [68] also shows degenerate properties. Prepared by hydride abstraction from n-pentane or isopentane in FSOjH-SbFj, its H-nmr spectrum was observed by Olah and Lukas (1967). The temperature dependence of the spectrum indicated scrambling of the methyl groups. A mechanism was proposed with an initial 1,2-hydride shift to the secondary... 

Beryllium hydride is covalent, similar to hydrides formed by the group IB - VB elements. Magnesium hydride is a borderline case it can be formed by direct reaction of Mg metal and as well as by the procedures used to prepare covalent hydrides (see below). 

A convenient general method of preparing Group IV hydrides, simple and substituted, is by the action of lithium aluminium hydride on the appropriate halide in ether solution ... 

The purpose of this chapter is to survey very briefly the general features of the occurrence, preparations and properties of hydrides. Specific compounds will be covered under each element in Volumes 2-4. We have concentrated on transition metal hydrides but also briefly mention some features of main group hydride chemistry. Useful reviews have appeared on various aspects of metal hydride complexes. One by M. L. H. and J. C. Green in Comprehensive Inorganic Chemistry has very useful lists of compounds but dates from 1973. Teller and Bau" have covered the structural data on metal hydrides and give extensive tabulations of structural data. Humphries and Kaesz have considered cluster hydrides, especially in terms of their reactivity. Hlatky and Crabtree have reviewed polyhydrides. In each of these reviews, the authors have extensively tabulated the relevant data. We shall try to avoid duplication by emphasizing areas not previously covered. 

A survey of the literature has revealed that many of the various methods reported for the preparation of metal nanopartides are applicable to a number of metals across the Periodic Table. For example, salt reduction using main group hydride-reducing agents has been used for the preparation of many metals in nanosized form (not only those cited in this subchapter). It is not the goal here to provide a directory of all reports of nanopartides syntheses, but rather to provide examples of the principal types of preparative methods that can be used. 

Hydride complexes, particularly those of the early transition metals, are often prepared from main group hydrides (Equations 3.115, 3.116, 3.117, 3.118, and 3.119 0-Borohydride and aluminohydride complexes are known and have been observed as intermediates in a few reactions that form transition metal hydrides. 

In contrast to alcohols with their nch chemical reactivity ethers (compounds contain mg a C—O—C unit) undergo relatively few chemical reactions As you saw when we discussed Grignard reagents m Chapter 14 and lithium aluminum hydride reduc tions m Chapter 15 this lack of reactivity of ethers makes them valuable as solvents m a number of synthetically important transformations In the present chapter you will learn of the conditions m which an ether linkage acts as a functional group as well as the methods by which ethers are prepared... 

Reduction of amides (Section 22 9) Lithi um aluminum hydride reduces the car bonyl group of an amide to a methylene group Primary secondary or tertiary amines may be prepared by proper choice of the starting amide R and R may be ei ther alkyl or aryl... 

Ethynodiol diacetate (53) is prepared by reduction of the 3-oxo group of norethindrone (28) with lithium tributoxyalurninum hydride, followed by acylation with acetic anhydride-pyridine (78,79). It has been reported that higher yields can be obtained in the reduction step by using triethylanainoalurninum hydride (80). 

Potassium 3-aniinopropylaniide [56038-00-7] (KAPA), KNHCH2CH2CH2-NH2, pX = 35, can be prepared by the reaction of 1,3-diaminopropane and potassium metal or potassium hydride [7693-26-7] (57—59). KAPA powder has been known to explode during storage under nitrogen in a drybox, and is therefore made in situ. KAPA is extremely effective in converting an internal acetylene or aHene group to a terminal acetylene (60) (see Acetylene-DERIVED chemicals). 

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