NMR hydride

The most remarkable pentammine is the hydride [Rh(NH3)5H]2+ [91], produced by zinc (powder) reduction of the chloropentammine salt. It shows u(Rh-H) at 2079 cm-1 in the IR spectrum (of the sulphate) and the low-frequency hydride NMR resonance at S = -17.1 ppm as a doublet showing Rh-H coupling (14.5 Hz). Its crystal structure shows the pronounced rraus-influence of hydride, with the Rh-N bond tram to H some 0.17 A longer than the cis Rh-N bond (Figure 2.45) [92]. 

Platinum hydrides have been primarily characterized by the Pt—H stretch in the IR spectrum and the high field shift of the hydride NMR resonance. The NMR technique is particularly... 

Baba and coworkers reported the unusual reactivity of highly coordinated tin compounds such as organotin(IV) enolates or organotin(IV) hydrides. NMR studies disclose the existence of five-coordinated tin enolate arising from the addition of certain ligands . In particular, the coordination to tin enolates by a bromide anion (from Bu4NBr) shows novel types of selective reactions. ... 

Hletho qr-l,3-dloxolane and 2-etho l,3-ndl xolane Trlmethyl orthoformate, or trlethyl orthoformate, was mixed with an equimolar amount of ethylene glycol In the presence of a trace of p-toluene-sulfonlc acid. The mixture was heated to reflux for one hour, and then the corresponding alcohol Is distilled off. The crude products were purified by distillation and kept In a vacuum ampoule over calcium hydride. % NMR (CD3NO2), 5.7(s, IH), 4.0(s, 4H),... 

Figure 1. Hydride NMR spectra (100 MHz) of the reaction of acetonitrile with Fe(DMPE)2D(CeD5) (1 dissolved in CqDq) taken as a function of time...

The discussion in the proceeding sections dealt with systems at equilibrium, but just as in the earlier example involving acetonitrile, it is possible to monitor the progress of these reactions by a combination of spectroscopic techniques. An interesting example is the reaction of 1 with acetophenone. One of a series of hydride NMR spectra taken as a function of time is shown in Figure 3. The first products observed were the meta- and para-aryl hydride adducts. Later the cis-methyl adduct developed, and finally, the trans-methyl adduct (barely visible in the figure) developed as the system approached equilibrium. 

The observation of weak satellites of osmium hydride nmr signals resulting from coupling ( Os 1.62% / = 5) has been applied... 

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