Group VI Hydrides

The Group VI hydrides exhibit an appreciable increase in acid strength with increasing molecular weight, the pK (p. 197) values of aqueous solutions being approximately as given in Table 35. 

H—O bonds are much stronger than the bonds in the other Group VI hydrides. As we might expect, the order of acid strengths for these hydrides is just the reverse of the order of bond strengths. 

All Group VI elements form a hydride HjX. With the notable exception of water, they are all poisonous gases with very unpleasant smells. Table 10.2 gives some of their important physical properties. 

Other II-VI compounds are deposited by the reaction of the Group VIb hydride with the Group lib vaporized metal... 

The isomerisation of the pentenyl and butenyl phosphine [PhzP-(CH2) CH=CH2 (n = 2,3) (see above and ref 43)] complexes of rhodium has been held to go through a ji-allyl hydride intermediate. Such an intermediate would be equally applicable to the reactions of the group VI metals with ap. Fig. 43b. 

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