There are described novel compounds of the formula I defined herein ##STR1## wherein R is a phenyl group which is unsubstituted or mono- to tetra-substituted by C.sub.1 -C.sub.4 -alkyl, halogen, nitro, cyano, trifluoromethyl, phenyl or C.sub.1 -C.sub.3 -alkoxy, or it is 3,4-methylenedioxy-phenyl, including the acid addition salts thereof with organic and inorganic acids as well as metal complexes thereof, all having tolerance to cultivated plants and possessing valuable microbicidal properties. They can be used for combating phytopathogenic microorganisms, particularly phytopathogenic fungi. The compounds of the formula I have for practical purposes a very favorable curative, systemic and preventive action for the protection of cultivated plants, without these being impaired as a result of undesirable side-effects. They can be used in practice on their own or in the form of microbicidal compositions.