Tantalum and niobium compounds having the general formula (I) and their use for the chemical vapour deposition process are described: wherein M stands for Nb or Ta, R1 and R2 mutually independently denote optionally substituted C1 to C12 alkyl, C5 to C12 cycloalkyl, C6 to C10 aryl radicals, 1-alkenyl, 2-alkenyl, 3-alkenyl, triorganosilyl radicals —SiR3, or amino radicals NR2 where R═C1 to C4 alkyl, R3 denotes an optionally substituted C1 to C8 alkyl, C5 to C10 cycloalkyl, C6 to C14 aryl radical, or SiR3 or NR2, R4 denotes halogen from the group comprising Cl, Br, I, or NH—R5 where R5═optionally substituted C1 to C8 alkyl, C5 to C10 cycloalkyl or C6 to C10 aryl radical, or O—R6 where R6=optionally substituted C1 to C11 alkyl, C5 to C10 cycloalkyl, C6 to C10 aryl radical, or —SiR3, or BH4, or an optionally substituted allyl radical, or an indenyl radical, or an optionally substituted benzyl radical, or an optionally substituted cyclopentadienyl radical, or —NR—NR′R″ (hydrazido(−1), wherein R, R′ and R″ have the aforementioned meaning of R, or CH2SiMe3, pseudohalide (e.g. —N3), or silylamide —N(SiMe3)2, R7 and R8 mutually independently denote H, optionally substituted C1 to C12 alkyl, C5 to C12 cycloalkyl or C6 to C10 aryl radicals.