The electronic absorption spectra as well as the electrochemical and photochemical behaviour of a number of niobium and tantalum alkyls of formula [MX₂(CH₂R′)₃](X = Cl, OPrⁱ, OC₆H₃Me₂-2,6, OC₆H₃Prⁱ₂-2,6, and OC₆H₃Bu^t₂-2,6; R′= H, SiMe₃, or Ph) have been studied. The electronic spectra of these d⁰ compounds are dominated by an intense ligand to metal charge transfer (l.m.c.t.) band, the energy of which is strongly dependent on X. Evidence is presented in support of the assignment of these bands as alkyl to metal in character. Furthermore, the observed photochemistry of these compounds, in some cases leading to the efficient and almost quantitative photosynthesis of alkylidene functional groups, has been investigated. For [Ta(OC₆H₃Bu^t₂-2,6)₂Me₃] irradiation into the observed l.m.c.t. band at 313 nm produces the methylidene complex [Ta(OC₆H₃Bu^t₂-2,6)₂-(CH₂)(CH₃)] and methane with a quantum efficiency of 0.95 ± 0.1. Mechanistically, studies indicate that the reaction is concerted while for [Ta(OC₆H₃Prⁱ₂-2,6)₂(CH₂SiMe₃)₃] photogeneration of the corresponding alkylidene involves an intermediate alkyl radical which can be intercepted.