A series of mono, di-, tri- and tetranuclear nitrosyl and oxo molybdenum co
mplexes containing the tris(3,5-dimethylpyrazolyl)borato ligand exhibit a r
ange of redox processes which are controlled mainly by the ligands and by t
he extent of oligonucleation. Homo- and hetero-dinuclear complexes have a r
ange of properties dependent on this redox behaviour, and linear (electroch
romism in the near infrared) and non-linear (second harmonic generation) pr
operties are described.