ChemInform Abstract: New Niobium Complexes with Alkynes. Part 2. Tetranuclear Compounds with Nb‐Nb Bonds, an Unprecedented Type of Tetracarbon Ligand, and Oxygen in a Rectangular Environment.

The tetranuclear dianion of complex (V) (P1, Z=1) is also prepared by reduction of NbCl3(Ph‐C≡C‐Ph)(THF)2 with Na amalgam and isolated as the dinatrium salt (20% yield, P1, Z=2) with the Na partially coordinated to Cl and THF solvate molecules, and by the same reduction in the presence of PEt3, then isolated as the PHEt3salt (49% yield, P1, Z=1).