The reaction of Cr(CO) 6 with 1,2 bis[(2,6 diisopropylphenyl)imino]acenaphthene (1, dpp bian) affords a chromium complex with the neutral diimine ligand (dpp bian)Cr(CO) 4 (2). The exchange reactions of the compound [(dpp bian)Cr( Cl)(THF)] 2 (3) with LiOH, PhCCNa, [(CH 3 ) 3 Si] 2 NK, C 5 H 5 Na, and C 5 Me 5 Na give the corresponding radical anion derivatives, viz., [(dpp bian)Cr( OH)] 2 (4), [(dpp bian)Cr( CCPh)] 2 (5), (dpp bian)Cr[N(SiMe 3 ) 2 ] (THF) (6), (dpp bian)Cr(C 5 H 5 ) (7), and (dpp bian)Cr(C 5 Me 5 ) (8). The titanium and zirconi um complexes with the acenaphthene 1,2 diimine dianion, viz., (dpp bian) 2 Ti (9) and (dpp bian)Zr(Cl)Cp (10), were synthesized by the reactions of Na 2 (dpp bian) with TiCl 4 and CpZrCl 3 , respectively. All compounds were characterized by IR spectroscopy and elemental analysis. Diamagnetic derivatives 2, 9, and 10 were additionally studied by 1 H NMR spectro scopy. The structures of products 2, 4-8, and 10 were determined by X ray diffraction.Key words: diimine ligands, transition metals, molecular and electronic structures.1,2 Bis(arylimino)acenaphthenes were put in use as ligands in the coordination chemistry about 10 years ago. 1,2 Bis[(2,6 diisopropylphenyl)imino]acenaphthene (1, dpp bian) is the most commonly applied ligand of this class. Its distinguishing features are, first, the conforma tional rigidity of the diimine moiety, the nitrogen atoms of which are coordinated to the metal atom, and, second, the shielding of the coordination area by bulky substituents at the nitrogen atoms. This ensures the formation of mono meric metal complexes, in which the diimine ligand never acts as a bridging ligand. The absolutely unique property of the dpp bian ligand is its ability to be reversibly reduced by alkali metals to mono , di , tri , and tetraanions to form the salts [(dpp bian) n-M + n (Et 2 O) m ] (M = Li, Na; n = 1-4, m = 1-4). 1,2 Organometallic compounds, for example, Me 2 Mg 3 or EtMgBr, 4 can also reduce dpp bian. In the former case, the reaction is accompanied by the elimination of the methyl radical to give the oragno magnesium derivative with the dpp bian radical anion [(dpp bian)MgMe] 2 . The reaction of dpp bian with a Grignard reagent affords the addition product of the oragnomagnesium compound at one of the C=N bonds of the diimine, (dpp bian Et)MgBr(Et 2 O) 2 . Both reactions proceed through the one electron transfer to form the dpp bian radical anion, which recombines with the ethyl radi cal to give the final product.A series of compounds containing unusual metal-met al bonds, including derivatives of Group 13 metals having unique reactivity toward alkynes, of the general formula (dpp bian)M-M(dpp bian) (M = Ga, Al) were synthe sized using dpp bian as the ligand. 5-9 Like other diimines, dpp bian can stabilize low oxidation states, including di valent states of silicon and germanium. 10-12 The redox isomerization in the complex of a 4f element, viz., in the compound [(dpp bian)YbBr(DME)] 2 , 13 was accom plished for the first time using the dpp b...