TRANSITION-METAL STABILIZED AS(I) AND SB(I) CHELATES

The dimetallaarsacumuleniumion [Cp'(CO)2Mn = As = Mn(CO)2Cp']+, 2, (Cp' = eta-5-C5H5CH3) obtained from the arsinidene compound Cp'(CO)2Mn-As(Cl)-Mn(CO)2Cp', 1a, reacts with dipy to give the cationic arsenic(I) chelate compound [Cp'(CO)2Mn]2As[dipy]+, which has been isolated and structurally characterized as its CF3SO3 - salt, 3a. ortho-Phenanthroline as the chelate ligand gives the corresponding omicron-phen chelate, isolated as its triflate 3b. In contrast to the arsinidene compound Cp'(CO)2Mn-As(Cl)-Mn(CO)2Cp', 1a, which has first to be transformed into the cumulenic system [Cp'(CO)2Mn = As = Mn(CO)2Cp']+, 2, in order to synthesize 3a, 3b, the ''inidene'' compounds (CO)5Cr-As(Cl)-Cr(CO)5, 1b, and Cp'(CO)2Mn-Sb(Cl)-Mn(CO)2 Cp', 1c, undergo a spontaneous reaction with dipy to form the salts [L(n)M]2Xdipy+[L(n)M]2XCl2- (L(n)M = (CO)5Cr, X = As: 3c; L(n)M = Cp'(CO)2Mn, X = Sb: 3d). X-ray analyses of 3c, 3d reveal the tetrahedral coordination around the main group centers X(I) in the cationic as well as in the anionic constituents of 3a (X = As) and 3d (X = Sb). Comparison of the structures known for chelate compounds of the type [L(n)M]2dipy+ (X = As, Sb, Bi) shows a systematic trend in the relative importance of X-N- vs. X-M-bonding for these species.