Anionic trimetallic compounds containing FeEM skeletons (E = Zn, Cd, Hg; M = Fe, Mo, W). Crystal structure of [N(PPh 3) 2] 2[(OC) 4FeHgFe(CO) 4

Abstract

Dichlorides of group 12 elements react with (NEt 4)[HFe(CO) 4] in tetrahydrofuran to give the di-hydrides [(OC) 4HFeEFeH(CO) 4] (E = Zn, Cd, Hg) in good yields. These compounds undergo proton abstraction by nBuLi to give di-anions [(OC) 4FeEFe(CO) 4] 2-, stabilized as their bis(triphenylphosphine)nitrogen(+) (PPN +) salts. (PPN) 2[(OC) 4FeHgFe(CO) 4] crystallizes in the triclinic system, space group P 1 with a 20.382(3), b 15.328(2), and c 13.420(2) Å; α 115.96(3), β 108.89(2), and γ 87.09(2) o, and Z = 2. The anion consists of an almost linear spine (FeHgFe angle 178.7(1) o), with an average FeHg bond distance of 2.546(2) Å. The Fe atoms display a trigonal bipyramidal geometry, and the equatorial CO groups linked to the iron atoms are in an eclipsed conformation, resulting in an idealized D 3 h symmetry. The existence of two conformers for this anion and the presence of Hg · · · CO backbonding are discussed on the basis of qualitative molecular orbital theory. The [(OC) 4FeHgFe(CO) 4] 2- anion undergoes redistribution reactions with [M(CO) 3(η-C 5H 5)] 2 Hg (M = Mo, W) to give the new unsymmetrical anions [(OC) 4FeHgM(CO) 3(η-C 5H 5)] -.