Transition Metal Complexes of (Schiff Base)Divalent Group 14 Element Species [(salen)M]n=M′(CO)6n (n = 1, 2; M = Ge, Sn, Pb; M′ = Cr, W)

Abstract

The syntheses, characterization, and reactivities of the new stable mono- and cis-disubstituted Group 14 metal(II) chromium and tungsten carbonyl complexes (salen)MM′(CO)5 [salen = 2,2′-N,N′-bis(salicylidene)ethylenediamine; M′ = Cr, M = Ge (4), Sn (5), Pb (6); M′ = W, M = Ge (7), Sn (8), Pb (9)] and [(salen)M]2=M′(CO)4 [M′ = W, M = Ge (10), Sn (11), Pb (12); M′ = Cr, M = Sn (14), Ge (15)] are described. Complexes 4–9 were obtained in high yields by treatment of the M′(CO)5 · THF intermediates with the stable divalent species (salen)MII [M = Ge (1), Sn (2), Pb (3)]. Direct irradiation of mixtures of (salen)MII and M′(CO)6 resulted in formation of the monosubstituted compounds 4–9 together with the disubstituted species 10–12, 14, and 15 in ratios depending on the nature of both M and M′. Pure complexes 10–12 were obtained by two different synthetic approaches starting from the (salen)MII species or the (salen)MM′(CO)5 complexes. Each of the new complexes has been characterized by 1H- and 13C-NMR, and by 119Sn-NMR in the case of 5, 8, 11, and 14, as well as by IR spectroscopy in all cases. The molecular structures of 5, 8, 11, and 14, determined by X-ray structure analyses, reveal a pentacoordinated tin atom. The tin–chromium distances are among the shortest (in particular that in 5, 2.557 Å) observed for transition metal divalent tin complexes and the tin lies about 0.99 Å above the plane defined by the O2N2 atoms of the salen ligand. All these complexes have been found to be unreactive towards water and organic acids. Simple phosphane monosubstitution of carbonyl in 8 using Ph3P led to the new complex 13. Reactions with 1,2-bis(diphenylphosphanyl)ethane and 3,5-di-tert-butyl-1,2-benzoquinone resulted in displacement of the divalent species from the carbonyl complexes 5 and 8.