The 1,3-Sn2O2-Heterocycle as a Ligand in Organometallic Compounds – Dimerization of the Inidene Species [{(CO)5M}2SnOR]– (M = Cr, W)

Abstract

Dimerized inidene complexes [(CO)5M−Sn(OR)−M(CO)5]22– (M = Cr, W; R = Et, iPr), 1, are obtained from [{(CO)5M}2SnCl2]2– by different routes. Dimerization occurs via alkoxy‐donor tin‐acceptor bonding by which a planar Sn2O2 ring is formed. The Sn–{M(CO)5} bonds are made in a plane vertical to this ring such that, with the R–O groups being almost coplanar with the Sn2O2 ring, the overall geometry of the compounds shows idealized D2h symmetry. – The 119Sn‐NMR resonances of 1 are found at rather low fields (M = Cr: δ ≈ 1400; M = W: δ ≈ 1170) indicating a low‐lying tin‐centered orbital in the LUMO range. Correspondingly EHT analyses show that the 3‐center‐4π system, which characterizes monomeric inidene species [LnM−E(X)−MLn]n, is still prevalent in the dimeric species 1. The low‐lying π*‐type LUMOs of 1 are the rationale for the observed 119Sn‐NMR low‐field shifts of 1. The dimeric compounds 1 react with 2,4‐pentanedione to form chelate compounds of the same type as those characteristically obtained from monomeric inidene complexes: [{(CO)5Cr}2SnOEt]22– (1a) reacts to give [{(CO)5Cr}2Sn(acac)]– (2). The experimental results are verified by X‐ray analyses in addition to the usual spectroscopic and analytical investigations.

Efficient Syntheses of the Complete Set of Compounds [{(OC)5M}6E6]2− (M = Cr, Mo, W; E = Ge, Sn) − Structure and Redox Behaviour of the Octahedral Clusters [Ge6]2− and [Sn6]2−

“…The reaction is sensitive to the molar ratio of the reactants: When Na 2 [Cr 2 (CO) 10 ] and SnCl 2 are used in a 3:1 ratio, the star-type compound [Sn{Cr(CO) 5 } 3 ] 2Ϫ is the main product. [21] With Na 2 [Mo 2 (CO) 10 ] or Na 2 [W 2 (CO) 10 ] used in the same molar ratio, mixtures of products are obtained which do not contain any 5 or 6, as judged from their IR absorptions. When a ratio of 1:1 is used, the isolated yield of 4 (as its Ph 4 P salt) is approximately 10%, along with other products in the reaction mixture.…”

“…The high-energy absorptions above 350 nm are characteristic of M(CO) 5 derivatives as a whole (see for instance ref. [21] ); the lower energy absorptions at approximately 400 nm are interpreted as LMCT absorptions. In agreement with germanium having a higher electronegativity than tin, these CT bands occur at higher energy for the germanium compounds than for the tin analogues (Table 5).…”