Zwei Extreme in der Zinnchemie: Ein nichtbindender Sn–Sn‐Abstand von 285 pm und eine ¹¹⁹Sn‐NMR‐Verschiebung δ = 3301 in metallorganischen Derivaten von Sn(0)

Two Extremes in Tin Chemistry: A Non‐bonding Sn–Sn Distance of 285 pm and a ¹¹⁹Sn‐NMR Shift δ = 3301 in Organome‐tallic Derivatives of Sn(0)The reaction of Na[{Cp'(CO)₂Mn}₂H] with SnCl₂, which produces the inidene compound [Cp'(CO)₂Mn\documentclass{article}\usepackage{amsmath}\pagestyle{empty}$ {\rm C}\ddot - {\rm C} $ Sn(Cl)\documentclass{article}\usepackage{amsmath}\pagestyle{empty}$ {\rm C}\ddot - {\rm C} $ Mn‐(CO)₂Cp']⁻ under standard workup procedures, results in the formation of [{Cp'(CO)₂MnSn}₂{μ₂‐Mn(CO)₂Cp'}₂{μ₂‐Cl}]⁻ (1) when quenched with unpolar solvents. While, formally, 1 contains tin in its oxidation state zero, it may be conceived as composed of an Sn²⁻₂ entity, which is linearly end‐on coordinated to two Cp'(CO)₂Mn 16‐electron species; in addition the tin centers are bridged by two μ₂‐Mn(CO)₂Cp' moieties and a μ₂‐Cl function. The resulting connectivity Sn₂{μ₂‐Mn(CO)₂Cp'}₂{μ₂‐Cl} thus corresponds to a [1.1.1]propellane scaffolding. While there is no obvious need for a tin‐tin bond in this propellane‐type cage, a short Sn–Sn contact of only 285 pm is observed. While the ¹¹⁹Sn‐NMR signal of 1 could not be recorded, the peculiar bonding in this type of compounds is generally mirrored in their unconventional ¹¹⁹Sn‐NMR shift whereever signals can be observed: it is found that [{Cp*(CO)₂Mn}₃(μ₃‐Sn)], which contains trigonally planar‐coordinated μ₃‐Sn as a naked ligand atom, has its ¹¹⁹Sn‐NMR resonance at δ = 3301 well beyond the known range of ¹¹⁹Sn‐NMR shifts. This finding is interpreted in terms of a relatively week Sn_pπ‐Mn_dπ π bonding which leads to low‐energy unoccupied molecular orbitals as the prerequisit for a large paramagnetic contribution to the NMR shift.