Dispersion-Corrected Relativistic Density Functional Theory (DFT) Calculations of Structure and ¹¹⁹Sn Mössbauer Parameters for M≡SnR Bonding in Filippou’s Stannylidyne Complexes of Molybdenum and Tungsten

Abstract

(119)Sn Mössbauer isomer shift (IS) and quadrupole splitting (ΔEQ) for M≡SnR bonding in metal-stannylidyne complexes trans-[Cl(PMe3)4Mo≡Sn-R] (1), trans-[Cl(PMe3)4W≡Sn-R] (2), trans-[Cl(dppe)2Mo≡Sn-R] (3), trans-[Cl(dppe)2W≡Sn-R] (4), [(dppe)2Mo≡Sn-R](+) (5), [(dppe)2W≡Sn-R](+) (6) (R = C6H3-2,6-Mes2) have been investigated for the first time. Calculations of optimized structures and (119)Sn Mössbauer parameters were carried out at the DFT/TPSS-D3(BJ)/TZVPP/ZORA level of theory. The calculated geometry parameters of stannylidyne complexes of molybdenum and tungsten (1-6) are in good agreement with experimental values of W-Sn and Sn-C bond distances. The calculated values of the isomer shift for the complexes (1-6) are almost same to the experimental values (within ±0.1 mm/s). Experimental values (ISexptl, 2.38-2.50 mm/s) and calculated values (IScalcd, 2.37-2.49 mm/s) of isomer shifts indicate that the oxidation state of tin in the studied complexes with M≡Sn-R bonding is Sn(II). The variations of ISexptl, as a function of Sn s electrons (Ns(Sn)), also exhibit a linear trend. (IS = 0.477Ns(Sn) - 1.888, R(2) = 0.9973). Calculated values of isomer shift (IScalcd) using the linear regression with the Ns(Sn) electron density are in excellent concord with the ISexptl.The calculated values of nuclear quadrupole splitting parameters (ΔEQ(calcd)) of (119)Sn using the relation ΔEQ(calcd) = (0.540 + 0.28) V are in agreement with the experimental values.

Metal–Silicon Triple Bonds: Access to [Si(η5-C5Me5)]+ from SiX2(NHC) and its Conversion to the Silylidyne Complex [TpMe(CO)2MoSi(η3-C5Me5)] (TpMe = κ3-N,N′,N″-hydridotris(3,5-dimethyl-1-pyrazolyl)borate)

“…We envisaged to develop a new synthetic approach to silylidyne complexes using silyliumylidenes based on the following conception. Quantum chemical bonding analyses of the presently known heavier tetrylidyne complexes [L n ME–R] (E = Si–Pb, R = organyl group) revealed that the M–E bonds between the negatively charged metal M and the positively charged tetrel atom E are quite polar and composed of a σ bond, polarized toward the tetrel atom E, and two π bonds, which are polarized toward the metal center M . The ME–R bonding can thus be reasonably well described in terms of the Dewar–Chatt–Duncanson model to comprise a σ-donation from the tetryliumylidene [ER] + ligand to the anionic transition-metal fragment [L n M] − and two [L n M] − → [ER] + π-backdonations, similar to the MC bonding in Fischer-type carbyne complexes .…”