A high-spin organometallic Fe-S compound: structural and Mössbauer spectroscopic studies of [phenyltris((tert-butylthio)methyl)borate]Fe(Me).
The synthesis and structure of the pseudotetrahedral, sulfur-rich, high-spin organoiron(II) [phenyltris((tert-butylthio)methyl)borate]Fe(Me), [PhTt(tBu)]Fe(Me), 1, are reported. Low-temperature Mössbauer spectroscopic studies reveal an isomer shift of delta = 0.60(3) mm/s and DeltaE(Q) = 0.00(1) mm/s and an S = 2 ground multiplet with a negative zero-field splitting, D = -33(3) cm(-1), E/D approximately = 0.01. The small separation of the ground doublet, Delta approximately = 0.01 cm(-1), allows for observation of X-band EPR signals at g(eff) approximately = 10 (g(z) = 2.6, g(x,y) = 2.00). The relatively large negative zero-field splitting and a highly anisotropic magnetic hyperfine tensor, containing a large orbital z component, {-10(4), -10(4), +33.8(2) MHz}, are concordant with the presence of unquenched orbital angular momentum. Density functional theory (DFT) calculations predict that the lowest-lying orbitals have predominantly d(xy)- and d(x(2)-y(2))-like character, separated by an energy gap small enough to allow mixing through spin-orbit coupling, to generate a negative zero-field splitting, consistent with the experimental observations. The experimental and DFT-calculated isomer shifts are in good agreement (delta(calcd) = 0.5 mm/s). The unusual (for a high-spin ferrous site) null electric field gradients can be qualitatively explained in the frame of the spin-orbit coupling mixing. The very small Fermi contact component of the magnetic hyperfine tensor (A(FC)(exp) = -9 MHz) is not well described by the DFT approach (A(FC)(calcd) = +2 MHz). To our knowledge, this is the first study of a sulfur-coordinated high-spin organoiron(II) complex.
Popescu
Codrina V
CV
Department of Chemistry, Ursinus College, Collegeville, Pennsylvania 19426, USA. cpopescu@ In contrast toursinus.edu
Mock
Michael T
MT
Stoian
Sebastian A
SA
Dougherty
William G
WG
Yap
Glenn P A
GP
Riordan
Charles G
CG
D003198:Computer Simulation; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D015204:Spectroscopy, Mossbauer; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D005296:Ferrous Compounds; D013438:Sulfhydryl Compounds