Orbital Analysis of Carbon-13 Chemical Shift Tensors Reveals Patterns to Distinguish Fischer and Schrock Carbenes.

Fischer and Schrock carbenes display highly deshielded carbon chemical shifts (>250 ppm), in particular Fischer carbenes (>300 ppm). Orbital analysis of the principal components of the chemical shift tensors determined by solid-state NMR spectroscopy and calculated by a 2-component DFT method shows specific patterns that act as fingerprints for each type of complex. The calculations highlight the role of the paramagnetic term in the shielding tensor especially in the two most deshielded components (σ11 and σ22 ). The paramagnetic term of σ11 is dominated by coupling σ(M=C) with π*(M=C) through the angular momentum operator perpendicular to the σ and π M=C bonds. The highly deshielded carbon of Fischer carbenes results from the particularly low-lying π*(M=C) associated with the CO ligand. A contribution of the coupling of π(M=C) with σ*(M=C) is found for Schrock and Ru-based carbenes, indicating similarities between them, despite their different electronic configurations (d0 vs. d6 ).

[1]  R. Schrock Recent advances in high oxidation state Mo and W imido alkylidene chemistry. , 2009, Chemical reviews.

[2]  R. Errington,et al.  17O NMR chemical shifts in oxometalates: from the simplest monometallic species to mixed-metal polyoxometalates , 2014 .

[3]  K. Morokuma,et al.  Unusual 31P Chemical Shielding Tensors in Terminal Phosphido Complexes Containing a Phosphorus−Metal Triple Bond , 1996 .

[4]  R. Schrock Multiple metal-carbon bonds for catalytic metathesis reactions (Nobel Lecture). , 2006, Angewandte Chemie.

[5]  Jochen Autschbach,et al.  Analyzing Pt chemical shifts calculated from relativistic density functional theory using localized orbitals: The role of Pt 5d lone pairs , 2008, Magnetic resonance in chemistry : MRC.

[6]  R. Hoffmann,et al.  Unusual metal-carbon-hydrogen angles, carbon-hydrogen bond activation, and α-hydrogen abstraction in transition-metal carbene complexes , 1980 .

[7]  K. Grela,et al.  Ruthenium-based olefin metathesis catalysts bearing N-heterocyclic carbene ligands. , 2009, Chemical reviews.

[8]  C. Casey 2005 Nobel Prize in Chemistry. Development of the Olefin Metathesis Method in Organic Synthesis , 2006 .

[9]  E. Fischer,et al.  On the Existence of a Tungsten Carbonyl Carbene Complex , 1964 .

[10]  R. Schrock Alkylidene complexes of niobium and tantalum , 1979 .

[11]  Lucas Visscher,et al.  The chemical bond between Au(I) and the noble gases. Comparative study of NgAuF and NgAu+ (Ng = Ar, Kr, Xe) by density functional and coupled cluster methods. , 2008, Journal of the American Chemical Society.

[12]  Jochen Autschbach,et al.  Scalar Relativistic Computations and Localized Orbital Analyses of Nuclear Hyperfine Coupling and Paramagnetic NMR Chemical Shifts. , 2012, Journal of chemical theory and computation.

[13]  R. Schrock High oxidation state multiple metal-carbon bonds. , 2002, Chemical reviews.

[14]  Stéphanie Halbert,et al.  Elucidating the Link between NMR Chemical Shifts and Electronic Structure in d(0) Olefin Metathesis Catalysts. , 2016, Journal of the American Chemical Society.

[15]  Justin A M Lummiss,et al.  Sterically Driven Olefin Metathesis: The Impact of Alkylidene Substitution on Catalyst Activity , 2016 .

[16]  A. Macchioni,et al.  Selectively measuring π back-donation in gold(I) complexes by NMR spectroscopy. , 2015, Chemistry.

[17]  M. Straka,et al.  Origin of the conformational modulation of the 13C NMR chemical shift of methoxy groups in aromatic natural compounds. , 2013, The journal of physical chemistry. A.

[18]  M. Straka,et al.  Mechanism of Spin-Orbit Effects on the Ligand NMR Chemical Shift in Transition-Metal Complexes: Linking NMR to EPR. , 2014, Journal of chemical theory and computation.

[19]  Gernot Frenking,et al.  Structure and Bonding of Low‐Valent (Fischer‐Type) and High‐Valent (Schrock‐Type) Transition Metal Carbene Complexes , 1998 .

[20]  M. Kaupp,et al.  “Unexpected” 29Si NMR Chemical Shifts in Heteroatom-Substituted Silyllithium Compounds: A Quantum-Chemical Analysis , 2004 .

[21]  Shaohui Zheng,et al.  Solid-state chlorine NMR of group IV transition metal organometallic complexes. , 2009, Journal of the American Chemical Society.

[22]  R. Schurko,et al.  Understanding chemical shielding tensors using group theory, MO analysis, and modern density‐functional theory , 2009 .

[23]  J. Cheeseman,et al.  NMR CHEMICAL SHIFTS. 3. A COMPARISON OF ACETYLENE, ALLENE, AND THE HIGHER CUMULENES , 1999 .

[24]  C. Strohmann,et al.  Understanding Substituent Effects on 29Si Chemical Shifts and Bonding in Disilynes. A Quantum-Chemical Analysis , 2003 .

[25]  Frank Weinhold,et al.  Natural chemical shielding analysis of nuclear magnetic resonance shielding tensors from gauge-including atomic orbital calculations , 1997 .

[26]  C. Montgomery Fischer and Schrock Carbene Complexes: A Molecular Modeling Exercise , 2015 .

[27]  R. Schrock Synthesis of stereoregular polymers through ring-opening metathesis polymerization. , 2014, Accounts of chemical research.

[28]  J. Poblet,et al.  Accurate calculation of (31)P NMR chemical shifts in polyoxometalates. , 2015, Physical chemistry chemical physics : PCCP.

[29]  Christopher C. Cummins,et al.  Complexes obtained by electrophilic attack on a dinitrogen-derived terminal molybdenum nitride: electronic structure analysis by solid state CP/MAS 15N NMR in combination with DFT calculations , 2004 .

[30]  C. A. Russell,et al.  Computation provides chemical insight into the diverse hydride NMR chemical shifts of [Ru(NHC)4(L)H]0/+ species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H-, F- and Cl-) and their [Ru(R2PCH2CH2PR2)2(L)H]+ congeners. , 2017, Dalton transactions.

[31]  J. Epping,et al.  Si=X multiple bonding with four-coordinate silicon? Insights into the nature of the Si=O and Si=S double bonds in stable silanoic esters and related thioesters: a combined NMR spectroscopic and computational study. , 2010, Journal of the American Chemical Society.

[32]  R. Schrock,et al.  Dynamics of silica-supported catalysts determined by combining solid-state NMR spectroscopy and DFT calculations. , 2008, Journal of the American Chemical Society.

[33]  R. Schrock First isolable transition metal methylene complex and analogs. Characterization, mode of decomposition, and some simple reactions , 1975 .

[34]  S. Nagase,et al.  Ab Initio and DFT Study of the 29Si NMR Chemical Shifts in RSi⋮SiR , 2005 .

[35]  F. Meier,et al.  Synthesis and bonding in carbene complexes of an unsymmetrical dilithio methandiide: a combined experimental and theoretical study. , 2013, Chemistry.

[36]  Y. Ruiz-Morales,et al.  Theoretical Study of 13C and 17O NMR Shielding Tensors in Transition Metal Carbonyls Based on Density Functional Theory and Gauge-Including Atomic Orbitals , 1996 .

[37]  R. Schrock Living ring-opening metathesis polymerization catalyzed by well-characterized transition-metal alkylidene complexes , 1990 .

[38]  Karl Heinz Dötz,et al.  Fischer carbene complexes in organic synthesis: metal-assisted and metal-templated reactions. , 2009, Chemical reviews.

[39]  E. O. Fischer,et al.  Zur Frage eines Wolfram‐Carbonyl‐Carben‐Komplexes , 1964 .

[40]  R. H. Grubbs Olefinmetathesekatalysatoren zur Synthese von Molekülen und Materialien (Nobel‐Vortrag) , 2006 .

[41]  R. West,et al.  Solid-state (29)Si NMR study of RSiSiR: a tool for analyzing the nature of the Si-Si bond. , 2006, Journal of the American Chemical Society.

[42]  Jochen Autschbach,et al.  Analyzing NMR shielding tensors calculated with two-component relativistic methods using spin-free localized molecular orbitals. , 2008, The Journal of chemical physics.

[43]  G. Schreckenbach,et al.  Origin of the Hydridic 1H NMR Chemical Shift in Low-Valent Transition-Metal Hydrides , 1996 .

[44]  R. Schrock Metall‐Kohlenstoff‐Mehrfachbindungen in katalytischen Metathesereaktionen (Nobel‐Vortrag) , 2006 .

[45]  H. Fujii,et al.  Solid-state 17O NMR and computational studies of terminal transition metal oxo compounds , 2012 .

[46]  R. Grubbs,et al.  Ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts. , 2010, Chemical reviews.

[47]  T. Farrar,et al.  Natural Bond Orbital Analysis of Carbon-13 Chemical Shieldings in Acetylenes , 1996 .

[48]  R. Grubbs Olefin-metathesis catalysts for the preparation of molecules and materials (Nobel Lecture). , 2006, Angewandte Chemie.

[49]  R. Schrock,et al.  Endo-selective enyne ring-closing metathesis promoted by stereogenic-at-Mo monoalkoxide and monoaryloxide complexes. Efficient synthesis of cyclic dienes not accessible through reactions with Ru carbenes. , 2009, Journal of the American Chemical Society.

[50]  M. Straka,et al.  Interpretation of substituent effects on 13C and 15N NMR chemical shifts in 6-substituted purines. , 2011, Physical chemistry chemical physics : PCCP.

[51]  R. Schrock,et al.  Synthesis of High Oxidation State Molybdenum Imido Heteroatom-Substituted Alkylidene Complexes. , 2013, Organometallics.