Structure and Bonding Analysis of Dimethylgallyl Complexes of Iron, Ruthenium, and Osmium [(η⁵-C₅H₅)(CO)₂M(GaMe₂)] and [(η⁵-C₅H₅)(Me₃P)₂M(GaMe₂)]

Density functional theory calculations have been performed for the dimethylgallyl complexes of iron, ruthenium, and osmium [(η5-C5H5)(L)2M(GaMe2] (M = Fe, Ru, Os; L = CO, PMe3) at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of the iron complex [(η5-C5H5)(CO)2Fe(GaMe2)] is in excellent agreement with structurally characterized complex [(η5-C5H5)(CO)2Fe(GatBu2)]. The Pauling bond order of the optimized structures shows that the M–Ga bonds in these complexes are nearly M–Ga single bond. Upon going from M = Fe to M = Os, the calculated M–Ga bond distance increases, while on substitution of the CO ligand by PMe3, the calculated M–Ga bond distances decrease. The π-bonding component of the total orbital contribution is significantly smaller than that of σ-bonding. Thus, in these complexes the GaX2 ligand behaves predominantly as a σ-donor. The contributions of the electrostatic interaction terms ΔEelstat are significantly smaller in all gallyl complexes than the covalent bonding ΔEorb term. The absolute values of the ΔEPauli, ΔEint, and ΔEelstat contributions to the M–Ga bonds increases in both sets of complexes via the order Fe < Ru < Os. The Ga–C(CO) and Ga–P bond distances are smaller than the sum of van der Waal radii and, thus, suggest the presence of weak intermolecular Ga---C(CO) and Ga---P interactions

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

¹¹⁹Sn Mössbauer isomer shift (IS) and quadrupole splitting (Δ<i>E_Q</i>) for MSnR bonding in metal–stannylidyne complexes <i>trans</i>-[Cl­(PMe₃)₄MoSn–R] (<b>1</b>), <i>trans</i>-[Cl­(PMe₃)₄WSn–R] (<b>2</b>), <i>trans</i>-[Cl­(dppe)₂MoSn–R] (<b>3</b>), <i>trans</i>-[Cl­(dppe)₂WSn–R] (<b>4</b>), [(dppe)₂MoSn–R]⁺ (<b>5</b>), [(dppe)₂WSn–R]⁺ (<b>6</b>) (R = C₆H₃–2,6-Mes₂) have been investigated for the first time. Calculations of optimized structures and ¹¹⁹Sn 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 (<b>1</b>–<b>6</b>) 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 (<b>1</b>–<b>6</b>) are almost same to the experimental values (within ±0.1 mm/s). Experimental values (IS_exptl, 2.38–2.50 mm/s) and calculated values (IS_calcd, 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 IS_exptl, as a function of Sn s electrons (<i>N</i>_s(Sn)), also exhibit a linear trend. (IS = 0.477<i>N</i>_s(Sn) – 1.888, <i>R</i>² = 0.9973). Calculated values of isomer shift (IS_calcd) using the linear regression with the <i>N</i>_s(Sn) electron density are in excellent concord with the IS_exptl.The calculated values of nuclear quadrupole splitting parameters (Δ<i>E</i>_{<i>Q</i>(calcd)}) of ¹¹⁹Sn using the relation Δ<i>E</i>_{<i>Q</i>(calcd)} = (0.540 + 0.28) V are in agreement with the experimental values

Bis(borylene) Complexes of Cobalt, Rhodium, and Iridium [(η⁵-C₅H₅)M(BNX₂)₂] (X = Me, SiH₃, SiMe₃): A Bonding Analysis

Geometry, electronic structure, and bonding analysis of the terminal neutral bis­(borylene) complexes of cobalt, rhodium, and iridium [(η⁵-C₅H₅)­M­(BNX₂)₂] (M = Co, Rh, Ir; X = Me, SiH₃, SiMe₃) were investigated at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of iridium complex [(η⁵-C₅H₅)­Ir­{BN­(SiMe₃)₂}₂] is in excellent agreement with structurally characterized iridium complex [(η⁵-C₅Me₅)­Ir­{BN­(SiMe₃)₂}₂]. Pauling, Mayer, and Nalewajski-Mrozek bond multiplicities of the optimized structures of bis­(borylene) complexes show that the M–B bonds in these complexes are nearly MB double bonds. On substitution of the BNX₂ ligand by the more π-acidic CO ligand, the calculated M–B bond distances increase, while substitution of the BNX₂ ligand by the less π-acidic PMe₃ ligand results in a decrease of the calculated M–B bond distances. The acute B–M–B bond angle and short B–B bond distance, in particular in cobalt bis­(borylene) complexes, reveal the presence of a MB2 interaction consistent with some degree of weak B–B bonding. The π-bonding contribution is, in all complexes, smaller (28.4–32.6% of total orbital contributions) than the σ-bonding contribution. The BNX₂ ligands are relatively poor π acceptors compared with the CO ligand, but better π acceptors than the PMe₃ ligand. The contribution of M ← BNX₂ Δ<i>E</i>_σ is clearly the dominant term of the orbital interaction. The σ-donor ability of borylene ligands BNX₂ is greater in bis­(borylene) complexes [(η⁵-C₅H₅)­M­(BNX₂)₂] than in carbonyl borylene complexes [(η⁵-C₅H₅)­(CO)­M­(BNX₂)] and phosphine borylene complexes [(η⁵-C₅H₅)­(PM₃)­M­(BNX₂)₂]. The absolute value of various energy terms for the MB bond decreases upon going from X = Me to SiH₃ and SiMe₃

Nature of M–Ge Bonds in the Metallogermylene Complexes of Chromium, Molybdenum, and Tungsten [(η⁵‑C₅H₅)(CO)₃M{GeN(SiMe₃)R}] and [(η⁵‑C₅H₅)(CO)₃M{GeN(Ph)R}] (R = Ph, Mesityl (Mes)): A Theoretical Study

Geometry and bond energy analysis of M–Ge bonds in the terminal metallogermylenes of chromium, molybdenum, and tungsten [(η5-C5H5)­(CO)3M­{GeN­(SiMe3)­R}] and [(η5-C5H5)­(CO)3M­{GeN­(Ph)­R}] (R = Ph, mesityl (Mes)) were investigated by DFT methods (BP86, PBE, and PW91) and the DFT-D3_BJ level of theory. The calculated geometric parameters of the molybdenum–aminogermylene complexes are in excellent agreement with the available experimental values. The M–Ge bonds in these complexes are essentially M–Ge single bonds. The optimized Ge–N bond distances are slightly smaller than those expected for a single bond on the basis of covalent radii predictions. The bent coordination geometries at germanium (M–Ge–N bond angles in the range 115.3–118.5°) in these complexes are consistent with the presence of a divalent Ge­(II) atom, which is singly bonded to a transition metal and the nitrogen of the NRR′ groups. In all studied complexes, the π-bonding contributions to the total M–Ge bonds are significantly smaller (∼17–18%) than the corresponding σ-bonding contributions and they decrease upon going from M = Cr to M = W. The contributions of the electrostatic interaction ΔEelstat to the M–Ge bonds are larger than the covalent bonding components, ΔEorb. The DFT-D3 dispersion corrections to the BDEs between the metal fragments [(η5-C5H5)­(CO)3M]− and ligand fragments [GeN­(SiMe3)­R]+ for the PBE functional are in the range 5.9–8.4 kcal/mol, which are smaller than the corresponding DFT-D3­(BJ) dispersion corrections (8.1–9.9 kcal/mol)

Linear MEMe Versus Bent MEMe: Bonding Analysis in Heavier Metal-ylidyne Complexes [(Cp)(CO)₂MEMe] and Metallo-ylidenes [(Cp)(CO)₃M−EMe] (M = Cr, Mo, W; E = Si, Ge, Sn, Pb)

The electronic and molecular structures of the complexes [(η5-C5H5)(CO)2MEMe] and [(η5-C5H5)(CO)3M−EMe] (M = Cr, Mo, W; E = Si, Sn, Pb) are calculated at the density-functional theory (DFT) level using the exchange correlation functionals B3LYP and BP86. The theoretically predicted bond lengths and angles of the model compounds are in excellent agreement with experimental values. The calculations reveal the presence of a strong ME triple (σ + 2π) bond in [(η5-C5H5)(CO)2MEMe]. The M−E bond lengths in [(η5-C5H5)(CO)3M−EMe] are longer than those expected for a single bond. The nature of the MEMe and M−EMe interactions was analyzed with charge and energy decomposition methods. In the MEMe bond, the M−E σ-bonding orbitals are always polarized toward the silicon, tin, and lead atoms, and the polarization increases from chromium to tungsten. In contrast, in the M−EMe bond, the M−E σ-bonding orbitals are significantly polarized toward the metal atom. The hybridization at the metal atoms in the ME bonds has d character in the range 60.6−68.8%, while in the M−E bonds has large d character which is always >86% of the total atomic orbital contribution. In the complexes [(η5-C5H5)(CO)2MEMe], the contributions of the electrostatic interactions, ΔEelstat, and the covalent bonding, ΔEorb, have nearly the same values for silylidyne and germylidyne complexes, while for the stannylidyne and plumbylidyne complexes, the electrostatic interactions, ΔEelstat, are greater than the orbital interaction, ΔEorb. The covalent bonding has a high degree of π-character. The total interaction energy ΔEint in the compound [(η5-C5H5)(CO)3M−EMe] is less attractive than those in the complexes [(η5-C5H5)(CO)2MEMe]. The M−ER bonds have a slightly lower degree of covalent bonding (34.9−44.9%) than the MEMe bonds (42.1−50.2%). The drastic difference between the two classes of compounds are found for the degree of a′′ (π) bonding. The contribution of ΔEπ to the covalent term ΔEorb is much higher in the MEMe bonding (41.6−42.6%) than in the M−EMe bonding (17.1−20.4%). While the π bonding contribution in [(η5-C5H5)(CO)3M−EMe] are weaker than those in [(η5-C5H5)(CO)2MEMe], the σ-bonding contribution in the former compounds are stronger than those in the latter

Nature of M−Ga Bonds in Cationic Metal-Gallylene Complexes of Iron, Ruthenium, and Osmium, [(η⁵-C₅H₅)(L)₂M(GaX)]⁺: A Theoretical Study

Density Functional Theory calculations have been performed for the cationic half-sandwich gallylene complexes of iron, ruthenium, and osmium [(η5-C5H5)(L)2M(GaX)]+ (M = Fe, L = CO, PMe3; X = Cl, Br, I, NMe2, Mes; M = Ru, Os: L = CO, PMe3; X = I, NMe2, Mes) at the BP86/TZ2P/ZORA level of theory. Calculated geometric parameters for the model iron iodogallylene system [(η5-C5H5)(Me3P)2Fe(GaI)]+ are in excellent agreement with the recently reported experimental values for [(η5-C5Me5)(dppe)Fe(GaI)]+. The M−Ga bonds in these systems are shorter than expected for single bonds, an observation attributed not to significant M−Ga π orbital contributions, but due instead primarily to high gallium s-orbital contributions to the M−Ga bonding orbitals. Such a finding is in line with the tenets of Bent’s Rule insofar as correspondingly greater gallium p-orbital character is found in the bonds to the (more electronegative) gallylene substituent X. Consistent with this, ΔEσ is found to be overwhelmingly the dominant contribution to the orbital interaction between [(η5-C5H5)(L)2M]+ and [GaX] fragments (with ΔEπ equating to only 8.0−18.6% of the total orbital contributions); GaX ligands thus behave as predominantly σ-donor ligands. Electrostatic contributions to the overall interaction energy ΔEint are also very important, being comparable in magnitude (or in some cases even larger than) the corresponding orbital interactions

Structure and Bonding Energy Analysis of Cobalt, Rhodium, and Iridium Borylene Complexes [(η⁵-C₅H₅)(CO)M(BNX₂] (X = Me, SiH₃, SiMe₃) and [(η⁵-C₅H₅)(PMe₃)M{BN(SiH₃)₂}] (M = Co, Rh, Ir)

Geometry, electronic structure, and bonding analysis of the terminal neutral borylene complexes of cobalt, rhodium, and iridium [(η5-C5H5)(CO)M(BNMe2)] (I, M = Co, II, M = Rh, III, M = Ir), [(η5-C5H5)(CO)M{BN(SiH3)2)}] (IV, M = Co, V, M = Rh, VI, M = Ir), [(η5-C5H5)(CO)M{BN(SiMe3)2)}] (VII, M = Co, VIII, M = Rh, IX, M = Ir), and [(η5-C5H5)(PMe3)M{BN(SiH3)2}] (X, M = Co, XI, M = Rh, XII, M = Ir) were investigated at the BP86 level of theory. The calculated geometry parameters of iridium borylene complex [(η5-C5H5)(CO)Ir{BN(SiMe3)2}] are in excellent agreement with their available experimental values. Pauling bond order of the optimized structures of I−XII shows that the M−B bonds in these complexes are nearly MB double bonds, which is also supported by the performed energy decomposition analysis. The orbital interactions between the metal and boron arise mainly from M←BNX2 σ-donation. In all complexes, the π-bonding contribution is smaller (26.2−37.0% of total orbital contributions) and increases via M = Rh 2 ligands, boron dominantly behaves as a σ-donor. The calculated MBNX2 interaction energy increases in all four sets of complexes in the order Co ≤ Rh Eelstat, are significantly larger in all studied borylene complexes than the covalent bonding ΔEorb: the MBNX2 bonding in the neutral borylene complexes has a greater degree of ionic character (61.2−68.5%). The iridium complexes possess the highest orbital interactions, ΔEorb, and electrostatic interactions, ΔEelstat

Nature of M–E Bonds in Metallosilylenes, -germylenes, -stannylenes, and -plumbylenes [(η⁵-C₅H₅)(Me₃P)(H)₂M(EPh)] (M = Fe, Ru, Os; E = Si, Ge, Sn, Pb)

Geometry, electronic structure, and bond energy analysis of M–ER bonds in the terminal metallosilylenes, metallogermylenes, metallostannylenes, and metalloplumbylenes of iron, ruthenium, and osmium [(η5-C5H5)(Me3P)(H)2M(EPh)] (I, M = Fe, E = Si; II, M = Fe, E = Ge; III, M = Fe, E = Sn; VI, M = Fe, E = Pb; V, M = Ru, E = Si; VI, M = Ru, E = Ge; VII, M = Ru, E = Sn; VIII, M = Ru, E = Pb; IX, M = Os, E = Si; X, M = Os, E = Ge; XI, M = Os, E = Sn; XII, M = Os, E = Pb) were investigated at the DFT/BP86/TZ2P/ZORA level of theory. The M–E bonds in these complexes are essentially M–E single bonds. In all studied complexes, the π-bonding contribution to the total M–EPh bond is significantly smaller than that of the σ-bonding and increases upon going from M = Fe to Os. Thus, in the EPh ligands the E atom is predominantly a σ-donor. The nature of E has a significant effect on the M–P bonding to the Me3P ligand trans to EPh. The M–P bond distances decrease upon going from SiPh to PbPh. The contributions of the electrostatic interactions ΔEelstat to the M–EPh bonds are larger in all complexes I–XII than the covalent bonding ΔEorb. The M–E bond in each case has a degree of covalent character of between 36% and 48%. In contrast to the interaction between charged fragments, where the electrostatic interactions ΔEelstat are greater that the orbital interactions ΔEorb, the orbital interactions ΔEorb are larger than the electrostatic interactions ΔEelstat for interaction between neutral fragments. In the case of homolytic bond dissociation, the M–E bond in each case has a degree of covalent character of between 56% and 64%

Structure and Bonding Analysis of the Cationic Electrophilic Phosphinidene Complexes of Iron, Ruthenium, and Osmium [(η⁵‑C₅Me₅)(CO)₂M{PNⁱPr₂}]⁺, [(η⁵‑C₅H₅)(CO)₂M{PNR₂}]⁺ (R = Me, ⁱPr), and [(η⁵‑C₅H₅)(PMe₃)₂M{PNMe₂}]⁺ (M = Fe, Ru, Os)

Quantum-chemical DFT calculations for the electronic, molecular structure and M–PNR2 bonding analyses of the experimentally known cationic electrophilic phosphinidene complexes [(η5-C5Me5)­(CO)2M­{PNiPr2}]+ and of the model complexes [(η5-C5H5)­(CO)2M­{PNR2}]+ (R = iPr, Me) and [(η5-C5H5)­(PMe3)2M­{PNMe2}]+ were carried out using BP86/TZ2P/ZORA level of theory. The calculated geometrical parameters of the studied complexes are in good agreement with the reported experimental values. The short M–P bond distances and calculated Pauling bond orders (range of 1.23–1.68), suggest the presence of M–P multiple bond characters. The Hirshfeld charge analysis shows that the overall charge flows from phosphinidene ligand to metal fragment. The M–P σ-bonding orbitals are well-occupied (>1.80e). The energy decomposition analysis revealed that the contribution of the electrostatic interaction ΔEelstat is, in all studied complexes, significantly larger (55.2–62.6%) than the orbital interactions ΔEorb. The orbital interactions between metal and PNR2 in [(η5-C5H5)­(L)2M­{PNR2}]+ arise mainly from M ← PNR2 σ-donation. The π-bonding contribution (19–36%) is much smaller than the σ-bonding. The interaction energies, as well as bond dissociation energies, depend on the auxiliary ligand framework around the metal and decrease in the order (η5-C5H5) > (η5-C5Me5) and CO > PMe3. Upon substitution of R = iPr with smaller group R = Me, the M–PNR2 bond strength slightly decreases

Where Are the Hydrogen Atoms in [(η⁵-C₅H₅)(PH₃)₂W(H₂SiMe₂)]⁺? A Theoretical Study

Quantum-chemical DFT calculations of the tungsten silylene complex [Cp(PH3)2W(H2SiMe2)]+ have been carried out with the aim to elucidate the structure and bonding situation of the molecule. The W−SiMe2 interactions have been examined with an energy decomposition analysis. The geometry optimization with the constraint of Cs symmetry gives a classical dihydride structure as the lowest-lying energy minimum form. Four other structures which have up to two bridging hydrogen atoms are only <5 kcal/mol higher in energy than the classical form. The results suggest that the model complex [Cp(PH3)2W(H2SiMe2)]+ and the real complex [Cp*(dmpe)W(H)2SiMe2][B(C6F5)4], which was synthesized by Tilley, have a very fluxional W(H2SiMe2) moiety, which makes it meaningless to classify the structure as classical or nonclassical. The energy decomposition analysis indicates that, in all binding modes, W→SiMe2 π-back-donation is very weak. The silylene complex should therefore be considered as a W(d2) compound, where the formal oxidation state of the metal is +4