Nucleophilic Functionalization of a Cationic Pentaphosphole Complex-A Systematic Study of Reactivity.

The systematic nucleophilic functionalization of the cationic pentaphosphole ligand complex [Cp*Fe(η-PMe)][OTf] (A) with group 16/17 nucleophiles is reported. This method represents a highly reliable and versatile strategy for the design of novel transition-metal complexes featuring twofold substituted end-deck cyclo-P ligands, bearing unprecedented hetero-element substituents. By the reaction of A with classical group 16 nucleophiles, complexes of the type [Cp*Fe(η-PMeE)] (E=OEt (1), OBu (2), SPh (3), SePh (4)) are obtained.

The Influence of the Solvation on the Bonding of Molecular Complexes of Diatomic Halogens With Nitrogen-Containing Donors and Their Stability With Respect to the Heterolytic Halogen-Halogen Bond Splitting.

In the framework of SMD approach a systematic computational study of structural, electronic and thermodynamic properties of molecular complexes of Cl, ICl and I with series of N-containing Lewis bases in solvents of different polarity was carried out. Results indicate that molecular complexes of Cl with strong and medium-strong LB undergo spontaneous ionization in the acetonitrile solution. The increase of the solvent polarity can change the nature of interaction in X'XLB systems from molecular X'X ← LB donor-acceptor complexes to 3-center 4-electron bound X'→X ← LB in solvents of medium polarity and to the contact ion pairs X'→[XLB] in polar solvents.

Facile heterolytic bond splitting of molecular chlorine upon reactions with Lewis bases: Comparison with ICl and I.

Formation of molecular complexes and subsequent heterolytic halogen-halogen bond splitting upon reactions of molecular Cl with nitrogen-containing Lewis bases (LB) are computationally studied at M06-2X/def2-TZVPD and for selected compounds at CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz levels of theory. Obtained results are compared with data for ICl and I molecules. Reaction pathways indicate, that in case of Cl∙LB complexes the activation energies for the heterolytic Cl-Cl bond splitting are lower than the activation energies of the homolytic splitting of Cl molecule into chlorine radicals.

Synthesis of bismuthanyl-substituted monomeric triel hydrides.

The syntheses and characterizations of the first bismuthanylborane monomers stabilized only by a donor in D·BHBi(SiMe) (D = DMAP 1a, IDipp 1b, IMe1c; DMAP = 4-dimethylaminopyridine, IDipp = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene, IMe = 1,3,4,5-tetramethylimidazol-2-ylidene) are presented. All compounds were synthesized by salt metathesis reactions between D·BHI and KBi(SiMe)(THF) and represent some of the extremely rare compounds featuring a 2c-2e B-Bi bond in a molecular compound. The products display high sensitivity towards air and light and slowly decompose in solution even at -80 °C.

Structures and stability of I and ICl complexes with pyridine: Ab initio and DFT study.

Theoretical investigation of thermodynamic stability and bonding features of possible isomers of the molecular and ionic complexes of pyridine with molecular iodine and iodine monochloride IX (X = I,Cl) is presented. M06-2X DFT functional is found to provide bond distances and dissociation energies which are close to those obtained at high-level ab initio CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz benchmark computations for the most stable isomers, formed via donation of a lone pair of nitrogen atom of pyridine to the iodine atom. These isomers are by 23-33 kJ mol (in case of I) and by 39-56 kJ mol (in case of ICl) more stable than other molecular complexes.

NHC-Stabilized Mixed Group 13/14/15 Element Hydrides.

The syntheses of novel N-heterocyclic carbene (NHC) adducts of group 13, 14 and 15 element hydrides are reported. Salt metathesis reactions between NaPH and IDipp ⋅ GeH BH OTf (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) led to mixtures of the two isomers IDipp ⋅ GeH BH PH (2 a) and IDipp ⋅ BH GeH PH (2 b); by altering the reaction conditions an almost exclusive formation of 2 b was achieved. Attempts to purify mixtures of 2 a and 2 b by re-crystallization from THF afforded a salt [IDipp ⋅ GeH BH  ⋅ IDipp][PHGeH BH PH BH GeH ] (4) that contains the novel anionic cyclohexyl-like inorganic heterocycle [PHGeH BH PH BH GeH ] .

Reactivity of [Cp*Fe(η -As )] towards Carbenes, Silylenes and Germylenes.

The reaction behavior of [Cp*Fe(η -As )] (I) (Cp*=C Me ) towards carbenes and their heavier analogs was investigated. The reaction of I with NHCs (NHCs=N-heterocyclic carbenes) results in the first substitution products of polyarsenic ligand complexes by NHCs [Cp*Fe(η -As NHC)] (1 a: NHC=IMe=1,3,4,5-tetramethylimidazolin-2-ylidene, 1 b: NHC=IMes=1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene). In contrast, the reaction of I with CAAC ( CAAC=2,6-diisopropylphenyl)-4,4-diethyl-2,2-dimethyl-pyrrolidin-5-ylidene) leads to a fragmentation and the formation of an unprecedented As -sawhorse-type compound [As (As CAAC) ] (2).

The Field of Main Group Lewis Acids and Lewis Superacids: Important Basics and Recent Developments.

New developments in the field of Lewis acidity are highlighted, with the focus of novel Lewis acids and Lewis superacids of group 2, 13, 14, and 15 elements. Several important basics, illustrated by modern examples (classification of Donor-Acceptor (DA) complexes, amphoteric nature of any compound in terms of DA interactions, reorganization energies of main group Lewis acids and the role of the energies of frontier orbitals) are presented and discussed. It is emphasized that the Lewis acidity phenomena are general and play vital role in different areas of chemistry: from weak "atomophilic" interactions to the complexes of Lewis superacids.

Structures and Stability of Mixed Main Group Hydrides [PBEH] (E = C, Si, Ge; = 1-4) and Donor-Acceptor Stabilization of Monomeric Chain Isomers.

Structures and stability of mixed group 13-14-15 element hydrides PBEH (E = C, Si, Ge), their oligomers, and complexes with Lewis acids and Lewis base are computationally studied at the B3LYP-D3/def2-TZVP level of theory. Unsubstituted chain hydrides are unstable and are expected to form cyclic oligomers. Cyclization can be prevented by the donor-acceptor complex formation.

Reactivity of Yellow Arsenic towards Cyclic (Alkyl)(Amino) Carbenes (CAACs).

Different cyclic (alkyl)(amino)carbenes (CAACs) were reacted with yellow arsenic. Several products [(CAAC-n) (μ,η -As )] (n=1 (1), 4 (2)), [(CAAC-2) (μ ,η -As )] (3) and [(CAAC-3) (μ ,η - As )] (6) were isolated due to the differing steric properties of CAAC-1-4. The products contain As , As or As units and represent the first examples of CAACs-substituted products of yellow arsenic.

A convenient route to mixed cationic group 13/14/15 compounds.

The formation of novel cationic mixed main group compounds is reported revealing a chain composed of different elements of group 13, 14, and 15. Reactions of different pnictogenylboranes REBH·NMe (E = P, R = Ph, H; E = As, R = Ph, H) with the NHC-stabilized compound IDipp·GeHBHOTf (1) (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene) were carried out, yielding the novel cationic, mixed group 13/14/15 compounds [IDipp·GeHBHERBH·NMe] (2a E = P; R = Ph; 2b E = As; R = Ph; 3a E = P; R = H; 3b E = As; R = H) by the nucleophilic substitution of the triflate (OTf) group. The products were analysed by NMR spectroscopy and mass spectrometry and for 2a and 2b also by X-ray structure analysis.

Hydrogen Activation by Frustrated and Not So Frustrated Lewis Pairs Based on Pyramidal Lewis Acid 9-Boratriptycene: A Computational Study.

Structural features and reactivity of frustrated Lewis pairs (FLPs) formed by pyramidal group 13 Lewis acids based on 9-bora and 9-alatriptycene and bulky phosphines P Bu, PPh, and PCy are considered at the M06-2X/def2-TZVP level of theory. Classic FLP is formed only in the B(CMe)CH/P Bu system, while both FLP and donor-acceptor (DA) complex are observed in the B(CF)CF/P Bu system. Formation of DA complexes was observed in other systems; the B(CH)CH·P Bu complex features an elongated DA bond and can be considered a "latent" FLP.

Three- and Five-Membered Anionic Chains of Pnictogenylboranes.

An unprecedented family of three- and five-membered substituted anionic derivatives of parent pnictogenylboranes is herein reported. Reacting various combinations of the pnictogenylboranes H E'-BH -NMe (E'=P, As) with pnictogen-based nucleophiles MER1R2 (E=P, As; R1=H, R2= Bu; R1=R2=Ph; M=Na, K) allows for the isolation of the unsymmetrical products [Na(18-crown-6)][H E'-BH -EH Bu] (3: E=E'=P; 4: E=E'=As; 5: E=As, E'=P) and [M(C)][H E'-BH -EPh ] (7: E=E'=P, M=Na, C=18-crown-6; 8: E=E'=As; M=K, C=[2.2.

Coordination of Pnictogenylboranes Towards Tl(I) Salts and a Tl- Mediated P-P Coupling.

The coordination chemistry of only Lewis-base (LB)-stabilized pnictogenylboranes EH BH ⋅NMe (E=P, As) towards Tl(I) salts has been studied. The reaction of Tl[BAr ] (BAr =[B(3,5-C H Cl ) ] ) with the corresponding pnictogenylborane results in the formation of [Tl(EH BH ⋅NMe )][BAr ] (1 a: E=P; 1 b: E=As). Whereas the Tl ion in 1 a/b is monocoordinated, the exchange of the weakly coordinating anion (WCA) in the Tl(I) salt leads to the formation of a trigonal pyramidal coordination mode at the Tl atom by coordination of three equivalents of EH BH  ⋅ NMe in [Tl(EH BH  ⋅ NMe ) ][WCA] (2 a: E=P, WCA=TEF ; 2 b: E=As, WCA=TEF) (TEF=[Al{OC(CF ) } ] , TEF =[Al{(OC(CF ) (CCl )} ] ).

Lewis acid stabilized group 13-15 element analogs of ethylene.

Stabilization of hydrogen-substituted group 13-15 compounds H EE'H (E = B, Al, Ga; E' = P, As, Sb) by Lewis acids is considered at B3LYP/def2-TZVP, B3LYP-D3/def2-TZVP and M06-2X/def2-TZVP levels of theory. It is shown, that for many Lewis acids additional reactivity beyond the DA complex formation with H EE'H monomer is expected. In case of complexation with E(C F ) , F/H exchange reactions with group 13 bound hydrides are predicted to be exothermic and accompanied by the activation energies which are smaller than dissociation of the complex into components.

An NHC-Stabilized H GeBH Precursor for the Preparation of Cationic Group 13/14/15 Hydride Chains.

The synthesis, characterization and reactivity studies of the NHC-stabilized complex IDipp ⋅ GeH BH OTf (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) are reported. Nucleophilic substitution of the triflate (OTf) group in 1 by phosphine or arsine donors provides access to the cationic group 13/14/15 chains [IDipp ⋅ GeH BH ERR R ] (2 E=P; R, R =H; R = Bu; 3 E=P; R=H; R , R =Ph; 4 a E=P; R, R , R =Ph; 4 b E=As; R, R , R =Ph). These novel cationic chains were characterized by X-ray crystallography, NMR spectroscopy and mass spectrometry.

Unusual molecular complexes of antimony fluoride dimers with acetonitrile and pyridine: structures and bonding.

The structures of two new molecular complexes of antimony pentafluoride with pyridine (Py) and acetonitrile (AN), SbF·Py and SbF·AN, and a molecular complex of antimony trifluoride SbF·Py and its ionic derivative [HPy][SbF] in the solid state have been determined by single crystal X-ray structural analysis. The complexes SbF·AN and SbF·Py are the first structurally characterized compounds of dimeric antimony fluorides. To reveal the nature of bonding in the complexes and their stability, DFT computations of the electronic structure and thermodynamic characteristics were performed, in particular the analysis of the electrostatic potentials, the orbital interactions and the topology.

Reactivity of the pentelidene complexes [Cp*E{W(CO)}] (E = P, As) towards dichalcogenides and chalcogenols - synthesis of novel chalcogenopentelidene complexes.

Pentelidene complexes of the type [Cp*E{W(CO)}] (Cp* = CMe; 1a: E = P, 1b: E = As) were reacted with the dichalcogenides RCh (R = Ph, Mes, Tipp; Ch = S, Se, Te; Mes = 2,4,6-trimethylphenyl; Tipp = 2,4,6-triisopropylphenyl) and the chalcogenols PhChH (Ch = S, Se). It has been shown that the formation of new E-Ch bonds proceeds under elimination of the Cp* substituent. The resulting chalcogenopentelidene complexes, which have been isolated and fully characterised, represent a novel class of phosphinidene complexes which can be synthesised through this general synthetic route.

Influence of the solvent on the Lewis acidity of antimony pentahalides and group 13 Lewis acids toward acetonitrile and pyridine.

Energetic effects of solvation of SbF , SbCl , and 21 group 13 Lewis acids (LA) and their molecular complexes with acetonitrile and pyridine are evaluated using SMD approach. Compared to the gas phase, solvation increases the stability of boron- and aluminum-containing complexes but decreases the stability of gallium and indium-containing homologs due to larger solation energies of free LA. New Lewis acidity scales, based on the Gibbs energy of dissociation of the molecular complexes LA·pyridine and LA·acetonitrile in the gas phase, in benzene and acetonitrile solutions, are proposed.

Stability and Electronic Structure of Donor-Acceptor Stabilized Group 13/15 Oligomers.

Electronic structures and thermodynamic characteristics of chain inorganic group 13-15 oligomers [HMEH] (M = B, Al, Ga, E = P, As; = 4-15) are presented. Donor-acceptor interaction with both Lewis acids and Lewis bases effectively stabilizes chain isomers with respect to spontaneous cyclization and significantly changes their electronic structure.

The carbene transfer to strong Lewis acids: copper is better than silver.

A new convenient approach to the synthesis of useful N-heterocyclic carbene complexes of group 13 metals was successfully developed. We demonstrate that air-stable copper(i) diaminocarbene complexes are excellent carbene transfer reagents for the synthesis of (IMes or IPr)MCl3 with high yields (M = Al, Ga). Use of this simple method allowed for the first time to obtain (IPr)AlCl3, inaccessible via a free carbene route.

Bulky Polyfluorinated Terphenyldiphenylboranes: Water Tolerant Lewis Acids.

Protocols for the synthesis of the bulky polyfluorinated triarylboranes 2,6-(C F ) C F B(C F ) (1), 2,6-(C F ) C F B[3,5-(CF ) C H ] (2), 2,4,6-(C F ) C H B(C F ) (3), 2,4,6-(C F ) C H B[3,5-(CF ) C H ] (4) were developed. All boranes are water tolerant and according to the Gutmann-Beckett method, 1-3 display Lewis acidities larger than that of the prominent B(C F ) .

NHC-stabilized Parent Arsanylalanes and -gallanes.

The synthesis and characterization of the unprecedented compounds IDipp⋅E'H AsH (E'=Al, Ga; IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) are reported, the first monomeric, parent representatives of an arsanylalane and arsanylgallane, respectively, stabilized only by a LB (LB=Lewis Base). They are prepared by a salt metathesis reaction of KAsH with IDipp⋅E'H Cl (E'=Al, Ga). The H -elimination pathway through the reaction of AsH with IDipp⋅E'H (E'=Al, Ga) was found to be a possible synthetic route with some disadvantages compared to the salt metathesis reaction.

NHCs as Neutral Donors towards Polyphosphorus Complexes.

The first adducts of NHCs (=N-heterocyclic carbenes) with aromatic polyphosphorus complexes are reported. The reactions of [Cp*Fe(η -P )] (1) (Cp*=pentamethyl-cyclopentadienyl) with IMe (=1,3,4,5-tetramethylimidazolin-2-ylidene), IMes (=1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene) and IDipp (=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) led to the corresponding neutral adducts which can be isolated in the solid state. However, in solution, they quickly undergo a dissociative equilibrium between the adduct and 1 including the corresponding NHC.