Synthesis,Structure, and Fluxionality of Strained Hypercoordinate Silicon‐Bridged [1]Ferrocenophanes

The first hypercoordinate sila[1]ferrocenophanes [fcSiMe(2‐C₆H₄CH₂NMe₂)] ( 5 a ) and [fcSi(CH₂Cl)(2‐C₆H₄CH₂NMe₂)] ( 5 b ) (fc=(η⁵‐C₅H₄)Fe(η⁵‐C₅H₄)) were synthesized by low‐temperature (?78 °C) reactions of Li[2‐C₆H₄CH₂NMe₂] with the appropriate chlorinated sila[1]ferrocenophanes ([fcSiMeCl] ( 1 a ) and [fcSi(CH₂Cl)Cl] ( 1 d ), respectively). Single‐crystal Xray diffraction studies revealed pseudo‐trigonal bipyramidal structures for both 5 a and 5 b , with one of the shortest reported Si???N distances for an sp³‐hybridized nitrogen atom interacting with a tetraorganosilane detected for 5 a (2.776(2) Å). Elongated Si? C_ipso bonds trans to the donating NMe₂ arms (1.919(2) and 1.909(2) Å for 5 a and 5 b , respectively) were observed relative to both the non‐trans bonds ( 5 a : 1.891(2); 5 b : 1.879(2) Å) and the Si? C_ipso bonds of the non‐hypercoordinate analogues ([fcSiMePh] ( 1 b ): 1.879(4), 1.880(4) Å; [fcSi(CH₂Cl)Ph] ( 1 e ): 1.881(2), 1.884(2)). Solution‐state fluxionality of 5 a and 5 b , suggestive of reversible coordination of the NMe₂ group to silicon, was demonstrated by means of variable‐temperature NMR studies. The ΔG^≠ of the fluxional processes for 5 a and 5 b in CD₂Cl₂ were estimated to be 35.0 and 37.6 kJ mol^?1, respectively (35.8 and 38.3 kJ mol^?1 in [D₈]toluene). The quaternization of 5 a and 5 b by MeOTf, to give [fcSiMe(2‐C₆H₄CH₂NMe₃)][OTf] ( 7 a‐ OTf) and [fcSi(CH₂Cl)(2‐C₆H₄CH₂NMe₃)][OTf] ( 7 b‐ OTf), respectively, supported the reversibility of NMe₂ coordination at the silicon center as the source of fluxionality for 5 a and 5 b . Surprisingly, low room‐temperature stability was detected for 5 b due to its tendency to intramolecularly cyclize and form the spirocyclic [fcSi(cyclo‐CH₂NMe₂CH₂C₆H₄)]Cl ( 9 ‐Cl). This process was observed in both solution and the solid state, and isolation and Xray characterization of 9 ‐Cl was achieved. The model compound, [Fc₂Si(2‐C₆H₄CH₂NMe₂)₂] ( 8 ), synthesized through reaction of [Fc₂SiCl₂] with two equivalents of Li[2‐C₆H₄CH₂NMe₂] at ?78 °C, showed a lack of hypercoordination in both the solid state and in solution (down to ?80 °C). This suggests that either the reduced steric hindrance around Si or the unique electronics of the strained sila[1]ferrocenophanes is necessary for hypercoordination to occur.     

Formation of Organolithium Hetero‐Aggregates [Li4Ar2(nBu)2] (Ar=C6H4CH(Me)NMe2‐2) during the Directed ortho‐Lithiation of [1‐(Dimethylamino)ethyl]benzene

(R)‐[1‐(Dimethylamino)ethyl]benzene reacts with nBuLi in a 1:1 molar ratio in pentane to quantitatively yield a unique hetero‐aggregate ( 2 a ) containing the lithiated arene, unreacted nBuLi, and the complexed parent arene in a 1:1:1 ratio. As a model compound, [Li₄(C₆H₄CH(Me)NMe₂‐2)₂(nBu)₂] ( 2 b ) was prepared from the quantitative redistribution reaction of the parent lithiated arene Li(C₆H₄CH(Me)NMe₂‐2) with nBuLi in a 1:1 molar ratio. The mono‐Et₂O adduct [Li₄(C₆H₄CH(Me)NMe₂‐2)₂(nBu)₂(OEt₂)] ( 2 c ) and the bis‐Et₂O adduct [Li₄(C₆H₄CH(Me)NMe₂‐2)₂(nBu)₂(OEt₂)₂] ( 2 d ) were obtained by re‐crystallization of 2 b from pentane/Et₂O and pure Et₂O, respectively. The single‐crystal X‐ray structure determinations of 2 b – d show that the overall structural motifs of all three derivatives are closely related. They are all tetranuclear Li aggregates in which the four Li atoms are arranged in an almost regular tetrahedron. These structures can be described as consisting of two linked dimeric units: one Li₂Ar₂ dimer and a hypothetical Li₂nBu₂ dimer. The stereochemical aspects of the chiral Li₂Ar₂ fragment are discussed. The structures as observed in the solid state are apparently retained in solution as revealed by a combination of cryoscopy and ¹H, ¹³C, and ⁶Li NMR spectroscopy.     

Synthesis,Coordination Behavior,and Reduction Chemistry of Cymantrenyl‐1,3‐bis(2,3,4,5‐tetraphenyl)borole

We describe the synthesis of base‐free bisborole [Cym^?(BC₄Ph₄)₂]—Cym^?=(OC)₃Mn(η⁵‐C₅H₃)—and its transformation into two fully characterized Lewis acid–base adducts with pyridine bases of the type 4‐R? NC₅H₄ (R=tBu, NMe₂). The results of electrochemical, as well as NMR and UV/Vis spectroscopic studies on [Cym^?(BC₄Ph₄)₂] and the related monoborole derivative [Cym(BC₄Ph₄)]—Cym=(OC)₃Mn(η⁵‐C₅H₄)—provided conclusive evidence for 1) the enhanced Lewis acidity of the two boron centers that result from conjugation of two borole fragments, and 2) the fact that Mn? B bonding interactions between the Lewis acidic borole moieties and the Mn center are considerably less pronounced for bisborole [Cym^?(BC₄Ph₄)₂]. In addition, the reduction chemistry of [Cym^?(BC₄Ph₄)₂] has been studied in detail, both electrochemically and chemically. Accordingly, chemical reduction of [Cym^?(BC₄Ph₄)₂] with magnesium anthracene afforded the corresponding tetraanion, which features a rare Mg? OC bonding mode in the solid state.     

Four‐Center Oxidation State Combinations and Near‐Infrared Absorption in [Ru(pap)(Q)2]n (Q=3,5‐Di‐tert‐butyl‐N‐aryl‐1,2‐benzoquinonemonoimine,pap=2‐Phenylazopyridine)

The complex series [Ru(pap)(Q)₂]ⁿ ([ 1 ]ⁿ–[ 4 ]ⁿ; n=+2, +1, 0, ?1, ?2) contains four redox non‐innocent entities: one ruthenium ion, 2‐phenylazopyridine (pap), and two o‐iminoquinone moieties, Q=3,5‐di‐tert‐butyl‐N‐aryl‐1,2‐benzoquinonemonoimine (aryl=C₆H₅ ( 1⁺ ); m‐(Cl)₂C₆H₃ ( 2⁺ ); m‐(OCH₃)₂C₆H₃ ( 3⁺ ); m‐(tBu)₂C₆H₃ ( 4 ⁺)). A crystal structure determination of the representative compound, [ 1 ]ClO₄, established the crystallization of the ctt‐isomeric form, that is, cis and trans with respect to the mutual orientations of O and N donors of two Q ligands, and the coordinating azo N atom trans to the O donor of Q. The sensitive C? O (average: 1.299(3) Å), C? N (average: 1.346(4) Å) and intra‐ring C? C (meta; average: 1.373(4) Å) bond lengths of the coordinated iminoquinone moieties in corroboration with the N?N length (1.292(3) Å) of pap in 1 ⁺ establish [Ru^III(pap⁰)(Q^.?)₂]⁺ as the most appropriate electronic structural form. The coupling of three spins from one low‐spin ruthenium(III) (t_2g⁵) and two Q^.? radicals in 1 ⁺– 4 ⁺ gives a ground state with one unpaired electron on Q^.?, as evident from g=1.995 radical‐type EPR signals for 1 ⁺– 4 ⁺. Accordingly, the DFT‐calculated Mulliken spin densities of 1 ⁺ (1.152 for two Q, Ru: ?0.179, pap: 0.031) confirm Q‐based spin. Complex ions 1 ⁺– 4 ⁺ exhibit two near‐IR absorption bands at about λ=2000 and 920 nm in addition to intense multiple transitions covering the visible to UV regions; compounds [ 1 ]ClO₄–[ 4 ]ClO₄ undergo one oxidation and three separate reduction processes within ±2.0 V versus SCE. The crystal structure of the neutral (one‐electron reduced) state ( 2 ) was determined to show metal‐based reduction and an EPR signal at g=1.996. The electronic transitions of the complexes 1 ⁿ– 4 ⁿ (n=+2, +1, 0, ?1, ?2) in the UV, visible, and NIR regions, as determined by using spectroelectrochemistry, have been analyzed by TD‐DFT calculations and reveal significant low‐energy absorbance (λ_max>1000 nm) for cations, anions, and neutral forms. The experimental studies in combination with DFT calculations suggest the dominant valence configurations of 1 ⁿ– 4 ⁿ in the accessible redox states to be [Ru^III(pap⁰)(Q^.?)(Q⁰)]²⁺ ( 1 ²⁺– 4 ²⁺)→[Ru^III(pap⁰)(Q^.?)₂]⁺ ( 1 ⁺– 4 ⁺)→[Ru^II(pap⁰)(Q^.?)₂] ( 1 – 4 )→[Ru^II(pap^.?)(Q^.?)₂]^? ( 1 ^?– 4 ^?)→[Ru^III(pap^.?)(Q^2?)₂]^2? ( 1 ^2?– 4 ^2?).     

Synthesis and Characterization of donor‐functionalized ansa‐Cyclopentadienyl‐Indenyl and ansa‐Indenyl‐Indenyl Complexes of Yttrium,Samarium, Thulium,and Lutetium

The stepwise reaction of Me₂SiCl₂ with K[C₅H₃ ^tBuMe‐3] or Li[C₉H₇] and then with K[C₉H₆CH₂CH₂‐ NMe₂‐1] followed by double deprotonation with NaH or LiBu, yields the two dimethylsilicon bridged cyclopentadienyl‐indenyl and indenyl‐indenyl donor‐functionalized ligand systems K₂[(C₅H₂ ^tBu‐3‐Me‐5)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)] ( 1 ), and Li₂[(1‐C₉H₆)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)] ( 2 ), respectively. Treatment of 1 with YCl₃(THF)₃, SmCl₃(THF)_1.77, TmI₃(DME)₃, and LuCl₃(THF)₃ gives the mixed ansa‐metallocenes [(C₅H₂ ^tBu‐3‐Me‐5)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)]LnX (X = Cl, Ln = Y ( 3 ), Sm ( 4 ), Lu ( 5 ); X = I, Ln = Tm ( 6 )), respectively. The reaction of 2 with LuCl₃(THF)₃ yields [(1‐C₉H₆)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)]LuCl ( 7 ). Compound 4 reacts with LiMe to give the corresponding alkyl derivative [(C₅H₂ ^tBu‐3‐Me‐5)SiMe₂(1‐C₉H₅CH₂CH₂NMe₂‐3)]Sm(CH₃) ( 8 ). The new complexes were characterized by elemental analyses, MS spectrometry, and NMR spectroscopy. The molecular structures of 5 and 6 were determined by single crystal X‐ray diffraction.     

2,4‐Diamino‐6‐methyl‐1,3,5‐triazin‐1‐ium trifluoroacetate

Crystals of the title compound, C₄H₈N₅⁺·C₂F₃O₂⁻, are built up of singly protonated 2,4‐diamino‐6‐methyl‐1,3,5‐triazin‐1‐ium cations and trifluoroacetate anions. The CF₃ group of the anion is disordered. The oppositely charged ions interact via almost linear N—H...O hydrogen bonds, forming a CF₃COO⁻...C₄H₈N₅⁺ unit. Two units related by an inversion centre interact through a pair of N—H...N hydrogen bonds, forming planar (CF₃COO⁻...C₄H₈N₅⁺...C₄H₈N₅⁺·CF₃COO⁻) aggregates that are linked by a pair of N—H...O hydrogen bonds into chains running along the c axis.     

Gemischte Sandwichkomplexe der 4 f‐Elemente: Enantiomerenreine Cyclooctatetraenyl‐Cyclopentadienyl‐Komplexe des Samariums und Lutetiums mit donorfunktionalisierten Cyclopentadienylliganden

Organometallic Compounds of the Lanthanides. 139 Mixed Sandwich Complexes of the 4 f Elements: Enantiomerically Pure Cyclooctatetraenyl Cyclopentadienyl Complexes of Samarium and Lutetium with Donor‐Functionalized Cyclopentadienyl Ligands The reactions of [K{(S)‐C₅H₄CH₂CH(Me)OMe}], [K{(S)‐C₅H₄CH₂CH(Me)NMe₂}] and [K{(S)‐C₅H₄CH(Ph)CH₂NMe₂}] with the cyclooctatetraenyl lanthanide chlorides [(η⁸‐C₈H₈)Ln(μ‐Cl)(THF)]₂ (Ln = Sm, Lu) yield the mixed cyclooctatetraenyl cyclopentadienyl lanthanide complexes [(η⁸‐C₈H₈)Sm{(S)‐η⁵ : η¹‐C₅H₄CH₂CH(Me)OMe}] ( 1 a ), [(η⁸‐C₈H₈)Ln{(S)‐η⁵ : η¹‐C₅H₄CH₂CH(Me)NMe₂}] (Ln = Sm ( 2 a ), Lu ( 2 b )) and [(η⁸‐C₈H₈)Ln{(S)‐η⁵ : η¹‐C₅H₄CH(Ph)CH₂NMe₂}] (Ln = Sm ( 3 a ), Lu ( 3 b )). For comparison, the achiral compounds [(η⁸‐C₈H₈)Ln{η⁵ : η¹‐C₅H₄CH₂CH₂NMe₂}] (Ln = Sm ( 4 a ), Lu ( 4 b )) are synthesized in an analogous manner. ¹H‐, ¹³C‐NMR‐, and mass spectra of all new compounds as well as the X‐ray crystal structures of 3 b and 4 b are discussed.     

Neutral 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide and its salt forms with inorganic anions

Semicarbazones can exist in two tautomeric forms. In the solid state, they are found in the keto form. This work presents the synthesis, structures and spectroscopic characterization (IR and NMR spectroscopy) of four such compounds, namely the neutral molecule 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide, C₁₉H₁₆N₄O, (I), abbreviated as HBzPyS, and three different hydrated salts, namely the chloride dihydrate, C₁₉H₁₇N₄O⁺·Cl^?·2H₂O, (II), the nitrate dihydrate, C₁₉H₁₇N₄O⁺·NO₃^?·2H₂O, (III), and the thiocyanate 2.5‐hydrate, C₁₉H₁₇N₄O⁺·SCN^?·2.5H₂O, (IV), of 2‐[phenyl({[(phenylcarbamoyl)amino]imino})methyl]pyridinium, abbreviated as [H₂BzPyS]⁺·X^?·nH₂O, with X = Cl^? and n = 2 for (II), X = NO₃^? and n = 2 for (III), and X = SCN^? and n = 2.5 for (IV), showing the influence of the anionic form in the intermolecular interactions. Water molecules and counter‐ions (chloride or nitrate) are involved in the formation of a two‐dimensional arrangement by the establishment of hydrogen bonds with the N—H groups of the cation, stabilizing the E isomers in the solid state. The neutral HBzPyS molecule crystallized as the E isomer due to the existence of weak π–π interactions between pairs of molecules. The calculated IR spectrum of the hydrated [H₂BzPyS]⁺ cation is in good agreement with the experimental results.     

Iron(0), rhodium(I) and palladium(II) complexes with p‐(N,N‐dimethylaminophenyl) diphenylphosphine and the application of the palladium complex as a catalyst for the Suzuki–Miyaura cross‐coupling reaction

The reaction of p‐(N,N‐dimethylaminophenyl)diphenylphosphine [PPh₂(p‐C₆H₄NMe₂)] with [Fe₃(CO)₁₂], [Rh(CO)₂Cl]₂ and PdCl₂ resulted in three new mononuclear complexes, {Fe(CO)₄[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1a ), trans‐{Rh(CO)Cl[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 2 ) and trans‐{PdCl₂[η¹‐(P)‐PPh₂(p‐C₆H₄NMe₂)]₂} ( 3 ), respectively. A small amount of dinuclear nonmetal‐metal bonded complex, {Fe₂(CO)₈[µ‐(P,N)‐PPh₂(p‐C₆H₄NMe₂)]} ( 1b ), was also isolated as a side product in the reaction of [Fe₃(CO)₁₂]. The complexes were characterized by elemental analyses, mass, IR, UV–vis, ¹H, ¹³C (except 1b) and ³¹P{¹H} NMR spectroscopy. The Pd complex 3 effectively catalyzes the Suzuki–Miyaura cross‐coupling reactions of aryl halides with arylboronic acids in water–isopropanol (1:1) at room temperature. Excellent yields (up to 99% isolated yield) were achieved. The effects of different solvents, bases, catalyst quantities were also evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

Two isomorphous transition metal complexes containing a protonated diaminopurine ligand: diaquabis(2,6‐diamino‐7H‐purin‐1‐ium‐κN9)bis(homophthalato‐κO)nickel(II) tetrahydrate and the cobalt(II) analogue

The two isomorphous title compounds, [M(C₅H₇N₆)₂(C₉H₆O₄)₂(H₂O)₂]·4H₂O or M²⁺(Hdap⁺)₂(hpt²⁻)₂(H₂O)₂·4H₂O {where dap is 2,6‐diaminopurine, H₂hpt is homophthalic acid [2‐(2‐carboxyphenyl)acetic acid] and M is Ni^II or Co^II}, consist of neutral M²⁺(Hdap⁺)₂(hpt²⁻)₂(H₂O)₂ monomers, where the M^II cation lies on an inversion centre and its MN₂O₄ octahedral environment is defined by one N atom (from Hdap⁺), two O atoms (from one hpt²⁻ dianion and one water molecule) and their inversion images. The structures are unusual in that the Hdap⁺ cation occurs in an uncommon protonated state (as 2,6‐diamino‐7H‐purin‐1‐ium) and both ligands bind in an unprecedented monodentate fashion. The existence of a large number of donors and acceptors for hydrogen bonding, together with π–π interactions, leads to a rather complex three‐dimensional structure.     

Synthesis and Reactivity of Boron‐, Silicon‐, and Tin‐Bridged ansa‐Cyclopentadienyl–Cycloheptatrienyl Titanium Complexes (Troticenophanes)

A novel one‐pot method was developed for the preparation of [Ti(η⁵‐C₅H₅)(η⁷‐C₇H₇)] (troticene, 1 ) by reaction of sodium cyclopentadienide (NaCp) with [TiCl₄(thf)₂], followed by reduction of the intermediate [(η⁵‐C₅H₅)₂TiCl₂] with magnesium in the presence of cycloheptatriene (C₇H₈). The [n]troticenophanes 3 (n=1), 4 , 8 , 10 (n=2), and 11 (n=3) were synthesized by salt elimination reactions between dilithiated troticene, [Ti(η⁵‐C₅H₄Li)(η⁷‐C₇H₆Li)] ? pmdta ( 2 ) (pmdta=N,N′,N′,N′′,N′′‐pentamethyldiethylenetriamine), and the appropriate organoelement dichlorides Cl₂Sn(Mes)₂ (Mes=2,4,6‐trimethylphenyl), Cl₂Sn₂(tBu)₄, Cl₂B₂(NMe₂)₂, Cl₂Si₂Me₄, and (ClSiMe₂)₂CH₂, respectively. Their structural characterization was carried out by single‐crystal X‐ray diffraction and multinuclear NMR spectroscopy. The stanna[1]‐ and stanna[2]troticenophanes 3 and 4 represent the first heteroleptic sandwich complexes bearing Sn atoms in the ansa bridge. The reaction of 3 with [Pt(PEt₃)₃] resulted in regioselective insertion of the [Pt(PEt₃)₂] fragment into the Sn? C_ipso bond between the tin atom and the seven‐membered ring, which afforded the platinastanna[2]troticenophane 5 . Oxidative addition was also observed upon treatment of 4 with elemental sulfur or selenium, to produce the [3]troticenophanes [Ti(η⁵‐C₅H₄SntBu₂)(η⁷‐C₇H₆SntBu₂)E] ( 6 : E=S; 7 : E=Se). The B? B bond of the bora[2]troticenophane 8 was readily cleaved by reaction with [Pt(PEt₃)₃] to form the corresponding oxidative addition product [Ti(η⁵‐C₅H₄BNMe₂)(η⁷‐C₇H₆BNMe₂)Pt(PEt₃)₂] ( 9 ). The solid‐state structures of compounds 5 , 6 , and 9 were also determined by single‐crystal X‐ray diffraction.     

Formation,Dynamic Behavior,and Chemical Transformation of Pt Complexes with a Rotaxane‐like Structure

The reaction of [Pt(CH₂COMe)(Ph)(cod)] (cod=1,5‐cyclooctadiene) with (ArCH₂NH₂CH₂‐C₆H₄COOH)⁺(PF₆)^? (Ar=4‐tBuC₆H₄ or 9‐anthryl) in the presence of cyclic oligoethers such as dibenzo[24]crown‐8 (DB24C8) and dicyclohexano[24]crown‐8 (DC24C8) produces {(ce)[ArCH₂NH₂CH₂C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? (ce=DB24C8 or DC24C8, Ar=4‐tBuC₆H₄ or 9‐anthryl) with interlocked structures. FABMS and NMR spectra of a solution of these compounds indicate that the Pt complexes with a secondary ammonium group and DB24C8 (or DC24C8) make up the axis and cyclic components, respectively. Temperature‐dependent ¹H NMR spectra of a solution of {(DB24C8)[4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? ({(DB24C8)[ 4 ‐H]}⁺(PF₆)^?) show equilibration with free DB24C8 and the axis component. The addition of DB24C8 to a solution of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^? causes partial exchange of the macrocyclic component of the interlocked molecules, giving a mixture of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^?, {(DB24C8)[ 4 ‐H]}⁺(PF₆)^?, and free macrocyclic compounds. The reaction of 3,5‐Me₂C₆H₃COCl with {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? affords the organic rotaxane {(DB24C8)(4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOCOC₆H₃Me₂‐3,5)}⁺(PF₆)^? through C? O bond formation between the aroyl group and the carboxylate ligand of the axis component. The addition of 2,2′‐bipyridine (bpy) to a solution of {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? induces the degradation of the interlocked structure to form a complex with trigonal bipyramidal coordination, [Pt(Ph)(bpy)(cod)]⁺(PF₆)^?, whereas the reaction of bpy with [Pt(OCOC₆H₄Me‐4)(Ph)(cod)] produces the square‐planar complex [Pt(OCOC₆H₄Me‐4)(Ph)(bpy)].     

(Z)‐2‐Methylbuten‐1‐yl(aryl)iodonium trifluoromethanesulfonates containing electron‐withdrawing groups on the aryl moiety

The crystal structures of [(Z)‐2‐methyl­but‐1‐en‐1‐yl]­[4‐(tri­fluoro­methyl)­phenyl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₂H₁₃F₃I⁺·CF₃O₃S^?, (I), (3,5‐di­chloro­phenyl)­[(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₁H₁₂­Cl₂I⁺·CF₃O₃S^?, (II), and bis{[3,5‐bis­(tri­fluoro­methyl)­phenyl][(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium} bis­(tri­fluoro­methane­sulfonate) di­chloro­methane solvate, 2C₁₃H₁₂F₆I⁺·­2CF₃­O₃S^?·CH₂Cl₂, (III), are described. Neither simple acyclic β,β‐di­alkyl‐substituted alkenyl­(aryl)­idonium salts nor a series containing electron‐deficient aryl rings have been described prior to this work. Compounds (I)–(III) were found to have distorted square‐planar geometries, with each I atom interacting with two tri­fluoro­methane­sulfonate counter‐ions.     

Electronically Strongly Coupled Divinylheterocyclic‐Bridged Diruthenium Complexes

Complexes [{Ru(CO)Cl(PiPr₃)₂}₂(μ‐2,5‐(CH?CH)₂‐^cC₄H₂E] (E=NR; R=C₆H₄‐4‐NMe₂ ( 10 a ), C₆H₄‐4‐OMe ( 10 b ), C₆H₄‐4‐Me ( 10 c ), C₆H₅ ( 10 d ), C₆H₄‐4‐CO₂Et ( 10 e ), C₆H₄‐4‐NO₂ ( 10 f ), C₆H₃‐3,5‐(CF₃)₂ ( 10 g ), CH₃ ( 11 ); E=O ( 12 ), S ( 13 )) are discussed. The solid state structures of four alkynes and two complexes are reported. (Spectro)electrochemical studies show a moderate influence of the nature of the heteroatom and the electron‐donating or ‐withdrawing substituents R in 10 a – g on the electrochemical and spectroscopic properties. The CVs display two consecutive one‐electron redox events with ΔE°′=350–495 mV. A linear relationship between ΔE°′ and the σ_p Hammett constant for 10 a–f was found. IR, UV/Vis/NIR and EPR studies for 10 ⁺– 13 ⁺ confirm full charge delocalization over the {Ru}CH?CH‐heterocycle‐CH?CH{Ru} backbone, classifying them as Class III systems according to the Robin and Day classification. DFT‐optimized structures of the neutral complexes agree well with the experimental ones and provide insight into the structural consequences of stepwise oxidations.     

Ligand‐to‐Ligand Charge‐Transfer Transitions of Platinum(II) Complexes with Arylacetylide Ligands with Different Chain Lengths: Spectroscopic Characterization,Effect of Molecular Conformations,and Density Functional Theory Calculations

The complexes [Pt(tBu₃tpy){C?C(C₆H₄C?C)_n?1R}]⁺ (n=1: R=alkyl and aryl (Ar); n=1–3: R=phenyl (Ph) or Ph‐N(CH₃)₂‐4; n=1 and 2, R=Ph‐NH₂‐4; tBu₃tpy=4,4’,4’’‐tri‐tert‐butyl‐2,2’:6’,2’’‐terpyridine) and [Pt(Cl₃tpy)(C?CR)]⁺ (R=tert‐butyl (tBu), Ph, 9,9’‐dibutylfluorene, 9,9’‐dibutyl‐7‐dimethyl‐amine‐fluorene; Cl₃tpy=4,4’,4’’‐trichloro‐2,2’:6’,2’’‐terpyridine) were prepared. The effects of substituent(s) on the terpyridine (tpy) and acetylide ligands and chain length of arylacetylide ligands on the absorption and emission spectra were examined. Resonance Raman (RR) spectra of [Pt(tBu₃tpy)(C?CR)]⁺ (R=n‐butyl, Ph, and C₆H₄‐OCH₃‐4) obtained in acetonitrile at 298 K reveal that the structural distortion of the C?C bond in the electronic excited state obtained by 502.9 nm excitation is substantially larger than that obtained by 416 nm excitation. Density functional theory (DFT) and time‐dependent DFT (TDDFT) calculations on [Pt(H₃tpy)(C?CR)]⁺ (R= n‐propyl (nPr), 2‐pyridyl (Py)), [Pt(H₃tpy){C?C(C₆H₄C?C)_n?1Ph}]⁺ (n=1–3), and [Pt(H₃tpy){C?C(C₆H₄C?C)_n?1C₆H₄‐N(CH₃)₂‐4}]⁺/+H⁺ (n=1–3; H₃tpy=nonsubstituted terpyridine) at two different conformations were performed, namely, with the phenyl rings of the arylacetylide ligands coplanar (“cop”) with and perpendicular (“per”) to the H₃tpy ligand. Combining the experimental data and calculated results, the two lowest energy absorption peak maxima, λ₁ and λ₂, of [Pt(Y₃tpy)(C?CR)]⁺ (Y=tBu or Cl, R=aryl) are attributed to ¹[π(C?CR)→π*(Y₃tpy)] in the “cop” conformation and mixed ¹[d_π(Pt)→π*(Y₃tpy)]/¹[π(C?CR)→π*(Y₃tpy)] transitions in the “per” conformation. The lowest energy absorption peak λ₁ for [Pt(tBu₃tpy){C?C(C₆H₄C?C)_n?1C₆H₄‐H‐4}]⁺ (n=1–3) shows a redshift with increasing chain length. However, for [Pt(tBu₃tpy){C?C(C6H4C?C)_n?1C₆H₄‐N(CH₃)₂‐4}]⁺ (n=1–3), λ₁ shows a blueshift with increasing chain length n, but shows a redshift after the addition of acid. The emissions of [Pt(Y₃tpy)(C?CR)]⁺ (Y=tBu or Cl) at 524–642 nm measured in dichloromethane at 298 K are assigned to the ³[π(C?CAr)→π*(Y₃tpy)] excited states and mixed ³[d_π(Pt)→π*(Y₃tpy)]/³[π(C?C)→π*(Y₃tpy)] excited states for R=aryl and alkyl groups, respectively. [Pt(tBu₃tpy){C?C(C₆H₄C?C)_n?1C₆H₄‐N(CH₃)₂‐4}]⁺ (n=1 and 2) are nonemissive, and this is attributed to the small energy gap between the singlet ground state (S₀) and the lowest triplet excited state (T₁).     

Synthesis,Interionic Structure,and Reactivity toward CO and p‐Methylstyrene of Palladacyclic Compounds Bearing α‐Diimine Ligands

Palladacyclic compounds [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] (R = Et, ⁱPr, 2,6‐ⁱPr₂C₆H₃; N? N = bpy = 2,2′‐bipyridine, or 1,4‐(o,o′‐dialkylaryl)‐1,4‐diazabuta‐1,3‐dienes; [X]^? = [BF₄]^? or [PF₆]^?) were synthesized from the dimers [{Pd(C₆H₄(C₆H₅C?O)C?N? R)(μ‐Cl)}₂] and N? N ligands. Their interionic structure in CD₂Cl₂ was determined by means of ¹⁹F,¹H‐HOESY experiments and compared with that in the solid state derived from X‐ray single‐crystal studies. [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] complexes were found to copolymerize CO and p‐methylstyrene affording syndiotactic or isotactic copolymers when bpy or 1,4‐(o,o′‐dimethylaryl)‐1,4‐diazabuta‐1,3‐dienes were used, respectively. The reactions with CO and p‐methylstyrene of the bpy derivatives were investigated. Two intermediates derived from a single and a double insertion of CO into the Pd? C bonds were isolated and completely characterized in solution.     

A Brønsted‐Ligand‐Based Iron Complex as a Molecular Switch with Five Accessible States

A mononuclear Fe^II complex, prepared with a Brønsted diacid ligand, H₂L (H₂L=2‐[5‐phenyl‐1H‐pyrazole‐3‐yl] 6‐benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [Fe^II(H₂L)₂](BF₄)₂ ( 1_A ), exhibits abrupt spin transition at T_1/2=258 K, and treatment with base yields a deprotonated analogue [Fe^II(HL)₂] ( 1_B ), which shows gradual SCO above 350 K. A range of Fe^III analogues were also characterized. [Fe^III(HL)(H₂L)](BF₄)Cl ( 1_C ) has an S=5/2 spin state, while the deprotonated complexes [Fe^III(L)(HL)], ( 1_D ), and (TEA)[Fe^III(L)₂], ( 1_E ) exist in the low‐spin S=1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid‐state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.     

Ion Pairing and Salt Structure in Organic Salts through Diffusion,Overhauser, DFT and X‐ray Methods

Pulsed gradient spin‐echo (PGSE) diffusion characteristics for a) the new [brucinium][X] salts 6 a – f [ a : X=BF₄^?; b : X=PF₆^?; c : X=MeSO₃^?, d : X=CF₃SO₃^?; e : X=BArF^?; f : X=PtCl₃(C₂H₄)^?], b) 4‐tert‐butyl‐N‐benzyl analogue, 7 and c) the aryl carbocations (p‐R‐C₆H₄)₂CH 9 a (R=CH₃O) and 9 b (R=(CH₃)₂N), (p‐CH₃O‐C₆H₄)_xCPh_3?x⁺ 10 a – c (x=1–3, respectively) and (p‐R‐C₆H₄)₃C⁺ 11 (R=(CH₃)₂N) and 12 (R=H) all in several different solvents, are reported. The solvent dependence suggests strong ion pairing in CDCl₃, intermediate ion pairing in CD₂Cl₂ and little ion pairing in [D₆]acetone. ¹H, ¹⁹F HOESY NMR spectra (HOESY: heteronuclear Overhauser effect spectroscopy) for 6 and 7 reveal a specific approach of the anion with respect to the brucinium cation plus subtle changes, which are related to the anion itself. Further, for carbocations 9 – 12 , (all as BF₄^? salts) based on the NOE results, one finds marked changes in the relative positions of the BF₄^? anion. In these aryl cationic species the anion can be located either a) very close to the carbonium ion carbon b) in an intermediate position or c) proximate to the N or O atom of the p‐substituent and remote from the formally positive C atom. This represents the first example of such a positional dependence of an anion on the structure of the carbocation. DFT calculations support the experimental HOESY results. The solid‐state structures for 6 c and the novel Zeise's salt derivative, [brucinium][PtCl₃(C₂H₄)], 6 f , are reported. Analysis of ¹⁹⁵Pt NMR and other NMR measurements suggest that the η²‐C₂H₄ bonding to the platinum centre in 6 f is very similar to that found in K[PtCl₃(C₂H₄)]. Field dependent T₁ measurements on [brucinium][PtCl₃(C₂H₄)] and K[PtCl₃(C₂H₄)], are reported and suggested to be useful in recognizing aggregation effects.     

Isolation of a Three‐Coordinate Boron Cation with a Boron–Sulfur Double Bond

The reaction of the bulky bis(imidazolin‐2‐iminato) ligand precursor (1,2‐(L^MesNH)₂‐C₂H₄)[OTs]₂ ( 1 ²⁺ 2[OTs]^?; L^Mes=1,3‐dimesityl imidazolin‐2‐ylidene, OTs=p‐toluenesulfonate) with lithium borohydride yields the boronium dihydride cation (1,2‐(L^MesN)₂‐C₂H₄)BH₂[OTs] ( 2 ⁺ [OTs]^?)_. The boronium cation 2 ⁺ [OTs]^? reacts with elemental sulfur to give the thioxoborane salt (1,2‐(L^MesN)₂‐C₂H₄)BS[OTs] ( 3 ⁺ [OTs]^?). The hitherto unknown compounds 1 ²⁺ 2[OTs]^?, 2 ⁺ [OTs]^?, and 3 ⁺ [OTs]^? were fully characterized by spectroscopic methods and single‐crystal X‐ray diffraction. Moreover, DFT calculations were carried out to elucidate the bonding situation in 2 ⁺ and 3 ⁺. The theoretical, as well as crystallographic studies reveal that 3 ⁺ is the first example for a stable cationic complex of three‐coordinate boron that bears a B?S double bond.     

Bis[μ3‐1,8‐bis(triisopropylsilylamido)naphthalene]bis(tetrahydrofuran)di‐μ3‐oxido‐dimanganese(III)disodium

The solid‐state structure of the title compound, [Na₂Mn₂(C₃₂H₅₆N₂OSi₂)₂O₂] or [1,8‐C₁₀H₆(NSiⁱPr₃)₂Mn(μ₃‐O)Na(THF)]₂, which lies across a crystallographic twofold axis, exhibits a central [Mn₂O₂Na₂]⁴⁺ core, with two oxide groups, each triply bridging between the two Mn^III ions and an Na⁺ ion. Additional coordination is provided to each Mn^III centre by a 1,8‐C₁₀H₆(NSiⁱPr₃)₂ [1,8‐bis(triisopropylsilylamido)naphthalene] ligand and to the Na⁺ centres by a tetrahydrofuran molecule. The presence of an additional Na...H—C agostic interaction potentially contributes to the distortion around the bridging oxide group.