Cyclic (alkyl)(amino)carbene gold(I) complexes: A synthetic and structural investigation

A series of mono- and dicarbene gold(I) complexes of types Au(CAAC)(Cl) [CAAC = cyclic (alkyl)(amino)carbene] (1) and [Au(CAAC)₂]⁺[X]^? (X = Cl, AuCl₂) (2) have been prepared through reaction of AuCl(SMe₂) with free carbenes a–e, and structurally characterized by single X-ray diffraction studies (1a, 1b, 2d, 2e). In addition two new free cyclic (alkyl)(amino)carbenes (c and e) have been synthesized.     

Ligand properties of N-heterocyclic and Bertrand carbenes: A density functional study

In order to probe the ligand properties we have examined a series of Cr(CO)₅L and Ni(CO)₃L complexes using density functional theory (DFT). The ligands included in our study are N-heterocyclic carbenes (NHCs) and Bertrand-type carbenes. Our study shows that the carbene–metal bonds of imidazol-2-ylidenes (1), imidazolin-2-ylidenes (2), thiazo-2-ylidenes (3), and triazo-5-ylidenes (4) are significantly stronger than those of Bertrand-type carbenes (5–7). The force constants of C–O in complexes are related to the property of isolated carbenes such as proton affinity (PA), electronegativity (χ), and charge transfer (ΔN). NHCs and Bertrand-type carbenes are identified as nucleophilic, soft ligands. Carbene stabilization energy (CSE) computations indicate that carbenes 1 and 4 are the most stable species, while 2 and 3 are less stable. In contrast to NHCs, CSE of carbenes 5–7 are much smaller, and their relative stabilities are in the order (amino)(aryl) carbenes 7e–7g > (amino)(alkyl) carbenes 7a–7d > (phosphino)(aryl) 6d–6e, and (phosphino)(silyl) carbenes 5a–5c > (phosphino)(alkyl) carbenes 6a–6c.     

Asymmetric hydrogenation reactions with Rh and Ru complexes bearing phosphine–phosphites with an oxymethylene backbone

Phosphine–phosphites 3a and 3b, derived from diphenylhydroxymethyl phosphine have been prepared. From these ligands [Rh(COD)(3a)]BF₄ 5a and RuCl₂(3b)[(S,S)-DPEN] 6b (DPEN = 1,2-diphenylethylenediamine) were synthesized and their structure determined by X-ray diffraction. Ligands 3 are characterized by a small bite angle of 83°. In addition, 5a led to an active catalyst for the hydrogenation of olefins, giving enantioselectivities of up to 96% ee. Likewise, compound 6b showed good activity and enantioselectivity in the hydrogenation of N-1-phenyl ethylidene aniline and a completed reaction at S/C = 500 in 24 h with 83% ee.     

The high-pressure [4+2]cycloaddition of 1-methoxybuta-1,3-diene to the glycolaldehyde-derived heterodienophiles,catalyzed by chiral metallosalen complexes

A high-pressure (ca. 10 kbar) reaction of 1-methoxybuta-1,3-diene 1 with variously O-protected glycolaldehydes 2, catalyzed by the chiral (salen)Cr(III)Cl 4a–d and 5 or (salen)Co(II) 6a–f and 7 complexes, has been studied. The best results were obtained for tert-butyldimethylsilyloxyacetaldehyde 2a. The reaction afforded, in good yield (up to 90%) and with very good diastereoselectivity (up to 92%) and enantioselectivity (up to 93% ee), the [4+2]cycloadducts 3a, which are compounds of significant synthetic interest. The stereochemical model of the cycloaddition reaction is discussed.     

The reaction of amidinato(pyridine) complexes of molybdenum and tungsten with triethylborane adduct of N-heterocyclic carbene (NHC · BEt3): Investigation on the reactivity of NHC · BEt3 as carbene precursor toward transition metal complexes

The reaction of triethylborane adduct of N-heterocyclic carbene, NHC · BEt₃, (NHC = IⁱPr = 1,3-diisopropylimidazol-2-ylidene (IⁱPr · BEt₃; 1a), NHC = IMes = 1,3-dimesitylimidazol-2-ylidene (IMes · BEt₃; 1b)), which was prepared by the reaction of the corresponding imidazolium salt with one equivalent of LiBEt₃H, with amidinato(pyridine) complex, [M(η³-allyl){η²-(NPh)₂CH}(CO)₂(NC₅H₅)] (M = Mo; 2-Mo M = W; 2-W), was investigated. The reaction of compound 1 with complex 2 under toluene-reflux conditions resulted in the formation of carbene complex [M(η³-allyl){η²-(NPh)₂CH}(CO)₂(NHC)] (M = Mo, NHC = IⁱPr; 3a-Mo, M = Mo, NHC = IMes; 3b-Mo, M = W, NHC = IⁱPr; 3a-W, M = W, NHC = IMes; 3b-W). These complexes were characterized spectroscopically as well as by X-ray analyses. Complex 3a-Mo was formed in various solvents such as 1,2-dimethoxyethane (DME), 1,2-dichloroethane, and acetonitrile under refluxing conditions for 3 h. In toluene, 3a-Mo was obtained in a good yield by heating at 70 °C for only 20 min. Employment of NHC · BEt₃ (1) was found to afford convenient route for the introduction of the carbene ligand to the transition metal complexes.     

Functionalized N-heterocyclic carbene iridium complexes: Synthesis,structure and addition polymerization of norbornene

Picolyl, pyridine, and methyl functionalized N-heterocyclic carbene iridium complexes [Cp¹Ir(C^N)Cl]Cl (4, C^N = 3-Methyl-1-picolyimidazol-2-ylidene), [Cp¹Ir(C^N)Cl][Cp¹IrCl₃] (5), [Cp¹Ir(C-N)Cl]Cl (6, C-N = 3-Methyl-1-pyridylimidazol-2-ylidene) and [Cp¹Ir(L)Cl₂] (7, L = 1,3-dimethylimidazol-2-ylidene) have been synthesized by transmetallation from Ag(I) carbene species, and characterized by ¹H NMR, ¹³C NMR spectra and elemental analyses. The molecular structures of 5–7 have been confirmed by X-ray single-crystal analyses. The iridium carbene complexes 4 and 6 show moderate catalytic activities (3.03 × 10⁵ g PNB (mol Ir)^?1 h^?1 and 1.70 × 10⁶ g PNB (mol Ir)^?1 h^?1) for the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as co-catalyst. The produced polynorbornene have been characterized by IR, ¹H NMR and ¹³C NMR spectra, showing it follows the vinyl-addition-type of polymerization.     

Tuning the electronic properties of Fe2(μ-arenedithiolate)(CO)6−n(PMe3)n (n = 0, 2) complexes related to the [Fe–Fe]-hydrogenase active site

Complexes [Fe₂(μ-S₂Ar)(CO)₆] (S₂Ar) = benzene-1,2-dithiolate (1a) toluene-3,4-dithiolate (2a), 3,6-dichloro-1,2-benzenedithiolate (3a), quinoxaline-2,3-dithiolate (7a) have been prepared to investigate the electronic effect that different bridging arenedithiolate ligands have on the appended Fe₂(CO)₆ sites. Dinuclear complexes [Fe₂(μ-S₂Ar)(CO)₄(PMe₃)₂] (1–3,7)b and mononuclear complexes [Fe(S₂Ar)(CO)₂(PMe₃)₂] (1–3,7)c were synthesized from their parent hexacarbonyl complexes (1–3,7)a. IR spectroscopic, crystallographic and electrochemical analyses show that an increase of the electron-withdrawing character (where quinoxaline-2,3-dithiolate > 3,6-dichloro-1,2-benzenedithiolate > 1,2-benzenedithiolate ≥ toluene-3,4-dithiolate) of the bridging ligand leads to a decreased electron density at the iron centers, which yield a milder reduction potential and higher eCO stretching frequencies. This effect is coherent for all of the investigated complexes. Electrocatalytic proton reduction by complex 3a (with trifluoromethanesulfonic acid) was evidenced by cyclic voltammetry. As a result of the milder reduction potential of 3a itself, proton reduction that is promoted by 3a proceeds at a potential that is milder than that for the 1a-catalyzed process.     

Metal–metal bond cleavage of carbene complexes by halogens: The crystal and molecular structures of ax-[Mn2(CO)9{C(OEt)2-thienyl}], [Mn(CO)4(I){C(OEt)2-thienyl}] and eq-[Mn2(CO)9{C(NH2)2-thienyl}]

The metal–metal bond in [M₂(CO)₉{C(OEt)R}] (M = Mn (1), Re (2), R = 2-thienyl (a), 2-bithienyl (b)) is readily cleaved with halogens to afford cis-[M(CO)₄(X){C(OEt)R}] (M = Mn (3), X = I; M = Re (4), X = Br). In the binuclear manganese complex, the carbene ligand is found in an axial position due to steric reasons, whereas the electronically favoured equatorial position is found for the carbene ligands in the corresponding rhenium complexes and in [Mn₂(CO)₉{C(NH₂)thienyl}] (5a), containing a sterically less demanding NH₂-substituent.     

A convenient route to six-membered heterocyclic carbene complexes: Reactions of aminoallenylidene complexes with 1,3-bidentate nucleophiles

Pentacarbonyl dimethylamino(methoxy)allenylidene complexes of chromium and tungsten, [(CO)₅MCCC(NMe₂)OMe] (M = Cr (1a), W (1b)), react with 1,3-bidentate nucleophiles such as amidines and guanidine, H₂N–C(NH)R (R = Ph, C₆H₄NH₂-4, C₆H₄NO₂-3, NH₂), by displacing the methoxy substituent to give exclusively dimethylamino(imino)-allenylidene complexes, [(CO)₅MCCC{NC(NH₂)R}NMe₂] (2a–5a, 2b). Treatment of the chromium complexes 2a–5a with catalytic amounts of hydrochloric acid or HBF₄ gives rise to an intramolecular cyclization. Addition of the terminal NH₂ substituent to the C_α–C_β bond of the allenylidene chain affords pyrimidinylidene complexes 6–9 in high yield. In contrast to the chromium complexes 2a–5a, the corresponding tungsten complex 2b could not be induced to cyclize due to the lower electrophilicity of the α-carbon atom in 2b. The dimethylamino(phenyl)allenylidene complex [(CO)₅CrCCC(NMe₂)Ph] (10) reacts with benzamidine or guanidine similarly to 1a. However, the second reaction step – cyclization to give pyrimidinylidene complexes – proceeds much faster. Therefore, the formation of an imino(phenyl)allenylidene complex as an intermediate is established only by IR spectroscopy. The analogous reaction of 10 with 3-amino-5-methylpyrazole affords, via a formal [3+3]-cycloaddition, a pyrazolo[1,5a]pyrimidinylidene complex 13. Compound 13 is obtained as two isomers differing in the relative position of the N-bound proton (1H or 4H). The related reaction of 10 with thioacetamide yields a thiazinylidene complex and additionally an alkenyl(amino)carbene complex.     

Some recent applications of Fischer carbenemetal complexes in organic synthesis

{[2-(Dialkylamino)ethenyl]ethoxycarbene}chromium complexes 4 have been made available from lithiated terminal alkynes, hexacarbonylchromium, triethyloxonium tetrafluoroborate and secondary amines in a one-pot operation, in good to excellent yields. Reactions of these complexes with alkynes afford 5-dialkylamino-3-ethoxycyclopentadienes 8 with excellent chemoselectivity. From cyclopentadienes of type 8, angular and linear triquinanes, di- and triannelated benzene derivatives 24/25, steroid-like skeletons 30/31, and hexacycles 32/33 can be obtained with great facility. In addition, otherwise not easily accessible cyclopenta[b]pyrans 42/43 and novel spiro[4.4]nonatrienes 52/53 can be prepared in single operational steps from complexes 4 and terminal alkynes via [3 + 2 + 2 + 1] and [3 + 2 + 2 + 2] cocyclizations incorporating two and three alkyne units, respectively. Upon heating simple Fischer carbene complexes of type 2 with methylenecyclopropanes 64, cyclopentenones 65 are formed by formal [4 + 1] cycloadditions. New carbenemetal complexes which have different chemical reactivities can be formed in situ by transmetallation from the corresponding carbenechromium complexes. Various cyclopentenone, cyclopentene and cycloheptanone derivatives are easily accessible from these new carbenemetal (nickel and rhodium) complexes and an alkyne or an allene.     

Synthesis of electron-rich platinum centers: Platinum0(carbene)(alkene)2 complexes

The synthesis and molecular structure of the zero-valent platinum-mono-carbene-bis-alkene complexes [Pt⁰(NHC)(dimethyl fumarate)₂] (NHC = 1,3-dimesityl-imidazol-2-ylidene (1a); 1,3-dimesityl-dihydroimidazol-2-ylidene (2a); diphenyl-dihydroimidazol-2-ylidene (2b) are described. Two routes have been evaluated for the synthesis of 1a and 2a, involving reaction of a zero-valent platinum compound either with an isolated carbene ligand, or with an in situ generated carbene ligand. The in situ method proved to be easier and gave similar yields of about 50% after crystallization. Attempts have been made to synthesize similar compounds with N-phenyl and N-alkyl groups, of which the latter met with little success. However, (1,3-diphenyl-dihydroimidazol-2-ylidene)-bis(η²-dimethyl fumarate) platinum(0) (2b) could be obtained in 49% yield, after crystallization, from the appropriate Wanzlick dimer.Compound 1a reacts with H₂ and D₂ in sequences of oxidative addition, migration–insertion involving dimethyl fumarate, and reductive elimination to form neutral hydrido platinum (II) carbene complexes, probably containing a metallacyclic (R)–CO … Pt unit.     

Synthesis and characterization of novel five-membered palladacycles

3-(2-Chloroquinolin-3-yl)-1,5-bis(3,4,5-trimethoxy-phenyl)-pentane-2,4-dione derivatives 3a–b were conveniently synthesized in excellent yields (82% each) by tandem Knoevenagel condensation reactions of 2-chloro-3-carbaldehyde-quinoline 1a–b with 3,4,5-trimethoxy acetophenone, followed by a base catalyzed Michael addition, such as DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) with or without solvent. The reactions of 3a–b with Pd(dba)₂ in the presence of PPh₃ (1:2) in degassed acetone provided the dinuclear palladium complexes {Pd(C,N-2-C₉H₄N–CH–[–CH₂CO(3,4,5-(OMe-)₃–C₆H₂-]₂–3-R-6)Cl(PPh₃)}₂ [(R = H (4a), R = OMe (4b)] in moderate yields (38% and 43%), which in turn reacted with an excess of isonitrile XyNC (Xy = 2,6-Me₂C₆H₃) to give the corresponding palladacycles 5a–b in moderate yields (45% and 43%). The palladacycles 5a–b were also obtained in similar yields (32% and 33%) via a one-pot oxidative addition reaction of 3a-b with isonitrile XyNC:Pd(dba)₂ (4:1). The products were characterized by satisfactory elemental analysis and spectral studies (IR, ¹H, and ³¹P NMR). The crystal structure of 5a was determined by X-ray crystallography diffraction studies.     

First examples of dipyrido[1,2-c:2′,1′-e]imidazolin-7-ylidenes serving as NHC-ligands: Synthesis,properties and structural features of their chromium and tungsten pentacarbonyl complexes

The first use of dipyridocarbenes as Arduengo–Wanzlick type carbene ligands for transition metal complexes is reported. The complexes M(CO)₅L (L = dipyridoimidazolinylidene, di-tert-butyldipyridoimidazolinylidene, M = Cr, W) were synthesized and their spectroscopic and structural properties compared with the literature known N-heterocyclic carbene (NHC) group 6 metal pentacarbonyl complexes. This reveals that the ¹³C NMR carbene signals of theses complexes with dipyrido carbene ligands show the strongest high-field shift ever observed for M(CO)₅(NHC) (M = Cr, W) complexes. The structural characterization shows alternating single and double bonds in the conjugated dipyrido moiety of the ligand.     

An expedient approach to ferrocenyl thioamides via Fischer carbenes

Oxidative demetalation of Fischer ferrocenyl ethoxy carbene complexes (1a–c, M = Cr, Mo, W) and new Fischer ferrocenyl R-amino carbene complexes [2–5 (a–c), 11–15 (a–c), and 21–22 (a–c); M = Cr, Mo, W; R = H, CH₃, C₂H₅, C₃H₇, (CH₂)₂OH, (CH₂)₃OH, (CH₂)₂(OMe)₂, (CH₂)₃N(Me)₂, CH₂CHCH₂, (CH₂)₂OSi(CH₃)₃, (CH₂)₃OSi(CH₃)₃] with elemental sulfur–NaBH₄ were carried out under mild conditions, obtaining O-ethyl ferrocenecarbothioate (6) and novel ferrocenyl thioamides (7–10 and 16–20) in excellent yields.     

Synthesis and X-ray structures of rhodium complexes with new chiral biaryl-based NHC-ligands

A new series of chiral NHC–rhodium complexes has been prepared from the reactions between [Rh(COD)Cl]₂, NaOAc, KI and dibenzimidazolium salt 4a or monobenzimidazolium salts 4b–d, which are derived from chiral 2,2′-diamino-6,6′-dimethyl-1,1′-biphenyl, 2,2′-diamino-1,1′-binaphthyl or 6,6′-dimethyl-2-amino-2′-hydroxy-1,1′-biphenyl. The steric and electronic effects of the ligand play an important role in the complex formation. For example, treatment of chiral monobenzimidazolium salt 4b (with a NMe₂ group) with 0.5 equiv of [Rh(COD)Cl]₂ in the presence of NaOAc and KI in CH₃CN at reflux gives a chiral Rh(I) complex 5b, while chiral monobenzimidazolium salt 4d (with a MeO group) affords a racemic Rh(I) complex 5d. Under similar reaction conditions, treatment of dibenzimidazolium salt 4a with 0.5 equiv of [Rh(COD)Cl]₂ in the presence of NaOAc and KI gives a racemic Rh(III) complex 5a, while the dibenzimidazolium salt [C₂₀H₁₂(C₇H₅N₂Me)₂]I₂ derived from chiral 2,2′-diamino-1,1′-binaphthyl affords a chiral Rh(III) complex [C₂₀H₁₂(C₇H₄N₂Me)₂]RhI₂(OAc). All compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of the rhodium complexes have been further confirmed by X-ray diffraction analyses.     

Oxidative addition of MeI to cationic Rh(I) carbonyl complexes with pyridyl bis(carbene) ligands

A series of cationic Rh(I) carbonyl complexes of the form [Rh(CO)(L)]PF₆ (where L = 2,6-bis (alkylimidazol-2-ylidene)-pyridine; alkyl = Me (1a), Et (1b), CH₂Ph (1c)) have been prepared by the reactions of [Rh(CO)₂(OAc)]₂ with diimidazolium pyridine salts in the presence of NEt₃. The ν(CO) values for 1 are ca. 1982 cm⁻¹, indicating that the N-heterocyclic carbene ligands impart high electron density on the Rh(I) centres, despite the overall cationic charge. Each of the Rh(I) complexes reacts with MeI to form two isomeric Rh(III) methyl species, and a third unidentified species. Kinetic measurements on the MeI oxidative addition reactions give second-order rate constants (MeCN, 25 °C) of 0.0927, 0.0633 and 0.0277 M⁻¹ s⁻¹ for 1a, 1b and 1c, respectively. Comparison of these data with those for related Rh(I) carbonyl complexes shows that 1 have remarkably high nucleophilicity for cationic species.     

Intramolecularly donor-stabilized silenes: Part 6. The synthesis of 1-[2,6-bis(dimethylaminomethyl)phenyl]silenes and their reaction with aromatic aldehydes

The intramolecularly donor-stabilized silenes ArR¹SiC(SiMe₃)₂ (3a–d) (3a: R¹ = Me; 3b: R¹ = t-Bu; 3c: R¹ = Ph; 3d: R¹ = SiMe₃; Ar = 2,6-(Me₂NCH₂)₂C₆H₃) were prepared by treatment of the (dichloromethyl)oligosilanes (Me₃Si)₂R¹Si–CHCl₂ (1a–d), with 2,6-bis(dimethylaminomethyl)phenyllithium (molar ratio 1:2). For 3c and 3d, X-ray structural analyses were performed indicating that only one dimethylamino group of the tridentate ligand is coordinated to the electrophilic silene silicon atoms, i.e., the central silicon atoms are tetracoordinated. The N → Si donation leads to pyramidalization at the silene silicon atoms; the configuration at the silene carbon atoms is planar. For a chemical characterization 3a and 3c were treated with water to give the silanols ArR¹Si(OH)–CH(SiMe₃)₂ (5a,c). Studies of the reactions of 3a and 3c with benzaldehyde, 4-chlorobenzaldehyde or 4-methoxybenzaldehyde, respectively, revealed an unexpected reaction path leading to the substituted 2-oxa-1-sila-1,2,3,4-tetrahydronaphthalenes 12a, 12c, 13 and 14. Both 12a and 12c were structurally characterized by X-ray analyses. The formation of these six-membered cyclic compounds, which is discussed in detail, gives support to a dipolar mechanism for the general reaction of silenes with carbonyl derivatives.     

Palladium(II) complexes with the new P,N-type ligand (2-oxazoline-2-ylmethyl)di-isopropylphosphine as intermediates in CO/ethylene or CO/methyl acrylate insertion

The ligand (i-Pr)₂PCH₂(oxazoline) (1a), of the P,N-donor type, was reacted with [PdMeCl(COD)] to yield the square planar methylpalladium(II) complex [PdClMe(P,N)] (P,N = 1a) (2a), from which the complex [PdMe(P,N)OTf] (OTf = OSO₂CF₃) (3a) was obtained by AgOTf-promoted chloride abstraction. The alkyl complexes

(P,N = 1a) (5a, R = H; 7a, R = C(O)OMe) have been isolated from the initial CO/ethylene or CO/methyl acrylate insertion steps into the Pd–Me bond of 3a, respectively, and spectroscopically characterized. Complexes 2a, 3a and 7a have been fully characterized by single crystal X-ray diffraction. Complex 7a is still a rare example of a structurally characterized CO/methyl acrylate stepwise insertion product. These complexes are relevant to the alternating copolymerization of olefins and carbon monoxide catalyzed by palladium complexes. In addition, the centrosymmetric dinuclear complex trans-[Pd(μ-Cl){(i-Pr)₂PCH₂(oxazoline)}]₂(OTf)₂ (6) has been obtained and characterized by X-ray diffraction; it appears to be the first dinuclear complex of the type [Pd(μ-Cl)(P,N)]₂ to be characterized by X-ray crystallography.

Résumé

Le ligand (i-Pr)₂PCH₂(oxazoline) (1a), de type donneur P,N, réagit avec [PdClMe(COD)] pour former le complexe plan carré méthylpalladium(II) [PdClMe(P,N)] (P,N = 1a) (2a), à partir duquel le complexe [PdMe(P,N)OTf] (OTf = OSO₂CF₃) (3a) a été obtenu par abstraction de chlorure à l'aide de AgOTf. Les complexes alkyles

(P,N = 1a) (5a, R = H; 7a, R = C(O)OMe), ont été isolés lors des premières étapes d'insertion de CO/éthylène ou de CO/acrylate de méthyle, respectivement, dans la liaison Pd–Me de 3a, et caractérisés par méthodes spectroscopiques. Les complexes 2a, 3a et 7a ont été complètement caractérisés par diffraction des rayons X sur monocristal. Le complexe 7a est un exemple encore rare de produit d'insertion par étapes de CO/acrylate de méthyle qui ait été caractérisé structuralement. Ces complexes sont pertinents pour la copolymérisation alternée d'oléfines et de monoxyde de carbone catalysée par les complexes du palladium. En outre, le complexe dinucléaire centrosymétrique trans-[Pd(μ-Cl){(i-Pr)₂PCH₂(oxazoline)}]₂(OTf)₂ (6) a été obtenu et caractérisé par diffraction des rayons X; il s'agit du premier complexe dinucléaire de type [Pd(μ-Cl)(P,N)]₂ à être caractérisé par diffraction des rayons X.     

Synthesis of heteronuclear (MoRu2) clusters from 16-electron half-sandwich complexes (p-Cymene)Ru[E2C2(B10H10)] (E = S,Se)

The heterometallic cluster complexes {(p-Cymene)Ru[S₂C₂(B₁₀H₁₀)]}Mo(CO)₂{(CO)₃Ru[S₂C₂(B₁₀H₁₀)]} (2) and {(p-Cymene)Ru[Se₂C₂(B₁₀H₁₀)]}₂Mo(CO)₂ (3) (p-Cymene = η⁶-4-isopropyl-toluene) have been synthesized from the reactions of 16-electron half-sandwich ruthenium 1,2-dichalcogenolate carborane complexes (p-Cymene)Ru[E₂C₂(B₁₀H₁₀)] (E = S(1a), Se(1b)) with Mo(CO)₃(Py)₃ in the presence of BF₃ · Et₂O. The complexes of 2 and 3 were characterized by elemental analysis and IR, NMR spectra. The molecular structure of 2 has been characterized by single-crystal X-ray diffraction analysis. Complex 2 is unsymmetrical and the two Ru–Mo single bonds (2.7893(14), 2.8189(13) Å) are each supported by a symmetrically bridging o-carborane-1,2-dithiolato ligand.     

Second-order non-linear optical response in LB films for the metal complexes

The complexes with long alkyl chains {[Fe(C₁₆-trz)₃](ClO₄)₂}_n (1), [Fe(C₁₅-BPT)₂(NCS)₂] (2), [Fe(C₁₆-salen)Cl] (3), [Fe(C₁₆-salmmen)Cl] (4), K[Fe(C₁₆-salen)(CN)₂] (5), K[Fe(C₁₆-salmmen)(CN)₂] (6), Na[Fe(C₁₆-salmmen)(CN)₂] (7), [Mn(C₁₆-salen)Cl] (8), [Ni(C₁₆-salen)] (9), [Cu(C₁₆-salen)] (10) were synthesized (C₁₆-trz = 4-hexadecyl-1,2,4-triazole, C₁₅-BPT = N-(3,5-di-2-pyridinyl-4H-1,2,4-triazol-4-yl)-hexadecanecarboxamide, C₁₆-salen = N,N-bis[4-(hexadecyloxy)salicylidene]ethylenediamine, C₁₆-salmmen = N,N′-bis[4-(hexadecyloxy)salicylidene]-1,2-diaminopropane). Langmuir–Blodgett (LB) films of compounds 1–10 were prepared (Scheme 1). The transfers of the molecules from onto the gas–water surface to glass substrate were confirmed by UV–Vis spectra. The second harmonic generation (SHG) were estimated for the LB films formed by the metal complexes. The SHG was observed for the complexes with the long alkyl chains in LB film. The order of the intensity for the SHG related with the number of unpaired d electrons or the d electron configurations.