Insertion reactions of alkynes and organic isocyanides into the palladium-carbon bond of dimetallic Fe-Pd alkoxysilyl complexes

Insertion of MeO(2)C-C[triple bond]C-CO(2)Me (DMAD) into the Pd-C bond of the heterodimetallic complex [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d(dmba-C)] (2) (dppm = Ph(2)PCH(2)PPh(2), dmba-C = metallated dimethylbenzylamine) and [(OC)(3){(MeO)(3)Si}F[upper bond 1 start]e(mu-dppm)P[upper bond 1 end]d(8-mq-C,N)] (3) (8-mq-C,N = cyclometallated 8-methylquinoline) yielded the sigma-alkenyl complexes [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{C(CO(2)Me)=C(CO(2)Me)(o-C(6)H(4)CH(2)NMe(2))}] (7) and [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{C(CO(2)Me)[double bond, length as m-dash]C(CO(2)Me)(CH(2)C(9)H(6)N)}] (8), respectively. The latter afforded the adduct [(OC)(3){(MeO)(3)Si}F[upper bond 1 start]e(mu-dppm)P[upper bond 1 end]d{C(CO(2)Me)=C(CO(2)Me)(CH(2)C(9)H(6)N)}(CNBu(t))] (9) upon reaction with 1 equiv. of Bu(t)NC. The heterodinuclear sigma-butadienyl complexes [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{C(Ph=C(Ph)C(CO(2)Me)=(CO(2)Me)(o-C(6)H(4)CH(2)NMe(2))}] (11) and [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{C(Ph)=C(CO(2)Et)C(Ph)=C(CO(2)Et)(CH(2)C(9)H(6)N)}] (13) have been obtained by reaction of the metallate K[Fe{Si(OMe)(3)}(CO)(3)(dppm-P)] (dppm = Ph(2)PCH(2)PPh(2)) with [P[upper bond 1 start]dCl{C(Ph)=C(Ph)C(CO(2)Me)=C(CO(2)Me)(o-C(6)H(4)CH(2)N[upper bond 1 end]Me(2))}] or [P[upper bond 1 start]dCl{C(Ph)=C(CO(2)Et)C(Ph)=(CO(2)Et)}(CH(2)C(9)H(6)N[upper bond 1 end])], respectively. Monoinsertion of various organic isocyanides RNC into the Pd-C bond of 2 and 3 afforded the corresponding heterometallic iminoacyl complexes. In the case of complexes [(OC)(3){(MeO)(3)Si}F[upper bond 1 start]e(mu-dppm)P[upper bond 1 end][upper bond 1 start]d{C=(NR)(CH(2)C(9)H(6)N[upper bond 1 end])}] (15a R = Ph, 15b R = xylyl), a static six-membered C,N chelate is formed at the Pd centre, in contrast to the situation in [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{C(=NR)(o-C(6)H(4)CH(2)NMe(2))}] (14a R = o-anisyl, 14b R = 2,6-xylyl) where formation of a mu-eta(2)-Si-O bridge is preferred over NMe(2) coordination. The outcome of the reaction of the dimetallic alkyl complex [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]dMe] with RNC depends both on the stoichiometry and the electronic donor properties of the isocyanide employed for the migratory insertion process. In the case of o-anisylisocyanide, the iminoacyl complex [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{C(=N-o-anisyl)Me}] (16) results from the reaction in a 1 : 1 ratio. Addition of three equiv. of o-anisylisocyanide affords the tris(insertion) product [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{[C(=N-o-anisyl)](3)Me}] (18). After addition of a fourth equivalent of o-anisylNC, exclusive formation of the isocyanide adduct [(OC)(3){(MeO)(3)Si}F[upper bond 1 start]e(mu-dppm)P[upper bond 1 end]d{[C(=N-o-anisyl)](3)Me}(CN-o-anisyl)] (19) was spectroscopically evidenced. In the complex [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]d{[C(=N-o-C(6)H(4)COCH(2))](2)Me}] (20), the sigma-bound diazabutadienyl unit is part of a 12-membered organic macrocyle which results from bis(insertion) of 1,2-bis(2-isocyanophenoxy)ethane into the Pd-Me bond of the precursor complex [(OC)(3)F[upper bond 1 start]e{mu-Si(OMe)(2)([lower bond 1 start]OMe)}(mu-dppm)P[lower bond 1 end][upper bond 1 end]dMe]. In contrast, addition of two equivalents of tert-butylisocyanide to a solution of the latter afforded [(OC)(3){(MeO)(3)Si}F[upper bond 1 start]Fe(mu-dppm)P[upper bond 1 end]d{C(=NBu(t))Me}(CNBu(t))] (21) in which both a terminal and an inserted isocyanide ligand are coordinated to the Pd centre. In all cases, there was no evidence for competing CO substitution at the Fe(CO)(3) fragment by RNC. The molecular structures of the insertion products 8 x CH(2)Cl(2) and 16 x CH(2)Cl(2) have been determined by X-ray diffraction.     

Structural and catalytic studies of lithium complexes bearing pendant aminophenolate ligands

Lithium complexes bearing mono-anionic aminophenolate ligands are described. Reactions of ligand precursors HON(Me)Ph(OMe), HON(Me)Ph(SMe), HON(Me)C(OMe) or HON(Me)C(NMe2) [HON(Me)Ph(OMe) = (2-OMeC6H4CH2)N(Me)(CH2-2-HO-3,5-C6H2((t)Bu)2); HON(Me)Ph(SMe)= (2-SMe-C6H4CH2)N(Me)(CH2-2-HO-3,5-C6H2((t)Bu)2); HON(Me)C(OMe) = (MeOCH(2)CH2)N(Me)(CH2-2-HO-3,5-C6H2((t)Bu)2); HON(Me)C(NMe2) = (Me2NCH2CH2)N(Me)(CH2-2-HO-3,5-C6H2((t)Bu)2)] with 1.1-1.3 molar equivalents of (n)BuLi in diethyl ether solution afford (LiON(Me)Ph(OMe))(2) (3), (LiON(Me)Ph(SMe))2 (4), (LiON(Me)C(OMe))2 (5) and (LiON(Me)C(NMe2))2 (6) as dinuclear lithium complexes. The BnOH adduct of , (BnOH)(LiON(Me)C(OMe)) (7), was prepared from the reaction of and BnOH in diethyl ether solution. The molecular structures are reported for ligand precursor HON(Me)Ph(SMe) and compounds 3-5 and 7. These dinuclear lithium complexes show excellent catalytic activities toward the ring-opening polymerization of L-lactide in the presence of benzyl alcohol.     

Reactivity of Phosphaalkenes toward Carbene Complexes

Reaction of phosphaalkenes RP=C(NMe 2 ) 2 (R = t -Bu, Me 3 Si), featuring an inverse distribution of electron density about the P--C double bond, with Fischer carbene complexes [(CO) 5 M=C(OEt)Ar] (Ar=Ph, 2-MeC 6 H 4 , 2-MeOC 6 H 4 , M = Cr, W) afforded a mixture of complexes [(CO) 5 M{P(R)=C(NMe 2 ) 2 }] and [(CO) 5 M{P(R)=C(OEt)Ar}]. The treatment of phosphaalkene HP=C(NMe 2 ) 2 with compound [(CO) 5 W=C(OEt)(2-MeOC 6 H 4 )] gives rise to the formation of an ( E / Z )-mixture of [(CO) 5 W{P(CH(NMe 2 ) 2 )=C(OEt)(2-MeOC 6 H 4 )}].     

Structural Aspects of Lithium Arenethiolate Complexes with Intramolecular Coordinating Amine Donors

Reaction of aryllithium reagents LiR (R = C(6)H(4)((R)-CH(Me)NMe(2))-2 (1a), C(6)H(3)(CH(2)NMe(2))(2)-2,6 (1b), C(6)H(4)(CH(2)N(Me)CH(2)CH(2)OMe)-2 (1c)) with 1 equiv of sulfur (1/8 S(8)) results in the quantitative formation of the corresponding lithium arenethiolates [Li{SC(6)H(4)((R)-CH(Me)NMe(2))-2}](6) (3), [Li{SC(6)H(3)(CH(2)NMe(2))(2)-2,6}](6) (4), and [Li{SC(6)H(4)(CH(2)N(Me)CH(2)CH(2)OMe)-2}](2) (5). Alternatively, 3 can be prepared by reacting the corresponding arenethiol HSC(6)H(4)((R)-CH(Me)NMe(2))-2 (2) with (n)BuLi. X-ray crystal structures of lithium arenethiolates 3 and 4, reported in abbreviated form, show them to have hexanuclear prismatic and hexanuclear planar structures, respectively, that are unprecedented in lithium thiolate chemistry. The lithium arenethiolate [Li{SC(6)H(4)(CH(2)N(Me)CH(2)CH(2)OMe)-2}](2) (5) is dimeric in the solid state and in solution, and crystals of 5 are monoclinic, space group P2(1)/c, with a = 17.7963(9) ?, b = 8.1281(7) ?, c = 17.1340(10) ?, beta = 108.288(5) degrees, Z = 4, and final R = 0.047 for 4051 reflections with F > 4sigma(F). Hexameric 4 reacts with 1 equiv of lithium iodide and 2 equiv of tetrahydrofuran to form the dinuclear adduct [Li(2)(SAr)(I)(THF)(2)] (6). Crystals of 6 are monoclinic, space group P2(1)/c, with a = 13.0346(10) ?, b = 11.523(3) ?, c = 16.127(3) ?, beta = 94.682(10) degrees, Z = 4, and final R = 0.059 for 3190 reflections with F > 4sigma(F).     

Non-heme iron(II) complexes containing tripodal tetradentate nitrogen ligands and their application in alkane oxidation catalysis

A series of iron(II) bis(triflate) complexes containing tripodal tetradentate nitrogen ligands with pyridine and dimethylamine donors of the type [N(CH(2)Pyr)(3-n)()(CH(2)CH(2)NMe(2))(n)] [n = 0 (tpa, 1), n = 1 (iso-bpmen, 3), n = 2 (Me(4)-benpa, 4), n = 3 (Me(6)-tren, 5)] and the linear tetradentate ligand [(CH(2)Pyr)MeN(CH(2)CH(2))NMe(CH(2)Pyr), (bpmen, 2)] has been prepared. The preferred coordination geometry of these complexes in the solid state and in CH(2)Cl(2) solution changes from six- to five-coordinate in the order from 1 to 5. In acetonitrile, the triflate ligands of all complexes are readily displaced by acetonitrile ligands. The complex [Fe(1)(CH(3)CN)(2)](2+) is essentially low spin at room temperature, whereas ligands with fewer pyridine donors increase the preference for high-spin Fe(II). Both the number of pyridine donors and the spin state of the metal center strongly affect the intensity of a characteristic MLCT band around 400 nm. The catalytic properties of the complexes for the oxidation of alkanes have been evaluated, using cyclohexane as the substrate. Complexes containing ligands 1-3 are more active and selective catalysts, possibly operating via a metal-based oxidation mechanism, whereas complexes containing ligands 4 and 5 give rise to Fenton-type chemistry.     

Ruthenium complexes of thiocinnamaldehydes: synthesis, structure, and [4+2]-cycloaddition reactions

Ruthenium hydrogensulfido complexes [CpRu(P-P)(SH)] ((P-P)=Ph(2)PCH(2)PPh(2) (dppm), Ph(2)PC(2)H(4)PPh(2) (dppe)) were obtained from the corresponding chloro complexes by Cl/SH exchange. Condensation with a range of cinnamaldehydes gave thiocinnamaldehyde complexes [CpRu(P-P)(S=CH-CR(2)=CHR(1))]PF(6) (R(1)=C(6)H(4)X, R(2)=H, Me, X=H, OMe, NMe(2), Cl, NO(2)) as highly-colored crystalline compounds. The thiocinnamaldehyde complexes undergo [4+2]-cycloaddition reactions with vinyl ethers CH(2)=CHOR(3) (R(3)=Et, Bu) and styrenes H(2)C=CHC(6)H(4)Y (Y=H, Me, OMe, Cl, Br, NO(2)) to give complexes of 2,4,5-trisubstituted 3,4-dihydro-2H-thiopyrans as mixtures of two diastereoisomers. The rate of addition of para-substituted styrenes H(2)C=CHC(6)H(4)Y to [CpRu(dppm)(S=CH-CH=CHPh)]PF(6) increases in the series Y=NO(2), Br, Cl, H, Me, OMe, indicating that the cycloaddition is dominated by the HOMO(dienophile)-LUMO(diene) interaction. The strained dienophiles norbornadiene and norbornene also add, giving ruthenium complexes of 3-thia-tricyclo[6.2.1.0(2,7)]undeca-4,9-dienes and 3-thia-tricyclo[6.2.1.0(2,7)]undec-4-enes, respectively. Addition reactions with acrolein, methacrolein, methyl vinyl ketone, acrylic ester, or ethyl propiolate finally yielded ruthenium complexes of 3,4-disubstituted 3,4-dihydro-2H-thiopyrans and 4H-thiopyrans, respectively.     

Synthetic and structural studies of donor-functionalized alkoxy derivatives of gallium

The synthesis of a range of alkyl/chloro-gallium alkoxide and amido/alkoxide compounds was achieved via a series of protonolysis and alcoholysis steps. The initial reaction involved the synthesis of [Me(Cl)Ga{N(SiMe(3))(2)}](2) (1) via methyl group transfer from the reaction of GaCl(3) with two equivalents of LiN(SiMe(3))(2). Reaction of 1 with varying amounts of ROH resulted in the formation of [Me(Cl)Ga(OR)](2) (2, R = CH(2)CH(2)OMe; 3, CH(CH(3))CH(2)NMe(2)), [Me(Cl)Ga{N(SiMe(3))(2)}(μ(2)-OR)Ga(Cl)Me] (4, R = CH(2)CH(2)NMe(2)), or [MeGa(OR)(2)] (5, R = CH(CH(3))CH(2)NMe(2)). Compound 4 represents an intermediate in the formation of dimeric complexes, of the type [Me(Cl)Ga(OR)](2), when formed from compound [Me(Cl)Ga{N(SiMe(3))(2)}](2). A methylgallium amido/alkoxide complex [MeGa{N(SiMe(3))(2)}(OCH(2)CH(2)OMe)](2) (6) was isolated when 2 was further reacted with LiN(SiMe(3))(2). In addition, reaction of 2 with HO(t)Bu resulted in a simple alcohol/alkoxide exchange and formation of [Me(Cl)Ga(O(t)Bu)](2) (7). In contrast to the formation of 1, the in situ reaction of GaCl(3) with one equivalent of LiN(SiMe(3))(2) yielded [Cl(2)Ga{N(SiMe(3))(2)}](2) in low yield, where no methyl group transfer has occurred. Reaction of alcohol with [Cl(2)Ga{N(SiMe(3))(2)}](2) was then found to yield [Cl(2)Ga(OR)](2) (8, R = CH(2)CH(2)NMe(2)), and further reaction of 8 with LiN(SiMe(3))(2) yielded the gallium amido alkoxide complex, [ClGa{N(SiMe(3))(2)}(OR)](2) (9, R = CH(2)CH(2)NMe(2)), similar to 6. The structures of compounds 4, 5, 7, and 8 have been determined by single-crystal X-ray diffraction.     

Aerosol assisted chemical vapor deposition of In2O3 films from Me3In and donor functionalized alcohols

The reaction of Me3In and ROH (R = CH2CH2NMe2, CH(CH3)CH2NMe2, C(CH3)2CH2OMe, CH2CH2OMe) in toluene under aerosol assisted chemical vapor deposition (AACVD) conditions leads to the production of indium oxide thin films on glass. The indium oxide films were deposited at 550 degrees C and analyzed by scanning electron microscopy (SEM), X-ray powder diffraction, wavelength dispersive analysis of X-rays (WDX), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. This CVD technique offers a rapid, convenient route to In2O3, which presumably involves the in situ formation of dimethylindium alkoxides, of the type [Me2InOR]2. In order to identify compounds present in the aerosol mist, the solution-phase reaction between Me3In and ROH (R = CH2CH2NMe2, C(CH3)2CH2OMe, CH(CH3)CH2NMe2, CH(CH2NMe2)2) at room temperature in toluene was carried out. Dimeric indium alkoxides, of the type [Me2In(OR)]2, were isolated, and their structures were determined by X-ray crystallography.     

The metalla-Pinner reaction between Pt(IV)-bound nitriles and alkylated oxamic and oximic forms of hydroxamic acids

The nitrile ligands in the platinum(IV) complexes trans-[PtCl4(RCN)2] (R=Me, Et, CH2Ph) and cis/trans-[PtCl4(MeCN)(Me2SO)] are involved in a metalla-Pinner reaction with N-methylbenzohydroxamic acid (N-alkylated form of hydroxamic acid, hydroxamic form; F1), PhC(=O)N(Me)OH, to achieve the imino species [PtCl4[NH=C(R)ON(Me)C(=O)Ph]2 (1-3) and [PtCl4[NH=C(Me)ON(Me)C(=O)Ph](Me2SO)] (7), respectively. Treatment of trans-[PtCl4(RCN)2] (R=Me, Et) and cis/trans-[PtCl4(MeCN)(Me2SO)] with the O-alkylated form of a hydroxamic acid (hydroximic form), i.e. methyl 2,4,6-trimethylbenzohydroximate, 2,4,6-(Me3C6H2)C(OMe)=NOH (F2A), allows the isolation of [PtCl4[NH=C(R)ON=C(OMe)(2,4,6-Me3C6H2)]2] (5, 6) and [PtCl4[NH=C(Me)ON=C(OMe)(2,4,6-Me3C6H2)](Me2SO)] (8), correspondingly. In accord with the latter reaction, the coupling of nitriles in trans-[PtCl4(EtCN)2] with methyl benzohydroximate, PhC(OMe)=NOH (F2B), gives [PtCl4[NH=C(Et)ON=C(OMe)Ph]2] (4). The addition proceeds faster with the hydroximic F2, rather than with the hydroxamic form F1. The complexes 1-8 were characterized by C, H, N elemental analyses, FAB+ mass-spectrometry, IR, 1H and 13C[1H] NMR spectroscopies. The X-ray structure determinations have been performed for both hydroxamic and hydroximic complexes, i.e. 2 and 6, indicating that the imino ligands are mutually trans and they are in the E-configuration.     

Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.     

Reactivity of the inversely polarized phosphaalkenes RP=C(NMe2)2 (R = tBu, Me3Si, H) towards arylcarbene complexes [(CO)5M=C(oEt)Ar] (Ar= Ph, M = Cr, W; Ar = 2-MeC6H4, 2-MeOC6H4, M = W)

The reaction of the arylated Fischer carbene complexes [(CO)5M=C(OEt)Ar] (Ar=Ph; M = Cr, W; 2-MeC6H4; 2-MeOC6H; M = W) with the phosphaalkenes RP=C(NMe2), (R=tBu, SiMe3) afforded the novel phosphaalkene complexes [[RP=C(OEt)Ar]M(CO)5] in addition to the compounds [(RP=C(NMe2)2]M(CO)5]. Only in the case of the R = SiMe3 (E/Z) mixtures of the metathesis products were obtained. The bis(dimethylamino)methylene unit of the phosphaalkene precursor was incorporated in olefins of the type (Me2N)2C=C(OEt)(Ar). Treatment of [(CO)5W=C(OEt)(2-MeOC6H4)] with HP=C(NMe2)2 gave rise to the formation of an E/Z mixture of [[(Me2N)2CH-P=C(OEt)(2-MeOC6H4)]W(CO)5] the organophosphorus ligand of which formally results from a combination of the carbene ligand and the phosphanediyl [P-CH(NMe2)2]. The reactions reported here strongly depend on an inverse distribution of alpha-electron density in the phosphaalkene precursors (Pdelta Cdelta+), which renders these molecules powerfu] nucleophiles.     

Stereospecific synthesis of polysubstituted E-olefins by reaction of acyclic nitrones with free and platinum(II) coordinated organonitriles

Free nitriles NCCH2R (1a R = CO2Me, 1b R = SO2Ph, and 1c R = COPh) with an acidic alpha-methylene react with acyclic nitrones -O+N(Me)=C(H)R' (2a R' = 4-MeC6H4 and 2b R' = 2,4,6-Me3C6H2), in refluxing CH2Cl2, to afford stereoselectively the E-olefins (NC)(R)C=C(H)R' (3a-3c and 3a'-3c'), whereas, when coordinated at the platinum(II) trans-[PtCl2(NCCH2R)2] complexes (4a R = CO2Me and 4b R = Cl), they undergo cycloaddition to give the (oxadiazoline)-PtII complexes trans-[PtCl2{N=C(CH2R)ON(Me)C(H)R'}2] (R = CO2Me, Cl and R' = 4-MeC6H4, 2,4,6-Me3C6H2) (5a-5d). Upon heating in CH2Cl2, 5a affords the corresponding alkene 3a. The reactions are greatly accelerated when carried out under focused microwave irradiation, particularly in the solid phase (SiO2), without solvent, a substantial increase of the yields being also observed. The compounds were characterized by IR and 1H, 13C, and 195Pt NMR spectroscopies, FAB+-MS, elemental analyses and, in the cases of the alkene (NC)(CO2Me)C=C(H)(4-MeC6H4) 3a and of the oxadiazoline complex trans-[PtCl2{N=C(CH2Cl)ON(Me)C(H)(4-C6H4Me)}2] 5c, also by X-ray diffraction analyses.     

Zwitterionic bis(phenolate)amine lanthanide complexes for the ring-opening polymerisation of cyclic esters

The reaction of Sm{N(SiMe3)2}3 with the bis(phenol)amines H2O2N(R) (H2O2N(R) = RCH2CH2N(2-HO-3,5-C6H2(t)Bu2)2; R = OMe, NMe2 or Me) gave exclusively zwitterions Sm(O2N(R))(HO2N(R)). For R = OMe or NMe2 these were efficient catalysts for the ring-opening polymerisation of epsilon-caprolactone and D,L-lactide with a tendency to form cyclic esters; in contrast, no polymerisation was observed for R = Me.     

NH/pi interaction in a spin-crossover complex [FeII(HLMe)2](BPh4)2.2CH3CN (BPh4-=Tetraphenylborate; HLMe=2-Methylimidazol-4-yl-methylideneamino-2-ethylpyridine)

Three FeII complexes, [Fe(HLR)2](BPh4)2.solvent (R=H, Me, Ph), were synthesized, where BPh4-=tetraphenylborate and HLR=2-substituted-imidazol-4-yl-methylideneamino-2-ethylpyridine. The magnetic susceptibility measurements in 5-300 K revealed that [Fe(HLH)2](BPh4)2.H2O, [Fe(HLMe)2](BPh4)2.2CH3CN, and [Fe(HLPh)2](BPh4)2.CH3CN are low-spin (LS), spin-crossover (SC), and high-spin (HS) FeII complexes, respectively, indicating that the spin state can be effectively tuned by the bulkiness of the substituent. Complex shows a steep SC around 250 K, where it assumes a cyclic structure of {[Fe(HLMe)2]BPh4}2 constructed by four NH/pi bonds between the imidazole group and the phenyl ring of BPh4- in the HS state and a deformed structure with NH/pi bonds and linear CH3CN...HN hydrogen bonds at the terminals in the LS state.     

Reactions of tris(amino)phosphines with arylsulfonyl azides: product dependency on tris(amino)phosphine structure

The Staudinger reaction of N(CH2CH2NR)3P [R = Me (1), Pr (2)] with 1 equiv of N3SO2C6H4Me-4 gave the ionic phosphazides [N(CH2CH2NR)3PN][SO2C6H4Me-4] [R = Me (3), R = Pr (5a)], and the same reaction of 2 with N3SO2C6H2Me3-2,4,6 gave the corresponding aryl sulfinite 5b. On the other hand, the reaction of 1 with 0.5 equiv of N3SO2Ar (Ar = C6H4Me-4) furnished the novel ionic phosphazide [[N(CH2CH2NMe)3P]2(mu-N3)][SO2Ar] (6). Data that shed light on the mechanistic pathway leading to 3 were obtained by low temperature 31P NMR spectroscopy. A crystal and molecular structure analysis of the phosphazide sulfonate [N(CH2CH2NMe)3PN3][SO3C6H4Me-4] (4), obtained by atmospheric oxidation of 3, indicated an ionic structure, the cationic part of which is stabilized by a transannular P-N bond. A crystal and molecular structure analysis of 6 also indicated an ionic structure in which the cation features two untransannulated N(CH2CH2NMe)3P cages bridged by an azido group in an eta 1: mu: eta 1 fashion. The reaction of P(NMe2)3 with N3SO2Ar (Ar = C6H4Me-4) in a 1:0.5 molar ratio furnished [[(Me2N)3P]2(mu-N3)][SO2-Ar] (11) in quantitative yield. On the other hand, the same reaction involving a 1:1 molar ratio of P(NMe2)3 and N3SO2Ar produced a mixture of 11, [(Me2N)3PN3][SO2Ar] (12), and the iminophosphorane (Me2N)3P=NSO2Ar (10). In contrast, the bicyclic tris(amino)phosphines MeC(CH2NMe)3P (7) and O=P(CH2NMe)3P (8) reacted with N3SO2-Ar (Ar = C6H4Me-4) to give the iminophosphorane MeC(CH2NMe)3P=NSO2Ar (14) (structured by X-ray means) and O=P(CH2NMe)3P=NSO2Ar (16) via the intermediate phosphazides MeC(CH2NMe)3PN3SO2Ar (13) and O=P(CH2NMe)3PN3SO2Ar (15), respectively. The variety of products obtained from the reactions of arylsulfonyl azides with proazaphosphatranes (1 and 2), acyclic P(NMe2)3, bicyclic tris(amino)phosphines 7 and 8 are rationalized in terms of steric and basicity variations among the phosphorus reagents.     

Spectral, structural, and electrochemical properties of ruthenium porphyrin diaryl and aryl(alkoxycarbonyl) carbene complexes: influence of carbene substituents, porphyrin substituents, and trans-axial ligands

A wide variety of ruthenium porphyrin carbene complexes, including [Ru(tpfpp)(CR(1)R(2))] (CR(1)R(2) = C(p-C(6)H(4)Cl)(2) 1 b, C(p-C(6)H(4)Me)(2) 1 c, C(p-C(6)H(4)OMe)(2) 1 d, C(CO(2)Me)(2) 1 e, C(p-C(6)H(4)NO(2))CO(2)Me 1 f, C(p-C(6)H(4)OMe)CO(2)Me 1 g, C(CH==CHPh)CO(2)CH(2)(CH==CH)(2)CH(3) 1 h), [Ru(por)(CPh(2))] (por=tdcpp 2 a, 4-Br-tpp 2 b, 4-Cl-tpp 2 c, 4-F-tpp 2 d, tpp 2 e, ttp 2 f, 4-MeO-tpp 2 g, tmp 2 h, 3,4,5-MeO-tpp 2 i), [Ru(por)[C(Ph)CO(2)Et]] (por=tdcpp 2 j, tmp 2 k), [Ru(tpfpp)(CPh(2))(L)] (L = MeOH 3 a, EtSH 3 b, Et(2)S 3 c, MeIm 3 d, OPPh(3) 3 e, py 3 f), and [Ru(tpfpp)[C(Ph)CO(2)R](MeOH)] (R = CH(2)CH==CH(2) 4 a, Me 4 b, Et 4 c), were prepared from the reactions of [Ru(por)(CO)] with diazo compounds N(2)CR(1)R(2) in dichloromethane and, for 3 and 4, by further treatment with reagents L. A similar reaction of [Os(tpfpp)(CO)] with N(2)CPh(2) in dichloromethane followed by treatment with MeIm gave [Os(tpfpp)(CPh(2))(MeIm)] (3 d-Os). All these complexes were characterized by (1)H NMR, (13)C NMR, and UV/Vis spectroscopy, mass spectrometry, and elemental analyses. X-ray crystal structure determinations of 1 d, 2 a,i, 3 a, b, d, e, 4 a-c, and 3 d-Os revealed Ru==C distances of 1.806(3)-1.876(3) A and an Os==C distance of 1.902(3) A. The structure of 1 d in the solid state features a unique "bridging" carbene ligand, which results in the formation of a one-dimensional coordination polymer. Cyclic voltammograms of 1 a-c, g, 2 a-d, g-k, 3 b-d, 4 a, b, and 3 d-Os show a reversible oxidation couple with E(1/2) values in the range of 0.06-0.65 V (vs Cp(2)Fe(+/0)) that is attributable to a metal-centered oxidation. The influence of carbene substituents, porphyrin substituents, and trans-ligands on the Ru==C bond was examined through comparison of the chemical shifts of the pyrrolic protons in the porphyrin macrocycles ((1)H NMR) and the M==C carbon atoms ((13)C NMR), the potentials of the metal-centered oxidation couples, and the Ru==C distances among the various ruthenium porphyrin carbene complexes. A direct comparison among iron, ruthenium, and osmium porphyrin carbene complexes is made.     

Cationic diiron and diruthenium μ-allenyl complexes: synthesis, X-ray structures and cyclization reactions with ethyldiazoacetate/amine affording unprecedented butenolide- and furaniminium-substituted bridging carbene ligands

The novel cationic diiron μ-allenyl complexes [Fe(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(2)(α,β)-C(α)(H)=C(β)=C(γ)(R)(2)}](+) (R = Me, 4a; R = Ph, 4b) have been obtained in good yields by a two-step reaction starting from [Fe(2)Cp(2)(CO)(4)]. The solid state structures of [4a][CF(3)SO(3)] and of the diruthenium analogues [Ru(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(2)(α,β)-C(α)(H)=C(β)=C(γ)(R)(2)}][BPh(4)] (R = Me, [2a][BPh(4)]; R = Ph, [2c][BPh(4)]) have been ascertained by X-ray diffraction studies. The reactions of 2c and 4a with Br?nsted bases result in formation of the μ-allenylidene compound [Ru(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(1)-C(α)=C(β)=C(γ)(Ph)(2)}] (5) and of the dimetallacyclopentenone [Fe(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)=C(β)(C(γ)(Me)CH(2))C(=O)}] (6), respectively. The nitrile adducts [Ru(2)Cp(2)(CO)(NCMe)(μ-CO){μ-η(1):η(2)-C(α)(H)=C(β)=C(γ)(R)(2)}](+) (R = Me, 7a; R = Ph, 7b), prepared by treatment of 2a,c with MeCN/Me(3)NO, react with N(2)CHCO(2)Et/NEt(3) at room temperature, affording the butenolide-substituted carbene complexes [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(R)(2)OC(=O)C[upper bond 1 end](H)] (R = Me, 10a; R = Ph, 10b). The intermediate cationic compound [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (9) has been detected in the course of the reaction leading to 10a. The addition of N(2)CHCO(2)Et/NHEt(2) to 7a gives the 2-furaniminium-carbene [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (11). The X-ray structures of 10a, 10b and [11][BF(4)] have been determined. The reactions of 4a,b with MeCN/Me(3)NO result in prevalent decomposition to mononuclear iron species.     

Monovalent iron in a sulfur-rich environment

A series of low-coordinate, paramagnetic iron complexes in a tris(thioether) ligand environment have been prepared. Reduction of ferrous {[PhTt(tBu)]FeCl}2 [1; PhTt(tBu) = phenyltris((tert-butylthio)methyl)borate] with KC8 in the presence of PR3(R = Me or Et) yields the high-spin, monovalent iron phosphine complexes [PhTt(tBu)]Fe(PR3) (2). These complexes provide entry into other low-valent derivatives via ligand substitution. Carbonylation led to smooth formation of the low-spin dicarbonyl [PhTt(tBu)]Fe(CO)2 (3). Alternatively, replacement of PR 3 with diphenylacetylene produced the high-spin alkyne complex [PhTt(tBu)]Fe(PhCCPh) (4). Lastly, 2 equiv of adamantyl azide undergoes a 3 + 2 cycloaddition at 2, yielding high-spin dialkyltetraazadiene complex 5.     

Tripodal bis(imidazole) thioether copper(I) complexes: mimics of the Cu(M) site of copper hydroxylase enzymes

Tripodal bis(imidazole) thioether ligands, (N-methyl-4,5-diphenyl-2-imidazolyl)2C(OR)C(CH3)2SR' (BIT(OR,SR'); R = H, CH3; R' = CH3, C(CH3)3, C(C6H5)3), have been prepared, offering the same N2S donor atom set as the CuM binding site of the hydroxylase enzymes, dopamine beta hydroxylase and peptidylglycine hydroxylating monooxygenase. Isolable copper(I) complexes of the type [(BIT(OR,SMe))Cu(CO)]PF6 (3a and 3b) are produced in reactions of the respective tripodal ligands 1a (R = H) and 1b (R = Me) with [Cu(CH3CN)4]PF6 in CH2Cl2 under CO (1 atm); the pyramidal structure of 3a has been determined crystallographically. The infrared (IR) nu(CO)'s of 3a and 3b (L = CO) are comparable to those of the Cu(M)-carbonylated enzymes, indicating similar electronic character at the copper centers. The reaction of [(BIT(OH,SMe))Cu(CH3CN)]PF6 (2a) with dioxygen produces [(BIT(O,SOMe))2Cu2(DMF)2](PF6)2 (4), whose X-ray structure revealed the presence of bridging BIT-alkoxo ligands and terminal -SOMe groups. In contrast, oxygenation of 2b (R = Me) affords crystallographically defined [(BIT(OMe,SMe))2Cu2(mu-OH)2](OTf)2 (5), in which the copper centers are oxygenated without accompanying sulfur oxidation. Complex 5 in DMF is transformed into five-coordinate, mononuclear [CuII(BIT(OMe,SMe))(DMF)2](PF6)2 (6). The sterically hindered BIT(OR,SR') ligands 9 and 10 (R' = t-Bu; R = H, Me) and 11 and 12 (R' = CPh3; R = H, Me) were also prepared and examined for copper coordination/oxygenation. Oxygenation of copper(I) complex 13b derived from the BIT(OMe,SBu-t) ligand is slow, relative to 2b, producing a mixture of (BIT(OMe,SBu-t))2Cu2(mu-OH)2-type complexes 14b and 15b in which the -SBu-t group is uncoordinated; one of these complexes (15b) has been ortho-oxygenated on a neighboring aryl group according to the X-ray analysis and characterization of the free ligand. Oxygenation of the copper(I) complex derived from BIT(OMe,SCPh3) ligand 12 produces a novel dinuclear disulfide complex, [(BIT(OMe,S)2Cu2(mu-OH)2](PF6)2 (17), which is structurally characterized. Reactivity studies under anaerobic conditions in the presence of t-BuNC indicate that 17 is the result of copper(I)-induced detritylation followed by oxygenation of a highly reactive copper(I)-thiolate complex.     

Merging organometallic chemistry with polyoxometalate chemistry

A series of polyoxomolybdate-incorporated organometallic complexes has been obtained by reaction of [MBr(CO)5] or solvated M(CO)3+ ions (M = Mn or Br) with (nBu4N)2[Mo2O7] in methanol, sometimes in the presence of triols of the type RC(CH2OH)3 (R = Me or CH2OH). Their molecular structures are related to those of previously described polyoxoalkoxomolybdates through the formal replacement of fac-MoO2(OR)+ units by topologically equivalent fac-M(CO)3+ units. Representative pairs of structurally related clusters include [Mo2O6(OMe)4-Re(CO)32]2- and [Mo4O10(OMe)6]2-, [Mo2O4MeC(CH2O)32Mn(CO)3]- and [Mo3O6(OMe)MeC(CH2O)32]-, [Mo2O4HOCH2C(CH2O)32Mn(CO)32] and [Mo4O8(OEt)2MeC(CH2O)32], [Mo6O16(OMe)2MeC(CH2O)32-Mn(CO)32]2- and [Mo8O20(OMe)4-MeC(CH2O)32]2-. Although the frameworks of the majority of derivatives are based on tetranuclear units which display the common rhomb-like structure, the alternative cubane-type arrangement is observed in [Mo2O5(OMe)5M(CO)32]-.