Osmabenzenes from the reactions of a dicationic osmabenzyne complex

Treatment of the osmabenzyne Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)Cl(2)(PPh(3))(2) (1) with 2,2'-bipyridine (bipy) and thallium triflate (TlOTf) produces the thermally stable dicationic osmabenzyne [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) (2). The dicationic osmabenzyne 2 reacts with ROH (R = H, Me) to give osmabenzene complexes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf, in which the metallabenzene ring deviates significantly from planarity. In contrast, reaction of the dicationic complex 2 with NaBH(4) produces a cyclopentadienyl complex, presumably through the osmabenzene intermediate [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf. The higher thermal stability of [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf relative to [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf can be related to the stabilization effect of the OR groups on the metallacycle. A theoretical study shows that conversion of the dicationic osmabenzyne complex [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) to a carbene complex by reductive elimination is thermodynamically unfavorable. The theoretical study also suggests that the nonplanarity of the osmabenzenes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf is mainly due to electronic reasons.     

Generation and coupling of [Mn(dmpe)2(C triple bond CR)(C triple bond C)]* radicals producing redox-active C4-bridged rigid-rod complexes

The symmetric d(5) trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)] (R = Me, 1 a; Et, 1 b; Ph, 1 c) (dmpe = 1,2-bis(dimethylphosphino)ethane) have been prepared by the reaction of [Mn(dmpe)(2)Br(2)] with two equivalents of the corresponding acetylide LiC triple bond CSiR(3). The reactions of species 1 with [Cp(2)Fe][PF(6)] yield the corresponding d(4) complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)][PF(6)] (R = Me, 2 a; Et, 2 b; Ph, 2 c). These complexes react with NBu(4)F (TBAF) at -10 degrees C to give the desilylated parent acetylide compound [Mn(dmpe)(2)(C triple bond CH)(2)][PF(6)] (6), which is stable only in solution at below 0 degrees C. The asymmetrically substituted trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(C triple bond CH)][PF(6)] (R = Me, 7 a; Et, 7 b) related to 6 have been prepared by the reaction of the vinylidene compounds [Mn(dmpe)(2)(C triple bond CSiR(3))(C=CH(2))] (R = Me, 5 a; Et, 5 b) with two equivalents of [Cp(2)Fe][PF(6)] and one equivalent of quinuclidine. The conversion of [Mn(C(5)H(4)Me)(dmpe)I] with Me(3)SiC triple bond CSnMe(3) and dmpe afforded the trans-iodide-alkynyl d(5) complex [Mn(dmpe)(2)(C triple bond CSiMe(3))I] (9). Complex 9 proved to be unstable with regard to ligand disproportionation reactions and could therefore not be oxidized to a unique Mn(III) product, which prevented its further use in acetylide coupling reactions. Compounds 2 react at room temperature with one equivalent of TBAF to form the mixed-valent species [[Mn(dmpe)(2)(C triple bond CH)](2)(micro-C(4))][PF(6)] (11) by C-C coupling of [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] radicals generated by deprotonation of 6. In a similar way, the mixed-valent complex [[Mn(dmpe)(2)(C triple bond CSiMe(3))](2)(micro-C(4))][PF(6)] [12](+) is obtained by the reaction of 7 a with one equivalent of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The relatively long-lived radical intermediate [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] could be trapped as the Mn(I) complex [Mn(dmpe)(2)(C triple bond CH)(triple bond C-CO(2))] (14) by addition of an excess of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to the reaction mixtures of species 2 and TBAF. The neutral dinuclear Mn(II)/Mn(II) compounds [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))] (R = H, 11; R = SiMe(3), 12) are produced by the reduction of [11](+) and [12](+), respectively, with [FeCp(C(6)Me(6))]. [11](+) and [12](+) can also be oxidized with [Cp(2)Fe][PF(6)] to produce the dicationic Mn(III)/Mn(III) species [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))][PF(6)](2) (R = H, [11](2+); R = SiMe(3), [12](2+)). Both redox processes are fully reversible. The dinuclear compounds have been characterized by NMR, IR, UV/Vis, and Raman spectroscopies, CV, and magnetic susceptibilities, as well as elemental analyses. X-ray diffraction studies have been performed on complexes 4 b, 7 b, 9, [12](+), [12](2+), and 14.     

Aluminacyclopropene: syntheses, characterization, and reactivity toward terminal alkynes

Reactions of LAl with ethyne, mono- and disubstituted alkynes, and diyne to aluminacyclopropene LAl[eta2-C2(R1)(R2)] ((L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3); R1 = R2 = H, (1); R1 = H, R2 = Ph, (2); R1 = R2 = Me, (3); R1 = SiMe3, R2 = C[triple bond]CSiMe3, (4)) are reported. Compounds 1 and 2 were obtained in equimolar quantities of the starting materials at low temperature. The amount of C2H2 was controlled by removing an excess of C2H2 in the range from -78 to -50 degrees C. Compound 4 can be alternatively prepared by the substitution reaction of LAl[eta2-C2(SiMe3)2] with Me3SiC[triple bond]CC[triple bond]CSiMe3 or by the reductive coupling reaction of LAlI2 with potassium in the presence of Me3SiC[triple bond]CC[triple bond]CSiMe3. The reaction of LAl with excess C2H2 and PhC[triple bond]CH (<1:2) afforded the respective alkenylalkynylaluminum compounds LAl(CH=CH2)(C[triple bond]CH) (5) and LAl(CH=CHPh)(C[triple bond]CPh) (6). The reaction of LAl(eta2-C2Ph2) with C2H2 and PhC[triple bond]CH yielded LAl(CPh=CHPh)(C[triple bond]CH) (7) and LAl(CPh=CHPh)(C[triple bond]CPh) (8), respectively. Rationally, the formation of 5 (or 6) may proceed through the corresponding precursor 1 (or 2). The theoretical studies based on DFT calculations show that an interaction between the Al(I) center and the C[triple bond]C unit needs almost no activation energy. Within the AlC2 ring the computational Al-C bond order of ca. 1 suggests an Al-C sigma bond and therefore less pi electron delocalization over the AlC2 ring. The computed Al-eta2-C2 bond dissociation energies (155-82.6 kJ/mol) indicate a remarkable reactivity of aluminacyclopropene species. Finally, the 1H NMR spectroscopy monitored reaction of LAl(eta2-C2Ph2) and PhC[triple bond]CH in toluene-d8 may reveal an acetylenic hydrogen migration process.     

C-C coupling reactions in the coordination sphere of rhodium(I) and rhodium(III): New routes for the di- and trimerization of terminal alkynes

The alkynyl(vinylidene)rhodium(I) complexes trans-[Rh(C[triple bond, length as m-dash]CR)(=C=CHR)(PiPr3)2] 2, 5, 6 react with CO by migratory insertion to give stereoselectively the butenynyl compounds trans-[Rh{eta1-(Z)-C(=CHR)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-7-9, of which (Z)-7 (R=Ph) and (Z)-8 (R=tBu) rearrange upon heating or UV irradiation to the (E) isomers. Similarly, trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CPh}(CO)(PiPr3)2] 12 and trans-[Rh{eta1-(Z)-C(=CHCO2Me)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-15, (Z)-16 have been prepared. At room temperature, the corresponding "non-substituted" derivative trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CH}(CO)(PiPr3)2] 18 is in equilibrium with the butatrienyl isomer trans-[Rh(eta1-CH=]C=C=CH2)(CO)(PiPr3)2] 19 that rearranges photochemically to the alkynyl complex trans-[Rh(C[triple bond, length as m-dash]CCH=CH2)(CO)(PiPr3)2] 20. Reactions of (Z)-7, (E)-7, (Z)-8 and (E)-8 with carboxylic acids R'CO2H (R'=CH3, CF3) yield either the butenyne (Z)- and/or (E)-RC[triple bond, length as m-dash]CCH=CHR or a mixture of the butenyne and the isomeric butatriene, the ratio of which depends on both R and R'. Treatment of 2 (R=Ph) with HCl at -40 degrees C affords five-coordinate [RhCl(C[triple bond, length as m-dash]CPh){(Z)-CH=CHPh}(PiPr3)2] 23, which at room temperature reacts by C-C coupling to give trans-[RhCl{eta2-(Z)-PhC[triple bond, length as m-dash]CCH=CHPh}(PiPr3)2](Z)-21. The related compound trans-[RhCl(eta2-HC[triple bond, length as m-dash]CCH=CH2)(PiPr3)2] 27, prepared from trans-[Rh(C[triple bond, length as m-dash]CH)(=C=CH2)(PiPr3)2] 17 and HCl, rearranges to the vinylvinylidene isomer trans-[RhCl(=C=CHCH=CH2)(PiPr3)2] 28. While stepwise reaction of 2with CF3CO2H yields, via alkynyl(vinyl)rhodium(III) intermediates (Z)-29 and (E)-29, the alkyne complexes trans-[Rh(kappa1-O2CCF3)(eta2-PhC[triple bond, length as m-dash]CCH=CHPh)(PiPr3)2](Z)-30 and (E)-30, from 2 and CH3CO2H the acetato derivative [Rh(kappa2-O2CCH3)(PiPr3)2] 33 and (Z)-PhC[triple bond, length as m-dash]CCH=]CHPh are obtained. From 6 (R=CO2Me) and HCl or HC[triple bond, length as m-dash]CCO2Me the chelate complexes [RhX(C[triple bond, length as m-dash]CCO2Me){kappa2(C,O)-CH=CHC(OMe)=O}(PiPr3)2] 34 (X=Cl) and 35 (X=C[triple bond, length as m-dash]CCO2Me) have been prepared. In contrast to the reactions of [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE)(CH=CHE)(PiPr3)2] 37(E=CO2Me) with chloride sources which give, via intramolecular C-C coupling, four-coordinate trans-[RhCl{eta2-(E)-EC[triple bond, length as m-dash]CCH=CHE}(PiPr3)2](E)-36, treatment of 37with HC[triple bond, length as m-dash]CE affords, via insertion of the alkyne into the rhodium-vinyl bond, six-coordinate [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE){eta1-(E,E)-C(=CHE)CH=CHE}(PiPr3)2] 38. The latter reacts with MgCl2 to yield trans-[RhCl{eta2-(E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE}(PiPr3)2] 39, which, in the presence of CO, generates the substituted hexadienyne (E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE 40.     

Acetylide-bridged organometallic oligomers via the photochemical metathesis of methyl-iron(II) complexes

The acetylido methyl iron(II) complexes, cis/trans-[Fe(dmpe)(2)(C[triple bond]CR)(CH(3))] (1) and trans-[Fe(depe)(2)(C[triple bond]CR)(CH(3))] (2) (dmpe = 1,2-dimethylphoshinoethane; depe = 1,2-diethylphosphinoethane), were synthesized by transmetalation from the corresponding alkyl halide complexes. Acetylido methyl iron(II) complexes were also formed by transmetalation from the chloride complexes, trans-[Fe(dmpe)(2)(C[triple bond]CR)(Cl)] or trans-[Fe(depe)(2)(C[triple bond]CR)(Cl)]. The structure of trans-[Fe(dmpe)(2)(C[triple bond]CC(6)H(5))(CH(3))] (1a) was determined by single-crystal X-ray diffraction. The methyl acetylido iron complexes, [Fe(dmpe)(2)(C[triple bond]CR)(CH(3))] (1), are thermally stable in the presence of acetylenes; however, under UV irradiation, methane is lost with the formation of a metal bisacetylide. Photochemical metathesis of cis- or trans-[Fe(dmpe)(2)(CH(3))(C[triple bond]CR)] (R = C(6)H(5) (1a), 4-C(6)H(4)OCH(3) (1b)) with terminal acetylenes was used to selectively synthesize unsymmetrically substituted iron(II) bisacetylide complexes of the type trans-[Fe(dmpe)(2)(C[triple bond]CR)(C[triple bond]CR')] [R = Ph, R' = Ph (6a), 4-CH(3)OC(6)H(4) (6b), (t)()Bu (6c), Si(CH(3))(3) (6d), (CH(2))(4)C[triple bond]CH (6e); R = 4-CH(3)OC(6)H(4), R' = 4-CH(3)OC(6)H(4), (6g), (t)()Bu (6h), (CH(2))(4)C[triple bond]CH (6i), adamantyl (6j)]. The structure of the unsymmetrical iron(II) bisacetylide complex trans-[Fe(dmpe)(2)(C[triple bond]CC(6)H(5))(C[triple bond]CC(6)H(4)OCH(3))] (6b) was determined by single-crystal X-ray diffraction. The photochemical metathesis of the bis-acetylene, 1,7-octadiyne, with trans-[Fe(dmpe)(2)(CH(3))(C[triple bond]CPh)] (1a), was utilized to synthesize the bridged binuclear species trans,trans-[(C(6)H(5)C[triple bond]C)Fe(dmpe)(2)(mu-C[triple bond]C(CH(2))(4)C[triple bond]C)Fe(dmpe)(2)(C[triple bond]CC(6)H(5))] (11). The trinuclear species trans,trans,trans-[(C(6)H(5)C[triple bond]C)Fe(dmpe)(2)(mu-C[triple bond]C(CH(2))(4)C[triple bond]C)Fe(dmpe)(2)(mu-C[triple bond]C(CH(2))(4)C[triple bond]C)Fe(dmpe)(2)(C[triple bond]CC(6)H(5))] (12) was synthesized by the photochemical reaction of Fe(dmpe)(2)(C[triple bond]CPh)(C[triple bond]C(CH(2))(4)C[triple bond]CH) (6e) with Fe(dmpe)(2)(CH(3))(2). Extended irradiation of the bisacetylide complexes with phenylacetylene resulted in insertion of the terminal alkyne into one of the metal acetylide bonds to give acetylide butenyne complexes. The structure of the acetylide butenyne complex, trans-[Fe(dmpe)(2)(C[triple bond]CC(6)H(4)OCH(3))(eta(1)-C(C(6)H(5))=CH(C[triple bond]CC(6)H(4)OCH(3)))] (9a) was determined by single-crystal X-ray diffraction.     

Sigma-organyl complexes of ruthenium and osmium supported by a mixed-donor ligand

A series of vinyl, aryl, acetylide and silyl complexes [Ru(R)(kappa2-MI)(CO)(PPh3)2] (R = CH=CH2, CH=CHPh, CH=CHC6H4CH3-4, CH=CH(t)Bu, CH=2OH, C(C triple bond CPh)=CHPh, C6H5, C triple bond CPh, SiMe2OEt; MI = 1-methylimidazole-2-thiolate) were prepared from either [Ru(R)Cl(CO)(PPh3)2] or [Ru(R)Cl(CO)(BTD)(PPh3)2](BTD = 2,1,3-benzothiadiazole) by reaction with the nitrogen-sulfur mixed-donor ligand, 1-methyl-2-mercaptoimidazole (HMI), in the presence of base. In the same manner, [Os(CH=CHPh)(kappa2-MI)(CO)(PPh3)2] was prepared from [Os(CH=CHPh)(CO)Cl(BTD)(PPh3)2]. The in situ hydroruthenation of 1-ethynylcyclohexan-1-ol by [RuH(CO)Cl(BTD)(PPh3)2] and subsequent addition of the HMI ligand and excess sodium methoxide yielded the dehydrated 1,3-dienyl complex [Ru(CH=CHC6H9)(kappa2-MI)(CO)(PPh3)2]. Dehydration of the complex [Ru(CH=CHCPh2OH)(kappa2-MI)(CO)(PPh3)2] with HBF4 yielded the vinyl carbene [Ru(=CHCH=CPh2)(kappa2-MI)(CO)(PPh3)2]BF4. The hydride complexes [MH(kappa2-MI)(CO)(PPh3)2](M = Ru, Os) were obtained from the reaction of HMI and KOH with [RuHCl(CO)(PPh3)3] and [OsHCl(CO)(BTD)(PPh3)2], respectively. Reaction of [Ru(CH=CHC6H4CH3-4)(kappa2-MI)(CO)(PPh3)2] with excess HC triple bond CPh leads to isolation of the acetylide complex [Ru(C triple bond CPh)(kappa2-MI)(CO)(PPh3)2], which is also accessible by direct reaction of [Ru(C triple bond CPh)Cl(CO)(BTD)(PPh3)2] with 1-methyl-2-mercaptoimidazole and NaOMe. The thiocarbonyl complex [Ru(CPh = CHPh)Cl(CS)(PPh3)2] reacted with HMI and NaOMe without migration to yield [Ru(CPh= CHPh)(kappa2-MI)(CS)(PPh3)2], while treatment of [Ru(CH=CHPh)Cl(CO)2(PPh3)2] with HMI yielded the monodentate acyl product [Ru{eta(1)-C(=O)CH=CHPh}(kappa2-MI)(CO)(PPh3)2]. The single-crystal X-ray structures of five complexes bearing vinyl, aryl, acetylide and dienyl functionality are reported.     

Syntheses, structures, and surface aromaticity of the new carbaalane [(AlH)(6)(AlNMe(3))(2)(CCH(2)R)(6)] (R = Ph, CH(2)SiMe(3)) and a stepwise functionalization of the inner and outer sphere of the cluster

The reaction of the acetylene RC triple bond CH (R = Ph, CH(2)SiMe(3)) with an excess of AlH(3).NMe(3) in boiling toluene leads to the carbaalane [(AlH)(6)(AlNMe(3))(2)(CCH(2)R)(6)] (R = Ph 1, CH(2)SiMe(3) 2) in good yield. Treatment of 2 with BCl(3) under varying conditions gives the chlorinated products [(AlCl)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] 3 and [(AlCl)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(2)Cl)(6)] 4, respectively. The latter clearly demonstrates that the cluster can be stepwise functionalized within the inner and outer sphere. The X-ray single-crystal structures of 1, 2, and 4 have been determined. All compounds have in common that the central core consists of a cluster having eight aluminum and six carbon atoms. The bonding properties in this cluster are described as a new manifestation of three-dimensional surface aromaticity. Each Al(4)C fragment of the cube is formed by four bonds with three electron pairs, thus leading to a strong delocalization of the electrons. A phenomenological modeling using a three-dimensional Hückel scheme with fitted parameters to reproduce the energies from ab initio calculations revealed that the orbital scheme localized at one Al(4)C fragment possesses an orbital sextet with a large HOMO-LUMO gap. This is in line with the criteria of aromaticity. The idea of aromaticity was sustained also by qualitative valence bond reasons enumerating the different resonance structures by means of graph theoretical methods.     

Dehydration reaction of hydroxyl substituted alkenes and alkynes on the Ru(2)S(2) complex

A variety of inter- and intramolecular dehydration was found in the reactions of [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)(mu-S(2))](CF(3)SO(3))(4) (1) with hydroxyl substituted alkenes and alkynes. Treatment of 1 with allyl alcohol gave a C(3)S(2) five-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)CH(2)CH(OCH(2)CH=CH(2))S]](CF(3)SO(3))(4) (2), via C-S bond formation after C-H bond activation and intermolecular dehydration. On the other hand, intramolecular dehydration was observed in the reaction of 1 with 3-buten-1-ol giving a C(4)S(2) six-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2) [mu-SCH(2)CH=CHCH(2)S]](CF(3)SO(3))(4) (3). Complex 1 reacts with 2-propyn-1-ol or 2-butyn-1-ol to give homocoupling products, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCR=CHCH(OCH(2)C triple bond CR)S]](CF(3)SO(3))(4) (4: R = H, 5: R = CH(3)), via intermolecular dehydration. In the reaction with 2-propyn-1-ol, the intermediate complex having a hydroxyl group, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OH)S]](CF(3)SO(3))(4) (6), was isolated, which further reacted with 2-propyn-1-ol and 2-butyn-1-ol to give 4 and a cross-coupling product, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OCH(2)C triple bond CCH(3))S]](CF(3)SO(3))(4) (7), respectively. The reaction of 1 with diols, (HO)CHRC triple bond CCHR(OH), gave furyl complexes, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SSC=CROCR=CH]](CF(3)SO(3))(3) (8: R = H, 9: R = CH(3)) via intramolecular elimination of a H(2)O molecule and a H(+). Even though (HO)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OH) does not have any propargylic C-H bond, it also reacts with 1 to give [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)C(=CH(2))C(=C=C(CH(3))(2))]S](CF(3)SO(3))(4) (10). In addition, the reaction of 1 with (CH(3)O)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OCH(3)) gives [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(2)][mu-S=C(C(CH(3))(2)OCH(3))C=CC(CH(3))CH(2)S][Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)]](CF(3)SO(3))(4) (11), in which one molecule of CH(3)OH is eliminated, and the S-S bond is cleaved.     

Stabilizing Heterobimetallic Complexes Containing Unsupported Ti-M Bonds (M = Fe, Ru, Co): The Nature of Ti-M Donor-Acceptor Bonds

The stabilization of unsupported Ti-M (M = Fe, Ru, Co) heterodinuclear complexes has been achieved by use of amidotitanium building blocks containing tripodal amido ligands. Salt metathesis of H(3)CC(CH(2)NSiMe(3))(3)TiX (1) and C(6)H(5)C(CH(2)NSiMe(3))(3)TiX (2) as well as HC{SiMe(2)N(4-CH(3)C(6)H(4))}(3)TiX (3) (X = Cl, a; Br, b) with K[M(CO)(2)Cp] (M = Fe, Ru) and Na[Co(CO)(3)(PR(3))] (R = Ph, Tol) gave the corresponding stable heterobimetallic complexes of which H(3)CC(CH(2)NSiMe(3))(3)Ti-M(CO)(2)Cp (M = Fe, 6; Ru, 7) and HC{SiMe(2)N(4-CH(3)C(6)H(4))}(3)Ti-M(CO)(2)Cp (M = Fe, 12; Ru, 13) have been characterized by X-ray crystallography. 6: monoclinic, P2(1)/n, a = 15.496(3) ?, b = 12.983(3) ?, c = 29.219(3) ?, beta = 104.52(2) degrees, Z = 8, V = 5690.71 ?(3), R = 0.070. 7: monoclinic, P2(1)/c, a = 12.977(3) ?, b = 12.084(3) ?, c = 18.217(3) ?, beta = 91.33(2) degrees, Z = 4, V = 2855.91 ?(3), R = 0.048. 12: monoclinic, I2/c, a = 24.660(4) ?, b = 15.452(3) ?, c = 20.631(4) ?, beta = 103.64(3) degrees, Z = 8, V = 7639.65 ?(3), R = 0.079. 13: monoclinic, I2/c, a = 24.473(3) ?, b = 15.417(3) ?, c = 20.783(4) ?, beta = 104.20(2) degrees, Z = 8, V = 7601.84 ?(3), R = 0.066. (1)H- and (13)C-NMR studies in solution indicate free internal rotation of the molecular fragments around the Ti-M bonds. Fenske-Hall calculations performed on the idealized system HC(CH(2)NH)(3)Ti-Fe(CO)(2)Cp (6x) have revealed a significant degree of pi-donor-acceptor interaction between the two metal fragments reinforcing the Ti-Fe sigma-bond. Due to the availability of energetically low-lying pi-acceptor orbitals at the Ti center this partial multiple bonding is more pronounced that in the tin analogue HC(CH(2)NH)(3)Sn-Fe(CO)(2)Cp (15x) in which an N-Sn sigma-orbital may act as pi-acceptor orbital.     

Syntheses of chromium pentacarbonyl derivatives of arsenic(V) and antimony(V). contrasting chemical reactivity with organic halogen derivatives

We have synthesized a new series of chromium-group 15 dihydride and hydride complexes [H(2)As(Cr(CO)(5))(2)](-) (1) and [HE(Cr(CO)(5))(3)](2)(-) (E = As, 2a; E = Sb, 2b), which represent the first examples of group 6 complexes containing E-H fragments. The contrasting chemical reactivity of 2a and 2b with organic halogen derivatives is demonstrated. The reaction of 2a with RBr (R = PhCH(2), HC triple bond CCH(2)) produces the RX addition products [(R)(Br)As(Cr(CO)(5))(2)](-) (R = PhCH(2), 3; R = C(3)H(3), 4), while the treatment of 2b with RX (RX = PhCH(2)Br or HC triple bond CCH(2)Br, CH(3)(CH(2))(5)C(O)Cl) forms the halo-substituted complexes [XSb(Cr(CO)(5))(3)](2-) (X = Br, 5; X = Cl, 6). Moreover, the dihaloantimony complexes [XX'Sb(Cr(CO)(5))(2)](-) can be obtained from the reaction of 2b with the appropriate organic halides. In this study, a series of organoarsenic and antimony chromium carbonyl complexes have been synthesized and structurally characterized and the role of the main group on the formation of the resultant complexes is also discussed.     

C-H and P-C(Ph) activation competitive processes caused by interaction with the solvate [cis-Pt(C6F5)2(thf)2

The study of the reaction between the ethylene [Pt(eta-H2C = CH2)(PPh3)2] or alkyne [Pt(eta2-HC [triple bond] CR)(PPh3)2] (R = SiMe3 1, Bu(t) 2) complexes with [cis-Pt(C6F5)2(thf)2] (thf = tetrahydrofuran) has enabled us to observe the existence of competitive processes between the activation of a P-C(Ph) bond on the PPh3 ligand, to give the binuclear derivative [cis-(C6F5)2Pt(mu-Ph)(mu-PPh2)Pt(PPh3)] 3, and the activation of a C-H bond of the unsaturated group, to give the corresponding (mu-hydride)(mu-vinyl) [cis, cis-(PPh3)2Pt(mu-H)(mu-1kappaC(alpha):eta2-CH = CH2)Pt(C6F5)2] 4 or (mu-hydride)(mu-alkynyl) [cis,cis-(PPh3)2Pt(mu-H)(mu-1kappaC(alpha):eta2-C [triple bond]CR)Pt(C6F5)2] (R = SiMe3 5, Bu(t) 6) compounds, respectively. The monitoring of these reactions by NMR spectroscopy has allowed us to detect several intermediates, and to propose a mechanism for the C-H bond activation. In addition, the structures of the (muo-hydride)(mu-alkynyl) complex 5 and the unprecedented (mu-hydride)(mu-vinyl) derivative 4 have been obtained by X-ray crystallographic analyses.     

Selective C-C bond formation between alkynes mediated by the [RuCp(PR)(3)](+) fragment leading to allyl,butadienyl, and allenyl carbene complexes--an experimental and theoretical study

The reaction of alkynes with [RuCp(PR(3))(CH(3)CN)(2)]PF(6) (R=Me, Ph, Cy) affords, depending on the structure of the alkyne and the substituent of the phosphine ligand, allyl carbene or butadienyl carbene complexes. These reactions involve the migration of the phosphine ligand or a facile 1,2 hydrogen shift. Both reactions proceed via a metallacyclopentatriene complex. If no alpha C[bond]H bonds are accessible, allyl carbenes are formed, while in the presence of alpha C[bond]H bonds butadienyl carbenes are typically obtained. With diphenylacetylene, on the other hand, a cyclobutadiene complex is formed. A different reaction pathway is encountered with HC[triple bond]CSiMe(3), ethynylferrocene (HC[triple bond]CFc), and ethynylruthenocene (HC[triple bond]CRc). Whereas the reaction of [RuCp(PR(3))(CH(3)CN)(2)]PF(6) (R=Ph and Cy) with HC[triple bond]CSiMe(3) affords a vinylidene complex, with HC[triple bond]CFc and HC[triple bond]CRc this reaction does not stop at the vinylidene stage but subsequent cycloaddition yields allenyl carbene complexes. This latter C[bond]C bond formation is effected by strong electronic coupling of the metallocene moiety with the conjugated allenyl carbene unit, which facilitates transient vinylidene formation with subsequent alkyne insertion into the Ru[double bond]C bond. The vinylidene intermediate appears only in the presence of bulky substituents of the phosphine coligand. For the small R=Me, head-to-tail coupling between two alkyne molecules involving phosphine migration is preferred, giving the more usual allyl carbene complexes. X-ray structures of representative complexes are presented. A reasonable mechanism for the formation of both allyl and allenyl carbenes has been established by means of DFT calculations. During the formation of allyl and allenyl carbenes, metallacyclopentatriene and vinylidene complexes, respectively, are crucial intermediates.     

Intermolecular C-H bond activation reactions promoted by transient titanium alkylidynes. Synthesis, reactivity, kinetic, and theoretical studies of the Ti[triple bond]C linkage

The neopentylidene-neopentyl complex (PNP)Ti=CH(t)Bu(CH2(t)Bu) (2; PNP(-) = N[2-P(CHMe2)(2-)4-methylphenyl]2), prepared from the precursor (PNP)Ti[triple bond]CH(t)Bu(OTf) (1) and LiCH2(t)Bu, extrudes neopentane in neat benzene under mild conditions (25 degrees C) to generate the transient titanium alkylidyne, (PNP)Ti[triple bond]C(t)Bu (A), which subsequently undergoes 1,2-CH bond addition of benzene across the Ti[triple bond]C linkage to generate (PNP)Ti=CH(t)Bu(C6H5) (3). Kinetic, mechanistic, and theoretical studies suggest the C-H activation process to obey pseudo-first-order in titanium, the alpha-hydrogen abstraction to be the rate-determining step (KIE for 2/2-d(3) conversion to 3/3-d(3) = 3.9(5) at 40 degrees C) with activation parameters DeltaH = 24(7) kcal/mol and DeltaS = -2(3) cal/mol.K, and the post-rate-determining step to be C-H bond activation of benzene (primary KIE = 1.03(7) at 25 degrees C for the intermolecular C-H activation reaction in C6H6 vs C6D6). A KIE of 1.33(3) at 25 degrees C arose when the intramolecular C-H activation reaction was monitored with 1,3,5-C6H3D3. For the activation of aromatic C-H bonds, however, the formation of the sigma-complex becomes rate-determining via a hypothetical intermediate (PNP)Ti[triple bond]C(t)Bu(C6H5), and C-H bond rupture is promoted in a heterolytic fashion by applying standard Lewis acid/base chemistry. Thermolysis of 3 in C6D6 at 95 degrees C over 48 h generates 3-d(6), thereby implying that 3 can slowly equilibrate with A under elevated temperatures with k = 1.2(2) x 10-5 s(-1), and with activation parameters DeltaH = 31(16) kcal/mol and DeltaS = 3(9) cal/mol x K. At 95 degrees C for one week, the EIE for the 2 --> 3 reaction in 1,3,5-C6H3D3 was found to be 1.36(7). When 1 is alkylated with LiCH2SiMe3 and KCH2Ph, the complexes (PNP)Ti=CHtBu(CH2SiMe3) (4) and (PNP)Ti=CHtBu(CH2Ph) (6) are formed, respectively, along with their corresponding tautomers (PNP)Ti=CHSiMe3(CH2tBu) (5) and (PNP)Ti=CHPh(CH2tBu) (7). By means of similar alkylations of (PNP)Ti=CHSiMe3(OTf) (8), the degenerate complex (PNP)Ti=CHSiMe3(CH2SiMe3) (9) or the non-degenerate alkylidene-alkyl complex (PNP)Ti=CHPh(CH2SiMe3) (11) can also be obtained, the latter of which results from a tautomerization process. Compounds 4/5 and 9, or 6/7 and 11, also activate benzene to afford (PNP)Ti=CHR(C6H5) (R = SiMe3 (10), Ph (12)). Substrates such as FC6H5, 1,2-F2C6H4, and 1,4-F2C6H4 react at the aryl C-H bond with intermediate A, in some cases regioselectively, to form the neopentylidene-aryl derivatives (PNP)Ti=CHtBu(aryl). Intermediate A can also perform stepwise alkylidene-alkyl metatheses with 1,3,5-Me3C6H3, SiMe4, 1,2-bis(trimethylsilyl)alkyne, and bis(trimethylsilyl)ether to afford the titanium alkylidene-alkyls (PNP)Ti=CHR(R') (R = 3,5-Me2C6H2, R' = CH2-3,5-Me2C6H2; R = SiMe3, R' = CH2SiMe3; R = SiMe2CCSiMe3, R' = CH2SiMe2CCSiMe3; R = SiMe2OSiMe3, R' = CH2SiMe2OSiMe3).     

Yttrium complexes incorporating the chelating diamides [ArN(CH2)xNAr]2- (Ar = C6H3-2,6-iPr2, x= 2, 3) and their unusual reaction with phenylsilane

Novel yttrium chelating diamide complexes [(Y[ArN(CH(2))(x)NAr](Z)(THF)(n))(y)] (Z = I, CH(SiMe(3))(2), CH(2)Ph, H, N(SiMe(3))(2), OC(6)H(3)-2,6-(t)Bu(2)-4-Me; x = 2, 3; n = 1 or 2; y = 1 or 2) were made via salt metathesis of the potassium diamides (x = 3 (3), x = 2 (4)) and yttrium triiodide in THF (5,10), followed by salt metathesis with the appropriate potassium salt (6-9, 11-13, 15) and further reaction with molecular hydrogen (14). 6 and 11(Z = CH(SiMe(3))(2), x = 2, 3) underwent unprecedented exchange of yttrium for silicon on reaction with phenylsilane to yield (Si[ArN(CH(2))(x)NAr]PhH) (x = 2 (16), 3) and (Si[CH(SiMe(3))(2)]PhH(2)).     

Preparation, structures and some reactions of novel diynyl complexes of iron and ruthenium

Reactions between HC triple bond CC triple bond CSiMe3 and several ruthenium halide precursors have given the complexes Ru(C triple bond CC triple bond CSiMe3)(L2)Cp'[Cp'= Cp, L = CO (1), PPh3 (2); Cp' = Cp*, L2= dppe (3)]. Proto-desilylation of 2 and 3 have given unsubstituted buta-1,3-diyn-1-yl complexes Ru(C triple bond CC triple bond CH)(L2)Cp'[Cp'= Cp, L = PPh3 (5); Cp'= Cp*, L2 = dppe (6)]. Replacement of H in 5 or 6 with Au(PR3) groups was achieved in reactions with AuCl(PR3) in the presence of KN(SiMe3)2 to give Ru(C triple bond CC triple bond CAu(PR3)](L2)Cp'[Cp' = Cp, L = PPh3, R = Ph (7); Cp' = Cp*, L2= dppe, R = Ph (8), tol (9)]. The asymmetrically end-capped [Cp(Ph3P)2Ru]C triple bond CC triple bond C[Ru(dppe)Cp*] (10) was obtained from Ru(C triple bond CC triple bond CH)(dppe)Cp* and RuCl(PPh3)2Cp. Single-crystal X-ray structural determinations of and are reported, with a comparative determination of the structure of Fe(C triple bond CC triple bond CSiMe3)(dppe)Cp* (4), and those of a fifth polymorph of [Ru(PPh3)2Cp]2(mu-C triple bond CC triple bond C) (12), and [Ru(dppe)Cp]2(mu-C triple bond CC triple bond C) (13).     

U(SMes*)n, (n = 3, 4) and Ln(SMes*)3 (Ln = La, Ce, Pr, Nd): lanthanide(III)/actinide(III) differentiation in agostic interactions and an unprecedented eta3 ligation mode of the arylthiolate ligand, from X-ray diffraction and DFT analysis

Reaction of U(NEt(2))(4) with HS-2,4,6-(t)Bu(3)C(6)H(2) (HSMes) gave U(SMes)(3)(NEt(2))(py) (1), whereas similar treatment of U[N(SiMe(3))SiMe(2)CH(2)][N(SiMe(3))(2)](2) afforded U(SMes)[N(SiMe(3))(2)](3) (2) and U(SMes)(3)[N(SiMe(3))(2)]. The first neutral homoleptic uranium(IV) thiolate to have been crystallographically characterized, U(SMes)(4) (4), was isolated from the reaction of U(BH(4))(4) and KSMes. The first homoleptic thiolate complex of uranium(III), U(SMes)(3) (5), was synthesized by protonolysis of U[N(SiMe(3))(2)](3) with HSMes in cyclohexane. The crystal structure of 5 exhibits the novel eta(3) ligation mode for the arylthiolate ligand. Comparison of the crystal structure of 5 with those of the isomorphous lanthanide congeners Ln(SMes)(3) (Ln = La, Ce, Pr, and Nd) indicates that the U-S, U-C(ipso)(), and U-C(ortho)() bond lengths are shorter than the corresponding ones in the 4f-element analogues, when taking into account the variation in the ionic radii of the metals. The distance between the uranium and the carbon atoms involved in the U...H-C epsilon agostic interaction of each thiolate ligand is shorter, by approximately 0.05 A, than that expected from a purely ionic bonding model. The lanthanide(III)/actinide(III) differentiation was analyzed by density functional theory (DFT). The nature of the M-S bond is shown to be ionic strongly polarized at the sulfur for M = U and iono-covalent (i.e. strongly ionic with low orbital interaction), for M = Ln. The strength of the U...H-C epsilon agostic interaction is proposed to be controlled by the maximization of the interaction between U(+) and S(-) under steric constraints. The eta(3) ligation mode of the arylthiolate ligand is also obtained from DFT.     

Group VI metal aminoborylene complex-catalyzed demercuration reactions of bis(alkynyl)mercurials

The first catalytic application of the Group VI metal borylene complexes [(CO)(5)M[double bond]BN(SiMe(3))(2)] involves the demercuration reaction of bis(alkynyl)mercurials, [Hg(C[triple bond]CR)(2)], with formation of a series of buta-1,3-diynes.     

Synthesis, structure and catalytic activity of alkali metal-free bent-sandwiched lanthanide amido complexes with calix[4]-pyrrolyl ligands

Simple silylamine elimination reactions of calix[4]-pyrrole [R(2)C(C(4)H(2)NH)](4) (R = Me (1), {-(CH(2))(5)-}(0.5) (2)) with 2 equiv. of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) (Ln = Nd, Sm, Dy) in reflux toluene, afforded the novel dinuclear alkali metal-free trivalent lanthanide amido complexes (η(5):η(1):η(5):η(1)-R(8)-calix[4]-pyrrolyl){LnN(SiMe(3))(2)}(2) (R = Me, Ln = Nd (3), Sm (4), Dy (5); R = {-(CH(2))(5)-}(0.5), Ln = Nd (6), Sm(7)). The complexes were fully characterized by elemental analyses, spectroscopic analyses and single-crystal X-ray analyses. X-ray diffraction studies showed that each lanthanide metal was supported by bispyrrolyl anions in an η(5) fashion and along with three nitrogen atoms from N(SiMe(3))(2) and two other pyrroyl rings in η(1) modes formed the novel bent-sandwiched lanthanide amido bridged trivalent lanthanide amido complexes, similar to ansa-cyclopentadienyl ligand-supported lanthanide amides with respect to each metal center. The catalytic activities of these organolanthanide complexes as single component l-lactide polymerization catalysts were studied.     

Reactions of a platinum(III) dimeric complex with alkynes in water: novel approach to alpha-aminoketone, alpha-iminoketone, and alpha,beta-diimine via ketonyl-Pt(III) dinuclear complexes

Reaction of the platinum(III) dimeric complex [Pt(2)(NH(3))(4)((CH(3))(3)CCONH)(2)(NO(3))(2)](NO(3))(2) (1), prepared in situ by the oxidation of the platinum blue complex [Pt(4)(NH(3))(8)((CH(3))(3)CCONH)(4)](NO(3))(5) (2) with Na(2)S(2)O(8), with terminal alkynes CH[triple bond]CR (R = (CH(2))(n)CH(3) (n = 2-5), (CH(2))(n)CH(2)OH (n = 0-2), CH(2)OCH(3), and Ph), in water gave a series of ketonyl-Pt(III) dinuclear complexes [Pt(2)(NH(3))(4)((CH(3))(3)CCONH)(2)(CH(2)COR)](NO(3))(3) (3, R = (CH(2))(2)CH(3); 4, R = (CH(2))(3)CH(3); 5, R = (CH(2))(4)CH(3); 6, R = (CH(2))(5)CH(3); 7, R = CH(2)OH; 8, R = CH(2)CH(2)OH; 9, R = (CH(2))(2)CH(2)OH; 10, R = CH(2)OCH(3); 11, R = Ph). Internal alkyne 2-butyne reacted with 1 to form the complex [Pt(2)(NH(3))(4)((CH(3))(3)CCONH)(2)(CH(CH(3))COCH(3))](NO(3))(3) (12). These reactions show that Pt(III) reacts with alkynes to give various ketonyl complexes. Coordination of the triple bond to the Pt(III) atom at the axial position, followed by nucleophilic attack of water and hydrogen shift from the enol to keto form, would be the mechanism. The structures of complexes 3.H(2)O, 7.0.5C(3)H(4)O, 9, 10, and 12 have been confirmed by X-ray diffraction analysis. A competitive reaction between equimolar 1-pentyne and 1-pentene toward 1 produced complex 3 and [Pt(2)(NH(3))(4)((CH(3))(3)CCONH)(2)(CH(2)CH(OH)CH(2)CH(2)CH(3))](NO(3))(3) (14) at a molar ratio of 9:1, suggesting that alkyne is more reactive than alkene. The ketonyl-Pt(III) dinuclear complexes are susceptible to nucleophiles, such as amines, and the reactions with secondary and tertiary amines give the corresponding alpha-amino-substituted ketones and the reduced Pt(II) complex quantitatively. In the reactions with primary amines, the once formed alpha-amino-substituted ketones were further converted to the iminoketones and diimines. The nucleophilic attack at the ketonyl group of the Pt(III) complexes provides a convenient means for the preparation of alpha-aminoketones, alpha-iminoketones, and diimines from the corresponding alkynes and amines.     

Synthetic and computational studies of the palladium(iv) system Pd(alkyl)(aryl)(alkynyl)(bidentate)(triflate) exhibiting selectivity in C-C reductive elimination

Synthetic routes to methyl(aryl)alkynylpalladium(iv) motifs are presented, together with studies of selectivity in carbon-carbon coupling by reductive elimination from Pd(IV) centres. The iodonium reagents IPh(C[triple bond, length as m-dash]CR)(OTf) (R = SiMe(3), Bu(t), OTf = O(3)SCF(3)) oxidise Pd(II)Me(p-Tol)(L(2)) (1-3) [L(2) = 1,2-bis(dimethylphosphino)ethane (dmpe) (1), 2,2'-bipyridine (bpy) (2), 1,10-phenanthroline (phen) (3)] in acetone-d(6) or toluene-d(9) at -80 °C to form complexes Pd(IV)(OTf)Me(p-Tol)(C[triple bond, length as m-dash]CR)(L(2)) [R = SiMe(3), L(2) = dmpe (4), bpy (5), phen (6); R = Bu(t), L(2) = dmpe (7), bpy (8), phen (9)] which reductively eliminate predominantly (>90%) p-Tol-C[triple bond, length as m-dash]CR above ～-50 °C. NMR spectra show that isomeric mixtures are present for the Pd(IV) complexes: three for dmpe complexes (4, 7), and two for bpy and phen complexes (5, 6, 8, 9), with reversible reduction in the number of isomers to two occurring between -80 °C and -60 °C observed for the dmpe complex 4 in toluene-d(8). Kinetic data for reductive elimination from Pd(IV)(OTf)Me(p-Tol)(C[triple bond, length as m-dash]CSiMe(3))(dmpe) (4) yield similar activation parameters in acetone-d(6) (66 ± 2 kJ mol(-1), ΔH(?) 64 ± 2 kJ mol(-1), ΔS(?)-67 ± 2 J K(-1) mol(-1)) and toluene-d(8) (E(a) 68 ± 3 kJ mol(-1), ΔH(?) 66 ± 3 kJ mol(-1), ΔS(?)-74 ± 3 J K(-1) mol(-1)). The reaction rate in acetone-d(6) is unaffected by addition of sodium triflate, indicative of reductive elimination without prior dissociation of triflate. DFT computational studies at the B97-D level show that the energy difference between the three isomers of 4 is small (12.6 kJ mol(-1)), and is similar to the energy difference encompassing the six potential transition state structures from these isomers leading to three feasible C-C coupling products (13.0 kJ mol(-1)). The calculations are supportive of reductive elimination occurring directly from two of the three NMR observed isomers of 4, involving lower activation energies to form p-TolC[triple bond, length as m-dash]CSiMe(3) and earlier transition states than for other products, and involving coupling of carbon atoms with higher s character of σ-bonds (sp(2) for p-Tol, sp for C[triple bond, length as m-dash]C-SiMe(3)) to form the product with the strongest C-C bond energy of the potential coupling products. Reductive elimination occurs predominantly from the isomer with Me(3)SiC[triple bond, length as m-dash]C trans to OTf. Crystal structure analyses are presented for Pd(II)Me(p-Tol)(dmpe) (1), Pd(II)Me(p-Tol)(bpy) (2), and the acetonyl complex Pd(II)Me(CH(2)COMe)(bpy) (11).