Synthesis and intramolecular and interionic structural characterization of half-sandwich (arene)ruthenium(II) derivatives of bis(pyrazolyl)alkanes

Arene ruthenium(II) complexes containing bis(pyrazolyl)methane ligands have been prepared by reacting the ligands L' (L' in general; specifically L(1) = H(2)C(pz)(2), L(2) = H(2)C(pz(Me2))(2), L(3) = H(2)C(pz(4Me))(2), L(4) = Me(2)C(pz)(2) and L(5) = Et(2)C(pz)(2) where pz = pyrazole) with [(arene)RuCl(mu-Cl)](2) dimers (arene = p-cymene or benzene). When the reaction was carried out in methanol solution, complexes of the type [(arene)Ru(L')Cl]Cl were obtained. When L(1), L(2), L(3), and L(5) ligands reacted with excess [(arene)RuCl(mu-Cl)](2), [(arene)Ru(L')Cl][(arene)RuCl(3)] species have been obtained, whereas by using the L(4) ligand under the same reaction conditions the unexpected [(p-cymene)Ru(pzH)(2)Cl]Cl complex was recovered. The reaction of 1 equiv of [(p-cymene)Ru(L')Cl]Cl and of [(p-cymene)Ru(pzH)(2)Cl]Cl with 1 equiv of AgX (X = O(3)SCF(3) or BF(4)) in methanol afforded the complexes [(p-cymene)Ru(L')Cl](O(3)SCF(3)) (L' = L(1) or L(2)) and [(p-cymene)Ru(pzH)(2)Cl]BF(4), respectively. [(p-cymene)Ru(L(1))(H(2)O)][PF(6)](2) formed when [(p-cymene)Ru(L(1))Cl]Cl reacts with an excess of AgPF(6). The solid-state structures of the three complexes, [(p-cymene)Ru{H(2)C(pz)(2)}Cl]Cl, [(p-cymene)Ru{H(2)Cpz(4Me))(2)}Cl]Cl, and [(p-cymene)Ru{H(2)C(pz)(2)}Cl](O(3)SCF(3)), were determined by X-ray crystallographic studies. The interionic structure of [(p-cymene)Ru(L(1))Cl](O(3)SCF(3)) and [(p-cymene)Ru(L')Cl][(p-cymene)RuCl(3)] (L' = L(1) or L(2)) was investigated through an integrated experimental approach based on NOE and pulsed field gradient spin-echo (PGSE) NMR experiments in CD(2)Cl(2) as a function of the concentration. PGSE NMR measurements indicate the predominance of ion pairs in solution. NOE measurements suggest that (O(3)SCF(3))(-) approaches the cation orienting itself toward the CH(2) moiety of the L(1) (H(2)C(pz)(2)) ligand as found in the solid state. Selected Ru species have been preliminarily investigated as catalysts toward styrene oxidation by dihydrogen peroxide, [(p-cymene)Ru(L(1))(H(2)O)][PF(6)](2) being the most active species.     

Syntheses and structures of mono-, di- and tetranuclear rhodium or iridium complexes of thiacalix[4]arene derivatives

The reactions of [Cp*MCl2]2(Cp*=eta5-C5Me5, M = Rh, Ir) with thiacalix[4]arene (TC4A(OH)4) and tetramercaptothiacalix[4]arene (TC4A(SH)4) gave the mononuclear complexes [(Cp*M){eta3-TC4A(OH)2(O)2}] and the dinuclear complexes [(Cp*M)2{eta3eta3-TC4A(S)4}] respectively, while the analogous reactions with dimercaptothiacalix[4]arene (TC4A(OH)2(SH)2) produced the tetranuclear complexes [(Cp*M)2(Cp*MCl2)2-{eta3eta3eta1eta1-TC4A(O)2(S)2}].     

Thiophenolato-bridged dinuclear arene ruthenium complexes: a new family of highly cytotoxic anticancer agents

New cationic diruthenium complexes of the type [(arene)(2)Ru(2)(SPh)(3)](+), arene being C(6)H(6), p-(i)PrC(6)H(4)Me, C(6)Me(6), C(6)H(5)R, where R = (CH(2))(n)OC(O)C(6)H(4)-p-O(CH(2))(6)CH(3) or (CH(2))(n)OC(O)CH=CHC(6)H(4)-p-OCH(3) and n = 2 or 4, are obtained from the reaction of the corresponding precursor [(arene)RuCl(2)](2) and thiophenol and isolated as their chloride salts. The complexes have been fully characterised by spectroscopic methods and the solid state structure of [(C(6)H(6))(2)Ru(2)(SPh)(3)](+), crystallised as the hexafluorophosphate salt, has been established by single crystal X-ray diffraction. The complexes are highly cytotoxic against human ovarian cancer cells (cell lines A2780 and A2780cisR), with the IC(50) values being in the submicromolar range. In comparison the analogous trishydroxythiophenolato compounds [(arene)(2)Ru(2)(S-p-C(6)H(4)OH)(3)]Cl (IC(50) values around 100 μM) are much less cytotoxic. Thus, it would appear that the increased antiproliferative effect of the arene ruthenium complexes is due to the presence of the phenyl or toluyl substituents at the three thiolato bridges.     

Utilization of self-sorting processes to generate dynamic combinatorial libraries with new network topologies

The synthesis of water-soluble, organometallic macrocycles is described. They were obtained by self-assembly in reactions of the half-sandwich complexes [[Ru(C6H5Me)Cl2]2], [[Ru(p-cymene)Cl2]2], [[Rh(Cp)Cl2]2], and [[Ir(Cp*)Cl2]2] with the ligand 5-dimethylaminomethyl-3-hydroxy-2-methyl-4-(1H)-pyridone in buffered aqueous solution at pH 8. The structure of the Ru-(p-cymene) complex was determined by single-crystal X-ray crystallography. Upon mixing, these complexes undergo scrambling reactions to give dynamic combinatorial libraries. In combination with structurally related complexes based on amino-methylated 3-hydroxy-2-(1H)-pyridone ligands, an exchange of metal fragments but no mixing of ligands was observed. This self-sorting behavior was used to construct dynamic combinatorial libraries of macrocycles, in which two four-component sub-libraries are connected by two common building blocks. This type of network topology influences the adaptive behavior of the library as demonstrated in selection experiments with lithium ions as the target.     

Diastereoselective formation of metallamacrocyclic (arene)Ru(II) and CpRh(III) complexes

The reaction of [(arene)RuCl(2)](2) (arene = cymene, 1,3,5-C(6)H(3)Me(3)) and [CpRhCl(2)](2) half-sandwich complexes with tridentate heterocyclic ligands in the presence of base has been investigated. In all cases, the chloro-ligands were substituted to give metallacyclic products with ring sizes between 4 and 18 atoms. The cyclization occurs in a highly diastereoselective fashion with chiral recognition between the different metal fragments. The complexes were comprehensively characterized by elemental analysis, NMR spectroscopy, and single crystal X-ray crystallography. For 2-hydroxy-nicotinic acid and 2-amino-nicotinic acid, dinuclear structures were obtained (15-17) whereas for 2,3-dihydroxyquinoline, 2,3-dihydroxyquinoxaline, and 6-methyl-2,3-phenazinediol, trimeric assemblies were found (19-22), and for 4-imidazolecarboxylic acid, a tetrameric assembly (18) was found.     

Interplay of cubic building blocks in (et6-arene)ruthenium-containing tungsten and molybdenum oxides

A series of molybdenum and tungsten organometallic oxides containing [Ru(arene)]2+ units (arene =p-cymene, C6Me6) was obtained by condensation of [[Ru(arene)Cl2]2] with oxomolybdates and oxotungstates in aqueous or nonaqueous solvents. The crystal structures of [[Ru(eta6-C6Me6]]4W4O16], [[Ru(eta6-p-MeC6H4iPr]]4W2O10], [[[Ru-(eta6-p-MeC6H4iPr)]2(mu-OH)3]2][[Ru(eta6-p-MeC6H4iPr)]2W8O28(OH)2[Ru(eta6-p-MeC6H4iPr)(H2O)]2], and [[Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) have been determined. While the windmill-type clusters [[Ru(eta6-arene)]4(MO3)4(mu3-O)4] (M = Mo, W; arene =p-MeC6H4iPr, C6Me6), the face-sharing double cubane-type cluster [[Ru(eta6-p-MeC6H4iPr)]4(WO2)2(mu3-O)4(mu4-O)2], and the dimeric cluster [[Ru(eta6-p-MeC6H4iPr)(WO3)3(mu3-O)3(mu3-OH)Ru(eta6-pMeC6H4iPr)(H2O)]2(mu-WO2)2]2- are based on cubane-like units, [(Ru(eta6-C6Me6)]2M5O18[Ru(eta6-C6Me6)(H2O)]] (M = Mo, W) are more properly described as lacunary Lindqvist-type polyoxoanions supporting three ruthenium centers. Precubane clusters [[Ru(eta6-arene)](MO3)2(mu-O)3(mu3-O)]6- are possible intermediates in the formation of these clusters. The cluster structures are retained in solution, except for [[Ru(eta6-p-MeC6H4iPr)]4Mo4O16], which isomerizes to the triple-cubane form.     

Connection of metallamacrocycles via dynamic covalent chemistry: a versatile method for the synthesis of molecular cages

A modular approach for the synthesis of cage structures is described. Reactions of [(arene)RuCl(2)](2) [arene = p-cymene, 1,3,5-C(6)H(3)Me(3), 1,3,5-C(6)H(3)(i-Pr)(3)] with formyl-substituted 3-hydroxy-2-pyridone ligands provide trinuclear metallamacrocycles with pendant aldehyde groups. Subsequent condensation reactions with di- and triamines give molecular cages with 3, 6, or 12 Ru centers in a diastereoselective and chemoselective (self-sorting) fashion. Some of the cages can also be prepared in one-pot reactions by mixing [(arene)RuCl(2)](2) with the pyridone ligand and the amine in the presence of base. The cages were comprehensively analyzed by X-ray crystallography. The diameter of the largest dodecanuclear complex is ～3 nm; the cavity sizes range from 290 to 740 ?(3). An amine exchange process with ethylenediamine allows the clean conversion of a dodecanuclear cage into a hexanuclear cage without disruption of the metallamacrocyclic structures.     

Synthesis and reactivities of a bis(cyanamido)-capped triruthenium complex

The tetraruthenium complex [Cp*RuCl]4 (Cp* = eta(5)-C(5)Me(5)) reacts with Na(2)NCN to afford the anionic bis(cyanamido)-capped triruthenium complex [(Cp*Ru)3(micro(3)-NCN)(2)]- ((2-)), which undergoes single electron oxidation to form [(Cp*Ru)3(micro(3)-NCN)2] upon workup with 1 equiv. of [Cp(2)Fe](PF(6)) (Cp = eta(5)-C(5)H(5)). Treatment of (2-) with 1 equiv. of HCl at room temperature leads to the protonation of one of the Ru-Ru edges to give the hydrido-bridged complex [(Cp*Ru)3(micro-H)(micro-NCN)2], while the cationic side-on NCNH(2) complex [(Cp*Ru)3(micro-Cl)(micro(3)-NCN)(micro(3)-NCNH(2)-1kappaC,N:2kappaC:3kappaN)]Cl (5) is obtained by the reaction of (2-) with an excess amount of HCl at -78 degrees C. On the other hand, the reaction of (2-) with BR(3) (R = Et, Ph) results in the ligation of two BR(3) molecules to the terminal nitrogen atoms of the cyanamido ligands to yield the bis(borane) adduct (PPN)[(Cp*Ru)(3){(micro(4)-NCN)(BR(3))}(2)] (6, PPN = Ph(3)PNPPPh(3)). 6b (R = Et) slowly liberates one BEt(3) molecule in acetone to give the mono(borane) adduct (PPN)[(Cp*Ru)3(micro(3)-NCN){(micro(4)-NCN)(BEt(3))}] (7). (2-) is also shown to react with [AuCl(PPh(3))] or PhCOCl to afford the tetranuclear heterometallic complex [(Cp*Ru)3(micro(3)-NCN){(micro(4)-NCN)(AuPPh(3))}] (8) or the benzoylcyanamido complex [(Cp*Ru)3(micro(3)-NCN)(micro(3)-NCNCOPh)] in which the Au(PPh(3))+ or benzoyl fragment is bound to the terminal nitrogen atom of a cyanamido ligand. The molecular structures of PPN+(2-), 5.C(6)H(6), 7 and 8.C(6)H(6) have been determined by single-crystal X-ray analyses.     

One-step synthesis of alkenyl ketone complexes from Cp*RhCl2(PPh3), alkyne and H2O in the presence of KPF6

The reaction of Cp*RhCl2(PPh3) 1 with 1-alkyne and H2O in the presence of KPF6 afforded the alkenyl ketone complex [Cp*Rh(PPh3)(CPh=CHCOCH2R)](PF6) [R = p-tolyl (3a), R = Ph (3b)], whereas Cp*IrCl2(PPh3) 2 or [(eta 6-C6Me6)RuCl2(PPh3) gave the corresponding [Cp*IrCl(CO)(PPh3)](PF6) 5a and [(eta 6-C6Me6)RuCl(CO)(PPh3)](PF6).     

Quasi-octahedral complexes of pentamethylcyclopentadienyliridium(III) bearing bis(diphenylphosphinomethyl)phenylphosphine (dpmp)

Reaction of [Cp*IrCl2]2 (1) with dpmp in the presence of KPF6 afforded a binuclear complex [Cp*IrCl(dpmp-P1,P2;P3)IrCl2Cp*](PF6) (2) (dpmp =(Ph2PCH2)2PPh). The mononuclear complex [Cp*IrCl(dpmp-P1,P2)](PF6) (4) was generated by the reaction of [Cp*IrCl2(BDMPP)](BDMPP =PPh[2,6-(MeO)2C6H3]2) with dpmp in the presence of KPF6. These mono- and binuclear complexes have four-membered ring structures with a terminal and a central P atom of the dpmp ligand coordinated to an iridium atom as a bidentate ligand. Since there are two chiral centers at the Ir atom and a central P2 atom, there are two diastereomers that were characterized by spectrometry. Complexes anti-4 and syn-4 reacted with [Cp*RhCl2]2 or [(C6Me6)RuCl2]2, giving the corresponding mixed-metal complexes, anti- and syn- [Cp*IrCl(dppm-P1,P2;P3)MCl2L](PF6) (6: M = Rh, L = Cp*; 7: M = Ru, L = C6Me6). Treatment with AuCl(SC4H8) gave tetranuclear complexes, anti- and syn-8 [[Cp*IrCl(dppm-P1,P2;P3)AuCl]2](PF6)2 bearing an Au-Au bond. Reaction of anti- with PtCl2(cod) generated the trinuclear complex anti-9, anti-[[Cp*IrCl(dppm-P1,P2;P3)]2PtCl2](PF6)2. These reactions proceeded stereospecifically. The P,O-chelated complex syn-[Cp*IrCl(BDMPP-P,O)] (syn-10)(BDMPP-P,O = PPh[2,6-(MeO)2C6H3][2-O-6-(MeO)C6H3]2) reacted with dpmp in the presence of KPF6, generating the corresponding anti-complex as a main product as well as a small amount of syn-complex, [Cp*Ir(BDMPP-P,O)(dppm-P1)](PF6) (11). The reaction proceeded preferentially with inversion. The reaction processes were investigated by PM3 calculation. anti- was treated with MCl2(cod), giving anti-[Cp*Ir(BDMPP-P,O)(dppm-P1;P2,P3)MCl2](PF6)(14: M = Pt; 15: M = Pd), in which the MCl2 moiety coordinated to the two free P atoms of anti-11. The X-ray analyses of syn-2, anti-2, anti-4, anti-8 and anti-11 were performed.     

Allenylidene-to-indenylidene rearrangement in arene-ruthenium complexes: a key step to highly active catalysts for olefin metathesis reactions

The allenylidene-ruthenium complexes [(eta6-arene)RuCl(=C=C=CR2)(PR'3)]OTf (R2 = Ph; fluorene, Ph, Me; PR'3 = PCy3, P(i)Pr3, PPh3) (OTf = CF3SO3) on protonation with HOTf at -40 C are completely transformed into alkenylcarbyne complexes [(eta6-p-cymene)RuCl([triple bond]CCH=CR2)(PR3)](OTf)2. At -20 degrees C the latter undergo intramolecular rearrangement of the allenylidene ligand, with release of HOTf, into the indenylidene group in derivatives [(eta6-arene)RuCl(indenylidene)(PR3)]OTf. The in situ-prepared indenylidene-ruthenium complexes are efficient catalyst precursors for ring-opening metathesis polymerization of cyclooctene and cyclopentene, reaching turnover frequencies of nearly 300 s(-1) at room temperature. Isolation of these derivatives improves catalytic activity for the ring-closing metathesis of a variety of dienes and enynes. A mechanism based on the initial release of arene ligand and the in situ generation of the active catalytic species RuCl(OTf)(=CH2)(PR3) is proposed.     

Synthesis,structural and chemosensitivity studies of arene d6 metal complexes having N‐phenyl‐N´‐(pyridyl/pyrimidyl)thiourea derivatives

The d⁶ metal complexes of thiourea derivatives were synthesized to investigate its cytotoxicity. Treatment of various N‐phenyl‐N´ pyridyl/pyrimidyl thiourea ligands with half‐sandwich d⁶ metal precursors yielded a series of cationic complexes. Reactions of ligand (L1‐L3) with [(p‐cymene)RuCl₂]₂ and [Cp*MCl₂]₂ (M = Rh/Ir) led to the formation of a series of cationic complexes bearing general formula [(arene)M(L1)к²_(N,S)Cl]⁺, [(arene)M(L2)к²_(N,S)Cl]⁺ and [(arene)M(L3)к²_(N,S)Cl]⁺ [arene = p‐cymene, M = Ru ( 1 , 4 , 7 ); Cp*, M = Rh ( 2 , 5 , 8 ); Cp*, Ir ( 3 , 6 , 9 )]. These compounds were isolated as their chloride salts. X‐ray crystallographic studies of the complexes revealed the coordination of the ligands to the metal in a bidentate chelating N,S‐ manner. Further the cytotoxicity studies of the thiourea derivatives and its complexes evaluated against HCT‐116 (human colorectal cancer), MIA‐PaCa‐2 (human pancreatic cancer) and ARPE‐19 (non‐cancer retinal epithelium) cancer cell lines showed that the thiourea ligands displayed no activity. Upon complexation however, the metal compounds possesses cytotoxicity and whilst potency is less than cisplatin, several complexes exhibited greater selectivity for HCT‐116 or MIA‐PaCa‐2 cells compared to ARPE‐19 cells than cisplatin in vitro. Rhodium complexes of thiourea derivatives were found to be more potent as compared to ruthenium and iridium complexes.     

Catalytic P--H activation by Ti and Zr catalysts

Catalytic dehydrocoupling of phosphines was investigated using the anionic zirconocene trihydride salts [Cp*2Zr(mu-H)3Li]3 (1 a) or [Cp*2Zr(mu-H)3K(thf)4] (1 b), and the metallocycles [CpTi(NPtBu3)(CH2)4] (6) and [Cp*M(NPtBu3)(CH2)4] (M=Ti 20, Zr 21) as catalyst precursors. Dehydrocoupling of primary phosphines RPH2 (R=Ph, C6H2Me3, Cy, C10H7) gave both dehydrocoupled dimers RP(H)P(H)R or cyclic oligophosphines (RP)n (n=4, 5) while reaction of tBu3C6H2PH2 gave the phosphaindoline tBu2(Me2CCH2)C6H2PH 9. Stoichiometric reactions of these catalyst precursors with primary phosphines afforded [Cp*2Zr((PR)2)H][K(thf)4] (R=Ph 2, Cy 3, C6H2Me3 4), [Cp*2Zr((PPh)3)H][K(thf)4] (5), [CpTi(NPtBu3)(PPh)3] (7) and [CpTi(NPtBu3)(mu-PHPh)]2 (8), while reaction of 6 with (C6H2tBu3)PH2 in the presence of PMe3 afforded [CpTi(NPtBu3)(PMe3)(P(C6H2tBu3)] (10). The secondary phosphines Ph2PH and (PhHPCH2)2CH2 also undergo dehydrocoupling affording (Ph2P)2 and (PhPCH2)2CH2. The bisphosphines (CH2PH2)2 and C6H4(PH2)2 are dehydrocoupled to give (PCH2CH2PH)2)(12) and (C6H4P(PH))2 (13) while prolonged reaction of 13 gave (C6H4P2)(8) (14). The analogous bisphosphine Me2C6H4(PH)2 (17) was prepared and dehydrocoupling catalysis afforded (Me2C6H2P(PH))2 (18) and subsequently [(Me2C6H2P2)2(mu-Me2C6H2P2)]2 (19). Stoichiometric reactions with these bisphosphines gave [Cp*2Zr(H)(PH)2C6-H4][Li(thf)4] (22), [CpTi(NPtBu3)(PH)2C6H4]2 (23) and [Cp*Ti(NPtBu3)(PH)2C6H4] (24). Mechanistic implications are discussed.     

Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation

Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine-NHC and amido-NHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [(p-cymene)RuCl(2)](2) and [Cp*MCl(2)](2) (M = Rh, Ir). Treating 2a with [Cp*MCl(2)](2) and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3; M = Ir, 4), resulting from aromatic C-H activation. In contrast, treating 2b with [(p-cymene)RuCl(2)](2), Ag(2)O and KI gave the amine-NHC complex [(p-cymene)Ru(C,NH(2))I]I (5). The reaction of 2b with [Cp*MCl(2)](2) (M = Rh, Ir), NaO(t)Bu and KI gave the amine-NHC complex [Cp*Rh(NH(2))I]I (6) or the amido-NHC complex Cp*Ir(C,NH)I (7); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amine-NHC complex [Cp*Ir(C,NH(2))I][CF(3)CO(2)] (8). These are the first primary amine- or amido-NHC complexes of Rh and Ir. Solid-state structures of the complexes 3-8 have been determined by single crystal X-ray diffraction. Complexes 5, 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity.     

Pyrazole Based Mono‐ and Di‐Substituted Half Sandwich d6 Platinum Group Metal Complexes: Synthesis and Spectral Characterization

Reactions of pyrazole based ligand and halide bridged arene d⁶ metal precursors resulted a series of mono and di‐substituted pyrazole based half sandwich d⁶ metal complexes. In general, they are formulated as [(arene)MLCl₂] [M = Ru, arene = benzene ( 1 ), p‐cymene ( 2 ), arene = Cp*, M = Rh ( 3 ) and Ir ( 4 )] and [(arene)ML₂Cl] [M = Ru, arene = benzene ( 5 ), p‐cymene ( 6 ), arene = Cp*, M = Rh ( 7 ) and Ir ( 8 )]. All these complexes were characterized by various spectroscopic techniques (IR, ¹H NMR, ESI‐MS, and UV/Vis). The molecular structures were confirmed by single‐crystal X‐ray diffraction technique. Spectroscopic studies revealed that complexation i.e., mono‐ and di‐substitution occurred by the ratio‐based reaction between pyrazole ligand and metal precursor through the neutral nitrogen rather than protic nitrogen. In these complexes deprotonation of the protic nitrogen does not occur unlike the other complexes containing pyrazole derivatives, in which the pyrazole ligand is anionic.     

Synthesis of ruthenium(II) complexes containing hydroxymethylphosphines and their catalytic activities for hydrogenation of supercritical carbon dioxide

Ligand substitution of RuCl2[P(C6H5)3]3 and Cp*RuCl(isoprene) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) complexes with hydroxymethylphosphines was investigated to develop new catalyst systems for CO2 hydrogenation. A reaction of P(C6H5)2CH2OH with RuCl2[P(C6H5)3]3 in CH2Cl2 gave Ru(H)Cl(CO)[P(C6H5)2CH2OH]3 (1), which was characterized by NMR spectroscopy and X-ray crystallographic analysis. An isotope labeling experiment using P(C6H5)213CH2OH indicated that the carbonyl moiety in complex 1 originated from formaldehyde formed by degradation of the hydroxymethylphosphine. Elimination of formaldehyde from PCy2CH2OH (Cy=cyclohexyl) was also promoted by treatment of RuCl2[P(C6H5)3]3 in ethanol to give RuCl2(PHCy2)4 under mild conditions. On the other hand, the substitution reaction using Cp*RuCl(isoprene) with the hydroxymethylphosphine ligands proceeded smoothly with formation of Cp*RuCl(L)2 [2a-2c; L=P(C6H5)2CH2OH, PCy(CH2OH)2, and P(CH2OH)3] in good yields. The isolable hydroxymethylphosphine complexes 1 and 2 efficiently catalyzed the hydrogenative amidation of supercritical carbon dioxide (scCO2) to N,N-dimethylformamide (DMF).     

Eta6-mesityl,eta1-imidazolinylidene-carbene-ruthenium(II) complexes: catalytic activity of their allenylidene derivatives in alkene metathesis and cycloisomerisation reactions

The reaction of electron-rich carbene-precursor olefins containing two imidazolinylidene moieties [(2,4,6-Me(3)C(6)H(2)CH(2))NCH(2)CH(2)N(R)Cdbond;](2) (2a: R=CH(2)CH(2)OMe, 2 b R=CH(2)Mes), bearing at least one 2,4,6-trimethylbenzyl (R=CH(2)Mes) group on the nitrogen atom, with [RuCl(2)(arene)](2) (arene=p-cymene, hexamethylbenzene) selectively leads to two types of complexes. The cleavage of the chloride bridges occurs first to yield the expected (carbene) (arene)ruthenium(II) complex 3. Then a further arene displacement reaction takes place to give the chelated eta(6)-mesityl,eta(1)-carbene-ruthenium complexes 4 and 5. An analogous eta(6)-arene,eta(1)-carbene complex with a benzimidazole frame 6 was isolated from an in situ reaction between [RuCl(2)(p-cymene)](2), the corresponding benzimidazolium salt and cesium carbonate. On heating, the RuCl(2)(imidazolinylidene) (p-cymene) complex 8, with p-methoxybenzyl pendent groups attached to the N atoms, leads to intramolecular p-cymene displacement and to the chelated eta(6)-arene,eta(1)-carbene complex 9. On reaction with AgOTf and the propargylic alcohol HCtbond;CCPh(2)OH, compounds 4-6 were transformed into the corresponding ruthenium allenylidene intermediates (4-->10, 5-->11, 6-->12). The in situ generated intermediates 10-12 were found to be active and selective catalysts for ring-closing metathesis (RCM) or cycloisomerisation reactions depending on the nature of the 1,6-dienes. Two complexes [RuCl(2)[eta(1)-CN(CH(2)C(6)H(2)Me(3)-2,4,6)CH(2)CH(2)N- (CH(2)CH(2)OMe)](C(6)Me(6))] 3 with a monodentate carbene ligand and [RuCl(2)[eta(1)-CN[CH(2)(eta(6)-C(6)H(2)Me(3)-2,4,6)]CH(2)CH(2)N-(CH(2)C(6)H(2)Me(3)-2,4,6)]] 5 with a chelating carbene-arene ligand were characterised by X-ray crystallography.     

Arene-mercury complexes stabilized aluminum and gallium chloride: synthesis and structural characterization.

Reaction of HgCl(2) with 2 equiv of MCl(3) in an aromatic solvent yields Hg(arene)(2)(MCl(4))(2) where, arene = C(6)H(5)Me, M = Al (1), Ga (2); arene = C(6)H(5)Et, M = Al (3) and Ga (4); o-C(6)H(4)Me(2), M = Al (5), Ga (6); C(6)H(3)-1,2,3-Me(3), M = Al (7) and Ga (8). The solid-state structures of compounds 1-5 and 7 have been determined by X-ray crystallography. In the solid state, compounds 1-4 and 7 exist as neutral complexes in which two arenes are bound to the mercury, and the MCl(3) groups are bound through bridging chlorides to the mercury; compound 5 exists as a cation-anion pair [Hg(o-C(6)H(4)Me(2))(2)(AlCl(4))][AlCl(4)]. However, in solution compounds 1-8 all exist as neutral complexes. The structures of Hg(arene)(2)(AlCl(4))(2) and [Hg(arene)(2)(AlCl(4))](+) have been determined by DFT calculations [B3LYP level] to facilitate the assignment of the (13)C CPMAS NMR spectra and are in good agreement with the X-ray diffraction structures of compounds 1 and 5. Reaction of HgCl(2) with MCl(3) in benzene, m-xylene, and p-xylene results in the formation of liquid clathrates whose spectroscopic characterization is consistent with ionic structures, [Hg(arene)(2)(MCl(4))][MCl(4)]. The calculated energy difference between Hg(C(6)H(5)Me)(2)(AlCl(4))(2) and [Hg(C(6)H(5)Me)(2)(AlCl(4))][AlCl(4)] is discussed with respect to the structure of compound 5 in the solid state versus solution state and the proposed speciation in the liquid clathrates.     

Insertion reactions of GaCp*, InCp* and In[C(SiMe3)3] into the Ru-Cl bonds of [(p-cymene)RuIICl2]2 and [Cp*RuIICl]4

The first carbonyl free ruthenium/low valent Group 13 organyl complexes are presented, obtained by insertion of ER (ER = GaCp*, InCp*, In[C(SiMe(3))(3)]) into the Ru-Cl bonds of [(p-cymene)RuCl2]2, [Cp*RuCl]4 and [Cp*RuCl2]2. The compound [(p-cymene)RuCl2]2 reacts with GaCp*, giving a variety of isolated products depending on the reaction conditions. The Ru-Ru dimers [{(p-cymene)Ru}2(GaCp*)4(mu3-Cl)2] and the intermediate [{(p-cymene)Ru}2(mu-Cl)2] were isolated, as well as monomeric complexes [(p-cymene)Ru(GaCp*)3Cl2], [(p-cymene)Ru(GaCp*)2GaCl3] and [(p-cymene)Ru(GaCp*)2Cl2(DMSO)]. The reaction of [Cp*RuCl]4 with ER gives "piano-stool" complexes of the type [Cp*Ru(ER)3Cl](ER = InCp*, In[C(SiMe3)3], GaCp*. The chloride ligand in complex can be removed by NaBPh4, yielding [Cp*Ru(GaCp*)3]+[BPh4]-. The reaction of [Cp*RuCl2]2 with GaCp* however, does not lead to an insertion product, but to the ionic Ru(II) complex [Cp*Ru(GaCp*)3]+[Cp*GaCl3]-. The ER ligands in complexes 3, 5, 6, 7 and 8 are equivalent on the NMR timescale in solution due to a chloride exchange between the three Group 13 atoms even at low temperatures. The solid state structures, however, exhibit a different structural pattern. The chloride ligands exhibit two coordination modes: either terminal or bridging. The new compounds are fully characterized including single crystal X-ray diffraction. These results point out the different reactivities of the two precursors and the nature of the neutral p-cymene and the anionic Cp* ligand when bonding to a Ru(II) centre.     

Synthesis of a crystalline molecular complex of Y2+, [(18-crown-6)K][(C5H4SiMe3)3Y

The La(2+) complex [K(18-crown-6)(OEt(2))][Cp″(3)La] (1) [Cp″ = C(5)H(3)(SiMe(3))(2)-1,3], can be synthesized under N(2), but in the presence of KC(5)Me(5), 1 reduces N(2) to the (N═N)(2-) product [(C(5)Me(5))(2)(THF)La](2)(μ-η(2):η(2)-N(2)). This suggests a dichotomy in terms of ligands that optimize isolation of reduced dinitrogen complexes versus isolation of divalent complexes of the rare earths. To determine whether the first crystalline molecular Y(2+) complex could be isolated using this logic, Cp'(3)Y (2) (Cp' = C(5)H(4)SiMe(3)) was synthesized from YCl(3) and KCp' and reduced with KC(8) in the presence of 18-crown-6 in Et(2)O at -45 °C under argon. EPR evidence was consistent with Y(2+) and crystallization provided the first structurally characterizable molecular Y(2+) complex, dark-maroon-purple [(18-crown-6)K][Cp'(3)Y] (3).