Cp*Rh complexes with pyridyloxazolines: synthesis, fluxionality and applications as asymmetric catalysts for Diels-Alder reactions

Half-sandwich complexes [RhCl(pymox)Cp*][SbF(6)](1-7)(pymox = pyridyloxazoline) have been synthesised as single diastereomers. Treatment of these with AgSbF(6) generates dications [Rh(OH(2))(pymox)Cp*](2+) which are fluxional at room temperature and which are enantioselective catalysts for the Diels-Alder reaction of methacrolein and cyclopentadiene. Treatment of the dication [Rh(OH(2))((i)Pr-pymox)Cp*](2+) with [X](-) gives [RhX((i)Pr-pymox)Cp*][SbF(6)](X = Br, I) as single diastereomers whilst reaction with 4-Mepy (4-methylpyridine) gives [Rh(4-Mepy)((i)Pr-pymox)Cp*][SbF(6)] as a mixture of diastereomers. Two complexes, [RhCl((i)Pr-pymox)Cp*][SbF(6)](3) and [RhCl(Bz-pymox)Cp*][SbF(6)](6) have been characterised by X-ray crystallography.     

The use of 1,2-dipiperidinoacetylene for the preparation of monometallic diaminoacetylene and homo- or heterobimetallic diaminodicarbene ruthenium(II) complexes

The reaction of the ynediamine 1,2-dipiperidinoacetylene (1) with [(η(2)-COE)Cr(CO)(5)], [(THF)W(CO)(5)] and [RuCl(2)(η(6)-cymene)](2) afforded homobimetallic complexes 2a, 2b and 3, in which the diaminoacetylene 1 acts as a bis(aminocarbene) ligand by bridging two complex fragments Cr(CO)(5) (in 2a), W(CO)(5) (in 2b) and RuCl(2)(η(6)-cymene) (in 3). The reaction of 1 with [RuCl(2)(PPh(3))(3)] gave trans-[(1)RuCl(PPh(3))(2)]Cl, [4]Cl, in which the alkyne 1 coordinates as a 4-electron donor ligand. The cation 4 represents a rare example of a square-planar Ru(II) complex with a low-spin ground state (S = 0), and its stability can be ascribed to the strong alkyne-metal π-interaction as confirmed by DFT calculations. Treatment with one or two equivalents of NaBPh(4) in acetonitrile gave [4]BPh(4) and the dicationic [(1)Ru(PPh(3))(2)(CH(3)CN)(2)](BPh(4))(2), [5](BPh(4))(2). [4]Cl can be used for the preparation of heterobimetallic Ru-Pd bis(aminocarbene) complexes by reaction with [(MeCN)(2)PdCl(2)], resulting in the formation of bimetallic 6 and tetrametallic 7.     

Ruthenium complexes with tridentate PNX (X = O, S) donor ligands

The ligands, PhPNXMe (1), PhPNXPh (2), and PhPNSMe (3), (PhPNX = 2-Ph2P-C6H4CH[double bond, length as m-dash]NC6H4X-2; X = O, S) have been prepared. A range of new ruthenium complexes were synthesised using these and related ligands, namely: [{RuCl(PhPNO)}2Cl] (4), [Ru(PhPNO)2] (5), [RuCl(PhPNXR)(PPh3)]BPh4 [X = O, R = Me (6); X = O, R = Ph (7); X = S, R = Me (8)], [{RuCl(PhPNX'R)}2Cl]X [X' = O, R = Me, X = Cl(-) (9); X' = S, R = Me, X = BPh4(-) or PF6(-) (10)], and [RuCl(PhPNO-eta 6C6H5)]BPh4 (11). The catalytic activity of these complexes with respect to the hydrosilyation of acetophenone and the hydrogenation of styrene has been investigated, giving an insight into the requirements for an active complex in these reactions.     

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.     

Coordinatively unsaturated semisandwich complexes of ruthenium with phosphinoamine ligands and related species: a complex containing (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane in a new coordination form kappa(3)P,P',N-eta(2)-P,N

The syntheses of the chloro complexes [Ru(eta5-C5R5)Cl(L)] (R = H, Me; L = phosphinoamine ligand) (1a-d) have been carried out by reaction of [(eta5-C5H5)RuCl(PPh3)2] or {(eta5-C5Me5)RuCl}4 with the corresponding phosphinoamine (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane), R,R-dippach, or 1,2-bis(((diisopropylphosphino)amino)ethane), dippae. The chloride abstraction reactions from these compounds lead to different products depending on the starting chlorocomplex and the reaction conditions. Under argon atmosphere, chloride abstraction from [(eta5-C5Me5)RuCl(R,R-dippach)] with NaBAr'4 yields the compound [(eta5-C5Me5)Ru(kappa3P,P'-(R,R)-dippach)][BAr'4] (2b) which exhibits a three-membered ring Ru-N-P by a new coordination form of this phosphinoamine. However, under the same conditions the reaction starting from [(eta5-C5Me5)RuCl(dippae)] yields the unsaturated 16 electron complex [(eta5-C5Me5)Ru(dippae)][BAr'4] (2d). The bonding modes of R,R-dippach and dippae ligands have been analyzed by DFT calculations. The possibility of tridentate P,N,P-coordination of the phosphinoamide ligand to a fragment [(eta5-C5Me5)Ru]+ is always present, but only the presence of a cyclohexane unit in the ligand framework converts this bonding mode in a more favorable option than the usual P,P-coordination. Dinitrogen [(eta5-C5R5)Ru(N2)(L)][BAr'4] (3a-d) and dioxygen complexes [(eta5-C5H5)Ru(O2)(R,R-dippach)][BPh4] (4a) and [(eta5-C5Me5)Ru(O2)(L)][BPh4] (4b,d) have been prepared by chloride abstraction under dinitrogen or dioxygen atmosphere, respectively. The presence of 16 electron [(eta5-C5H5)Ru(R,R-dippach)]+ species in fluorobenzene solutions of the corresponding dinitrogen or dioxygen complexes in conjunction with the presence of [BAr'4]- gave in some cases a small fraction of [Ru(eta5-C5H5)(eta6-C6H5F)][BAr'4] (5a), which has been isolated and characterized by X-ray diffraction.     

New half sandwich-type Ru(II) coordination compounds characterized by the fac-Ru(dmso-S)3 fragment: influence of the face-capping group on the chemical behavior and in vitro anticancer activity

The Ru(II) complex fac-[RuCl(dmso-S)(3)(dmso-O)(2)][PF(6)] (P2) was found to be an excellent precursor for the facile preparation in high yield of half sandwich-type compounds of the general formula fac-[RuCl(dmso-S)(3)(N)(2)][PF(6)] (e.g. (N)(2) = 1,2-diaminoethane (en, 4), trans-1,2-diaminocyclohexane (dach, 5), or 2 NH(3) (6)). Neutral half sandwich-type compounds of the general formula fac-[RuCl(dmso-S)(3)(N-O)] where N-O is an anionic chelating ligand (e.g. N-O = picolinate (pic, 7)) are best prepared from the universal Ru(II)-dmso precursor cis-[RuCl(2)(dmso)(4)] (P1). These complexes, that were fully characterized in solution and in the solid state, are structurally similar to the anticancer organometallic compounds [Ru(η(6)-arene)(chel)Cl][PF(6)](n) but, in place of a face-capping arene, have the fac-Ru(dmso-S)(3) fragment. In contrast to what observed for the corresponding arene compounds, that rapidly hydrolyze the Cl ligand upon dissolution in water, compounds 4-6 are very stable and inert in aqueous solution. Probably their inertness is the reason why they showed no significant cytotoxicity against the MDA-MB-231 cancer cell line.     

Chiral pyridylamino-ruthenium(II) complexes: synthesis, structure and catalytic properties in Diels-Alder reactions

Half-sandwich complexes [(eta(6)-arene)RuCl(pyam)][SbF(6)] (pyam = L(n) = N-(2-pyridylmethyl)-(R)-1-phenylethylamine (L(1)), N-(2-pyridylmethyl)-(R)-1-naphthylethylamine (L(2)), N-(2-quinolylmethyl)-(R)-1-naphthylethylamine (L(3)), N-(2-pyridylmethyl)-(R)-1-cyclohexylethylamine (L(4)), N-(2-pyridylmethyl)-(1R,2S,4R)-1-bornylamine (L(5))) have been synthetised and characterised. Treatment of these compounds with AgSbF(6) generates dicationic complexes [(eta(6)-arene)Ru(pyam)(H(2)O)](2+) which act as enantioselective catalysts for the Diels-Alder reactions of methacrolein and cyclopentadiene. The catalytic reactions occur quickly at room temperature with good exo : endo selectivity (from 84 : 16 to 98 : 2) and moderate enantioselectivity (up to 74% ee). The molecular structures of the chloride complexes (R(Ru),S(N),R(C))-[(eta(6)-p-MeC(6)H(4)iPr)RuClL(1)][SbF(6)], (R(Ru),S(N),S(C2))-[(eta(6)-p-MeC(6)H(4)iPr)RuClL(5)][SbF(6)], and that of the aqua complex (R(Ru),S(N),S(C2))-[(eta(6)-p-MeC(6)H(4)iPr)RuL(5)(H(2)O)][SbF(6)](2), were determined by X-ray diffractometric methods. The distinctive variations observed in the molecular structures of these complexes only concern the puckering parameters of the metallacycle and the relative disposition of substituents within this ring. A clear trend to localise the most steric demanding substituents at equatorial positions is evident from the structural study.     

Preparation of stannyl complexes of ruthenium and osmium stabilised by polypyridine and phosphite ligands

Trichlorostannyl complexes [M(SnCl3)(bpy)2P]BPh4 [M = Ru, P = P(OEt)(3), 1a PPh(OEt)2 1b; M = Os, P = P(OEt)3 2; bpy = 2,2'-bipyridine] were prepared by allowing chloro complexes [MCl(bpy)2P]BPh4 to react with SnCl2 in 1,2-dichloroethane. Bis(trichlorostannyl) compounds Ru(SnCl3)2(N-N)P2 [N-N = bpy, P = P(OEt)3 3a, PPh(OEt)2 3b; N-N = 1,10-phenanthroline (phen), P = P(OEt)3 4] were also prepared by reacting [RuCl(N-N)P3]BPh4 precursors with SnCl2.2H2O in ethanol. Treatment of both mono- 1a, 2 and bis 3a trichlorostannyl complexes with NaBH4 afforded mono- and bis(trihydridestannyl) derivatives [M(SnH3)(bpy)2P]BPh4 5, 6 and Ru(SnH3)2(bpy)P2 7[P = P(OEt)3], respectively. Treatment of 1a, 2 with MgBrMe gave the trimethylstannyl complexes [M(SnMe3)(bpy)2P]BPh4 8, 9 and treatment of 3a afforded the bis(stannyl) Ru(SnClMe2)2(bpy)P2 10 derivative. Alkynylstannyl complexes [M{Sn(C triple bond CR)3}(bpy)2P]BPh4 11-13 and Ru[Sn(C triple bond CR)3]2(N-N)P2 14-17(R = p-tolyl, Bu t; N-N = bpy, phen) were also prepared by allowing trichlorostannyl compounds 1-4 to react with Li+[RC triple bond C]* in thf. The complexes were characterised spectroscopically and by the X-ray crystal structure determination of [Ru(SnMe3)(bpy)2{P(OEt)3}]BPh4 derivative.     

Preparation and reactivity of mixed-ligand ruthenium(II) hydride complexes with phosphites and polypyridyls

Chloro complexes [RuCl(N-N)P3]BPh4 (1-3) [N-N = 2,2'-bipyridine, bpy; 1,10-phenanthroline, phen; 5,5'-dimethyl-2,2'-bipyridine, 5,5'-Me2bpy; P = P(OEt)3, PPh(OEt)2 and PPh2OEt] were prepared by allowing the [RuCl4(N-N)].H2O compounds to react with an excess of phosphite in ethanol. The bis(bipyridine) [RuCl(bpy)2[P(OEt)3]]BPh4 (7) complex was also prepared by reacting RuCl2(bpy)2.2H2O with phosphite and ethanol. Treatment of the chloro complexes 1-3 and 7 with NaBH4 yielded the hydride [RuH(N-N)P3]BPh4 (4-6) and [RuH(bpy)2P]BPh4 (8) derivatives, which were characterized spectroscopically and by the X-ray crystal structure determination of [RuH(bpy)[P(OEt)3]3]BPh4 (4a). Protonation reaction of the new hydrides with Br?nsted acid was studied and led to dicationic [Ru(eta2-H2)(N-N)P3]2+ (9, 10) and [Ru(eta(2-H2)(bpy)2P]2+ (11) dihydrogen derivatives. The presence of the eta2-H2 ligand was indicated by a short T(1 min) value and by the measurements of the J(HD) in the [Ru](eta2-HD) isotopomers. From T(1 min) and J(HD) values the H-H distances of the dihydrogen complexes were also calculated. A series of ruthenium complexes, [RuL(N-N)P3](BPh4)2 and [RuL(bpy)2P](BPh4)2 (P = P(OEt)3; L = H2O, CO, 4-CH3C6H4NC, CH3CN, 4-CH3C6H4CN, PPh(OEt)2], was prepared by substituting the labile eta2-H2 ligand in the 9, 10, 11 derivatives. The reactions of the new hydrides 4-6 and 8 with both mono- and bis(aryldiazonium) cations were studied and led to aryldiazene [Ru(C6H5N=NH)(N-N)P3](BPh4)2 (19, 21), [[Ru(N-N)P3]2(mu-4,4'-NH=NC6H4-C6H4N=NH)](BPh4)4 (20), and [Ru(C6H5N=NH)(bpy)2P](BPh4)2 (22) derivatives. Also the heteroallenes CO2 and CS2 reacted with [RuH(bpy)2P]BPh4, yielding the formato [Ru[eta1-OC(H)=O](bpy)2P]BPh4 and dithioformato [Ru[eta1-SC(H)=S](bpy)2P]BPh4 derivatives.     

Ruthenium(II) polypyridyl complexes: potential precursors, metalloligands, and topo II inhibitors

Neutral and cationic mononuclear complexes containing both group 15 and polypyridyl ligands [Ru(kappa3-tptz)(PPh3)Cl2] [1; tptz=2,4,6-tris(2-pyridyl)-1,3,5-triazine], [Ru(kappa3-tptz)(kappa2-dppm)Cl]BF4 [2; dppm=bis(diphenylphosphino)methane], [Ru(kappa3-tptz)(PPh3)(pa)]Cl (3; pa=phenylalanine), [Ru(kappa3-tptz)(PPh3)(dtc)]Cl (4; dtc=diethyldithiocarbamate), [Ru(kappa3-tptz)(PPh3)(SCN)2] (5) and [Ru(kappa3-tptz)(PPh3)(N3)2] (6) have been synthesized. Complex 1 has been used as a metalloligand in the synthesis of homo- and heterodinuclear complexes [Cl2(PPh3)Ru(micro-tptz)Ru(eta6-C6H6)Cl]BF4 (7), [Cl2(PPh3)Ru(mu-tptz)Ru(eta6-C10H14)Cl]PF6 (8), and [Cl2(PPh3)Ru(micro-tptz)Rh(eta5-C5Me5)Cl]BF4 (9). Complexes 7-9 present examples of homo- and heterodinuclear complexes in which a typical organometallic moiety [(eta6-C6H6)RuCl]+, [(eta6-C10H14)RuCl]+, or [(eta5-C5Me5)RhCl]+ is bonded to a ruthenium(II) polypyridine moiety. The complexes have been fully characterized by elemental analyses, fast-atom-bombardment mass spectroscopy, NMR (1H and 31P), and electronic spectral studies. Molecular structures of 1-3, 8, and 9 have been determined by single-crystal X-ray diffraction analyses. Complex 1 functions as a good precursor in the synthesis of other ruthenium(II) complexes and as a metalloligand. All of the complexes under study exhibit inhibitory effects on the Topoisomerase II-DNA activity of filarial parasite Setaria cervi and beta-hematin/hemozoin formation in the presence of Plasmodium yoelii lysate.     

Ruthenium complexes of substituted hydrazine: new solution- and solid-state binding modes

The methylhydrazine complex [Ru(NH(2)NHMe)(PyP)(2)]Cl(BPh(4)) (PyP=1-[2-(diphenylphosphino)ethyl]pyrazole) was synthesised by addition of methylhydrazine to the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(BPh(4))(2). The methylhydrazine ligand of the ruthenium complex has two different binding modes: side-on (eta(2)-) when the complex is in the solid state and end-on (eta(1)-) when the complex is in solution. The solid-state structure of [Ru(PyP)(2)(NH(2)NHMe)]Cl(BPh(4)) was determined by X-ray crystallography. 2D NMR spectroscopic experiments with (15)N at natural abundance confirmed that in solution the methylhydrazine is bound to the metal centre by only the -NH(2) group and the ruthenium complex retains an octahedral conformation. Hydrazine complexes [RuCl(PyP)(2)(eta(1)-NH(2)NRR')]OSO(2)CF(3) (in which R=H, R'=Ph, R=R'=Me and NRR'=NC(5)H(10)) were formed in situ by the addition of phenylhydrazine, 1,1-dimethylhydrazine and N-aminopiperidine, respectively, to a solution of the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(OSO(2)CF(3))(2) in dichloromethane. These substituted hydrazine complexes of ruthenium were shown to exist in an equilibrium mixture with the bimetallic starting material.     

Ruthenium(II) complexes containing bis(2-(diphenylphosphino)phenyl) ether and their catalytic activity in hydrogenation reactions

The half-sandwich complexes [(eta5-C5H5)RuCl(DPEphos)] (1) and [{(eta6-p-cymene)RuCl2}2(mu-DPEphos)] (2) were synthesized by the reaction of bis(2-(diphenylphosphino)phenyl) ether (DPEphos) with a mixture of ruthenium trichloride trihydrate and cyclopentadiene and with [(eta6-p-cymene)RuCl2]2, respectively. Treatment of DPEphos with cis-[RuCl2(dmso)4] afforded fac-[RuCl2(kappa3-P,O,P-DPEphos)(dmso)] (3). The dmso ligand in 3 can be substituted by pyridine, 2,2'-bipyridine, 4,4'-bipyridine, and PPh3 to yield trans,cis-[RuCl2(DPEphos)(C5H5N)2] (4), cis,cis-[RuCl2(DPEphos)(2,2'-bipyridine)] (5), trans,cis-[RuCl2(DPEphos)(mu-4,4'-bipyridine)]n (6), and mer,trans-[RuCl2(kappa3-P,P,O-DPEphos)(PPh3)] (7), respectively. Refluxing [(eta6-p-cymene)RuCl2]2 with DPEphos in moist acetonitrile leads to the elimination of the p-cymene group and the formation of the octahedral complex cis,cis-[RuCl2(DPEphos)(H2O)(CH3CN)] (8). The structures of the complexes 1-5, 7, and 8 are confirmed by X-ray crystallography. The catalytic activity of these complexes for the hydrogenation of styrene is studied.     

Towards new organometallic wires: tetraruthenium complexes bridged by phenylenevinylene and vinylpyridine ligands

The tetranuclear complexes [{(PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)Ru Cl(CO)(PPh(3))(2)}(2)(mu-CH=CH-C(6)H(4)- CH=CH-1,4)] (3 a) and [{(PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)RuCl(CO)(PPh(3))(2)}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,3)] (3b), which contain vinylpyridine ligands that connect peripheral Ru(PiPr(3))(2)(CO)Cl units to a central divinylphenylene-bridged diruthenium core, have been prepared and investigated. These complexes, in various oxidation states up to the tetracation level, have been characterized by standard electrochemical and spectroelectrochemical techniques, including IR, UV/Vis/NIR and ESR spectroscopy. A comparison with the results for the vinylpyridine-bridged dinuclear complex [PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)RuCl(CO)(PPh(3))(2)(CH=CHPh)] (6) and the divinylphenylene-bridged complexes [{(EtOOCpy)(CO)Cl(PPh(3))(2)Ru}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,4)] (8a) and [{(EtOOCpy)(CO)Cl(PPh(3))(2)Ru}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,3)] (8b), which represent the outer sections (6) or the inner core (8a,b) of complexes 3a,b, and with the mononuclear complex [(EtOOCpy)(CO)(PPh(3))(2)RuCl(CH=CHPh)] (7) indicate that every accessible oxidation process is primarily centred on one of the vinyl ligands, with smaller contributions from the metal centres. The experimental results and quantum chemical calculations indicate charge- and spin-delocalization across the central divinylphenylenediruthenium part of 3a,b or the styrylruthenium unit of 6, but not beyond. The energy gap between the higher lying styryl- or divinylphenylenediruthenium-based and the lower occupied vinylpyridineruthenium-based orbitals increases in the order 6<3 b<3 a and thus follows the conjugation within the non-heteroatom-substituted aromatic vinyl ligand.     

Stepwise assembly of linearly-aligned Ru-M-Ru (M = Pd, Pt) heterotrimetallic complexes with sigma-4-ethynylpyridine spacer

Two heterotrinuclear oligomeric complexes [trans-RuCl(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)](2)[MCl(2)] (M = Pd ; M = Pt ) are prepared from the metalloligand trans-[RuCl(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)] (dppm = Ph(2)PCH(2)PPh(2), ). The resultant linear alignment of the metals [Ru-M-Ru] is imposed by a combinative use of trans-directed spacers and planar metals with trans-juxtaposed donor sites. Ligand exchange of with [Pd(CH(3)CN)(4)][PF(6)](2) gives trans-[Ru(CH(3)CN)(C[triple bond, length as m-dash]Cpy-4)(dppm)(2)][PF(6)] (). All complexes are characterized by single-crystal X-ray crystallography and solution spectroscopy. Acid-base titration on suggested protonation of the pendant pyridyl. Complexes and also undergo protonation at the C[triple bond, length as m-dash]C moiety under acid conditions. The inter-conversion of alkynyl and vinylidene functionality is described. The dual acid and base characters of makes it a potential metalloligand towards basic and acidic fragments in multinuclear heterometallic assemblies.     

Heteronuclear rhodium, palladium, platinum, and gold organoimido complexes from dinuclear organoamido rhodium precursors

Treatment of the organoamido complexes [Rh(2)(mu-4-HNC(6)H(4)Me)(2)(L(2))(2)] (L(2) = 1,5-cyclooctadiene (cod), L = CO) with nBuLi gave solutions of the organoimido species [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(L(2))(2)]. Further reaction of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(cod)(2)] with [Rh(2)(mu-Cl)(2)(cod)(2)] afforded the neutral tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(cod)(4)] (2), which rationalizes the direct syntheses of 2 from [Rh(2)(mu-Cl)(2)(cod)(2)] and Li(2)NC(6)H(4)Me. Reactions of [Li(2)Rh(2)(mu-4-NC(6)H(4)Me)(2)(CO)(4)] with chloro complexes such as [Rh(2)(mu-Cl)(2)(CO)(4)], [MCl(2)(cod)] (M = Pd, Pt), and [Ru(2)(mu-Cl)(2)Cl(2)(p-cymene)(2)] afforded the homo- and heterotrinuclear complexes PPN[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)] (5; PPN=bis(triphenylphosphine)iminium), [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)M(cod)] (M = Pd (6), Pt(7)) and [(CO)(4)Rh(2)(mu-4-NC(6)H(4)Me)(2)Ru(p-cymene)] (8), while the reaction with [AuCl(PPh(3))] gave the tetranuclear compound [(CO)(4)Rh(2)(mu--4-NC(6)H(4)Me)(2)[Au(PPh(3))](2)] (9). The structures of complexes 6, 8, and 9 were determined by X-ray diffraction studies. The anion of 5 reacts with [AuCl(PPh(3))] to give the butterfly cluster [[Rh(3)(mu-4-NC(6)H(4)Me)(2)(CO)(6)]Au(PPh(3))] (10), in which the Au atom is bonded to two rhodium atoms. Reaction of the anion of 5 with [Rh(cod)(NCMe)(2)](BF(4)) gave the tetranuclear complex [Rh(4)(mu-4-NC(6)H(4)Me)(2)(CO)(6)(cod)] (11) in which the Rh(cod) fragment is pi-bonded to one of the arene rings, while the reaction of the anion of 5 with [PdCl(2)(cod)] afforded the heterotrinuclear complex 6 through a metal exchange process.     

Preparation of a series of Ru(II) complexes with N-heterocyclic carbene ligands for the catalytic transfer hydrogenation of aromatic ketones

The reaction of [RuCl(2)(p-cymene](2) with Ag-N-heterocyclic carbene (NHC) complexes yields a series of [(p-cymene)Ru(NHC)] complexes (2a-f). All synthesised compounds were characterized by elemental analysis, NMR spectroscopy and the molecular structure of 2a was determined by X-ray crystallography. All complexes have been tested as catalysts for the transfer hydrogenation of aromatic ketones, showing excellent activity in this reaction.     

Pentamethylcyclopentadienyl-iridium(III) complexes with pyridylamino ligands: synthesis and applications as asymmetric catalysts for Diels-Alder reactions

Reaction of the dimer [(Cp*IrCl)2(P-Cl)2] with chiral pyridylamino ligands (pyam, L1-L5) in the presence of NaSbF6 gave complexes [Cp*IrCl(pyam)][SbF6] 1-5 as diastereomeric mixtures, which have been fully characterised, including the X-ray molecular structure determination of the complexes (S(Ir),R(N),R(C))-[Cp*IrClL1][SbF6] 1a and (R(Ir),S(N),S(C))-[Cp*IrClL5][SbF6] 5a. Treatment of these cations with AgSbF6 affords the corresponding aqua species [Cp*Ir(pyam)(H2O)][SbF6]2 6-10 which have been also fully characterised. The molecular structure of the complex (S(Ir),R(N),R(C))-[Cp*IrL,(H2O)][SbF6]2 6 has been determined by X-ray diffractometric methods. The aqua complexes [Cp*Ir(pyam)(H2O)][SbF6]2 (6, pyam = L2 (7), L3 (8)) evolve to the cyclometallated species [Cp*Ir{kappa3(N,N',C)-(R)-(C6H4)CH(CH3)NHCH2C5NH4}][SbF6] (11), [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)-NHCH2C5NH4)}][SbF6] (12), and [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)NHCH2C9NH6)}][SbF6] (13) respectively, via intramolecular activation of an ortho C-H aryl bond. Complexes 6-10 are enantioselective catalysts for the Diels-Alder reaction between methacrolein and cyclopentadiene. Reaction occurs rapidly at room temperature with good exo : endo selectivity (from 81 : 19 to 98 : 2) and moderate enantioselectivity (up to 72%). The involved intermediate Lewis acid-dienophile compounds [Cp*Ir(pyam)(methacrolein)][SbF]2 (pyam = L4 (14), L5 (15)) have been isolated and characterised.     

Diastereospecific and diastereoselective syntheses of Ruthenium(II) complexes using N,N' bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH2-2-C5H4N and their oxidation to imine ligands

Coordination of N,N' bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH2-2-C5H4N 1 (Ar = 4-CH3-C6H4, 1a; 4-CH3O-C6H4, 1b; 2,6-(CH3)2-C6H3, 1c; 4-CF3-C6H4, 1d) to the moieties [Ru(bipy)2]2+, [Ru(eta5-C5H5)L]+ (L = CH3CN, CO), or [Ru(eta6-arene)Cl]2+ (arene = benzene, p-cymene) occurs under diastereoselective or diastereospecific conditions. Detailed stereochemical analysis of the new complexes is included. The coordination of these secondary amine ligands activates their oxidation to imines by molecular oxygen in a base-catalyzed reaction and hydrogen peroxide was detected as byproduct. The amine-to-imine oxidation was also observed under the experimental conditions of cyclic voltammetry measurements. Deprotonation of the coordinated amine ligands afforded isolatable amido complexes only for the ligand (1-methyl-1-pyridin-2-yl-ethyl)-p-tolyl-amine, 1e, which doesn't contain hydrogen atoms in a beta position relative to the N-H bond. The structures of [Ru(2,2'-bipyridine)2(1b)](PF6)2, 2b; [Ru(2,2'-bipyridine)(2)(1c)](PF6)2, 2c; trans-[RuCl2(COD)(1a)], 3; and [RuCl2(eta6-C6H6)(1a)]PF6, 4a, have been confirmed by X-ray diffraction studies.     

New benzo[h]quinoline-based ligands and their pincer Ru and Os complexes for efficient catalytic transfer hydrogenation of carbonyl compounds

New benzo[h]quinoline ligands (HCN'N) containing a CHRNH2 (R=H (a), Me (b), tBu (c)) function in the 2-position were prepared starting from benzo[h]quinoline N-oxide (in the case of ligand a) and 2-chlorobenzo[h]quinoline (for ligands b and c). These compounds were used to prepare ruthenium and osmium complexes, which are excellent catalysts for the transfer hydrogenation (TH) of ketones. The reaction of a with [RuCl2(PPh3)3] in 2-propanol at reflux afforded the terdentate CN'N complex [RuCl(CN'N)(PPh3)2] (1), whereas the complexes [RuCl(CN'N)(dppb)] (2-4; dppb=Ph2P(CH2)4PPh2) were obtained from [RuCl2(PPh3)(dppb)] with a-c, respectively. Employment of (R,S)-Josiphos, (S,R)-Josiphos*, (S,S)-Skewphos, and (S)-MeO-Biphep in combination with [RuCl2(PPh3)3] and ligand a gave the chiral derivatives [RuCl(CN'N)(PP)] (5-8). The osmium complex [OsCl(CN'N)(dppb)] (12) was prepared by treatment of [OsCl2(PPh3)3] with dppb and ligand a. Reaction of the chloride 2 and 12 with NaOiPr in 2-propanol/toluene afforded the hydride complexes [MH(CN'N)(dppb)] (M=Ru 10, Os 14), through elimination of acetone from [M(OiPr)(CN'N)(dppb)] (M=Ru 9, Os 13). The species 9 and 13 easily reacted with 4,4'-difluorobenzophenone, via 10 and 14, respectively, affording the corresponding isolable alkoxides [M(OR)(CN'N)(dppb)] (M=Ru 11, Os 15). The complexes [MX(CN'N)(P2)] (1-15) (M=Ru, Os; X=Cl, H, OR; P=PPh3 and P2=diphosphane) are efficient catalysts for the TH of carbonyl compounds with 2-propanol in the presence of NaOiPr (2 mol %). Turnover frequency (TOF) values up to 1.8x10(6) h(-1) have been achieved using 0.02-0.001 mol % of catalyst. Much the same activity has been observed for the Ru--Cl, --H, --OR, and the Os--Cl derivatives, whereas the Os--H and Os--OR derivatives display significantly lower activity on account of their high oxygen sensitivity. The chiral Ru complexes 5-8 catalyze the asymmetric TH of methyl-aryl ketones with TOF approximately 10(5) h(-1) at 60 degrees C, up to 97 % enatiomeric excess (ee) and remarkably high productivity (0.005 mol % catalyst loading). High catalytic activity (TOF up to 2.2x10(5) h(-1)) and enantioselectivity (up to 98 % ee) have also been achieved with the in-situ-generated catalysts prepared from [MCl2(PPh3)3], (S,R)-Josiphos or (S,R)-Josiphos*, and the benzo[h]quinoline ligands a-c.     

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.