Elena Lastra

Indenyl complexes of Group 8 metals

Abstract The present review article is concerned with the state of the art of the chemistry of indenyl Group 8 metal complexes which has undergone significant progress during the last decade. It deals mainly with complexes of the types: (a) bis(indenyl) sandwich compounds [M(η5-C9H7−xRx)2] (R=H, Me); (b) half-sandwich derivatives [M(η5-C9H7−xRx)(CO)2]2 and [M(η5-C9H7−xRx)XL2] (X=halides, H, alkyl, acetylide; L=two electron donor ligands); (c) cationic complexes [M(η5-C9H7−xRx)L2L′]+ (L, L′=two electron donor ligands). A detailed account of the synthesis, structural and reactivity aspects is presented including kinetic studies and catalytic processes. A discussion of the structural features and coordination modes of the indenyl group with special attention to its distortion parameters is presented. The reactivity studies include redox (chemical and electrochemical) processes, insertion reactions, ring transformations as well as ligand exchange processes in half-sandwich derivatives [M(η5-C9H7−xRx) XL2]. In particular, a detailed discussion of the ability of the moiety [M(η5-C9H7−xRx)L2] to stabilize unsaturated carbene groups such as vinylidene (CCR2, allenylidene CCCR2 and α,β-unsaturated alkenyl carbene C(H)C(R1)CRR′ complexes is presented. The influence of the indenyl ring on the regio- and stereoselective nucleophilic additions to these carbene groups allows selective synthesis leading to either allenyl or functionalized alkynyl complexes. A large number of the latter have been synthesized some of them showing excellent non-linear optical properties.

Synthesis and characterization of novel σ-alkynyl cyclopentadienyl iron(II) complexes [Fe(CCR)L2(η-C5H5)] [L CO; L2 bis(diphenylphosphino)methane (dppm)]. Crystal structure of [Fe(CCC6H5)(dppm)(η-C5H5)]

Abstract The synthesis of novel σ-alkynyl cyclopentadienyl iron(II) complexes of the type [Fe(CCR)L 2 (η-C 5 H 5 )] [L  CO; R  SiMe 3 , t Bu, CO 2 Me; L 2 = bis(diphenylphosphino)methane (dppm), R  SiMe 3 , t Bu, CCO 2 Me, H, C 6 H 5 ] is described. IR and 1 , 31 P{ 1 H} and 13 C NMR data are discussed. The structure of [Fe(CCPh)(dppm)(η-C 5 H 5 )] has been determined by an X-ray diffraction study. the coordination around the Fe atom of the cyclopentadienyl ring (considered as bonded at its centroid), the two P atoms of the dppm molecule acting as a chelating ligand, and the terminal carbon of the phenylacetylide ligand, can be described as a three-legged piano stool. The stabilities of the dppm chelate rings in the complexes have been studied, and their reactions with CO under atmospheric or higher pressure examined.

An unusual coordination mode of acetylide ligands: synthesis of tetranuclear copper(I) complexes containing μ3-ν1 acetylide bridging ligands. Crystal structure of [Cu(μ3-ν1-CCPh)- (Ph2Ppy-P]4(Ph2Ppy = 2-(diphenylphosphine)pyridine)

Abstract The preparation and properties of novel tetranuclear copper(I) complexes of the type [Cu(CCR)(LL)]4 (LL = 2-(diphenylphosphine)pyridine (Ph2Ppy), R = tBu, ph; LL = bis(diphenylphosphino)methane (dppm), R = Ph) are described. The crystal structure of [Cu(μ3-η1-CCph)(Ph2Ppy-P)]4 has been determined by X-ray diffraction. Crystals are monoclinic, space group C2/c with Z = 4 in a unit cell of dimensions a 14.859(3), b 24.405(4), c 23.279(4) A and β 95.35(2)°; refinement gave R = 0.056 for 3586 reflections with I ≥ 2.5σ(I). The molecule consists of a tetrahedral “cluster” of copper atoms bearing four μ3-η1 phenylacetylide and four monodentate P-bonded 2-((diphenylphosphine)pyridine ligands (Ph2Ppy-P). IR, 1H and 31P{1H} NMR data are discussed.

Binuclear copper(I) complexes containing two or three 2-(diphenylphosphine) pyridine (dppy) bridging ligands: X-ray crystal structure of [Cu2(µ-dppy)3(MeCN)][BF4]2 and variable-temperature 1H and 31P-{1H} nuclear magnetic resonance studies

Treatment of [Cu(MeCN)4] BF4 with 2-(diphenylphosphino)pyridine (dppy) at room temperature in acetonitrile or dichloromethane gives [Cu2(µ-dppy)2(MeCN)x][BF4]2, x= 4 or 2, respectively. Reaction with an excess of dppy in refluxing acetone leads to the formation of [Cu2(µ-dppy)3]-[BF4]2, which gives [Cu(µ-dppy)3(MeCN)][BF4]2 upon recrystallization from acetonitrile. This complex can also be obtained from [Cu(MeCN)4]BF4 by reaction with an excess of dppy in refluxing acetonitrile. Substituted complexes [Cu2(µ-dppy)3Lx][BF4]2[x= 1, L = 2-methylpyridine, x= 2, L = 4-methylpyridine, P(OMe)3, or PMe3] are also described. Variable-temperature 1H and 31P-{1H} n.m.r. studies show that MeCN and dppy dissociation and rapid ligand-exchange processes take place in solution. The crystal structure of [Cu2(µ-dppy)3(MeCN)][BF4]2 has been determined by X-ray methods. Crystals are monoclinic, space group P21/c with Z= 4 in a unit cell of dimensions a= 21.424(7), b= 13.186(6), c= 18.232(6)A, and β= 99.77(2)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by blockmatrix least squares to R= 0.0657 for 6 539 observed reflections [I 2σ(I)]. The structure consists of [Cu2(µ-dppy)3(MeCN)]2+ cations and of BF4– anions. In the cations the two copper atoms are held in close proximity [2.721(3)A] by three dppy ligands acting as bridges through the P and N atoms. One copper atom is three-co-ordinate, being bonded to two N and one P atom from dppy ligands, the other is four-co-ordinate, being bonded to two P and one N atom from dppy ligands and to an additional N atom from an acetonitrile molecule. As expected, the Cu–P and Cu–N bonds for the three-co-ordinate copper are shorter than these of the four-co-ordinate copper.

Synthesis and crystal structure of [Cu3(μ3-η1-CCPh)(μ-dppm)3][BF4]2, a tricopper(I) complex containing a μ3-η1 acetylide group and three bis(diphenylphosphino)methane (dppm) bridging ligands

Abstract The synthesis of the cationic trinuclear copper(I) complex [Cu 3 (CCPh)(dppm) 3 ][BF 4 ] 2 is described. An X-ray structure determination shows a triangular array of copper atoms with three diphosphine ligands Ph 2 PCH 2 PPh 2 (dppm) bridging each edge of the triangle and a μ 3 -η 1 phenyl acetylide group bound to the Cu 3 unit.

Reactions of novel cationic diphenylallenylidene complexes [Ru(CC CPh2)L2(η-C9H7)]+(L = PPh3; L2= bis(diphenylphosphino)methane, dppm or 1,2-bis(diphenylphosphino)ethane, dppe) with neutral and anionic nucleophiles

Abstract The synthesis of novel allenylideneruthenium(II) complexes [Ru(CCCPh 2 )L 2 (η-C 9 H 7 )] [PF 6 ] [L = PPh 3 ; L 2 = bis(diphenyl phosphino)methane (dppm) or 1,2-bis(diphenylphosphino)ethane (dppe)] is described. The allenylidene complexes are unreactive towards methanol but other nucleophiles [PMe 3 , NaOMe, LiCCR (R = Ph, n-C 3 H 7 )] can be added regioselectively to the C γ atom to give alkynyl derivatives. [Ru{CCCPh 2 (PMe 3 )}(dppm)(η-C 9 H 7 )] [PF 6 ] isomerizes in tetrahydrofuran solution to the thermodynamically stable product [Ru{C(PMe 3 )CCPh 2 }(dppm)(η-C 9 H 7 )] [PF 6 ].

Facile modification of 1,3,5-triaza-7-phosphatricyclo[3.3.1.1(3,7)]decane phosphanes coordinated to ruthenium(II).

Hydridotris(pyrazolyl)borate (Tp) ruthenium (II) complexes containing new phosphane ligands are described. The new complexes were obtained by electrophilic attack to a coordinated 1,3,5-triaza-7-phosphatricyclo[3.3.1.1(3,7)]decane (PTA) ligand. Thus, cationic complexes [RuX{kappa(3)(N,N,N)-Tp}(PPh(3))(1-R-PTA)][Y] (X = Cl, R = H (1), CH(2)Ph (4), CH(2)CH=CH(2) (6), CH(2)C[triple bond]CH (8); X = I, R = CH(2)Ph (5), CH(2)CH=CH(2) (7)) and neutral [RuCl{kappa(3)(N,N,N)-Tp}(PPh(3))(1-I(2)-PTA)] (3) have been synthesized and characterized. For complexes [RuI{kappa(3)(N,N,N)-Tp}(PPh(3))(1-R-PTA)][Y] (R = CH(2)Ph, CH(2)CH=CH(2)) an unprecedented formal C-H activation has been observed in alcohols leading to complexes with 1-methyl-4-phenyl-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1(3,7)]decane, 4-(2-methoxyethyl)-1-methyl-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1(3,7)]decane and 1-methyl-4-[2-(propan-2-yloxi)ethyl]-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1(3,7)]decane ligands, respectively, and the mechanism explored through deuteriation experiments. The first I(2)-charge transfer compound between I(2) and a nitrogen which belongs to a ligand coordinated to a transition metal, [RuI{kappa(3)(N,N,N)-Tp}(PPh(3))(1-I(2)-PTA)] is described.

Lithioalkynyl iron(II) or ruthenium(II) complexes as precursors of novel alkynyl and vinylidene derivatives: heterobimetallic complexes containing a bridging ethynediyl system

Deprotonation of ethynyl complexes [Fe(CCH)(η5-C5H5)(dppm)]1a(dppm = Ph2PCH2PPh2) and [Ru(CCH)(η5-C9H7)L2][L2= 2PPh31b, Ph2PCH2CH2PPh2(dppe)1c or (PMe3)(PPh3)1d] with LiBut at –78 °C gave the lithiated complexes [Fe(CCLi)(η5-C5H5)(dppm)]2a and [Ru(CCLi)(η5-C9H7)L2]2b–2d, respectively. These species have been used in situ as precursors of novel alkynyl and vinylidene complexes by reactions with electrophiles. Treatment of complexes 2a–2d with MeOSO2CF3 at –78 °C gave vinylidene complexes [Fe(CCMe2)(η5C5H5)(dppm)][CF3SO3]3a and [Ru(CCMe2)(η5-C9H7)L2][CF3SO3][L2= 2PPh33b, dppe 3c or (PPh3)(PMe3)3d]. Iodoalkynyl complexes [Ru(CCl)(η5-C9H7)L2](L2= 2PPh34b or dppe 4c) have been obtained by reaction of [I(py)2][BF4](py = pyridine) with 2b and 2c, respectively. Reaction of 2a–2d with SnPh3Cl yielded the ethynediyl bridging bimetallic complexes [(η5-C5H5)(dppm)Fe–CC–SnPh3]5a and [(η5-C9H7)L2Ru–CC–SnPh3][L2= 2PPh35b, dppe 5c or (PPh3)(PMe3)5d]. Similar heterobimetallic complexes [(η5-C5H5)(dppm)Fe–CC–Au(PPh3)]6a and [(η5-C9H7)L2Ru–CC–Au(PPh3)]6b–6d have been obtained by treatment of ethynyl complexes 1a–1d with [AuCl(PPh3)] and TI(acac)(acac = acetylacetonate) in dichloromethane. Complexes 6a and 6b can alternatively be obtained by reaction of 5a and with 5b with [AuCl(PPh3)] in the presence of [PdCl2(MeCN)2]. The crystal structure of 5a has been determined by X-ray diffraction methods. It shows a typical three-legged piano-stool geometry. The iron atom is bonded to the cyclopentadienyl ring, the two phosphorus atoms of a chelating dppm ligand, with a narrow bite angle [74.90(5)°] and the terminal carbon of the triphenyltin acetylide group. The ethynyl bridge is bound to the iron and tin forming an CC–Sn angle of 162.8(4)° and an almost linear Fe–CC arrangement [178.0(3)°].

1,3-Dipolar cycloadditions of ruthenium(II) azido complexes with alkynes and nitriles.

The diazido complex [Na][Ru(N3)2{κ(3)(N,N,N)-Tpms}(PPh3)] (1) (Tpms = tris(pyrazolyl)methanesulfonate) has been synthesized, and its reactivity toward dipolarophiles has been investigated. Thus, the reaction of 1 with alkynes leads to complexes with one or two triazolate ligands depending on the alkyne and the reaction conditions. Complex 1 also reacts with nitriles. Thus, the reaction with RCN (R = Me, Ph) leads to the substitution products [Ru(N3)(NCR){κ(3)(N,N,N)-Tpms}(PPh3)]. However, when fumaronitrile is used, a complex containing a new κ(2)(N(1),N(3))-5-(1,2,3-triazol-4-yl)-1,2,3,4-tetrazolate ligand is obtained as the result of two consecutive cycloaddition reactions. The mechanism for this unusual reaction has been unambiguously established through the isolation of the intermediate complex resulting from a first cycloaddition between a coordinated azide and the C═C double bond.

Highly Enantioselective Hydrogenation of N‐Aryl Imines Derived from Acetophenones by Using Ru–Pybox Complexes under Hydrogenation or Transfer Hydrogenation Conditions in Isopropanol

The asymmetric reduction of N-aryl imines derived from acetophenones by using Ru complexes bearing both a pybox (2,6-bis(oxazoline)pyridine) and a monodentate phosphite ligand has been described. The catalysts show good activity with a diverse range of substrates, and deliver the amine products in very high levels of enantioselectivity (up to 99 %) under both hydrogenation and transfer hydrogenation conditions in isopropanol. From deuteration studies, a very different labeling is observed under hydrogenation and transfer hydrogenation conditions, which demonstrates the different nature of the hydrogen source in both reactions.