Structure Of Cis Research Articles

New synthetic routes to biscarbonylbipyridinerhenium(I) complexes cis,trans-[Re(X2bpy)(CO)2(PR3)(Y)n+ (X2bpy = 4,4'-X2-2,2'-bipyridine) via photochemical ligand substitution reactions, and their photophysical and electrochemical properties.

Photochemical ligand substitution of fac-[Re(X2bpy)(CO)3(PR3)]+ (X2bpy = 4,4'-X2-2,2'-bipyridine; X = Me, H, CF3; R = OEt, Ph) with acetonitrile quantitatively gave a new class of biscarbonyl complexes, cis,trans[Re(X2bpy)(CO)2(PR3)(MeCN)]+, coordinated with four different kinds of ligands. Similarly, other biscarbonylrhenium complexes, cis,trans-[Re(X2bpy)(CO)2(PR3)(Y)]n+ (n = 0, Y = Cl-; n = 1, Y = pyridine, PR'3), were synthesized in good yields via photochemical ligand substitution reactions. The structure of cis,trans-[Re(Me2bpy)(CO)2[P(OEt)3](PPh3)](PF6) was determined by X-ray analysis. Crystal data: C38H42N2O5F6P3Re, monoclinic, P2(1/a), a = 11.592(1) A, b = 30.953(4) A, c = 11.799(2) A, V = 4221.6(1) A3, Z = 4, 7813 reflections, R = 0.066. The biscarbonyl complexes with two phosphorus ligands were strongly emissive from their 3MLCT state with lifetimes of 20-640 ns in fluid solutions at room temperature. Only weak or no emission was observed in the cases Y = Cl-, MeCN, and pyridine. Electrochemical reduction of the biscarbonyl complexes with Y = Cl- and pyridine in MeCN resulted in efficient ligand substitution to give the solvento complexes cis,trans-[Re(X2bpy)(CO)2(PR3)(MeCN)]+.

Synthesis and characterization of piperidine platinum(II) complexes with dicarboxylates: crystal and molecular structure of cis-[Pt(piperidine) 2Cl 2]·H 2O

A series of new platinum complexes of the type cis-[Pt(PIP) 2X] (where PIP=piperidine and X=dichloro, sulfato, oxalato, malonato, methylmalonato, dimethylmalonato, tartronato, 1,1-cyclopropyldicarboxylato (CPDCA) or 1,1-cyclobutyldicarboxylato (CBDCA) ligand) were synthesized and characterized by elemental analysis, IR, and 195Pt nuclear magnetic resonance spectroscopy. The crystal structure of cis-[Pt(PIP) 2Cl 2]·H 2O was determined by X-ray crystallography. In this complex platinum has slightly distorted square planar geometry with two adjacent corners being occupied by two nitrogen atoms of piperidine, whereas the remaining two adjacent corners are occupied by two chloride atoms. An intricate network of intermolecular hydrogen bonding holds the crystal lattice together. In these complexes, piperidine acts as non-leaving ligand, whereas the dicarboxylic acids act as leaving groups.

Programmed assembly of heteromultinuclear complexes using 4′-diphenylphosphino-2,2′:6′,2″-terpyridine

The complex [Ru(tpy)(1)]2+ (tpy=2,2′:6′,2″-terpyridine; 1=4′-diphenylphosphino-2,2′:6′,2″-terpyridine) was prepared and reacted with trans-[PdCl2(NCMe)2] to give trans-[PdCl2{(μ-1)Ru(tpy)}2]4+ in high yield. With trans-[PtCl2(NCPh)2], [Ru(tpy)(1)]2+ reacts to yield trans-[PtCl2{(μ-1)Ru(tpy)}2]4+ which isomerizes in acetone solution; equilibrium is reached after ≈10 days at room temperature with a 1:19 trans:cis-isomer ratio. The reaction of trans-[PtCl2(NCPh)2] with ligand 1 gives cis-[PtCl2(1)2]. The single crystal structures of cis-[PtCl2(1)2]·H2O and cis-[PtCl2(1)2]·CH2Cl2·1.6C5H12 are described and significant differences in structure are observed dependent upon whether the solvate molecules are able to enter into hydrogen bonding interactions with the complex.

Synthesis and characterisation of platinum(II) complexes containing heterobidentate S,N-chelating ligands: X-ray crystal structure of cis-[Pt{SPPh 2NC(Me)NH- S,N}(PMe 2Ph) 2]Cl

Deprotonation of the terminal amino group in the N-thiophosphoryl compounds Me 2P(S)NC(NH 2) 2 (HL 1), Ph 2P(S)NC(Me)NH 2 (HL 2) or Ph 2P(S)NC(NH 2) 2 (HL 3) using potassium tert butoxide in thf, followed by treatment with cis-[PtCl 2(PR 3) 2] (PR 3=PMe 2Ph or 1 2 dppe) generates monocationic complexes cis-[Pt(L n - S,N)(PR 3) 2]Cl ( 1– 6), which have been characterised by 31P{ 1H} NMR, IR and FAB + mass spectroscopies, and for cis-[Pt(L 2- S,N)(PMe 2Ph) 2]Cl ( 2) by single crystal X-ray diffraction. The molecular structure of 2 reveals bidentate coordination of the platinum(II) centre by a bidentate S,N-chelating [Ph 2P(S)NC(Me)NH] − anion, giving a six-membered platinacycle, which adopts a chaise-longue conformation, with a strong hydrogen-bonding interaction between the chloride counterion and the nitrogen-bound proton.

The Cu(II)-2,2′-bipyridine system revisited

The system formed by Cu(II) and 2,2′-bipyridine (bpy) has been revisited by use of EPR and electronic absorption spectroscopies. The mono-chelated [Cu(bpy)] 2+, bis-chelated trans-[Cu(bpy) 2] 2+ with pseudo-tetrahedral geometry due to the steric hindrance of the 3,3′ hydrogen atoms and tris-chelated [Cu(bpy) 3] 2+ species exist in aqueous solution. In basic media hydrolysis yields [Cu(bpy)OH] + and [Cu(bpy)(OH) 2]. The dimer [Cu(bpy)(OH)] 2 2+ is favoured by increasing metal ion concentration in the pH range 8–10. The EPR spectrum of the dimeric species shows well-resolved Δ M=1 and 2 features, and is different from that observed in the solid state. The zero-field splitting is consistent with a distance of ∼3.4 Å between metallic centres. The behaviour of the complex system is in agreement with potentiometric data reported in the literature. In the EtOH–H 2O mixture the bis-chelated complex adopts a five-coordinate cis structure exhibiting a rhombic EPR spectrum and, in basic solution, the [Cu(bpy) 2(OH)] + species is formed. The attribution of the solution species has been confirmed by the analysis of solid compounds, [Cu(bpy)SO 4]·2H 2O, [Cu(bpy)(H 2O) 2](NO 3) 2, [Cu(bpy) 2OSO 3]·4H 2O and [Cu(bpy) 2ONO 2]NO 3·H 2O, after dissolution.

Asymmetric allyl-metal bonding in substituted (eta3-allyl) palladium complexes: X-ray structures of cis- and trans-4-acetoxy-

Enantiomerically pure cis and trans isomers of 4-acetoxy-[eta3(1,2,3)-cyclohexenyl]palladium chloride dimers (cis-1 and trans-1) were prepared from enantiomerically pure trans-1-acetoxy-4-chloro-2-cyclohexene. X-ray analyses of these complexes show that in the trans complex (trans-1) the six-membered ring prefers a chair conformation, whereas in the cis complex (cis-1) the cyclohexenyl ring has a boat conformation. According to the X-ray structure of trans-1 the Pd-C3 bond is shorter than the other allylic terminal palladium-carbon bond (Pd-C1). On the other hand, in cis-1 the Pd-C3 and Pd-C1 bond lengths are identical within the experimental error. The calculated structures (B3PW91/LANL2DZ + P) of trans-1 and cis-1 also display differences in the allylpalladium bonding. The asymmetric allylpalladium bonding in trans-1 is explained on the basis of pi-sigma electronic interactions between the 4-acetoxy substituent and the allyl-metal moiety.

The co-ordination chemistry of 2-(diphenylphosphinoamino)pyridine †

2-(Diphenylphosphinoamino)pyridine, dppap [Ph2PNHpy], and over 40 illustrative examples of its complexes have been prepared. Monodentate, bidentate and bridging co-ordination of the neutral (and bidentate deprotonated ligand) has been demonstrated in a range of palladium, platinum and gold complexes. Ten demonstrative examples have been characterised by single crystal X-ray diffraction. Ph2PNHpy exists as hydrogen-bonded dimer pairs; cis-[PtCl(Ph2PNHpy-P,N){Ph2PNHpy-P}]Cl packs in hydrogen-bonded infinite chains; cis-[Pt(Ph2PNpy-P,N)2] and cis-[Pd(Ph2PNpy-P,N)2] are isomorphous. The structures of cis-[Pd(Ph2PNHpy-P,N)2][BF4]2, [AuCl(Ph2PNHpy-P)], [Pt(C8H12OMe)(Ph2PNpy-P,N)]·H2O illustrating hydrogen-bonding, cis-[PtCl(Ph2PNHpy-P,N)(PMe3)]Cl, cis-[PtCl(Ph2PNpy-P,N)(PMe3)] and cis-[PtCl(Ph2PNHpy-P,N)(P(OPh)3)]Cl are also reported.

Chiral and achiral platinum(II) complexes for potential use as chemotherapeutic agents: crystal and molecular structures of cis-[Pt(L1)2] and [Pt(L1)Cl(MPSO)] [HL1 = N,N-diethyl-N ′-benzoylthiourea

The synthesis and characterisation of platinum(II) complexes, with the general formula [Pt(acylthioureato)Cl(RR′SO)], is reported. These complexes are readily formed by the reaction of [PtCl2(RR′SO)2] with the acylthiourea ligands, N,N-di(2-hydroxyethyl)-N′-benzoylthiourea (HL), N,N-diethyl-N′-benzoylthiourea (HL1) and N,N-adipoylbis(N′,N′-diethylthiourea) (H2L2) in the presence of sodium acetate. Variation of the sulfoxide ligand (RR′SO) enables preparation of achiral complexes when RR′SO is dimethylsulfoxide (DMSO) or methylphenylsulfoxide (MPSO), and chiral complexes when use is made of the chiral sulfoxides, such as (R)-methyl(p-tolyl)sulfoxide and (S)-methyl(p-tolyl)sulfoxide. The reaction also yields, as a minor product, the corresponding cis-bis(acylthioureato)platinum(II) complexes, which can be removed by chromatography. The molecular structures of the two products, [Pt(L1)Cl(MPSO)] and cis-[Pt(L1)2], were determined by X-ray crystallography. The sulfoxide of [Pt(L1)Cl(MPSO)] is sulfur bound, as expected, and cis to the sulfur atom of the acylthioureato ligand. All bond lengths and bond angles around the square planar platinum are normal, with the Pt–S bond trans to Cl being 2.257(4) A and the Pt–S bond trans to O 2.192(3) A in length. The Pt–O and Pt–Cl bonds are 2.016(9) and 2.334(3) A, respectively, and are within the expected ranges. Similarly, the bond lengths and bond angles around the coordination plane of cis-[Pt(L1)2] compare well with related complexes.

Stabilisation of the [Mn(CO)2]+ fragment by thioether macrocyclic ligands; synthesis, spectroscopic and structural characterisation

The fac-tricarbonyl manganese(I) species fac-[Mn(CO)3(L)]+ (L = [12]aneS4, 1,4,7,10-tetrathiacyclododecane; [14]aneS4, 1,4,8,11-tetrathiacyclotetradecane; or [15]aneS5, 1,4,7,10,13-pentathiacyclopentadecane), formed by treatment of fac-[Mn(CO)3(Me2CO)3]+ with L in MeCN solution, were readily decarbonylated with Me3NO to yield the first dicarbonyl manganese(I) thioether complexes, cis-[Mn(CO)2(L)]+. The crystal structures of [Mn(CO)3([12]aneS4)]CF3SO3 and [Mn(CO)3([15]aneS5)]CF3SO3 confirm the fac tricarbonyl arrangement, with the macrocycle bonded in a tridentate manner, leaving one or two non-bonding S atoms respectively. The crystal structure of cis-[Mn(CO)2([12]aneS4)]CF3SO3·0.5CHCl3 reveals a distorted octahedral geometry at MnI with the two CO ligands mutually cis and with the tetradentate macrocycle occupying the other four co-ordination sites. IR spectroscopic studies reveal that the CO stretching vibrations occur at very low frequency, indicating very significant π-back bonding to the CO ligands, with the thioether ligands behaving essentially as pure σ donors to the low-valent manganese(I) ion in these systems.

Synthesis, characterisation and coordination chemistry of novel chiral N,N-dialkyl-N ′-menthyloxycarbonylthioureas. Crystal and molecular structures of N,N-diethyl-N ′-(−)-(3R)-menthyloxycarbonylthiourea and cis-(S,S)-[Pt(L)Cl(DMSO)] [where HL = N-(+)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea or N-benzoyl-N′,N′-diethylthiourea

The novel ligands N,N-diethyl-N′-(−)-(3R)-menthyloxycarbonylthiourea (HL3), N,N-diethyl-N′-(+)-(3R)-menthyloxycarbonylthiourea (HL4), N-(−)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea (HL5) and N-(+)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea (HL6) have been prepared and characterised. The molecular structure of HL3 has been confirmed by X-ray crystallography. The reaction of these N,N-disubstituted-N′-menthyloxycarbonylthiourea ligands with cis-[PtCl2(DMSO)2] in the presence of sodium acetate yields geometric isomers of the resultant [Pt(L)Cl(DMSO)] complexes, that is the DMSO is sulfur bonded to the platinum in either a cis-(S,S) or trans-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. This is in contrast to the complexation reaction of cis-[PtCl2(DMSO)2] with N-benzoyl-N′,N′-diethylthiourea (HL1) or N-benzoyl-N′-morpholinothiourea (HL2) which yields only one [Pt(L)Cl(DMSO)] complex in which the DMSO is in a cis-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. The molecular structures of cis-(S,S)-[Pt(L)Cl(DMSO)], where L = (L1)− or (L6)−, have been determined by X-ray crystallography. The difference in the coordination chemistry of the acylthiourea and alkoxycarbonylthiourea ligands has been examined further by treating the [Pt(L)Cl(DMSO)] complexes with PPh3 to give the corresponding mono- and bis-(phosphine) complexes, [Pt(L)Cl(PPh3)] and [Pt(L)(PPh3)2]+. The 31P NMR studies of these complexes reveal that the alkoxycarbonylthiourea ligands bind less strongly than the acylthiourea ligands, which is consistent with the crystallographic studies. The weaker binding properties of the alkoxycarbonylthiourea ligands might be a possible explanation for the observed geometric isomerisation of the complexes and that the mechanism could involve a chelate ring opening step.

Synthesis, structure and kinetics of Group 6 metal carbonyl complexes containing a new ‘P2N’ mixed donor multidentate ligand †

The ‘P2N’ mixed donor ligand 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]aniline (PNCHP) reacted with [Cr(CO)4(NBD)] and [M(CO)4(C5H11N)2] (M = Mo or W; NBD = norbornadiene; C5H11N = piperidine) to yield cis-[Cr(CO)4(PNCHP-κ2N,P)] and cis-[M(CO)4(PNCHP-κ2P,P′)] respectively. PNCHP behaves as a ‘P,N’ bidentate ligand when M is Cr and a ‘P,P’ bidentate ligand when M is Mo or W. Heating cis-[Cr(CO)4(PNCHP-κ2N,P)] or cis-[M(CO)4(PNCHP-κ2P,P′)] (M = Mo or W) in toluene affords the complexes mer-[M(CO)3(PNCHP-κ3P,N,P′)] (M = Cr, Mo or W). Reaction of PNCHP with [Mo(CO)3(CHT)] (CHT = 1,3,5-cycloheptatriene) in cold toluene yields fac-[Mo(CO)3(PNCHP-κ3P,N,P′)] which readily isomerises to mer-[Mo(CO)3(PNCHP-κ3P,N,P′)] in solution. PNCHP reacts with UV-irradiated tetrahydrofuran solutions of [M(CO)6] (M = Cr or W) to yield phosphorus bound co-ordination isomers of [M(CO)5(PNCHP-κ1P)]. The same reaction when carried out with one half equivalent of PNCHP yields the PNCHP bridged dinuclear species [{M(CO)5}2(PNCHP-κ2P,P′)]. The compounds have been characterised by spectroscopic means and the single crystal structures of cis-[Cr(CO)4(PNCHP-κ2N,P)], cis-[W(CO)4(PNCHP-κ2P,P′)], mer-[Mo(CO)3(PNCHP-κ3P,N,P′)] and [{W(CO)5}2(PNCHP-κ2P,P′)] determined. In addition, the isomerisation kinetics of fac- to mer-[Mo(CO)3(PNCHP-κ3P,N,P′)] has been studied to determine rate constants and thermodynamic activation parameters.

Crystal structure of cis-[Ru(bpy)2{PMe(o-tol)2}Cl+][ClO- 4]: Steric effects in some PMen(o-tol)3-n (n = 1-3) derivatives of ruthenium(II)

The complex cis-[Ru(bpy)2{PMe(o-tol)2}Cl+][ClO− 4] crystallizes in space group P21/c witha = 9.375(2) A, b = 22.019(7) A, c = 16.153(4) A, β = 90.83(2)°, V = 3333.9(16) A3 and D(calc'd) = 1.547 g/cm3 for Z = 4. The Ru-PMe(o-tol)2 bond length of 2.357(3) A is significantly longer than distances of Ru-PMe2(o-tol) = 2.324(2) A and Ru-PMe3 = 2.310(2) A in analogous complexes. The corresponding Ru-P(o-tol)3 complex has eluded synthesis, probably due to steric hindrance.

Rhodium(I) complexes of robust phosphites derived from calix[4]arenes and their application in the hydroformylation of 1-hexene

The monophosphites derived from calix[4]arene (Laa) and p-tert-butylcalix[4]arene (Lbbb) react with [Rh(CO)2(acac*)] (acac* = ButCOCHCOBut) to give the mononuclear complexes [Rh(CO)(Laa)(acac*)] and [Rh(CO)(Lbbb)(acac*)] respectively. The crystal structure of [Rh(CO)(Lbbb)(acac*)] shows the calixarene conformation to have aryl groups in {down, out, up, up} orientations with one aryl blocking the axial site at the square planar metal. Treatment of [Rh2(μ-Cl)2(CO)4] with Lbbb gives an equilibrium mixture of products which have been assigned to the cis/trans isomers of [Rh2(μ-Cl)2(CO)2(Lbbb)2]. The crystal structure of cis-[Rh2(μ-Cl)2(CO)2(Lbbb)2] has a folded dimer geometry with both the concave and convex faces of the dimer partly blocked by the calixarene phosphite ligand. The rhodium complexes of Laa and Lbbb are very active and chemoselective catalysts for the hydroformylation of hexene but the regioselectivity is low.

Trans–cis isomerization and structure of dimeric [Me2M-μ-N(H)NPh2]2 (M=Al, Ga)

Abstract Reaction of MMe3 (M=Al, Ga) with one equivalent of NH2NPh2 affords a dimeric complex [Me2M-μ-N(H)NPh2]2 [M=Al (1), M=Ga (2)] as a mixture of trans and cis isomers. Purification of 1 and 2 by recrystallization gives only trans isomers 1a and 2a, respectively. Variable-temperature 1H-NMR studies reveal that both 1 and 2 in solution undergo trans→cis isomerization with free energy of activation (ΔGc‡) values of 15.9 for 1 and 18.3 kcal mol−1 for 2. The solid state structures of trans isomers 1a and 2a have been determined by single-crystal X-ray diffraction studies. The molecular geometries of 1a and 2a consist of a centrosymmetric and dimeric unit (MN)2 with two bridging hydrazido groups and two terminal methyl groups bound to each metal atom. The two NNPh2 groups are trans to each other with respect to the (MN)2 core plane. The coordination geometry of both metal and nitrogen atoms are distorted tetrahedral.

The first amidozirconium(IV)–porphyrin complex:cis-[bis(trimethylsilyl)amido]chloro(tetraphenylporphyrinato)zirconium(IV)

The title compound, [ZrCl(C 44 H 28 N 4 )(C 6 H 18 NSi 2 )], is the first amidozirconium(IV)-porphyrin complex and it adopts an out-of-plane cis structure with the Zr atom in a distorted trigonal prismatic coordination geometry.

Coligand Effects on Bonding Mode. Synthesis and Properties of (Diallylmalonato)platinum(II) Complexes of P vs. N Donating Ligand

Abstract The reaction of cis-[PtII(OH)2A2] (A = triethylphosphine (PEt3); A2 = tetrahydro-4H-pyran-4,4-dimethanamine (hpda)) with diallylmalonic acid in aqueous solution affords cis-[Pt(dam)A2] (dam = diallylmalonate). The bonding mode of the dam is dependent upon the donation effect of the phosphine vs the nitrogen coligand. The crystal structure of cis-[Pt(dam)(PEt3)2] (C21H40O4P2Pt·H2O: monoclinic P21/c, a = 13.918(2), b = 12.464(1), c = 15.737(1) Å, β = 107.097(8)°, V = 2609.4(4) Å3, Z = 4, R = 0.033) discloses that the dam is bonded to the platinum atom in a (κ2O3)-mode (Pt–O = 2.057(4), 2.061(4) Å) with two phosphine ligands in the cis position. In contrast, for cis-[Pt(dam)(hpda)] (C16H16N2O5Pt·4.5H2O: monoclinic C2/c, a = 28.250(3), b = 11.169(1), c = 13.368(4) Å, β = 94.16(1)°, V = 4207(1) Å3, Z = 8, R = 0.0293), the dam ligand is chelated to the platinum(II) ion in a (κO,η2-C,C)-mode (Pt–O = 2.004(4) Å; Pt–C = 2.089(6), 2.101(6) Å) in the solid state. cis-[Pt(κ2O3-dam)(PEt3)2] easily reacts with KBr pellet matrix for IR measurements while cis-[Pt(κO,η2-C,C-dam)(hpda)] is inert in the pellet. In solution, however, the structure of cis-[Pt(κ2O3-dam)(PEt3)2] is locked, whereas cis-[Pt(κO,η2-C,C-dam)(hpda)] can be isomerized to cis-[Pt(κ2O3-dam)(hpda)].

Density Functional Study of Tetra-Atomic Clusters and Complexes of the Group 16 Elements: Trends in Structure and Bonding

Se4 and Te4 clusters, the intermolecular weakly bound charge-transfer complexes (Se2)(O2) and (Te2)(O2), and the (X2)(Y2) and (XY)(YX) mixed compounds (X, Y = S, Se, Te) were studied using density functional theory with all-electron and effective core potential basis sets. All systems were analyzed in terms of interactions of the diatomic molecules. The energetically favorable “face to face” binding of the diatomic moieties leads to delocalization of the electron density in the high-lying occupied π*-antibonding orbitals of the tetra-atomic products. The cis structures are minima for all systems considered as a result of this delocalization. For the clusters and mixed compounds, the cis tetra-atomic structures formed by the diatomic molecules with equal or similar electronegativities correspond to global minima. The diatomic fragments in these compounds are nonparallel and have shorter bond lengths than their free diatomic values. For the clusters, the other low-lying isomers ordered according to their re...

Synthesis of thiolate and phosphido bridged iron–manganese complexes; molecular structure of cis-[FeMn(μ-CO)(μ-SEt)(CO) 2(Cp)(C 5H 4Me)

The reaction of [Fe(CO) 2(SR)(Cp)] (R=Et, Ph; Cp=η-C 5H 5) with [Mn(CO) 2(thf)(C 5H 4Me)] (thf=tetrahydrofuran), under photolytic conditions, leads to the formation of the novel heterodinuclear bridged thiolate complexes [FeMn(μ-CO)(μ-SR)(CO) 2(Cp)(C 5H 4Me)] in low yields. [FeMn(μ-CO)(μ-SEt)(CO) 2(Cp)(C 5H 4Me)] consists of a mixture of cis and trans isomers which have been separated and characterized by IR and NMR spectroscopy. The μ-phosphido complex [FeMn(μ-CO)(μ-PPh 2)(CO) 2(Cp)(C 5H 4Me)] has been prepared analogously from [Fe(CO) 2(PPh 2)(Cp)] and [Mn(CO) 2(thf)(C 5H 4Me)]. Variable temperature NMR spectra of the latter heterodinuclear complex, in CDCl 3, show the presence of an equilibrium mixture of the two interconverting cis and - trans isomers. The X-ray molecular structure of cis-[FeMn(μ-CO)(μ-SEt)(CO) 2(Cp)(C 5H 4Me)] shows a bonded Fe–Mn interaction [2.617(2) Å] reinforced by a μ-CO and a μ-SEt ligands. The molecule contains chiral centers at the iron, manganese and sulfur atoms and the diastereoisomer under study exhibits optimized non bonded contacts between the alkyl groups.

The reaction of [Fe 2(η-C 5H 5) 2(CO)(CNMe)(μ-CO)(μ-CNMe 2)] + and related salts with trifluoromethanesulphonic acid, HOSO 2CF 3: structure of cis-[Fe 2(η-C 5H 5) 2(CO) 2(μ-CNMe) (μ-CNMe 2)] [BPh 4

[Fe 2(η-C 5H 5) 2(L)(CNMe)(μ-CO)(μ-CNMe 2)][SO 3CF 3] where L=CO reacts with HOSO 2CF 3 in chloroform solution at room temperature (r.t.) to give [Fe 2(η-C 5H 5) 2(CO) 2{μ-CN(H)Me}(μ-CNMe 2)][SO 3CF 3] 2 (reaction (i)). This salt readily and reversibly loses a proton to form [Fe 2(η-C 5H 5) 2(CO) 2(μ-CNMe)(μ-CNMe 2)][SO 3CF 3] (reaction (ii)) which, in solution, slowly reverts to [Fe 2(η-C 5H 5) 2(CO)(CNMe)(μ-CO)(μ-CNMe 2)][SO 3CF 3] under the influence of UV radiation (reaction (iii)) although it can be trapped by reaction with RX (R=H or alkyl; X −=I − or [SO 3CF 3] −) to give [Fe 2(η-C 5H 5) 2(CO) 2{μ-CN(R)Me}(μ-CNMe 2)][SO 3CF 3] 2 (reaction (iv)). In reactions closely related to (i) and (iii), [Fe 2(η-C 5H 5) 2(L)(CN)(μ-CO)(μ-CNMe 2)] (L=CO or CNMe) is converted by HOSO 2CF 3 to [Fe 2(η-C 5H 5) 2(L)(CO)(μ-CNH 2)(μ-CNMe 2)][SO 3CF 3] 2 (reaction (v)); this is reversed by deprotonation and no intermediates are observed (reaction (vi)). The scope and limitations of these reactions have been investigated. Replacement of L by isocyanides shows that the ease with which t-CNR is converted to μ-CN(H)R (reactions (i) and (v)) decreases along the series CNR=CN −/CNH⪢CNXy′(Xy′=C 6H 3Et 2-2,6)>CNMe>CNEt which reflects the μ-seeking ability of the CNR ligands and not their basicity. Reaction (i) does not take place with cis constrained complexes where the two cyclopentadienyl ligands are linked by a –CH 2C(O)-group, in donor solvents such as acetonitrile, or with weaker acids such as CF 3CO 2H or CH 3CO 2H. Reaction (iii) does not take place when L=CNMe or CNEt, or when μ-CNMe is replaced by μ-CNXy′ even when L=CO. Reaction (vi) always takes place; however, if L=CNMe either it or the t-CO may end-up in the μ-site but the latter is preferred. During reactions (i), (iii), (v) and (vi), cis↔ trans isomerism may accompany ligand migration, but the cis is always the predominant product. Spectroscopic data is presented, assigned and used to distinguish between these isomers. Most is straight-forward, but the IR spectrum of [Fe 2(η-C 5H 5) 2(CO) 2(μ-CNXy′)(μ-CNMe 2)][SO 3CF 3] is very unusual as in solution its ν(μ-C-NXy′) absorption band has a very high frequency,>1900 cm −1, and is very broad, ca. 200 cm −1. The structure of cis-[Fe 2(η-C 5H 5) 2(CO) 2(μ-CNMe)(μ-CNMe 2)][BPh 4] has been determined by X-ray crystallography.

Synthesis and NMR investigation of 3,4‐diazabicyclo[4.3.0]non‐2‐ene and N,N'‐azo‐3‐azabicyclo[3.3.0]octane. X‐ray crystal structure analysis of a new tetrazene derivative

Abstract3,4‐Diazabicyclo[4.3.0]non‐2‐ene and N,N'‐azo‐3‐azabicyclo[3.3.0]octane are the main products of the oxidation of N‐amino‐3‐azabicyclo[3.3.0]octane by chloramine. These new compounds have been isolated and characterized. A structural study has been performed with the goal of establishing the cis—trans configuration at the bicyclic junction. Multinuclear proton decoupling carried out on the endocyclic hydrazone has allowed the determination of the coupling constant of the bridgehead hydrogens. A low temperature conformational study shows splitting of the 13C signal of the carbon atom located α with respect to the ammonia nitrogen. This result, consistent with a cis structure, was confirmed by a nmr analysis conducted on the solid tetrazene derivative. The X‐ray data collection on a single cyrstal of the tetrazene has permitted us to determine the crystallographic properties of this compound. Data processing by direct methods reveals that the geometry of the molecule presents a cis configuration for the bicyclic bridge link and a trans one for the azo group, confirming thus the main results obtained by nmr studies.