Jan Fraanje

MONODENTATE AND BRIDGING COORDINATION OF 3,3'-ANNELATED 2,2'-BIPYRIDINES IN ZEROVALENT PALLADIUM- AND PLATINUM-P-QUINONE COMPLEXES

Compounds of the type M(N∩N-κN)(nq)2 and M2(μ2-N∩N)(μ2-pbq)2, in which nq = 1,4-naphthoquinone, pbq = 1,4-benzoquinone, and N∩N is a monodentate or bridging ligand of the α-diimine type, were obtained from reactions of Pd(dba)2 in toluene with the 3,3′-annelated-2,2′-bipyridines: 4,5-diazafluoren-9-one (dafo) and 4,5-diazafluorene (dafe) in the presence of the appropriate p-quinone. In the corresponding reactions with 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 2,2′-bipyrimidine (bpym), N,N′-dicyclohexyl-1,4-diaza-1,3-butadiene (chex-dab), bis[N-(o,o′-diisopropyl)phenylimino]acenaphthene (o,o′-iPr2-bian) and 5,6-dihydro-1,10-phenanthroline (dh-phen) only complexes of the type M(N∩N-κ2N)(Q) were formed (Q = nq, pbq). The structures of the complexes have been established by NMR in solution and by X-ray diffraction in the solid state; crystal structures of Pd(bpy-κ2N)(η2-pbq) (1) Pd(dafo-κN)(η2-nq)2 (14) and Pd2(μ2-dafo)(μ2,η2:η2-pbq)2 (16) have been determined. Of the ligands, dafo and dafe are the only ones apt to form complexes containing a monodentate or bridging N∩N ligand. This behaviour is ascribed to the geometrical constraints of dafo and dafe; the annelation by one carbon atom at the 3,3′-positions in these ligands causes an increase in bite angle from approximately 77° to 82°.

Alkyl-dependent photochemistry of Mn(R)(CO)3(R'DAB) (R=Me,Bz; R'=iPr,pTol): Homolysis of the Mn-R bond for R=Bz and release of CO for R=Me

The spectroscopic properties and photochemistry of the complexes Mn(R)(CO)3(R′-DAB) (R=Me, Bz; R′=iPr, pTol) are reported. The UV-photoelectron spectrum of Mn(Me)(CO)3(iPr-DAB) shows that the σ(MnMe) orbital has a higher ionization potential than the Dπ(Mn) orbitals, which is of importance for the photochemical behavior of this complex. The R group bound to the metal determines the photochemistry of these complexes. The Me complexes lose CO upon irradiation into their MLCT bands. The CO-loss products react with Lewis bases, the final product being cis(CO,CO),trans(Me,L)-Mn(Me)(L)(CO)2(R′-DAB). The structure of one of these products, viz. cis,trans-Mn(Me)(P(OMe)3)(CO)2(iPr-DAB)(C14H28N2O5PMn) has been determined by a single-crystal X-ray diffraction study (T=200 K). The crystal is monoclinic, space group P21/n with unit cell dimensions a=15.435(3), b=15.200(3), c=18.192(4) A, V=3915(2) A3, Z=8. The structure refinement converged to R=0.077 for 2829 observed reflections (total number of parameters: 319). Transient absorption spectroscopy shows that an equatorial CO ligand is lost upon excitation and that the final product is formed via different cis,cis-isomers. For R = Bz, visible excitation leads to efficient homolysis (Φ= 0.4 for R′ =iPr) of the MnBz bond, resulting in the formation of radicals which are characterized by ESR spectroscopy. The different behavior of the Bz and Me complexes is attributed to a difference in relative energies of two reactive excited states. For R=Me, the complexes lose CO from the lowest MLCT state; for R=Bz they undergo homolysis of the MnBz bond from the lowest σπ∗ state.

SYNTHESIS AND SPECTROSCOPIC PROPERTIES OF RE(R)(CO)3(ALPHA -DIIMINE) (R=ALKYL ; ALPHA -DIIMINE=R'-PYCA, R'-DAB) COMPLEXES. CRYSTAL STRUCTURE OF RE(ME) (CO)3(IPR-DAB)

Abstract The synthesis, structure and spectroscopic properties of several complexes of the type Re(R)(CO)3(α-diimine) (R  alkyl) are reported. The structure of Re(Me)(CO)3(iPr-DAB) has been determined by a single-crystal X-ray diffraction study. The molecule has a distorted octahedral geometry, with the three carbonyls in a fac-geometry. The complexes possess strong absorption bands in the visible region which are assigned to MLCT transitions with the aid of resonance Raman spectroscopy; the Raman spectra do not provide any evidence for a σ(Re — R) → π∗ (α-diimine) transition within this absorption band. The UV-vis spectrum of Re(Bz)(CO)3(iPr-DAB) (Bz = benzyl) shows a distinct shoulder at the low-energy side of the visible band, which is attributed to the interaction between the dπ(Re)-orbitals and the π-orbitals of the benzyl group. The UV-photoelectron spectrum of Re(Me)(CO)3(iPr-DAB) shows that σ(Re — Me) has a higher ionization potential than the dπ(Re)-orbitals, a result that is of importance for the interpretation of the photochemical behaviour of this complex.

Syntheses, structures and spectroscopic properties of novel inorganometallic complexes Ru(E)(E′)(CO)2(iPr-DAB): (E=Cl, E′=SnPh3, PbPh3; E=Me, E′=SnPh3, PbPh3; E=SnPh3, E′=SnPh3, SnMe3, GePh3; E=PbPh3, E′=PbPh3, PbMe3, GePh3; iPr-DAB=N,N′-diisopropyl-1,4-diaza-1,3-butadiene)

Abstract This article describes the syntheses, structures and spectroscopic (IR, Raman, NMR, visible absorption) properties of novel inorganometallic complexes of the type Ru(E)(E′)(CO) 2 (iPr-DAB) in which E represents a Cl, Me, SnPh 3 or PbPh 3 group and E′=GePh 3 , SnR 3 or PbR 3 (R=Ph, Me) depending on E. The X-ray structures of Ru(Cl)(SnPh 3 )(CO) 2 (iPr-DAB) and Ru(Cl)(PbPh 3 )(CO) 2 (iPr-DAB) show that these complexes have a distorted octahedral geometry with E and E′ in axial positions. The latter complex is, to our knowledge, the first with a Ru–PbR 3 bond for which a crystal structure has been reported. Replacement of Cl by the more electron releasing ligands Me, SnR 3 or PbR 3 causes a shift of ν (CO) and ν (CN) to lower frequencies. At the same time, the strong absorption band shifts from ∼440 to 510–550 nm, with a concomitant decrease of solvatochromism. The very large decrease of solvatochromism upon replacement of Me by GePh 3 or ER 3 (E=Pb, Sn; R=Me, Ph) is tentatively explained with a delocalisation of charge over the axial ER 3 groups. Support for this explanation is provided by the 1 H NMR spectra, which show very large 4 J ( 117/119 Sn,H) and 4 J ( 207 Pb,H) coupling constants of the imine protons in the SnR 3 and PbR 3 containing complexes respectively.

Facile synthesis of highly substituted Pd-η3-allyl complexes containing nitrogen ligands

The first examples of quantitative migratory insertion of allene, 1,1-dimethylallene (DMA) and tetramethylallene (TMA) into alkyl and acyl palladium complexes containing bidentate and terdentate nitrogen ligands are presented; very stable palladium η3-allyl compounds containing 2,2′-bipyridine and 2-(2-{[(6′-methyl-2-pyridyl)methylene]amino}ethyl)-pyridine and an exceptional η1-allyl palladium complex containing terpy have been obtained.

Syntheses, structures and spectroscopic properties of a novel series of metalmetal bonded complexes Ru(E)(E′)(CO)2(iPrDAB): (E Br, E′ Mn(CO)5; E SnPh3, E′ Mn(CO)5, Re(CO)5, CO(CO)4; E Me, E′ Re(CO)5; E E′ Mn(CO)5, Re(CO)5; iPrDAB N,N′-diisopropyl-1,4-diaza-1,3-butadiene)

Abstract This article describes the syntheses, structures and spectroscopic (IR, Raman, NMR, visible absorption) properties of novel metalmetal bonded complexes of the type trans,cis-Ru(E)(E′)(CO)2(iPrDAB) in which E  Br, Me, SnPh3, Mn(CO)5 or Re(CO)5 and E′  Mn(CO)5, Re(CO)5 or Co(CO)4 (depending on E). The structures of Ru(SnPh3)(Mn(CO)5)(CO)2(iPrDAB) Ru(SnPh3)(Co(CO)4)(CO)2(iPrDAB) and Ru(Re(CO)5)2(CO)2(iPrDAB) were determined by single crystal X-ray diffraction. The complexes have a distorted octahedral geometry with E and E′ in axial positions. The structure of Ru(SnPh3)(Co(CO)4)(CO)2(iPrDAB) is noteworthy, since one of the carbonyl ligands of the Co(CO)4 group forms a semi-bridge with Ru. The IR and Raman spectra in the ν(CO) and νs(CN) wavenumber region are assigned. The absorption spectra show one or two charge-transfer bands in the visible region, their position and number depending on E and E′. The SnPh3-complexes show in the 1H NMR spectra a large 4 J( 117 119 Sn,H) coupling constant for the imine protons of their iPrDAB ligands, which points to a strong delocalisation of charge within these complexes.

New furanoditerpenoids from Croton jatrophoides.

Four furanoditerpenoids were isolated from roots of Croton jatrophoides (Euphorbiaceae) collected in Tanzania. In addition to the known compounds penduliflaworosin and teucvin (mallotucin A), a new teucvin isomer, which was named isoteucvin, and a furanoditerpenoid with a new skeleton, for which the name jatrophoidin was adopted, were isolated. Their structures were elucidated by spectroscopic methods such as ESI-MS and NMR, including (1)H-, (13)C-, and two-dimensional NMR. The crystal structures of isoteucvin and jatrophoidin were solved using single-crystal X-ray diffraction, by which we also established the absolute configuration of jatrophoidin. The refined crystal structure of isoteucvin has the same (absolute) configuration as jatrophoidin, although the X-ray diffraction data of isoteucvin were not conclusive with respect to the absolute configuration.

Calix[4]arene based monophosphites, identification of three conformations and their use in the rhodium-catalysed hydroformylation of 1-octene

Eight monodentate phosphites (2–9) based on the calix[4]arene backbone were synthesised following two synthetic routes. Out of six conformations only three were actually formed under the applied reaction conditions. X-Ray analysis of two conformers (4 and 5) provided insight into the 3-dimensional structure of two of these conformations. The three conformations were characterised by 1H, 13C and 31P NMR spectroscopy. NMR experiments showed that several of the phosphites are flexible showing fluxional behaviour of the molecular backbone in solution, but no interconversion between the different conformers was observed. The conformation of the product in the phosphite synthesis is determined at the point where the phosphorus atom is linked to two hydroxyl groups of the calix[4]arene (phosphorus amidite). Such an intermediate phosphorus amidite (12) was isolated in the synthesis of 4 and 5. Phosphites 3–6, 8 and 9 were tested in rhodium-catalysed hydroformylation. Differences in rate can be correlated to the conformation of the ligand.

1,3-dipolar cycloaddition to the Fe-S=C fragment 20. Preparation and properties of carbonyliron complexes of di-thiooxamide. Reactivity of the mononuclear (di-thiooxamide)Fe(CO)(3) towards dimethyl acetylenedicarboxylate

Abstract Reaction of Fe2(CO)9 at room temperature in THF with the di-thiooxamides (L), SC{N(R,R′)}C{(R,R′)N}S [R=Me, R′–R′=(CH2)2 (a); R=H, R′=iPr (b); R=H, R′=iPr (c), R=H, R′=benzyl (d); R=H, R′=H (e)], results for ligands a–d initially in the formation of the mononuclear σ-S, σ-S′ chelate complexes Fe(CO)3(L) (7a–d), which could be isolated in case of 7a and 7d. Under the reaction conditions, complexes 7a–d react further with [Fe(CO)4] fragments to give three types of Fe2(CO)6(L) complexes (8a–d) in high yields, depending on the di-thiooxamide ligand used together with traces of the known complex S2Fe3(CO)9 (14). The molecular structures of these complexes have been established by the single crystal X-ray diffraction determinations of 8a, 8b and 8d. In the reaction with ligand e the corresponding complex 7e was not detected and the well-known complexes 14 and S2Fe3(CO)9 (15) were isolated in low yield. In situ prepared 7a reacts in a slow reaction with 1 equiv. of dimethyl acetylene dicarboxylate in a 1,3-dipolar cycloaddition reaction to give the stable initial ferra [2.2.1] bicyclic complex 10a in 60% yield. In complex 10a an additional Fe(CO)4 fragment is coordinated to the sulfido sulfur atom of the cycloadded FeSC fragment. When a toluene solution of 10a is heated to 50 °C it loses two terminal CO ligands to give the binuclear FeFe bonded complex 11a in almost quantitative yield. The molecular structures of 10a and 11a have been confirmed by single crystal X-ray diffraction. Reaction of 7d at room temperature with 2 equiv. of dimethyl acetylene dicarboxylate results in the mononuclear complex 12d in 5% yield. The molecular structure of 12b has been established by single crystal X-ray diffraction and comprises a tetra dentate ligand with two ferra-sulpha cyclobutene, and a ferra-disulpha cyclopentene moiety. When the reaction is performed at 60 °C a low yield of 2,3,4,5-thiophene tetramethyl tertracarboxylate is obtained besides complex 12d.

Synthesis and Resolution of BICOL, a Carbazole Analogue of BINOL

The synthesis and resolution of a novel chiral C2-symmetric bicarbazolediol (BICOL), is reported. The key step in the synthesis is the copper(II)-catalysed oxidative phenol coupling of 3-hydroxycarbazole. Menthyl chloroformate is used as resolving agent for the separation of the two enantiomers of BICOL. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)