Emilio Bordignon

Preparation of new ''diazo'' complexes of manganese stabilised by phosphite ligands

Abstract A series of mono- and binuclear aryldiazene complexes [Mn(ArNNH)(CO)nP5−n]BPh4 and [{Mn(CO)nP5−n}2(μ-HNNArArNNH)](BPh4)2 [P=P(OMe)3, P(OEt)3 or P(OPh)3; Ar=C6H5, 4-CH3C6H4; ArAr=4,4′-C6H4C6H4, 4,4′-C6H4CH2C6H4; n=1, 2 or 3] were prepared by allowing hydride species MnH(CO)nP5−n to react with the appropriate aryldiazonium salts at −80°C. Characterisation of the complexes by IR and variable-temperature 1H-, 31P-, 15N-NMR spectra (with 15N isotopic substitution) are reported. Treatment of aryldiazene derivatives containing both the tricarbonyl Mn(CO)3P2 and the dicarbonyl Mn(CO)2P3 fragments with NEt3 affords the pentacoordinate dicarbonyl aryldiazenido Mn(ArN2)(CO)2P2 and [Mn(CO)2P2]2(μ-N2ArArN2) derivatives. Instead, the aryldiazene bonded to the monocarbonyl fragment Mn(CO)P4 is unreactive towards base and does not give aryldiazenido species. Hydrazine complexes [Mn(RNHNH2)(CO)nP5−n]BPh4 [R=H, CH3 or C6H5; P=P(OMe)3, P(OEt)3 or P(OPh)3; n=1, 2 or 3] were prepared by reacting hydride species MnH(CO)nP5−n first with Bronsted acid (HBF4 or CF3SO3H) and then with an excess of the appropriate hydrazine. The binuclear complex [{Mn(CO)3[P(OEt)3]2}2(μ-NH2NH2)](BPh4)2 was also prepared. Oxidation reactions of phenylhydrazine cations [Mn(C6H5NHNH2)(CO)nP5−n]+ with Pb(OAc)4 at −40°C give the phenyldiazene [Mn(C6H5NNH)(CO)nP5−n]+ derivatives, whereas the oxidation of methylhydrazine [Mn(CH3NHNH2)(CO)nP5−n]+ complexes allows the synthesis of the first methyldiazene [Mn(CH3NNH)(CO){P(OMe)3}4]BPh4 derivative of manganese.

Reactivity of [Re(η2-H2)(CO)2P3]+ cations with alkynes: preparation of vinylidene and propadienylidene complexes

Abstract Treatment of [Re(η2-H2)(CO)2P3]+ cations with phenylacetylene leads to the displacement of H2 and the formation of vinylidene [Re{CC(H)Ph}(CO)2P3]+ (1–3) [P=P(OEt)3, PPh(OEt)2 or PPh2OEt] derivatives. Infrared and NMR data support equilibrium in solution [Re(CO)2P3]++PhCCH⇄[Re{CC(H)Ph}(CO)2P3]+ involving the unsaturated complex, free alkyne and vinylidene derivative. 1,4-Diethynylbenzene also tautomerises to the Re(I) centre, affording the [Re{CC(H)(1,4-C6H4CCH)}(CO)2P3]BF4 [P=P(OEt)3 or PPh(OEt)2] vinylidene derivatives. Vinylidene complexes 1–3 are deprotonated easily by NEt3 to give acetylides Re(CCR)(CO)2P3 (4–6) (R=Ph or 1,4-C6H4CCH), which may in turn be reprotonated with HBF4·Et2O to reform vinylidenes 1–3. Acetylide complexes 4–6 were also prepared by reacting unsaturated cations [Re(CO)2P3]+ with lithium acetylide. Binuclear complexes {Re(CO)2P3}2(μ-1,4-CCC6H4CC) (7, 8) [P=PPh(OEt)2 or PPh2OEt] were obtained by sequential treatment of [Re(CO)2P3]+ cations, first with 1,4-HCCC6H4CCH and then with an excess of NEt3. Propadienylidene complexes [Re(CCCPh2)(CO)2P3]BF4 (9, 10) [P=PPh(OEt)2 or PPh2OEt] were prepared by allowing [Re(η2-H2)(CO)2P3]+ cations or unsaturated species [Re(CO)2P3]+ to react with HCCC(Ph2)OH at room temperature. The characterisation of all new complexes by IR and 1H-, 31P{1H}- and 13C{1H}-NMR spectra is also discussed.

Preparation of new acetylide and vinylidene complexes of ruthenium

Abstract Monoacetylide RuCl(CCR)P 4 complexes (R=Ph, 4-MeC 6 H 4 , 1,4-C 6 H 4 CCH, SiMe 3 , Bu t or COOMe; P=P(OEt) 3 or P(OMe) 3 ) were prepared by allowing RuCl 2 P 4 to react with terminal alkynes RCCH in the presence of an excess of NEt 3 . Dinuclear compounds [{Ru[P(OEt) 3 ] 5 } 2 (μ-1,4-CCC 6 H 4 CC)]Y 2 (Y=PF 6 or BPh 4 ) were also prepared from the reaction of RuCl 2 P 4 with 1,4-HCCC 6 H 4 CCH. Treatment of RuCl 2 P 4 with Li + [1,4-HCCC 6 H 4 CC] − afforded bis(alkynyl) Ru(1,4-CCC 6 H 4 CCH) 2 P 4 [P=P(OEt) 3 , P(OMe) 3 or PPh(OEt) 2 ] derivatives. Protonation reactions of monoacetylides RuCl(CCR)P 4 with CF 3 SO 3 H led to vinylidene [RuCl{CC(H)R}P 4 ]CF 3 SO 3 [R=Ph, 4-MeC 6 H 4 or 1,4-C 6 H 4 CCH; P=P(OEt) 3 or P(OMe) 3 ] complexes, which were fully characterised by IR and 1 H-, 31 P- and 13 C-NMR spectra.

Preparation of bis(hydrazine) complexes of iron(II)

Abstract Bis(hydrazine) complexes [ Fe ( RNHNH 2 ) 2 { PPh ( OEt ) 2 } 4 ]( BPh 4 ) 2 ( R = H , CH 3 ) 1, 2 were prepared by allowing nitrile complexes [Fe(CH3CN)2{PPh(OEt)2}4](BPh4)2 to react with hydrazine at 0°C. The monohydrazine [Fe(NH2NH2)(CH3CN)2{P(OEt)3}3] (BPh4)2 derivative was also obtained. Treatment of bis(hydrazine) 1, 2 with Pb(OAc)4 led to the acetate complex [Fe(κ2-O2CCH3){PPh(OEt)2}4]BPh4.

Preparation of the alkynyl-hydride complexes MH(CCR) {PPh(OEt)2}4 of iron and ruthenium

Abstract The hydride FeClHP 4 [P = PPh(OEt) 2 ] was prepared by allowing the complex [FeH( η 2 -H 2 )P 4 ]BPh 4 t react with an excess of lithium chloride. Treatment of FeClHP 4 with lithium acetylide Li[RCC] (R = Ph, p -tolyl or t Bu) gave the alkynyl-hydride FeH(CCR)P 4 derivatives. Related ruthenium RuH(CCR)P 4 complexes were also obtained by treating RuH 2 P 4 with CF 3 SO 3 Me, followed by treatment with lithium acetylide. The characterization of the complexes by IR and 1 H, 31 P and 13 C NMR spectroscopy is discussed, along with some studies on the protonation reactions of the alkynyl-hydride derivatives.

The influence of phosphine ligands on the stoichiometry of mixed-ligand hexacoordinate iron(II) complexes with isocyanides and phosphines

The synthesis and characterization of complexes of the type [FeX(4-CH3-C6H4NC)nL5−n]ClO4 (X  Cl, Br, or I; n = 2, 3 or 4; L  PhPMe2, PhPEt2, Ph2PMe, Ph2PEt, or Ph2P(OEt) are described. The steric hindrance by the phosphine ligand is tentatively correlated with the influence of the π-acidity of phosphine and isocyanide ligands in determining the composition of these compounds. Their structures have been postulated on the basis of infrared and PMR spectra. Mossbauer parameters have also been determined at liquid nitrogen temperature by a treatment of the data by the point-charge model.

Stereospecific oxidation of methionine to methionine sulphoxide by tetrachloroauric(III) acid

The use of gold(III) as oxidant provides a method for the sterospecific oxidation of methionine to methionine sulphoxide under conditions that can be extended to biological systems containing sulphides; preliminary kinetic studies give a possible explanation of the sterospecifiction of this reaction.

Monomeric ruthenium(II) complexes containing diazene and isocyanide ligands: preparation and properties. Crystal structure of [Ru(4-CH3C6H4NNH)-(4-CH3C6H4NC){P(OEt)3}4](PF6)2

Abstract The complexes [Ru(ArNNH)(RNC){P(OEt) 3 } 4 ](BPh 4 ) 2 ( 1 : Ar = 4-CH 3 C 6 H 4 , 4-CH 3 OC 6 H 4 , 4-FC 6 H 4 ; R = 4-CH 3 C 6 H 4 , 4-CH 3 OC 6 H 4 , C 6 H 5 ), [Ru(RNC) 2 -{P(OEt) 3 } 4 ] (BPh 4 ) 2 ( 2 ) and [Ru(RNC) 3 {P(OEt) 3 } 3 ](BPh 4 ) 2 ( 3 ) (R = 4-CH 3 -C 6 H 4 derivatives were prepared by treating the bis(diazene) [Ru(ArNNH) 2 -{P(OEt) 3 } 4 ] 2+ cations with isocyanides: they were characterized by IR and 1 H and 31 P{ 1 H} NMR spectroscopy. The crystal structure of [Ru(4-CH 3 C 6 H 4 NNH)(4-CH 3 C 6 H 4 NC){P(OEt) 3 }4] (PF 6 ) 2 was determined by X-ray diffraction. Crystals are monoclinic, of space group P 2 1 / n with unit-cell dimensions a 23.527(4), b 22.597(3), c 11.565(1) A, β 92.78(1)°, and Z = 4. The structure was solved by the heavy-atom method and refined by least-squares procedures to an R value of 0.0906 for 4812 independent observed reflections. The ruthenium atom lies within an essentially octahedral array of ligands with the diazene and isocyanide groups cis to one another. Reactions of the mono(diazene) derivatives 1 with NaBH 4 and LiCl gave the new complexes [RuH(ArNNH)(RNC){P(OEt) 3 }3]BPh 4 and [RuCl(RNC){P(OEt) 3 } 4 ]BPh 4 .

Preparation of aryldiazene complexes of rhodium

Abstract Aryldiazene complexes [Rh(ArNNH)(CO)(PPh3)3]BF4 (1) and [Rh(ArNNH)(PPh3)4]BF4 (2) (Ar=C6H5 or 4-CH3C6H4) were prepared by allowing hydride species RhH(CO)(PPh3)3 and RhH(PPh3)4 to react with aryldiazonium cations at low temperature. The complexes were characterised by IR and 1H-, 31P- and 15N-NMR spectra, using 15N labelled compounds. Free aryldiazene ArNNH species and [Rh{PPh(OEt)2}4]BF4 were obtained by reacting the hydride RhH[PPh(OEt)2]4 with aryldiazonium cations in CH2Cl2 at −80°C. Reactions of aryldiazene complexes 1 and 2 with H2 (1 atm) were also studied, but did not lead to arylhydrazine derivatives.

Bis(alkynyl) and alkynyl–vinylidene iron(II) complexes with monodentate phosphite ligands

The bis(alkynyl) derivatives [Fe(CCR)2L4][R = Ph, p-tolyl or But; L = P(OMe)3, P(OEt)3 or PPh(OEt)2] were prepared and their protonation and methylation reactions with HBF4 and CF3SO3Me afforded alkynyl–vinylidene cations [Fe(CCR){CC(H)R}L4]+ and [Fe(CCR){CC(Me)R}L4]+, respectively. The aryldiazovinylidene [Fe(CCR){CC(NNC6H4Me-p)Ph}{P(OEt)3}4]BPh4 was also prepared. The complexes were characterized by infrared and 1H, 31P and 13C NMR spectra and the crystal structure of [Fe(CCPh){CC(H)Ph}{P(OEt)3}4]BF4 has been determined. The reactivity of the new vinylidene complexes was studied and showed the rearrangement in solution of the [Fe(CCR){CC(H)R}L4]+ cations to enynyl [Fe(η3-RC3CHR)L4]+ derivatives only in the case of LPPh(OEt)2. Deprotonation with base giving [Fe(CCR)2L4] as well as substitution of the vinylidene ligand in [Fe(CCR){CC(H)R}L4]+ cations by CO and CNC6H4Me-p giving [Fe(CCR)-(CO){P(OEt)3}4]+ and [Fe(CCR)(p-MeC6H4NC){P(OEt)3}4]+ derivatives are also discussed.