Gabriele Albertin

Electronic structures and spectra of hexakisphenylisocyanide complexes of Cr(0), Mo(0), W(0), Mn(I), and Mn(II)

Abstract Electronic absorption spectra of M(CNPh) 6 [M = Cr(0), Mo(0), W(0)], [Mn(CNPh) 6 ]Cl, and [Mn (CNPh) 6 ](PF 6 ) 2 are reported. Each of the M(CNPh) 6 complexes exhibits three intense metal-to-ligand charge transfer (MLCT) absorption bands between 20.8 and 32.7 kK. The lowest MLCT bands are observed at 29.9 and 31.1 kK in the electronic spectrum of Mn (CNPh) 6 + . Low energy bands at 18.2 and 20.4 kK in [Mn(CNPh) 6 ] 2+ are assigned to vibronic components of a σ(CNPh) → dπ charge transfer transition. The unique electronic structural properties of arylisocyanide complexes are apparently related to the π conjugation of aromatic ring orbitals with the out-of-plane π*(CN) function.

New rhenium complexes with phosphinite PPh2OR or phosphonite PPh(OR)2(R = Me, Et or Pri) ligands: synthesis and protonation of various polyhydrides

The rhenium complexes [ReOCl3L2] and [ReCl3L3][L = PPh2OMe, PPh2OEt, PPh2OPri, PPh(OEt)2 or PPh(OPri)2] were prepared by allowing [ReOCl3(AsPh3)2] to react with the appropriate amount of phosphinite or phosphonite. Treatment of [ReCl3L3] with CO and p-MeC6H4NC afforded the mer-trans-[ReCl(CO)3L2] and [ReCl2(p-MeC6H4NC)4L]BPh4 complexes, respectively. Treatment of [ReOCl3L2] with NaBH4 gave [Re2H8L4], but in the presence of phosphinite or phosphonite the trihydrides [ReH3L4] were obtained. Treatment of [ReCl3L3] with NaBH4 gave instead pentahydride complexes [ReH5L3]. All the multihydrides were characterised as ‘classical’ species by variable-temperature NMR spectroscopy (1H and 31P) and T1 measurements. Protonation of [Re2H8L4] and [ReH3L4] with HBF4·Et2O gave the classical hydride cations [Re2H9L4]+ and [ReH4L4]+, respectively, while similar treatment of [ReH5L3] gave a species formulated as containing an η2-H2 ligand, [ReH4(η2-H2)L3]+ on the basis of T1(min) evidence.

Iridium-assisted CC bond cleavage of 1-alkyne by water: preparation of new alkyl derivatives

Alkyl complexes IrCl2(η1-CH2Ar)(CO)(PPh3)2 (1) [Ar = Ph (a), p-tolyl (b)] were prepared by allowing the hydride mer- or fac-IrHCl2(PPh3)3 to react with terminal alkynes ArCCH in the presence of water. The complexes were characterized spectroscopically (IR and 1H, 31P, 13C NMR) and by the X-ray crystal structure determination of 1b. The acyl complex IrCl2{C(O)CH2C(CH3)3}(PPh3)2 (2) was also prepared by reacting mer-IrHCl2(PPh3)3 with tert-butylacetylene HCCC(CH3)3 in the presence of H2O. A reaction path for the hydration of terminal alkyne in the presence of the Ir(III) complex leading to the cleavage of the CC bond, with the formation of the complexes 1 or 2 is also proposed. Acetylide complexes IrHCl(CCAr)(PPh3)3 (3), IrHCl(CCAr)(AsPh3)3 (4) [Ar = Ph (a), p-tolyl (b)] and IrHCl(CCPh){PPh(OEt)2}(PPh3)2 (5) were prepared by reacting IrHCl2L3 (L = PPh3, AsPh3) or IrHCl2{PPh(OEt)2}(PPh3)2 with lithium acetylide. Protonation reaction with Bronsted acids of the acetylide 3 was also studied and led to unstable vinyl derivatives. The stable vinyl [IrCl{η2-CHC(H)COOMe}L2]BPh4 (6,7) [L = PPh3 (6), AsPh3 (7)] complexes, instead, were prepared by allowing IrHCl2L3 to react first with AgCF3SO3 and then with methyl propiolate.

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.

Preparation and reactivity towards hydrazines of bis(cyanamide) and bis(cyanoguanidine) complexes of the iron triad

Bis(diethylcyanamide) [Fe(N≡CNEt2)2L4](BPh4)2 1a and bis(cyanoguanidine) [Fe{N≡CN(H)C(NH2)=NH}2L4](BPh4)2 1b [L = P(OEt)3] complexes were prepared by allowing iron(II) chloride to react first with an excess of P(OEt)3 and then of the appropriate cyanamide, followed by addition of an excess of NaBPh4. Instead, bis(complexes) of ruthenium and osmium [M(N≡CNEt2)2L4](BPh4)2 2a, 3a and [M{N≡CN(H)C(NH2)=NH}2L4](BPh4)2 2b, 3b (M = Ru 2, Os 3) were prepared by reacting hydrides MH2L4 first with either triflic acid HOTf or methyltriflate MeOTf and then with an excess of the appropriate cyanamide. Hydride-diethylcyanamide [MH(N≡CNEt2)L4]BPh4 4a, 5a and hydride-cyanoguanidine complexes [MH{N≡CN(H)C(NH2)=NH}L4](BPh4)2 4b, 5b (M = Ru 4, Os 5) were also obtained by reacting MH2L4 first with one equivalent of HOTf or MeOTf and then with the appropriate cyanamide. Treatment of bis(cyanamide) and bis(cyanoguanidine) complexes 1-3 with hydrazines RNHNH2 afforded hydrazinecarboximidamide derivatives [M{η(2)-N(H)=C(NEt2)N(R)NH2}L4](BPh4)2 6a-12a and [M{η(2)-N(H)=C[N=C(NH2)2]N(R)NH2}L4](BPh4)2 6b-12b (M = Fe 6-8, Ru 9, 10, Os 11, 12; R = H 6, 9, 11, Me 7, 10, 12, Ph 8). A reaction path involving nucleophilic attack by hydrazine on the cyanamide carbon atom is proposed. All the complexes were characterised by spectroscopy and X-ray crystal structure determination of [Os{η(2)-NH=C[N=C(NH2)2]N(CH3)NH2}{P(OEt)3}4](BPh4)2 12b.

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.

Hydrolysis of Coordinated Diazoalkanes To Yield Side-On 1,2-Diazene Derivatives

Diazoalkane complexes [Ru(η(5)-C5Me5)(N2CAr1Ar2)(PPh3){P(OR)3}]BPh4 [R = Me (1), Et (2); Ar1 = Ar2 = Ph (a); Ar1 = Ph, Ar2 = p-tolyl (b); Ar1Ar2 = C12H8 (c)] were prepared by allowing chloro complexes RuCl(η(5)-C5Me5)(PPh3)[P(OR)3] to react with diazoalkane Ar1Ar2CN2 in ethanol. The treatment of compounds 1 and 2 with H2O afforded 1,2-diazene derivatives [Ru(η(5)-C5Me5)(η(2)-NH═NH)(PPh3){P(OR)3}]BPh4 (3 and 4) and ketone Ar1Ar2CO. A reaction path involving nucleophilic attack by H2O on the coordinated diazoalkane is proposed. The complexes were characterized spectroscopically (IR and NMR) and by X-ray crystal structure determination of [Ru(η(5)-C5Me5)(η(2)-NH═NH)(PPh3){P(OMe)3}]BPh4 (3).

Azo Complexes of Osmium(II): Preparation and Reactivity of Organic Azide and Hydrazine Derivatives

Mixed-ligand hydride complexes OsHCl(CO)(PPh3)2L (2) [L = P(OMe)3, P(OEt)3] were prepared by allowing OsHCl(CO)(PPh3)3 (1) to react with an excess of phosphite P(OR)3 in refluxing toluene. Dichloro compounds OsCl2(CO)(PPh3)2L (3, 4) were also prepared by reacting 1, 2 with HCl. Treatment of hydrides OsHCl(CO)(PPh3)2L (2), first with triflic acid and then with an excess of RN3 afforded organic azide complexes [OsCl(η(1)-N3R)(CO)(PPh3)2L]BPh4 (5-7) [R = 4-CH3C6H4CH2, C6H5CH2, C6H5; L = P(OEt)3]. Benzylazide complexes react in CH2Cl2/ethanol solution, leading to the imine derivative [OsCl(CO){η(1)-NH═C(H)C6H4-4-CH3}(PPh3)2{P(OEt)3}]BPh4 (8b). Hydrazine complexes [OsCl(CO)(RNHNH2)(PPh3)2L]BPh4 (9-11) [R = H, CH3, C6H5; L = P(OMe)3, P(OEt)3] were prepared by allowing hydride species OsHCl(CO)(PPh3)2L (2) to react first with triflic acid and then with an excess of hydrazine. Aryldiazene derivatives [OsCl(CO)(ArN═NH)(PPh3)2L]BPh4 (12, 13) were also prepared following two different methods: (i) by oxidizing arylhydrazine [OsCl(C6H5NHNH2)(CO)(PPh3)2L]BPh4 (11) with Pb(OAc)4 in CH2Cl2 at -30 °C; (ii) by allowing hydride species OsHCl(CO)(PPh3)2L (2) to react with aryldiazonium cations ArN2(+) (Ar = C6H5, 4-CH3C6H4) in CH2Cl2. The complexes were characterized spectroscopically and by X-ray crystal structure determination of OsHCl(CO)(PPh3)2[P(OEt)3] (2b) and [OsCl{η(1)-NH═C(H)C6H4-4-CH3}(CO)(PPh3)2{P(OEt)3}]BPh4 (8b).

Preparation of bis(aryldiazene) and new aryldiazenido complexes of rhenium

Abstract Mixed-ligand hydride ReH 2 (NO)L(PPh 3 ) 2 complexes [L=P(OEt) 3 or PPh(OEt) 2 ] were prepared by allowing the ReH 2 (NO)(PPh 3 ) 3 species to react with an excess of phosphite. Treatment of ReH 2 (NO)L(PPh 3 ) 2 hydrides with an equimolar amount of aryldiazonium cations ArN 2 + gives the mono-aryldiazene [ReH(ArNNH)(NO)L(PPh 3 ) 2 ]BPh 4 complexes (Ar=C 6 H 5 , 4-CH 3 C 6 H 4 ), while treatment with an excess of ArN 2 + yields bis(aryldiazene) [Re(ArNNH) 2 (NO)L(PPh 3 ) 2 ](BPh 4 ) 2 derivatives. Binuclear [{ReH(NO)L(PPh 3 ) 2 } 2 (μ-HNNArArNNH)](BPh 4 ) 2 and [{Re(4-CH 3 C 6 H 4 NNH)(NO)L(PPh 3 ) 2 } 2 (μ-HNNArArNNH)](BPh 4 ) 4 complexes (ArAr=4,4′-C 6 H 4 C 6 H 4 , 4,4′-C 6 H 4 CH 2 C 6 H 4 ) were also prepared. The reaction of the triphenylphosphine ReH 2 (NO)(PPh 3 ) 3 complex with aryldiazonium cations was studied and led exclusively to mono-aryldiazene [ReH(ArNNH)(NO)(PPh 3 ) 3 ]BPh 4 and [{ReH(NO)(PPh 3 ) 3 } 2 (μ-HNNArArNNH)](BPh 4 ) 2 derivatives. The complexes were characterised spectroscopically (IR, NMR) using the 15 N-labelled derivatives. The aryldiazenido [ReH(C 6 H 5 N 2 ){PPh(OEt) 2 } 4 ]BPh 4 complex was prepared by allowing trihydride ReH 3 [PPh(OEt) 2 ] 4 to react with phenyldiazonium tetrafluoroborate. A reaction path involving the aryldiazene [ReH 2 (C 6 H 5 NNH){PPh(OEt) 2 } 4 ] + intermediate was also proposed.

Preparation of acetylide and propadienylidene complexes of iron(II)

Abstract Depending on the nature of the phosphine ligands, the reaction of phosphite-containing FeCl2 solutions with propargylic alcohols HCCCRR′(OH) affords propadienylidene [Fe(CCCPh2){P(OEt)3}5](BPh4)2 and [FeCl(CCCPh2){PPh(OEt)2}4]BPh4 complexes and acetylide [Fe{CCCRR′(OH)}{P(OEt)3}5]BPh4 derivatives (R=R′=Ph; R=Me, R′=Ph). In contrast, the reaction of phosphite-containing FeCl2 solutions with terminal alkynes RCCH affords mononuclear [Fe(CCPh){P(OEt)3}5]BPh4 and binuclear [{Fe[P(OEt)3]5}2(μ-1,4-CCC6H4CC)](BPh4)2 acetylide derivatives. All the new complexes were characterised by IR and 1H, 31P and 13C NMR data, and a geometry in solution was also established.