Synthesis, characterization and redox behaviour of benzoyldiazenido- and oxorhenium complexes bearing N,N- and S,S-type ligands

The reactions of [ReCl₂{η²-N₂C(O)Ph}(PPh₃)₂] (1) with 2-aminopyrimidine (H₂Npyrm), 2,2′-bipyridine (bpy) and tetraethylthiuram disulfide (tds), in MeOH upon reflux, lead to the new η¹-(benzoyldiazenido)rhenium(III) complexes [ReCl{η¹-N₂C(O)Ph}(HNpyrm)(PPh₃)₂] (2) and [ReCl₂{η¹-N₂C(O)Ph}(bpy)(PPh₃)] (3), and the known oxo(diethyldithiocarbamato)dirhenium(v) complex [Re₂O₂(μ-O){Et₂NC(S)S}₄] (4), respectively. The Et₂NC(S)S ligands in 4 result from S-S bond rupture of tds molecules. The obtained compounds have been characterized by IR, ¹H, ³¹P{¹H} and ¹³C{¹H} NMR spectroscopies, FAB⁺-MS, elemental and single-crystal X-ray diffraction (for 2 and 4) analyses. Complex 2 represents the first structurally characterized Re compound derived from 2-aminopyrimidine. Besides, the redox behaviour of 2-4 in CH₂Cl₂ solution has been studied by cyclic voltammetry, and the Lever electrochemical ligand parameter (E_L) has been estimated, for the first time, for HNpyrm. The electrochemical results are discussed in terms of electronic properties of the Re centres and the ligands.     

Synthesis, characterization and molecular structures of the trichloro-η-benzoyldiazenido [ReCl3{η-NNC(O)Ph}(PPh3)2] and oxorhenium [ReOCl2(OMe)(PPh3)2] complexes derived from reactions of [ReCl2{η-NNC(O)Ph}(PPh3)2] with a peroxide or dioxygen

The reactions of [ReCl₂{η²-NNC(O)Ph}(PPh₃)₂] (1) with t-BuOOH, in C₆H₆ or chlorinated solvents, at room temperature or with MeOH upon reflux in air lead to the trichloro-η¹-benzoyldiazenido [ReCl₃{η¹-NNC(O)Ph}(PPh₃)₂] (2) or the methoxy-oxo [ReOCl₂(OMe)(PPh₃)₂] (3) compound, respectively, which have been characterized by spectroscopic and FAB⁺-MS methods, elemental and single crystal X-ray diffraction analyses. They show distorted octahedral coordinaiton geometries with trans triphenylphosphine ligands, an essentially linear η¹-diazenido moiety in 2 and the methoxy group in 3 in trans position to the oxo ligand.     

Rhenium(III) and rhenium(V) complexes stabilized by the potentially tetradentate ligand tris(2-diphenylphosphinoethyl)amine

The reaction of the rhenium(V) nitrido complex [Re(N)Cl₂(PPh₃)₂] with the tripodal ligand N(CH₂CH₂PPh₂)₃ (NP₃) in THF gave [Re(N)Cl₂(η²-P,P-NP₃)] (1) in which NP₃ acts as a tridentate ligand using the nitrogen and two phosphorus donors for coordination. Refluxing 1 in a polar solvent such as ethanol produced [(η⁴-NP₃)Re(N)Cl]Cl (2) in which NP₃ acts as a tetradentate ligand. Treatment of complex [Re(O)Cl₃(AsPh₃)₂] containing the [ReO]³⁺ core with NP₃ in THF yielded [ReCl₃{η³-N,P,P-(N{CH₂CH₂Ph₂}₂{CH₂CH₂P(O)Ph₂})}] (3). Complexes 1 and 3 have been characterized by single-crystal X-ray analyses.     

Rhenium(III) and technetium(III) complexes with 2-mercapto-1,3-azole ligands and X-ray crystal structures

Reactions of labile [MCl₃(PPh₃)₂(NCMe)] (M = Tc, Re) precursors with 1H-benzoimidazole-2-thiol (H₂L¹), 5-methyl-1H-benzoimidazole-2-thiol (H₂L²) and 1H-imidazole-2-thiol (H₂L³), in the presence of PPh₃ and [AsPh₄]Cl gave a new series of trigonal bipyramidal M(III) complexes [AsPh₄]{[M(PPh₃)Cl(H₂L^1-3)₃]Cl₃} (M = Re, 1-3; M = Tc, 4-6). The molecular structures of 1 and 3 were determined by X-ray diffraction. When the reactions were carried out with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵), neutral paramagnetic monosubstituted M(III) complexes [M(PPh₃)₂Cl₂(L^4,5)] (M = Re, 8, 9; M = Tc, 10, 11) were obtained. In these compounds, the central metal ions adopt an octahedral coordination geometry as authenticated by single crystal X-ray diffraction analysis of 8 and 11. Rhenium and technetium complexes 1, 4 and rhenium chelate compounds 8, 9 have been also synthesized by reduction of [MO₄]⁻ with PPh₃ and HCl in the presence of the appropriate ligand. All the complexes were characterized by elemental analyses, FTIR and NMR spectroscopy.     

Preparation of benzophenone imine complexes of transition metals

Benzophenone imine [M(η¹-NHCPh₂)(CO)_nP_5-n]BPh₄ [M = Mn, Re; n = 2, 3; P = P(OEt)₃, PPh(OEt)₂, PPh₂OEt, PPh₃] complexes were prepared by allowing triflate M(κ¹-OTf)(CO)_nP_5-n compounds to react with an excess of the imine. Hydride-imine [MH(η¹-NHCPh₂)P₄]BPh₄ (M = Ru, Os), triflate-imine [Os(κ¹-OTf)(η¹-NHCPh₂)P₄]BPh₄ and bis(imine) [Ru(η¹-NHCPh₂)₂P₄](BPh₄)₂ [P = P(OEt)₃] derivatives were also prepared. The complexes were characterized spectroscopically (IR, ¹H, ³¹P, ¹³C NMR) and a geometry in solution was also established. Hydride-benzophenone imine [IrHCl(η¹-NHCPh₂)L(PPh₃)₂]BPh₄and [IrHCl(η¹-NHCPh₂)L(AsPh₃)₂]BPh₄ [L = P(OEt)₃ and PPh(OEt)₂] complexes were prepared by reacting hydride IrHCl₂L(PPh₃)₂ and IrHCl₂L(AsPh₃)₂ precursors with an excess of imine. Dihydride IrH₂(η¹-NHCPh₂)(PPh₃)₃ complex was also obtained and a geometry in solution was proposed.     

Synthesis, molecular structure, substitution and C-C coupling reactions of ruthenium complexes containing (η-C9H7)Ru(PPh3) as a molecular unit

The 2-methallyl complex [(η⁵-C₉H₇)Ru(η³-2-MeC₃H₄)(PPh₃)] (3), prepared from [(η⁵-C₉H₇)Ru(PPh₃)₂Cl] (2) and 2-MeC₃H₄MgCl, reacts with HX (X = Cl, CF₃CO₂) in the presence of ethene to give the chiral-at-metal compounds [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)X] (4, 5) in nearly quantitative yields. Treatment of 2 with AgPF₆ and ethene affords [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)₂]PF₆ (6), which reacts with acetone to give the substitution product [(η⁵-C₉H₇)Ru(OCMe₂)(PPh₃)₂]PF₆ (7). The molecular structure of 7 has been determined crystallographically. Whereas treatment of 4 with CH(CO₂Et)N₂ yields the olefin complex [(η⁵-C₉H₇)Ru{η²-(Z)-C₂H₂(CO₂Et)₂}(PPh₃)Cl] (8), the reactions of 4 and 5 with Ph₂CN₂, PhCHN₂ and (Me₃Si)CHN₂ lead to the formation of the carbeneruthenium(II) derivatives [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)Cl] (9-11) and [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)(κ¹-O₂CCF₃)] (12-14), respectively. Treatment of 9 (R = R′ = Ph), 10 (R = H, R′ = Ph) and 11 (R = H, R′ = SiMe₃) with MeLi produces the hydrido(olefin) complexes [(η⁵-C₉H₇)RuH(η²-CH₂CPh₂)(PPh₃)] (15), [(η⁵-C₉H₇)RuH(η²-CH₂CHPh)(PPh₃)] (18a,b) and [(η⁵-C₉H₇)RuH(η²-CH₂CHSiMe₃)(PPh₃)] (19) via C-C coupling and β-hydride shift. The analogous reactions of 11 with PhLi gives the η³-benzyl compound [(η⁵-C₉H₇)Ru{η³-(Me₃Si)CHC₆H₅}(PPh₃)] (20). The η³-allyl complex [(η⁵-C₉H₇)Ru(η³-1-PhC₃H₄)(PPh₃)] (17) was prepared from 10 and CH₂CHMgBr by nucleophilic attack.     

Rhodium and iridium complexes bearing an alkyloxazoline-substituted indenyl ligand (Indox ligand) and their stereoselective construction of metal-centered chirality

The Indox ligands, [{(S)-(ⁱPr)Indox}_n]H (1) [n=2 (a), 3 (b)] and [{(H)Indox}_n=3]H (2), in which an indenyl group and an oxazoline ring are connected by an ethylene or propylene spacer, have been prepared. Reaction of [Ir(coe)₂Cl]₂ or [RhCl(C₂H₄)₂]₂ with the potassium salt of 1 afforded η⁵-[{(S)-(ⁱPr)Indox}_n]Ir(coe)₂ (3) or η⁵-[{(S)-(ⁱPr)Indox}_n]Rh(C₂H₄)₂ (6) as a 1:1 mixture of two diastereomers. The oxazoline ring in 3 and 6 did not coordinate to the metal center. When the complexes 3 or 6 reacted with iodine in diethyl ether, oxidative addition proceeded and the oxazoline ring coordinated to the metal center to give diiodoiridium(III) or rhodium(III) complexes, η⁵:η¹-[{(S)-(ⁱPr)Indox}_n]M(I)₂ [M=Ir (4), Rh (7)]. The corresponding diiodoiridium(III) complex bearing the Indox ligand 2, η⁵:η¹-[{(H)Indox}_n=2]Ir(I)₂ (5), was also prepared by a similar method. Reaction of 4 or 7 with PPh₃ in THF afforded diiodo-phosphine complexes, η⁵-[{(S)-(ⁱPr)Indox}_n]M(PPh₃)(I)₂ [M=Ir (8), Rh (9)] as a 1:1 mixture of two diastereomers in which the oxazoline ring dissociated from the metal center. The related reaction of 8 or 9 with more than 2 equiv. of AgOTf afforded the cationic complexes, [η⁵:η¹-[{(S)-(ⁱPr)Indox}_n]M(PPh₃)(OTf)]OTf [M=Ir (10), Rh (11)], having a stereogenic center at the metal center as a mixture of only two diastereomers. From ¹H and ³¹P NMR analyses, each diastereomer of 8 or 9 afforded only a single isomer of 10 or 11. The corresponding iridium(III) complex bearing the Indox ligand 2, [η⁵:η¹-[{(H)Indox}_n=3]Ir(PPh₃)(OTf)]OTf (12) was also prepared. The coordinated triflate ligand of 12 was slowly replaced by water in CDCl₃ to afford the dicationic aquo complex, (S^*_pl,R^*_Ir)-[η⁵:η¹-[{(H)Indox}_n=3]Ir(PPh₃)(H₂O)](OTf)₂ (13). The monocationic complex, [η⁵:η¹-[{(S)-(ⁱPr)Indox}_n=2]Ir(PPh₃)(I)]OTf (14a), having metal-centered chirality, was observed as a mixture of only two diastereomers in the reaction of 10a (a mixture of two diastereomers) with 1 equiv. of AgOTf. These observations indicated that the ligand exchange reaction of 8 or 9 with AgOTf contained the following three steps: (i) abstraction of one of the two prochiral iododes by AgOTf, (ii) recoordination of the oxazoline ring, and (iii) exchange of the remaining iodide for the triflate by AgOTf. The stereochemistry around the metal center was determined at the second step. All complexes have been characterized by usual spectroscopic methods as well as elemental analyses, and 4 and 13 have been characterized by X-ray analyses.     

Complexes of N-thiophosphorylthioureas RNHC(S)NHP(S)(OiPr)2 (HL) (R = pyridin-2-yl, pyridin-3-yl, 6-amino-pyridin-2-yl) with copper(I): Crystal structures of Cu(PPh3)nL (n = 1, 2)

Reaction of the potassium salts of N-thiophosphorylated thioureas of common formula RNHC(S)NHP(S)(OiPr)₂ [R = pyridin-2-yl (HL^a), pyridin-3-yl (HL^b), 6-amino-pyridin-2-yl (HL^c)] with Cu(PPh₃)₃I in aqueous EtOH/CH₂Cl₂ leads to mononuclear [Cu(PPh₃)₂L^a,b-S,S′] (1, 2) and [Cu(PPh₃)L^c-S,S′] (3) complexes. Using copper(I) iodide instead of Cu(PPh₃)₃I, polynuclear complexes [Cu_n(L-S,S′)_n] (4-6) were obtained. The structures of these compounds were investigated by IR, ¹H, ³¹P{¹H} NMR spectroscopy, ES-MS and elemental analyses. The crystal structures of Cu(PPh₃)₂L^b (2) and Cu(PPh₃)L^c (3) were determined by single-crystal X-ray diffraction.     

Diazo complexes of osmium: preparation of binuclear derivatives with bis(aryldiazene) and bis(aryldiazenido) bridging ligands

Depending on experimental conditions and the nature of the phosphite, the reaction of OsH₂P₄ [P=P(OEt)₃ and PPh(OEt)₂] with bis(aryldiazonium) salts [N₂Ar-ArN₂](BF₄)₂ [Ar-Ar=4,4^′-C₆H₄-C₆H₄, 4,4^′-(2-CH₃)C₆H₃-C₆H₃(2-CH₃), 4,4^′-C₆H₄-CH₂-C₆H₄ and 1,5-C₁₀H₆] afford the cis and the trans binuclear [{OsHP₄}₂(μ-HNNAr-ArNNH)](BPh₄)₂1, 2 aryldiazene derivatives. These complexes 1, 2 further react with the mono(diazonium) (4-CH₃C₆H₄N₂)BF₄ salt to give the bis(aryldiazene) [{Os(4-CH₃C₆H₄NNH)P₄}₂(μ-HNNAr-ArNNH)](BPh₄)₄3, 4 derivatives. Binuclear bis(aryldiazenido) [{OsP₄}₂(μ-N₂Ar-ArN₂)](BPh₄)₂ (6) [P=P(OEt)₃; Ar-Ar=4,4^′-C₆H₄-C₆H₄, 4,4^′-C₆H₄-CH₂-C₆H₄] complexes were prepared by deprotonating with NEt₃ the nitrile-diazene [{Os(4-CH₃C₆H₄CN)P₄}₂(μ-HNNAr-ArNNH)](BPh₄)₄ (5) derivatives. The aryldiazenido compounds 6 react with HCl to give the new aryldiazene [{OsClP₄}₂(μ-HNNAr-ArNNH)](BPh₄)₂ (7) derivatives. The characterisation of the complexes by IR and ¹H, ³¹P, ¹⁵N NMR data is also discussed. The reaction of the hydride OsH₂(PPh₂OEt)₄ with mono(diazonium) salts was also studied and led exclusively to the mono(aryldiazene) [OsH(ArN NH)(PPh₂OEt)₄]BPh₄ (8) (Ar=C₆H₅, 4-CH₃C₆H₄) derivatives. Spectroscopic data (¹H, ³¹P, ¹⁵N NMR) on ¹⁵N-labelled derivatives suggest the presence of two isomers with the N-bonded and the π-bonded ArNNH ligand, respectively.     

Synthesis and characterisation of a series of 1,2-phenylenedioxoborylcyclopentadienyl-metal complexes [Ti(IV), Zr(IV), Hf(IV), La(III), Ce(III), Yb(III), Sn(II) and Fe(II)]

The preparation of a series of 1,2-phenylenedioxoborylcyclopentadienyl-metal complexes is described. These are of formula [M{η⁵-C₅H₄(BX)}Cl₃] [M = Ti and X = CAT (2a), CAT^t (2b) or CAT^tt (2c); X = CAT^tt and M = Zr (4a) or Hf (4b)], [M{η⁵-C₅H₄(BX)}₂Cl₂] [M = Zr, X = CAT (3a) or CAT^t (3c); or M = Hf, X = CAT (3b) or CAT^t (3d)], [M{(μ-η⁵-C₅H₃BCAT)₂ SiMe₂}Cl₂] [M = Zr (5a) or Hf (5b)], [M{η⁵-C₅H₃(BCAT)₂}Cl₃] [M = Zr (6a) or Hf (6b)], [M{η⁵-C₅H₄BCAT}₃(THF)] [M = La (7a), Ce (7b) or Yb (7c)], [Sn{η⁵-C₅ H₄(BCAT^t)}Cl](8) and [Fe{η⁵-C₅H₄(BCAT^t)}₂] (9). The abbreviations refer to BO₂C₆H₄-1,2 (BCAT) and the 4-Bu^t (BCAT^t) and the (BCAT^tt) analogues. The compounds 2a-9 have been characterised by microanalysis, multinuclear NMR and mass spectra. The single crystal X-ray structure of the lanthanum compound 7a is presented.     

Phosphorus-carbon bond formation via reactions of triphenylphosphine with acetylene and pentamethylcyclopentadienyl coordinated to iridium(III)

Phosphorus-carbon bond is formed via: (i) the apparent HCCH insertion into Ir-P bond to produce Ir-CHCH-PPh₃ group and (ii) the activation of the ring-methyl group of the coordinated Cp^* (C₅Me₅ ⁻) to produce Ir(η⁵-C₅Me₄CH₂-PPh₃) group from reactions of iridium(III)-Cp^* complexes, [Cp^*IrL₃]ⁿ⁺ (n=1, 2); Cp^*=C₅Me₅ ⁻; L₃=Cl(PPh₃)₂ (3), (CH₃CN)₃ (5). The following new P-C bond containing iridium(III) complexes have been prepared: [Cp^*Ir(-CHCH-PPh₃)Cl(PPh₃)]⁺ (4) from 3 with HCCH; [Ir(η⁵-C₅Me₄CH₂-PPh₃)(H)(PPh₃)₂]²⁺ (6) from 5 with PPh₃; [Cp^*Ir(-CHCH-PPh₃)₂(PPh₃)]²⁺ (7) from 5 with HCCH and PPh₃; [Ir(η⁵-C₅Me₄CH₂-PPh₃)(-CHCH-PPh₃)Cl(PPh₃)]²⁺ (8) from [Ir(η⁵-C₅Me₄CH₂-PPh₃)(Cl)(PPh₃)₂]²⁺ (6-Cl) with HCCH; [Ir(η⁵-C₅Me₃(1,3-CH₂-PPh₃)₂(H)(PPh₃)₂)]³⁺ (10) from [Ir(η⁵-C₅Me₄CH₂-PPh₃)(NCCH₃)₂(PPh₃)]³⁺ (9) with PPh₃; [Ir(η⁵-C₅Me₄CH₂-PPh₃)(-CHCH-PPh₃)₂(PPh₃)]³⁺ (11) from 9 with HCCH and PPh₃.     

Preparation of trihydridostannyl complexes of rhenium stabilised by isocyanide ligands

Mixed-ligand complexes [ReBr(CO)₂(CNR)_nL_3−n] (1-4) [R = 4-CH₃OC₆H₄, 4-CH₃C₆H₄, C(CH₃)₃; L = P(OEt)₃, PPh(OEt)₂; n = 1, 2] were prepared by allowing carbonyl compounds [ReBr(CO)₄L] and [ReBr(CO)₃L₂] to react with an excess of isocyanide. Treatment of these bromocomplexes [ReBr(CO)₂(CNR)_nL_3−n] with SnCl₂ · 2H₂O yielded the trichlorostannyl derivatives [Re(SnCl₃)(CO)₂(CNR)_nL_3−n] (5-8). Trihydridestannyl complexes [Re(SnH₃)(CO)₂(CNR)_nL_3−n] (9-12) were prepared by allowing trichlorostannyl compounds 5-8 to react with NaBH₄ in ethanol. The trimethylstannyl derivative [Re(SnMe₃)(CO)₂(CNC₆H₄-4-CH₃){PPh(OEt)₂}₂] (13b) was also prepared by treating [Re(SnCl₃)(CO)₂(CNC₆H₄-4-CH₃){PPh(OEt)₂}₂] with an excess of MgBrMe in diethylether. Reaction of the tin trihydride complexes [Re(SnH₃)(CO)₂(CNR)_nL_3−n] (9-12) with CO₂ (1 atm) led to dinuclear OH-bridging bis(formate) derivatives [Re{Sn(OC(H)O)₂(μ-OH)}(CO)₂(CNR)_nL_3−n]₂ (14, 15). The complexes were characterised spectroscopically (IR, ¹H, ³¹P, ¹³C, ¹¹⁹Sn NMR) and by X-ray crystal structure determination of [Re(SnH₃)(CO)₂{CNC(CH₃)₃}{PPh(OEt)₂}₂] (10b).     

Synthesis and cyclization reactions of platinum(II)-coordinated arsonium-substituted phenyl isocyanides, o-(IR3As-CH2)C6H4NC

The arsonium-substituted isocyanides, o-(I⁻⁺R₃AsCH₂)C₆H₄NC (AsR₃=AsPh₃, L₁; AsMePh₂, L₂; AsMe₂Ph, L₃), were prepared by reaction of o-(chloromethyl)phenyl isocyanide, o-(CH₂Cl)C₆H₄NC, with a slight molar stoichiometric amount of the arsine in the presence of a 3-fold excess of NaI in acetone at room temperature. The isocyanides L₁-L₃ coordinate to some Pt(II) complexes such as trans-[PtX{o-(I⁻⁺R₃AsCH₂)C₆H₄NC}(PPh₃)₂] [BF₄] (AsR₃=AsPh₃, 1; AsMePh₂, 2; AsMe₂Ph, 3; X=Cl, I) and [PtX{o-(I⁻⁺R₃AsCH₂)C₆H₄NC}(Ph₂PCHCHPPh₂)] [BF₄] (AsR₃=AsMePh₂, 4; X=Cl, I). Complexes 2-4 are converted in CH₂Cl₂ at room temperature in the presence of NEt₃ to the corresponding indolidin-2-ylidene derivatives trans-[PtX{(AsR₃)}(PPh₃)₂]BF₄] (AsR₃=AsPh₃, 5; AsMePh₂, 6; AsMe₂Ph, 7) and [PtX{(AsMePh₂)}(Ph₂PCHCHPPh₂)][BF₄] (8).     

Synthesis of the manganese-monocarbollide dianion [1-NHBu-2,2,2-(CO)3-closo-2,1-MnCB10H10]: Reactions with transition metal cations

Reaction of [Mn(NCMe)₃(CO)₃][PF₆] with Li₃[7-NHBu^t-nido-7-CB₁₀H₁₀] in THF (THF = tetrahydrofuran) affords the twelve-vertex manganacarborane dianion [1-NHBu^t-2,2,2-(CO)₃-closo-2,1-MnCB₁₀H₁₀]²⁻, isolated as the bis-[N(PPh₃)₂]⁺ salt (5a). This species reacts with {Pt(dppe)}²⁺ (dppe = Ph₂PCH₂CH₂PPh₂) to afford the bimetallic complex [1-NH₂Bu^t-2,3-{Pt(dppe)}-2,2,2-(CO)₃-closo-2,1-MnCB₁₀H₉] (7) which has an Mn-Pt bond. In contrast, with {Cu(PPh₃)}⁺ the anion of 5a yields a CuMnCu trimetallic compound [1-{NH(Bu^t)Cu(PPh₃)}-2,3,7-{Cu(PPh₃)}-3,7-(μ-H)₂-2,2,2-(CO)₃-closo-2,1-MnCB₁₀H₈] (8) in which one of the Cu centers is bonded to Mn, whilst the other is attached to the pendant NHBu^t group. Upon treatment with Ag⁺, compound 5a is oxidized giving the very unusual Mn(III)-carbonyl complex [1,2-μ-NHBu^t-2,2,2-(CO)₃-closo-2,1-MnCB₁₀H₁₀] (9a) in which the carborane ligand formally acts as an eight-electron donor to manganese. The novel structural features of compounds 7, 8, and 9a have been confirmed by X-ray diffraction studies.     

Strong 1,4 P-O intramolecular interactions as a source of conformational preferences in α-stabilised phosphorus ylides. Part 2: metallic complexes

The complexes cis-[PdCl₂{η²-[C(H)PH₃]₂CO}] (2) in two different stereochemical arrangements (cisoid-cisoid, 2cc; cisoid-transoid, 2ct) have been studied by DFT methods at the B3LYP level. The (2cc) structure is energetically more stable than the (2ct), being the main responsible of the energy difference between the two complexes the energetic gap between the cc and ct isomers of the free bis-ylide ligand [H₃PC(H)-C(O)-C(H)PH₃] (1). In (1) these differences arise from the presence of 1,4-intramolecular interactions between the phosphorus atoms and the carbonyl oxygen. That is, the conformational preferences observed in (1) due to the establishment of 1,4-P?O interactions are directly transferred to the metallic complexes (2) in such a way that the most stable structure for the free ligand gives the most stable complex. In the absence of the carbonyl group (e.g. [H₃PC(H)-C(CH₂)-C(H)PH₃] (3) or [H₃PC(H)-CH₂-C(H)PH₃] (5)) all isomers of a given bis-ylide (cc, ct and tt) become isoenergetic. The absence of discrimination in the free bis-ylides (3) and (5) gives isoenergetic cc and ct structures for the corresponding complexes cis-[PdCl₂{η²-[C(H)PH₃]₂CCH₂}] (4), cis-[PdCl₂{η²-[C(H)PH₃]₂CH₂}] (6) and [CpNi{η²-[C(H)PH₃]₂CH₂}] (7), as stated by NMR spectroscopy for (7). The influence of other factors (change of the heteroatom at C_β, change of the P substituents) in the energy of the different isomers of the bis-ylides and in the energy of the corresponding complexes has also been studied and discussed.     

Methyl- and propylacetamidinates of lanthanides: Structures, catalytic and some physical properties

The acetamidinates {[MeNC(Me)NMe]₂Ln}₂[μ-η²-η²-MeNC(Me)NMe]₂ (Ln = Y (1), Dy (2)) and {[PrⁿNC(Me)NPrⁿ]₂Y}₂[μ-η²-η²-PrⁿNC(Me)NPrⁿ]₂ (3) have been prepared by the reactions of amides Ln[N(SiMe₃)₂]₃ with respective N,N′-disubstituted amidines MeNC(Me)NHMe or PrⁿNC(Me)NHPrⁿ. The reaction of Er[N(SiMe₃)₂]₃ with excess of monosubstituted amidine HNC(Me)NHPrⁱ or in a ratio of 1:2 resulted in the formation of compound {Er[NC(Me)NHPrⁱ]₃}_x (4). The same reaction with 1:1 ratio yielded heteroleptic complex {Er[N(SiMe₃)₂]₂[NC(Me)NHPrⁱ]}_x (5). The complexes 1, 2 and 3 have similar structures and contain four terminal and two μ-η²:η²-N,N-bridging amidinate groups binding the metal atoms. Volatility of 1, 2 and 3 is comparable to that of known monomeric La[PrⁱNC(R)NPrⁱ]₃. Compound 1 efficiently catalyzes the ring-opening polymerization of rac-lactide to give polylactide with M_n 53 085 and polydispersity 1.84.     

Coordination chemistry of Re complexes with 2(2′-pyridyl)benzimidazole

Two new Re(III) and Re(IV) complexes with 2(2′-pyridyl)benzimidazole (pbimz) were prepared and their crystal and molecular structures established by single-crystal X-ray diffraction. Reaction of [ReOCl₂(OEt)(PPh₃)₂] with the ligand gave red cis(Cl),trans(P)-[ReCl₂(PPh₃)₂(pbimz)]Cl (1), while red [ReCl₄(pbimz)] · OPPh₃ (2) was obtained from [ReCl₃(PhC(O)C(O)Ph)(PPh₃)] and pbimz in the presence of perchlorate. The compounds were characterized by elemental analysis, FAB-MS, UV-Vis, IR, NMR spectroscopy and magnetic susceptibility measurements.     

Reaction of [MCl2(CH3CN)2] (M = Pd(II), Pt(II)) compounds with N1-alkylpyridylpyrazole-derived ligands

Palladium(II) and platinum(II) complexes with N-alkylpyridylpyrazole-derived ligands, 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L¹) and 2-(1-octyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L²), cis-[MCl₂(L)] (M = Pd(II), Pt(II)), have been synthesised. Treatment of [PdCl₂(L)] (L = L¹, L²) with excess of ligand (L¹, L²), pyridine (py) or triphenylphosphine (PPh₃) in the presence of AgBF₄ and NaBPh₄ produced the following complexes: [Pd(L)₂](BPh₄)₂, [Pd(L)(py)₂](BPh₄)₂ and [Pd(L)(PPh₃)₂](BPh₄)₂. All complexes have been characterised by elemental analyses, conductivity, IR and NMR spectroscopies. The crystal structures of cis-[PdCl₂(L²)] (2) and cis-[PtCl₂(L¹)] (3) were determined by a single crystal X-ray diffraction method. In both complexes, the metal atom is coordinated by one pyrazole nitrogen, one pyridine nitrogen and two chlorine atoms in a distorted square-planar geometry. In complex 3, π-π stacking between pairs of molecules is observed.     

Two novel oxomolybdenum complexes derived from the reaction of chlorotrisulfidomolybdate precursor with a pyridine-containing tridentate ligand

Reaction of chlorotrisulfidomolybdate [PPh₄][MoClS₃] (1) with one equivalent of tridentate ligand PyCH₂NHC₂H₄SNa (PyNSNa) in THF generated both a mononuclear and a dinuclear complexes, [PPh₄][(PyNS)MoO(η²-S₂)₂] (2) and [PPh₄][(PyNS)Mo(O)(μ-S)₂Mo(S)(η²-S₂)]·0.5MeCN (3·0.5MeCN). These two complexes were separated mechanically and fully characterized using IR, UV/Vis spectra, ¹H NMR spectra and X-ray single crystal diffraction analysis. In both complexes, one terminal sulfido ligand was substituted by one oxo group. In complex 3, two types of intermolecular hydrogen bonding in its solid state led to a 1-D structure in which each unit was a dimmer formed via hydrogen bonding.     

Synthesis and characterization of tetrairon-tungsten cluster complex containing a μ4, η-carbonyl ligand

Reaction of [(PPh₂C₅H₄)Cp₃Fe₄(CO)₄] (1) with (CO)₄W(CH₃CN)₂ at ambient temperature affords [(CO)₄W(PPh₂C₅H₄)Cp₃Fe₄(CO)₄] (2) as the major product, together with a small amount of [(CO)₅W(PPh₂C₅H₄)Cp₃Fe₄(CO)₄] (3). Compound 3 can be obtained in good yield by treating (CO)₅W(CH₃CN) with equal molar of 1, and reaction of 3 with Me₃NO in acetonitrile solvent produces 2 exclusively. The crystal structures of 2 and 3 have been determined by an X-ray diffraction study. Compound 2 contains an interesting μ₄, η²-CO ligand, where two electrons donated by the carbon atom are involved to bridge a Fe₃ face and two electrons from oxygen are donated to the tungsten(0) atom.