Synthesis and characterization of cyclometallated palladium(II) and platinum(II) complexes with amide-thiolate ligands

The redox reaction of bis(2-benzamidophenyl) disulfide (H₂L-LH₂) with [Pd(PPh₃)₄] in a 1:1 ratio gave mononuclear and dinuclear palladium(II) complexes with 2-benzamidobenzenethiolate (H₂L⁻), [Pd(H₂L-S)₂(PPh₃)₂] (1) and [Pd₂(H₂L-S)₂ (μ-H₂L-S)₂(PPh₃)₂] (2). A similar reaction with [Pt(PPh₃)₄] produced only the corresponding mononuclear platinum(II) complex, [Pt(H₂L-S)₂(PPh₃)₂] (3). Treatment of these complexes with KOH led to the formation of cyclometallated palladium(II) and platinum(II) complexes, [Pd(L-C,N,S)(PPh₃)]⁻ ([4]⁻) and [Pt(L-C,N,S) (PPh₃)]⁻ ([5]⁻). The molecular structures of 2, 3 and [4]⁻ were determined by X-ray crystallography.     

Synthesis and characterization of platinum and palladium pyrrolidinedithiocarbamate complexes

Treatment of (PPh₃)₂MCl₂ (M = Pd or Pt) with ammonium pyrrolidinedithiocarbamate (NH₄S₂CNC₄H₈) in a 1:1 molar ratio gave (PPh₃)M(Cl)(κ ² S,S-S₂CNC₄H₈) [M = Pt (1), Pd (2)]. On the other hand, the interaction of these compounds in a 1:2 [M:L] molar ratio gave (PPh₃)Pt(κS-S₂CNC₄H₈)(κ ² S,S-S₂CNC₄H₈) (3), which contains both terminal and chelated dithiocarbamato ligands, or a yellow insoluble solid for M = Pd. The bis(diphenylphosphino)ethane platinum or palladium dichlorides [(dppe)MCl₂] reacted with the same ligand to give the salts [(dppe)M(κ ² S,S-S₂CNC₄H₈)]Cl (M = Pt (4), Pd (5) which have only one chelating dithiocarbamato ligand. The new compounds were characterized by ¹H-, ¹³C{¹H}- and ³¹P-n.m.r. spectroscopy, mass spectrometry, elemental analysis and X-ray single crystal structure analysis.     

Allyl palladium dithiocarbamates and related dithiolate complexes as precursors to palladium sulfides

Allyl-palladium dithiocarbamate complexes, [Pd(allyl)(S₂CNR₂)], have been prepared from the addition of dithiocarbamate salts to [Pd(allyl)(μ-Cl)]₂ and TGA and DSC studies have been carried out in order to assess their potential as MOCVD precursors to palladium sulfides. For comparison [(η³-C₄H₇)Pd(S₂PPh₂)] and [Pd(S₂CNMeR)₂] (R = Bu, Hex) have also been prepared and tested as precursors. The unsymmetrical dithiocarbamate complex, [(η³-C₃H₅)Pd(S₂CNMeHex)], which has a melting point of 65 °C was selected as the best single source precursor and thin films of predominantly Pd_2.8S were deposited on glass slides. The crystal structures of [(η³-C₄H₇)Pd(S₂CNMe₂)], [(η³-C₄H₇)Pd(S₂CNPr₂)], [(η³-C₄H₇)Pd(S₂PPh₂)] and [Pd(S₂CNMeBu)₂] are reported. All except [(η³-C₄H₇)Pd(S₂CNPr₂)] show weak intermolecular S?H or Pd?H interactions.     

A convenient synthesis of methylindium(III) dithiolate complexes—precursors for indium sulfides

Methylindium(III) dithiolate complexes of the general formulae [Me₂In(S^∩S)] ( 1 ) and [MeIn(S^∩S)₂] ( 2 ) [S^∩S = (EtO)₂PS₂^?, (PrⁱO)₂PS₂^?, Et₂NCS₂^?, , O(CH₂CH₂)₂NCS₂^?, EtOCS₂^? and PrⁱOCS₂^?] have been isolated conveniently by the reaction of Me₃In·OEt₂ with In(S^∩S)₃ ( 3 ) in an appropriate stoichiometry. Both 1 and 2 have been characterized by indium analysis, IR, NMR (¹H, ¹³C{¹H} and ³¹P{H}) and mass spectral data. NMR data of 3 are also included for comparison. The Me–In and S^∩S resonances are sensitive to the number of methyl groups attached to indium metal. The mass spectral data indicate that these complexes are monomeric in nature. The thermal behavior of a few complexes has been investigated. The xanthate and dithiocarbamate complexes on pyrolysis under dynamic vacuum or flowing nitrogen atmosphere gave either In₂S₃ or a mixture of InS, In₂S₃ and In₆S₇, which were characterized using EDAX and powder XRD. Copyright © 2005 John Wiley & Sons, Ltd.     

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh₃)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] ( 2c ) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh₃)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a , b (alkyl=ⁱPr or ^tBu, P*CHP*) and the complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 3). The crystal structures of achiral [RuCl(equation/tex2gif-sup-3.gifPCP)(PPh₃)] 4c and of chiral (S,S)‐[RuCl(equation/tex2gif-sup-6.gifPCP)(PPh₃)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh₃)] complexes and chiral [RuCl(P*CP*)(PPh₃)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.     

Bimetallic complexes with porphyrins containing a cyclometalated phenylpyridine group

Treatment of Ni(HP¹) (H₃P¹ = meso-5-[4′-(2″-pyridyl)phenyl]-10,15,20-triphenyporphyrin) with K₂[PdCl₄] in EtOH afforded [Pd{Ni(P¹)}]₂(μ-Cl)₂ that reacted with NaS₂CNEt₂ to give Pd(S₂CNEt₂)[Ni(P¹)]. Reaction of Ni(HP¹) with [Ir(H)₂(PPh₃)₂(Me₂CO)₂][BF₄] afforded Ir(H)Cl(PPh₃)₂[Ni(P¹)]. The crystal structures of Pd(S₂CNEt₂)[Ni(P¹)] and Ir(H)(Cl)(PPh₃)₂[Ni(P¹)] have been determined.     

N-phosphonio formamidine derivatives: Synthesis,characterization, X-ray crystal structures,and deprotonation reactions

A simple and efficient method for the preparation of N-phosphonio formamidine derivatives of the general formula [R”₂N?C(H)=N?P(R’)R₂]⁺X^? is described. The data recorded in solution and the single crystal X-ray studies revealed that these compounds are best described by the combination of the two mesomeric N-phosphonio formamidine [R”₂N?C(H)=N?P(R’)R₂]⁺ and iminium phosphazene [R”₂N=C(H)?N=P(R’)R₂]⁺ forms. Formamidine phosphorus ylides ⁱPr₂N?C(H)=N?P(CH₂)R₂ were prepared after addition of ^tBuLi at –78 °C from the corresponding N-phosphonio compounds. [(PhCN)₂Pd(Cl)₂] was reacted with ⁱPr₂N?C(H)=N?P(CH₂)ⁱPr₂ to form the dimeric complex [(ⁱPr₂N?C(H)=N?P(CH₂)ⁱPr₂)Pd(Cl)(μ-Cl)]₂ which was structurally characterized by X-ray analysis. The deprotonation reactions conducted on [ⁱPr₂N?C(H)=N?PPh₃]⁺X^? occurred via an intramolecular rearrangement to give the cyanamide compound ⁱPr₂N?C≡N and PPh₃; transient formation of the amino-phosphazene-carbene ⁱPr₂N?C?N=PPh₃ was not observed.     

Variable Bonding Modes of Pyrimidine‐2‐thione in PdII/PtII Complexes [M(η2‐N,S‐pymS)(η1‐S‐pymS)(PPh3)] and [M(η1‐S‐pymS)2(L‐L)] (L‐L = dppm,dppe)

Reactions of pyrimidine‐2‐thione (HpymS) with Pd^II/Pt^IV salts in the presence of triphenyl phosphine and bis(diphenylphosphino)alkanes, Ph₂P‐(CH₂)_m‐PPh₂ (m = 1, 2) have yielded two types of complexes, viz. a) [M(η²‐N, S‐ pymS)(η¹‐S‐ pymS)(PPh₃)] (M = Pd, 1 ; Pt, 2 ), and (b) [M(η¹‐S‐pymS)₂(L‐L)] {L‐L, M = dppm (m = 1) Pd, 3 ; Pt, 4 ; dppe (m = 2), Pd, 5 ; Pt, 6 }. Complexes have been characterized by elemental analysis (C, H, N), NMR spectroscopy (¹H, ¹³C, ³¹P), and single crystal X‐ray crystallography ( 1 , 2 , 4 , and 5 ). Complexes 1 and 2 have terminal η¹‐S and chelating η²‐N, S‐modes of pymS⁻, while other Pd/Pt complexes have only terminal η¹‐S modes. The solution state ³¹P NMR spectral data reveal dynamic equilibrium for the complexes 3 , 5 and 6 , whereas the complexes 1 , 2 and 4 are static in solution state.     

The influence of substituents (R) at the C carbon on bonding properties of thiosemicarbazones {RC(H)N-NH–C(S)–NH2} in palladium(II) complexes

Reactions of the trans-PdCl₂(PPh₃)₂ precursor with furan-2-carbaldehyde thiosemicarbazone (Hftsc) and thiophene-2-carbaldehyde thiosemicarbazone (Httsc), in 1:1 molar ratios in the presence of Et₃N base, removed one Cl and one PPh₃ group from the Pd^II center, and yielded the complexes [Pd(η²-N³,S-ftsc)(PPh₃)Cl] (1) and [Pd(η²-N³,S-ttsc)(PPh₃)Cl] (2), respectively. However, when a 1:2 molar ratio (M:L) was used, both Cl and PPh₃ ligands were removed, yielding the complexes trans-[Pd(η²-N³,S-ftsc)₂] (3) and trans-[Pd(η²-N³,S-ttsc)₂] (4). Complexes 1–4 have been characterized with the help of analytical data, spectroscopic techniques (IR, ¹H and ³¹P NMR) and single crystal X-ray crystallography. The thiosemicarbazone ligands behave as uninegative N³,S-chelating ligands in complexes 1–4. In contrast, pyrrole-2-carbaldehyde thiosemicarbazone (H₂ptsc) and salicylaldehyde thiosemicarbazone (H₂stsc) invariably formed the complexes [Pd(η³-N⁴,N³,S-ptsc)(PPh₃)] (5) and [Pd(η³–O, N³,S-stsc)(PPh₃)] (6), respectively, and the ligands acted as binegative tridentate donors (N⁴, N³, S, 5; O, N³, S, 6).     

Platinum(II) pyridine-2-thiolate and -selenolate complexes

The reaction of [Pt₂X₂(-Cl)₂(PR₃)₂] with NaSpy or NaSepy gave complexes of the type [PtX(Epy)(PR₃)]_n (X=Cl or Ar; E=S or Se; PR₃=PEt₃, PMe₂Ph, PMePh₂ or PPh₃; n=1 or 2) which were characterized by elemental analysis and by ¹H, ³¹P{¹H}, ¹⁹⁵Pt{¹H} n.m.r. spectroscopy. When X=Cl a dynamic equilibrium between [Pt₂Cl₂(-Spy)₂(PR₃)₂] and [PtCl(k-S,N-Spy)(PR₃)] species exists in CHCl₃ solution. The aryl derivatives, X=Ar, exist exclusively as dimers (n=2) with predominantly SN bridging. The [Pt(Spy)₂ (PPh₃)₂] complex, prepared by reacting [PtCl₂ (PPh₃)₂] with NaSpy, dissociates in CHCl₃ to [Pt(k-S,N-Spy) (Spy)(PPh₃)] and PPh₃ at room temperature.     

Dipyrromethane-Based PGeP Pincer Germyl Rhodium Complexes

A family of germyl rhodium complexes derived from the PGeP germylene 2,2’-bis(di-isopropylphosphanylmethyl)-5,5’-dimethyldipyrromethane-1,1’-diylgermanium(II), Ge(pyrmPⁱPr₂)₂CMe₂ ( 1 ), has been prepared. Germylene 1 reacted readily with [RhCl(PPh₃)₃] and [RhCl(cod)(PPh₃)] (cod=1,5-cyclooctadiene) to give, in both cases, the PGeP-pincer chloridogermyl rhodium(I) derivative [Rh{κ³P,Ge,P-GeCl(pyrmPⁱPr₂)₂CMe₂}(PPh₃)] ( 2 ). Similarly, the reaction of 1 with [RhCl(cod)(MeCN)] afforded [Rh{κ³P,Ge,P-GeCl(pyrmPⁱPr₂)₂CMe₂}(MeCN)] ( 3 ). The methoxidogermyl and methylgermyl rhodium(I) complexes [Rh{κ³P,Ge,P-GeR(pyrmPⁱPr₂)₂CMe₂}(PPh₃)] (R=OMe, 4 ; Me, 5 ) were prepared by treating complex 2 with LiOMe and LiMe, respectively. Complex 5 readily reacted with CO to give the carbonyl rhodium(I) derivative [Rh{κ³P,Ge,P-GeR(pyrmPⁱPr₂)₂CMe₂}(CO)] ( 6 ), with HCl, HSnPh₃ and Ph₂S₂ rendering the pentacoordinate methylgermyl rhodium(III) complexes [RhHX{κ³P,Ge,P-GeMe(pyrmPⁱPr₂)₂CMe₂}] (X=Cl, 7 ; SnPh₃, 8 ) and [Rh(SPh)₂{κ³P,Ge,P-GeMe(pyrmPⁱPr₂)₂CMe₂}] ( 9 ), respectively, and with H₂ to give the hexacoordinate derivative [RhH₂{κ³P,Ge,P-GeMe(pyrmPⁱPr₂)₂CMe₂}(PPh₃)] ( 10 ). Complexes 3 and 5 are catalyst precursors for the hydroboration of styrene, 4-vinyltoluene and 4-vinylfluorobenzene with catecholborane under mild conditions.     

The Influence of Substituents at C2 Carbon Atom of Thiosemicarbazones {R(H)C2=N3‐N2(H)‐C1(=S)‐N1H2} on their Dentacy in PtII/PdII Complexes: Synthesis,Spectroscopy, and Crystal Structures

The coordination chemistry of platinum(II) with a series of thiosemicarbazones {R(H)C²=N³‐N²(H)‐C¹(=S)‐N¹H₂, R = 2‐hydroxyphenyl, H₂stsc; pyrrole, H₂ptsc; phenyl, Hbtsc} is described. Reactions of trans‐PtCl₂(PPh₃)₂ precursor with H₂stsc (or H₂ptsc) in 1 : 1 molar ratio in the presence of Et₃N base yielded complexes, [Pt(η³‐ O, N³, S‐stsc)(PPh₃)] ( 1 ) and [Pt(η³‐ N⁴, N³, S‐ptsc)(PPh₃)] ( 2 ), respectively. Further, trans‐PtCl₂(PPh₃)₂ and Hbtsc in 1 : 2 (M : L) molar ratio yielded a different compound, [Pt(η²‐ N³, S‐btsc)(η¹‐S‐btsc)(PPh₃)] ( 3 ). Complex 1 involved deprotonation of hydrazinic (‐N²H‐) and hydroxyl (‐OH) groups, and stsc^2? is coordinating via O, N³, S donor atoms, while complex 2 involved deprotonation of hydrazinic (‐N²H‐) and ‐N⁴H groups and ptsc^2? is probably coordinating via N⁴, N³, S donor atoms. Reaction of PdCl₂(PPh₃)₂ with Hbtsc‐Me {C₆H₅(CH₃)C²=N³‐N²(H)‐C¹(=S)‐N¹H₂} yielded a cyclometallated complex [Pd(η³‐C, N³, S‐btsc‐Me)(PPh₃)] ( 4 ). These complexes have been characterized with the help of analytical data, spectroscopic techniques {IR, NMR (¹H, ³¹P), U.V} and single crystal X‐ray crystallography ( 1 , 3 and 4 ). The effects of substituents at C² carbon of thiosemicarbazones on their dentacy and cyclometallation are emphasized.     

The oxidative addition of SnCl4 to [W(CO)4(NCMe)(PPh3)]. The X-ray crystal structure of [WH(CO)3(NCMe)(PPh3)2][SnCl5·MeOH]

The oxidative addition reaction of SnCl₄ with [W(CO)₄(NCMe)(PPh₃)] in acetonitrile gives a mixture of seven-coordinate tungsten(II) compounds: [WCl(SnCl₃)(CO)₃(NCMe)(PPh₃)] (1), [WCl₂(CO)₃(NCMe)(PPh₃)] (2), [WCl(SnCl₃)(CO)₂(NCMe)₂(PPh₃)] (3), and [WCl₂(CO)₂(NCMe)₂(PPh₃)] (4) identified by IR and NMR (¹H, ¹³C{¹H}, and ³¹P{¹H}) studies. Treatment of [W(CO)₄(NCMe)(PPh₃)] with 1 equiv. of SnCl₄ in CH₂Cl₂ solution besides compounds 1 and 2 also gives ionic species such as [HPPh₃]⁺ and [SnCl₆]²⁻ and cationic tungsten(II) complexes. The crystal structure of one of these, [WH(CO)₃(NCMe)(PPh₃)₂][SnCl₅·MeOH] (5), has been established by single-crystal X-ray diffraction. The IR, ¹H, ¹³C{¹H} and ³¹P{¹H} spectra of 5 are also described and can be correlated with the crystallographically observed geometry. A notable feature of 5 is the presence of an agostic interaction of the hydride ligand with one of the carbonyl ligands.     

Preparation and reactions of palladium(II) complexes with C2-bonded heteroaromatic ligands trans[PdCl(RN)(PPh3)2] (RN = 2-pyridyl, 2-pirazyl, 2-pyrimidyl group). A new reaction pathway in the insertion of isocyanides into the Pdc bond of trans-[PdXR(L)2] compounds

The complexes trans-[PdCl(R_N)(PPh₃)₂] (I) [R_N = 2-pyridyl (2-Py), 2-pyrazyl (2-pyz), 2-pyrimidyl (2-pym) group] have been prepared in high yield by deprotonation with NEt₃ of the corresponding cationic compounds trans[PdCl(R_NH) (PPh₃)₂]⁺ (R_NH = N-protonated C²-heteroaromatic ligand) in the presence of an excess of PPh₃. In chlorinated solvents, complexes I undergo a slow reversible dimerization into the binuclear derivatives [PdCl(μ-R_N)(PPh₃)]₂ (II) (μ-R_N = C²,N¹-bridging ligand). From the ³¹P NMR spectra in 1,2-dichloroethane the following dissociation constants were obtained: 1.9 mol 1⁻¹ (R_N= 2-py), 5.1 × 10⁻² (2-pym), 6.6 × 10⁻³ (2-pyz). The dimerization becomes fast and quantitative if the PPh₃, involved in the equilibrium is removed by oxidation or by reaction with [PdCl(η³-2-MeC₃H₄)]₂. Only the 2-pyridyl complex Ia reacts (slowly) with CO yielding the migratory insertion product trans-[PdCl{C(2-py)O}(PPh₃)₂], together with the dimer IIa. All the complexes I undergo migratory insertion of t-butylisocyanide with formation of trans-[PdCl{C(R_N) = NCMe₃}(PPh₃)₂]] at rates which depend on the heterocyclic group (R_N = 2-py > 2-pyz ⪢ 2-pym). The reaction of the 2-pyrazyl complex Ib with CNCMe₃ has been studied in detail by conductivity measurements and by IR and ³¹P NMR spectroscopy. The data suggest a complex mechanism in which insertion occurs through rearrangement of a four-coordinate intermediate [PdCl(2-pyz)(CNCMe₃)(PPh₃)], and through interaction of a cationic intermediate trans-[Pd(2-pyz)(CNCMe₃)(PPh₃)₂]⁺ (Vb) with Cl⁻ and with the free isocyanide of the initial equilibria. The occurrence of the latter reactions is confirmed by independent experiments in which the cationic complex Vb (isolated as perchlorate salt) is treated with an equimolar amount of [AsPh₄]Cl or CNCMe₃. The isocyanide-promoted insertion step represents a new mechanistic pathway for isocyanide insertion into the PdC bond of trans-[PdXR(L)₂] complexes.     

Preparation and Structural Studies of [Mo(N3S2){R2(0)PNP(S)R2}2]

Abstract

The compounds [Mo(N₃S₂){Ph₂(O)PNP(S)Ph₂}₂] 1 [Mo(N₃S₂){ⁱPr₂(O)PNP(S)ⁱPr₂}₂] 2 have been synthesised by treating [MoCl₃(N₃S₂)] with KN(PPh₂S)₂ or KN(PⁱPr₂S)₂. X–Ray structures of 1 and 2 have been solved. On complexation, the MoN₃S₂ ring remained planar, but the Mo(OPNPS)₂ rings are puckered.     

Square-Planar Nickel(II) O,O′-Dialkyldithiophosphato Complexes with Triphenylphosphine of the Type [NiX(S2P{OR}2)(PPh3)] (X = Cl,Br, I and NCS)

A series of new [NiX(S₂P{O-c-Hex}₂)(PPh₃)](X = Cl^–, Br^–, I^– and NCS^–)(1)–(4) and [Ni(NCS)(S₂P{OR}₂)(PPh₃)][R =n-Pr (5), i-Pr (6)] complexes has been synthesized and characterized by elemental analyses, f.i.r., i.r., u.v.–vis., ¹H-, ¹³C{¹H}- and ³¹P{¹H}-n.m.r. spectra, magnetochemical and conductivity measurements. A single crystal X-ray analysis of [Ni(NCS)(S₂P{O-n-Pr}₂)(PPh₃)](5) reveals the molecular structure of the complex and confirms a square-planar geometry around the central atom of nickel with the NCS anion coordinated via the nitrogen atom.     

Nickelocene chemistry : III. Reactions of Bromo(η5-cyclopentadienyl)triphenylphosphinenickel with phosphorus,arsenic and sulphur ylids

The phosphorus ylids Ph₃PCHR (R = Me, Et, Prⁿ, Prⁱ, Bu_n, Cl, and OMe), and the ylids Ph₃AsCH₂, Me₂SCH₂, and Me₂S(O)CH₂ react with [Ni(η⁵-C₅H₅)Br(PPh₃)] at room temperature to give the complexes [Ni(Ph₃PCHR)(η⁵-C₅H₅(PPh₃)] Br, [Ni(Ph₃AsCH₂)(η⁵-C₅H₅)(PPh₃)]Br, [Ni(Me₂SCH₂)(η⁵-C₅H₅)(PPh₃)]Br and [Ni{Me₂S(O)CH₂} (η⁵-C₅H₅)(PPh₃)]Br, respectively. These are readily converted into the corresponding hexafluorophosphate salts on reaction with ammonium hexafluorophosphate. Under more forcing conditions the stabilised ylid Ph₃PCHCOPh gives a product believed to be the complex [Ni(Ph₃PCHCOPh)₂(η⁵-C₅H₅)]Br, isolated and characterised as its PF₆^? salt.     

Insights into the Two-Electron Reductive Process of [FeFe]H2ase Biomimetics: Cyclic Voltammetry and DFT Investigation on Chelate Control of Redox Properties of [Fe2(CO)4(κ2-Chelate)(μ-Dithiolate)]

The electrochemical reduction of complexes [Fe₂(CO)₄(κ²-phen)(μ-xdt)] (phen=1,10-phenanthroline; xdt=pdt ( 1 ), adt^iPr ( 2 )) in MeCN-[Bu₄N][PF₆] 0.2 m is described as a two-reduction process. DFT calculations show that 1 and its monoreduced form 1⁻ display metal- and phenanthroline-centered frontier orbitals (LUMO and SOMO) indicating the non-innocence of the phenanthroline ligand. Two energetically close geometries were found for the doubly reduced species suggesting an intriguing influence of the phenanthroline ligand leading to the cleavage of a Fe−S bond as proposed generally for this type of complex or retaining the electron density and avoiding Fe−S cleavage. Extension of calculations to other complexes with edt, adt^iPr bridge and even virtual species [Fe₂(CO)₄(κ²-phen)(μ-adt^R)] (R=CH(CF₃)₂, H) or [Fe₂(CO)₄(κ²-phen)(μ-pdt^R)] (R=CH(CF₃)₂, iPr) showed that the relative stability between both two-electron-reduced isomers depends on the nature of the bridge and the possibility to establish a remote anagostic interaction between the iron center {Fe(CO)₃} and the group carried by the bridged-head atom of the dithiolate group.     

Synthesis,Reactivity and Crystal Structures of the Palladium(II) Complexes with the Pyrimidine Containing Ligand: Crystal Structures of [Pd(PPh3)(η1‐C4H3N2)(η2‐S2CNC4H8)] and [Pd(PPh3)(η1‐C4H3N2)(η2‐Tp)]

Treatment of Pd(PPh₃)₄ with 5‐bromo‐pyrimidine [C₄H₃N₂Br] in dichloromethane at ambient temperature cause the oxidative addition reaction to produce the palladium complex [Pd(PPh₃)₂(η¹‐C₄H₃N₂)(Br)], 1 , by substituting two triphenylphosphine ligands. In acetonitrile solution of 1 in refluxing temperature for 1 day, it do not undergo displacement of the triphenylphosphine ligand to form the dipalladium complex [Pd(PPh₃)Br]₂{μ,η²‐(η¹‐C₄H₃N₂)}₂, or bromide ligand to form chelating pyrimidine complex [Pd(PPh₃)₂(η²‐C₄H₃N₂)]Br. Complex 1 reacted with bidentate ligand, NH₄S₂CNC₄H₈, and tridentate ligand, KTp {Tp = tris(pyrazoyl‐1‐yl)borate}, to obtain the η²‐dithiocarbamate η¹‐pyrimidine complex [Pd(PPh₃)(η¹‐C₄H₃N₂)(η²‐S₂CNC₄H₈)], 4 and η²‐Tp η¹‐pyrimidine complex [Pd(PPh₃)(η¹‐C₄H₃N₂)(η²‐Tp)], 5 , respectively. Complexes 4 and 5 are characterized by X‐ray diffraction analyses.