A highly active two six-membered phosphinite palladium PCP pincer complex [PdCl{C6H3(CH2OPPr)2-2,6}]

The diphosphinite 1,3-bis[(di-isopropylphosphinite)methyl]benzene (2) has been synthesized and its complexation in palladium chemistry investigated. Complex 3 represents the first example of a two six-member PCP pincer bis(phosphinite) species. A catalytic study of 3 in the Heck reaction, revealed this specie to have an outstanding activity in the olefination of iodo-, bromo- and chloro-benzenes. When compared with other PCP pincer complexes, the results show that both by increasing the ring size from five to six-membered and using phosphinite instead of phosphine groups lead to a more active catalyst.     

Synthesis, structures and spectroelectrochemistry of methyl-substituted bis(η-indenyl)iron(II) complexes

Several new methyl-substituted indenyl ferrocenes were prepared by metathesis reactions of the indenide (generated from the appropriate indene with BuLi) with ferrous chloride. The indenides used to prepare new ferrocenes were: 2-methyl-, 1,2-dimethyl-, 4,7-dimethyl-, 1,4,7-trimethyl-, and 1,3,4,7-tetramethyl-indenide. These indenyl ferrocenes, along with those prepared from indenide, 1-methylindenide, and 1,3-dimethylindenide, were then characterized by ¹H and ¹³C NMR, UV/visible spectroscopy, cyclic voltammetry and mass spectrometry. The cyclic voltammetry showed an additive relationship between oxidation potential and the number of methyl groups which is also position-dependent, whereas the UV/visible spectra showed two absorptions essentially unaffected by methyl substitution. Additionally, bis(2-methylindenyl)iron(II) and bis(4,7-dimethylindenyl)iron(II) were characterized by X-ray crystallography.     

Synthesis, characterization and electrochemical studies of the heterometallic diclusters [{Fe2(μ-CO)(CO)6(μ-PPh2)Au}2(diphosphine)] (diphosphine=dppm, dppip, dppe, dppp)

Treatment of [(ClAu)₂(diphosphine)] {diphosphine=bis(diphenylphosphino)methane (dppm), bis(diphenylphosphino)isopropane (dppip), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp)} with two equivalents of the anion [Fe₂(μ-CO)(CO)₆(μ-PPh₂)]⁻ in the presence of TlBF₄ gives the new heterometallic diclusters [{Fe₂(μ-CO)(CO)₆(μ-PPh₂)Au}₂(diphosphine)] that have been isolated and characterized. Their ³¹P-NMR spectra show different patterns as a function of the diphosphine ligand. The electrochemical behavior of these compounds has been investigated and compared with that of the mono- [Fe₂(μ-CO)(CO)₆(μ-PPh₂)(μ-AuPPh₃)] and tricluster [{Fe₂(μ-CO)(CO)₆(μ-PPh₂)Au}₃(triphos)] derivatives.     

Reduction reactions of the metallocene complex (η-C5H4CMe2C9H7)2ZrCl2

The preparation and characterization of the substituted bis(cyclopentadienyl) zirconium dichloride complexes (η⁵-C₅H₄CMe₂C₉H₇)₂ZrCl₂ (1a, b) is reported. The isomer mixture of 1a, b was treated with different reducing agents such as sodium and n-butyllithium under various reaction conditions. In these reactions CC and CH activation and cleavage reactions were observed. In combination with methylaluminoxane (MAO) 1a, b and 3 showed low activities as homogeneous ethylene polymerization catalysts and no activities towards propylene. Compounds 2 and 3 were characterized by NMR spectroscopy and X-ray crystallography.     

New homo- and heteroleptic derivatives of trivalent ytterbium containing radical anion 1,4-diazadiene ligands. Synthesis, properties, and crystal structures of the complexes (C9H7)2Yb[2-MeC6H4NC(Me)C(Me)NC6H4Me-2] and [PhNC(Ph)C(Ph)NPh]3Yb

The interaction of the ytterbium bis(indenyl) complex (C₉H₇)₂Yb^II(THF)₂ (1) with the 1,4-diazabutadiene 2-MeC₆H₄N=C(Me)-C(Me)=NC₆H₄Me-2 (^MeDAD) is accompanied by the oxidation of the metal atom to the trivalent state and results in a paramagnetic compound of the metallocene type (C₉H₇)₂Yb^III(^MeDAD^−·) (3) containing the radical anion of 1,4-diazabutadiene. The structure of the complex 3 was determined by X-ray diffraction analysis. The reactions of the bis(indenyl) (1) and bis(fluorenyl) (C₁₃H₉)₂Yb^II(THF)₂ (2) derivatives of divalent ytterbium with the 1,4-diazabutadiene PhN=C(Ph)-C(Ph)=NPh (^PhDAD) (with the molar ratio of the reactants 1:2) proceed with a complete cleavage of the bonds Yb-C and the oxidation of the ytterbium atom to the trivalent state and result in a homoligand complex (^PhDAD^−·)₃Yb (6) containing three radical anion 1,4-diazadiene ligands. Complex 6 was also obtained by an exchange reaction of YbCl₃ with ^PhDAD^−·K⁺ (1: 3) in THF. Complex 6 was characterized by X-ray diffraction analysis.     

Synthesis,spectroscopic and structural investigation of Zn(NCS)2(nicotinamide)2 and [Hg(SCN)2(nicotinamide)]n

Zinc(II) and mercury(II) thiocyanate complexes with nicotinamide, bis(nicotinamide-N)-bis(thiocyanato-N)zinc(II) (1) and catena-[nicotinamide-N-(μ-thiocyanato-S,N)(thiocyanato-S)mercury(II)] (2), have been prepared and characterized by spectroscopic, thermal and X-ray crystallographic methods. The vibrational bands of diagnostic value are compared to the values of the free ligand and the data are in good correlation with the X-ray results. Centrosymmetrical hydrogen bonded dimers are found, R₂²(10) in 1 and R₂²(8) in 2.     

Bis(diphenylphosphino)amid-komplexe des platins,palladiums und nickels. Kristallstruktur des N-methylierungsprodukts {CH3N[(C6H5)2P]2}2Pd2+ 2SO3F−

Reaction of lithiated bis(diphenylphosphino)amine, [(C₆H₅)₂P]₂N^? Li⁺, with K₂PtCl₄ or PdCl₂ (in the presence of trimethylphosphine) yields the homoleptic bis[bis(diphenylphosphino)amide] complexes I and II, respectively. With NiCl₂/(CH₃)₃P the chloro-bridged dinuclear complex III is obtained. A symmetrical bonding of the Ph₂P-·N-·PPh₂ anion to the metal through the phosphorus atoms is indicated for these diamagnetic, deep-yellow (I, II) or red (III) complexes by ³¹P NMR spectroscopy (J(PtP) 1812 Hz for I). I and II are dissolved in CF₃COOH with protonation at the nitrogen atoms to give bis(diphenylphosphino)amine complexes IV and V, respectively (J(PtP) 2080 Hz for IV). IV and V are 1:2 electrolytes in CH₃NO₂. Methylation of I-III with CH₃OSO₂F leads to the bis(diphenylphos-phino)methylamine complexes VI-VIII, of which the palladium compound VII has been structurally characterized by single crystal X-ray diffraction. VII contains a planar CNP₂PdP₂NC skeleton and is thus based on planar ligand arrays both at Pd and at the two N atoms.     

Iron carbonyl complexes of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane. Crystal and molecular structure of (C10H10O)Fe(CO)3 and (C9H10CO)Fe2(CO)6

The reaction of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane (I) with iron carbonyls in various solvents yields the (η⁴-1,3-diene)Fe(CO)₃ isomers (II: exo; III: endo) and the bimetallic isomers bis[(η⁴-1,3-diene)Fe(CO)₃] (IV: bis(exo); V: endo,exo). In weakly coordinating solvents, a parallel rearrangement of I occurs through CO bond cleavage of the allylic ether by Fe₂(CO)₉ yielding an unsaturated ketone (VI) bonded to two Fe(CO)₃ groups through a trimethylenemethane and a 1,3-diene system, respectively. The geometries of III and VI have been ascertained by X-ray crystal structure determinations.     

Preparation and reactivity of the new cyclopentadienyl-bridged complex (Me2SiCH2CH2SiMe2)(C5H4Fe(CO)2)2

A new metal-metal bonded binuclear iron system [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂]₂ (2) has been prepared by treating two equivalents of NaCp with one equivalent of ClSi(Me)₂CH₂CH₂SiClMe₂ obtaining the intermediate (C₅H₅)Si(Me)₂CH₂CH₂Si(Me)₂(C₅H₅) which then is directly allowed to react with Fe(CO)₅ given 2 in 30% yield. From this cyclopentadienyldisilyl linked system three new binuclear irom complexes are formed. Treatment of 2 with Na/Hg in THF produced the dianion [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂^?]₂ which is quenched with CH₃I giving [Me₂SiCH₂CH₂SiMe₂][η⁵-C₄H₄Fe(CO)₂CH₃]₂ (4) in 76% yield. Complex 2 is oxidized with 1.2 equivalent of I₂ to give [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)₂I]₂ (5) in 85% yield. Photolysis of 5 (1 equiv.) and PPh₃ (3 equiv.) results in the formation of the bis-substituted compound [Me₂SiCH₂CH₂SiMe₂][η⁵-C₅H₄Fe(CO)(PPh₃)I]₂ (6). These four new binuclear iron complexes are characterized by ¹H, ¹³C, and ³¹P NMR and IR spectroscopy.     

Synthesis and characterization of mercury(II) complexes with 2-styryl-1,3-benzothiazole (sb). Presence of two differently coordinated Hg(II) ions in the dinuclear complex Hg2Cl4(sb)3. Structural characterization of 2-styryl-1,3-benzothiazole and some of its derivatives

The molecular and crystal structures of the following compounds 2-styryl-1,3-benzothiazole, sb, (1), Hg₂Cl₄(sb)₃ (2), 1,3-bis(1,3-benzothiazol-2-yl)-2,4-diphenylcyclobutane (3) 1,3-bis(1,3-benzothiazol-2-yl)-2,4-bis(4-chlorophenyl)cyclobutane (4) and HgBr₂(sb)₂ (5) were determined by single-crystal X-ray diffractometry. The crystal structure of 1 consists of discrete sb molecules which are essentially planar. The dimeric molecules of 3 and 4 are characterized by a cyclobutane ring. In both isolated complexes 2 and 5, sb acts as a neutral monodentate ligand coordinated to the mercury atom through the thiazolyl nitrogen atom. The dinuclear complex 2 is characterized by the unique example of two differently coordinated Hg(II) ions bridged via a non-symmetrical linear Cl⁻ bridge. The first one is coordinated by one terminal and one bridging Cl⁻ ion and two thiazolyl nitrogen atoms in the form of distorted tetrahedron. The second one is bonded to two terminal Cl⁻ ions and the bridging Cl⁻ ion and one thiazolyl nitrogen atom in a 2+2 manner. In complex 5 the Hg(II) ion, which is situated on a crystallographic twofold axis, is tetrahedrally coordinated by two Br⁻ ions and two thiazolyl nitrogen atoms. Both complexes are characterized by stronger mercury-to-halide covalent bonds than mercury-to-nitrogen bonds, which are regarded as contacts shorter than the van der Waals radii sum of the corresponding atoms. The geometry of the sb ligand in both complexes 2 and 5 has not been changed remarkably from that one in the uncoordinated state due to not so strong bonds formation with the Hg(II) ion.     

The crystal and molecular structure of 1-bromobenzocymantrene, (η5-C9H6Br)Mn(CO)3

The crystal and molecular structure of tricarbonyl [1–4: 9-η-(1-bromo)indenyl]manganese (III) prepared by reaction of bromo(pentacarbonyl)manganese (II) with diazoindene (I) (“diazo method”) has been determined by X-ray diffraction methods. III belongs to the monoclinic space group P2₁/c with unit cell constants a 12.953(9), b 7.627(5), c 13.098(9) Å, and β 110.53(5)°. Full-matrix least-squares refinement converged with a conventional R factor of 0.052 based on 1505 observed reflections. The molecule contains an essentially planar indenyl-π-ligand which is coordinated to the manganese atom through its cyclopentadienyl-like moiety. The bromine ligand is attached to the C(1) position of the indenyl system and has only a very slight influence on the characteristics of the indenyl skeleton. The change from cyclopentadienyl (in cymantrene) to indenyl (in III) produces essentially no disturbance in the normal manganese—carbonyl linkage.     

Thermal transformation of 1D-Pb(en)2Cl2 to 3D-PbCl2via 2D-Pb(en)Cl2 and their substantial modification of the coordination environment on Pb(II)

The solvothermal synthesis and crystal structures of two new lead(II) compounds, bis(ethylenediamine)lead(II) chloride, Pb(en)₂Cl₂1 and mono(ethylenediamine)lead(II) chloride, Pb(en)Cl₂2, are reported. A detailed comparison of the two structures is given. In 1, the Pb(II) center is coordinated by two chlorine atoms and four nitrogen atoms from three en ligands, which act as either chelating or bridging ligands, allowing links to other Pb(II) centers. This creates an infinite linear chain of Pb(en)₂Cl₂. In 2, the Pb(II) center is chelated by one en ligand and is coordinated by six chlorine atoms, including two unusually weak Pb–Cl bonds (>3.5 Å) connected through μ₂- and μ₄-Cl to build a neutral layer of Pb(en)Cl₂ units. Complex 1 contains a hemidirected Pb(II), while complex 2 has a (pseudo-)hemidirected Pb(II). TGA and high-temperature controlled powder-XRD studies show that compound 1 decomposes to compound 2 near 150 °C, and finally to PbCl₂ above 320 °C.     

Synthesis and reaction chemistry of 4-nitrile-substituted NCN-pincer palladium(II) and platinum(II) complexes (NCN = [NC-4-C6H2(CH2NMe2)2-2,6])

Nitrile-functionalized NCN-pincer complexes of type [MBr(NC-4-C₆H₂(CH₂NMe₂)₂-2,6)] (6a, M = Pd; 6b, M = Pt) (NCN = [C₆H₂(CH₂NMe₂)₂-2,6]⁻) are accessible by the reaction of Br-1-NC-4-C₆H₂(CH₂NMe₂)₂-2,6 (2b) with [Pd₂(dba)₃ · CHCl₃] (5a) (dba = dibenzylidene acetone) and [Pt(tol-4)₂(SEt₂)]₂ (5b) (tol = tolyl), respectively. Complex 6b could successfully be converted to the linear coordination polymer {[Pt(NC-4-C₆H₂(CH₂NMe₂)₂-2,6)](ClO₄)}_n (8) upon its reaction with the organometallic heterobimetallic π-tweezer compound {[Ti](μ-σ,π-CCSiMe₃)₂}AgOClO₃ (7) ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti).The structures of 6a (M = Pd) and 6b (M = Pt) in the solid state are reported. In both complexes the d⁸-configurated transition metal ions palladium(II) and platinum(II) possess a somewhat distorted square-planar coordination sphere. Coordination number 4 at the group-10 metal atoms M is reached by the coordination of two ortho-substituents Me₂NCH₂, the NCN ipso-carbon atom and the bromide ligand. The NC group is para-positioned with respect to M.     

Synthesis and characterization of (C5H9C9H6)2Yb(THF)2(II) (1) and [(C5H9C5H4)2Yb(THF)]2O2 (2), and ring-opening polymerization of lactones with 1

Reaction of YbI₂ with two equivalents of cyclopentylindenyl lithium (C₅H₉C₉H₆Li) affords ytterbium(II) substituted indenyl complex (C₅H₉C₉H₆)₂Yb(THF)₂ (1) which shows high activity to ring-opening polymerization (ROP) of lactones. The reaction between YbI₂ and cyclopentylcyclopentadienyl sodium (C₅H₉C₅H₄Na) gives complex [(C₅H₉C₅H₄)₂Yb(THF)]₂O₂ (2) in the presence of a trace amount of O₂, the molecular structure of which comprises two (C₅H₉C₅H₄)₂Yb(THF) bridged by an asymmetric O₂ unit. The O₂ unit and ytterbium atoms define a plane that contains a C_i symmetry center.     

Synthesis and characterisation of six Fe(II or III), Co(II) or Zr(IV) complexes containing the ligand [CH(SiMe2R)P(Ph)2NSiMe3] (R = Me, NEt2) and of [Co{N(SiMe3)C(Ph)C(H)P(Ph)2NSiMe3}2]

The C,N-(trimethylsilyliminodiphenylphosphoranyl)silylmethylmetal complexes [Fe(L)₂] (3), [Co(L)₂] (4), [ZrCl₃(L)]·0.83CH₂Cl₂ (5), [Fe(L)₃] (6), [Fe(L′)₂] (7) and [Co(L′)₂] (8) have been prepared from the lithium compound Li[CH(SiMe₂R)P(Ph)₂NSiMe₃] [1a, (R = Me) {≡ Li(L)}; 1b, (R = NEt₂) {≡ Li(L′)}] and the appropriate metal chloride (or for 7, FeCl₃). From Li[N(SiMe₃)C(Ph)C(H)P(Ph)₂NSiMe₃] [≡ Li(L″)] (2), prepared in situ from Li(L) (1a) and PhCN, and CoCl₂ there was obtained bis(3-trimethylsilylimino- diphenylphosphoranyl-2-phenyl-N-trimethylsilyl-1-azaallyl-N,N′)cobalt(II) (9). These crystalline complexes 3-9 were characterised by their mass spectra, microanalyses, high spin magnetic moments (not 5) and for 5 multinuclear NMR solution spectra. The X-ray structure of 3 showed it to be a pseudotetrahedral bis(chelate), the iron atom at the spiro junction.     

Vanadium(II) alkyls. Synthesis and X-ray crystal structures of trans-VMe2(dmpe)2 and cis-V(CH2SiMe3) 2(dmpe)2

Treatment of the vanadium(II) tetrahydroborate complex trans-V(η¹-BH₄)₂(dmpe)₂ with (trimethylsilyl) methyllithium gives the new vanadium(II) alkyl cis-V(CH₂SiMe₃)₂(dmpe)₂, where dmpe is the chelating diphosphine 1,2-bis(dimethylphosphino)ethane. Interestingly, this complex could not be prepared from the chloride starting material VCl₂(dmpe)₂. The CH₂SiMe₃ complex has a magnetic moment of 3.8 μ_B, and has been characterized by ¹H NMR and EPR spectroscopy. The cis geometry of the CH₂SiMe₃ complex is somewhat unexpected, but in fact the structure can be rationalized on steric grounds. The X-ray crystal structure of cis-V(CH₂SiMe₃)₂(dmpe)₂ is described along with that of the related vanadium(II) alkyl complex trans-VMe₂(dmpe)₂. Comparisons of the bond distances and angles for VMe₂(dmpe) ₂, V---C = 2.310(5) Å, V---P = 2.455(5) Å, and P---V---P = 83.5(2)° with those of V(CH₂SiMe₃)₂(dmpe)₂, V---C = 2.253(3) Å, V---P = 2.551(1) Å, and P ---V---P = 79.37(3)° show differences due to the differing trans influences of alkyl and phosphine ligands, and due to steric crowding in latter molecule. The V---P bond distances also suggest that metal-phosphorus π-back bonding is important in these early transition metal systems. Crystal data for VMe₂(dmpe)₂ at 25°C: space group P2₁/n, with a = 9.041(1) Å, b = 12.815(2) Å, c = 9.905(2) Å, β = 93.20(1)°, V = 1145.8(5) ų, Z = 2, R_F = 0.106, and R_wF =0.127 for 74 variables and 728 data for which I 2.58 σ(I); crystal data for V(CH₂SiMe₃)₂(dmpe)₂ at −75°C: space group C2/c, with a = 9.652(4) Å, b = 17.958(5) Å, c = 18.524(4) Å, β = 102.07(3)°, V= 3140(3) ų, Z = 4, R_F = 0.033, and R_wF = 0.032 for 231 variables and 1946 data for which I 2.58 σ(I).     

Solubility of trans-Co2(CO)6 [3,5-bis(CF3)C6H3P(i-C3H7)2] in dense carbon dioxide

The title compound (1) was prepared by the reaction of 3,5-bis(CF₃)C₆H₃P(i-C₃H₇)₂ (L1) and Co₂(CO)₈. Its solubility in supercritical carbon dioxide was measured at varying temperatures and pressures using a modified analytical extraction device. Solubility data were determined in the temperature and pressure ranges between 40 and 70 °C and between 100 and 300 bar, respectively. The solubility of 1 is lower compared to (p-CF₃C₆H₄)₃P, but much higher than for transition metal complexes bearing phosphines without fluorinated substituents.     

The evaluation of singlet-triplet separations for [W2(μ-H)(μ-Cl)Cl4(μ-dppm)2] and [W2(μ-H)2 (μ-O2CC6H5)2(P(C6H5)3)2] based on P NMR and crystallographic data

The singlet-triplet separations for the edge-sharing bioctahedral (ESBO) complex W₂(μ-H)(μ-Cl)(Cl₄(μ-dppm)₂ · (THF)₃ (II) has been studied by ³¹P NMR spectroscopy. The structural characterization of [W₂(μ-H)₂(μ-O₂CC₆H₅)₂Cl₂(P(C₆H₅)₃)₂] (I) by single-crystal X-ray crystallography has allowed the comparison of the energy of the HOMOLUMO separation determined using the Fenske-Hall method for a series of ESBO complexes with two hydride bridging atoms, two chloride bridging atoms and the mixed case with a chloride and hydride bridging atom. The complex representing the mixed case, [W₂(μ-H)(μ-Cl)Cl₄(μ-dppm)₂ · (THF)₃] (II), has been synthesized and the value of −2J determined from variable-temperature ³¹P NMR spectroscopy.     

Preparation of chiral diimino- and diaminodiphosphine ligands and their Cu and Ag complexes. X-ray crystal structures of [Cu(1S,2S-cyclohexyl-P2N2)][PF6] and [Ag(1R,2R-cyclohexyl-P2N2H4)][BF4]

The interaction of optically pure 1R,2R-diammoniumyclohexane mono-(+)-tartrate and 1S,2S-diammoniumcyclohexane mono-(−)-tartrate with 2 equiv. of o-(diphenylphosphino)benzaldehyde in the presence of 2 equiv. of potassium carbonate in a refluxing ethanol/water mixture gave the optically pure condensation products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diiminocyclohexane[1R,2R-cyclohexyl-P₂N₂, (R,R)-I] and N,N′-bis[o-(diphenylphosphino)benzylidene]-1S,2S-diiminocyclohexane [1S,2S-cyclohexyl-P₂N₂, (S,S)-I], respectively, in good yield. Reduction of optically pure (R,R)-I and (S,S)-I with NaBH₄ in ethanol gave the optically pure reduced products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diaminocyclohexane[1R,2R-cyclohexyl-P₂N₂H₄, (R,R)-II] and N,N′-bis[o-diphenylphosphine)benzylidene]-1S,2S-diaminocyclohexane[1S,2S-cyclohexyl-P₂N₂H₄, (S,S)-II], respectively, in good yield. The coordination behaviour of I and II toward salts of Cu^I and Ag^I have been examined. The interaction of [Cu(C)₃CN)₄][X] (X = ClO₄⁻, PF₆⁻) with 1 equiv. of optically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II] gave the corresponding optically pure [CuL₄][X] complexes, III–VI IIIa, L₄ = (R,R)-I, X = PF₆⁻ IIIb, L₄ = (R,R)-I, X = ClO₄⁻ IV, X = PF₆⁻; Va, L₄ = (R,R)-II, X = PF₆⁻, Vb L₄ = (R,R)-II, X= ClO₄⁻, VI L₄ = (S,S)-II, X = PF₆⁻, in good yield. For the Cu^I complexes, the L₄ ligand acted as a tetradentate ligand. However, a variable-temperature ³¹P[¹H] NMR study of IIIb shows that at ambient temperature one of the imino groups of the tetradentate ligand undergoes rapid dissociation to form a tridentate ligand. The interaction of AgBF₄ with 1 equiv. of otpically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II gave the corresponding optically pure [AgL₄][BF₄] complexes, VII–X VII L₄ = (R,R)-I; VIII, L₄ = (S,S)-I; IX,L₄ = (R,R)-II; X, L₄ = (S,S)-II], in good yield. For the Ag^I complexes, the L₄ ligand acted as a tetradentate ligand with the two amino groups coordinated unsymmetrically to the silver. A variable temperature ³¹P [¹H] NMR study of VII suggests that at high temperature the complex exists as a tri-coordinated complex. The structurers of IV and IX were established by X-ray diffraction studies.