Binding N2, N2H2, N2H4, and NH3 to transition-metal sulfur sites: modeling potential intermediates of biological N2 fixation

In the quest for low-molecular-weight metal sulfur complexes that bind nitrogenase-relevant small molecules and can serve as model complexes for nitrogenase, compounds with the [Ru(PiPr(3))('N(2)Me(2)S(2)')] fragment were found ('N(2)Me(2)S(2)'(2-)=1,2-ethanediamine-N,N'-dimethyl-N,N'-bis(2-benzenethiolate)(2-)). This fragment enabled the synthesis of a first series of chiral metal sulfur complexes, [Ru(L)(PiPr(3))('N(2)Me(2)S(2)')] with L=N(2), N(2)H(2), N(2)H(4), and NH(3), that meet the biological constraint of forming under mild conditions. The reaction of [Ru(NCCH(3))(PiPr(3))('N(2)Me(2)S(2)')] (1) with NH(3) gave the ammonia complex [Ru(NH(3))(PiPr(3))('N(2)Me(2)S(2)')] (4), which readily exchanged NH(3) for N(2) to yield the mononuclear dinitrogen complex [Ru(N(2))(PiPr(3))('N(2)Me(2)S(2)')] (2) in almost quantitative yield. Complex 2, obtained by this new efficient synthesis, was the starting material for the synthesis of dinuclear (R,R)- and (S,S)-[micro-N(2)[Ru(PiPr(3))('N(2)Me(2)S(2)')](2)] ((R,R)-/(S,S)-3). (Both 2 and 3 have been reported previously.) The as-yet inexplicable behavior of complex 3 to form also the R,S isomer in solution has been revealed by DFT calculations and (2)D NMR spectroscopy studies. The reaction of 1 or 2 with anhydrous hydrazine yielded the hydrazine complex [Ru(N(2)H(4))(PiPr(3))('N(2)Me(2)S(2)')] (6), which is a highly reactive intermediate. Disproportionation of 6 resulted in the formation of mononuclear diazene complexes, the ammonia complex 4, and finally the dinuclear diazene complex [micro-N(2)H(2)[Ru(PiPr(3))('N(2)Me(2)S(2)')](2)] (5). Dinuclear complex 5 could also be obtained directly in an independent synthesis from 1 and N(2)H(2), which was generated in situ by acidolysis of K(2)N(2)(CO(2))(2). Treatment of 6 with CH(2)Cl(2), however, formed a chloromethylated diazene species [[Ru(PiPr(3))('N(2)Me(2)S(2)')]-micro-N(2)H(2)[Ru(Cl)('N(2)Me(2)S(2)CH(2)Cl')]] (9) ('N(2)Me(2)S(2)CH(2)Cl'(2-) =1,2-ethanediamine-N,N'-dimethyl-N-(2-benzenethiolate)(1-)-N'-(2-benzenechloromethylthioether)(1-)]. The molecular structures of 4, 5, and 9 were determined by X-ray crystal structure analysis, and the labile N(2)H(4) complex 6 was characterized by NMR spectroscopy.     

N,N-coordinated pi radical anions of S-methyl-1-phenyl-isothiosemicarbazide in two five-coordinate ferric complexes [Fe III(L Me*)(2)X] (X = CH3S-, Cl-)

The reaction between [Fe(III)(dmf)(6)](ClO(4))(3) and the ligand S-methyl-1-phenyl-isothiosemicarbazide, H(2)[L(Me)], and triethylamine (1:3:6) in methanol under an argon blanketing atmosphere at elevated temperatures (reflux) yields a purple solution from which upon cooling to 20 degrees C dark green crystals of [Fe(III)(L(Me)(*))(2)(SCH(3))] (1) were obtained in 15% yield. From a similar reaction mixture using FeCl(3) as starting material in the solvent acetone under anaerobic conditions at -80 degrees C, dark green crystals of [Fe(III)(L(Me)(*))(2)Cl] (2) were obtained in 21% yield. The structures of complexes 1 and 2 have been determined by single-crystal X-ray crystallography at 100 K. Both complexes are five-coordinate square base pyramidal ferric species containing two N,N-coordinated, monoanionic pi radicals, (L(Me)(*))(1)(-), of the parent S-methyl-1-phenyl-isothiosemicarbazide(2-) dianion in the basal positions whereas the axial position is occupied by methylthiolate in 1 and chloride in 2, respectively. The electronic structure of both species has been elucidated by their electronic spectra, magnetic properties, and X-band EPR and M?ssbauer spectra. Both possess an S(t) = (1)/(2) ground state which is attained via an antiferromagnetic coupling between the spins of an intermediate spin ferric ion (S(Fe) = (3)/(2)) and two ligand pi radical anions (S(rad) = (1)/(2)).     

Synthesis, properties and structures of eight-coordinate zirconium(IV) and hafnium(IV) halide complexes with phosphorus and arsenic ligands

Eight-coordinate [MX(4)(L-L)(2)] (M = Zr or Hf; X = Cl or Br; L-L = o-C(6)H(4)(PMe(2))(2) or o-C(6)H(4)(AsMe(2))(2)) were made by displacement of Me(2)S from [MX(4)(Me(2)S)(2)] by three equivalents of L-L in CH(2)Cl(2) solution, or from MX(4) and L-L in anhydrous thf solution. The [MI(4)(L-L)(2)] were made directly from reaction of MI(4) with the ligand in CH(2)Cl(2) solution. The very moisture-sensitive complexes were characterised by IR, UV/Vis, and (1)H and (31)P NMR spectroscopy and microanalysis. Crystal structures of [ZrCl(4)[o-C(6)H(4)(AsMe(2))(2)](2)], [ZrBr(4)[-C(6)H(4)(PMe(2))(2)](2)], [ZrI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] and [HfI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] all show distorted dodecahedral structures. Surprisingly, unlike the corresponding Ti(iv) systems, only the eight-coordinate complex was found in each system. In contrast, the ligand o-C(6)H(4)(PPh(2))(2) forms only six-coordinate complexes [MX(4)[-C(6)H(4)(PPh(2))(2)]] which were fully characterised spectroscopically and analytically. Surprisingly the tripodal triarsine, MeC(CH(2)AsMe(2))(3), also produces eight-coordinate [MX(4)[MeC(CH(2)AsMe(2))(3)](2)] in which the triarsines bind as bidentates in a distorted dodecahedral structure. There is no evidence for seven-coordination as found in some thioether systems.     

Recognition of topological isomerism: synthesis,structure, and magnetic properties of two pentanuclear high-spin molecules of the type [NiI(N-N)2]3[FeIII(CN)6]2

The syntheses, structures, and magnetic properties of two pentanuclear cyanide-bridged compounds are reported. The trigonal bipyramidal molecule [[Ni(tmphen)(2)](3)[Fe(CN)(6)](2)].14H(2)O, (1).14H(2)O (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) crystallizes in the space group P2(1)/c (No. 14) with unit cell parameters a = 19.531(4) A, b = 24.895(5) A, c = 24.522(5) A, beta = 98.68(3) degrees, V = 11787(4) A(3), and Z = 4. The pi-pi interactions between the tmphen ligands provide the closest intermolecular contacts of 3.37 A leading to large intermolecular M...M distances (> 8.68 A). The dc magnetic susceptibility of 1 indicates a ferromagnetically coupled S = 4 ground state best fit to the parameters g = 2.23, J = +4.3 cm(-1), and D(Ni) = +8.8 cm(-1) for the Hamiltonian H = -2J [(S(Fe(1)) + S(Fe(2))).(S(Ni(1)) + S(Ni(2)) + S(Ni(3)))] + D[S(Ni(1))(z)(2) + S(Ni(2))(z)(2) + S(Ni(3))(z)(2)]. The extended square molecule [Ni(bpy)(2)(H(2)O)][[Ni(bpy)(2)](2)[Fe(CN)(6)](2)].12H(2)O, (2).12H(2)O (bpy = 2,2'-bipyridine) crystallizes in the space group P1 (No. 2) with unit cell parameters a = 13.264(3) A, b = 17.607(4) A, c = 18.057(4) A, alpha = 94.58(3) degrees, beta = 103.29(3) degrees, gamma = 95.18(3) degrees, V = 4065(2) A(3), and Z = 2. The pi-pi interactions of 3.29 A between the bpy ligands are the closest intermolecular contacts, and the intermolecular M...M separations are greater than 7.76 A. The dc magnetic susceptibility data for 2 are also in accord with an S = 4 ground state arising from intramolecular ferromagnetic coupling. The data were best fit to the parameters g = 2.25, J = J' = +3.3 cm(-1), and D(Ni) = +5.8 cm(-1) for the Hamiltonian H = -2J[(S(Fe(1)) + S(Fe(2))).(S(Ni(1)) + S(Ni(2)))] - 2J'[(S(Fe(2)).S(Ni(3)))] + D[S(Ni(1))(z)(2) + S(Ni(2))(z)(2) + S(Ni(3))(z)(2)]. No evidence for long-range magnetic ordering was observed for crystalline samples of 1 or 2.     

Heterobimetallic Clusters of Copper(I) with Trithiotungstate and Trithiomolybdate. Synthesis and Characterization of the Octanuclear Clusters [Et(4)N](4)[M(4)Cu(4)S(12)O(4)] (M = Mo, W) and the Dodecanuclear Clusters [M(4)Cu(4)S(12)O(4)(CuTMEN)(4)] (M = Mo, W; TMEN = N,N,N',N'-Tetramethylethylenediamine)

Synthetic methods for [Et(4)N](4)[W(4)Cu(4)S(12)O(4)] (1), [Et(4)N](4)[Mo(4)Cu(4)S(12)O(4)] (2), [W(4)Cu(4)S(12)O(4)(CuTMEN)(4)] (3), and [Mo(4)Cu(4)S(12)O(4)(CuTMEN)(4)] (4) are described. [Et(4)N](2)[MS(4)], [Et(4)N](2)[MS(2)O(2)], Cu(NO(3))(2).3H(2)O, and KBH(4) (or Et(4)NBH(4)) were used as starting materials for the synthesis of 1 and 2. Compounds 3 and 4 were produced by reaction of [Et(4)N](2)[WOS(3)], Cu(NO(3))(2).3H(2)O, and TMEN and by reaction of [Me(4)N](2)[MO(2)O(2)S(8)], Cu(NO(3))(2).3H(2)O, and TMEN, respectively. Crystal structures of compounds 1-4 were determined. Compounds 1 and 2 crystallized in the monoclinic space group C2/c with a = 14.264(5) ?, b = 32.833(8) ?, c = 14.480(3) ?, beta = 118.66(2) degrees, V = 5950.8(5) ?(3), and Z = 4 for 1 and a = 14.288(5) ?, b = 32.937(10) ?, c = 14.490(3) ?, beta = 118.75(2) degrees, V = 5978.4(7) ?(3), and Z = 4 for 2. Compounds 3 and 4 crystallized in the trigonal space group P3(2)21 with a = 13.836(6) ?, c = 29.81(1) ?, V = 4942(4) ?(3), and Z = 3 for 3 and a = 13.756(9) ?, c = 29.80(2) ?, V = 4885(6) ?(3), and Z = 3 for 4. The cluster cores have approximate C(2v) symmetry. The anions of 1 and 2 may be viewed as consisting of two butterfly-type [CuMOS(3)Cu] fragments bridged by two [MOS(3)](2-) groups. Eight metal atoms in the anions are arranged in an approximate square configuration, with a Cu(4)M(4)S(12) ring structure. Compounds 3 and 4 can be considered to consist of one [M(4)Cu(4)S(12)O(4)](4-) (the anions of 1 and 2) unit capped by Cu(TMEN)(+) groups on each M atom; the Cu(TMEN)(+) groups extend alternately up and down around the Cu(4)M(4) square. The electronic spectra of the compounds are dominated by the internal transitions of the [MOS(3)](2-) moiety. (95)Mo NMR spectral data are investigated and compared with those of other compounds.     

Unusual Anions [LAl(SH)(S)]- and [LAl(S)2]2- stabilized by weakly coordinating imidazolium cations. synthesis of LAl(SSiMe2)2O (L = HC[C(Me)N(Ar)]2, Ar = 2,6-iPr2C6H3)

Deprotonation of an Al-SH moiety has been achieved easily by using N-heterocyclic carbene as the base. Monomeric mono- and bis-imidazolium salts [C(t)H(+)][LAl(SH)(S)](-) ([C(t)H(+)] = N,N'-bis-tert-butylimidazolium), [C(m)H(+)][LAl(SH)(S)](-), and [C(m)H(+)](2)[LAl(S)(2)](2-) ([C(m)H(+)] = N,N'-bismesitylimidazolium), containing unusual anions [LAl(SH)(S)](-) and [LAl(S)(2)](2-), have been synthesized in nearly quantitative yields. Furthermore, [C(m)H(+)](2)[LAl(S)(2)](2-) has been successfully used for the preparation of LAl(SSiMe(2))(2)O containing the [O(Me(2)SiS)(2)](2-) ligand.     

Coordination chemistry of silanedithiolato ligands derived from cyclotrisilathiane: synthesis and structures of complexes of iron(II), cobalt(II), palladium(II), copper(I), and silver(I)

The coordination chemistry of chelating silanedithiolato ligands has been investigated on Fe(II), Co(II), Pd(II), Cu(I), and Ag(I). Treatment of M(OAc)(2) (M = Fe, Co, Pd) with cyclotrisilathiane (SSiMe(2))(3) in the presence of Lewis bases resulted in formation of Fe(S(2)SiMe(2))(PMDETA) (1), Fe(S(2)SiMe(2))(Me(3)TACN) (2), Co(S(2)SiMe(2))(PMDETA) (3), and Pd(S(2)SiMe(2))(PEt(3))(2) (4) (PMDETA = N,N,N',N',N' '-pentamethyldiethylenetriamine; Me(3)TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane). The analogous reactions of M(OAc) (M = Cu, Ag) in the presence of PEt(3) gave rise to the dinuclear complexes M(2)[(SSiMe(2))(2)S](PEt(3))(3) [M = Cu (5), Ag (6)]. Complexes were characterized in solution by (1)H, (31)P[(1)H], and (29)Si[(1)H] NMR and in the solid state by single-crystal X-ray diffraction. Mononuclear complexes 1-3 have a four-membered MS(2)Si ring, and these five-coordinate complexes adopt trigonal-bipyramidal (for the PMDETA adducts) or square-pyramidal (for the Me(3)TACN adduct) geometries. In dimer 6, the (SSiMe(2))(2)S(2)(-) silanedithiolato ligand bridges two metal centers, one of which is three-coordinate and the other four-coordinate. The chelating effect of silanedithiolato ligands leads to an increase in the stability of silylated thiolato complexes.     

1,1-ethylenedithiolato complexes of palladium(II) and platinum(II) with isocyanide and carbene ligands

The reactions of [Tl(2)[S(2)C=C[C(O)Me](2)]](n) with [MCl(2)(NCPh)(2)] and CNR (1:1:2) give complexes [M[eta(2)-S(2)C=C[C(O)Me](2)](CNR)(2)] [R = (t)Bu, M = Pd (1a), Pt (1b); R = C(6)H(3)Me(2)-2,6 (Xy), M = Pd (2a), Pt (2b)]. Compound 1b reacts with AgClO(4) (1:1) to give [[Pt(CN(t)Bu)(2)](2)Ag(2)[mu(2),eta(2)-(S,S')-[S(2)C=C[C(O)Me](2)](2)]](ClO(4))(2) (3). The reactions of 1 or 2 with diethylamine give mixed isocyanide carbene complexes [M[eta(2)-S(2)C=C[C(O)Me](2)](CNR)[C(NEt(2))(NHR)]] [R = (t)Bu, M = Pd (4a), Pt (4b); R = Xy, M = Pd (5a), Pt (5b)] regardless of the molar ratio of the reagents. The same complexes react with an excess of ammonia to give [M[eta(2)-(S,S')-S(2)C=C[C(O)Me](2)](CN(t)Bu)[C(NH(2))(NH(t)Bu)]] [M = Pd (6a), Pt (6b)] or [M[eta(2)-(S,S')-S(2)C=C[C(O)Me](2)][C(NH(2))(NHXy)](2)] [M = Pd (7a), Pt (7b)] probably depending on steric factors. The crystal structures of 2b, 4a, and 4b have been determined. Compounds 4a and 4b are isostructural. They all display distorted square planar metal environments and chelating planar E,Z-2,2-diacetyl-1,1-ethylenedithiolato ligands that coordinate through the sulfur atoms.     

Titanium, zinc and alkaline-earth metal complexes supported by bulky O,N,N,O-multidentate ligands: syntheses, characterisation and activity in cyclic ester polymerisation

The reactions of the bulky amino-bis(phenol) ligand Me(2)NCH(2)CH(2)N[CH(2)-3,5-Bu(t)(2)-C(6)H(2)OH-2](2)(1-H(2)) with Zn[N(SiMe(3))(2)](2)(4), [Mg[N(SiMe(3))(2)](2)](2)(5) and Ca[N(SiMe(3))(2)](2)(THF)(2)(6) yield the complexes 1-Zn, 1-Mg and 1-Ca in good yields. The X-ray structure of 1-Ca showed the complex to be dimeric, with calcium in a distorted octahedral coordination geometry. Five of the positions are occupied by an N(2)O(3) donor set, while the sixth is taken up by an intramolecular close contact to an o-Bu(t) substituent, a rare case of a Ca...H-C agostic interaction (Ca...H distances of 2.37 and 2.41 Angstroms). Another sterically hindered calcium complex, Ca[2-Bu(t)-6-(C(6)F(5)N=CH)C(6)H(3)O](2)(THF)(2).(C(7)H(8))(2/3)(7), was prepared by reaction of 6 with the iminophenol 2-Bu(t)-6-(C(6)F(5)N=CH)C(6)H(3)OH (3-H). According to the crystal structure 7 is monomeric and octahedral, with trans THF ligands. The complex Ti[N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)O-2](2)[CH(2)CH(2)NMe(2)]](OPr(i))(2)(2-Ti) was prepared by treatment of Ti(OPr(i)(4)) with the new amino-bis(phenol) Me(2)NCH(2)CH(2)N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)OH-2](2)(2-H(2)). The reduction of 2-Ti with sodium amalgam gave the titanium(III) salt Ti[N[CH(2)-3-Bu(t)-5-Me-C(6)H(2)O-2](2)[CH(2)CH(2)NMe(2)]](OPr(i))(2).Na(THF)(2)(8). A comparison of the X-ray structures of 2-Ti and 8 showed that the additional electron in 8 significantly reduced the intensity of the pi-bonding from the oxygen atoms of the isopropoxide groups to titanium. 1-Ca and 8 were active initiators for the ring-opening polymerisation of epsilon-caprolactone (up to 97% conversion of 200 equivalents in 2 hours) and yielded polymers with narrow molecular weight distributions.     

Realization of unusual ligand binding motifs in metalated container molecules: synthesis, structures, and magnetic properties of the complexes [(LMe)Ni2(mu-L')]n+ with L'=NO3-, NO2-, N3-, N2H4, pyridazine, phthalazine, pyrazolate, and benzoate

A series of dinickel(II) complexes with the 24-membered macrocyclic hexaazadithiophenol ligand H(2)L(Me) was prepared and examined. The doubly deprotonated form (L(Me))(2-) forms complexes of the type [(L(Me))Ni2II(mu-L')](n+) with a bioctahedral N(3)Ni(II)(mu-SR)(2)(mu-L')Ni(II)N(3) core and an overall calixarene-like structure. The bridging coordination site L' is accessible for a wide range of exogenous coligands. In this study L'=NO(3)(-), NO(2)(-), N(3)(-), N(2)H(4), pyrazolate (pz), pyridazine (pydz), phthalazine (phtz), and benzoate (OBz). Crystallographic studies reveal that each substrate binds in a distinct fashion to the [(L(Me))Ni(2)](2+) portion: NO(2)(-), N(2)H(4), pz, pydz, and phtz form mu(1,2)-bridges, whereas NO(3)(-), N(3)(-), and OBz(-) are mu(1,3)-bridging. These distinctive binding motifs and the fact that some of the coligands adopt unusual conformations is discussed in terms of complementary host-guest interactions and the size and form of the binding pocket of the [(L(Me))Ni(2)](2+) fragment. UV/Vis and electrochemical studies reveal that the solid-state structures are retained in the solution state. The relative stabilities of the complexes indicate that the [(L(Me))Ni(2)](2+) fragment binds anionic coligands preferentially over neutral ones and strong-field ligands over weak-field ligands. Secondary van der Waals interactions also contribute to the stability of the complexes. Intramolecular ferromagnetic exchange interactions are present in the nitrito-, pyridazine-, and the benzoato-bridged complexes where J=+6.7, +3.5, and +5.8 cm(-1) (H=-2 JS(1)S(2), S(1)=S(2)=1) as indicated by magnetic susceptibility data taken from 300 to 2 K. In contrast, the azido bridge in [(L(Me))Ni(2)(mu(1,3)-N(3))](+) results in an antiferromagnetic exchange interaction J=-46.7 cm(-1). An explanation for this difference is qualitatively discussed in terms of bonding differences.     

A series of dinuclear homo- and heterometallic complexes with two or three bridging sulfido ligands derived from the tungsten tris(sulfido) complex [Et(4)N][(Me(2)Tp)WS(3)] (Me(2)Tp = hydridotris(3,5-dimethylpyrazol-1-yl)borate)

The generation of heterobimetallic complexes with two or three bridging sulfido ligands from mononuclear tris(sulfido) complex of tungsten [Et(4)N][(Me(2)Tp)WS(3)] (1; Me(2)Tp = hydridotris(3,5-dimethylpyrazol-1-yl)borate) and organometallic precursors is reported. Treatment of 1 with stoichiometric amounts of metal complexes such as [M(PPh(3))(4)] (M = Pt, Pd), [(PtMe(3))(4)(micro(3)-I)(4)], [M(cod)(PPh(3))(2)][PF(6)] (M = Ir, Rh; cod = 1,5-cyclooctadiene), [Rh(cod)(dppe)][PF(6)] (dppe = Ph(2)PCH(2)CH(2)PPh(2)), [CpIr(MeCN)(3)][PF(6)](2) (Cp = eta(5)-C(5)Me(5)), [CpRu(MeCN)(3)][PF(6)], and [M(CO)(3)(MeCN)(3)] (M = Mo, W) in MeCN or MeCN-THF at room temperature afforded either the doubly bridged complexes [Et(4)N][(Me(2)Tp)W(=S)(micro-S)(2)M(PPh(3))] (M = Pt (3), Pd (4)), [(Me(2)Tp)W(=S)(micro-S)(2)M(cod)] (M = Ir, Rh (7)), [(Me(2)Tp)W(=S)(micro-S)(2)Rh(dppe)], [(Me(2)Tp)W(=S)(micro-S)(2)RuCp] (10), and [Et(4)N][(Me(2)Tp)W(=S)(micro-S)(2)W(CO)(3)] (12) or the triply bridged complexes including [(Me(2)Tp)W(micro-S)(3)PtMe(3)] (5), [(Me(2)Tp)W(micro-S)(3)IrCp][PF(6)] (9), and [Et(4)N][(Me(2)Tp)W(micro-S)(3)Mo(CO)(3)] (11), depending on the nature of the incorporated metal fragment. The X-ray analyses have been undertaken to clarify the detailed structures of 3-5, 7, and 9-12.     

Synthesis, characterization, and structures of copper(II)-thiosulfate complexes incorporating tripodal tetraamine ligands

The reaction of [Cu(L)(H(2)O)](2+) with an excess of thiosulfate in aqueous solution produces a blue to green color change indicative of thiosulfate coordination to Cu(II) [L = tren, Bz(3)tren, Me(6)tren, and Me(3)tren; tren = tris(2-aminoethyl)amine, Bz(3)tren = tris(2-benzylaminoethyl)amine, Me(6)tren = tris(2,2-dimethylaminoethyl)amine, and Me(3)tren = tris(2-methylaminoethyl)amine]. In excess thiosulfate, only [Cu(Me(6)tren)(H(2)O)](2+) promotes the oxidation of thiosulfate to polythionates. Products suitable for single-crystal X-ray diffraction analyses were obtained for three thiosulfate complexes, namely, [Cu(tren)(S(2)O(3))].H(2)O, [Cu(Bz(3)tren)(S(2)O(3))].MeOH, and (H(3)Me(3)tren)[Cu(Me(3)tren)(S(2)O(3))](2)(ClO(4))(3). Isolation of [Cu(Me(6)tren)(S(2)O(3))] was prevented by its reactivity. In each complex, the copper(II) center is found in a trigonal bipyramidal (TBP) geometry consisting of four amine nitrogen atoms, with the bridgehead nitrogen in an axial position and an S-bound thiosulfate in the other axial site. Each structure exhibits H bonding (involving the amine ligand, thiosulfate, and solvent molecule, if present), forming either 2D sheets or 1D chains. The structure of [Cu(Me(3)tren)(MeCN)](ClO(4))(2) was also determined for comparison since no structures of mononuclear Cu(II)-Me(3)tren complexes have been reported. The thiosulfate binding constant was determined spectrophotometrically for each Cu(II)-amine complex. Three complexes yielded the highest values reported to date [K(f) = (1.82 +/- 0.09) x 10(3) M(-1) for tren, (4.30 +/- 0.21) x 10(4) M(-1) for Bz(3)tren, and (2.13 +/- 0.05) x 10(3) M(-1) for Me(3)tren], while for Me(6)tren, the binding constant was much smaller (40 +/- 10 M(-1)).     

(N2)3- radical chemistry via trivalent lanthanide salt/alkali metal reduction of dinitrogen: new syntheses and examples of (N2)2- and (N2)3- complexes and density functional theory comparisons of closed shell Sc3+, Y3+, and Lu3+ versus 4f(9) Dy3+

New syntheses of complexes containing the recently discovered (N(2))(3-) radical trianion have been developed by examining variations on the LnA(3)/M reductive system that delivers "LnA(2)" reactivity when Ln = scandium, yttrium, or a lanthanide, M = an alkali metal, and A = N(SiMe(3))(2) and C(5)R(5). The first examples of LnA(3)/M reduction of dinitrogen with aryloxide ligands (A = OC(6)R(5)) are reported: the combination of Dy(OAr)(3) (OAr = OC(6)H(3)(t)Bu(2)-2,6) with KC(8) under dinitrogen was found to produce both (N(2))(2-) and (N(2))(3-) products, [(ArO)(2)Dy(THF)(2)](2)(μ-η(2):η(2)-N(2)), 1, and [(ArO)(2)Dy(THF)](2)(μ-η(2):η(2)-N(2))[K(THF)(6)], 2a, respectively. The range of metals that form (N(2))(3-) complexes with [N(SiMe(3))(2)](-) ancillary ligands has been expanded from Y to Lu, Er, and La. Ln[N(SiMe(3))(2)](3)/M reactions with M = Na as well as KC(8) are reported. Reduction of the isolated (N(2))(2-) complex {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2)), 3, with KC(8) forms the (N(2))(3-) complex, {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2))[K(THF)(6)], 4a, in high yield. The reverse transformation, the conversion of 4a to 3 can be accomplished cleanly with elemental Hg. The crown ether derivative {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2))[K(18-crown-6)(THF)(2)] was isolated from reduction of 3 with KC(8) in the presence of 18-crown-6 and found to be much less soluble in tetrahydrofuran (THF) than the [K(THF)(6)](+) salt, which facilitates its separation from 3. Evidence for ligand metalation in the Y[N(SiMe(3))(2)](3)/KC(8) reaction was obtained through the crystal structure of the metallacyclic complex {[(Me(3)Si)(2)N](2)Y[CH(2)Si(Me(2))NSiMe(3)]}[K(18-crown-6)(THF)(toluene)]. Density functional theory previously used only with reduced dinitrogen complexes of closed shell Sc(3+) and Y(3+) was extended to Lu(3+) as well as to open shell 4f(9) Dy(3+) complexes to allow the first comparison of bonding between these four metals.     

Reactions of tetrakis(dimethylamide)-titanium, -zirconium and -hafnium with silanes: synthesis of unusual amide hydride complexes and mechanistic studies of titanium-silicon-nitride (Ti-Si-N) formation

M(NMe(2))(4) (M = Ti, Zr, Hf) were found to react with H(2)SiR'Ph (R' = H, Me, Ph) to yield H(2), aminosilanes, and black solids. Unusual amide hydride complexes [(Me(2)N)(3)M(mu-H)(mu-NMe(2))(2)](2)M (M = Zr, 1; Hf, 2) were observed to be intermediates and characterized by single-crystal X-ray diffraction. [(Me(2)N)(3)M(mu-D)(mu-NMe(2))(2)](2)M (1-d(2), 2-d(2)) were prepared through reactions of M(NMe(2))(4) with D(2)SiPh(2). Reactions of (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) with H(2)SiR'Ph were found to give aminosilanes and (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6). These reactions are reversible through unusual equilibria such as (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) + H(2)SiPh(2) right arrow over left arrow (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6) + HSi(NMe(2))Ph(2). The deuteride ligand in (Me(2)N)(2)Zr(D)Si(SiMe(3))(3) (6-d(1)) undergoes H-D exchange with H(2)SiR'Ph (R' = Me, H) to give 6 and HDSiR'Ph. The reaction of Ti(NMe(2))(4) with SiH(4) in chemical vapor deposition at 450 degrees C yielded thin Ti-Si-N ternary films containing TiN and Si(3)N(4). Ti(NMe(2))(4) reacts with SiH(4) at 23 degrees C to give H(2), HSi(NMe(2))(3), and a black solid. HNMe(2) was not detected in this reaction. The reaction mixture, upon heating, gave TiN and Si(3)N(4) powders. Analyses and reactivities of the black solid revealed that it contained -H and unreacted -NMe(2) ligands but no silicon-containing ligand. Ab initio quantum chemical calculations of the reactions of Ti(NR(2))(4) (R = Me, H) with SiH(4) indicated that the formation of aminosilanes and HTi(NR(2))(3) was favored. These calculations also showed that HTi(NH(2))(3) (3b) reacted with SiH(4) or H(3)Si-NH(2) in the following step to give H(2)Ti(NH(2))(2) (4b) and aminosilanes. The results in the current studies indicated that the role of SiH(4) in its reaction with Ti(NMe(2))(4) was mainly to remove amide ligands as HSi(NMe(2))(3). The removal of amide ligands is incomplete, and the reaction thus yielded "=Ti(H)(NMe(2))" as the black solid. Subsequent heating of the black solid and HSi(NMe(2))(3) may then yield TiN and Si(3)N(4), respectively, as the Ti-Si-N materials.     

Cyclo- and carbophosphazene-supported ligands for the assembly of heterometallic (Cu2+/Ca2+, Cu2+/Dy3+, Cu2+/Tb3+) complexes: synthesis, structure, and magnetism

The carbophosphazene and cyclophosphazene hydrazides, [{NC(N(CH(3))(2))}(2){NP{N(CH(3))NH(2)}(2)}] (1) and [N(3)P(3)(O(2)C(12)H(8))(2){N(CH(3))NH(2)}(2)] were condensed with o-vanillin to afford the multisite coordination ligands [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-OH)(m-OCH(3))}(2)}] (2) and [{N(2)P(2)(O(2)C(12)H(8))(2)}{NP{N(CH(3))N═CH-C (6)H(3)-(o-OH)(m-OCH(3))}(2)}] (3), respectively. These ligands were used for the preparation of heterometallic complexes [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuCa(NO(3))(2)}] (4), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{Cu(2)Ca(2)(NO(3))(4)}]·4H(2)O (5), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(4)}]·CH(3)COCH(3) (6), [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(3)}] (7), and [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuTb(NO(3))(3)}] (8). The molecular structures of these compounds reveals that the ligands 2 and 3 possess dual coordination pockets which are used to specifically bind the transition metal ion and the alkaline earth/lanthanide metal ion; the Cu(2+)/Ca(2+), Cu(2+)/Tb(3+), and Cu(2+)/Dy(3+) pairs in these compounds are brought together by phenoxide and methoxy oxygen atoms. While 4, 6, 7, and 8 are dinuclear complexes, 5 is a tetranuclear complex. Detailed magnetic properties on 6-8 reveal that these compounds show weak couplings between the magnetic centers and magnetic anisotropy. However, the ac susceptibility experiments did not reveal any out of phase signal suggesting that in these compounds slow relaxation of magnetization is absent above 1.8 K.     

Dinuclear cyano complexes of cobalt(III) and Iron(III) containing noninnocent 1,2,4,5-tetrakis(2-pyridinecarboxamido)benzene bridging ligands

Two new dinucleating ligands 1,2,4,5-tetrakis(2-pyridinecarboxamido)benzene, H(4)(tpb), and 1,2,4,5-tetrakis(4-tert-butyl-2-pyridinecarboxamido)benzene, H(4)(tbpb), have been synthesized, and the following dinuclear cyano complexes of cobalt(III) and iron(III) have been isolated: Na(2)[Co(III)(2)(tpb)(CN)(4)] (1); [N(n-Bu)(4)](2)[Co(III)(2)(tbpb)(CN)(4)] (2); [Co(III)(2)(tbpb(ox2))(CN)(4)] (3); [N(n-Bu)(4)](2)[Fe(III)(2)(tpb)(N(3))(4)] (4); [N(n-Bu)(4)](2)[Fe(III)(2)(tpb)(CN)(4)] (5); [N(n-Bu)(4)](2)[Fe(III)(2)(tbpb)(CN)(4)] (6). Complexes 2-4 and 6 have been structurally characterized by X-ray crystallography at 100 K. From electrochemical and spectroscopic (UV-vis, IR, EPR, M?ssbauer) and magnetochemical investigations it is established that the coordinated central 1,2,4,5-tetraamidobenzene entity in the cyano complexes can be oxidized in two successive one-electron steps yielding paramagnetic (tbpb(ox1))(3)(-) and diamagnetic (tbpb(ox2))(2)(-) anions. Thus, complex 6 exists in five characterized oxidation levels: [Fe(III)(2)(tbpb(ox2))(CN)(4)](0) (S = 0); [Fe(III)(2)(tbpb(ox1))(CN)(4)](-) (S = (1)/(2)); [Fe(III)(2)(tbpb)(CN)(4)](2)(-) (S = 0); [Fe(III)Fe(II)(tbpb)(CN)(4)](3)(-) (S = (1)/(2)); [Fe(II)(2)(tbpb)(CN)(4)](4)(-) (S = 0). The iron(II) and (III) ions are always low-spin configurated. The electronic structure of the paramagnetic iron(III) ions and the exchange interaction of the three-spin system [Fe(III)(2)(tbpb(ox1))(CN)(4)](-) are characterized in detail. Similarly, for 2 three oxidation levels have been identified and fully characterized: [Co(III)(2)(tbpb)(CN)(4)](2)(-) (S = 0); [Co(III)(2)(tbpb(ox1))(CN)(4)](-) (S = (1)/(2)); [Co(III)(2)(tbpb(ox2))(CN)(4)](0). The crystal structures of 2 and 3 clearly show that the two electron oxidation of 2 yielding 3 affects only the central tetraamidobenzene part of the ligand.     

Extended network thiocyanate- and tetracyanoethanide-based first-row transition metal complexes

Linear chain thiocyanate complexes of M(NCS)(2)(OCMe(2))(2) (M = Fe, Mn, Cr) composition have been prepared and structurally, chemically, and magnetically characterized. Fe(NCS)(2)(OCMe(2))(2) exhibits metamagnetic-like behavior, and orders as an antiferromagnet at 6 K. The Mn and Cr compounds are antiferromagnets with T(c) of 30 and 50 K, respectively, with J/k(B) = -3.5 (-2.4 cm(-1)) and -9.9 K (-6.9 cm(-1)), respectively, when fit to one-dimensional (1-D) Fisher chain model (H = -2JS(i)·S(j)). Co(NCS)(2) was prepared by a new synthetic route, and powder diffraction was used to determine its structure to be a two-dimensional (2-D) layer with μ(N,S,S)-NCS motif, and it is an antiferromagnet (T(c) = 22 K; θ = -33 K for T > 25 K). M(NCS)(2)(OCMe(2))(2) (M = Fe, Mn) and Co(NCS)(2) react with (NBu(4))(TCNE) in dichloromethane to form M(TCNE)[C(4)(CN)(8)](1/2), and in acetone to form M[C(4)(CN)(8)](OCMe(2))(2) (M = Fe, Mn, Co). These materials possess μ(4)-[C(4)(CN)(8)](2-) that form 2-D layered structural motifs, which exhibit weak antiferromagnetic coupling. Co(TCNE)[C(4)(CN)(8)](1/2) behaves as a paramagnet with strong antiferromagnetic coupling (θ = -50 K).     

Synthesis and structural characterization of PHP[(C(5)Me(4))(2)], a monodentate chiral phosphine derived from intramolecular C-C coupling of tetramethylcyclopentadienyl groups: an evaluation of steric and electronic properties

The chiral monodentate phosphine PhP[(C(5)Me(4))(2)] is readily obtained by oxidation of the lithium complex Li(2)[PhP(C(5)Me(4))(2)] with I(2), which couples the two cyclopentadienyl groups to form a five-membered heterocyclic ring. The steric and electronic properties of PhP[(C(5)Me(4))(2)] have been evaluated by X-ray diffraction and IR spectroscopic studies on a variety of derivatives, including Ph[(C(5)Me(4))(2)]PE (E = S, Se), Cp*MCl(4)[P[(C(5)Me(4))(2)]Ph] (M = Mo, Ta), Ir[P[(C(5)Me(4))(2)]Ph](2)(CO)Cl, and CpFe(CO)[PhP[(C(5)Me(4))(2)]]Me. For comparison purposes, derivatives of the related phospholane ligand PhP[Me(2)C(4)H(6)] have also been investigated, including Ph[Me(2)C(4)H(6)]PS, Ir[Ph[Me(2)C(4)H(6)]](2)(CO)Cl, Ir[Ph[Me(2)C(4)H(6)]](2)(CO)Me, Ir[PPh[Me(2)C(4)H(6)]](COD)(Cl), and Pd[P[Me(2)C(4)H(6)]Ph][eta(2)-C(6)H(4)C(H)(Me)NMe(2)]Cl. The steric and electronic properties of PhP[(C(5)Me(4))(2)] are determined to be intermediate between those of PPh(2)Me and PPh(3). Thus, the crystallographic cone angles increase in the sequence PPh(2)Me (134.5 degrees) < PhP[(C(5)Me(4))(2)] (140.2 degrees) < PPh(3) (148.2 degrees), while the electron donating abilities decrease in the sequence PPh(2)Me > PhP[(C(5)Me(4))(2)] > PPh(3). Finally, PhP[(C(5)Me(4))(2)] has a smaller cone angle and is less electron donating than the structurally similar phosphine, PhP[Me(2)C(4)H(6)].     

Synthesis, structure and DFT study of dinuclear iron, cobalt and nickel complexes with cyclopentadienyl-metal moieties

Reactions of 1,1'-bis(dipheny1phosphino)cobaltocene with Co(PMe(3))(4), Ni(PMe(3))(4), Fe(PMe(3))(4), Ni(COD)(2), FeMe(2)(PMe(3))(4) or NiMe(2)(PMe(3))(3) afford a series of novel dinuclear complexes [((Me(3)P)[lower bond 1 start]Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2)))((Me(3)P)M[upper bond 1 end](η(5)-C(5)H(4)P[lower bond 1 end]Ph(2)))] (M = Co(1), Ni(2) and Fe(3)) [Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)Ni[upper bond 1 end](COD)](4), [Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)Ni[upper bond 1 end](PMe(3))(2)] (5) and [((Me(3)P)[lower bond 1 start]Co(Me)(η(5)-C(5)H(4)[upper bond 1 start]PPh(2)))((Me(3)P)Fe[upper bond 1 end](Me)(η(5)-C(5)H(4)P[lower bond 1 end]Ph(2)))] (6). Reactions of 1,1'-bis(dipheny1phosphino)ferrocene with Ni(PMe(3))(4), NiMe(2)(PMe(3))(3), or Co(PMe(3))(4) gives rise to complexes [Fe(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)M[upper bond 1 end](PMe(3))(2)] (M = Ni (7), Co (8)). The complexes 1-8 were spectroscopically investigated and studied by X-ray single crystal diffraction. The possible reaction mechanisms and structural characteristics are discussed. Density functional theory (DFT) calculations strongly support the deductions.     

Trivalent [(C5Me5)2(THF)Ln]2(mu-eta2:eta2-N2) complexes as reducing agents including the reductive homologation of CO to a ketene carboxylate, (mu-eta4-O2C-C=C=O)2-

The [Z(2)Ln(THF)](2)(mu-eta(2)():eta(2)()-N(2)) complexes (Z = monoanionic ligand) generated by reduction of dinitrogen with trivalent lanthanide salts and alkali metals are strong reductants in their own right and provide another option in reductive lanthanide chemistry. Hence, lanthanide-based reduction chemistry can be effected in a diamagnetic trivalent system using the dinitrogen reduction product, [(C(5)Me(5))(2)(THF)La](2)(mu-eta(2)():eta(2)()-N(2)), 1, readily obtained from [(C(5)Me(5))(2)La][BPh(4)], KC(8), and N(2). Complex 1 reduces phenazine, cyclooctatetraene, anthracene, and azobenzene to form [(C(5)Me(5))(2)La](2)[mu-eta(3):eta(3)-(C(12)H(8)N(2))], 2, (C(5)Me(5))La(C(8)H(8)), 3, [(C(5)Me(5))(2)La](2)[mu-eta(3):eta(3)-(C(14)H(10))], 4, and [(C(5)Me(5))La(mu-eta(2)-(PhNNPh)(THF)](2), 5, respectively. Neither stilbene nor naphthalene are reduced by 1, but 1 reduces CO to make the ketene carboxylate complex {[(C(5)Me(5))(2)La](2)[mu-eta(4)-O(2)C-C=C=O](THF)}(2), 6, that contains CO-derived carbon atoms completely free of oxygen.