Synthesis and characterization of iron complexes with monoanionic and dianionic N,N',N' '-trialkylguanidinate ligands

Trisubstitued N,N',N' '-tri(alkyl)guanidinate anions have been used in the synthesis of a family of Fe(II) and Fe(III) complexes. Complexes FeCl[((i)PrN)(2)C(HN(i)Pr)](2) (1), [Fe[micro-((i)PrN)(2)C(HN(i)Pr)][((i)PrN)(2)C(HN(i)Pr)]](2) (2), and [Fe[mgr;-(CyN)(2)C(HNCy)][(CyN)(2)C(HNCy)]](2) (3) were prepared from the reaction of the appropriate lithium tri(alkyl)guanidinate and FeCl(3) or FeBr(2). The complex [FeBr[micro-(CyN)(2)C(HNCy)]](2) (4), an apparent intermediate in the formation of 3, has also been isolated and characterized. Complexes 1 and 2 react with alkyllithium reagents to yield products that depend on the identity of the reagent as well as the reaction stoichiometry. Reaction of 2 with MeLi (1:2 ratio) produces Li(2)[Fe[micro-((i)PrN)(2)C=N(i)Pr][((i)PrN)(2)C(HN(i)Pr)]](2) (5). Reaction of 1 with an equimolar amount of LiCH(2)SiMe(3) results in reduction to Fe(II) and generation of 2 while reaction with 4 LiCH(2)SiMe(3) proceeds by a combination of reduction, substitution, and deprotonation of guandinate to yield Li(4)(THF)(2)[Fe[((i)PrN)(2)CN(i)Pr](CH(2)SiMe(3))(2)](2) (7). Both complexes 5 and 7 posssess dianionic guanidinate ligands. The reaction of 2 with 1 equiv of LiCH(2)SiMe(3) generated Fe(2)[micro-((i)PrNCN(i)Pr)(2)(N(i)Pr)][((i)PrN)(2)C(HN(i)Pr)](2) (6). Compound 6 has a dianionic biguanidinate ligand derived from the coupling of the two bridging guanidinate ligands of 2.     

Extensively Conjugated Dianionic Tetrathiooxalate-Bridged Copper(II) Complexes for Synthetic Metals

Using a unique three-solvent biphasic method, we have prepared and characterized three new fully conjugated, chalcogen-rich, bridged copper(II) complexes for the preparation of molecular conductors and magnetic materials, having the general formula (Bu(4)N)(2){tto[Cu(L)](2)} (tto = C(2)S(4)(2)(-) = tetrathiooxalato; L = mnt = C(4)N(2)S(2)(2)(-) = 1,2-dicyanoethene-1,2-dithiolato for complex 2, dsit = C(3)Se(2)S(3)(2)(-) = 2-thioxo-1,3-dithiole-4,5-diselenolato for complex 3, dmid = C(3)OS(4)(2)(-) = 2-oxo-1,3-dithiole-4,5-dithiolato for complex 4a). The single-crystal X-ray structures of 2 and 3 have been determined: 2, (Bu(4)N)(2){tto[Cu(mnt)](2)}, monoclinic, space group C2/m, a = 19.549(4) ?, b = 13.519(3) ?, c = 10.162(2) ?, beta = 90.33(1) degrees, Z = 2; 3, (Bu(4)N)(2){tto[Cu(dsit)](2)}, monoclinic, space group P2(1)/c, a = 9.903(1) ?, b = 15.589(1) ?, c = 18.218(1) ?, beta = 90.40(1) degrees, Z = 2. Complex 2 displays perfect planarity, while 3 shows a slight tetrahedral distortion at the metal centers, resulting in a dihedral angle of 24.86(3) degrees. Cyclic voltammetry of (Bu(4)N)(2){tto[Cu(mnt)](2)} (2), (Bu(4)N)(2){tto[Cu(dsit)](2)} (3), and (Bu(4)N)(2){tto[Cu(dmid)](2)} (4a) shows each complex to exhibit two reversible redox processes which can be attributed to {tto[Cu(L)](2)}(2)(-) right arrow over left arrow tto[Cu(L)](2)}(-) and {tto[Cu(L)](2)}(1)(-) right arrow over left arrow {tto[Cu(L)](2)}(0) couples. The structural and electronic properties of 2, 3, and 4a will be compared to those of the recently communicated analogous complex (Bu(4)N)(2){tto[Cu(dmit)](2)} (1).     

Catalytic addition of amine N-H bonds to carbodiimides by half-sandwich rare-earth metal complexes: efficient synthesis of substituted guanidines through amine protonolysis of rare-earth metal guanidinates

Reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] (Ln=Y, Yb, and Lu) with one equivalent of Me(2)Si(C(5)Me(4)H)NHR' (R'=Ph, 2,4,6-Me(3)C(6)H(2), tBu) affords straightforwardly the corresponding half-sandwich rare-earth metal alkyl complexes [{Me(2)Si(C(5)Me(4))(NR')}Ln(CH(2)SiMe(3))(thf)(n)] (1: Ln = Y, R' = Ph, n=2; 2: Ln = Y, R' = C(6)H(2)Me(3)-2,4,6, n=1; 3: Ln = Y, R' = tBu, n=1; 4: Ln = Yb, R' = Ph, n=2; 5: Ln = Lu, R' = Ph, n=2) in high yields. These complexes, especially the yttrium complexes 1-3, serve as excellent catalyst precursors for the catalytic addition of various primary and secondary amines to carbodiimides, efficiently yielding a series of guanidine derivatives with a wide range of substituents on the nitrogen atoms. Functional groups such as C[triple chemical bond]N, C[triple chemical bond]CH, and aromatic C--X (X: F, Cl, Br, I) bonds can survive the catalytic reaction conditions. A primary amino group can be distinguished from a secondary one by the catalyst system, and therefore, the reaction of 1,2,3,4-tetrahydro-5-aminoisoquinoline with iPrN==C==NiPr can be achieved stepwise first at the primary amino group to selectively give the monoguanidine 38, and then at the cyclic secondary amino unit to give the biguanidine 39. Some key reaction intermediates or true catalyst species, such as the amido complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y(NEt(2))(thf)(2)] (40) and [{Me(2)Si(C(5)Me(4))(NPh)}Y(NHC(6)H(4)Br-4)(thf)(2)] (42), and the guanidinate complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrNC(NEt(2))(NiPr)}(thf)] (41) and [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrN}C(NC(6)H(4)Br-4)(NHiPr)}(thf)] (44) have been isolated and structurally characterized. Reactivity studies on these complexes suggest that the present catalytic formation of a guanidine compound proceeds mechanistically through nucleophilic addition of an amido species, formed by acid-base reaction between a rare-earth metal alkyl bond and an amine N--H bond, to a carbodiimide, followed by amine protonolysis of the resultant guanidinate species.     

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.     

Spectrophotometric studies on ion-pair extraction equilibria of the iron(ii) and iron(III) complexes with 4-(2-pyridylazo)resorcinol

The ion-pair extraction equilibria of the iron(II) and iron(III) chelates of 4-(2-pyridylazo)resorcinol (PAR, H(2)L) are described. The anionic chelates were extracted into chloroform with benzyldimethyltetradecylammonium chloride (QC1) as counter-ion. The extraction constants were estimated to be K(ex1)(Fe(II)) = [Q{Fe(II)(HL)L}](0)/[Q(+)][{Fe(II)(HL)L}(-)] = 10(8.59 +/- 0.11), K(ex2)(Fe(II)) = [Q(2){Fe(II)L(2)}](o)/ [Q(+)](2)[{Fe(II)L(2)}(2-)] = 10(12.17 +/- 0.10) and K(ex1)(Fe(III)) = [Q{Fe((III))L(2)}](o)/(Q(+)][{Fe(III)L(2)}(-)] = 10(6.78 +/- 0.15) at I = 0.10 and 20 degrees , where [ ](o) is concentration in the chloroform phase. Aggregation of Q{Fe(III)L(2)} in chloroform was observed and the dimerization constant (K(d) = [Q(2){Fe(III)L(2)}(2)](o)/[Q{Fe(III)L(2)}](o)(2)) was evaluated as log K(d) = 4.3 +/- 0.3 at 20 degrees . The neutral chelates of {Fe(II)(HL)(2)} and {Fe(III)(HL)L}, and the ion-pair of the cationic chelate, {Fe(III)(HL)(2)}ClO(4), were also extracted into chloroform or nitrobenzene. The relationship between the forms and extraction properties of the iron(II) and iron(III) PAR chelates are discussed in connection with those of the nickel(II) and cobalt(III) complexes. Correlation between the extraction equilibrium data and the elution behaviour of some PAR chelates in ion-pair reversed-phase partition chromatography is also discussed.     

Transition metal complexes with wide-angle dithio-, diseleno- and ditelluroethers: properties and structural systematics

The ligands o-C(6)H(4)(CH(2)EMe)(2) (E = S or Se) have been prepared and characterised spectroscopically. A systematic study of the coordination chemistry of these, together with the telluroether analogue, o-C(6)H(4)(CH(2)TeMe)(2), with late transition metal centers has been undertaken. The planar complexes [MCl(2){o-C(6)H(4)(CH(2)SMe)(2)}] and [M{o-C(6)H(4)(CH(2)EMe)(2)}(2)](PF(6))(2) (M = Pd or Pt; E = S or Se), the distorted octahedral [RhCl(2){o-C(6)H(4)(CH(2)EMe)(2)}(2)]Y (E = S or Se: Y = PF(6); E = Te: Y = Cl) and [RuCl(2){o-C(6)H(4)(CH(2)EMe)(2)}(2)] (E = S, Se or Te), the dithioether-bridged binuclear [{RuCl(2)(p-cymene)}(2){micro-o-C(6)H(4)(CH(2)SMe)(2)}] and the tetrahedral [M'{o-C(6)H(4)(CH(2)EMe)(2)}(2)]BF(4) (M' = Cu or Ag; E = S, Se or Te) have been obtained and characterised by IR and multinuclear NMR spectroscopy ((1)H, (63)Cu, (77)Se{(1)H}, (125)Te{(1)H} and (195)Pt), electrospray MS and microanalyses. Crystal structures of the parent o-C(6)H(4)(CH(2)SMe)(2) and seven complexes are described, which show three different stereoisomeric forms for the chelated ligands, as well as the first example of a bridging coordination mode in [{RuCl(2)(p-cymene)}(2){micro-o-C(6)H(4)(CH(2)SMe)(2)}]. These studies reveal the consequences of the sterically demanding o-xylyl backbone, which typically leads to unusually obtuse E-M-E chelate angles of approximately 100 degrees .     

Selective reaction based on the linked diamido ligands of dinuclear lanthanide complexes

The dinuclear ytterbium pyridyl diamido complexes [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,6)] (1a) and [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,3)] (1b) are easily prepared by protonolysis of Cp(3)Yb with 0.5 equiv of the corresponding diaminopyridine in accepted yields, respectively. Treatment of 1a with 2 equiv of dicyclohexylcarbodiimide (CyN=C=NCy) in THF at low temperature leads to the isolation of the formal double N-H addition product (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyN(CyNH)CN)(2)(C(5)H(3)N-2,6)] (2) in 42% yield. Compound 2 is unstable to heat and slowly isomerized to the mixed neutral/dianionic diguanidinate complex (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyNH)(2)CN(C(5)H(3)N-2,6)NC(NCy)(2)](THF) (3) at room temperature. Similarly, treatment of 1b with 2 equiv of CyN=C=NCy gives the addition/ isomerization product (Cp(2)Yb)(2)[mu-eta(2):eta(2):eta(1)-(CyNH)(2)CN(C(5)H(3)N-2,3)NC(NCy)(2)] (4). Moreover, the reaction of various ytterbium aryl diamido complexes (prepared in situ from [Cp(2)YbMe](2) and aryldiamine, respectively) with CyN=C=NCy affords the corresponding addition products (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,4)] (5), (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,3)](6), and (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(13)H(8)-2,7)] (7), respectively. In contrast to pyridyl-bridged bis(guanidinate monoanion) complexes, aryl-bridged bis(guanidinate monoanion) complexes 5-7 are stable even with prolonged heating at 110 degrees C. All the results not only demonstrate that the presence of the pyridyl bridge can impart the diamido complexes with a unique reactivity and initiate the unexpected reaction sequence but also indicate evidently that the number and distribution of negative charges of the diguanidinate ligand is tunable from double monoanionic units to mixed neutral/dianionic isomers. All the complexes are characterized by elemental analysis and IR spectroscopies. The structures of complexes 1a, 3, 5, 6, and 7 are also determined through X-ray single-crystal diffraction analysis.     

Carbophosphazene-supported ligand systems containing pyrazole/guanidine coordinating groups

Carbophosphazene-based coordination ligands [{NC(NMe(2))}(2){NP(3,5-Me(2)Pz)(2)}] (1), [{NC(NEt)(2)}{NC(3,5-Me(2)Pz)}{NP(3,5-Me(2)Pz)(2)}] (2), [NC(3,5-Me(2)Pz)](2)[NP(3,5-Me(2)Pz)(2)] (3), [{NCCl}(2){NP(NC(NMe(2))(2))(2)}] (4), and [{NC(p-OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}] (5) were synthesized and structurally characterized. In these compounds, the six-membered C(2)N(3)P ring is perfectly planar. The reaction of 1 with CuCl(2) afforded [{NC(NMe(2))}(2){NHP(O)(3,5-Me(2)Pz)}·{Cu(3,5-Me(2)PzH)(2)(Cl)}][Cl] (6). The ligand binds to Cu(II) utilizing the geminal [P(O)(3,5-Me(2)Pz)] coordinating unit. Similarly, the reaction of 2 with PdCl(2) afforded, after a metal-assisted P-N hydrolysis, [{NC(NEt)(2)}{NC(3,5-Me(2)Pz)}{NP(O)(3,5-Me(2)Pz)}·{Pd(3,5-Me(2)PzH)(Cl)}] (7). In the latter, the [P(O)(3,5-Me(2)Pz)] unit does not coordinate; in this instance, the Pd(II) is bound by a ring nitrogen atom and a carbon-tethered pyrazolyl nitrogen atom. The reaction of 3 with PdCl(2) also results in P-N bond hydrolysis affording [{NC(3,5-Me(2)Pz)(2)}{NP(O)(3,5-Me(2)Pz)}{Pd(Cl)}] (8). In contrast to 7, however, in 8, the Pd(II) elicits a nongeminal η(3) coordination from the ligand involving two carbon-tethered pyrazolyl groups and a ring nitrogen atom. Metalated products could not be isolated in the reaction of 3 with K(2)PtCl(4). Instead, a P-O-P bridged carbodiphosphazane dimer, [{NC(3,5-Me(2)Pz)NHC(3,5-Me(2)Pz)}{NP(O)}](2) (9), was isolated as the major product. Finally, the reaction of 5 with PdCl(2) resulted in [{NC(OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}·{PdCl(2)}] (10). In the latter, the exocyclic P-N bonds are quite robust and are involved in binding to the metal ion. Compounds 6-10 have been characterized by a variety of techniques including X-ray crystallography. In all of the compounds, the bond parameters of the inorganic heterocyclic rings are affected by metalation.     

Novel polyoxometalate hybrids consisting of copper-lanthanide heterometallic/lanthanide germanotungstate fragments

Three organic-inorganic hybrid copper-lanthanide heterometallic germanotungstates, {[Cu(en)(2)(H(2)O)] [Cu(3)Eu(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)·11H(2)O (1), {[Cu(en)(2)(H(2)O)][Cu(3)Tb(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)·11H(2)O (2) and {[Cu(en)(2)(H(2)O)][Cu(3)Dy(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)·10H(2)O (3) and three polyoxometalate hybrids built by lanthanide-containing germanotungstates and copper-ethylendiamine complexes, Na(2)H(6)[Cu(en)(2)(H(2)O)](8){Cu(en)(2)[La(α-GeW(11)O(39))(2)](2)}·18H(2)O (4), K(4)H(2)[Cu(en)(2)(H(2)O)(2)](5)[Cu(en)(2)(H(2)O)](2)[Cu(en)(2)](2){Cu(en)(2)[Pr(α-GeW(11)O(39))(2)](2)}·16H(2)O (5) and KNa(2)H(7)[enH(2)](3)[Cu(en)(2)(H(2)O)](2)[Cu(en)(2)](2){Cu(en)(2)[Er(α-GeW(11)O(39))(2)](2)}·15H(2)O (6) (en = ethylenediamine) have been hydrothermally synthesized and structurally characterized by elemental analyses, inductively coupled plasma atomic emission spectrometry (ICP-AES) analyses, IR spectra, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS) and single-crystal X-ray diffraction. 1-3 are essentially isomorphous and their main skeletons display the interesting dimeric motif {[Cu(3)Ln(en)(3)(OH)(3)(H(2)O)(2)](α-GeW(11)O(39))}(2)(4-), which is constructed from two {Cu(3)LnO(4)} cubane anchored monovacant [α-GeW(11)O(39)](8-) fragments through two W-O-Ln-O-W linkers. The primary backbones of 4-6 exhibit the tetrameric architecture {Cu(en)(2)[Ln(α-GeW(11)O(39))(2)](2)}(24-) built by two 1?:?2-type [Ln(α-GeW(11)O(39))(2)](13-) moieties and one [Cu(en)(2)](2+) bridge, albeit they are not isostructural. To our knowledge, 1-6 are rare polyoxometalate derivatives consisting of copper-lanthanide heterometallic/lanthanide germanotungstate fragments. 1 exhibits antiferromagnetic coupling interactions within the {Cu(3)EuO(4)} cubane units, while 2 and 3 display dominant ferromagnetic interactions between the Tb(III)/Dy(III) and Cu(II) cations. The room-temperature solid-state photoluminescence properties of 1-3 have been investigated.     

Synthesis and structure of two new (guanidinate)boron dichlorides and their attempted conversion to boron(I) derivatives

To test the feasibility of the guanidinate architecture for the support of boron(i) carbene analogues the energy gap between the singlet and triplet states of the model compound, [Me(2)NC{N(Ph)}(2)B:] (), has been probed by both DFT and second order M?ller-Plesset (MP2) methods. The singlet state is calculated to be more stable than the triplet state by between 6.0 and 10.1 kcal mol(-1). The new (guanidinate)boron dichlorides [Ph(2)NC{N(Mes)(2)]BCl(2) () and [Ph(2)NC{N(Dipp)(2)]BCl(2) () have been prepared and characterized by single-crystal X-ray diffraction. Attempts to reduce and to the corresponding boron(i) species were not successful.     

Amidoximes provide facile platinum(II)-mediated oxime-nitrile coupling

The nucleophilic addition of amidoximes R'C(NH(2))═NOH [R' = Me (2.Me), Ph (2.Ph)] to coordinated nitriles in the platinum(II) complexes trans-[PtCl(2)(RCN)(2)] [R = Et (1t.Et), Ph (1t.Ph), NMe(2) (1t.NMe(2))] and cis-[PtCl(2)(RCN)(2)] [R = Et (1c.Et), Ph (1c.Ph), NMe(2) (1c.NMe(2))] proceeds in a 1:1 molar ratio and leads to the monoaddition products trans-[PtCl(RCN){HN═C(R)ONC(R')NH(2)}]Cl [R = NMe(2); R' = Me ([3a]Cl), Ph ([3b]Cl)], cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}] [R = NMe(2); R' = Me (4a), Ph (4b)], and trans/cis-[PtCl(2)(RCN){HN═C(R)ONC(R')NH(2)}] [R = Et; R' = Me (5a, 6a), Ph (5b, 6b); R = Ph; R' = Me (5c, 6c), Ph (5d, 6d), correspondingly]. If the nucleophilic addition proceeds in a 2:1 molar ratio, the reaction gives the bisaddition species trans/cis-[Pt{HN═C(R)ONC(R')NH(2)}(2)]Cl(2) [R = NMe(2); R' = Me ([7a]Cl(2), [8a]Cl(2)), Ph ([7b]Cl(2), [8b]Cl(2))] and trans/cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}(2)] [R = Et; R' = Me (10a), Ph (9b, 10b); R = Ph; R' = Me (9c, 10c), Ph (9d, 10d), respectively]. The reaction of 1 equiv of the corresponding amidoxime and each of [3a]Cl, [3b]Cl, 5b-5d, and 6a-6d leads to [7a]Cl(2), [7b]Cl(2), 9b-9d, and 10a-10d. Open-chain bisaddition species 9b-9d and 10a-10d were transformed to corresponding chelated bisaddition complexes [7d](2+)-[7f](2+) and [8c](2+)-[8f](2+) by the addition of 2 equiv AgNO(3). All of the complexes synthesized bear nitrogen-bound O-iminoacylated amidoxime groups. The obtained complexes were characterized by elemental analyses, high-resolution ESI-MS, IR, and (1)H NMR techniques, while 4a, 4b, 5b, 6d, [7b](Cl)(2), [7d](SO(3)CF(3))(2), [8b](Cl)(2), [8f](NO(3))(2), 9b, and 10b were also characterized by single-crystal X-ray diffraction.     

Lithium aluminates on a molecular titanium oxide

Lithium aluminates Li[Al(O-2,6-Me(2)C(6)H(3))R'(3)] (R' = Et, Ph) react with the μ(3)-alkylidyne oxoderivative ligands [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CR)] [R = H (1), Me (2)] to afford the aluminum-lithium-titanium cubane complexes [{R'(3)Al(μ-O-2,6-Me(2)C(6)H(3))Li}(μ(3)-O)(3){Ti(η(5)-C(5)Me(5))}(3)(μ(3)-CR)] [R = H, R' = Et (5), Ph (7); R = Me, R' = Et (6), Ph (8)]. Complex 7 evolves with the formation of a lithium dicubane species and a Li{Al(μ-O-2,6-Me(2)C(6)H(3))Ph(3)}(2)] unit.     

Two novel cyanide-bridged bimetallic magnetic chains derived from manganese(III) Schiff bases and hexacyanochromate(III) building blocks

Two novel complexes, [{Mn(salen)}(2){Mn(salen)(CH(3)OH)}{Cr(CN)(6)}](n)·2nCH(3)CN·nCH(3)OH (1) and [Mn(5-Clsalmen)(CH(3)OH)(H(2)O)](2n)[{Mn(5-Clsalmen)(μ-CN)}Cr(CN)(5)](n)·5.5nH(2)O (2) (salen(2-) = N,N'-ethylene-bis(salicylideneiminato) dianion; 5-Clsalmen(2-) = N,N'-(1-methylethylene)-bis(5-chlorosalicylideneiminato) dianion), were synthesized and structurally characterized by X-ray single-crystal diffraction. The structural analyses show that complex 1 consists of one-dimensional (1D) alternating chains formed by the [{Cr(CN)(6)}{Mn(salen)}(4){Mn(salen)(CH(3)OH)}(2)](3+) heptanuclear cations and [Cr(CN)(6)](3-) anions. While in complex 2, the hexacyanochromate(III) anion acts as a bis-monodentate ligand through two trans-cyano groups to bridge two [Mn(5-Clsalmen)](+) cations to form a straight chain. The magnetic analysis indicates that complex 1 shows three-dimensional (3D) antiferromagnetic ordering with the Ne?el temperature of 5.0 K, and it is a metamagnet displaying antiferromagnetic to ferromagnetic transition at a critical field of about 2.6 kOe at 2 K. Complex 2 behaves as a molecular magnet with Tc = 3.0 K.     

Bulky guanidinato nickel(I) complexes: synthesis, characterization, isomerization, and reactivity studies

Reactions of lithium complexes of the bulky guanidinates [{(Dip)N}(2)CNR(2)](-) (Dip=C(6)H(3)iPr(2)-2,6; R=C(6)H(11) (Giso(-)) or iPr (Priso(-)), with NiBr(2) have afforded the nickel(II) complexes [{Ni(L)(μ-Br)}(2)] (L=Giso(-) or Priso(-)), the latter of which was crystallographically characterized. Reduction of [{Ni(Priso)(μ-Br)}(2)] with elemental potassium in benzene or toluene afforded the diamagnetic species [{Ni(Priso)}(2)(μ-C(6)H(5)R)] (R=H or Me), which were shown, by X-ray crystallographic studies, to possess nonplanar bridging arene ligands that are partially reduced. A similar reduction of [{Ni(Priso)(μ-Br)}(2)] in cyclohexane yielded a mixture of the isomeric complexes [{Ni(μ-κ(1)-N-,η(2)-Dip-Priso)}(2)] and [{Ni(μ-κ(2)-N,N'-Priso)}(2)], both of which were structurally characterized. These complexes were also formed through arene elimination processes if [{Ni(Priso)}(2)(μ-C(6)H(5)R)] (R=H or Me) were dissolved in hexane. In that solvent, diamagnetic [{Ni(μ-κ(1)-N-,η(2)-Dip-Priso)}(2)] was found to slowly convert to paramagnetic [{Ni(μ-κ(2)-N,N'-Priso)}(2)], suggesting that the latter is the thermodynamic isomer. Computational analysis of a model of [{Ni(μ-κ(2)-N,N'-Priso)}(2)] showed it to have a Ni-Ni bond that has a multiconfigurational electronic structure. An analogous copper(I) complex [{Cu(μ-κ(2)-N,N'-Giso)}(2)] was prepared, structurally authenticated, and found, by a theoretical study, to have a negligible Cu···Cu bonding interaction. The reactivity of [{Ni(Priso)}(2)(μ-C(6)H(5)Me)] and [{Ni(μ-κ(2)-N,N'-Priso)}(2)] towards a range of small molecules was examined and this gave rise to diamagnetic complexes [{Ni(Priso)(μ-CO)}(2)] and [{Ni(Priso)(μ-N(3))}(2)]. Taken as a whole, this study highlights similarities between bulky guanidinate ligands and the β-diketiminate ligand class, but shows the former to have greater coordinative flexibility.     

Peroxide solvation by a toroidal lithium inverse crown ether complex assembled by multidentate polyimido sulfonates

In this communication we present the synthesis of the inverse crown ether complex [Li(2)O(2)·Li(4){CH(2)(N(Me)CH(2)S(NtBu)(2))(2)}(2)] (1) which is able to accommodate peroxide in a torus of lithium ions.     

Synthesis and structures of a 3-sila-beta-diketiminatomagnesium bromide, ketenimide and triflate

The crystalline compounds [Mg(Br)(L)(thf)].0.5Et2O [L = {N(R)C(C6H3Me2-2,6)}2SiR, R = SiMe3] (1), [Mg(L){N=C=C(C(Me)=CH)2CH2}(D)2] [D = NCC6H3Me2-2,6 (2), thf (3)] and [{Mg(L)}2{mu-OSO(CF3)O-[mu}2] (4) were prepared from (a) Si(Br)(R){C(C6H3Me2-2,6)=NR}2 and Mg for (1), (b) [Mg(SiR3)2(thf)2] and 2,6-Me2C6H3CN (5 mol for (2), 3 mol for (3)), and (c) (2) + Me3SiOS(O)2CF3 for (4); a coproduct from (c) is believed to have been the trimethylsilyl ketenimide Me3SiN=C=C{C(Me)=CH}2CH2 (5).     

Solution studies of dinuclear polyamine-linked platinum-based antitumour complexes

The aquation profiles of two novel dinuclear polyamine-linked, platinum-based antitumour complexes [{trans-PtCl((15)NH(3))(2)}(2){μ-((15)NH(2)(CH(2))(6)(15)NH(2)(CH(2))(6)(15)NH(2))}](3+) (BBR3007, 1,1/t,t-6,6, 1) and [{trans-PtCl((15)NH(3))(2)}(2){μ-((15)NH(2)(CH(2))(6)(15)NH(2)(CH(2))(2)(15)NH(2)(CH(2))(6)(15)NH(2))}](4+) (BBR3610, 1,1/t,t-6,2,6, 1') have been probed using 2D [(1)H, (15)N] HSQC NMR spectroscopy. Reported herein are the rate constants for the hydrolysis of 1 and 1', as well as the acid dissociation constants of the coordinated aqua ligands in their aquated derivatives. The aquation and anation rate constants for the single step aquation model in 15 mM NaClO(4) (pH 5.4) at 298 K are, for 1, k(1) = 7.2 ± 0.1 ×10(-5) s(-1), k(-1) = 0.096 ± 0.002 M(-1) s(-1) and, for 1', k(1) = 4.0 ± 0.2 × 10(-5) s(-1), k(-1) = 1.4 ± 0.1 M(-1) s(-1). The effect of the linker backbone (Pt(tetra(m)mine vs. polyamine) was evaluated by comparison with previous data for the trinuclear complex [{trans-PtCl(NH(3))(2)}(2)(μ-trans-Pt(NH(3))(2){NH(2)(CH(2))(6)NH(2)}(2))](4+) (1,0,1/t,t,t or BBR3464). The pK(1) for 1,0,1/t,t,t (3.44) is closest to that of 1 (3.12), while the pronounced difference for 1' (4.54), means that 1' is the least aquated of the three complexes at equilibrium. pK(a) values of 5.92 were calculated for the aquated forms of both 1 and 1', which are 0.3 pK units higher than for either 1,0,1/t,t,t, or the dinuclear 1,1/t,t. The higher pK(a) values for both polyamine-linked compounds may be attributed to the formation of macrochelates between the central NH(2) groups and the {PtN(3)O} coordination sphere of the aquated species.     

Nucleophilic attack toward group 4 metal complexes bearing reactive 1-Aza-1,3-butadienyl and imido moieties

Unique (1-aza-2-butenyl)titanium complexes bearing a phosphonium ylide moiety [Ti=NTbt{C(Me)(PR3)CH=C(Me)N(Mes)}Cl] (3-5, Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = 2,4,6-trimethylphenyl) were formed by the nucleophilic attack of PMe3, P(n-Bu)3, and 1,2-bis(dimethylphosphino)ethane (dmpe) toward the corresponding (1-aza-1,3-butadienyl)titanium complex, [Ti=NTbt{C(Me)CHC(Me)N(Mes)}(mu-Cl)2Li(tmeda)] (2a). The reaction of a lithium beta-diketiminate, [Li{N(Tbt)C(Me)CHC(Me)N(Mes)}] (1) with [TiIICl2(dmpe)2] also resulted in the formation of the same complex 5. Density functional theory calculation indicated that the negative charge of the model molecule of 3 was slightly delocalized to the C3N plane. In addition, the calculation of the model molecule of 2a suggested the electrophilicity of 2a at the carbon atom connecting to the titanium atom. Interestingly, the reaction of zirconium and hafnium analogues (2b and 2c) with PMe3 and dmpe did not proceed. In contrast to the cases of phosphine reagents, pyridine which was found to undergo the nucleophilic attack toward the titanium center of 2a gave the pyridine-coordinated titanium-imide [Ti=NTbt{C(Me)CHC(Me)N(Mes)}Cl(py)] (7).     

Secondary Amine Stabilized Aluminum Hydrides Derived from N,N'-Di-tert-butylethylenediamines

The metalation of substituted N,N'-di-tert-butylethylenediamines by various aluminum hydride sources has been investigated. HN(t-Bu)CH(t-Bu)CH(2)N(H)(t-Bu) forms a dimeric lithium chelated adduct of LiAlH(4), [{[HN(t-Bu)CH(t-Bu)CH(2)N(H)(t-Bu)]Li(&mgr;-H)(2)AlH(2)}(2)], 4, which thermally decomposes to yield the tetrameric lithium diamidoaluminum hydride [{Li[N(t-Bu)CH(t-Bu)CH(2)N(t-Bu)]AlH(2)}(4)], 5. The same diamine reacts with AlH(3).NMe(3) or AlH(3) diethyl etherate to give the secondary amine stabilized amidoaluminum hydride species [{HN(t-Bu)CH(t-Bu)CH(2)N(t-Bu)}AlH(2)], 2. Similarly, the same aluminum hydride sources react with the diamine rac-HN(t-Bu)CH(Me)CH(Me)N(H)(t-Bu) to yield [{rac-HN(t-Bu)CH(Me)CH(Me)N(t-Bu)}AlH(2)], 3. Compounds 2 and 3 are stable with respect to elimination of hydrogen to form diamidoaluminum hydrides, but can be converted to the alane rich species, [H(2)Al{N(t-Bu)CH(t-Bu)CH(2)N(t-Bu)}AlH(2)],6, and [H(2)Al{rac-N(t-Bu)CH(Me)CH(Me)N(t-Bu)}AlH(2)], 7, by reaction with AlH(3).NMe(3) under special conditions. The varying reactivity of the three aluminum hydride sources in these reactions has enabled mechanistic information to be gathered, and the effect of the different steric requirements in the diamines on the stability of the complexes is discussed. Crystals of 3are monoclinic, space group P2(1)/n (No. 14), with a = 8.910(4), b = 14.809(1), and c = 12.239(6) ?, beta = 109.76(2) degrees, V = 1520(1) ?(3), and Z = 4. Crystals of 4 are orthorhombic, space group Pbca (No. 61), with a = 15.906(9), b = 24.651(7), and c = 9.933(7) ?, V = 3895(3) ?(3), and Z = 4. Crystals of 6 are monoclinic, space group P2(1)/c (No. 14), with a = 8.392(1), b = 17.513(2), and c = 12.959(1) ?, beta = 107.098(8) degrees, V = 1820.4(3) ?(3), and Z = 4.     

The preparation and characterisation of hetero- and homobimetallic complexes containing bridging naphthalene-1,8-dithiolato ligands

Homo- and heterobimetallic complexes of the form [(PPh(3))(2)(mu(2)-1,8-S(2)-nap){ML(n)}] (in which (1,8-S(2)-nap)=naphtho-1,8-dithiolate and {ML(n)}={PtCl(2)} (1), {PtClMe} (2), {PtClPh} (3), {PtMe(2)} (4), {PtIMe(3)} (5) and {Mo(CO)(4)} (6)) were obtained by the addition of [PtCl(2)(NCPh)(2)], [PtClMe(cod)] (cod=1,5-cyclooctadiene), [PtClPh(cod)], [PtMe(2)(cod)], [{PtIMe(3)}(4)] and [Mo(CO)(4)(nbd)] (nbd=norbornadiene), respectively, to [Pt(PPh(3))(2)(1,8-S(2)-nap)]. Synthesis of cationic complexes was achieved by the addition of one or two equivalents of a halide abstractor, Ag[BF(4)] or Ag[ClO(4)], to [{Pt(mu-Cl)(mu-eta(2):eta(1)-C(3)H(5))}(4)], [{Pd(mu-Cl)(eta(3)-C(3)H(5))}(2)], [{IrCl(mu-Cl)(eta(5)-C(5)Me(5))}(2)] (in which C(5)Me(5)=Cp*=1,2,3,4,5-pentamethylcyclopentadienyl), [{RhCl(mu-Cl)(eta(5)-C(5)Me(5))}(2)], [PtCl(2)(PMe(2)Ph)(2)] and [{Rh(mu-Cl)(cod)}(2)] to give the appropriate coordinatively unsaturated species that, upon treatment with [(PPh(3))(2)Pt(1,8-S(2)-nap)], gave complexes of the form [(PPh(3))(2)(mu(2)-1,8-S(2)-nap){ML(n)}][X] (in which {ML(n)}[X]={Pt(eta(3)-C(3)H(5))}[ClO(4)] (7), {Pd(eta(3)-C(3)H(5))}[ClO(4)] (8), {IrCl(eta(5)-C(5)Me(5))}[ClO(4)] (9), {RhCl(eta(5)-C(5)Me(5))}[BF(4)] (10), {Pt(PMe(2)Ph)(2)}[ClO(4)](2) (11), {Rh(cod)}[ClO(4)] (12); the carbonyl complex {Rh(CO)(2)}[ClO(4)] (13) was formed by bubbling gaseous CO through a solution of 12. In all cases the naphtho-1,8-dithiolate ligand acts as a bridge between two metal centres to give a four-membered PtMS(2) ring (M=transition metal). All compounds were characterised spectroscopically. The X-ray structures of 5, 6, 7, 8, 10 and 12 reveal a binuclear PtMS(2) core with PtM distances ranging from 2.9630(8)-3.438(1) A for 8 and 5, respectively. The napS(2) mean plane is tilted with respect to the PtP(2)S(2) coordination plane, with dihedral angles in the range 49.7-76.1 degrees and the degree of tilting being related to the PtM distance and the coordination number of M. The sum of the Pt(1)coordination plane/napS(2) angle, a, and the Pt(1)coordination plane/M(2)coordination plane angle, b, a+b, is close to 120 degrees in nearly all cases. This suggests that electronic effects play a significant role in these binuclear systems.