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.     

Reactivity of niobium(v) and tantalum(v) halides with carbonyl compounds: synthesis of simple coordination adducts, C-H bond activation, C=O protonation, and halide transfer

The metal halides of Group 5 MX(5) (M = Nb, Ta; X = F, Cl, Br) react with ketones and acetylacetones affording the octahedral complexes [MX(5)(ketone)] () and [TaX(4){kappa(2)(O)-OC(Me)C(R)C(Me)O}] (R = H, Me, ), respectively. The adducts [MX(5)(acetone)] are still reactive towards acetone, acetophenone or benzophenone, giving the aldolate species [MX(4){kappa(2)(O)-OC(Me)CH(2)C(R)(R')O}] (). The syntheses of (M = Ta, X = F, R = R' = Ph) and (M = Ta, X = Cl, R = Me, R' = Ph) take place with concomitant formation of [(Ph(2)CO)(2)-H][TaF(6)], and [(MePhCO)(2)-H][TaCl(6)], respectively. The compounds [acacH(2)][TaF(6)], and [TaF{OC(Me)C(Me)C(Me)O}(3)][TaF(6)], have been isolated as by-products in the reactions of TaF(5) with acacH and 3-methyl-2,4-pentanedione, respectively. The molecular structures of, and have been ascertained by single crystal X-ray diffraction studies.     

Ruthenium complexes with tridentate PNX (X = O, S) donor ligands

The ligands, PhPNXMe (1), PhPNXPh (2), and PhPNSMe (3), (PhPNX = 2-Ph2P-C6H4CH[double bond, length as m-dash]NC6H4X-2; X = O, S) have been prepared. A range of new ruthenium complexes were synthesised using these and related ligands, namely: [{RuCl(PhPNO)}2Cl] (4), [Ru(PhPNO)2] (5), [RuCl(PhPNXR)(PPh3)]BPh4 [X = O, R = Me (6); X = O, R = Ph (7); X = S, R = Me (8)], [{RuCl(PhPNX'R)}2Cl]X [X' = O, R = Me, X = Cl(-) (9); X' = S, R = Me, X = BPh4(-) or PF6(-) (10)], and [RuCl(PhPNO-eta 6C6H5)]BPh4 (11). The catalytic activity of these complexes with respect to the hydrosilyation of acetophenone and the hydrogenation of styrene has been investigated, giving an insight into the requirements for an active complex in these reactions.     

The first coordination complexes of selenones: a structural comparison with complexes of sulfones

Reactivity of the two classes of very weak donors R(2)XO(2) (X = S, R = Me (1) and Ph (2); X = Se, R = Me (3) and Ph (4)) have been studied. Coordination properties of sulfones and selenones in solution and in the gas phase have been compared for the first time using a model bidentate metal complex, [Rh(2)(O(2)CCF(3))(4)]. Two coordination modes, bridging mu(2)-O,O' and terminal eta(1)-O, have been detected. These types of binding were realized in two series of sulfone and selenone metal complexes, polymeric mono-adducts [Rh(2)(O(2)CCF(3))(4).(R(2)XO(2))]( infinity ) (X = S, R = Me (1a); R = Ph (2a); X = Se, R = Ph (4a)) and discrete bis-adducts [Rh(2)(O(2)CCF(3))(4).(R(2)XO(2))(2)] (X = S, R = Ph (2b); X = Se, R = Me (3b)). The compositions and structures of new compounds have been confirmed by NMR and IR spectroscopy, chemical analyses, and X-ray diffraction studies. Compounds 3b and 4a are the first crystallographically characterized metal complexes having selenone ligands coordinated to the metal centers. Preparation and X-ray study of analogous metal complexes of sulfone and selenone ligands allow, for the first time, tracking the structural changes induced by metal coordination. In addition, the X-ray structure of dimethyl selenone, Me(2)SeO(2) (3), an analogue of Me(2)SO(2), has been determined. Geometries of coordinated sulfone and selenones ligands have been compared with those of the corresponding "free" molecules.     

Access to new Janus head ligands: linking sulfur diimides and phosphanes for hemilabile tripodal scorpionates

Reactions of lithium dialkyl/phenyl phosphanylmethylides, RR'PCH(X)Li (R, R' = Me, Et, Ph and R = Me, R' = Ph; X = H or Me), with sulfur diimides S(NR')2 (R' = (t)Bu or SiMe3) in an equimolar ratio yielded Janus head complexes with the structural motif [Li{RR'PCH(X)S(NR')2}]2 (R' = (t)Bu, SiMe3). The basic core of these dimeric complexes is composed of a (LiN)(2) four-membered ring containing two four-coordinated lithium atoms. A lithium complex of the new Janus head ligand with another structural motif [TMEDA·Li{Ph(2)PCH(2)S(NSiMe3)2}] (6) could be isolated from the reaction of [Ph2PCH2Li·TMEDA] with S(NSiMe3)2. Two monomeric complexes [Mg{Me2PCH2S(NR')2}2] (7, 8) were synthesised by a straightforward reaction of [Li{Me2PCH2S(NR')2}2] with MgCl2 in pentane. The magnesium atom is chelated by one phosphorus atom and two nitrogen atoms of each unit of the hemilabile ligand in a tripodal manner, leading to octahedral geometry around the magnesium cation. A complete analysis of [Ph2PCH2(SNSiMe3)(HNSiMe3)] (9) is also described in which one nitrogen atom of the imido moiety is protonated.     

PtII-mediated 1,3-dipolar cycloaddition of oxazoline N-oxides to nitriles as a key step to dihydrooxazolo-1,2,4-oxadiazoles

A novel type of heterocycle, viz., 2,3a-disubstituted 5,6-dihydro-3aH-[1,3]oxazolo[3,2-b][1,2,4]oxadiazoles, was generated by an intermolecular PtII-mediated 1,3-dipolar cycloaddition (1,3-DCA) between the oxazoline N-oxide C(Me)2CH2OC(R)=N+(O-) (R = Me, Et) and coordinated nitriles in the complexes trans/cis-[PtCl2(R'CN)2] [R' = Me, Et, CH2Ph, Ph, N(C5H10)]. The reaction is unknown for free RCN and oxazoline N-oxides, but under PtII-mediated conditions, it proceeds smoothly (CH2Cl2, 20-25 degrees C, 18-20 h) and gives pure complexes [PtCl2{N=C(R')ONC(R)OCH2CMe2}2] [R/R' = Me/Me, 1; Me/Et, 2; Me/CH2Ph, 3; Me/Ph, 4; Me/N(C5H10), 5; Et/Me, 6; Et/Et, 7; Et/CH2Ph, 8; Et/Ph, 9; Et/N(C5H10), 10] in 42-84% yields after column chromatography. Compounds 1-10 were characterized by elemental analyses (C, H, N), FAB+-MS, IR, and 1H and 13C{1H} NMR spectroscopies, and X-ray diffraction (for 1, 2, 5, and 9). With the exception of benzonitrile complexes, 1,3-DCA of oxazoline N-oxides to the PtII-ligated nitriles occurred diastereoselectively and afforded mixtures of enantiomers. Depending on the substituents on nitriles, asymmetric atoms in both of the formed heterocyclic ligands have the same (SS/RR) or different (SR/RS) configurations. The heterocyclic ligands were liberated from 1-4 and 6-9 by treatment with excess ethane-1,2-diamine (en) in CH2Cl2 for 1 day at 20-25 degrees C (for R' = Me, Et, CH2Ph) and at 50 degrees C (for R' = Ph) to achieve the free organic species and the well-known [Pt(en)2](Cl)2; the products were separated, and 2,3a-disubstituted 5,6-dihydro-3aH-[1,3]oxazolo[3,2-b][1,2,4]oxadiazoles (11-18) were characterized by ESI+-MS and 1H and 13C{1H} NMR spectroscopies.     

Group 13 β-ketoiminate compounds: gallium hydride derivatives as molecular precursors to thin films of Ga2O3

Bis(β-ketoimine) ligands, [R{N(H)C(Me)-CHC(Me)═O}(2)] (L(1)H(2), R = (CH(2))(2); L(2)H(2), R = (CH(2))(3)), linked by ethylene (L(1)) and propylene (L(2)) bridges have been used to form aluminum, gallium, and indium chloride complexes [Al(L(1))Cl] (3), [Ga(L(n))Cl] (4, n = 1; 6, n = 2) and [In(L(n))Cl] (5, n = 1; 7, n = 2). Ligand L(1) has also been used to form a gallium hydride derivative [Ga(L(1))H] (8), but indium analogues could not be made. β-ketoimine ligands, [Me(2)N(CH(2))(3)N(H)C(R')-CHC(R')═O] (L(3)H, R' = Me; L(4)H, R' = Ph), with a donor-functionalized Lewis base have also been synthesized and used to form gallium and indium alkyl complexes, [Ga(L(3))Me(2)] (9) and [In(L(3))Me(2)] (10), which were isolated as oils. The related gallium hydride complexes, [Ga(L(n))H(2)] (11, n = 3; 12, n = 4), were also prepared, but again no indium hydride species could be made. The complexes were characterized mainly by NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction. The β-ketoiminate gallium hydride compounds (8 and 11) have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted (AA)CVD with toluene as the solvent. The quality of the films varied according to the precursor used, with the complex [Ga(L(1))H] (8) giving by far the best quality films. Although the films were amorphous as deposited, they could be annealed at 1000 °C to form crystalline Ga(2)O(3). The films were analyzed by powder XRD, SEM, and EDX.     

Stereospecific synthesis of polysubstituted E-olefins by reaction of acyclic nitrones with free and platinum(II) coordinated organonitriles

Free nitriles NCCH2R (1a R = CO2Me, 1b R = SO2Ph, and 1c R = COPh) with an acidic alpha-methylene react with acyclic nitrones -O+N(Me)=C(H)R' (2a R' = 4-MeC6H4 and 2b R' = 2,4,6-Me3C6H2), in refluxing CH2Cl2, to afford stereoselectively the E-olefins (NC)(R)C=C(H)R' (3a-3c and 3a'-3c'), whereas, when coordinated at the platinum(II) trans-[PtCl2(NCCH2R)2] complexes (4a R = CO2Me and 4b R = Cl), they undergo cycloaddition to give the (oxadiazoline)-PtII complexes trans-[PtCl2{N=C(CH2R)ON(Me)C(H)R'}2] (R = CO2Me, Cl and R' = 4-MeC6H4, 2,4,6-Me3C6H2) (5a-5d). Upon heating in CH2Cl2, 5a affords the corresponding alkene 3a. The reactions are greatly accelerated when carried out under focused microwave irradiation, particularly in the solid phase (SiO2), without solvent, a substantial increase of the yields being also observed. The compounds were characterized by IR and 1H, 13C, and 195Pt NMR spectroscopies, FAB+-MS, elemental analyses and, in the cases of the alkene (NC)(CO2Me)C=C(H)(4-MeC6H4) 3a and of the oxadiazoline complex trans-[PtCl2{N=C(CH2Cl)ON(Me)C(H)(4-C6H4Me)}2] 5c, also by X-ray diffraction analyses.     

Synthesis,structure, and reactivity of some sterically hindered (Silylamino)phosphines

A series of new (silylamino)phosphines that contain sterically bulky silyl groups on nitrogen were prepared by deprotonation/substitution reactions of the hindered disilylamines t-BuR(2)Si(Me(3)Si)NH (1, R = Me; 2, R = Ph) and (Et(3)Si)(2)NH (3). Sequential treatment of the N-lithio derivatives of 1-3 with PCl(3) or PhPCl(2) and MeLi gave the corresponding (silylamino)phosphines t-BuR(2)Si(Me(3)Si)NP(R')Me (5, R = Me, R' = Ph; 6, R = Ph, R' = Me) and (Et(3)Si)(2)NP(R)Me (11, R = Me; 12, R = Ph) in high yields. Two of the P-chloro intermediates t-BuR(2)Si(Me(3)Si)NP(Ph)Cl (7, R = Ph; 9, R = Me) were also isolated and fully characterized. Hydrolysis of 7 afforded the crystalline PH-substituted aminophosphine oxide t-BuPh(2)SiN(H)P(Ph)(=O)H (10). Thermal decomposition of 7 occurred with elimination of Me(3)SiCl and formation of a novel P(2)N(2) four-membered ring system (36) that contains both P(III) and P(V) centers. Reactions of the N-lithio derivatives of amines 1 and 2 with phosphorus trihalides afforded the thermally stable -PF(2) derivatives t-BuR(2)Si(Me(3)Si)NPF(2) (13, R = Me; 14, R = Ph) and the unstable -PCl(2) analogue 17 (R = Ph). Reduction (using LiAlH(4)) of the SiPh-substituted dihalophosphines 14 and 17 gave the unstable parent phosphine t-BuPh(2)Si(Me(3)Si)NPH(2) (15). The P-organo-substituted (silylamino)phosphines underwent oxidative bromination to afford high yields of the corresponding N-silyl-P-bromophosphoranimines t-BuR(2)SiN=P(R')(Me)Br (18, R = R' = Me; 19, R = Me, R' = Ph; 20, R = Ph, R' = Me) and Et(3)SiN=P(R)(Me)Br (23, R = Me; 24, R = Ph). Subsequent treatment of these reactive PBr compounds with lithium trifluoroethoxide or phenoxide produced the corresponding PO derivatives t-BuR(2)SiN=P(R')(Me)OR' ' (25 and 26, R' ' = CH(2)CF(3); 28-30, R' ' = Ph) and Et(3)SiN=P(R)(Me)OR' (31 and 33, R' = CH(2)CF(3); 32 and 34, R = Ph), respectively. Many of the new compounds containing the bulky tert-butyldiphenylsilyl group, t-BuPh(2)Si, were solids that gave crystals suitable for X-ray diffraction studies. Consequently, the crystal structures of three (silylamino)phosphines (6, 7, and 14), one (silylamino)phosphine oxide (10), one N-silylphosphoranimine (30), and the cyclic compound 36 were determined. Among the (silylamino)phosphines, the P-N bond distances [6, N-PMe(2), 1.725(3) A; 7, N-P(Ph)Cl, 1.68(1) A, 14, N-PF(2), 1.652(4) A] decreased significantly as the electron-withdrawing nature of the phosphorus substituents increased. The N-silylphosphoranimine t-BuPh(2)SiN=PMe(2)OPh (30), which is a model system for poly(phosphazene) precursors, had a much shorter P=N distance of 1.512(6) A and a wide Si-N-P bond angle of 166.4(3) degrees. A similar P=N bond distance [1.514(7) A] and Si-N-P angle [169.9(6) degrees ] were observed for the exocyclic P=N-Si linkage in the ring compound 36, while the phosphine oxide 10 had P-N and P=O distances of 1.637(4) and 1.496(3) A, respectively, and a Si-N-P angle of 134.3(2) degrees.     

Reactions of amides with organoaluminum compounds: factors affecting the coordination mode of aluminum amidates

Factors affecting the coordination mode of an amidato group on aluminum will be presented. The reaction of N-tert-butylalkylacetamide ((t)BuNHCR([double bond]O)) with 1.1 molar equiv of Me(3)Al in refluxing hexane affords a pentacoordinated, dimeric compound [Me(2)Al[eta(2)-(t)BuNC(R)(mu(2)-O)]](2) (3, R = p-(t)Bu-C(6)H(4); 4, R = 2,6-F,F-C(6)H(3); 5, R = Me; 6, R = CF(3); 7, R = p-F(3)C-C(6)H(4)). However, in the presence of 2.2 molar equiv of Me(3)Al, N-tert-butyl-4-tert-butylbenzamide ((t)BuNHC(p-(t)Bu-C(6)H(4))([double bond]O in refluxing hexane gives [Me(2)Al[eta(2)-(t)BuNC(p-(t)Bu-C(6)H(4))(mu(2)-O)]AlMe(3)], 8. In contrast, the reaction of R'NHCR' '([double bond]O) with 1 molar equiv of R(3)Al at room temperature produces tetracoordinated, dimeric, eight-membered ring aluminum compounds [R(2)Al[mu,eta(2)-R'NC(R' ')O]](2) (9, R = Me, R' = 2,6-(i)Pr, (i)()Pr-C(6)H(3), R' ' = Ph; 10, R = Me, R' = (i)Bu, R' ' = Ph; 11, R = Et, R' = Bn, R' ' = Ph; 12, R = Me, R' = Ph, R' ' = CF(3); 13, R = Me, R' = Bn, R' ' = CF(3)). On the other hand, 4'-chlorobenzanilide ((p-Cl-C(6)H(4))NHCPh([double bond]O)) reacts with R(3)Al to produce trimeric, twelve-membered ring aluminum compounds [R(2)Al[mu, eta(2)-(p-Cl-C(6)H(4))NC(Ph)O]](3) (14, R = Me; 15, R = Et). Furthermore, the reaction of 2'-methoxybenzanilide with 1 molar equiv of Me(3)Al in hexane yields a dinuclear aluminum complex [Me(2)Al(o-OMe-Ph)NC(Ph)(O)AlMe(3)], 16.     

Reactions of phosphine oxides with bromophosphoranimines; synthesis and unusual rearrangements of O-donor stabilized phosphoranimine cations

Reaction of phosphine oxides R(3)P═O [R = Me (1a), Et (1c), (i)Pr (1d) and Ph (1e)], with the bromophosphoranimines BrPR'R'P═NSiMe(3) [R' = R' = Me (2a); R' = Me, R' = Ph (2b); R' = R' = OCH(2)CF(3) (2c)] in the presence or absence of AgOTf (OTf = CF(3)SO(3)) resulted in a rearrangement reaction to give the salts [R(3)P═N═PR'R'O-SiMe(3)]X (X = Br or OTf) ([4]X). Reaction of phosphine oxide 1a with the phosphoranimine BrPMe(2)═NSiPh(3) (5) with a sterically encumbered silyl group also resulted in the analogous rearranged product [Me(3)P═N═PMe(2)O-SiPh(3)]X ([8]X) but at a significantly slower rate. In contrast, the direct reaction of the bulky tert-butyl substituted phosphine oxide, (t)Bu(3)P═O (1b) with 2a or 2c in the presence of AgOTf yielded the phosphine oxide-stabilized phosphoranimine cations [(t)Bu(3)P═O·PR'(2)═NSiMe(3)](+) ([3](+), R' = Me (d), OCH(2)CF(3) (e)). A mechanism is proposed for the unexpected formation of [4](+) in which the formation of the donor-stabilized adduct [3](+) occurs as the first step.     

Synthesis and coordination properties of new bis(phosphinomethyl)pyridine N,P,P'-trioxides

In a search for more hydrocarbon solvent soluble derivatives of the parent ligand, 2,6-[Ph(2)P(O)CH(2)](2)C(5)H(3)NO (1a), a series of new ligands, 2,6-[R(2)P(O)CH(2)](2)C(5)H(3)NO [R = Bz (1b); Tol (1c); Et (1d); Pr (1e); Bu (1f); Pn (1g); Hx (1h); Hp (1i); and Oct (1j)] and 2,6-[RR'P(O)CH(2)](2)C(5)H(3)NO [R = Ph, R' = Bz (2a); R = Ph, R' = Me (2b); R = Ph, R' = Hx (2c); R = Ph, R' = Oct (2d)], have been prepared by either Arbusov or Grignard substitutions on 2,6-bis(chloromethyl)pyridine followed by N-oxidation. The new ligands have been characterized by spectroscopic methods, and their coordination chemistry with selected lanthanide ions has been surveyed. Several 1:1 and 2:1 ligand/metal complexes have been isolated, and single-crystal X-ray diffraction analyses for Nd(2a)(NO(3))(3), Er(2a)(NO(3))(3), Yb(1d)(NO(3))(3), and [Nd(1c)(2)](NO(3))(3) are described. The new structural data are discussed in relation to the structures of complexes formed by 1a.     

Synthesis,structure, and reactivity of some N-phosphorylphosphoranimines

A large series of new N-phosphorylphosphoranimines that bear potentially reactive functional groups on both phosphorus centers were prepared by silicon-nitrogen bond cleavage reactions of N-silylphosphoranimines. Thus, treatment of the N-silylphosphoranimines, Me(3)SiN=P(Me)(R)X (R = Me, Ph; X = OCH(2)CF(3) and R = Me, X = OPh), with phosphoryl chlorides, RP(=O)Cl(2) (R' = Cl, Me, Ph), readily afforded the corresponding N-phosphoryl derivatives, R'P(=O)(Cl)-N=P(Me)(R)X, in high yields. Subsequent reaction with 1 or 2 equiv of the silylamine, Me(3)SiNMe(2), resulted in ligand exchange at the phosphoryl (P=O) group to give the P-dimethylamino analogues, R'P(=O)(NMe(2))N=P(Me)(R)X (R' = Cl, NMe(2), Me, Ph; R = Me, Ph; X = OCH(2)CF(3), OPh). These new N-phosphorylphosphoranimines (and one thiophosphoryl analogue) were obtained as thermally stable, distillable liquids and were characterized by NMR ((1)H, (13)C, and (31)P) spectroscopy and elemental analysis. One member of the series, Cl(2)P(=O)N=P(Me)(Ph)OCH(2)CF(3) (4), was also studied by single-crystal X-ray diffraction which revealed that the formal P(O)-N single bond [1.55(1) A] is shorter than the formal N=PR(2)X double bond [1.60(1) A]. Such structural features are compared to those of similar compounds and discussed in relationship to the unexpected thermolysis pathways observed for these N-phosphorylphosphoranimines, none of which produced poly(phosphazenes).     

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.     

Chromium(III) stars and butterflies: synthesis, structural and magnetic studies of tetrametallic clusters

We report the synthesis, structures and magnetic properties of a series of chromium(III) metal-centered triangle (or "star") clusters, [Cr(4){RC(CH(2)O)(3)}(2)(4,4'-R'(2)-bipy)(3)Cl(6)] [R = Et, R' = H (2); R = HOCH(2), R' = H (3); R = Et, R' = (t)Bu (4)], prepared by two-step solvothermal reactions starting from [CrCl(3)(thf)(3)]. The product of the first stage of this reaction is the salt [Cr(bipy)(2)Cl(2)](2)[Cr(2)Cl(8)(MeCN)(2)] (1). In the absence of the diimine, a different family of tetrametallics is isolated: the butterfly complexes [Cr(4){EtC(CH(2)O)(3)}(2){NH(C(R)NH)(2)}(2)Cl(6)] (R = Me (5), Et (6), Ph (7)] where the chelating N-acetimidoylacetamidine NH(C(R)=NH)(2) ligands are formed in situ via condensation of the nitrile solvents (RCN) under solvothermal conditions. Magnetic measurements show the chromium stars to have an isolated S = 3 ground state, arising from antiferromagnetic coupling between the central and peripheral metal ions, analogous to the well-known Fe(III) stars. Bulk antiferromagnetic ordering is observed at 0.6 K. The butterfly complexes have a singlet ground state, with a low-lying S = 1 first excited state, due to dominant wing-body antiferromagnetic coupling.     

The first acetimine gold(I) and gold(III) complexes and the first acetonine complexes

Ketimino(phosphino)gold(I) complexes of the type [Au[NR=C(Me)R']L]X (X = ClO4, R = H, L = PPh3, R'=Me (la), Et (2a); L=PAr3 (Ar=C6H4OMe-4), R'=Me (1b), Et (2b); L=PPh3, R=R'=Me (3); X= CF3SO3 (OTf), L=PPh3, R=R'=Me (3'); R=Ar, R'=Me (4)) have been prepared from [Au(acac)L] (acac = acetyl acetonate) and ammonium salts [RNH3]X dissolved in the appropriate ketone MeC(O)R'. Complexes [Au(NH=CMe2)2]X (X = C1O4 (6), OTf (6')) were obtained from solutions of [Au(NH3)2]X in acetone. The reaction of 6 with PPN[AuCl2] or with PhICl2 gave [AuCl(NH=CMe2)] (7) or [AuCI2(NH=CMe2)2]ClO4 (8), respectively. Complex 7 was oxidized with PhICl2 to give [AuCl3(NH=CMe2)] (9). The reaction of [AuCl(tht)] (tht = tetrahydrothiophene), NaClO4, and ammonia in acetone gave [Au(acetonine)2]ClO4 (10) (acetonine = 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine) which reacted with PPh3 or with PPN[AuCl2] to give [Au(PPh3)(acetonine)]ClO4 (11) or [AuCl(acetonine)] (12), respectively. Complex 11 reacts with [Au(PPh3)(Me2CO)]ClO4 to give [(AuPPh3)2(mu-acetonine)](ClO4)2 (13). The reaction of AgClO4 with acetonine gave [Ag(acetonine)(OClO3)] (14). The crystal structures of [Au(NH2Ar)(PPh3)]OTf (5), 6' and 10 have been determined.     

Synthesis and reactivity of Ir(I) and Ir(III) complexes with MeNH2, Me2C=NR (R = H, Me), C,N-C6H4{C(Me)=N(Me)}-2, and N,N'-RN=C(Me)CH2C(Me2)NHR (R = H, Me) ligands

Complexes [Ir(Cp*)Cl(n)(NH2Me)(3-n)]X(m) (n = 2, m = 0 (1), n = 1, m = 1, X = Cl (2a), n = 0, m = 2, X = OTf (3)) are obtained by reacting [Ir(Cp*)Cl(mu-Cl)]2 with MeNH2 (1:2 or 1:8) or with [Ag(NH2Me)2]OTf (1:4), respectively. Complex 2b (n = 1, m = 1, X = ClO 4) is obtained from 2a and NaClO4 x H2O. The reaction of 3 with MeC(O)Ph at 80 degrees C gives [Ir(Cp*){C,N-C6H4{C(Me)=N(Me)}-2}(NH2Me)]OTf (4), which in turn reacts with RNC to give [Ir(Cp*){C,N-C6H4{C(Me)=N(Me)}-2}(CNR)]OTf (R = (t)Bu (5), Xy (6)). [Ir(mu-Cl)(COD)]2 reacts with [Ag{N(R)=CMe2}2]X (1:2) to give [Ir{N(R)=CMe2}2(COD)]X (R = H, X = ClO4 (7); R = Me, X = OTf (8)). Complexes [Ir(CO)2(NH=CMe2)2]ClO4 (9) and [IrCl{N(R)=CMe2}(COD)] (R = H (10), Me (11)) are obtained from the appropriate [Ir{N(R)=CMe2}2(COD)]X and CO or Me4NCl, respectively. [Ir(Cp*)Cl(mu-Cl)]2 reacts with [Au(NH=CMe2)(PPh3)]ClO4 (1:2) to give [Ir(Cp*)(mu-Cl)(NH=CMe2)]2(ClO4)2 (12) which in turn reacts with PPh 3 or Me4NCl (1:2) to give [Ir(Cp*)Cl(NH=CMe2)(PPh3)]ClO4 (13) or [Ir(Cp*)Cl2(NH=CMe2)] (14), respectively. Complex 14 hydrolyzes in a CH2Cl2/Et2O solution to give [Ir(Cp*)Cl2(NH3)] (15). The reaction of [Ir(Cp*)Cl(mu-Cl)]2 with [Ag(NH=CMe2)2]ClO4 (1:4) gives [Ir(Cp*)(NH=CMe2)3](ClO4)2 (16a), which reacts with PPNCl (PPN = Ph3=P=N=PPh3) under different reaction conditions to give [Ir(Cp*)(NH=CMe2)3]XY (X = Cl, Y = ClO4 (16b); X = Y = Cl (16c)). Equimolar amounts of 14 and 16a react to give [Ir(Cp*)Cl(NH=CMe2)2]ClO4 (17), which in turn reacts with PPNCl to give [Ir(Cp*)Cl(H-imam)]Cl (R-imam = N,N'-N(R)=C(Me)CH2C(Me)2NHR (18a)]. Complexes [Ir(Cp*)Cl(R-imam)]ClO4 (R = H (18b), Me (19)) are obtained from 18a and AgClO4 or by refluxing 2b in acetone for 7 h, respectively. They react with AgClO4 and the appropriate neutral ligand or with [Ag(NH=CMe2)2]ClO4 to give [Ir(Cp*)(R-imam)L](ClO4)2 (R = H, L = (t)BuNC (20), XyNC (21); R = Me, L = MeCN (22)) or [Ir(Cp*)(H-imam)(NH=CMe2)](ClO4)2 (23a), respectively. The later reacts with PPNCl to give [Ir(Cp*)(H-imam)(NH=CMe2)]Cl(ClO4) (23b). The reaction of 22 with XyNC gives [Ir(Cp*)(Me-imam)(CNXy)](ClO4)2 (24). The structures of complexes 15, 16c and 18b have been solved by X-ray diffraction methods.     

Oxygen extrusion from amidate ligands to generate terminal Ta=O units under reducing conditions. How to successfully use amidate ligands in dinitrogen coordination chemistry

A series of mixed Cp* amidate tantalum complexes Cp*Ta(RNC(O)R')X(3) (where R = Me(2)C(6)H(3), (i)Pr, R' = (t)Bu, Ph, X = Cl, Me) have been prepared via salt metathesis and their fundamental reactivities under reducing conditions have been explored. Reaction of the tantalum chloro precursors with potassium graphite under N(2) or Ar leads to the stereoselective formation of the terminal tantalum oxo species, Cp*Ta=O(η(2)-RN=CR')Cl. This represents the formal extrusion of oxygen from the amidate ligand to the reduced tantalum center and is accompanied by the formation of the iminoacyl fragment bound to Ta(v). Amidate dinitrogen complexes, [Cp*TaCl(RNC(O)(t)Bu)](2)(μ-N(2)) (where R = Me(2)C(6)H(3), (i)Pr) were synthesized via salt metathesis from the known [Cp*TaCl(2)](2)(μ-N(2)) precursor, establishing that amidate ligands can support dinitrogen complexes, but not the reduction process often necessary for their synthesis.     

Chemistry of the oxophosphinidene ligand. 2. Reactivity of the anionic complexes [MCp{P(O)R*}(CO)(2)](-) (M = Mo, W; R* = 2,4,6-C(6)H(2)(t)Bu(3)) toward electrophiles based on elements different from carbon

The anionic oxophosphinidene complexes (H-DBU)[MCp{P(O)R*}(CO)(2)] (M = Mo, W; R* = 2,4,6-C(6)H(2)(t)Bu(3); Cp = η(5)-C(5)H(5), DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene) displayed multisite reactivity when faced with different electrophilic reagents. The reactions with the group 14 organochloride compounds ER(4-x)Cl(x) (E = Si, Ge, Sn, Pb) led to either phosphide-like, oxophosphinidene-bridged derivatives [MCp{P(OE')R*}(CO)(2)] (E' = SiMe(3), SiPh(3), GePh(3), GeMe(2)Cl) or to terminal oxophosphinidene complexes [MCp{P(O)R*}(CO)(2)(E')] (E' = SnPh(3), SnPh(2)Cl, PbPh(3); Mo-Pb = 2.8845(4) ? for the MoPb compound). A particular situation was found in the reaction with SnMe(3)Cl, this giving a product existing in both tautomeric forms, with the phosphide-like complex [MCp{P(OSnMe(3))R*}(CO)(2)] prevailing at room temperature and the tautomer [MCp{P(O)R*}(CO)(2)(SnMe(3))] being the unique species present below 203 K in dichloromethane solution. The title anions also showed a multisite behavior when reacting with transition-metal based electrophiles. Thus, the reactions with the complexes [M'Cp(2)Cl(2)] (M' = Ti, Zr) gave phosphide-like derivatives [MCp{P(OM')R*}(CO)(2)] (M = Mo, M' = TiCp(2)Cl, ZrCp(2)Cl; M = W, M' = ZrCp(2)Cl), displaying a bridging κ(1),κ(1)-P,O- oxophosphinidene ligand connecting MCp(CO)(2) and M'Cp(2)Cl metal fragments (W-P = 2.233(1) ?, O-Zr = 2.016(4) ? for the WZr compound]. In contrast, the reactions with the complex [AuCl{P(p-tol)(3)}] gave the metal-metal bonded derivatives trans-[MCp{P(O)R*}(CO)(2){AuP(p-tol)(3)}] (M = Mo, W; Mo-Au = 2.7071(7) ?). From all the above results it was concluded that the terminal oxophosphinidene complexes are preferentially formed under conditions of orbital control, while charge-controlled reactions tend to give derivatives with the electrophilic fragment bound to the oxygen atom of the oxophosphinidene ligand (phosphide-like, oxophosphinidene-bridged derivatives).     

Low-valent group-13 chemistry. Theoretical investigation of the structures and relative stabilities of donor-acceptor complexes R(3)E[bond]E'R' and their isomers R(2)E[bond]E'RR'

The results of quantum chemical calculations at the gradient-corrected density functional theory (DFT) level with the B3LYP functional of the donor-acceptor complexes R(3)E[bond]E'R' and their isomers R(2)E[bond]E'RR', where E, E' = B[bond]Tl and R, R' = H, Cl, or CH(3), are reported. The theoretically predicted energy differences between the donor-acceptor form R(3)E[bond]E'R' and the classical isomer R(2)E[bond]E'RR' and the bond dissociation energies of the E[bond]E' bonds are given. The results are discussed in order to show which factors stabilize the isomers R(3)E[bond]E'R'. There is no simple correlation of the nature of the group-13 elements E, E' and the substituents R, R' with the stability of the complexes. The isomers R(3)E[bond]'R' come stabilized by pi donor groups R', while the substituents R may either be sigma- or pi-bonded groups. Calculations of Cl(3)B[bond]BR' [R' = Cl, cyclopentadienyl (Cp), or Cp*] indicate that the Cp* group has a particularly strong effect on the complex form. The calculations show that the experimentally known complex Cl(3)B[bond]BCp* is the strongest bonded donor-acceptor complex of main-group elements that has been synthesized until now. The theoretically predicted B[bond]B bond energy is D(o) = 50.6 kcal/mol. However, the calculations indicate that it should also be possible to isolate donor-acceptor complexes R(3)E[bond]E'R' where R' is a sigma-bonded bulky substituent. Possible candidates that are suggested for synthetic work are the borane complexes (C(6)F(5))(3)B[bond]E'R' and (t)Bu(3)B[bond]E'R' (E' = Al[bond]Tl) and the alane complexes Cl(3)Al[bond]E'R' (E' = Ga[bond]Tl).