Magnesium(II) complexes of 2,4-N,N'-disubstituted 1,3,5-triazapentadienyl ligands: synthesis and characterization of [N(Dipp)C(NMe2)NC(NMe(2))N(SiMe3)MgBr]2 and [N(R)C(R')NC(R')N(SiMe3)]2Mg (Dipp = 2,6-iPr2-C6H3, R = Ph, SiMe(3); R' = NMe2, 1-piperidino)

Treatment of the appropriate lithium or sodium 2,4-N,N'-disubstituted 1,3,5-triazapentadienate [RNC(R')NC(R')N(SiMe(3))M](2) (R = Ph, 2,6-(i)Pr(2)-C(6)H(3)(Dipp) or SiMe(3); R' = NMe(2) or 1-piperidino; M = Li or Na) with one or half equivalent portion of MgBr(2)(THF)(2) in Et(2)O under mild conditions furnishes in good yield the first structurally characterized molecular magnesium 2,4-N,N'-disubstituted 1,3,5-triazapentadienates [DippNC(NMe(2))NC(NMe(2))N(SiMe(3))MgBr](2) (1), [{RNC(R')NC(R')N(SiMe(3))}(2)Mg] (R = Ph, R' = NMe(2) 2; R = Ph, R' = 1-piperidino 3; R = SiMe(3), R' = 1-piperidino 4). The solid-state structure of 1 is dimeric and those of 2, 3, and 4 are monomeric. The ligand backbone NCNCN in 1 adopts a W-shaped configuration, while in 2, 3 and 4 adopts a U-shaped configuration.     

Gas-phase synthesis and reactivity of binuclear gold hydride cations, (R3PAu)2H+ (R = Me and Ph)

Electrospray ionization of a mixture of the two gold phosphine chlorides, R3PAuCl (R = Ph and Me), silver nitrate and the amino acid N,N-dimethylglycine (DMG) yields a range of gold containing cluster ions including: (R3P)Au(PR'3)+; (R3PAu)(R'3PAu)Cl+ and (R3PAu)(R'3PAu)(DMG-H)+ (where R = R' = Ph; R = R' = Me; R = Me and R' = Ph). Collision induced dissociation (CID) of the (R3PAu)(R'3PAu)(DMG-H)+ precursor ions yielded the hitherto unknown gold hydride dimers (R3PAu)(R'3PAu)H+. The gas-phase chemistry of these dimers was studied using ion-molecule reactions, collision induced dissociation, electronic excitation dissociation (EED) and DFT calculations on the (H3PAu)2H+ model system. A novel phosphine ligand migration was found to occur prior to fragmentation under CID conditions and this was supported by DFT calculations, which revealed a transition state with a bridging phosphine ligand.     

Substituent effects on indium-phosphorus bonding in (4-RC6H4S)3In.PR'3 adducts (R = H, Me, F; R' = Et, Cy, Ph): a spectroscopic, structural, and thermal decomposition study

The tris(arylthiolate)indium(III) complexes (4-RC(6)H(4)S)(3)In [R = H (5), Me (6), F (7)] were prepared from the 2:3 reaction of elemental indium and the corresponding aryl disulfide in methanol. Reaction of 5-7 with 2 equiv of the appropriate triorganylphosphine in benzene or toluene resulted in isolation of the indium-phosphine adduct series (4-RC(6)H(4)S)(3)In.PR'(3) [R = H, R' = Et (5a), Cy (5b), Ph (5c); R = Me, R' = Et (6a), Cy (6b), Ph (6c); R = F, R' = Et (7a), Cy (7b), Ph (7c)]. These compounds were characterized via elemental analysis, FT-IR, FT-Raman, solution (1)H, (13)C{(1)H}, (31)P{(1)H}, and (19)F (7a-c) NMR spectroscopy, and X-ray crystallography (5c, 6a, 6c, and 7a). NMR spectra show retention of the In-P bond in benzene-d(6) solution, with phosphine (31)P{(1)H} signals shifted downfield compared to the uncoordinated ligand. The X-ray structures show monomeric 1:1 adduct complexes in all cases. The In-P bond distance [2.5863(5)-2.6493(12) A] is influenced significantly by the phosphine substituents but is unaffected by the substituted phenylthiolate ligand. Relatively low melting points (88-130 degrees C) are observed for all adducts, while high-temperature thermal decomposition is observed for the indium thiolate reactants 5-7. DSC/TGA and EI-MS data show a two-step thermal decomposition process, involving an initial loss of the phosphine moiety followed by loss of thiolate ligand.     

Synthesis, structures and reactions of lithium complexes of [(o-RCHC6H4)PPh2=NSiMe3]-(R = H, SiMe3) ligands

N-Trimethylsilyl o-methylphenyldiphenylphosphinimine, (o-MeC6H4)PPh2=NSiMe3 (1), was prepared by reaction of Ph2P(Br)=NSiMe3 with o-methylphenyllithium. Treatment of 1 with LiBun and then Me3SiCl afforded (o-Me3SiCH2C6H4)PPh2=NSiMe3 (2). Lithiations of both 1 and 2 with LiBu(n) in the presence of tmen gave crystalline lithium complexes [Li{CH(R)C6H4(PPh(2=NSiMe3)-.tmen](3, R = H; 4, R = SiMe3). From the mother liquor of 4, traces of the tmen-bridged complex [Li{CH(SiMe3)C6H4(PPh2=NSiMe3)-2}]2(mu-tmen) (5) were obtained. Reaction of 2 with LiBun in Et2O yielded complex [Li{CH(SiMe3)C6H4(PPh2=NSiMe3)-2}.OEt2] (6). Reaction of lithiated with Me2SiCl2 in a 2:1 molar ratio afforded dimethylsilyl-bridged compound Me2Si[CH2C6H4(PPh2=NSiMe3)-2]2 (7). Lithiation of 7 with two equivalents of LiBun in Et2O yielded [Li2{(CHC6H4(PPh2=NSiMe3)-2)2SiMe2}.0.5OEt2](8.0.5OEt2). Treatment of 4 with PhCN formed a lithium enamide complex [Li{N(SiMe3)C(Ph)CHC6H4(PPh2=NSiMe3)-2}.tmen] (9). Reaction of two equivalents of 5 with 1,4-dicyanobenzene gave a dilithium complex [{Li(OEt2)2}2(1,4-{C(N(SiMe3)CHC6H4(PPh2=NSiMe3)-2}2C6H4)] (10). All compounds were characterised by NMR spectroscopy and elemental analyses. The structures of compounds 2, 3, 5, 6 and 9 have been determined by single crystal X-ray diffraction techniques.     

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.     

Synthesis and structures of the [benzamidinato]3- complexes Li3(tmeda)(L1)]2 and [Li(thf)4][Li5(L2)(OEt2)2] [L1 = N(SiMe3)C(Ph)N(SiMe3) and L2 = N(SiMe3)C(C6H4-4)NPh

Reduction at ambient temperature of each of the lithium benzamidinates [Li(L(1))(tmeda)] or [{Li(L(2))(OEt(2))(2)}(2)] with four equivalents of lithium metal in diethyl ether or thf furnished the brown crystalline [Li(3)(L(1))(tmeda)] (1) or [Li(thf)(4)][Li(5)(L(2))(2)(OEt(2))(2)] (2), respectively. Their structures show that in each the [N(R(1))C(R(3))NR(2)](3-) moiety has the three negative charges largely localised on each of N, N' and R = Aryl); a consequence is that the "aromatic" 2,3- and 5,6-CC bonds of R(3) approximate to being double bonds. Multinuclear NMR spectra in C(6)D(6) and C(7)D(8) show that 1 and 2 exhibit dynamic behaviour. [The following abbreviations are used: L(1) = N(SiMe(3))C(Ph)N(SiMe(3)); L(2) = N(SiMe(3))C(C(6)H(4)Me-4)N(Ph); tmeda = (Me(2)NCH(2)-)(2); thf = tetrahydrofuran.] This reduction is further supported by a DFT analysis.     

Reaction of the stable silylene Si[(NCH2But)2C6H4-1,2] with lithium amides

The thermally stable silylene Si[(NCH2But)2C6H4-1,2] 1 undergoes oxidative addition reactions with the lithium amides LiNRR'(R = SiMe3, R' = But; R = SiMe3, R' = C6H3Me2-2,6; R = R' = Me or R = R' = Pri) to afford the new lithium amides Li(THF)2[N(R)Si(SiMe3){(NCH2But)2C6H4-1,2}][R = But2 or R = C6H3Me2-2,6 (3a)] or the new tris(amino)functionalised silyllithiums Li(THF)x[Si{(NCH2But)2C6H4-1,2}NRR'][R = SiMe3, R' = C6H3Me2-2,6, x = 2 (3); R = R'= Me, x = 3 (4) or R = R' = Pri, x = 3 (5)]. Compounds 4 and 5 are stable at ambient temperature but compound 3 is thermally labile and converts into 3a upon heating. The pathway for the formation of 2 and 3 is discussed and the X-ray structures of 2-5 are presented.     

Reactions between a sodium amide Na[N(SiMe3)R1] (R1 = SiMe3, SiMe2Ph or But) and a cyanoalkane RCN (R = Ad or Bu(t))

Reactions between sodium amides Na[N(SiMe3)R1] [R1 = SiMe3 (1), SiMe2Ph (2) or But (3)] and cyanoalkanes RCN (R = Ad or But) were investigated. In each case the nitrile adduct [Na{mu-N(SiMe3)2}(NCR)]2 [R = Ad (1a) or But (1b)], trans-[Na{mu-N(SiMe3)(SiMe2Ph)}(NCR)]2 [R = Ad (2a) or But (2b)], [(Na{mu-N(SiMe3)But})3(NCAd)3] (3a) or [(Na{mu-N(SiMe3)But})3(NCBut)n] [n = 3 (3b) or 2 (3c)] was isolated. The reaction of complexes 3a or 3b with benzene afforded the ketimido complex [Na{mu-N=C(Ad)(Ph)}]6.2C6H6 (4a) or [Na{mu-N=C(But)(Ph)}]6 (4b); the former was also prepared in more conventional fashion from NaPh and AdCN. The synthesis and structure of an analogue of complex 1a, [Li{mu-N(SiMe3)2}(NCAd)]2 (5a), is also presented. The compounds 1a, 1b, 2a, 2b, 3, 3b, 4a, 4b and 5a were characterised by X-ray diffraction.     

Reactions of Li- and Yb-coordinated N,N'-bis(trimethylsilyl)-beta-diketiminates: one- and two-electron reductions, deprotonation, and C-N bond cleavage

The synthesis and characterisation of novel Li and Yb complexes is reported, in which the monoanionic beta-diketiminato ligand has been (i) reduced (SET or 2 [times] SET), (ii) deprotonated, or (iii) C-N bond-cleaved. Reduction of the lithium beta-diketiminate Li(L(R,R'))[L(R,R')= N(SiMe(3))C(R)CHC(R')N(SiMe(3))] with Li metal gave the dilithium derivative [Li(tmen)(mu-L(R,R'))Li(OEt(2))](R = R'= Ph; or, R = Ph, R[prime or minute]= Bu(t)). When excess of Li was used the dimeric trilithium [small beta]-diketiminate [Li(3)(L(R,R[prime or minute]))(tmen)](2)(, R = R'= C(6)H(4)Bu(t)-4 = Ar) was obtained. Similar reduction of [Yb(L(R,R'))(2)Cl] gave [Yb[(mu-L(R,R'))Li(thf)](2)](, R = R[prime or minute]= Ph; or, R = R'= C(6)H(4)Ph-4 = Dph). Use of the Yb-naphthalene complex instead of Li in the reaction with [Yb(L(Ph,Ph))(2)] led to the polynuclear Yb clusters [Yb(3)(L(Ph,Ph))(3)(thf)], [Yb(3)(L(Ph,Ph))(2)(dme)(2)], or [Yb(5)(L(Ph,Ph))(L(1))(L(2))(L(3))(thf)(4)] [L(1)= N(SiMe(3))C(Ph)CHC(Ph)N(SiMe(2)CH(2)), L(2)= NC(Ph)CHC(Ph)H, L(3)= N(SiMe(2)CH(2))] depending on the reaction conditions and stoichiometry. The structures of the crystalline complexes 4, 6x21/2(hexane), 5(C(6)D(6)), and have been determined by X-ray crystallography (and have been published).     

Activation and functionalization of white phosphorus at rhodium: experimental and computational analysis of the [(triphos)Rh (eta1:eta2-P4RR')]Y complexes (triphos=MeC(CH2PPh2)3; R=H, Alkyl, Aryl; R'=2 electrons, H, Me)

Thermal reaction of white phosphorus with [(triphos)RhH(3)] (1) in THF affords [(triphos)Rh(eta(1):eta(2)-P(4)H)] (2), triphos=MeC(CH(2)PPh(2))(3). Similar complexes [(triphos)Rh(eta(1):eta(2)-P(4)R)] (R=Me (7), Et (8), Ph (9)) also form at lower temperature by the reaction of P(4) and [(triphos)Rh(R)(eta(2)-C(2)H(4))] with elimination of ethene. In contrast, a double-insertion process follows the reaction of [(triphos)Rh(H)(eta(2)-C(2)H(4))] and P(4) to generate tetraphosphido ethyl complex 8. Compounds 2, 7, 8 and 9 are thermally unstable and eventually decompose into the cyclotriphosphorus complex [(triphos)Rh(eta(3)-P(3))] (3) plus other unidentified phosphorus-containing species. Otherwise, PH(3) or PH(2)R is generated in the presence of H(2). The formation of PH(3) and 3 is quantitative starting from the precursor 2. The electrophilic attack of MeOTf or HBF(4) on the P(4)R ligand in the complexes 2, 7-9 is regioselective, and yields a cationic product of formula [(triphos)Rh(eta(1):eta(2)-P(4)RR')](+). The direct attack on the substituted p-R phosphorus atom is demonstrated by crossing experiments. Complexes of the latter type have been isolated in the solid state for the combinations R=H and R'=Me (11) or R=Ph and R'=Me (12). The latter species, [(triphos)Rh(eta(1):eta(2)-P(4)PhMe')]OTf.2 CH(2)Cl(2) (OTf=triflate), has been characterised by X-ray methods. The geometry at the metal is better described as a trigonal bipyramidal than pseudo-octahedral. In fact, the P(4)RR' unit acts as a bidentate ligand with its exocyclic PR(2) donor group and the endocyclic, dihapto-coordinated Pdbond;P linkage. The latter group lies in the equatorial plane, in a similar way to a classic olefin ligand that is coordinated to a butterfly-shaped L(4)M fragment (M=d(8)). DFT calculations on a model of 2 and all possible protonated isomers confirm that double substitution at the exocyclic P-donor positions of the open P(4) unit is energetically favoured. A multinuclear and multidimensional NMR analysis confirms that this structure is maintained in solution for both the parent and the protonated compounds.     

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.     

Synthesis and structures of crystalline Li, Al and Sn(II) 1-azaallyls and beta-diketiminates derived from [Li{mu,eta3-N(SiMe3)C(Ad)C(H)SiMe3}]2 (Ad = 1-adamantyl)

The crystalline dimeric 1-azaallyllithium complex [Li{mu,eta(3-N(SiMe3)C(Ad)C(H)SiMe3}]2 (1) was prepared from equivalent portions of Li[CH(SiMe3)2] and 1-cyanoadamantane (AdCN). Complex was used as precursor to each of the crystalline complexes 2-8 which were obtained in good yield. By 1-azaallyl ligand transfer, 1 afforded (i) [Al{eta3-N(SiMe3)C(Ad)C(H)SiMe3}{kappa1-N(SiMe3)C(Ad)=C(H)SiMe3-E}Me] (5) with [AlCl2Me](2), (ii) [Sn{eta3-N(SiMe3)C(Ad)C(H)SiMe3}2] (7) with Sn[N(SiMe3)2]2, and (iii) [Li(N{C(Ad)=C(H)SiMe3-E}{Si(NN)SiMe3})(thf)2] (8) with the silylene Si[(NCH(2)Bu(t))2C6H(4)-1,2] [= Si(NN)]. By insertion into the C[triple bond, length as m-dash]N bond of the appropriate cyanoarene RCN, gave the beta-diketiminate [Li{mu-N(SiMe3)C(Ad)C(H)C(R)NSiMe3}]2 [R = Ph (2), C(6)H(4)Me-4 (3)], and yielded [Al{kappa2-N(SiMe3)C(Ad)C(H)C(Ph)NSiMe3}{kappa1-N(SiMe3)C(Ad)=C(H)SiMe3-E}Me] (6). The beta-diketiminate [Al{kappa2-N(SiMe3)C(Ad)C(H)C(Ph)NSiMe3}Me2] (4) was prepared from 2 and [AlClMe2]2. The X-ray structures of 1 and 3-8 are presented. Multinuclear NMR spectra in C6D6 or C6D5CD3 have been recorded for each of 1-8; such data on 8 revealed that in solution two minor isomers were also present.     

Structural, spectroscopic and magnetic properties of M[R2P(E)NP(E)R'2]2 complexes, M = Co, Mn, E = S, Se and R, R' = Ph or iPr. Covalency of M-S bonds from experimental data and theoretical calculations

The S/Se-containing bidentate ligands LH of the type R2P(E)NHP(E)R'2, E = S, Se and R, R' = Ph or iPr have been employed to synthesize ML2 (M = Mn, Co) complexes which contain the biologically important MS4 core. Theoretical calculations on the LH and L- forms of the ligands probe the geometric and electronic changes induced by the deprotonation of the LH form, which are correlated with structural data from X-ray crystallography. These results reflect the flexibility of the ligands, which enables them to be rather versatile with respect to the formation of ML2 complexes with varied geometries and MEPNPE metallacycle conformations. A series of old and new ML2 complexes have been synthesized and their structural, spectroscopic and magnetic properties characterized in detail. The nephelauxetic ratio beta of the CoL2 complexes provides evidence of covalent interactions, whereas the EPR properties of the MnL2 complexes are interpreted on the basis of predominant ionic interactions, between the metal center and the ligands, respectively. Additional evidence for the existence of covalent interactions in the CoL2 complexes (R = Ph, iPr, or mixed Ph/iPr), is offered by comparisons between their 31P NMR. The aforementioned notations are supported by extensive theoretical calculations on the ML2 (E = S, R = Me) modelled structures, which probe the covalent and ionic character of the M-S bonds when M = Co or Mn. Wider implications of the findings of the present study on the M-S covalency and its importance in the active sites of various metalloenzymes are also discussed.     

Synthesis, X-ray diffraction studies, and DFT calculations on hexacoordinated germanium derivatives: the case of germaspirobis(ocanes)

Synthesis of the title compounds, viz. [RN(CH2CHR'O)2]2Ge (1, R = Me, R' = H; 2, R = Me, R' = Ph; 3, R = Ph, R' = H), by the reaction of 2 equiv of corresponding dialkanolamines RN(CH2CHR'OH)2 (4, R = Me, R' = H; 5, R = Me, R' = Ph; 6, R = Ph, R' = H) with (AlkO)4Ge is reported. Composition and structures of all novel compounds were established by 1H and 13C NMR spectroscopy and mass spectrometry as well as elemental analysis data. The single-crystal X-ray diffraction of 2 has clearly indicated the presence of two transannular interactions Ge<--N in the compound. N atoms are cis-orientated. The compound 3 possesses long Ge...N distances. The structural data obtained from geometry optimizations by DFT calculations on 1-3 reproduces experimental results. Both cis- and trans-isomers were studied, and cis-configuration was found to be more thermodynamically stable for all three compounds. The transition states for possible cis <--> trans rearrangement processes in 1-3 were calculated. The properties of the Ge-O and Ge<--N bonds in 1-3 were analyzed by the AIM approach. The interactions between the Ge atom and N atoms as well as O atoms possess predominantly ionic character.     

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).     

Interaction of tertiary phosphines with lignin-type, alpha,beta-unsaturated aldehydes in water

To learn more about the bleaching action of pulps by (hydroxymethyl)phosphines, lignin chromophores, such as the alpha,beta-unsaturated aromatic aldehydes, sinapaldehyde, coniferylaldehyde, and coumaraldehyde, were reacted with the tertiary phosphines R2R'P [R = R' = Me, Et, (CH2)3OH, iPr, cyclo-C6H11, (CH2)2CN; R = Me or Et, R' = Ph; R = Ph, R' = Me, m-NaSO3-C6H4] in water at room temperature under argon. In all cases, initial nucleophilic attack of the phosphine occurs at the activated C=C bond to form a zwitterionic monophosphonium species. With the phosphines PR3 [R = Me, Et, (CH2)3OH] and with R2R'P (R = Me or Et, R' = Ph), the zwitterion undergoes self-condensation to give a bisphosphonium zwitterion that can react with aqueous HCl to form the corresponding dichloride salts (as a mixture of R,R- and S,S-enantiomers); X-ray structures are presented for the bisphosphonium chlorides synthesized from the Et3P and Me3P reactions with sinapaldehyde. With the more bulky phosphines, iPr3P, MePPh2, (cyclo-C6H11)3P, and Na[Ph2P(m-SO3-C6H4)], only an equilibrium of the monophosphonium zwitterion with the reactant aldehyde is observed. The weakly nucleophilic [NC(CH2)2]3P does not react with sinapaldehyde. An analysis of some exceptional 1H NMR data within the prochiral phosphorus centers of the bisphosphonium chlorides is also presented.     

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.     

Interactions of Rh(III)-dihydrido-bis(phosphine) complexes with semicarbazones

Interaction of cis,trans,cis-[Rh(H)2(PR3)2(acetone)2]PF6 complexes (R = aryl or R3 = Ph2Me, Ph2Et) under H2 with E-semicarbazones gives the Rh(III)-dihydrido-bis(phosphine)-semicarbazone species cis,trans-[Rh(H)2(PR3)2{R'(R' ')C=N-N(H)CONH2}]PF6, where R' and R' ' are Ph, Et, or Me. The complexes are generally characterized by elemental analysis, 31P{1H} NMR, 1H NMR, and IR spectroscopies, and MS. X-ray analysis of three PPh3 complexes reveals chelation of E-semicarbazones by the imine-N atom and the carbonyl-O atom. In contrast, the corresponding reaction of [Rh(H)2(PPhMe2)2(acetone)2]PF6 with acetophenone semicarbazone gives the ortho-metalated-semicarbazone species cis-[RhH(PPhMe2)2{o-C6H4(Me)C=N-N(H)CONH2}]PF6. The X-ray structure of E-propiophenone semicarbazone is also reported. Rhodium-catalyzed, homogeneous hydrogenation of semicarbazones was not observed even at 40 atm H2.     

Scope and limitations of the base-catalyzed phospha-peterson P=C bond-forming reaction

Phosphaalkenes (MesP=CRR': R = R' = Ph (1a); R = R' = 4-FC6H4 (1b); R = Ph, R' = 4-FC6H4 (1c); R = R' = 4-OMeC6H4 (1d); R = Ph, R' = 4-OMeC6H4 (1e); R = Ph, R' = 2-pyridyl (1f)) are prepared from the reaction of MesP(SiMe3)2 and O=CRR' in the presence of a trace of KOH or NaOH. The base-catalyzed phospha-Peterson reaction is quantitated by NMR spectroscopy, and isolated yields of phosphaalkene between 40 and 70% are obtained after vacuum distillation and/or recrystallization. The asymmetrically substituted phosphaalkenes (1c, 1e, 1f) form as 1:1 mixtures of E and Z isomers; however, X-ray crystallography reveals that the E isomers crystallize preferentially. Interestingly, E-1e and E-1f readily isomerize in solution in the dark, although the rate of isomerization is much faster when samples are exposed to light. X-ray crystal structures of 1b, E-1e, and E-1f reveal that the P=C bond lengths (average of 1.70 A) are in the long end of the range typically found in phosphaalkenes (1.61-1.71 A). Attempts to prepare isolable P-adamantyl phosphaalkenes following this route were unsuccessful. Although AdP=CPh2 (2a) is detected by 31P NMR spectroscopy, attempts to isolate this species afforded the 1,2-diphosphetane (AdPCPh2)2 (3a), which was characterized by X-ray crystallography.