金属有机多齿配体配位化学: 双核化合物的形成促使铁卡宾键的稳定化

单核物MXn[MXn=HgCl2,HgI2,CdCl2,K2Zn(SCN)4]与1,3-二硫铁卡宾化合物Fe(CO)2.(Ph2PPy)2[CS2C2(CO2Me)2]反应生成稳定的双核铁卡宾配合物FeM(μ-Ph2PPy)2[CS2C2.(CO2Me)2](CO2)2X2(Ph2PPy为2-二苯基膦基吡啶)。这些配合物为IR,^3^1P NMR, 及元素分析所证实。     

金属-金属键形成反应的研究: [η^5-RO~2CC~5H~4(CO)~3M]~2Hg(R=Me,Et;M=Cr,Mo,W)的合成及鉴定

η~5-RO_2CC_5H_4(CO)_3MNa(1)与R~1HgCl(2,R~1=Me,Et,Ph)可发生一种非预期的金属键形成反应,生成[η~5-RO_2CC_5H_4(CO)_3M]_2Hg(3a—3f)(R=Me,Et;M=Cr,Mo,W)。对反应中间物η~5EtQ_2CC_5H_4(CO)_3MoHgPh的研究表明:反应是按缩合及对称化两步机理进行的。3e(R=Et,M=Mo)属三斜晶系,空间群P-1。a=0.6333(1),b=0.7712(1),c=1.4204(4)nm;a=77.31(1),β=74.51(2),γ=68.72(1)°;V=0.61714nm~3;Z=1;D_x=2.246g/cm~3;R=0.044.     

金属-金属键形成反应的研究: [η^5-RO~2CC~5H~4(CO)~3M]~2Hg(R=Me,Et;M=Cr,Mo,W)的合成及鉴定

η^5-RO~2CC~5H~4(CO)~3MNa与R^1HgCl,R^1=Me, Et, Ph)可发生一种非预期的金属键形成反应, 生成[η^5-RO~2CC~5H~4(CO)~3M]~2Hg(R=Me,Et;M=Cr,Mo,W)。对反应中间物η^5-EtO~2CC~5H~4(CO)~3MoHgPh的研究表明: 反应是按缩合及对称化两步机理进行的。(R=Et,M=Mo)属三斜晶系, 空间群P-1。a=0.6333(1), b=0.7712(1), c=1.4204(4)nm; a=77.31(1),β=74.51(2), γ=68.72(1)^°; V=0.61714nm^3;Z=1;D~x=2.246g/cm^3;R=0.044。     

铁铂硫原子簇化合物的合成与结构研究 V: [MoFe3S4]类立方烷簇合物的转化反应和[Et4N]3[Mo2Fe6S8(SC6H4CH3-m)3Cl6]的晶体结构

具[MoFe2S4]类立方烷结构单元的双类立方烷化合物[Et4N]4[Mo2Fe7S8(SR)12](1a,R=Ph; 1b, R=tolyl-m)或单类立方烷化合物[MoFe3S4(dteR2)5](2a, R=Me; 2b, R=Et)与酰氯在乙腈中反应, 分别得到不含Fe桥的双类立方烷化合物(Et4N)3[Mo2Fe6S8(SR)3Cl6](3a, R=Ph; 3b, R=toly-m)与[MoFe3S4]骨架支解后的Fe(dteR2)2Cl(4a, R=Me; 4b, R=Et)。说明在相同反应条件下, [MoFe3S4]单元在1中比在2中稳定, 本文首次将1型与3型结构通过一步化学反应连系起来。3型化合物的产生得到X射线衍射测定及^1H NMR谱的证实。本文报道3b的单晶结构及3的^!H NMR数据, 3b属六方晶系, P63/m, a=1.6827(3), c=1.5951(16)nm; V=3.91158nm^3; Dc=1.491g/cm^3;Z=2; F(000)=1780; 偏离因子R=0.048, 化合物2与酰氯反应产生4, 由红外及紫外可见光谱证实。     

铁铂硫原子簇化合物的合成与结构研究 V: [MoFe3S4]类立方烷簇合物的转化反应和[Et4N]3[Mo2Fe6S8(SC6H4CH3-m)3Cl6]的晶体结构

具[MoFe2S4]类立方烷结构单元的双类立方烷化合物[Et4N]4[Mo2Fe7S8(SR)12](1a,R=Ph; 1b, R=tolyl-m)或单类立方烷化合物[MoFe3S4(dteR2)5](2a, R=Me; 2b, R=Et)与酰氯在乙腈中反应, 分别得到不含Fe桥的双类立方烷化合物(Et4N)3[Mo2Fe6S8(SR)3Cl6](3a, R=Ph; 3b, R=toly-m)与[MoFe3S4]骨架支解后的Fe(dteR2)2Cl(4a, R=Me; 4b, R=Et)。说明在相同反应条件下, [MoFe3S4]单元在1中比在2中稳定, 本文首次将1型与3型结构通过一步化学反应连系起来。3型化合物的产生得到X射线衍射测定及^1H NMR谱的证实。本文报道3b的单晶结构及3的^!H NMR数据, 3b属六方晶系, P63/m, a=1.6827(3), c=1.5951(16)nm; V=3.91158nm^3; Dc=1.491g/cm^3;Z=2; F(000)=1780; 偏离因子R=0.048, 化合物2与酰氯反应产生4, 由红外及紫外可见光谱证实。     

四羰基双[2,5-二(三甲硅基)-1-甲基环戊二烯基]

由甲基环戊二烯经两步类似反应向其环上引入两个Me3Si取代基, 生成(Me3Si)2-MeC5H3, 后者与Fe(CO)5反应除生成预期的双核Fe-Fe键产物[η^5-{Me3Si)2MeC5H2}Fe(CO)]2-(μ-CO)2(2)外, 还分离到小量单核化合物η^5-[(Me2Si)2MeC5H2]Fe(CO)2Cl(3), 2与碘反应生成Fe-Fe键断裂的单核铁碘化物(4)。2经Na/Hg还原生成Fe-Fe键断裂的铁负离子, 后者随即分别与数种氯化物反应, 生成在铁原子上引入相应取代基的铁衍生物η^5-[(Me3Si)2MeC5H2]Fe(CO)2R(R=PhCH2, 5; CH2COOC2H5, 6; Ph3Sn, 7; Ph2SnCl, 8)。测定了4的晶体结构, 晶体属单斜晶系, P21/c空间群, 晶胞参数a=0.7333(1), b=2.0089(3),c=1.3323(4)nm; β=92.02(2)°, V=1.962(1)nm^3, Z=4。     

四羰基双[2,5-二(三甲硅基)-1-甲基环戊二烯基]

由甲基环戊二烯经两步类似反应向其环上引入两个Me3Si取代基, 生成(Me3Si)2-MeC5H3, 后者与Fe(CO)5反应除生成预期的双核Fe-Fe键产物[η^5-{Me3Si)2MeC5H2}Fe(CO)]2-(μ-CO)2(2)外, 还分离到小量单核化合物η^5-[(Me2Si)2MeC5H2]Fe(CO)2Cl(3), 2与碘反应生成Fe-Fe键断裂的单核铁碘化物(4)。2经Na/Hg还原生成Fe-Fe键断裂的铁负离子, 后者随即分别与数种氯化物反应, 生成在铁原子上引入相应取代基的铁衍生物η^5-[(Me3Si)2MeC5H2]Fe(CO)2R(R=PhCH2, 5; CH2COOC2H5, 6; Ph3Sn, 7; Ph2SnCl, 8)。测定了4的晶体结构, 晶体属单斜晶系, P21/c空间群, 晶胞参数a=0.7333(1), b=2.0089(3),c=1.3323(4)nm; β=92.02(2)°, V=1.962(1)nm^3, Z=4。     

2-苯亚胺官能化吲哚基铕胺基配合物与芳基取代甲脒的反应性（英文）

2-(苯亚胺基次甲基)吲哚铕胺基配合物[η1∶η1-2-(C6H5NH=CH)C8H5N]2Eu[N(Si Me3)2](1)与二芳基取代甲脒(2,6-R2C6H3N=CHNH(C6H3R2-2,6)(R=iPr(2),Me(3))经过配体交换反应,分别得到了含吲哚基脒基铕配合物[η1∶η1-2-(C6H5NH=CH)C8H5N]Eu[(η3-2,6-iPr2C6H3)N=CHN(C6H3iPr2-2,6)][N(Si Me3)2](4)和含脒基的稀土铕配合物[(η3-2,6-Me2C6H3)N=CHN(C6H3Me2-2,6)]2Eu[N(Si Me3)2](5)。结果表明,脒基的位阻显著影响了吲哚基稀土金属胺基配合物与二芳基取代甲脒的配体交换反应。配合物4和5通过IR、元素分析和X射线单晶衍射分析进行了表征。     

环戊二烯基二硫代氨基甲酸钛(Ⅳ), 锆(Ⅳ)配合物的合成及结构表征

(RCp)~2MCl~2, (RCp)TiCl~3分别与N-(4-苯基-2-噻唑基)二硫代氨基甲酸钾和3-苯基-5-(2-呋喃基)-吡唑啉-1-二硫代甲酸钠进行反应, 合成了三十二个未见报道的(RCp)M(S~2CNHR')~nCl~3~-~n,(RCp)~2M-(S~2CNHR')~nCl~2~-~n [R=H, Me; M=Ti, Zr; R'=4-苯基噻唑基(PTDTC), n=1,2,3] 以及(RCp)M(S~2CR^2)~nCl~3~-~n,(RCp)~2M(S~2CR^2)~nCl~2~n[R=H,Me;M=Ti,Zr,R^2=3-苯基-金-(呋喃-2)吡唑啉基(PFPDTC), n=1,2,3]型配合物。所有配合物经元素分析、UV、IR和^1H NMR谱证实, 二硫代氨基甲酸是以双齿配体键合的。     

[Ph(Me3Si)N]3Yb(THF)的合成及其催化Tischenko反应的研究

通过无水YbCl3和Ph[(CH3)3N]Li在四氢呋喃中反应,合成了目标化合物[Ph(Me3Si)N]3Yb(THF),该化合物经过元素分析,红外光谱以及X单晶结构表征.研究表明该配合物以较高活性催化芳醛的Tischenko反应.     

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.     

2 + 3] cycloaddition of nitrones to platinum-bound organonitriles: effect of metal oxidation state and of nitrile substituent

The ligated benzonitriles in the platinum(II) complex [PtCl2(PhCN)2] undergo metal-mediated [2 + 3] cycloaddition with nitrones -ON+(R3)=C(R1)(R2) [R1/R2/R3 = H/Ph/Me, H/p-MeC6H4/Me, H/Ph/CH2Ph] to give delta 4-1,2,4-oxadiazoline complexes, [PtCl2(N=C(Ph)O-N(R3)-C(R1)(R2))2] (2a, 4a, 6a), as a 1:1 mixture of two diastereoisomers, in 60-75% yields, while [PtCl2(MeCN)2] is inactive toward the addition. However, a strong activation of acetonitrile was reached by application of the platinum(IV) complex [PtCl4(MeCN)2] and both [PtCl4(RCN)2] (R = Me, Ph) react smoothly with various nitrones to give [PtCl4(N=C(R)O-N(R3)-C(R1)(R2))2] (1b-6b). The latter were reduced to the corresponding platinum(II) complexes [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) by treatment with PhCH2NHOH, while the reverse reaction, i.e. conversion of 1a-6a to 1b-6b, was achieved by chlorination with Cl2. The diastereoisomers of [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) exhibit different kinetic labilities, and liberation of the delta 4-1,2,4-oxadiazolines by substitution with 1,2-bis(diphenylphosphino)ethane (dppe) in CDCl3 proceeds at different reaction rates to give free N=C(R)O-N(R3)-C(R1)(R2) and [PtCl2(dppe)] in almost quantitative NMR yield. All prepared compounds were characterized by elemental analyses, FAB mass spectrometry, and IR and 1H, 13C(1H), and 195Pt (metal complexes) NMR spectroscopies; X-ray structure determination of the first (delta 4-1,2,4-oxadiazoline)Pt(II) complexes was performed for (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)Ph)2] (1a) (a = 9.3562(4), b = 9.8046(3), c = 13.1146(5) A; alpha = 76.155(2), beta = 83.421(2), gamma = 73.285(2) degrees; V = 1117.39(7) A3; triclinic, P1, Z = 2), (R,S)-meso-[PtCl2(N=C(Ph)O-N(Me)-C(H)Ph)2] (2a) (a = 8.9689(9), b = 9.1365(5), c = 10.1846(10) A; alpha = 64.328(6), beta = 72.532(4), gamma = 67.744(6) degrees; V = 686.82(11) A3; triclinic, P1, Z = 1), (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)(p-C6H4Me))2] (3a) (a = 11.6378(2), b = 19.0767(7), c = 11.5782(4) A; beta = 111.062(2) degrees; V = 2398.76(13) A3; monoclinic, P2(1)/c, Z = 4), and (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(CH2Ph)-C(H)Ph2] (5a) (a = 10.664(2), b = 10.879(2), c = 14.388(3) A; alpha = 73.11(3), beta = 78.30(3), gamma = 88.88(3) degrees; V = 1562.6(6) A3; triclinic, P1, Z = 2).     

Fast carbon dioxide fixation by 2,6-pyridinedicarboxamidato-nickel(II)-hydroxide complexes: influence of changes in reactive site environment on reaction rates

The planar complexes [Ni(II)(pyN(2)(R2))(OH)](-), containing a terminal hydroxo group, are readily prepared from N,N'-(2,6-C(6)H(3)R(2))-2,6-pyridinedicarboxamidate(2-) tridentate pincer ligands (R(4)N)(OH), and Ni(OTf)(2). These complexes react cleanly and completely with carbon dioxide in DMF solution in a process of CO(2) fixation with formation of the bicarbonate product complexes [Ni(II)(pyN(2)(R2))(HCO(3))](-) having η(1)-OCO(2)H ligation. Fixation reactions follow second-order kinetics (rate = k(2)'[Ni(II)-OH][CO(2)]) with negative activation entropies (-17 to -28 eu). Reactions were monitored by growth and decay of metal-to-ligand charge-transfer (MLCT) bands at 350-450 nm. The rate order R = Me > macro > Et > Pr(i) > Bu(i) > Ph at 298 K (macro = macrocylic pincer ligand) reflects increasing steric hindrance at the reactive site. The inherent highly reactive nature of these complexes follows from k(2)' ≈ 10(6) M(-1) s(-1) for the R = Me system that is attenuated by only 100-fold in the R = Ph complex. A reaction mechanism is proposed based on computation of the enthalpic reaction profile for the R = Pr(i) system by DFT methods. The R = Et, Pr(i), and Bu(i) systems display biphasic kinetics in which the initial fast process is followed by a slower first order process currently of uncertain origin.     

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.     

Oxo transfer reactions mediated by bis(dithiolene)tungsten analogues of the active sites of molybdoenzymes in the DMSO reductase family: comparative reactivity of tungsten and molybdenum.

The discovery of tungsten enzymes and molybdenum/tungsten isoenzymes, in which the mononuclear catalytic sites contain a metal chelated by one or two pterin-dithiolene cofactor ligands, has lent new significance to tungsten-dithiolene chemistry. Reaction of [W(CO)(2)(S(2)C(2)Me(2))(2)] with RO(-) affords a series of square pyramidal desoxo complexes [W(IV)(OR')(S(2)C(2)Me(2))(2)](1)(-), including R' = Ph (1) and Pr(i)() (3). Reaction of 1 and 3 with Me(3)NO gives the cis-octahedral complexes [W(VI)O(OR')(S(2)C(2)Me(2))(2)](1)(-), including R' = Ph (6) and Pr(i)() (8). These W(IV,VI) complexes are considered unconstrained versions of protein-bound sites of DMSOR and TMAOR (DMSOR = dimethylsulfoxide reductase, TMAOR = trimethylamine N-oxide reductase) members of the title enzyme family. The structure of 6 and the catalytic center of one DMSO reductase isoenzyme have similar overall stereochemistry and comparable bond lengths. The minimal oxo transfer reaction paradigm thought to apply to enzymes, W(IV) + XO --> W(VI)O + X, has been investigated. Direct oxo transfer was demonstrated by isotope transfer from Ph(2)Se(18)O. Complex 1 reacts cleanly and completely with various substrates XO to afford 6 and product X in second-order reactions with associative transition states. The substrate reactivity order with 1 is Me(3)NO > Ph(3)AsO > pyO (pyridine N-oxide) > R(2)SO > Ph(3)PO. For reaction of 3 with Me(3)NO, k(2) = 0.93 M(-)(1) s(-)(1), and for 1 with Me(2)SO, k(2) = 3.9 x 10(-)(5) M(-)(1) s(-)(1); other rate constants and activation parameters are reported. These results demonstrate that bis(dithiolene)W(IV) complexes are competent to reduce both N-oxides and S-oxides; DMSORs reduce both substrate types, but TMAORs are reported to reduce only N-oxides. Comparison of k(cat)/K(M) data for isoenzymes and k(2) values for isostructural analogue complexes reveals that catalytic and stoichiometric oxo transfer, respectively, from substrate to metal is faster with tungsten and from metal to substrate is faster with molybdenum. These results constitute a kinetic metal effect in direct oxo transfer reactions for analogue complexes and for isoenzymes provided the catalytic sites are isostructural. The nature of the transition state in oxo transfer reactions of analogues is tentatively considered. This research presents the first kinetics study of substrate reduction via oxo transfer mediated by bis(dithiolene)tungsten complexes.     

A Route to 1,2,4-oxadiazoles and their complexes via platinum-mediated 1,3-dipolar cycloaddition of nitrile oxides to organonitriles

A significant activation of the Ctbd1;N group in organonitriles upon their coordination to a platinum(IV) center has been found in the reaction of [PtCl(4)(RCN)(2)] (R = Me, Et, CH(2)Ph) with the nitrile oxides 2,4,6-R'(3)C(6)H(2)CNO (R' = Me, OMe) to give the (1,2,4-oxadiazole)platinum(IV) complexes (R = Me, R' = Me (1); R = Et, R' = Me (2); R = Et, R' = OMe (3); R = CH(2)Ph, R' = Me (4)); the [2 + 3] cycloaddition was performed under mild conditions (unless poor solubility of [PtCl(4)(RCN)(2)] precludes the reaction) starting even from complexed acetonitrile and propionitrile, which exhibit low reactivity in the free state. The reaction between complexes 2-4 and 1 equiv of Ph(3)P=CHCO(2)Me in CH(2)Cl(2) leads to the appropriate platinum(II) complexes (5-7); the reduction failed only in the case of 1 insofar as this complex is insoluble in the most common organic solvents. All the platinum compounds were characterized by elemental analyses, FAB mass spectrometry, and IR and (1)H, (13)C((1)H), and (195)Pt NMR spectroscopies, and three of them also by X-ray crystallography. The oxadiazoles formed in the course of the metal-mediated reaction were liberated almost quantitatively from their Pt(IV) complexes by reaction of the latter (complexes 2-4) with an excess of pyridine in chloroform, giving free 1,2,4-oxadiazoles and trans-[PtCl(4)(pyridine)(2)]; the sequence of the Pt(IV)-mediated [2 + 3] cycloaddition and the liberation opens up an alternative route for the preparation of this important class of heterocycles.     

Constrained geometry organoactinides as versatile catalysts for the intramolecular hydroamination/cyclization of primary and secondary amines having diverse tethered C-C unsaturation

A series of "constrained geometry" organoactinide complexes, (CGC)An(NMe)2 (CGC = Me2Si(eta5-Me4C5)(tBuN); An = Th, 1; U, 2), has been prepared via efficient in situ, two-step protodeamination routes in good yields and high purity. Both 1 and 2 are quantitatively converted to the neutrally charged, solvent-free dichlorides (1-Cl2, 2-Cl2) and slightly more soluble diiodides (1-I2, 2-I2) with excess Me3Si-X (X = Cl, I) in non-coordinating solvents. The new complexes were characterized by NMR spectroscopy, elemental analysis, and (for 1 and 2) single-crystal X-ray diffraction, revealing substantially increased metal coordinative unsaturation vs the corresponding Me2SiCp' '2AnR2 (Cp' ' = eta5-Me4C5; An = Th, R = CH2(SiMe3), 3; An = U, R = CH2Ph, 4) and Cp'2AnR2 (Cp' = eta5-Me5C5 ; An = Th, R = CH2(SiMe3), 5; An = U, R = CH2(SiMe3), 6) complexes. Complexes 1-6 exhibit broad applicability for the intramolecular hydroamination of diverse C-C unsaturations, including terminal and internal aminoalkenes (primary and secondary amines), aminoalkynes (primary and secondary amines), aminoallenes, and aminodienes. Large turnover frequencies (Nt up to 3000 h-1) and high regioselectivities (>/=95%) are observed throughout, along with moderate to high diastereoselectivities (up to 90% trans ring closures). With several noteworthy exceptions, reactivity trends track relative 5f ionic radii and ancillary ligand coordinative unsaturation. Reactivity patterns and activation parameters are consistent with a reaction pathway proceeding via turnover-limiting C=C/CC insertion into the An-N sigma-bond.     

Nitrile-amidine coupling at Pt(IV) and Pt(II) centers. An easy entry to imidoylamidine complexes

Treatment of trans-[PtCl4(RCN)2] (R = Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl3 (R = Et, Ph), or in CHCl3 solution (R = NEt2) results in the formation of the imidoylamidine complexes trans-[PtCl4{NH=C(R)N=C(Ph)NHPh}2] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph3P=CHCO2Me in CH2Cl2 (40 degrees C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2{NH=C(R)NC(Ph)=NPh}2] (R = Ph, 5; R = NEt2, 6), accordingly, and the phosphonium salt [Ph3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P=CHCO2Me at 50 degrees C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt2)NC(Ph)=NPh}2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl3 is used. When the platinum(II) complex trans-[PtCl2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh] x HCl (7) are formed. The reaction of trans-[PtCl2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}2] (12-15). The treatment of cis-[PtCl2(RCN)2] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl2{NH=C(R)NHC(Ph)=NHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C{1H}, and 195Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.     

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.     

A new mode of reactivity for pyridine N-oxide: C-H activation with uranium(IV) and thorium(IV) bis(alkyl) complexes

Uranium(IV) and thorium(IV) bis(alkyl) complexes of the type (C5Me5)2AnR2 (An = U, Th; R = CH3, CH2Ph) activate the sp2 and sp3 hybridized C-H bonds in pyridine N-oxide and lutidine N-oxide to produce the corresponding cyclometalated complexes, (C5Me5)2An(R)[eta2-(O,C)-ONC5H4] and (C5Me5)2An(R)[eta2-(O,C)-ON-2-CH2-5-CH3-C5H3]. These provide rare examples of C-H activation chemistry mediated by actinide metal centers. This chemistry is in contrast to the known oxygen atom transfer reactivity patterns of pyridine N-oxides with oxophilic metal complexes and constitutes a new mode of reactivity for pyridine N-oxides.