Search

National Nature Science Foundation of China (NNSFC)[20972129, 91027014]; Research Fund for New Teacher of Higher Education[200803841012]; National Fund for Fostering Talents of Basic Science (NFFTBS)[J1030415]

LGe(Se)OH (2) (L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3) was obtained by oxidative addition of red selenium to LGeOH (1). Compound 2 was characterized by IR, multinuclear NMR, EI-MS, and single-crystal X-ray diffraction. Furthermore, theoretical calculations of the acid strength (pKa) of compound 2 and LGe(S)OH were carried out by means of density functional theory (DFT).

A kinetically controlled trans bifunctionalized organoimido derivative of hexamolybdate, (n-Bu(4)N)(2){trans-[Mo(6)O(17)(NAr)(2)]} (Ar = 2,6-dimethylphenyl) 1, in which the two 2,6-dimethylphenylimido groups are bonded to hexamolybdate at the trans positions, has been successfully synthesized in ca. 60% yield under mild reaction conditions. Its trans structure has been confirmed by a single-crystal X-ray diffraction study. In the crystals, cluster anions of 1 self-assemble into a 3D netlike structure via two different kinds of C-H...O hydrogen bondings, in which 1D supramolecular rectangular channels containing tetrabutylammonium cations form along the a axis. Compound 1 has also been characterized by (1)H NMR, IR, and UV-vis spectroscopic studies. UV-vis-near-IR reflectance spectroscopy measurements reveal the compound's nature of semiconductivity with an optical energy gap of 2.55 eV.

Reaction of LAl (1) or [LAl{η2-C2(SiMe3)2}] (2) {L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3} with azobenzene affords a five-membered ring compound [LAl{N(H)-o-C6H4N(Ph)}] (3). In the formation of 3 a three-membered intermediate [LAl(η2-N2Ph2)] (A) is suggested by a [1 + 2] cycloaddition reaction; A is not stable and further rearranges to 3. DFT calculations on similar compounds with modified L' {L' = HC[(CMe)(NPh)]2} show that the complexation energy of the reaction of L'Al with azobenzene to form [L'Al(η2-N2Ph2)] is about–39 kcal mol–1, and the best estimate of the energy difference between [L'Al(η2-N2Ph2)] and [L'Al{N(H)-o-C6H4N(Ph)}] is–76 kcal mol–1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The compounds [MoCl(NAr)2R] (R=CH2CMe2Ph (1) or CH2CMe3(2); Ar=2,6-Pri2C6H3) have been prepared from [MoCl2(NAr)2(dme)] (dme=1,2-dimethoxyethane) and one equivalent of the respective Grignard reagent RMgCl in diethyl ether. Similarly, the mixed-imido complex [MoCl2(NAr)(NBut)(dme)] affords [MoCl(NAr)(NBut)(CH2CMe2Ph)] (3). Chloride substitution reactions of 1 with the appropriate lithium reagents afford the compounds [MoCp(NAr)2(CH2CMe2Ph)] (4) (Cp=cyclopentadienyl), [MoInd(NAr)2(CH2CMe2Ph)] (5) (Ind=Indenyl), [Mo(OBut)(NAr)2(CH2CMe 2Ph)] (6), [MoMe(NAr)2(CH2CMe2Ph)] (7), [MoMe(PMe3)(NAr)2(CH2CMe 2Ph)] (8) (formed in the presence of PMe3) and [Mo(NHAr)(NAr)2(CH2CMe2P h)](9). In the latter case, a by-product {[Mo(NAr)2(CH2CMe2Ph) ]2(μ-O)}(10) has also been isolated. The crystal structures of 1, 4, 5 and 10 have been determined. All possess distorted tetrahedral metal centres with cis near-linear arylimido ligands; in each case (except 5, for which the evidence is unclear) there are α-agostic interactions present.

The nature of the bonding between the two M( μ -NAr # )imido monomers [M = Si, Ge, Sn, Pb; Ar # =C 6 H 3 -2,6-(C 6 H 2 -2,4,6-R 3 ) 2 ; R = Me, iPr] in the {M( μ -NAr # )} 2 dimer is investigated with the help of a newly developed energy and density decomposition scheme as well as molecular dynamics. The approach combines the extended transition state energy decomposition method with the natural orbitals for chemical valence density decomposition scheme within the same theoretical framework. The dimers are kept together by two σ bonds and two π bonds. The σ bonding has two major contributions. The fi rst is a dative transfer of charge from nitrogen to M. It amounts to − 188 kcal/mol for {Si( μ -NAr # )} 2 , − 152 kcal/mol for {Ge( μ -NAr # )} 2 with − 105 kcal/mol for {Sn( μ -NAr # )} 2 , and − 79 kcal/mol for {Pb( μ -NAr # )} 2 . The second is a charge buildup within the ring made up of the two dimers. It amounts to − 82 kcal/mol for M = Si with − 61 kcal/mol for M = Ge and ∼− 50 kcal/mol for M = Sn and Pb. We fi nally have π bonding with a donation of charge from M to nitrogen. It has a modest contribution of ∼− 30 kcal/mol. The presence of isopropyl (iPr) groups is further shown to stabilize{M( μ -NAr # )} 2 [M = Si, Ge, Sn, Pb; Ar # =C 6 H 3 -2,6-(C 6 H 2 -2,4,6-iPr 3 ) 2 ] compared to the methylated derivatives (R = Me) through attractive van der Waals dispersion interactions.

Use of the very bulky amidinate ligand [tBuC(NAr)2]–(= Piso, Ar = C6H3iPr2–2,6) allowed the synthesis and structural characterization of the chloro-functional complex (Piso)2CeCl (1). Complex 1 represents a rare example of an unsolvated bis(amidinato) lanthanide chloride. An X-ray diffraction study confirmed the presence of a pentacoordinate cerium(III) complex.

LGeOH (1; L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3) reacted with iron and manganese complexes to give LGe(OH)Fe(CO)4 (2) and LGe(OH)Mn(Cp)(CO)2 (3; Cp = cyclopentadienyl). Compounds 2 and 3 were characterized by IR, multinuclear NMR, EI-MS, and single-crystal X-ray diffraction.

Mixed-valent imido-bridged dinuclear titanium complexes, [Cp(2)Co][{(C(5)R(5))TiCl}(2)(μ-NAr)(2)] (R = H, Me; Ar = 3,5-(CF(3))(2)C(6)H(3)), were prepared by one-electron reduction of the corresponding [(C(5)R(5))TiCl](2)(μ-NAr)(2). One unpaired electron is delocalized in the central Ti(μ-NR)(2)Ti core as the first example of a fully delocalized mixed-valent imido-bridged [Ti(2)](7+) species.

The complex Ru(TPP)(NAr)(2) inserts a nitrene group into allylic and benzylic C-H bonds and is the key intermediate in the ruthenium porphyrin-catalyzed amination of hydrocarbons by aryl azides.

Reaction of ArNCO with syn-[MoO(mu-O)(S2CNR2)]2 or syn-[MoO(mu-NAr)(S2CNR2)]2 at 110 degrees C leads to the facile formation of bridging ureato complexes [Mo2(NAr)2(mu-NAr){mu-ArNC(O)NAr}(S2CNR2)2](Ar = Ph, p-tol; R = Me, Et, Pr), formed upon substitution of all oxo ligands and addition of a further equivalent of isocyanate across one of the bridging imido ligands. Related sulfido-bridged complexes [Mo2(NAr)2(mu-S){mu-ArNC(O)NAr}(S2CNR2)2] have been prepared from syn-[Mo2O2(mu-O)(mu-S)(S2CNR2)2]. When reactions with syn-[MoO(mu-NAr)(S2CNEt2)]2 were followed by NMR, intermediates were observed, being formulated as [Mo2O(NAr)(mu-NAr){mu-ArNC(O)NAr}(S2CNEt2)2], which at higher temperatures convert to the fully substituted products. A crystallographic study of [Mo2(N-p-tol)2(mu-S){mu-p-tolNC(O)N-p-tol}(S2CNPr2)2] reveals that the bridging ureato ligand is bound asymmetrically to the dimolybdenum centre-molybdenum-nitrogen bonds trans to the terminal imido ligands being significantly elongated with respect to those cis-a result of the trans-influence of the terminal imido ligands. This trans-influence also leads to a trans-effect, whereby the exchange of aryl isocyanates can occur in a regioselective manner. This is followed by NMR studies and confirmed by a crystallographic study of [Mo2(N-p-tol)2(mu-N-p-tol){mu-p-tolNC(O)NPh}(S2CNEt2)2]--the PhNCO occupying the site trans to the terminal imido ligands. Ureato complexes also react with PhNCS, initially forming [Mo2(NAr)2(mu-S){mu-ArNC(O)NAr}(S2CNR2)2], resulting from exchange of the bridging imido ligand for sulfur, together with small amounts of [Mo2(NAr)2(mu-S)(mu-S2)(S2CNEt2)2], containing bridging sulfide and disulfide ligands. The ureato complexes [Mo2(NAr)2(mu-S){mu-ArNC(O)NAr}(S2CNR2)2] react further with PhNCS to give [Mo2(NAr)2(mu-S)2(S2CNR2)2]n (n = 1, 2), which exist in a dimer-tetramer equilibrium. In order to confirm these results crystallographic studies have been carried out on [Mo2(N-p-tol)2(mu-S)(mu-S2)(S2CNEt2)2] and [Mo2(N-p-tol)2(mu-S)2(S2CNPr2)2]2.

The reaction of 2 equiv of MeMgCl with Tc{sub 2}(NAr){sub 4}({mu}-NAr){sub 2} (Ar = 2,6-dimethylphenyl) results in displacement of an imido ligand and the formation of TcMe{sub 2}(NAr)({mu}-NAr){sub 2}Tc(NAr){sub 2}. Treatment of TcMe{sub 2-}(NAr)({mu}-NAr){sub 2}Tc(NAr){sub 2}({mu}-NAr){sub 2}Me{sub 4}. Single crystal X-ray determinations of these complexes confirmed the unprecedented substitution of an imido ligand by two methyl groups.

Room temperature reaction of K2[Ru3(CO)11] with the molybdenum(VI) bis(imido) complexes Mo(NAr)2Cl2(dme) (Ar = C6H3X2-2,6; X = Me, Pri, Cl; dme = 1,2-dimethoxyethane) affords new high-low valent clusters Ru3(CO)12{Mo(NAr)2} which adopt a butterfly arrangement of metal centres with [Ru3(CO)12]2 acting as a ligand at a molybdenum(VI) centre.