The course of (R2R'SiO)3TaCl2 (R = tBu, R' = H, Me, Ph, tBu (silox); R = iPr, R' = tBu, iPr) reduction is dependent on siloxide size

Various sized siloxides (Cy(3)SiO > (t)Bu(3)SiO > (t)Bu(2)PhSiO > (t)Bu(2)MeSiO approximately (i)Pr(2)(t)BuSiO > (i)Pr(3)SiO > (t)Bu(2)HSiO) were used to make (R(2)R'SiO)(3)TaCl(2) (R = (t)Bu, R' = H (1-H), Me (1-Me), Ph (1-Ph), (t)Bu (1); R = (i)Pr, R' = (t)Bu (1-(i)Pr(2)); R = R' = (i)Pr (1-(i)Pr(3)); R = R' = (c)Hex (Cy)). Product analyses of sodium amalgam reductions of several dichlorides suggest that [(R(2)R'SiO)(3)Ta](2)(mu-Cl)(2) may be a common intermediate. When the siloxide is large (1-(t)Bu), formation of the Ta(III) species ((t)Bu(3)SiO)(3)Ta (6) occurs via disproportionation. When the siloxide is small, the Ta(IV) intermediate is stable (e.g., [((i)Pr(3)SiO)(3)Ta](2)(mu-Cl)(2) (2)), and when intermediate sized siloxides are used, solvent bond activation via unstable Ta(III) tris-siloxides is proposed to occur. Under hydrogen, reductions of 1-Me and 1-Ph provide Ta(IV) and Ta(V) hydrides [((t)Bu(2)MeSiO)(3)Ta](2)(micro-H)(2) (4-Me) and ((t)Bu(2)PhSiO)(3)TaH(2) (7-Ph), respectively.     

Über den Phosphandiyl‐Transfer von invers‐polarisierten Phosphaalkenen R1P=C(NMe2)2 (R1 = tBu,Cy, Ph,H) auf Phospheniumkomplexe [(η5‐C5H5)(CO)2M=P(R2)R3] (R2 = R3 = Ph; R2 = tBu,R3 = H; R2 = Ph,R3 = N(SiMe3)2)

Phosphanediyl Transfer from Inversely Polarized Phosphaalkenes R¹P=C(NMe₂)₂ (R¹ = tBu, Cy, Ph, H) onto Phosphenium Complexes [(η⁵‐C₅H₅)(CO)₂M=P(R²)R³] (R² = R³ = Ph; R² = tBu, R³ = H; R² = Ph, R³ = N(SiMe₃)₂) Reaction of the freshly prepared phosphenium tungsten complex [(η⁵‐C₅H₅)(CO)₂W=PPh₂] ( 3 ) with the inversely polarized phosphaalkenes RP=C(NMe₂)₂ ( 1 ) ( a : R = tBu; b : Cy; c : Ph) led to the η²‐diphosphanyl complexes ( 9a‐c ) which were isolated by column chromatography as yellow crystals in 24‐30 % yield. Similarly, phosphenium complexes [(η⁵‐C₅H₅)(CO)₂M=P(H)tBu] (M = W ( 6 ); Mo ( 8 )) were converted into (M = W ( 11 ); Mo ( 12 )) by the formal abstraction of the phosphanediyl [PtBu] from 1a . Treatment of [(η⁵‐C₅H₅)(CO)₂W=P(Ph)N(SiMe₃)₂] ( 4 ) with HP=C(NMe₂)₂ ( 1d ) gave rise to the formation of yellow crystalline ( 10 ). The products were characterized by elemental analyses and spectra (IR, ¹H, ¹³C‐, ³¹P‐NMR, MS). The molecular structure of compound 10 was elucidated by an X‐ray diffraction analysis.     

Thermally Stable Heterobinuclear Bivalent Group 14 Metal Complexes Ar2M−Sn[1,8-(NR)2C10H6] (M=Ge,Sn; Ar=2,6-(Me2N)2C6H3; R=CH2tBu)

The first thermally robust Ge ^II −Sn ^II compound 1 and the structurally characterized Sn^II-Sn^II analogue 2 , which maintain their structural integrity in solution, were obtained by treating MAr₂ (M=Ge, Sn; Ar=2,6-(Me₂N)₂C₆H₃) with Sn[1,8-(NR₂)₂C₁₀H₆] (R=CH₂tBu). On the basis of structural and spectroscopic data, the M−Sn bond is regarded as the interaction of a MAr₂ donor with an Sn[1,8-(NR₂)₂C₁₀H₆] acceptor.     

Conformational Rigidity in Complexes [MCl(tBu2PH)3] (M = Rh,Ir)

Reactions of [{M(μ‐Cl)(coe)₂}₂] (M = Rh, Ir; coe = cis‐cyclooctene) with the secondary phosphane tBu₂PH under various molar ratios were investigated. Probably, for kinetic reasons, the reaction behavior of the rhodium species differed from that of the iridium analogue in some instances. During these studies complexes [MCl(tBu₂PH)₃] [M = Rh ( 1 ), Ir ( 2 )] were isolated, and solution variable‐temperature ³¹P{¹H} NMR studies revealed that these complexes show a conformational rigidity on the NMR time scale. Spectra recorded in the temperature range from 173 to 373 K indicated in each case only one rotamer containing three chemically nonequivalent phosphanes due to the restricted rotation of these ligands about the M–P bonds and the tert‐butyl substituents around the P–C(tBu) bonds, respectively. Compound 1 showed in solution already at room temperature in several solvents a dissociation of a phosphane ligand affording the known complex [{Rh(μ‐Cl)(tBu₂PH)₂}₂] beside the free phosphane. In contrast to these findings, the iridium analogue 2 remained completely unchanged under similar conditions and exhibited, therefore, some kinetic inertness. For a better understanding of the NMR spectroscopic investigations, the molecular structure of 1 in the solid state was confirmed by X‐ray crystallography.     

Investigating CN- cleavage by three-coordinate M[N(R)Ar]3 complexes

Three-coordinate Mo[N((t)Bu)Ar]3 binds cyanide to form the intermediate [Ar((t)Bu)N]3Mo-CN-Mo[N((t)Bu)Ar]3 but, unlike its N2 analogue which spontaneously cleaves dinitrogen, the C-N bond remains intact. DFT calculations on the model [NH2]3Mo/CN- system show that while the overall reaction is significantly exothermic, the final cleavage step is endothermic by at least 90 kJ mol(-1), accounting for why C-N bond cleavage is not observed experimentally. The situation is improved for the [H2N]3W/CN- system where the intermediate and products are closer in energy but not enough for CN- cleavage to be facile at room temperature. Additional calculations were undertaken on the mixed-metal [H2N]3Re+/CN- /W[NH2]3 and [H2N]3Re+/CN-/Ta[NH2]3 systems in which the metals ions were chosen to maximise the stability of the products on the basis of an earlier bond energy study. Although the reaction energetics for the [H2N]3Re+/CN /W[NH2]3 system are more favourable than those for the [H2N]3W/CN- system, the final C-N cleavage step is still endothermic by 32 kJ mol(-1) when symmetry constraints are relaxed. The resistance of these systems to C-N cleavage was examined by a bond decomposition analysis of [H2N]M-L1[triple bond]L2-M[NH2]3 intermediates for L1[triple bond]L2 = N2, CO and CN which showed that backbonding from the metal into the L1[triple bond]L2 pi* orbitals is significantly less for CN than for N2 or CO due to the negative charge on CN- which results in a large energy gap between the metal d(pi), and the pi* orbitals of CN-. This, combined with the very strong M-CN- interaction which stabilises the CN intermediate, makes C-N bond cleavage in these systems unfavourable even though the C[triple bond]N triple bond is not as strong as the bond in N2 or CO.     

链状三核异金属簇阴离子［Cl_2FeS_2M＇（PPh_3）_2］~－（M＝Mo

在５５０～９０ｃｍ~（－１）波数范围内，测量簇阴离子［Ｃｌ_２ＦｅＳ_２ＭＳ_２Ｍ′（ＰＰｈ_３）_２］~－（Ｍ＝Ｍｏ，Ｍ′＝Ａｇ；Ｍ＝Ｗ，Ｍ′＝Ｃｕ，Ａｇ）的付里叶变换红外光谱，并对标题簇阴离子［Ｃｌ_２ＦｅＳ_２ＷＳ_２Ｃｕ（ＰＰｈ_３）_２］~－，［Ｃｌ_２ＦｅＳ_２ＭｏＳ_２Ａｇ（ＰＰｈ_３）_２］~－和［Ｃｌ_２ＦｅＳ_２ＷＳ_２Ａｇ（ＰＰｈ_３）_２］~－骨架的振动光谱给予经验指认。同时采用＂诱导自洽方法计算振动力常数＂程序，对簇骨架［Ｃｌ_２ＦｅＳ_２ＭＳ_２Ｍ~′Ｐ_２］进行简正坐标分析。振动频率的计算值与观测值符合良好，两者平均偏差小于１．０％，计算结果支持了振动谱带的归属并表明计算力常数的合理性。文中还讨论了主要价键振动频率的变化规律。     

Carbon-carbon bond activation of R-CN (R = Me, Ar, iPr, tBu) using a cationic Rh(III) complex

Addition of 1.0 equiv of Ph3SiH to [Cp*(PMe3)Rh(Me)(CH2Cl2)]+BAr'4- (1) resulted in release of methane and quantitative formation of [Cp*(PMe3)Rh(SiPh3)(CH2Cl2)]+BAr'4- (2). Subsequent addition of 1.0 equiv of MeCN to 2 caused immediate displacement of dichloromethane to form the eta1-nitrile adduct [Cp*(PMe3)Rh(SiPh3)(NCMe)]+BAr'4- (3). Upon standing at room-temperature overnight, complex 3 converted quantitatively to another product which has been characterized as the C-C activation product, [Cp*(PMe3)Rh(Me)(CNSiPh3)]+BAr'4- (5). Addition of other nitrile substrates (R-CN, R = Ph, (4-CF3)Ph, (4-MeO)Ph, iPr, tBu) to 2 also resulted in C-C activation of the R-CN bond to form [Cp*(PMe3)Rh(R)(CNSiPh3)]+BAr'4-. Evidence for an eta2-iminoacyl intermediate complex, [Cp*(PMe3)Rh(eta2-C(R)=N(SiPh3)]+BAr'4-, is also presented.     

Triarylantimony Dicaroxylates Ar3Sb[OC(O)R]2 (Ar = Ph,p-Tol; R = 2-C4H3O, 3-C5H4N): Synthesis and Structure

Bis(2-furoinate)triphenyl- and tri-p-tolylantimony and bis(3-niacinate)triphenylanitmony were synthesized by reacting triarylantimony (Ar₃Sb; Ar = Ph, p-Tol) with 2-furancarboxylic and 3-pyridinecarboxylic acids in the presence of hydrogen peroxide. According to X-ray diffraction data, Sb atoms have trigonal bipyramidal coordination polyhedra. The Sb–O distances are 2.117(4), 2.137(4) Å; 2.136(2), 2.158(2) Å, and 2.112(1), 2.101(2) Å, the Sb···O distances are 2.866(4), 2.798(4) Å; 2.816(2), 2.774(2) Å, and 3.054(2), 3.168(2) Å, respectively.     

Reactivity of the inversely polarized phosphaalkenes RP=C(NMe2)2 (R = tBu, Me3Si, H) towards arylcarbene complexes [(CO)5M=C(oEt)Ar] (Ar= Ph, M = Cr, W; Ar = 2-MeC6H4, 2-MeOC6H4, M = W)

The reaction of the arylated Fischer carbene complexes [(CO)5M=C(OEt)Ar] (Ar=Ph; M = Cr, W; 2-MeC6H4; 2-MeOC6H; M = W) with the phosphaalkenes RP=C(NMe2), (R=tBu, SiMe3) afforded the novel phosphaalkene complexes [[RP=C(OEt)Ar]M(CO)5] in addition to the compounds [(RP=C(NMe2)2]M(CO)5]. Only in the case of the R = SiMe3 (E/Z) mixtures of the metathesis products were obtained. The bis(dimethylamino)methylene unit of the phosphaalkene precursor was incorporated in olefins of the type (Me2N)2C=C(OEt)(Ar). Treatment of [(CO)5W=C(OEt)(2-MeOC6H4)] with HP=C(NMe2)2 gave rise to the formation of an E/Z mixture of [[(Me2N)2CH-P=C(OEt)(2-MeOC6H4)]W(CO)5] the organophosphorus ligand of which formally results from a combination of the carbene ligand and the phosphanediyl [P-CH(NMe2)2]. The reactions reported here strongly depend on an inverse distribution of alpha-electron density in the phosphaalkene precursors (Pdelta Cdelta+), which renders these molecules powerfu] nucleophiles.     

Investigation of the microstructure of poly(propylene) in dependence of the polymerization temperature for the systems iPr[3‐RCpFlu]ZrCl2/MAO,with R = H,Me, Et,iPr, tBu,and iPr[IndFlu]ZrCl2/MAO

With six different metallocenes, namely ⁱPr[CpFlu]ZrCl₂ I , ⁱPr[3‐MeCpFlu]ZrCl₂ II , ⁱPr[3‐EtCpFlu]ZrCl₂ III , ⁱPr[3‐ⁱPrCpFlu]ZrCl₂ IV , ⁱPr[IndFlu]ZrCl₂ V and ⁱPr[3‐^tBuCpFlu]ZrCl₂ VI propene polymerizations were carried out at different polymerization temperatures. MAO was used as a cocatalyst for all polymerizations. In case of metallocenes II, III and IV an increase in isotacticity with increasing polymerization temperature was observed. This is due to the increased rotation and, as a consequence, to the increased steric demand of the substituent at the cyclopentadienyl residue. With metallocene V a catalyst of in principle the same type was synthesized, but rotation of the substituent is not possible. Here, in the contrary, the assumed effect was observed, that the stereospecificity of the metallocene decreases, while raising the polymerization temperature. In metallocene I there is no rotatory substituent at the cyclopentadienyl residue and therefore a more stereoirregular polymer is formed at higher polymerization temperatures. Metallocene VI produces poly(propylene) with slightly increased isotacticity at higher polymerization temperature.     

Cu-[M’]MOR和Ag-[M’]MOR (M’=B,Al, Ga,Fe)的酸性

采用Dmol3程序中基于密度泛函理论(DFT)的广义梯度方法(GGA)和BLYP方法以及DND基组, 研究了丝光沸石H-[M']MOR、Cu-[M']MOR和Ag-[M']MOR(M'=B, Al, Ga, Fe)结构及其对NH3分子的吸附, 获得了吸附平衡构型和吸附能. NH3分子在H-[M']MOR中的吸附主要是通过NH3分子中氮原子上的孤对电子与质子酸位作用, NH3分子在H-[Al]MOR、H-[Ga]MOR和H-[Fe]MOR上发生化学吸附, 而在H-[B]MOR上发生物理吸附, 这与文献结果相符. NH3分子与Cu-[M']MOR 和Ag-[M']MOR分子筛之间主要通过氮上的孤对电子和平衡离子(Cu+和Ag+)的s空轨道间配位作用而发生化学吸附. 吸附能数据表明, 在H-[M']MOR、Cu-[M']MOR 和Ag-[M']MOR中, A1原子进入骨架导致H-[A1]MOR、Cu-[A1]MOR和Ag-[A1]MOR的酸强度最强; 对于同一种原子取代的丝光沸石, 其酸强度次序为: Cu-[M']MOR > Ag-[M']MOR > H-[M']MOR. 此外, 还对吸附前后的沸石中平衡离子(H+、Cu+和Ag+)及NH3分子的Mulliken电荷集居数作了研究和分析.     

Robust, alkali-stable, triscarbonyl metal derivatives of hexametalate anions, [M6O19[M'(CO)3]n](8-n)- (M = Nb, Ta; M' =Mn, Re; n = 1, 2)

Ten 1:1 and 2:1 complexes of [Mn(CO)(3)](+) and [Re(CO)(3)](+) with [Nb(6)O(19)](8)(-) and [Ta(6)O(19)](8)(-) have been isolated as potassium salts in good yields and characterized by elemental analysis, (17)O NMR and infrared spectroscopy, and single-crystal X-ray structure determinations. Crystal data for 1 (t-Re(2)Ta(6)): empirical formula, K(4)Na(2)Re(2)C(6)Ta(6)O(35)H(20), monoclinic, space group, C2/m, a = 17.648(3) A, b = 10.056(1) A, c = 13.171(2) A, beta = 112.531(2) degrees, Z = 2. 2 (t-Re(2)Nb(6)): empirical formula, K(6)Re(2)C(6)Nb(6)O(38)H(26), monoclinic, space group, C2/m, a = 17.724(1) A, b = 10.0664(6) A, c = 13.1965(7) A, beta = 112.067(1) degrees, Z = 2. 3 (t-Mn(2)Nb(6)): empirical formula, K(6)Mn(2)C(6)Nb(6)O(37)H(24), monoclinic, space group, C2/m, a = 17.812(2) A, b = 10.098(1) A, c = 13.109(2) A, beta = 112.733(2) degrees, Z = 2. 4 (c-Mn(2)Nb(6)): empirical formula, K(6)Mn(2)C(6)Nb(6)O(50)H(50), triclinic, space group, P1, a = 10.2617(6) A, b = 13.4198(8) A, c = 21.411(1) A, alpha = 72.738(1) degrees, beta = 112.067(1) degrees, gamma = 83.501(1) degrees, Z = 2. 5 (c-Re(2)Nb(6)): empirical formula, K(6)Re(2)C(6)Nb(6)O(54)H(58), monoclinic, space group, P2(1)/c, a = 21.687(2) A, b = 10.3085(9) A, c = 26.780(2) A, beta = 108.787(1) degrees, Z = 4. The complexes contain M(CO)(3) groups attached to the surface bridging oxygen atoms of the hexametalate anions to yield structures of nominal C(3)(v)() (1:1), D(3)(d)() (trans 2:1), and C(2)(v)() (cis 2:1) symmetry. The syntheses are carried out in aqueous solution or by aqueous hydrothermal methods, and the complexes have remarkably high thermal, redox, and hydrolytic stabilities. The Re-containing compounds are stable to 400-450 degrees C, at which point CO loss occurs. The Mn compounds lose CO at temperatures above 200 degrees C. Cyclic voltammetry of all complexes in 0.1 M sodium acetate show no redox behavior, except an irreversible oxidation process at approximately 1.0 V vs. Ag/AgCl. In contrast to the parent hexametalate anions that are stable only in alkaline (pH >10) solution, the new complexes are stable, at least kinetically, between pH 4 and pEta approximately 12.     

Phosphinophosphiniden-Phosphorane tBu2P?P = P(R)tBu2 aus Li(THF)2[η2-(tBu2P)2P] und Alkylhalogeniden

The Phosphinophosphinidene-phosphoranes ^tBu₂P? P = P(R)^tBu₂ from Li(THF)₂[η²-(^tBu₂P)₂P] and Alkyl Halides We report the formation of ^tBu₂P? P = P(R)^tBu₂ a and (^tBu₂)₂PR b (with R = Me, Et, ⁿPr, ⁱPr, ⁿBu, PhCH₂, H₂C = CH? CH₂ and CF₃) reactions of Li(THF)₂[η²-(^tBu₂P)₂P] 2 with MeCl, MeI, EtCl, EtBr, ⁿPrCl, ⁿPrBr, ⁱPrCl, ⁿBuBr, PhCH₂Cl, H₂C = CH? CH₂Cl or CF₃Br. In THF solutions the ylidic compounds a predominate, whereas in pentane the corresponding triphosphanes b are preferrably formed. With ClCH₂? CH = CH₂ only b is produced; CF₃Br however yields both ^tBu₂P? P = P(Br)^tBu₂ and ^tBu₂P? P = P(CF₃)^tBu₂, but no b . The ratio of a:b is influenced by the reaction temperature, too. The compounds ^tBu₂P? P = P(Et)^tBu₂ 4a and (^tBu₂P)₂PEt 4 b , e. g., are produced in a ratio of 4:3 at ?70°C in THF, and 1:1 at 20°C; whereas 1:1 is obtained at ?70°C in pentane, and 1:2 at 20°C. Neither ^tBuCl nor H₂C = CHCl react with 2 . The compounds a decompose thermally or under UV irradiation forming ^tBu₂PR and the cyclophosphanes (^tBu₂P)_nP_n.     

Optimizing small molecule activation and cleavage in three-coordinate M[N(R)Ar]3 complexes

The sterically hindered, three-coordinate metal systems M[N(R)Ar]3 (R = tBu, iPr; Ar = 3,5-C6H3Me2) are known to bind and activate a number of fundamental diatomic molecules via a [Ar(R)N]3M-L-L-M[N(R)Ar]3 dimer intermediate. To predict which metals are most suitable for activating and cleaving small molecules such as N(2), NO, CO, and CN(-), the M-L bond energies in the L-M(NH2)3 (L = O, N, C) model complexes were calculated for a wide range of metals, oxidation states, and dn (n = 2-6) configurations. The strongest M-O, M-N, and M-C bonds occurred for the d2, d3, and d4 metals, respectively, and for these d(n) configurations, the M-C and M-O bonds were calculated to be stronger than the M-N bonds. For isoelectronic metals, the bond strengths were found to increase both down a group and to the left of a period. Both the calculated N-N bond lengths and activation barriers for N2 bond cleavage in the (H2N)3M-N-N-M(NH2)3 intermediate dimers were shown to follow the trends in the M-N bond energies. The three-coordinate complexes of Ta(II), W(III), and Nb(II) are predicted to deliver more favorable N2 cleavage reactions than the experimentally known Mo(III) system and the Re(III)Ta(III) dimer, [Ar(R)N]3Re-CO-Ta[N(R)Ar]3, is thermodynamically best suited for cleaving CO.     

Bonding analysis of metal-metal multiple bonds in R3M-M'R3 (M, M' = Cr, Mo, W; R = Cl, NMe2)

The bonding situation of homonuclear and heteronuclear metal-metal multiple bonds in R(3)M-M'R(3) (M, M' = Cr, Mo, W; R = Cl, NMe(2)) is investigated by density functional theory (DFT) calculations, with the help of energy decomposition analysis (EDA). The M-M' bond strength increases as M and M' become heavier. The strongest bond is predicted for the 5d-5d tungsten complexes (NMe(2))(3)W-W(NMe(2))(3) (D(e) = 103.6 kcal/mol) and Cl(3)W-WCl(3) (D(e) = 99.8 kcal/mol). Although the heteronuclear molecules with polar M-M' bonds are not known experimentally, the predicted bond dissociation energies of up to 94.1 kcal/mol for (NMe(2))(3)Mo-W(NMe(2))(3) indicate that they are stable enough to be isolated in the condensed phase. The results of the EDA show that the stronger R(3)M-M'R(3) bonds for heavier metal atoms can be ascribed to the larger electrostatic interaction caused by effective attraction between the expanding valence orbitals in one metal atom and the more positively charged nucleus in the other metal atom. The orbital interaction reveal that the covalency of the homonuclear and heteronuclear R(3)M-M'R(3) bonds is due to genuine triple bonds with one σ- and one degenerate π-symmetric component. The metal-metal bonds may be classified as triple bonds where π-bonding is much stronger than σ-bonding; however, the largest attraction comes from the quasiclassical contribution to the metal-metal bonding. The heterodimetallic species show only moderate polarity and their properties and stabilities are intermediate between the corresponding homodimetallic species, a fact which should allow for the experimental isolation of heterodinuclear species. CASPT2 calculations of Cl(3)M-MCl(3) (M = Cr, Mo, W) support the assignment of the molecules as triply bonded systems.     

Reactions of Lithium Salts of Triphosphanes tBu2P–PLi–PtBu2 and tBu2P–PLi–P(NEt2)2 with Metal Complexes [(R3P)2MCl2] (M = Ni,Pd, Pt,R3P = Et3P,pTol3P,Ph2EtP,iPr3P)

tBu₂P–PLi–PtBu₂ · 2THF reacts with [(R₃P)₂MCl₂] (M = Pt, Pd, Ni; R₃P = Et₃P, pTol₃P, Ph₂EtP, iPr₃P) to yield isomers of [(1,2‐η‐tBu₂P=P–PtBu₂)M(PR₃)Cl], in which the tBu₂P–P–PtBu₂ ligand adopts the arrangement of a side‐on bonded 1,1‐di‐tert‐butyl‐2‐(di‐tert‐butylphosphanyl)diphosphenium cation. tBu₂P–PLi–P(NEt₂)₂ · 2THF reacts with [(R₃P)₂MCl₂] but does not form complexes with a tBu₂P–P–P(NEt₂)₂ moiety, however, splitting of a P–P(NEt₂)₂ bond of the parent triphosphane takes place.     

Experimental and theoretical comparison of actinide and lanthanide bonding in M[N(EPR(2))(2)](3) complexes (M = U, Pu, La, Ce; E = S, Se, Te; R = Ph, iPr, H)

Treatment of M[N(SiMe3)2]3 (M = U, Pu (An); La, Ce (Ln)) with NH(EPPh2)2 and NH(EPiPr2)2 (E = S, Se), afforded the neutral complexes M[N(EPR2)2]3 (R = Ph, iPr). Tellurium donor complexes were synthesized by treatment of MI3(sol)4 (M = U, Pu; sol = py and M = La, Ce; sol = thf) with Na(tmeda)[N(TePiPr2)2]. The complexes have been structurally and spectroscopically characterized with concomitant computational modeling through density functional theory (DFT) calculations. The An-E bond lengths are shorter than the Ln-E bond lengths for metal ions of similar ionic radii, consistent with an increase in covalent interactions in the actinide bonding relative to the lanthanide bonding. In addition, the magnitude of the differences in the bonding is slightly greater with increasing softness of the chalcogen donor atom. The DFT calculations for the model systems correlate well with experimentally determined metrical parameters. They indicate that the enhanced covalency in the M-E bond as group 16 is descended arises mostly from increased metal d-orbital participation. Conversely, an increase in f-orbital participation is responsible for the enhancement of covalency in An-E bonds compared to Ln-E bonds. The fundamental and practical importance of such studies of the role of the valence d and f orbitals in the bonding of the f elements is emphasized.