Unusual cationic tris(dimethylsulfide)-substituted closo-boranes: preparation and characterization of [1,7,9-(Me2S)3-B12H9] BF4 and [1,2,10-(Me2S)3-B10H7] BF4.

Rational syntheses of trisubstituted sulfur-bearing closo-boranes are presented. In the development of these syntheses unusual cationic closo-boranes [1,7,9-(Me(2)S)(3)-B(12)H(9)](+) (3) and [1,2,10-(Me(2)S)(3)-B(10)H(7)](+) (4) have been identified. These were initially recognized to be intermediates in the formation of the neutral trisubstituted species 1,7-(Me(2)S)(2)-9-(MeS)-B(12)H(9) (1) and 1,10-(Me(2)S)(2)-2-(MeS)-B(10)H(7) (2), respectively. Stable tetrafluoroborate salts were prepared and isolated, and their structures are presented. They are believed to represent the first structural determinations of cationic borane clusters of any type.

Ammonium octahydrotriborate (NH4B3H8): new synthesis, structure, and hydrolytic hydrogen release.

A metathesis reaction between unsolvated NaB(3)H(8) and NH(4)Cl provides a simple and high-yield synthesis of NH(4)B(3)H(8). Structure determination through X-ray single crystal diffraction analysis reveals weak N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8) and strong N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8)·18-crown-6·THF adduct. Pyrolysis of NH(4)B(3)H(8) leads to the formation of hydrogen gas with appreciable amounts of other volatile boranes below 160 °C. Hydrolysis experiments show that upon addition of catalysts, NH(4)B(3)H(8) releases up to 7.5 materials wt % hydrogen.

Intermolecular dihydrogen- and hydrogen-bonding interactions in diammonium closo-decahydrodecaborate sesquihydrate.

The asymmetric unit of the title salt, 2NH(4)(+).B(10)H(10)(2-).1.5H(2)O or (NH(4))(2)B(10)H(10).1.5H(2)O, (I), contains two B(10)H(10)(2-) anions, four NH(4)(+) cations and three water molecules. (I) was converted to the anhydrous compound (NH(4))(2)B(10)H(10), (II), by heating to 343 K and its X-ray powder pattern was obtained. The extended structure of (I) shows two types of hydrogen-bonding interactions (N-H...O and O-H...O) and two types of dihydrogen-bonding interactions (N-H...H-B and O-H...H-B). The N-H...H-B dihydrogen bonding forms a two-dimensional sheet structure, and hydrogen bonding (N-H...O and O-H...O) and O-H...H-B dihydrogen bonding link the respective sheets to form a three-dimensional polymeric network structure. Compound (II) has been shown to form a polymer with the accompanying loss of H(2) at a faster rate than (NH(4))(2)B(12)H(12) and we believe that this is due to the stronger dihydrogen-bonding interactions shown in the hydrate (I).

Synthesis and characterization of homopolymers and copolymers containing closo-[B(12)H(12)](2-) boron cage derivatives.

Chains of cages: Neutral/ionic [B(12)H(12)](2-) boron-cage-functionalized methacrylate and styrene homopolymers or copolymers (see picture) are non-crystalline solids, T(g) increases as the number of B(12) cages in the chain of polystyrene increases, and homopolymers retain more weight than the copolymers when heated to 400 degrees C.New [B(12)H(12)](2-) boron cage functionalized neutral and ionic methacrylate and styrene monomers (1, 2, 3) were synthesized and these monomers were used to prepare homopolymers (4, 5, 6) and copolymers with methylmethacrylate (MMA) (7, 8), 2-hydroxyethylmethacrylate (HEMA) (11, 12, 13, 17), 2-hydroxyethylacrylate (HEA) (14, 15, 18), acrylamide (AA) (16), and styrene (9, 10, 19) with different monomer ratios. Free-radical initiated bulk and solution polymerization methods were used to synthesize these polymers and they were characterized by (1)H NMR, (11)B NMR, and IR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). Generally, the polymers show broad (1)H NMR and (11)B NMR peaks compared to their respective monomers. The copolymers have high molecular weights with higher [B(12)H(12)](2-) boron cage mole ratios. All the polymers on which DSC experiments were conducted (4 b, 5 b, 6 b, 7, 8, 9, 10, 17, 18, and 19) are non-glassy amorphous solids, except styrene copolymers (9, 19) and homopolymer (6 b) which show T(g) values of 100, 117, and 162 degrees C, respectively. Copolymers 9 and 10 have higher thermal stability (320 degrees C) than polymers 5 b, 4 b, and 8, which are stable up to 244, 250, and 260 degrees C, respectively. The homopolymers retained more weight than the copolymers when they were heated to 400 degrees C.

Water-free rare earth-Prussian blue type analogues: synthesis, structure, computational analysis, and magnetic data of {Ln(III)(DMF)(6)Fe(III)(CN)(6)}(infinity) (Ln = rare earths excluding Pm).

Water-free rare earth(III) hexacyanoferrate(III) complexes, {Ln(DMF)(6)(mu-CN)(2)Fe(CN)(4)}(infinity) (DMF = N,N-dimethylformamide; Ln = Sm, 1; Eu, 2; Gd, 3; Tb, 4; Dy, 5; Ho, 6; Er, 7; Tm, 8; Yb, 9; Lu, 10; Y, 11; La, 12; Ce, 13; Pr, 14; Nd, 15), were synthesized in dry DMF through the metathesis reactions of [(18-crown-6)K](3)Fe(CN)(6) with LnX(3)(DMF)(n) (X = Cl or NO(3)). Anhydrous DMF solutions of LnX(3)(DMF)(n) were prepared at room temperature from LnCl(3) or LnX(3).nH(2)O under a dynamic vacuum. All compounds were characterized by IR, X-ray powder diffraction (except for 10), and single crystal X-ray diffraction (except for 2, 7, 10). Infrared spectra reveal that a monotonic, linear relationship exists between the ionic radius of the lanthanide and the nu(mu-CN) stretching frequency of 1-10, 12-15 while 11 deviates slightly from the ionic radius relationship. X-ray powder diffraction data are in agreement with powder patterns calculated from single crystal X-ray diffraction results, a useful alternative for bulk sample confirmation when elemental analysis data are difficult to obtain. Eight-coordinate Ln(III) metal centers are observed for all structures. trans-cyanide units of [Fe(CN)(6)](3-) formed isocyanide linkages to Ln(III) resulting in one-dimensional polymeric chains. Structures of compounds 1-9 and 11 are isomorphous, crystallizing in the space group C2/c. Structures of compounds 12-15 are also isomorphous, crystallizing in the space group P2/n. One unique polymeric chain exists in the structures of 1-9 and 11 while two unique polymeric chains exist in structures of 12-15. One of the polymeric chains of 12-15 is similar to that observed for 1-9, 11 while the other is more distorted and has a shorter Ln-Fe distance. Magnetic susceptibility measurements for compounds 3-6, 8, 11 were performed on polycrystalline samples of the compounds.

Cyclic Hydroborate Complexes of Metallocenes II: Reactivity of (&mgr;-H)(2)(BC(5)H(10))(2) and Its Cyclic Derivative, [H(2)BC(5)H(10)](-); Synthesis of (eta(5)-C(5)H(5))(2)MCl(&mgr;-H)(2)BC(5)H(10) (M = Zr, Hf).

Reactions of the organodiborane (&mgr;-H)(2)(BC(5)H(10))(2), 1, with the Lewis bases, N(CH(3))(3), P(CH(3))(3), NH(3), and H(-), produced the cyclic adducts LHBC(5)H(10) (L = N(CH(3))(3), P(CH(3))(3), NH(3), H(-)) through symmetrical cleavage of the hydrogen bridge system. The salt [(NH(3))(2)BC(5)H(10)][H(2)BC(5)H(10)] was produced through unsymmetrical cleavage of the hydrogen bridge system. An improved, synthesis of the anion [H(2)BC(5)H(10)](-), 3, is described. It can function as a hydride transfer reducing agent in its reactions with BH(3)THF and 4-tert-butylcyclohexanone. In its reactions with (eta(5)-C(5)H(5))(2)MCl(2) it serves as a chelating agent to produce (eta(5)-C(5)H(5))(2)MCl(&mgr;-H)(2)BC(5)H(10) (M = Zr, 4; Hf, 5). The molecular structures of 1 and 4 are reported here. Crystal data for 1: space group P&onemacr;, a = 6.415(3) Å, b = 9.260(4) Å, c =10.291(5) Å, alpha = 114.53(4) degrees, beta = 104.25(4) degrees, gamma = 90.01(4) degrees, Z = 2. Crystal data for 4: space group P2(1)/c, a = 12.584(2) Å, b = 9.511(1) Å, c = 12.813(2) Å, beta = 100.26(1) degrees, Z = 4.

Heterometallic One-Dimensional Arrays Containing Cyanide-Bridged Lanthanide(III) and Transition Metals.

One-dimensional arrays having the general formula {(DMF)(10)Ln(2)[M(CN)(4)](3)}(infinity) [Ln = Sm, Eu, Er, Yb and M = Ni, Pd, Pt] were prepared from the reactions of 2:3 molar ratios of LnCl(3) with K(2)[M(CN)(4)] in DMF (DMF = N,N-dimethylformamide). Under similar conditions using 1:1 molar ratios of SmCl(3) and K(2)[Ni(CN)(4)] in DMF or YbCl(3) and K(2)[Ni(CN)(4)] in DMA (DMA = N,N-dimethylacetamide), the one-dimensional arrays {(DMF)(5)Sm[Ni(CN)(4)]Cl}(infinity), 8, and {(DMA)(4)Yb[Ni(CN)(4)]Cl}(infinity), 9, were prepared. An earlier study of {(DMF)(10)Yb[Ni(CN)(4)](3)}(infinity), 3, and {(DMF)(10)Yb(2)[Pt(CN)(4)](3)}(infinity), 7, showed that two different yet related one-dimensional arrays can be adopted. In the present study, X-ray crystal structures of {(DMF)(10)Sm(2)[Ni(CN)(4)](3)}(infinity), 1, and {(DMF)(10)Er(2)[Ni(CN)(4)](3)}(infinity), 2, are shown to be isomorphous with {(DMF)(10)Yb(2)[Ni(CN)(4)](3)}(infinity), 3, while {(DMF)(10)Sm(2)[Pd(CN)(4)](3)}(infinity), 4, {(DMF)(10)Eu(2)[Pd(CN)(4)](3)}(infinity), 5, and {(DMF)(10)Yb(2)[Pd(CN)(4)](3)}(infinity), 6, are isomorphous with {(DMF)(10)Yb(2)[Pt(CN)(4)](3)}(infinity), 7. Single-crystal X-ray crystal structure determinations reveal that arrays 1, 2, and 3 consist of cyanide-bridged "diamond"-shaped Ln(2)Ni(2) metal cores. These metal cores are linked together in an infinite array through cyanide bridges by [Ni(CN)(4)](2)(-) anions generating a single-strand chain. Crystal data for 1: triclinic space group P&onemacr;, a = 10.442(5) Å, b = 10.923(2) Å, c = 15.168(3) Å, alpha = 74.02(2) degrees, beta = 83.81(3) degrees, gamma = 82.91(2) degrees, Z = 2. Crystal data for 2: triclinic space group P&onemacr;, a = 10.172(1) Å, b = 11.111(3) Å, c = 15.369(2) Å, alpha = 73.17(2) degrees, beta = 85.15(1) degrees, gamma = 83.48(2) degrees, Z = 2. Arrays 4, 5, 6, and 7 consist of two parallel zigzag chains that are linked together through bridging [M(CN)(4)](2)(-) anions. Crystal data for 4: triclinic space group P&onemacr;, a = 9.304(2) Å, b = 11.351(3) Å, c = 16.257(5) Å, alpha = 81.62(2) degrees, beta = 77.51(2) degrees, gamma = 82.47(2) degrees, Z = 2. Crystal data for 5: triclinic space group P&onemacr;, a = 9.300(3) Å, b = 11.353(4) Å, c = 16.279(3) Å, alpha = 81.58(2) degrees, beta = 77.37(2) degrees, gamma = 81.58(2) degrees, Z = 2. Crystal data for 6: triclinic space group P&onemacr;, a = 9.164(2) Å, b = 11.718(3) Å, c = 16.122(3) Å, alpha = 79.88(2) degrees, beta = 74.43(2) degrees, gamma = 80.50(2) degrees, Z = 2. Electrical conductance, NMR, and infrared studies of DMF solutions of 1-7 reveal that these arrays are partially ionized in solution. Single-crystal X-ray analyses of the one-dimensional arrays 8 and 9 show that these complexes adopt the commonly observed zigzag chain structure. Crystal data for 8: monoclinic space group P2(1)/n, a =7.783(2) Å, b = 17.748(8) Å, c = 21.236(5) Å, beta = 92.87(2) degrees, Z = 4. Crystal data for 9: monoclinic space group P2(1)/n, a = 10.022(2) Å, b = 19.505(4) Å, c = 15.742(3) Å, beta = 105.94(2) degrees, Z = 4. Studies of 8 and 9 in DMF and DMA, respectively, indicate that 8 is partially ionized and 9 is almost completely ionized.

Cyclic Hydroborate Complexes of Metallocenes. IV. Weak Unsupported Single Hydrogen Bridges in Cp(2)Zr{(&mgr;-H)B(X)CH(2)Ph}{(&mgr;-H)(2)BX} (X = C(5)H(10), C(4)H(8)).

The compounds Cp(2)Zr{(&mgr;-H)(BC(5)H(10))CH(2)Ph}{(&mgr;-H)(2)BC(5)H(10)}, 1, and Cp(2)Zr{(&mgr;-H)(BC(4)H(8))CH(2)Ph}{(&mgr;-H)(2)BC(4)H(8)}, 2, were prepared in yields of 59% and 51%, respectively, from the reactions of Cp(2)ZrCl{(&mgr;-H)(2)BX} (X = C(5)H(10), C(4)H(8)) with PhCH(2)MgCl. Single-crystal X-ray diffraction analyses indicate the presence of an unsupported Zr-H-B bond in these complexes. In solution at low temperature (1)H NMR spectra are consistent with the presence of the unsupported Zr-H-B bridge in complexes 1 and 2. However, NMR spectra at room temperature indicate that the hydrogen bridge is dissociated into Cp(2)ZrH{(&mgr;-H)(2)BC(5)H(10)} and B(C(5)H(10))CH(2)Ph in the case of complex 1, and Cp(2)ZrH{(&mgr;-H)(2)BC(4)H(8)} and B(C(4)H(8))CH(2)Ph in the case of complex 2. It is possible to pump away the B(C(4)H(8))CH(2)Ph from solid 2 at room temperature, leaving behind Cp(2)ZrH{(&mgr;-H)(2)BC(4)H(8)}. These results suggest that the Zr-H bond acts as an electron pair donor to trivalent boron in the formation of 1and 2. Crystal data for Cp(2)Zr{(&mgr;-H)(BC(5)H(10))CH(2)Ph}{(&mgr;-H)(2)BC(5)H(10)}: monoclinic, P2(1)/m (No. 11), a = 9.392(5) Å, b = 13.250(4) Å, c = 9.841(6) Å, beta = 95.70(4) degrees, Z = 2. Crystal data for Cp(2)Zr{(&mgr;-H)(BC(4)H(8))CH(2)Ph}{(&mgr;-H)(2)BC(4)H(8)}: orthorhombic, Pbca (No. 61), a = 18.1630(10) Å, b = 19.0497(10) Å, c = 13.0393(10) Å, Z = 8.

Two Novel Lithium-15-Crown-5 Complexes: An Extended LiCl Chain Stabilized by Crown Ether and a Dimeric Complex Stabilized by Hydrogen Bonding with Water.

Two lithium chloride-15C5 (15C5 = 15-crown-5) complexes, [Li(15C5)(&mgr;-Cl)(2)Li](infinity), 1, and {[Li(15C5)(H(2)O)]Cl}(2), 2, were synthesized. Their structures, characterized by single-crystal X-ray diffraction analyses, are dictated by the absence of or presence of water. Complex 1, prepared in an anhydrous environment, is the first example of an extended LiCl chain structure. It contains repeating units Li(&mgr;-Cl)Li(15C5) that are connected by additional bridging Cl atoms. One Li has close contacts with one Cl and all five O atoms of 15C5 and the other Li with three Cl and one O of 15C5. However, the chain structure cannot form in the presence of water. Instead dimeric complex 2 was formed when LiCl.xH(2)O (x = 1.14) was the starting material. In this case H(2)O is coordinated to lithium through a Li-O linkage and is hydrogen bonded to Cl(-) (H.Cl). The Li(+) cation is coordinated to the five O atoms of 15C5 as well as the O atom from H(2)O, and the Cl(-) counteranion is isolated from Li(+) by two hydrogen bonds with one H atom each from two H(2)O molecules with H.Cl distances of 2.30(4) and 2.35(4) Å, respectively. A crystallographically imposed center of symmetry generates a dimer that resembles a 2:2 anion-paired encapsulate. Crystal data for 1: space group Pna2(1) (no. 33), a = 14.974(1) Å, b = 13.553(1) Å, c = 7.160(1) Å, V = 1453.0(2) Å(3), Z = 4. Crystal data for 2: space group P2(1)/n (no. 14), a = 10.353(1) Å, b = 7.9070(1) Å, c = 17.741 Å, beta = 100.50(1) degrees, V = 1427.9(2) Å(3), Z = 4.

Lanthanide-transition metal carbonyl complexes: condensation of solvent-separated ion-pair compounds into extended structures.

New solvent-separated ion-pair compounds and extended structures containing ytterbium(II)-transition metal isocarbonyl linkages were synthesized. [Yb(THF)6][M(CO)5]2 (1, M = Mn; 2, M = Re) were prepared via transmetalation reactions between Yb metal and Hg[M(CO)5]2 in THF. Reflux of 1 in Et2O afforded {Yb(THF)2(Et2O)2[(mu-CO)2Mn(CO)3]2}infinity (3) which is a sheet-layer structure. In ether solution, 3 is converted to {Yb(THF)4[(mu-CO)2Mn(CO)3]2}infinity (4) which has a linear structure. In both 3 and 4, ytterbium is 8-coordinated (distorted square antiprism geometry), four coordination sites occupied by molecules of solvent and four more by oxygen atoms of isocarbonyl linkages. The [Mn(CO)5]- anion has trigonal bipyramidal geometry and is linked to ytterbium through two equatorial carbonyls. The formation of two minor products, (THF)2Mn3(CO)10 (5) and [(THF)5Yb(mu-CO)Mn3(CO)13][Mn3(CO)14] (6), was observed during condensation of 1 into 3 and 4.

A stacking interaction between a bridging hydrogen atom and aromatic pi density in the n-B18H22-benzene system.

The structures of n-B18H22 and of n-B18H22 x C6H6 were determined by single-crystal X-ray analysis at -60 degrees C. The geometry of the boron cluster itself does not seem to be appreciably affected by solvation. There does, however, appear to be an unusual interaction of a polyborane bridging hydrogen atom with the benzene pi system, giving rise to an extended stacked structure. The 1H{11B} spectrum of n-B18H22 in [D6]benzene differs from that in [D12]cyclohexane most noticeably in the bridging proton region. Upon moving from the aliphatic to the aromatic solvent, the greatest increase in shielding was for the signal corresponding to the bridge hydrogen atom that interacts with the pi system of benzene; the signal was shifted upfield by 0.49 ppm. Density functional theory calculations were performed on 1:1 and 2:1 complexes of the n-B18H22 unit with benzene.

Preparation and crystal structures of a series of titanium(III) 9-BBN hydroborate complexes containing Ti...H agostic interactions.

9-BBN hydroborate complexes Ti{(mu-H)2BC8H14}3(THF)2 (1), Ti{(mu-H)2BC8H14}3(OEt2) (2), and [K(OEt2)4]-[Ti{(mu-H)2BC8H14}4] (4) were formed from the reaction of TiCl4 with K[H2BC8H14] in diethyl ether or THF. Ti{(mu-H)2BC8H14}3(PhNH2) (3) was isolated from the reaction of 2 with aniline in diethyl ether. In the formation of these complexes, Ti(IV) is reduced to Ti(III). The coordinated diethyl ether in 2 can be displaced by the stronger bases THF and aniline, to form 1 and 3, respectively. All of the compounds were characterized by single-crystal X-ray diffraction analysis. In complex 1, which contains two coordinated THF ligands, the titanium possesses a 17 electron configuration and there is no evidence for agostic interaction. Complexes 2 and 3 contain only one coordinated ether or aniline ligand, and the titanium possesses a 15 electron configuration. In these compounds, a C-H hydrogen on an alpha carbon on the BC8H14 unit of a 9-BBN hydroborate ligand forms an agostic interaction with the titanium. Criteria for assessing the existence of agostic interactions are discussed. As the potassium salt, the anion of complex 4 is more stable than the complexes 1-3. Organometallic anions of the type [ML4]- for titanium(III) are rare.

Two distinct Ln(III)-Cu(I) cyanide extended arrays: structures and synthetic methodology for inclusion and layer complexes.

Encapsulation complexes formulated as {[La(DMF)(9)](2)[Cu(12)(CN)(18)].2DMF}(infinity), 1, and {[Ln(DMF)(8)][Cu(6)(CN)(9)].2DMF}(infinity) (Ln = Eu, 2; Gd, 3; Er, 4) were obtained from the one step reaction of LnCl(3) (Ln = La, Eu, Gd, Er) with CuCN and KCN in DMF. They consist of a three-dimensional Cu-CN anionic array with pockets occupied by the cation, [Ln(DMF)(x)](3+) (x = 8, 9). These complexes are believed to be the first examples of encapsulated Ln(3+) cations, and the zeolite-like anionic network is unique. A two step procedure that employs the same components generates the layer structure {Ln(DMF)(4)Cu(2)(CN)(5)}(infinity) (Ln = La, 5; Gd, 6; Er, 7) in which the five-membered ring repeating unit has Cu-CN-Ln and Cu-CN-Cu linkages which are also without precedent. Encapsulation complexes can also be prepared from CuCl, reacting with LnCl(3) and KCN. The crystal structure of {K(DMF)(2)Cu(CN)(2)}(infinity) (8) provides insight into the proposed reaction pathways for forming these two different structural types.

Synthesis and X-ray and neutron structures of Zr{(mu-H)2BC8H14}4.

The complex Zr(9-BBN)4 [9-BBN = (mu-H)2BC8H14] has been synthesized via the reaction of K(9-BBN) with ZrCl4 in diethyl ether. The structure of the title compound has been determined by X-ray and neutron single-crystal diffraction techniques. Each 9-BBN ligand is coordinated to the Zr atom via two B-H-Zr bridges, and these metal-ligand bonding interactions are further augmented by three prominent C-H...Zr agostic interactions. Average molecular parameters derived from the neutron analysis: Zr-H = 2.051(8) A, B-H = 1.286(7) A, Zr...B = 2.409(6) A, Zr-H-B = 87.7(4) degrees , H-Zr-H = 58.9(3) degrees . The Zr...H distances corresponding to the three C-H...Zr agostic interactions are 2.424(7), 2.663(8), and 2.551(7) A. The fourth potential C-H...Zr interaction has a Zr...H distance [3.146(7) A] that is too long to be considered in the agostic range. Single-crystal X-ray diffraction data were collected on an Enraf-Nonius Kappa CCD diffraction system, and neutron diffraction data were collected on the quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin; the final agreement factor for the neutron analysis is 6.52% for 2557 reflections with I > 2sigma(I).

Europium(II) and ytterbium(II) cyclic organohydroborates with agostic interactions.

The divalent lanthanide bis((cyclooctane-1,5-diyl)dihydroborate) complexes {K(THF)4}2{Ln{(mu-H)2BC8H14}4} (Ln = Eu, 3; Yb, 4) were prepared by a metathesis reaction between (THF)(x)LnCl2 and K[H2BC8H14] in THF in a 1:4 molar ratio. Although the reaction ratios were varied between 1:3 and 1:6, complexes 3 and 4 were the only lanthanide 9-BBN hydroborates produced. Because of disorder of THF in crystals of 3 and 4, good single-crystal X-ray structural data could not be obtained. However, when the potassium cation was replaced by the tetramethylammonium cation or when MeTHF (2-methyltetrahydrofuran) was employed in place of THF, good quality crystals were obtained. Complexes [NMe4]2[Ln{(mu-H)2BC8H14}4] (Ln = Eu, 5; Yb, 6) were afforded by metathesis reactions of NMe4Cl with 3 and 4 in situ. On the basis of the single-crystal X-ray diffraction analysis, the four 9-BBN tetrahydroborate ligands are tetrahedrally arranged around the lanthanide cation in 5 and 6. The two structures differ in that one alpha-C-H bond from each of the four {(mu-H)2BC8H14}4 units exhibits an agostic interaction with Eu(II) in 5 but, in complex 6, only two of the alpha-C-H bonds form agostic interactions with Yb(II). Complexes {K(MeTHF)3}2{Ln{(mu-H)2BC8H14}4} (Ln = Eu, 7; Yb, 8) were produced by employing MeTHF in place of THF. The structures of 7 and 8 display connectivity between the anion {Ln{(mu-H)2BC8H14}4}2- and the cation {K(MeTHF)3}+, in which the potassium not only interacts directly with the hydrogens of the Ln-H-B bridged bonds but is also involved in agostic interactions with alpha-C-H bonds. By systematically examining the structures of complexes 3-8 and taking into account the previously reported complexes (THF)4Ln{(mu-H)2BC8H14}2 (Ln = Eu, 1; Yb, 2), it is concluded that Eu(II) appears to have a better ability to form agostic interactions than Yb(II) because of its larger size, even though Yb(II) has a higher positive charge density.

Lanthanide-transition-metal carbonyl complexes: new [Co4(CO)11]2- clusters and lanthanide(II) isocarbonyl polymeric arrays.

Two types of Ln(II)-Co(4) isocarbonyl polymeric arrays, [(Et(2)O)(3)(-)(x)()(THF)(x)()Ln[Co(4)(CO)(11)]]( infinity ) (1-3; x = 0, 1) and [(THF)(5)Eu[Co(4)(CO)(11)]]( infinity ) (4), were prepared and structurally characterized. Transmetalation involving Ln(0) and Hg[Co(CO)(4)](2) in Et(2)O yields [(Et(2)O)(3)Ln[Co(4)(CO)(11)]]( infinity ) (1, Ln = Yb; 2, Ln = Eu). Dissolution of the solvent-separated ion pairs [Ln(THF)(x)()][Co(CO)(4)](2) (Ln = Yb, x = 6; Ln = Eu) in Et(2)O affords [(Et(2)O)(2)(THF)Yb[Co(4)(CO)(11)]]( infinity ) (3) and [(THF)(5)Eu[Co(4)(CO)(11)]]( infinity ) (4). In these reactions, oxidation and condensation of the [Co(CO)(4)](-) anions result in formation of the new tetrahedral cluster [Co(4)(CO)(11)](2)(-). The two types of Ln(II)-Co(4) compounds contain different isomers of [Co(4)(CO)(11)](2)(-), and, consequently, the structures of the infinite isocarbonyl networks are distinct. The cluster in [(Et(2)O)(3)(-)(x)()(THF)(x)()Ln[Co(4)(CO)(11)]]( infinity ) (1-3) possesses pseudo C(3)(v)() symmetry (an apical Co, three basal Co atoms; one face-bridging, three edge-bridging, seven terminal carbonyls) and connects to Ln(II) centers through eta(2),micro(4)- and eta(2),micro(3)-carbonyls to generate a 2-D puckered sheet. In contrast, [(THF)(5)Eu[Co(4)(CO)(11)]]( infinity ) (4) incorporates a C(2)(v)() symmetric cluster (two unique Co environments; two face-bridging, one edge-bridging, eight terminal carbonyls), and isocarbonyl linkages (eta(2),micro(4)-carbonyls) to Eu(II) atoms create a 1-D zigzag chain. Complexes 1-4 contain the first reported eta(2),micro(4)-CO bridges between a Ln and a transition-metal carbonyl cluster. Infrared spectroscopic studies revealed that the isocarbonyl associations to Ln(II) persist in solution. The solution structure and dynamic behavior of the [Co(4)(CO)(11)](2)(-) cluster in 1 was investigated by variable-temperature (59)Co and (13)C NMR spectroscopies.

Synthesis, structural characterization, and reactions of cyclic organohydroborate half-zirconocene compounds.

Cyclic organohydroborate complexes of zirconium monocyclopentadienyl CpZr[(mu-H)(2)BC(5)H(10)](3), 1, and CpZr[(mu-H)(2)BC(8)H(14)](3), 2, were prepared from the reaction of CpZrCl(3) with 3 mol of K[H(2)BC(5)H(10)] and K[H(2)BC(8)H(10)], respectively, in diethyl ether. Compounds 1 and 2 react with the hydride ion abstracting agent B(C(6)F(5))(3) to form the same salt [CpZr(OEt)(OEt(2))(mu-OEt)](2)[HB(C(6)F(5))(3)](2), 5. The complexes CpZr(Cl)[(mu-H)(2)BC(8)H(14)](2), 3, and CpZr(Cl)[(mu-H)(2)BC(8)H(14)](2) [where Cp = C(5)(CH(3))(5)], 4, were prepared from the reaction of CpZrCl(3) and CpZrCl(3) with K[H(2)BC(8)H(10)] in 1:2 molar ratios, respectively. An alpha-hydrogen of a BC(8)H(14) unit forms an agostic interaction with Zr in compound 3 but not in 4. All of the compounds were characterized by single-crystal X-ray diffraction analysis.