Facile synthesis of cyclopropene analogues of aluminum and an aluminum pinacolate, and the reactivity of LAl[eta(2)-C(2)(SiMe(3))(2)] toward unsaturated molecules (L=HC[(CMe)(NAr)](2), Ar=2,6-i-Pr(2)C(6)H(3)).

Reduction of LAlI(2) (1) (L = HC[(CMe)(NAr)](2), Ar = 2,6-i-Pr(2)C(6)H(3)) with potassium in the presence of alkynes C(2)(SiMe(3))(2), C(2)Ph(2), and C(2)Ph(SiMe(3)) yielded the first neutral cyclopropene analogues of aluminum LAl[eta(2)-C(2)(SiMe(3))(2)] (3), LAl(eta(2)-C(2)Ph(2)) (4), and LAl[eta(2)-C(2)Ph(SiMe(3))] (5), respectively, whereas reduction of 1 in the presence of Ph(2)CO gave an aluminum pinacolate LAl[O(2)(CPh(2))(2)] (6), irrespective of the amount of Ph(2)CO employed. The unsaturated molecules CO(2), Ph(2)CO, and PhCN inserted into one of the Al-C bonds of 3 leading to ring enlargement to give novel aluminum five-membered heterocyclic systems LAl[OC(O)C(2)(SiMe(3))(2)] (7), LAl[OC(Ph)(2)C(2)(SiMe(3))(2)] (8), and LAl[NC(Ph)C(2)(SiMe(3))(2)] (9) in high yields. In contrast, 3 reacted with t-BuCN, 2,6-Trip(2)C(6)H(3)N(3) (Trip = 2,4,6-i-Pr(3)C(6)H(2)), and Ph(3)SiN(3) resulting in the displacement of the alkyne moiety to afford LAl[N(2)(Ct-Bu)(2)] (10) with an unprecedented aluminum-containing imidazole ring, and the first monomeric aluminum imides LAlNC(6)H(3)-2,6-Trip(2) (11) and LAlNSiPh(3) (12). All compounds have been characterized spectroscopically. The variable-temperature (1)H NMR studies of 3 and ESR measurements of 3 and 4 suggest that the Al-C-C three-membered-ring systems can be best described as metallacyclopropenes. The (27)Al NMR resonances of 2 and 3 are reported and compared. Molecular structures of compounds 3, 4, 6.OEt(2), 8.OEt(2), and 9 were determined by single-crystal X-ray structural analysis.

1-Boraadamantane: reactivity towards di(1-alkynyl)silicon and -tin compounds: first access to 7-metalla-2,5-diboranorbornane derivatives.

1-Boraadamantane (1) reacts with di(1-alkynyl)silicon and -tin compounds 2 (Me2M(C...CR)2: M=Si; R=Me (a), tBu (b), SiMe3 (c); M=Sn, R=SiMe3 (e)) in a 1:1 ratio by intermolecular 1,1-alkylboration, followed by intramolecular 1,1-vinylboration, to give siloles 5a-c and the stannole 5e, respectively, in which the tricyclic 1-boraadamantane system is enlarged by two carbon atoms. Owing to the high reactivity of 1, a second fast intermolecular 1,1-alkylboration competes with the intramolecular 1,1-vinylboration as the second major step in the reaction if the substituent R at the C...C bond is small (2a) and/or if the M-C... bond is also highly reactive, as in 2d (M=Sn, R= Me) and 2e (M=Sn, R=SiMe3). This leads finally to the novel octacyclic 7-metalla-2,5-diboranorbornane derivatives 8a, 8d, and 8e, of which 8e was characterized by X-ray analysis in the solid state. 1,1,2,2-Tetramethyldi(1-propynyl)disilane, MeC...C-SiMe2SiMe2-C...CMe (3), reacts with 1 to give mainly a 1,2-dihydro-1,2,5-disilaborepine derivative 9 and the octacyclic compound 11, which is analogous to 8a but with an Me4Si2 bridge. All new products were characterized in solution by 1H, 11B, 13C, 29Si, and 119Sn NMR spectroscopy. For 8 and 11, highly resolved 29Si and 119Sn NMR spectra revealed the first two-bond isotope-induced chemical shifts, 2delta10/11B(29Si) and 2delta10/11B(119Sn) respectively, to be reported.

Monocarbaborane chemistry. Preparation and characterisation of [4-CB8H9]-, the 'missing' closo-carbaborane anion.

Thermolysis in the solid state of Cs+[arachno-CB9H14]-, or of Cs+[nido-CB9H12]-, or the oxidation of nido-1-CB8H12 with I2 in THF at -78 degrees C in the presence of NEt3, gives the first nine-vertex closo monocarbaborane, the stable [closo-4-CB8H9]- anion, in yields of 56, 61 and 75%, respectively.

Metal-induced B-H activation: addition of methyl acetylene carboxylates to Cp*Rh-, Cp*Ir-, (p-cymene)Ru-, and (p-cymene)Os half-sandwich complexes containing the chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligand

The reactions of the 16e half-sandwich complexes [Cp*M[S2C2(B10)H10)]] (1: M=Rh; 2: M = Ir) and [eta6-(4-isopropyltoluene)M[S2C2(B10H10)] (3: M=Ru; 4: M=Os) with both methyl acetylene monocarboxylate and dimethyl acetylene dicarboxylate were studied in order to obtain more evidence for B-H activation, ortho-metalation, and B(3,6)-substitution of the carborane cluster. In the case of rhodium, the reaction of 1 with methyl acetylene monocarboxylate led to new complexes after twofold insertion into one of the Rh-S bonds (7), and twofold insertion together with B-substitution at the carborane cage (8). In the case of iridium, the reactions of 2 with methyl acetylene monocarboxylate gave two geometrical isomers 10 and 11, in which the alkyne is inserted into one of the Ir-S bonds, followed by hydrogen transfer from the carborane via the metal to the former alkyne and formation of an Ir-B bond. Only one type each (12 and 13) of these isomers was obtained from the reactions of the ruthenium and osmium half-sandwich complexes 3 and 4. The 16e starting materials 1-4 reacted with dimethyl acetylene dicarboxylate at room temperature to give the complexes 14-17, respectively, which are formed by addition of the C=C bond to the metal center and insertion into one of the metal-sulfur bonds. The proposed structures in solution were deduced from NMR data (1H, 11B, 13C, 103Rh NMR), and X-ray structural analyses were carried out for the rhodium complexes 7 and 8.

Hydroxo hydrido complexes of iron and cobalt (Sn-Fe-Sn, Sn-Co-Sn): probing agostic Sn...H-M interactions in solution and in the solid state

Bis(toluene)iron 9 reacts with Lappert's stannylene [Sn[CH(SiMe3)2]2] (4) to form the paramagnetic bis-stannylene complex [[(eta6-toluene)Fe-Sn-[CH(SiMe3)2]2]2] (10). Compound 10 reacts with H2O to form the hydroxo hydrido complex [(eta6-C7H8)(mu-OH)(H)-Fe-[Sn[CH(SiMe3)2]2]2] (12) in high yield; its solid-state structure has been elucidated by X-ray and neutron diffraction analysis. In agreement with the 1H NMR results, 12 contains a hydridic ligand whose exact coordination geometry could be determined by neutron diffraction. The 1H and 119Sn NMR analysis of 12 suggested a multicenter Sn/Sn/H/Fe bonding interaction in solution, based on significantly large values of J(Sn,H,Fe) = 640+/-30 Hz and J(119Sn,119Sn) = 4340+/-100 Hz. In solution, complex 12 exists as two diastereomers in a ratio of about 2:1. Neutron diffraction analysis has characterized 12 as a classical metal hydride complex with very little Sn...H interaction and a typical Fe-H single bond (1.575(8) A). This conclusion is based on the fact that the values of the Sn...H contact distances (2.482(9) and 2.499(9) A) are not consistent with strong Fe-H...Sn interactions. This finding is discussed in relation to other compounds containing M-H...Sn units with and without strong three-center interactions. The neutron diffraction analysis of 12 represents the first determination of a Sn-H atomic distance employing this analytical technique. The cobalt analogues [(eta5-Cp)(mu-OH)(H)Co-[Sn[CH(SiMe3)2]2]2] (15) and [(eta5-Cp)(OD)(D)Co-[Sn[CH-(SiMe3)2]2]2] [D2]15, which are isolobal with 12, were prepared by the reaction of [(eta5-Cp)Co-Sn[CH(SiMe3)2]2] (14) with H2O and D2O, respectively. The magnitude of J(Sn,H) (539 Hz) in 15 is in the same range as that found for 12. The molecular structure of 15 has been determined by X-ray diffraction which reveals it to be isostructural with 12. The coordination geometries of the Co(Fe)-Sn1-O-Sn2 arrangements in 12 and 15 are fully planar within experimental error. Compounds 10 and 15 are rare examples of fully characterized complexes obtained as primary products from water activation reactions.

Rhodium-Induced Selective B(3)/B(6)-Disubstitution of ortho-Carborane-1,2-dithiolate.

The various reactive sites in the 16 e complex 1 invite addition reactions with alkynes. After addition of 2 to one of the Rh-S bonds, B-H activation takes place which finally leads to the complex 3, in which a B(3)/B(6)-disubstituted o-carborane cage is present for the first time.