Hypercoordinated eka-tin materials with dangling aryl-methoxy and -methylthio ligands exhibiting intramolecular secondary bonding and aryl bond stabilization in reactions with organotin chlorides.

The syntheses of [2-(CH3ECH2)C6H4]PbPh3-nCln, (n = 0, E = O (4), E = S (5); n = 1, E = O (6), E = S (7); n = 2, E = O (8), are described. NMR and single crystal data illustrate significant Pb⋯E interactions increasing as n progresses from 0 to 2. The Pb⋯E interactions stabilize the Pb-aryl bonding to the extent that the reactions of 4 and 5 with Me2SnCl2 result in interchange of a Ph group and Cl to produce 6 and 7, respectively, together with Me2PhSnCl.

A utility for organoleads: selective alkyl and aryl group transfer to tin.

Me4Pb and Ph4Pb readily transfer methyl or phenyl groups to an equivalent molar ratio of tin(iv) chlorides in the order SnCl4 > MeSnCl3 > Me2SnCl2 > Me3SnCl, often in a selective manner. Me3PbCl and Ph3PbCl specifically transfer a single methyl/phenyl group under the same reaction conditions to produce recovered yields in >75%. Specific transfer of 2 methyl groups from PbMe4 can be achieved at elevated temperatures and/or a 2 : 1 molar ratio Pb : Sn.

Antimony(v) cations for the selective catalytic transformation of aldehydes into symmetric ethers, α,ß-unsaturated aldehydes, and 1,3,5-trioxanes.

1-Diphenylphosphinonaphthyl-8-triphenylstibonium triflate ([][OTf]) was prepared in excellent yield by treating 1-lithio-8-diphenylphosphinonaphthalene with dibromotriphenylstiborane followed by halide abstraction with AgOTf. This antimony(v) cation was found to be stable toward oxygen and water, and exhibited exceptional Lewis acidity. The Lewis acidity of [][OTf] was exploited in the catalytic reductive coupling of a variety of aldehydes into symmetric ethers of type in good to excellent yields under mild conditions using Et3SiH as the reductant. Additionally, [][OTf] was found to selectively catalyze the Aldol condensation reaction to afford α-ß unsaturated aldehydes () when aldehydes with 2 α-hydrogen atoms were used. Finally, [][OTf] catalyzed the cyclotrimerization of aliphatic and aromatic aldehydes to afford the industrially-useful 1,3,5 trioxanes () in good yields, and with great selectivity. This phosphine-stibonium motif represents one of the first catalytic systems of its kind that is able to catalyze these reactions with aldehydes in a controlled, efficient manner. The mechanism of these processes has been explored both experimentally and theoretically. In all cases the Lewis acidic nature of the antimony(v) cation was found to promote these reactions.

Platinum-Catalyzed Reduction of DMF by 1,1,3,3-Tetramethyldisiloxane, HMeSi2OSiMe2H: New Intermediates HSiMe2OSiMe2OCH2NMe2 and HSiMe2(OSiMe2)3OCH2NMe2 and Their Further Chemical Reactivity.

The use of Karstedt's catalyst to study the reduction of Me2NCHO (DMF) by the popular "dual SiH"-containing tetramethyldisiloxane, HMe2SiOSiMe2H (1), has revealed that the first step in the process involves an initial single hydrosilylation to form HSiMe2OSiMe2OCH2NMe2 (3). This intermediate is readily isolated and purified via distillation. In the continued presence of the catalyst, 3 transforms to the transient tetrasiloxane HMe2SiOSiMe2OSiMe2OSiMe2OCH2NMe2 (4), along with the formation of Me3N. The tetrasiloxane 4 itself transforms to Me3N and (Me2SiO) n (n = 4-6). Despite the demonstrated reactivity of 3, it can also be used to perform the expected metal-catalyzed hydrosilylation chemistry of the SiH group as well as reactions of the SiOCH2NMe2 functionality involving siloxane chain extension and is thus an important new reagent for siloxane chemistry.

Metal-catalyzed reduction of HCONR'2, R' = Me (DMF), Et (DEF), by silanes to produce R'2NMe and disiloxanes: a mechanism unraveled.

We demonstrate that using Mo(CO)(6), Mo(CO)(5)NMe(3), and (η(5)-C(5)H(5))Mn(CO)(3) as catalysts for the silane, R(3)SiH, reduction of N,N-dimethylformamide (DMF), and N,N-diethylformamide (DEF), we can observe, intercept, and isolate, the important siloxymethylamine intermediates, R(3)SiOCH(2)NR'(2), R' = Me, Et, for the first time. In the presence of excess DMF such intermediates thermally react with a variety of silanes to form the corresponding disiloxanes in the absence of a metal catalyst. We also show that the germanium hydrides, Et(3)GeH and Bu(3)GeH, also reduce DMF to form trimethylamine and the corresponding digermoxane but observe no intermediates R(3)GeOCH(2)NMe(2). Bu(3)SnH reduces DMF, but along with the low yields of Bu(3)SnOSnBu(3) (but no Bu(3)SnOCH(2)NMe(2)) significant side products are obtained including (Bu(3)Sn)(2) and Bu(4)Sn. In the absence of DMF the siloxymethylamines can undergo metal-catalyzed reactions with silanes, germanes and stannanes to form disiloxanes, and R(3)SiOER(3) E = Ge, Sn, respectively. To date, the most efficient catalyst for this latter process is (η(5)-C(5)H(5))Mo(CO)(3)CH(3) via a photochemical reaction.

Methyl transfer from Fe (and Mo) to Sn: formation of (eta(5)-C(5)H(5))M(CO)(n)Sn(t)Bu(2)Me (M = Fe, n = 2; M = Mo, n = 3) complexes from photochemical irradiation of (eta(5)-C(5)H(5))M(CO)(n)Me and (t)Bu(2)SnH(2).

Formation of an Sn-CH(3) bond, concomitantly with an Sn-M (M = Fe, Mo), is readily achieved from the photochemical reactions of (t)Bu(2)SnH(2) with (eta(5)-C(5)H(5))M(CO)(n)Me (M = Fe, n = 2; M = Mo, n = 3) via the intermediacy of (eta(5)-C(5)H(5))M(CO)(n)Sn(t)Bu(2)H.