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The reactivity of tin and lead phosphanido complexes with chalogens is reported. The addition of sulfur to [(BDI)MPCy2] (M = Sn, Pb; BDI = CH{(CH3)CN-2,6-iPr2C6H3}2) results in the formation of phosphinodithioates [(BDI)MSP(S)Cy2] regardless of the conditions; however, when selenium is added to [(BDI)MPCy2], a selenium insertion product, phosphinoselenoite [(BDI)MSePCy2], can be isolated. This compound readily reacts with additional selenium to form the phosphinodiselenoate complex [(BDI)MSeP(Se)Cy2]. In contrast, the addition of selenium to [(BDI)SnP(SiMe3)2] results in the formation of the heavy ether [(BDI)SnSeSiMe3]. Differences in the solution and solid-state molecular species of tin phosphinoselenoite and phosphinodiselenoate complexes were probed using multinuclear solution and solid-state NMR spectroscopy.

A series of heavier group 14 element, terminal phosphide complexes, M(BDI)(PR(2)) (M = Ge, Sn, Pb; BDI = CH{(CH(3))CN-2,6-iPr(2)C(6)H(3)}(2); R = Ph, Cy, SiMe(3)) have been synthesized. Two different conformations (endo and exo) are observed in the solid-state; the complexes with an endo conformation have a planar coordination geometry at phosphorus (M = Ge, Sn; R = SiMe(3)) whereas the complexes possessing an exo conformation have a pyramidal geometry at phosphorus. Solution-state NMR studies reveal through-space scalar coupling between the tin and the isopropyl groups on the N-aryl moiety of the BDI ligand, with endo and exo exhibiting different J(SnC) values. The magnitudes of the tin-phosphorus and lead-phosphorus coupling constants, |J(SnP)| and |J(PbP)|, differ significantly depending upon the hybridization of the phosphorus atom. For Sn(BDI)(P{SiMe(3)}(2)), |J(SnP)| is the largest reported in the literature, surpassing values attributed to compounds with tin-phosphorus multiple-bonds. Low temperature NMR studies of Pb(BDI)(P{SiMe(3)}(2)) show two species with vastly different |J(PbP)| values, interpreted as belonging to the endo and exo conformations, with sp(2)- and sp(3)-hybridized phosphorus, respectively.

Reaction of the alkylzinc bromide Zn(C{SiMe3}2{SiMe2hpp})Br (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) with an excess of sodium hydride gives good yields of an unusual zinc hydride cluster, in which five zinc atoms are linked by (-H) bridges

The alkylcobalt halide [{(2-C 5 H 4 N)Me 2 Si}(Me 3 Si) 2 CCoCl] 2 (2) and the lithium silanolatocobaltates Li(THF) 2 (μ-Br)2Co(μ-OSi-Me 3 ) 2 Co(μ-Br) 2 Li(THF) 2 (4) and [LiBr{Li(THF)} 2 {CoBr(OSiMe 3 ) 3 }] 2 (5) form centrosymmetrical halogen-bridged dimers in the crystalline state. Compound 4 shows bromide bridges between lithium and cobalt, and silanolato bridges between the cobalt atoms. Below 200 K there are significant antiferromagnetic interactions between the cobalt centres. Compound 5 crystallises in a novel structure in which two cubane-like fragments containing silanolato bridges are linked together through a Li 2 Br 2 ring.

The lithium derivative (1) reacted with AlCl3 or Me2AlCl to give, respectively, the monomeric compounds (2a) and (2b). The product from reaction with commercially available GaBr3 was the analytically pure monomeric heterocycle (3), indicating that the starting halide had been partially hydrolysed before use. The reaction between 1 and commercially available InCl3 gave a homogenous white solid (4) with X = Cl (59%) or OH (41%). The X-ray crystal structures of 2a, 3, and 4 have been determined.

The lithium reagent (3) reacts with a molar equivalent of anhydrous zinc bromide to give the dimeric compound (2a), in which zinc is four-coordinate. The product from a similar reaction with Li{C(SiMe3)2(SiMe2NPhMe)} is the lithium zincate [Li(THF)2(?-Br)2Zn{C(SiMe3)2(SiMe2NPhMe)}] (4), in which the zinc is only three-coordinate. The crystal structures of 2a and 4 have been determined.

Metallation of (HMe2Si)(Me3Si)2CH (1) by LiMe gave the organolithium compound Li(THF)2C(SiMe3)2(SiMe2H) (2a), which exists in toluene solution as a mixture of covalent species and ion pairs [Li(THF)4][Li{C(SiMe3)2(SiMe2H)}2] (2b). Treatment of a mixture of 1 and LiMe with KOBut gave KC(SiMe3)2(SiMe2H) (3). This reacted with AlMe2Cl in hexane/THF to give Al(THF)Me2{C(SiMe3)2(Si Me2H)} (4). Treatment of (HMe2Si)(PhMe2Si)2CH (5) with LiMe in Et2O/THF gave the THF adduct [Li(THF)2C(SiMe2Ph)2(SiMe2H)] (6); in the presence of KOBut the solvent-free [K][C(SiMe2Ph)2(SiMe2H)] (7) was obtained. Crystal structure determinations showed that 6 crystallizes in a molecular lattice and 7 in an ionic lattice in which the coordination sphere of the potassium comprises phenyl groups and hydrogen atoms attached to silicon, as well as the central carbon of the bulky carbanion. Compound 7 reacted with an excess of AlMe2Cl to give [AlClMe{C(SiMe2Ph)2(SiMe2H)}]2 (8) and AlMe3. A small amount of the methoxo derivative [Al(OMe)Me{C(SiMe2Ph)2(SiMe2H)}]2 (9) was obtained as a byproduct, presumably after the accidental admission of traces of air. X-ray structural determinations showed that 8 forms halogen-bridged dimers, with the bulky ligands in the anti-configuration, and 9 forms methoxo-bridged species in which the bulky ligands are syn.

The first structurally characterized dialkylaluminate [{Li(THF)}(AltBu{C(SiMe3)3}H2)]2 (3) is dimeric in the solid state with [Li(THF)]+ and [AltBu{C(SiMe3)3}H2]− fragments linked by Li···H−Al bridges. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Care is necessary when relating physical data obtained at one temperature on compounds showing significant intermolecular interactions to X-ray data obtained at other temperatures. This is revealed by the determination of the structure of tri(cyclohexyl)tin chloride at nine different temperatures between 108 and 298 K. In the crystal, the molecules pack in chains parallel to the c axis with the Sn and Cl atoms close to the plane, with y = 0.25. At low temperature, successive molecules in the chain are related by the glide plane in space group P2(1)/c, and there is significant intermolecular interaction. As the temperature is raised, the Cy(3)SnCl.Sn interactions weaken and the intramolecular Sn-Cl bonds strengthen. At about 248 K, there is an order-disorder transition to space group P2(1)/m with the c axis halved, and at room temperature the structure is best described as comprising discrete molecules, as previously reported. Thus, some of the molecular dimensions, in particular the Sn-Cl bond lengths, are not constant but are functions of temperature.

The reaction of [Li(thf)2AlH3{C(SiMe3)3}]2 (1) with four equivalents of ArOH (Ar = C6H3Pri2-2,6) yielded [Li(thf)(μ-OAr)2AlH{C(SiMe3)3}] (2) (thf = tetrahydrofuran), which has a structure containing a four-membered LiO2Al ring both in the crystal and in toluene solution. The corresponding reaction with ArOH (Ar = C6H3But2-2,6) gave a mixture that could not be separated by fractional crystallisation. The reaction of 1 with Ph3SiOH gave [Al(OSiPh3)2{C(SiMe3)3}(thf)] (3), which was shown by an X-ray structure determination to be monomeric.

The ate complexes [M{C(SiMe3)3}(μ-SBu)2Li(THF)2], M = Ge or Sn, have been made from M(SBu)2 and LiC(SiMe3)3 in tetrahydrofuran and their crystal structures determined. The LiS2M rings are folded at...

The cyclic stannylene (2; RR = C(SiMe3)2SiMe2CH2CH2Me2Si(Me3Si)2C) reacted with alkyl iodides R‘I (R‘ = Et, iPr) to give the SnIV compounds (6b,c), which were converted by treatment with silver trifluoroacetate into (7b,c). Reactions of the stannylene 2 with appropriate enones or diones yielded the products (10), (11), (12), and (13) (OC14H8O = 9,10-phenanthrenediolato). The crystal structures of 6b, 7b,c, and 10−13 have been determined. Treatment of 2 with water, alcohols, or phenol led to ring opening. There is evidence from ESR spectroscopy that the oxidative additions of diones involve radical intermediates. The compound (6a) reacted with ICl to give the chloride (15), but, in contrast to the previously described crowded trialkyltin halides (Me3Si)3CSnMe2X (X = Cl, I), neither 6a nor 15 reacted with nucleophilic reagents.

The organolithium compound Li(THF)(2){C(SiMe3)(2)(SiMe2NMe2)} reacted with one equivalent of MnCl2 to give [Mn(mu-Cl){C(SiMe3)(2)(SiMe2NMe2)}](2) (4) and with 0.5 equivalent of MnCl2 to give Mn{C(SiMe3)(2)(SiMe2NMe2)}(2) together with a small amount of the Mn-III compound [Mn(mu-O){C(SiMe3)(2)(SiMe2NMe2)}](2) (6) formed by adventitious admission of air. With CoBr2, the compound [Co(mu-Br){C(SiMe3)(2)(SiMe2NMe2)}](2) (7) was obtained. The reaction between the lithium compound Li(THF)(2){C(SiMe3)(2)(SiMe2OMe)} and MnCl2 in THF gave [Mn(THF)(mu-Cl){C(SiMe3)(2)(SiMe2OMe)}](2) (5). The crystal structures of compounds 4, 5, 6 and 7 were determined. Compounds 4 and 5 are the first manganese analogues of Grignard reagents containing Mn-C sigma-bonds to be characterised in the solid state. (C) 2002 Elsevier Science B.V. All rights reserved.

The new organosilicon bromides (Me 3 Si) 2 (ZMe 2 Si)CSiMe 2 Br with Z=PhO or MeS have been prepared and new spectroscopic data obtained for the previously reported compounds with Z=H, F, Br, Me, Ph, MeO or PhS. Competitions between pairs of bromides for a deficiency of AgBF 4 in Et 2 O, with the determination of the ratio of the fluoride products by 19 F-NMR spectroscopy, have led to the following approximate relative reactivities of the bromides and so to the relative abilities of the γ-Z groups to provide anchimeric assistance to the leaving of Br − in this reaction: Me, 1; Ph, 40; PhO, 3400; PhS, 5000; MeS, 7000; MeO, 54 000. In methanolysis in CH 2 Cl 2 , (Me 3 Si) 2 (MeOMe 2 Si)CSiMe 2 Cl has been found to be roughly 120 times as reactive as (Me 3 Si) 2 (PhOMe 2 Si)CSiMe 2 Cl. Combination of the results with previously available information suggests the following approximate order of ability of γ-groups Z to provide anchimeric assistance in reactions at the SiX bonds in compounds (Me 3 Si) 2 (ZMe 2 Si)CSiMe 2 X: OCOMe>OMe>OCOCF 3 >MeS>PhS, PhO>N 3 , Cl>NCS>Ph>CHCH 2 >Me.

The complex [Li(TMEDA) {C(SiMe3)(2)SiMe(2)NMe2}] (1) (TMEDA = N,N,N,N-tetramethylethane-1,2,-diamine) was found to crystallise with an internally coordinated structure like that of [Li(THF)(2){C(SiMe3)(2)SiMe2Me2}] (THF = tetrahydrfuran). In contrast, the compound with Ph in place of NMe2 crystallised as a dialkyllithate [Li(TMEDA)(2)][Li{C(SiME3)(2)(SiMe2Ph)}(2)] (4). The reaction of 4 with MgBr2 gave the doubly bromide-bridged lithium-magnesium complex [Li(TMEDA)(mu -Br)(2)Mg{C(SiMe3)(2)(SiMe2Ph)} (THF)] (6), and that of [Li(THF){C(SiMe3)(2)(SiMe2C5H4N-2)}] gave the singly bridged compound [Li(THF)(3)(mu -Br)MgBr{C(SiMe3)(2)(SiMe2C5H4N-2)] (8). The Grignard reagents [Mg{C(SiMe3)(3)}I(OEt2)](2) (10) and [Mg{C(SiMe3)(2) (SiMe2Ph)} I(OEt2)](2) (11) were obtained from the reactions between (Me3Si)(3)CI and (Me2Ph)(Me3Si)CI, respectively, with magnesium metal and shown to have halide-bridged structures. The unsymmetrical dialkylmagnesium [MgBu{C(SiMe3)(2)(SiMe2NMe2)}(THF)] (13), was prepared from a mixture of LiBu, 1 and [MgBr2(OEt2)(2)]. (C) 2001 Elsevier Science B.V. All rights reserved.

In this study, the interaction of monomeric and polymeric sodium silicate with zirconia was investigated in an alkaline environment (pH=9–14) and the reaction mechanisms related to polysialation. Various adsorption and zeta potential measurements confirmed the initial adsorption of silicate to be dominated by hydrated cation sites and subsequent adsorption to be controlled by polycondensation reactions. The extent of polycondensation was shown to be controlled by the degree of polymerization of the silicate and amount of co-precipitation with sodium. The distribution of silicate species was described utilising a thermochemical model based on constants attained by Sjoberg et al. and Caullet et al. with the aid of 29Si Nuclear Magnetic Resonance (NMR) data. In addition, Scanning Electron Microscope (SEM) and X-ray Diffraction analyses confirmed that the morphology and elemental compositions of the polysialates were pH dependent, with a higher proportion of aluminium found in polysialates prepared at a higher pH. The formation of polysialates from sodium silicate and zirconia did not reveal a reaction exotherm through Differential Scanning Calorimetry (DSC) analysis. It is concluded that silicate and polysialate adsorption onto zirconia is greatest when monomeric species predominate at high pH, forming a network structure containing sodium, which is mostly amorphous in nature.

Reactions between LiC(SiMe3)(2)(SiMe2C5H4N-2), 1, and the halides GeCl2.dioxane, SnCl2, and PbCl2 gave the isostructural compounds MCl{C(SiMe3)(2)(SiMe2C5H4N-2)} (M = Ge, 2; Sn, 3; or Pb, 4) which contain three-coordinate M. Treatment of the tin derivative 3 with MeI gave the oxidative addition product SnMeClI{C(SiMe3)(2)(SiMe2C5H4N-2)}, 51 and this reacted with AgOCOCF3 or AgOSO2C6H4Me-4 to give, respectively, the compounds SnMeX2{C(SiMe3)(2)(SiMe2C5H4N-2)} with X = OCOCF3, 6, or OSO2C6H4Me-4, 7. Despite the presence of the bulky C(SiMe3)(2)(SiMe3C5H4N-2) ligand, the Sn atom in the solid state structures of 6 and 7 is five-coordinate, and multinuclear NMR studies show that five-coordinate species are present also in THF solutions of 5, 6, and 7.

An unprecedented series of “lower order” alkali metal (Li, Na, K) cyanocuprates containing the bulky (Me2PhSi)3C ligand has been synthesized. Both monomeric and dimeric forms of the lithium derivative have been characterized; the tetrameric potassium compound provides a striking example of molecular self-assembly driven by K−π-aryl interactions.

The compound HC(SiMe3)2(SiMe2C5H4N-2), 1, reacts with methyllithium in THF to give a good yield of the lithium derivative which has been isolated as a molecular THF adduct 2. This reacts (a) with KOtBu to give 3, which crystallizes in a solvent-free ionic lattice, (b) with MgBr2 to give the Grignard reagent 4, and (c) with CrCl2 to give Cr{C(SiMe3)2(SiMe2C5H4N-2)}2, 5, along with the halide-bridged Grignard reagent analogue 6, which crystallizes in a lattice containing alternate THF-free molecules (6a) and molecules (6b) with coordinated THF. The reactions of 2 with MnCl2 and CoBr2 give the halide-bridged ate complexes 7, and 8, respectively.

The alkylaluminate [Li(THF) 2 AlH 3 C(SiMe 3 ) 2 (SiMe 2 NMe 2 )] 2 ( 3 ), obtained by the reaction between [LiC(SiMe 3 ) 2 (SiMe 2 NMe 2 )·2THF] and LiAlH 4 , has a cyclic structure like those of the compounds [Li(THF) 2 AlH 3 R] 2 (R=C(SiMe 3 ) 3 ( 1 ), or C(SiMe 2 Ph) 3 ( 2 )). The Al and Li atoms are linked by hydride bridges and the NMe 2 groups are not coordinated to metal centres. The compound 1 reacts (i) with one equivalent of SiMe 3 Cl to give the cyclic dialuminate ( 4 ) (characterised by an X-ray study); (ii) with two equivalents of SiMe 3 Cl to give the alaneTHF complex (Me 3 Si) 3 CAlH 2 ·THF ( 5 ); and (iii) with an excess of pyrazole to give [LiAlH(C 3 H 3 N 2 ) 2 C(SiMe 3 ) 3 ] 2 ( 7 ), in which Al and Li atoms are linked by both hydride and pyrazolato bridges. The compound (Me 2 PhSi) 3 CAlH 2 ·THF ( 6 ) has been obtained by the reaction of 2 with two equivalents of SiMe 3 Cl.

The alkylpotassium compound KC{SiMe3}(2){SiMe(2)hpp} (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) reacts with a slurry of CaI2 in toluene to give the internally coordinated dialkylcalcium(II) complex Ca(C{SiMe3}(2){SiMe(2)hpp})(2). The molecular structure in the solid state shows short Ca-N and long Ca-C bonds and a wide C-Ca-C angle. The H-1 and C-13 NMR spectra suggest that the metallacycle is transiently opened in toluene at room temperature.

Reaction of (THF)2KRRK(THF)2 (RR = C(SiMe3)2SiMe2CH2CH2Me2Si(Me3Si)2C) with SnCl2 in Et2O gave a mixture of the cyclic and linear SnII compounds RSnR 4, and ClSnRRSnCl, 9. This mixture was treated with MeI to give the corresponding SnIV compounds 5, and IClMeSnRRSnMeClI, 10. Treatment of RSnMeIR 5 and 10 with AgO2CCF3 gave the corresponding trifluoroacetates 6 and 11, which were structurally characterized.

Reaction of the lithate [Li(THF)(4)][CH2SiMe2C(SiMe3)(2)LiC(SiMe3)(2)SiMe2CH2] with (KOBu)-Bu-t in THF has given the organopotassium reagent (THF)(2)KC(SiMe3)(2)SiMe2CH2CH2Me2Si(Me3Si)(2)CK(THF)(2), 8, and reaction of HC(SiMe3)(2)SiMe2CH2CH2Me2Si(Me3Si)(2)CH with KMe in benzene has given the related ether-free species (C6H6)(2)KC(SiMe3)(2)SiMe2CH2CH2Me2Si-(Me3Si)(2)CK(C6H6)(2), 7. The structures of 7 and 8 have been confirmed by X-ray studies which indicate that both compounds show K ... Me contacts in the range 3.3-3.5 Angstrom. The ether-free reagent 7 reacted with YbI2 in benzene to give the cyclic Yb(II) derivative CH2SiMe2(SiMe3)(2)YbC(SiMe3)(2)SiMe2CH2, which was found to be somewhat more stable toward Et2O than the I previously studied Yb{C(SiMe3)(3)}(2). Reaction of the lithate [Li(TMEDA)(2)][CH2SiMe2C(SiMe3)(2)LiC(SiMe3)(2)SiMe2CH2] (2a) with ZnCl2 in THF gave a cyclic compound CH2SiMe2C(SiMe3)(2)ZnC(SiMe3)(2)SiMe2CH2, which is stable toward boiling aqueous THF. An X-ray study shows that the angle at Zn is 170 degrees. In contrast, the reactions of 2a with SnCl4 or Me2SnCl2 gave linear species ClX2SnC(SiMe3)(2)SiMe2CH2CH2Me2Si(Me3Si)(2)CSnX2Cl, X = Cl or Me, the structures of which were confirmed by single-crystal X-ray diffraction studies.

The compound (Ph2PMe2Si)3CH I reacted (i) with [Mo(CO)6] to give cis-[Mo(CO)4{(Ph2PMe2Si)3CH}] 1 in which two phosphine groups are co-ordinated to molybdenum and one is free, and (ii) with LiBu in the presence of N,N,N′,N′-tetramethylethane-1,2-diamine (tmen) to give [Li(tmen)2][C(SiMe2PPh2)3] 2, which contains discrete planar carbanions and no Li–P co-ordination. The crystal structures of compounds I and 2 have been determined and 1 has been characterised spectroscopically.

The organolithium reagent (1) is readily obtained by reaction of the chloride (Me3Si)2(Me2NMe2Si)CCl with LiBu in THF (tetrahydrofuran) at low temperature. Reactions of 1 with HgBr2, AlCl3, GaCl3, and SnCl4 give [Hg{C(SiMe3)2(SiMe2NMe2)}2] (2), (3), Ga{C(SiMe3)2(SiMe2NMe2)}Cl2 (5), and [Sn{C(SiMe3)2(SiMe2NMe2)}Cl3] (6), respectively, and treatment of 3 with LiPh gives (4). Crystal structure determinations have shown that there is intramolecular coordination of the N atom to the metal M, with formation of a planar four-membered ring, in 1, 3, 4, and 5 (but not 2). Engagement of the lone pair on N in coordination with Al in 3 results in an exceptionally long Si−N bond length of 1.875(2) A, some 0.16 A longer than that in 2 and in simple silylamines generally; the Si−N bond is possibly shorter in 4 (1.851(2) A) and 5 (1.858(4) A), and is markedly so in 1 (1.796(4) A), but still notably long. The lengths of the N−metal bonds in these compounds are similar to those between alkylamines and the metals in coordin...

Single-crystal X-ray diffraction of MC(SiMe3)2(SiMe2hpp) (M = Li, K; hppH = 1,3,4,6,7,8,-hexahydro-2H-pyrimido[1,2-a]pyrimidine) showed nonsolvated organometallic compounds in which the iminonitrogen of the guanidine forms strong intramolecular bonds to generate six-membered metallacycles.

Reaction of the organolithium reagent (THF = tetrahydrofuran), 1, with LiAlH4 gave the title organotrihydridoaluminate, 2, which is unusual for an alkali metal organotrihydridoaluminate in being monomeric and in having the Al linked to the Li not only through hydride but also through another of its ligands. The corresponding reaction with AlCl3 gave the title organoaluminum dichloride. The Si−O bonds in 1 and 2 are not significantly lengthened by the O−metal coordination. The bond from Li to the OMe in 1 oxygen is not significantly different in length from that to the THF oxygen.

Some compounds having very bulky ligands, mainly (Me 3 Si) 3 C (denoted by Tsi) or (PhMe 2 Si) 3 C (denoted by Tpsi), attached to functional tin centres have been studied. Treatment of TsiSnR 2 Cl, R=Me or Ph, with one equivalent of ICl gave the corresponding chloride TsiSnRCl 2 , and use of an excess of ICl gave TsiSnCl 3 in both cases. Reaction of either chloride with one equivalent of Br 2 gave the dibromide TsiSnRBr 2 ; when an excess of Br 2 was used TsiSnMe 2 Cl still gave the dibromide but TsiSiPh 2 Cl gave the tribromide TsiSnBr 3 . Reaction of TsiSnMe 2 Br with AgSCN or Ag 2 O gave TsiSnMe 2 NCS and (TsiSnMe 2 ) 2 O, respectively, but when the crude product from the reaction of TsiSnMeBr 2 with AgNO 3 was recrystallized from MeOH the nitrato–oxide {TsiMe(O 2 NO)Sn} 2 O was obtained. In a seemingly previously unreported type of reaction, the alkoxide TsiSnMe 2 OEt reacted with ICl, Br 2 , or I 2 to give TsiSnMe 2 X, X=Cl, Br, or I, respectively, and Bu 3 SnOEt likewise reacted with ICl to give Bu 3 SnCl. The chlorides TsiSnMe 2 Cl and TsiSnMeCl 2 gave the hydrides TsiSnMe 2 H and TsiSnMeH 2 on treatment with LiAlH 4 , but in the case of TpsiSnMe 2 Cl the TpsiSn bond was cleaved to give TpsiH. The compound (Me 3 Si) 2 C(SnMe 2 Ph)(SiMe 2 Cl) reacted with a 1 M proportion of AgBF 4 in CH 2 Cl 2 with cleavage of the SnPh bond to give the difluoride (Me 3 Si) 2 C(SnMe 2 F)(SiMe 2 F). The crystal structures of the monomeric compounds {TsiMe(O 2 NO)Sn} 2 O, TpsiSnMeCl 2 and TpsiSnCl 3 are reported; {TsiMe(O 2 NO)Sn} 2 O provides the first example of unidentate bonding of an NO 3 group to four-coordinate tin.

The title compounds have been made by treatment of SnCl2 or PbCl2 in tetrahydrofuran with the appropriate reagent LiR, where R = (PhMe2Si)3C, (Me3Si)3C, or (MeOMe2Si)(Me3Si)2C, and their crystal structures determined. In all four compounds, as in the previously reported [Pb{C(SiMe2Ph)3}Cl]2, the metal atoms are linked by bridging Cl atoms, unsymmetrically except in the case of the trimeric [Pb{C(SiMe3)3}Cl]3 (in which the six-membered ring has a distorted boat form). = Sn or Pb, which are isomorphous, there are (relatively weak) intramolecular MeO···M interactions in addition. The compounds [Pb{C(SiMe2Ph)3}Cl]2 and [Pb{C(SiMe3)3}Cl]3 are the only known σ-bonded mono(organo)lead(II) compounds to have been structurally characterized, and [Sn{C(SiMe2Ph)3}Cl]2 is only the second solvent-free mono(alkyl)tin(II) compound. All of the compounds are yellow and air-sensitive in the solid and in solution, and the lead compounds are readily decomposed in solution by exposure to daylight.

The syntheses of a number of alkali metal compounds MC(SiMe3)3-n(SiMe2Ph)n, are described (n = 1, M = Li(TMEDA) (3a), Li(Et2O) (3b), or Na(TMEDA) (3c); n = 2, M = Li(THF)2 (6a), Li(TMEDA) (6b), Na(...

The alkyls EuR2 (R = C(SiMe3)3) and YbR2 (R = [C(SiMe3)2(SiMe2X)], X = Me, CHCH2, or CH2CH2OEt) have been obtained from reactions between KR and MI2, and the ytterbium analogues of Grignard reagent...

A survey is given of the preparation and properties of compounds of elements of Groups 11–13 containing the very bulky ligand (Me3Si)3C or (PhMe2Si)3C, or a related ligand of the type (Me3Si)2(XMe2Si)C.

The structures of the complexes [PbL 2 ], L = 1-phenyl-3-methyl-4-acylpyrazolonato, RCOC 10 H 8 N 2 O, R = Me ( 2 ) or Pr ( 3 ), have been determined by X-ray diffraction studies. Compound 2 is monoclinic, space group P2 1 , a = 11.285(4), b = 14.727(4), c = 20.749(5) A , β = 95.83(3)°, R = 0.039 for 4486 reflections, and 3 is monoclinic, space group C2/c, a = 27.528(11), b = 7.245(11), c = 14.264(7) A , β = 113.6(3)°, R = 0.021 for 2118 reflections. There are three different lead environments in 2 but only one in 3 . In each case the lead atom makes four strong bonds to oxygen and two weaker bonds to either oxygen or nitrogen in adjacent molecules.

Reaction of (Me 3 Si) 2 (PhSMe 2 Si)CCl with BuLi at low temperature gave the organolithium reagent (Me 3 Si) 2 (PhSMe 2 Si)CLi, which was treated with Me 3 SnCl to give (Me 3 Si) 2 (PhSMe 2 Si)CSnMe 3 . Reaction of the latter with a one or two molar proportion of iodine gave the monoiodide (Me 3 Si) 2 (PhSMe 2 Si)CSnMe 2 I and the diiodide (Me 3 Si) 2 (IMe 2 Si)CSnMe 2 I respectively. The corresponding reaction with even a one molar proportion of bromine gave mainly the dibromide (Me 3 Si) 2 (BrMe 2 Si)CSnMe 2 Br. Treatment of the monoiodide with an excess of AgCN in CDCl 3 gave (Me 3 Si) 2 (PhSMe 2 Si)CSnMe 2 CN, but similar treatment with AgBF 4 gave mainly the difluoride (Me 3 Si) 2 (FMe 2 Si)CSnMe 2 F. Hydrolysis of the diiodide gave the mixed diol (Me 3 Si) 2 (HOMe 2 Si)CSnMe 2 OH.

The alkyl chloride R2(HMe2Si)CCl (R = SiMe3) reacted with ICl to give the iodide R2(ClMe2Si)CI, which with MeOH gave R2(MeOMe2Si)CI. This reacted with Mg in Et2O to give MgI2(OEt2)2 (which was isolated and structurally characterised) and the chelated dialkylmagnesium Mg{C(SiMe3)2(SiMe2OMe)}2, apparently following initial formation of the Grignard reagent MeOSiMe2CR2MgI. The latter compound was isolated from the products of the reaction between the iodide R2(MeOMe2Si)CI and Mg in toluene. The lithium compound MeOSiMe2CR2Li was made by treatment of the chloride R2(MeOMe2Si)2CCl with Buli in THF and the chelated structure was confirmed by an X-ray study.

The compound {(Me3Si)2CHSiMe2CH2}2 has been prepared and metalated with MeLi to give the chelated lithate ion [CH2SiMe2C(SiMe3)2LiC(SiMe3)2SiMe2CH2]-, which was isolated as its [Li(TMEDA)2] salt (TMEDA = N,N,N‘,N‘-tetramethylethylenediamine). The potential of this salt as a source of the very bulky dicarbanionic ligand {(Me3Si)2CSiMe2CH2}2 was demonstrated by its reaction with HgBr2 in THF to give the chelated mercury compound [CH2SiMe2C(SiMe3)2HgC(SiMe3)2SiMe2CH2]. The crystal structures of the salt and the mercurial compound were determined.

Mercury compounds of the types HgR1R (R1 = C(SiMe3)3; R = Me, iPr, Bu, tBu or Ph) and HgR2R(R2 = C(SiMe2Ph)3; R = Me, Bu, CH2Ph or Ph) have been prepared. Those containing R1 were made by reactions of the bromides HgR1Br with the Grignard reagents MgRX, and those containing R2 by reaction of HgR2Cl with LiR or, for R = CH2Ph, with Mg(CH2Ph)Cl. Replacement of one R group in HgR2 by the bulky R1 or R2 group leads to a large increase in thermal stability, a marked shift in the 199Hg resonance to lower frequency and an increase in the coupling constant 1 J( 13 C  199 Hg ) for the HgR bond. The compound HgR2Cl does not react further with LiR2 in tetrahydrofuran, but with LiR1 gives HgR1R2; the arrangement of the SiMe2Ph groups in the latter in solution in CH2C12 at low temperature appears to be different from that in the solid.

A review is presented of the chemistry of organometallic compounds containing very bulky ligands of the types C(SiMe 2 X) 3 (X = Me, Ph or OMe) and C(SiMe 3 ) 2 (SiMe 2 X) (X = Ph or OMe) attached to metals of Groups 1–3. The structures and reactions of these compounds show novel features not observed for analogues containing less bulky alkyl groups.

The only product isolated from the reaction of (Me 3 Si) 3 CBr with Mg in THF was, as shown by an X-ray diffraction study, (Me 3 Si) 3 CMg(μ-Br) 3 Mg(THF) 3 , which contains one four-coordinate and one six-coordinate Mg atom. A similar product, (Me 3 Si) 3 CMg(μ-Br) 3 Mg(Et 2 O) x , appears to be formed in the reaction in ether. It is suggested that the high Br/(Me 3 Si) 3 C ratio in the products may be associated with formation of (Me 3 Si) 3 C radicals (which go on to give (Me 3 Si) 3 CH) during the reaction with Mg.

The compounds (PhMe2Si)3CMCl (M  Zn, Cd, or Hg) have been prepared by reaction of (PhMe2Si)3CLi with the chlorides MCl2; for M  Zn or Cd they were obtained via (isolated) Li-containing intermediates thought to [(PhMe2Si)3CM(μ-Cl)2Li(THF)2]. The crystal structures of all three compounds [(PhMe2Si)3CMCl have been determined. The zinc and cadmium chlorides are present in the crystal as the dimers [(PhMe2Si)3CM(μ-Cl)2MC(SiMe2Ph)3], with the metals three-coordinate in a planar environment (for M  Zn, the CMCl angles average 136° and the ClMCl angles 88°; for M  Cd the corresponding values are 137° and 86°) and the chloride bridges slightly unsymmetrical. The cadmium compound is also dimeric in solution in benzene. The compounds appear to be the first structurally characterized organo-zinc or -cadmium halides in which the metal is three-coordinate. The mercury compound also forms dimers in the solid, but the geometry is almost that expected for two-coordinate mercury (the CHgCl angles at the two metal centres are 171.0(3) and 171.3(3)°), with a very weak intermolecular Hg⋯Cl interaction (mean distance 3.29 A). The conformations of the (PhMe2Si)3C groups in all three compounds are discussed.

An X-ray study showed that 1-phenyl-3-methyl-4-butanoylpyrazol-5-one, RCOC10 H9N2O (abH, R = Pr) (1), crystallized in the enol form. It reacted with iron(III) salts to give a dark red complexes, [Fe(ab)3], which crystallized from butanol as the mer-isomer. The complex [Fe(ab)3] (R = Me) was prepared similarly, but the fac-isomer was obtained.

The crowded organotin compound (PhMe 2 Si) 3 CSnMe 2 NCS is monomeric in the solid state and contains tetracoordinate tin, the first tin isothiocyanate to be shown to do so. The related nitrate (PhMe 2 Si) 3 CSnMe 2 ONO 2 is also monomeric, but there is a weak intramolecular interaction between the tin atom and one of the oxygen atoms of the NO 2 group, making the tin quasi-pentacoordinate. The weak coordination appears, however, to have no significant effect on the disposition of the four full bonds around the tin, the geometry being markedly distorted from tetrahedral by steric interactions to a similar extent in both the nitrate and the isothiocyanate.

A single-crystal X-ray study of (Me3Si)3CLi·tmen (tmen =N,N,N′,N′-tetramethylethylenediamine) shows that it crystallises with the ionic structure [Li(tmen)2][Li{C(SiMe3)3}2] but that the anions pack with different orientations from those in crystalline [Li(thf)4][Li{C(SiMe3)3}2](thf = tetrahydrofuran). The 1H, 7Li, 13C and 29Si NMR spectra of (Me3Si)3CLi·2thf and (Me3Si)3CLi·tmen in thf and toluene, and 7Li, 13C and 29Si NMR spectra of the solids are described. Spectra obtained from solutions below ca. 25 °C show the presence of ion pairs [Li(thf)4][Li{C(SiMe3)3}2] or [Li(tmen)2][Li{C(SiMe3)3}2], together with further species which appear to be different in thf and toluene. Spectra from solutions at higher temperatures show inter-species exchange on the NMR timescale.

The compound (Me 3 Si) 2 CCl 2 was converted by treatment with BuLi/Et 2 O/THF and then with Me 2 HSiCl into (Me 3 Si 2 )CCl(SiMe 2 H). Further lithiation with BuLi gave LiC(SiMe 3 ) 2 (SiMe 2 H), which reacted with ZnBr 2 to yield Zn[C(SiMe 3 ) 2 (SiMe 2 H)] 2 . Thence, several new organozinc compounds Zn[C(SiMe 3 ) 2 (SiMe 2 X)] 2 , with X  Cl, Br, I, F, OH, OMe, O 2 CCF 3 , O 2 CH, or NCS, were obtained by substitutions at silicon without cleavage of ZnC bonds. The compounds Cd[C(SiMe 3 ) 2 (SiMe 2 X)] 2 , with X  H, OMe, and Ph, were obtained similarly, but subsequent substitutions at Si were accompanied by reactions at Cd. The crystal structure of the trifluoroacetato derivative Zn[C(SiMe 3 ) 2 (SiMe 2 OCOCF 3 )] 2 shows that the molecules are centrosymmetric, with the O 2 CCF 3 groups forced outwards by steric hindrance away from the metal centre. In Cd[C(SiMe 3 ) 2 (SiMe 2 OMe)] 2 , the methoxy groups are folded in towards cadmium but the Cd … O distance is only slightly shorter than the sum of the van der Waals radii.

The preparation of the novel mercurial [(MeOMe2Si)(Me3Si)2C]2Hg is described. X-ray diffraction studies show that the molecules of this compound and its zinc analogue are centrosymmetric (and the CMC linkage thus linear), but in the former OMe group is directed away from the metal atom whereas in the latter it lies in towards the metal, with an O⋯Zn distance of 2.93 A. In crystals of [(HOMe2Si)(Me3Si)2C]2Zn there is hydrogen bonding between the two oxygen atom within each molecule, and hydrogen bonding between two molecules to give discrete dimers. Because of the hydrogen bonding the CZnC linkage is slightly bent (the angle is 175.9(1)°), and the geometries of the two [(HOMe2Si)(Me3Si)2C]2C groups are significantly different.

The yellow complex trans-[PtCl2L2] (L = PPh2CH(SiMe3)2) has been characterised. An attempt to make a similar complex with the more sterically hindered phosphine PPh2C(SiMe3)3 resulted in the loss of a trimethylsilyl group from one phosphine ligand and activation of a CH bond in another to give the white complex PtClPPh2C(SiMe3)2SiMe2CH2{PPh2CH(SiMe3)2}, the structure of which was established by X-ray diffraction.

The complexes [UO2L2(H2O)] (L = 1-phenyl-3- methyl-4-acylpyrazolonato, RCOC10H8N2O, R = Me (2) or Ph (3) have been synthesised. X-ray diffraction studies show that 2 is monoclinic, space group C2/c, a = 22.798(5), b = 15.939(3), c = 13.703(3) A, β = 97.24(2)°, R = 0.084 for 1925 reflections. Complex 3 is obtained from propanol-acetone as UO2L2(PrOH) (4) which is monoclinic, space group Cc, a = 12.719(2), b = 15.668(5), c = 18.000(7) A, β = 102.27(2)°, R = 0.071 for 2612 reflections. In each case, the coordination at uranium is pentagonal bipyramidal with short UO bonds to oxygen atoms in axial positions. Four of the equatorial positions are occupied by oxygen atoms from the enolato ligands and the fifth by an oxygen atom from the solvent.

The dichloroborane RBCl 2 (R = (Me 3 Si) 3 C) is reduced by LiBH 4 to the diborane trans -RHB(μ-H) 2 BHR, which melts sharply at 183–185°C. It also reacts with ammonia to give the diaminoborane RB(NH 2 ) 2 which on warming in vacuum gives the bis(aminoboryl)amine {R(NH 2 )B} 2 NH. The structures of the diborane and the bis(aminoboryl)amine have been confirmed by X-ray diffraction.

A variety of structures are shown in the solid state by the phosphanides MPHR of alkali metals. Whereas oligomeric and polymeric ladder or helical structures based on M-P bonds predominate for compounds of the lighter homologues (M=Li, Na, K), the 2,6-dimesitylphenylphosphanides of Rb and Cs are present as a Rb4 P4 cubane and a Cs+ {Cs2 (PHR)3 }- contact ion pair, respectively (the partial structures are shown above). These unexpected new structures show interactions between the metal center and π electrons of the ligand.

Reaction of (Me2NMe2Si)3CLi with AlEt2Cl in toluene followed by recrystallization of the product from benzene has given the unprecedented title compound, in which a tetrahedral cationic Al(III) center and a planar carbanion center form part of a six-membered ring. The corresponding reaction with AlCl3 has given Crystal structures of both products are reported.