摘要:
J. CHEM. SOC. DALTON TRANS. 1992 3503Sterically Hindered Organotin Compounds. Part 3.'The Reaction Between Di-fert-butyltin Oxide andOrganoboronic Acids tPaul Brown, Mary F. Mahon and Kieran C. Molloy"School of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UKThe reaction between ( Bu',SnO), and BR(OH), [R = Ph or 2,4,6-Me3C,H, (mes)] has been investigatedand found to yield two classes of product. The first is a boron-rich species, cyc/o-Bu',SnO(RBO),,which exists alongside its acyclic hydrolysis product SnBu',[OB(OH) R12. The second product, whichis tin-rich, SnBu',(OH),[(But,SnO),OBR],, can be formulated as cyc/o-RBO(Bu',SnO), chelatedacross one Sn-0-Sn unit by a molecule of SnBu',(OH),. The crystal and molecular structures ofSnBu',[OB(OH)Ph], and SnBu',(OH),[ ( B u ' , S ~ O ) , O B C , H , M ~ , - ~ , ~ , ~ ] ~ = ~ M ~ C N have been determined.We have been interested for some time in the synthesis oforganotin heterocycles,2 both rings 3,4 and cages,5 as thesecould serve as precursors to porous lattices of zeolite-typestructure containing a Lewis acidic, redox-active centre (Sn).6Heterocycles based on Sn-0-B linkages are interesting targetsin this respect, as boron can itself act as a Lewis-acid centre,and furthermore there is a rich and diverse chemistry associatedwith B-0 compounds, in which triangular BO, and tetrahedralB 0 , - units generate a plethora of ring and cage compounds.'Moreover, there are structural parallels between the organo-metallic oxides of the two elements, provided the strongly Lewis-acidic tin centre is sterically protected to generate oligomersrather than polymers containing the metal in an expanded co-ordination sphere.For example, SnBu',O is a cyclic trimer 1while organoboronic acids 2 can also be condensed to similarrings 3.9 It was of interest to us to examine the possibility ofButp R1 2 3synthesising rings such as those above containing both tin andboron in the same compound, and the results of such efforts arereported herein.Surprisingly, the chemistry of stannaboroxanes has remainedbarren since the early 1970s when the first significant syntheticstudies were undertaken."-' The absence of structurallycharacterised organometallic compounds containing the Sn-0-B linkage is all the more striking, in part due to the industrialimportance of organotin compounds for the deposition of tinoxide on glass (where such compounds might act as models forany interactions with borosilicate surface^),'^ and further due torecent interest in organometallic Si-0-B compounds.' '-'Structures of inorganic tin borates, e.g.MSn(BO,), (M = Mgor Sr), are, however, known."Results and DiscussionReaction of equimolar quantities of SnBu',O and an aryl-t Supplementary, data available: see Instructions for Authors, J. Chem.Soc., Dulton Truns., 1992, Issue 1, pp. xx-xxv.boronic acid RB(OH), [R = Ph or 2,4,6-Me3C6H, (mes)] inbenzene, with removal of water via a Dean and Stark trap,yielded two classes of product which have been separated byrepeated crystallisations. These two types of product, whichdiffer in their Sn:B ratio, are shown in equations (1) and (2).But2/ 4 5\RB(OH);! + SnBut20SnBut~(OH)2[(But2Sn0)20BR] (2)6Little or no observable reaction ensued from the correspondinguse of the insoluble, polymeric organotin oxides SnR,O(R = Me, Pr' or Ph).As shown in equation (l), two related boron-rich products, 4and 5, were identified, and are most clearly seen in the "'SnNMR spectrum where 4 appears at 6 - 127.8 or - 131.6 (R =Ph 4a or mes 4b, respectively) and 5 at 6 -106.4 or -106.7(R = Ph 5a or mes 5b, respectively).However, 4a is thedominant product for R = Ph (70%), while 5b dominates whenthe more hindered mesitylboronic acid is used (84%). In bothcases, the products which crystallise from these solutionmixtures are of type 5.In both pairs of compound the ratio ofboron to tin was established as 2: 1 from integration of the aryland alkyl proton resonances in the 'H NMR spectrum. Theisolated solid compounds 5a and 5b exhibit broad v(0H) bandsat 3250 and 3300 cm-' in their IR spectra, respectively, whichcan be correlated with the presence of 6(BOH) at 6.05 and 6.22in the 'H NMR spectra of the mixtures. The integration for theBOH signal of 5b (2 H) can be entirely accounted for bycorrelation with the integrated intensities for the dibutyltin(18 Hj, CH, (18 H) and aryl signals (4 Hj, suggesting that 4bretains its B-0-B linkages. The H NMR spectrum of the 4a, 5amixture can be interpreted similarly, though in this case thesignals due to the hydrolysis product 5a are in the minority(30%).We therefore assign the structure of 4 to the six-membered B,Sn03 heterocycle, which can be viewed as theincorporation of one tin atom into the B,O, trimer 3 at th3504 J. CHEM. SOC. DALTON TRANS. 1992C(3)Fig. 1probability levelThe asymmetric unit (two independent molecules) of compound 5a showing the atomic labelling. Thermal ellipsoids are at the 30%expense of boron. Furthermore, 5 can be rationalised as theacyclic hydrolysis product of 4, in which one B-0-B linkage hasbeen cleaved and two B(0H) moieties generated, a formulationwhich we have confirmed crystallographically for 5a.The structure of compound 5a, determined crystallo-graphically, is shown in Fig.1. The asymmetric unit consists oftwo independent molecules, both essentially identical and of cis-R,SnO, stereochemistry. The Mossbauer quadrupole splitting(q.s.) values of 2.81 mm s-' for 5a and 2.66 mm s-l for 5b areconsistent with this structure.,' In each molecule the tin ischelated in an anisobidentate manner by one RB(0)OH unit[Sn( 1)-0(4) 1.97(2), Sn(1)-O(3) 2.78(2), Sn(2)-O(6) 1.97(2),Sn(2)-O(5) 2.75(2) A], while the other bonds to tin in amonodentate fashion [Sn( 1)-O( 1) 1.99(2), Sn(2)-O(7) 1.99(2)A] with the oxygen of the second hydroxyl group outside theco-ordination sphere of the metal [Sn(l) O(2) 3.46,Sn(2) O(8) 3.47 A], The covalent Sn-0 bonds are similar inlength to those found in the precursor oxide, (Bu',SnO),, and itsrelated congener [(MeCH,CMe,),SnO],, which lie in therange 1.95-1.98 A.' The co-ordination sphere about tin ismarkedly distorted from an ideal cis-R,SnO, trigonalbipyramid, presumably due mainly to the small bite angle ofthe RBO, ligand [0(3)-Sn( 1)-0(4) 54.6(6), 0(5)-Sn(2)-0(6)55.9(6)"].Chelation by the RBO, ligand also reduces the0-B-0 angle [0(3)-B(2)-0(4) 103(3)"] compared to thecorresponding unidentate ligand [0( 1)-B( 1)-0(2) 120(3)"],though the difference is less marked in the second molecule ofthe asymmetric unit [112(2), 118(2)", respectively]. The axial0-Sn-0 angles are significantly reduced from 180" [0( 1)-Sn( 1)-0(3) 146.3(6), 0(5)-Sn(2)-0(7) 145.7(6)"], while theC-Sn-C angle is widened from 120" [C( 13)-Sn( 1)-C( 17) 135( l),C(33)-Sn(2)-C(37) 133( l)'], in keeping with both the stericdemands of the ligands and the accepted ideas of isovalentrehybridations.' ' The sum of the equatorial angles about themetal [352, 353" for Sn(1) and Sn(2), respectively] is, how-ever, more consistent with the proposed trigonal-bipyramidalgeometry (360") than a tetrahedral one (328.5').The atoms ofthe two BO, units exhibit large thermal displacements pre-cluding unambiguous analysis of the bonding in this part of themolecule. The B-0 bond lengths in the bidentate boronateunits CB(2)-O(3) 1.48(4), B(2)-O(4) 1.43(4), B(3)-O(5) 1.41(4),B(3)-O(6) 1.38(4) A] are all similar and are within the rangecited for trigonal BO? species (1.28-1.43 A).22 Direct compari-son can be made with the equivalent bonds in the parentphenylboronic acid (1.36, 1.38 A).,, In the unidentate ligandstwo distinct B-0 bonds are suggested, one similar to thosealready described [B( 1)-0(2) 1.47(4), B(4)-O(8) 1.39(3) A]while the other [B(l)-0(1) 1.20(3), B(4)-O(7) 1.28(3) A] isshorter and is more like the B==O found for B,O, in the gasphase [ 1.20(3)].24 Interestingly, the oxygen atoms involved inthese short B-0 bonds [O(l), 0(7)] are the only oxygen atomsnot involved in hydrogen bonding (see below).In addition, theSn-0 bonds involving the same oxygen atoms, which are axialand hence expected to be relatively long, are the same length asthe equatorial Sn-0 linkages. Collectively, these data suggestthat one of the oxygen lone pairs on each of O( 1) and O(7) isdelocalised into the vacant p orbital on boron (introducingsome B=O character), and to a lesser extent into a vacant dorbital on tin.The involvement of lone pairs on the remainingoxygen atoms in a hydrogen-bonding network precludes thistype of interaction.The lattice structure of compound 5a is dominated by anextensive network of hydrogen bonds. Hydrogen bonds occurbetween BOH OB units in both an intramolecular [0(2)O(4) 2.74,0(8) O(6) 2.70 A] (Fig. 1) and intermolecularmanner [0(2) O(5) 2.70, O(3') 0(8) 2.67 A]. Theintermolecular network links molecules into a polymeric chain(Fig. 2), the latter adopting a helical conformation of fourmolecules per complete turn (Fig. 3). No hydrogen bondingbetween helical chains is observed.The second class of compound derived from the reaction ofSnBu',O with an arylboronic acid [equation (2), R = Ph 6a ormes 6b] is a more complex formulation.Spectra for 6a and 6bfollow parallel patterns, so only the data for 6b, for which acrystallographic analysis is available, are discussed in detail.The 19Sn NMR spectrum contains two distinct tin resonancesin 2: 1 ratio, with upfield chemical shifts typical of co-ordinationnumbers higher than four (6 -260.3, -278.5).,' The samJ . CHEM. soc. DALTON TRANS. 1992 3505Fig. 2hydrogen-bonded polymeric latticeThe unit cell of compound 5a viewed along a, showing theFig. 3fold helical nature of the polymer propagationThe unit cell of compound 5a viewed along c, showing the four-pattern is reflected in both the 'H and NMR spectra, whichindicate two types of But groups in the ratio 2 : l .Thedistinctions between the two Bu',Sn environments are clearlyminor, and the similarity of the Mossbauer q.s. data (2.31 mms - l ) to those for 5 suggests a similar cis-R,SnO, co-ordinationsphere. Integration of the alkyl and aryl protons establishes theSn: B ratio as 3: 1, while the IR spectrum of the compoundFig. 4 The asymmetric unit of compound 6b, showing the atomiclabelling. The But groups attached to Sn(1) (not shown) are severelydisordered, and could not be located with any consistency in theelectron-density maps. Thermal ellipsoids are at the 30% probabilitylevelrecrystallised from a non-co-ordinating solvent (e.g. lightpetroleum, CHCI,) reveals a sharp v(0H) at 3670 cm-I.On theother hand, recrystallisation from MeCN or acetone causes thev(0H) to broaden and lower in wavenumber (3480 cm-I),typical of a hydrogen-bonded OH group. In particular, recrystal-lisation from MeCN yields crystals of an adduct, formulated as(Bu',SnO),OB(mes)~H,O=2MeCN on the basis of the foregoingspectral data, along with microanalytical figures. Ostensibly,this formulation is suggestive of incorporation of one B-0 unitinto the six-membered Sn,O, ring of the parent oxide, solvatedwith both H 2 0 and MeCN. However, the crystallographicanalysis of the compound reveals a more complex formulation.The structure of compound 6b is shown in Fig. 4. The lowinitial crystal quality followed by decay of the crystal within theX-ray beam during data collection (ca.33% loss in the intensityof the monitor reflection by the end of data collection) have ledto large errors in the resulting geometric data, compounded bydisorder of the two Bu' groups on Sn(1). These appear as asmear of electron density in the Fourier maps, and attempts tocorrelate and refine carbon atom positions with peaks appear-ing within this smear failed to yield chemically consistentpositions. Invariably, the thermal parameters for such atompositions were excessively large, the atom positions movedirrationally, and new electron-dense positions emerged in theFourier difference maps. Despite these difficulties, the grossstructure shown in Fig. 4 confirms the empirical formulation,and can be viewed as being derived from the incorporation ofone RBO unit into the precursor Sn,O, heterocycle, yieldingan eight-membered Sn,BO, ring as previously suggested.Inaddition, this ring contains a central oxygen atom, generatingtwo four-membered Sn,O, rings and one six-memberedSn,BO, ring within the larger heterocycle. Notably, the six-membered Sn2B0, ring is the chemical inverse of that in 4. Allnine ring atoms are essentially coplanar [maximum deviationfrom mean plane: B(1) -0.10 A], with a pseudo-mirror planecontaining these atoms (also bisecting the two pairs of Bu'groups and dividing in two the mesityl ligand) only broken bythe two MeCN molecules which both lie above the ring plane.The molecule does possess a crystallographically impose3506 J.CHEM. SOC. DALTON TRANS. 1992mirror plane, orthogonal to the above pseudo-mirror, contain-ing Sn( l), O( l), B( 1) and all the atoms of the mesityl ligand.Given the hydrolytic relationship between compounds 4 and5 discussed earlier, the correct interpretation of the structure of6b rests on the assignment of hydrogen atoms to one or more ofthe oxygen atoms, i.e. are the elements of H,O present as a watermolecule or has it converted an M-0-M unit into two M-OHgroups (M = Sn or B) as in 5? Given the low quality of thecrystallographic data for this compound, location of therelevant hydrogen atoms in the Fourier maps proved im-possible. However, the positions of the two MeCN solventmolecules "(1) O(2) 2.87 A], which the IR data suggestinduce hydrogen bonding from the hydroxyl groups, leads us toposition one hydrogen atom on each of O(2) and O(2').Aschematic of our preferred formulation for both compounds 6aand 6b based on the structure of the latter is therefore as shown.R2HO P\ f OHRThe Sn-0 bond length data lend some support to the aboveinterpretation. All the Sn-0 bonds save Sn(2)-O(2) [and itssymmetry-related Sn(2')-0(2')] are in the range 2.04(2)-2.18(2) A, slightly longer than, but still comparable with, thosealready noted in compound 5a. On the other hand, Sn(2)-0(2),the nominally co-ordinate interaction between tin and thehydrogen-bonded hydroxyl group, is notably longer at 2.33(3)A. This bond, in which oxygen both co-ordinates tin andis involved in hydrogen bonding, is longer than examples ofnon-hydrogen-bonded hydroxyl groups involved in eitherterminal Sn-OH [e.g.(R,Sn),(OH),(p-0), R = (Me,Si),CH,2.032(7); 2 5 Sn(trop),(OH) (Htrop = 2-hydroxycyclohepta-2,4,6-trien-l-one), 1.974(6) A or bridging Sn-OH [e.g.SnPh,(OH) 2.197(5) 8, 27]. The compound { [(OH)Bu'-((',SiCH,)Sn],O}, also shows distinct terminal [2.016(8) A]and bridging [2.299(7) A] Sn-OH bonds.28The co-ordination spheres about all three tin atoms are, notunexpectedly, severely distorted, and this is most clearly seen indeviations of the axial 0-Sn-0 moiety away from the idealangle of 180". It would appear that the tin of the Bu',Sn(OH),unit [0(2)-Sn(l)-0(2') 149.8(8)"] is more affected than the tinof the nominal six-membered Sn,BO, [0(2)-Sn(2)-0(3)166( l)"].The angles within the four-membered Sn,(p-OH)-(p-0) rings are surprisingly similar to those in rings ofanalogous content, also incorporating five-co-ordinate tin. Forexample, the internal angles at Sn(l), Sn(2), 0(1) and O(2) incompound 6b [75.0(7), 72.3(9), 112.4(7) and 100(l)o, respec-tively] compare well with the analogous angles in {[(OH)(Cl)-Pr'Sn],O}, [74.7(6), 72.4(5), 113.8(8) and 98.9(6)"] 29 and~[(OH)BU'(M~,S~CH,)S~]~O}, [70.1(3), 73.4(3), 115.4(4) and99.9(3)", re~pectively].~' The across-ring Sn(1) Sn(2)separation (3.460 A) is, however, much longer than in(R2Sn),(p-0),, R = (Me,Si),CH (2.94 A), which is orange andmay involve weak Sn Sn interaction^.,^ Within the six-membered Sn,BO, sub-ring, the internal angles at 0(1) andO(3) [135(1), 134(3)"] are identical with those in the parent(Bu',SnO), [ 133( l)"],' but the internal angles at tin[0( l)-Sn(2)-0(3) 93( I)"] are significantly different due to theincrease in the co-ordination number at the metal from four tofive.The internal angle at trigonal boron [129(6)"] is also widerthan normally found, though the large error in this parameternegates confident analysis. In general, though, the ring angles inrelated planar six-and eight-membered heterocycles containingfour-co-ordinate silicon and three-co-ordinate boron, e.g.PhSSi,B03,'6*'7 Ph6Si2B204,' But4Ph,Si,B,04 " and Buqt-Me,FSi,O,, are all very close to the ideal tetrahedral ortrigonal values for silicon and boron, respectively.However,unlike 6b, significant angular distortions at two-co-ordinateoxygen are common, with internal angles at oxygen varyingbetween 118 and 168°.'7,'8The presence of Bu',Sn(OH), as a sub-unit of the structure ofcompound 6b is the first structural evidence for the existence of adiscrete organotin dihydroxide. While such species have beenclaimed in the p a ~ t , ~ ' * ~ l no crystallographic studies have beenreported, largely due to the instability of such species withrespect to the corresponding dehydration product, SnR,O. Therecently reported monomeric [R,Sn(OH)],O [R = (Me,Si),-or dimers of the same formulation, { [Bu'(Me,SiCH,)-Sn(OH)],0),,28 can be viewed as intermediate between thesetwo extremes.ExperimentalSpectra were recorded on the following instruments: JEOLGX270 ('H, 13C NMR), GX400 ("B, "'Sn NMR); PerkinElmer 599B (IR). Details of our Mossbauer spectrometer andrelated procedures are given elsewhere.,, The NMR spectrawere recorded as saturated CDCl, solutions at roomtemperature; "B and '19Sn chemical shifts are relative toBF,-OEt, and SnMe,, respectively.The compounds SnBu',Cl, and SnBu',O were prepared byliteratureSynthesis of Mesitylboronic Acid.-Mesit ylmagnesium brom-ide, from magnesium (3.7 g, 152 mmol) and mesityl bromide (30g, 151 mmol) in diethyl ether (100 cm3), and trimethyl borate(15.6 g, 150 mmol) were simultaneously added to stirred ether(200 cm3) at -78 "C.After ca. 75% of the reagents had beenadded, more solvent (100 cm3) was added to enable efficientstirring to continue. The mixture was allowed to warm to roomtemperature and stirring continued for 17 h.Water was thenadded to the slurry to hydrolyse the remaining methoxy groups,the mixture extracted with ether, and dried over anhydrousmagnesium sulfate. After solvent evaporation in uacuo, the solidresidue was recrystallised from chloroform-light petroleum(b.p. 4Ck60 "C) (1 : 1) to yield mesitylboronic acid as a colourlesscrystalline solid (8.1 g, 33%; m.p. 177 "C) [Found (Calc. forC,H,,BO,): C, 65.20 (65.90); H, 8.00 (8.00)%]. NMR: 'H, 6 2.25BOH) and 6.80 (s, 2 H, C,H,); 13C, 6 21.1 (p-CH,C,H,), 22.0(o-CH,C,H,), 127.2, 138.6, 139.6 and 143.5 (m-, 0-, p - c ofC6H2); ' 'B, 6 29.6 (br).(S, 3 H, p-CH,C,H,), 2.32 (S, 6 H, O-CH,C,H,), 5.09 (S, 2 H,Reaction of Di-tert-hutyltin Oxide and an Arylboronic acid.-Di-tert-butyltin oxide (1.0 g, 4 mmol) and phenylboronic acid(0.49 g, 4 mmol) were heated to reflux in benzene (30 cm3) andthe water generated in the reaction separated in a Dean andStark apparatus.After continued reflux for 17 h the solution wascooled and the solvent evaporated in vucuo to yield a whitesolid. Repeated recrystallisation from acetone yielded twofractions, one containing a mixture of compounds 4a and 5a,from which 5a crystallised on standing, the other 6a.2,2-Di- tert-butyl-4,6-diphenyl- 1,3,5- trioxa-2-stannadiborinane4a. NMR: 'H, 6 1.47 [s, 18 H, C,H,; ,J(Sn-H) = 99, 103 Hz],7.44 (m, 6 H, m-,p-H of Ph) and 8.1 1 (m, 4 H, o-H of Ph); I3C, 6(br); *19Sn, 6 - 127.8.Di-tert-butylbis[hydroxy(phenyl)boryloxy]stannane 5a.Found (Calc.for C2,H,,B204Sn): C, 50.70 (50.60); H, 6.50(6.35)%. NMR: 'H, 6 1.46s, 18 H, C,H,; ,J(Sn-H) = 101, 105Hz], 6.05 (s, 2 H, BOH), 7.44 (m, 6 H,m-,p-H of Ph) and 7.87 (m,4 H, o-H of Ph); 13C, 6 29.5 (C4H9), 127.7, 130.5, 134.2 (m-,p-,0-C of Ph); 'B, 6 26.3 (br); ' 19Sn, 6 - 106.4. '19Sn Mossbauer:i.s. = 1.46, q.s. = 2.81 mm s-'. IR: v(0H) 3250 cm-',2: 3 ~ ~ O - p ~ - o x o - t r i ~ [ b ~ k ( t e r t - h ~ t y l ) t i n ] 6a. Found (Calc. for29.4 (C4H9), 127.5, 130.5, 135.1 (m, 0-, p-C of Ph); "B, 6 26.3p-DioxophenjYborato- 1 : 2 ~ ~ 0 : 0'-di-p-hydroxo- 1 : 3 ~ ~ 0 J . CHEM. SOC. DALTON TRANS. 1992 3507C,,H, B05Sn,*2CH,CN): C, 42.80 (42.95); H, 7.20 (7.10);N, 2.75 (2.95)%.NMR: 'H, 6 1.38 [s, 36 H, C4H9, 3J(Sn-H) =100, 1061, 1.39 [s, 18 H, C4H9, ,J(Sn-H) = 100, 104 Hz], 7.28(m, 3 H, rn-, p-H of Ph) and 7.94 (m, 2 H, 0-H of Ph); ' ,C, 6 30.7(C4H9), 30.8 (C4H9), 126.8, 128.1, 135.4 (m-,p-, 0-C of Ph); "B,6 25.0 (br); "9Sn, 6 -261.8 and -277.8. '19Sn Mossbauer,Table I Crystallographic data for compounds 5a and 6b"5a 6bEmpirical formulaMrnl AhlA'./Ac', A3x = piY lCrystal systemSpace groupzDclgcmCrystal sizelmmP/cmF ( o wAbsorption factors/i,k,l limitsData collectedUnique data, 1 > 3a(l)No. variablesMaximum shift/e.s.d.Maximum, minimumresidualsie A-3R'C*,H3oB,O,Sn474.812.402(3)12.4O4( 3)15.787(9)90.090.0( 1)2428.5MonoclinicP2, (unique c)2b1.300.3 x 0.3 x 0.259.759681.01,0.960-13,13-13,-16 to 165392301 6144d0.01 60.39, -0.530.07 18C37H73BN205Sn3993.016.482(4)16.482(4)18.395(6)90.090.04997.2TetragonalP4,nm4'1.350.3 x 0.2 x 0.213.9920641.10,0.97&17, (rl7, &1934001257100- 0.0060.27, -0.210.0794' Details in common: data collected on a Hilger and Watts Y290 four-circle diffractometer at room temperature using Mo-Ka radiation (A =0.710 69 A); empirical absorption correction; 20 range 4-44".Twomolecules per asymmetric unit. Half a molecule per asymmetric unit(see Fig. 4). Refined in two blocks, each comprising the variables forone molecule of the asymmetric unit.Unit weights.i.s. = 1.20, q.s. = 2.36 mm s-'. IR: v(0H) 3680 (recrystallisationfrom light petroleum, CHCl,): 35 lObr cm-' (recrystallisationfrom MeCN or acetone).Using the same methodology and mesitylboronic acid asreagent, a solution mixture of compounds 4b and 5b wasobtained from which 5b crystallised on standing, along with 6b.2,2-Di-tert-butyl-4,6-dimesityl- 1,3,5-trioxa-2- stannadiborinane4b was only present as 16% of the mixture with 5b makingreliable assignments of the 'H and I3C NMR data tenuous.NMR: "B, 6 28.0 (br); lI9Sn, 6 - 131.6.Di-tert-butylbis[hydroxy(mesityl)boryloxy]stannane 5b.Found (Calc. for C,,H,,B,04Sn): C, 56.00 (55.85); H, 7.75(7.55)%. NMR: 'H, 6 1.49 [s, 18 H, C4H9, ,J(Sn-H) = 100,104Hz], 2.30 (s, 6 H, p-CH,C,H,), 2.39 (s, 12 H, o - C H ~ C ~ H ~ ) , 6.22(s, 2 H, BOH) and 6.82 (m, 4 H, m-CH,C,H,); I3C, 6 21.1(p-a3C,H,), 22.4 (O-m3C,H2), 29.4 (C4H9), 127.0, 137.1,139.3 (m-,p-, 0-C Of CH,C,H,); "B, 6 28.0 (br); ' I9Sn, 6 - 106.7.Il9Sn Mossbauer: is.= 1.37, q.s. = 2.66 mm s-'. IR: v(0H)3300 cm-I.2 : 3~~0-p-mesityldioxoborato-1 : 2 ~ ~ 0 : O'-p,-oxo-tris(tert-butyl)tin] 6b. Found (Calc. forC,,H,,BO5Sn3-2CH3CN): C, 44.80 (44.75); H, 7.55 (7.40); N,3.05 (2.80)%. NMR: 'H, 6 1.33 [s, 36 H, C4H9, ,J(Sn-H) = 101,1041, 1.39 [s, 18 H, C4H9, ,J(Sn-H) = 100, 104 Hz], 1.95Di-p-hydroxo-1 : 3 ~ ~ 0 ;(s, 6 H, CHSCN), 2.23 (s, 3 H, P-CH~C~HZ), 2.49 (s, 6 H,O-CH,C,H,) and 6.73 (S, 2 H, CH,C,H,); l3c, 6 21.1(p-m3C6H,), 23.5 (O-m3C,H2), 30.7 (C4H9), 39.2 (C4H9),126.5, 134.4, 139.7 (m-, p-, 0-C of CH3C6H,); "B, 6 26.5 (br);"'Sn, 6 -260.3 and -278.5.lI9Sn Mossbauer: i.s. = 1.16,q.s. = 2.31 mm s-'; IR: v(0H) 3670 (recrystallisation fromlight petroleum, CHCl,); 3480br cm-' (recrystallisation fromMeCN).Crystal Structures of Compounds 5a and 6b.-Details of thecrystal and experimental data relating to both compounds aregiven in Table 1. For both structures, scattering factors usedwere for neutral atoms,34 while the program suites used wereSHELX 86,35 SHELX 76 36 and DIFABS.,,Due to initial uncertainty in the crystal system, data forcompound 5a were collected in the ranges h 0-13, k - 13 to 13and 1 -16 to 16. Photographic data indicated that the spaceTable 2 Fractional atomic coordinates for compound 5ar0.0966(2)0.0545(3)0.3047(3)0.036 6(2)0.146 O(2)0.268 O( 1)0.218 7( 1)0.4 18 4(2)0.348 4(4)0.624 6(3)0.275 4( 1)0.423 4( 1 )0.552 7( 1)0.607 3(2)- 0.01 2 2(24)- 0.093 7( 25)- 0.153 5(30)-0.132 2(27)-0.054 l(28)0.010 6(26)0.401 5(23)0.497 7(26)0,573 8(27)0.606 O(33)0.530 l(33)0.432 5(29)0.158 l(32)Y0.081 5( 1)-0.120 8(3)0.154 3(3)-0.054 7(1)-0.106 l(1)0.225 9( 1)0.078 3(1)-0.403 3( 1)-0.203 7(3)-0.441 6(2)-0.234 l(1)-0.283 8( 1)-0.463 7(1)-0.352 3(1)-0.228 3(20)-0.250 4(23)-0.342 2(26)-0.408 2(27)-0.387 5(26)-0.297 5(22)0.164 8(18)0.242 l(23)0.246 7(23)0.168 O(25)0.083 9(32)0.089 8(25)0.027 2(28)z1.Ooo 000.900 O(2)0.927 8(3)0.954 O( 1)0.842 3( 1)0.997 2( 1)0.919 8(1)0.750 3(2)0.684 2(2)0.644 9(2)0.748 O( 1)0.668 6( 1)0.700 9( 1)0.593 3( 1)0.877 5( 18)0.939 2( 19)0.923 3(23)0.859 6(21)0.798 8(22)0.818 8(18)0.887 8( 15)0.901 8(19)0.858 3(18)0.802 5(21)0.734 6(27)0.828 7(19)1.120 7(23)X Y0.187 l(32) 0.117 2(29)0.234 3(30) -0.050 7(29)0.064 l(30) -0.027 2(29)-0.026 3(27) 0.196 9(24)0.016 4(31) 0.269 5(28)-0.1 19 3(28) 0.144 2(27)-0.038 3(31) 0.260 2(29)0.335 2(22) -0.096 7(18)0.409 8(24) - 0.070 4(20)0.409 O(30) 0.027 2(25)0.330 l(27) 0.103 l(28)0.257 6(22) 0.073 l(19)0.258 2(23) -0.019 8(19)0.725 8(23) -0.507 4(19)0.748 7(25) -0.594 2(20)0.846 l(27) - 0.654 2(25 j0.908 5(27) -0.632 l(22)0.885 7(30) -0.556 5(26)0.800 l(27) -0.492 O(26)0.298 O(28) -0.523 O(24)0.228 2(27) -0.483 5(25)0.237 8(38) -0.542 3(36)0.358 2(26) -0.622 O(23)0.473 4(32) -0.345 9(28)0.379 9(27) -0.305 8(27)0.530 O(29) -0.437 5(27)0.544 l(27) -0.253 8(24jz1.173 2(25)1.099 5(24)1.163 7(26)0.960 3( 18)0.902 5(24)0.933 8(22)1.052 7(21)0.592 8(16)0.579 O(16)0.526 4(23)0.542 8(20)0.613 3(16)0.653 4(17)0.631 3(16)0.684 O(19)0.671 5(21)0.609 l(19)0.550 O(23)0.567 3(20)0.71 1 4(19)0.648 6(21)0.791 5(27)0.679 7(20)0.874 l(23)0.925 3(23)0.9147(24)0.854 7(213508 J.CHEM. SOC. DALTON TRANS. 1992Table 3 Selected bond lengths (A) and angles (") for compound 5aC(4)-Sn( 1)-O( 1)C( 13)-Sn( 1)-0(4)O(3)-Sn( 1)-0(4)C( 17)-Sn( 1)-0(4)0(2FB(1)-0(1) c( 1 t-w 1 )-0(2)C( 7)-B( 2)-O( 3)B( 1)-O( 1)-Sn( 1)O( 7)-Sn(2)-0(6)O( 5)-Sn(2)-0(7)C( 3 3)-Sn(2)-0( 7)C( 37)-Sn(2)-0(7)0(6)-B(3)-0(5)C( 2 1 )-B( 3)-O( 6)C(27)-B(4)-0(7)B( 3)-O(6)-Sn( 2)1.99( 2)3.462.16(4)1.20(3)1.61(4)1.43(4)1.97(2)2.75(2)2.19(3)1.41(4)1.52(4)1.39(3)92.0(7)54.6(6)1 11.4(9)11 l(2)107(1)120( 3)124(3)140(2)90.0(7)145.7(6)102(1)102(1)112(2)128(3)124( 2)114(2)C( 13)-Sn( 1 )-O( 1)C( 17)-Sn( 1 )-O( 1)O( 1)-Sn( 1)-0(3)C( 17)-Sn( 1 )-C( 13)C( 1)-B( 1)-O( 1)C(4)-B(2)-0(3)C(7)-B(2)-0(4)B(2)-0(4)-Sn(l)C( 3 3)-Sn(2)-0(6)C(S)-Sn(2)-0(6)C(37)-Sn(2)-0(6)C(37)-Sn(2)-C(33)C( 2 1 )-B( 3)-O( 5 )0(8)-B(4)-0(7)C(27)-B(4)-0(8)B(4)-0(7)-Sn(2)1.97(2)2.78(2)2.18(3)1.47(4)1.48(4)1.36(5)1.99(2)3.472.19(4)1.38(4)1.28(3)1.5 1 (4)lOl(1)lOl(1)1 46.3 (6)135( 1)129(3)103(3)133(3)120(2)110.3(9)55.9(6)109(1)133( 1)120(3)118(2)1 1 S(2)140( 2)Table 4 Fractional atomic coordinates for compound 6bX0.2 199(2)0.2982( 1)0.2184(11)0.3121(14)0.2673( 15)0.2 108(36)0.2092(23)0.1539(18)0.1050(22)0.1539(22)0.1993(24)0.1980(28)0.2501(21)0.26 17( 19)0.3122(17)0.2602(20)0.2929(28)0.2964(41)0.178 l(27)0.4270(23)0.4784(27)0.4252(24)0.4498(29)0.0782(25)0.93 l(26)0.1088(27)Y0.2199(2)0.1344( 1)0.2184(11)0.13 18( 13)0.1610( 14)0.2108(36)0.2092(23)0.1539( 18)0.1050(22)0.1 539(22)0.1993(24)0.1980(28)0.2501(21)0.26 1 7( 19)0.3 122( 17)0.0 103( 20)- 0.0220(27)-0.0397(39)0.0036(26)0.1701 (23)0.1387(27)0.2652(25)0.1338(30)0.3699( 27)0.4445(27)0.5166(29)z1 .m0.8432(2)0.8859( 14)0.9693( 14)0.738 6( 13)0.7068(41)0.6260(28)0.5944( 2 1 )0.6272(27)0.504 l(32)0.4678(29)0.3882(35)0.4982(32)0.58 16( 23)0.6 197(22)0.835 l(25)0.7621(23)0.8920(37)0.8 199(23)0.832 l(30)0.8978(25)0.8229(23)0.7580(28)1.5795(22)1.5694(22)1.5623(24)group has only one mirror plane (orthogonal to the mountedaxis), and that the Weissenberg axes were equal in length.Least-squares refinement of the unit-cell parameters (based on 12reflections with 8 in the range 12-16') upheld that two axes (aand b) were the same length within the bounds of experimentalerror and that the y angle was 90.0'.After processing thecorrected data the only systematic absence was in the 0,0,1subgroup of reflections. The reflection condition was itselfambiguous and of the two possibilities for an observedreflection, 1 = 2n and 1 = 4n, only the latter reflections wereintense. In addition, the volume indicated that there ought to beTable 5 Selected bond lengths (A) and angles (") for compound 6bSn(1 W ( 1 ) 2.10( 3) Sn( 1)-0(2) 2.17(2)Sn(2)-0( 1) 2.06( 1) Sn(2)-0(2) 2.33(3)Sn(2)-O(3) 2.04(2) Sn(2)-C( 10) 2.14(3)Sn(2)-C( 14) 2.2 l(4) 0(3)-B(1) 1.37(4)B(1 )-C(l) 1.48(8) c c 1 -cc2 1.27(5)Cc2-N( 1 ) 1.23(6)0(2kSn(lt-0(1)0(3)-Sn(2)-0( 1)C( 10)-Sn(2)-Sn( 1)C( 10)-Sn(2)-0(2)C( 14)-Sn(2)-0(1)C( 14)-Sn(2)-0(2)Sn(2)-0( 1)-Sn(2)Sn(2)-0(2)-Sn( 1)0(3)-B( 1 )-0(3)N( 1 bCc2-C~ 175.0(7)93U)1 lO(1)95V)118(1)90U)135(1)1 W )129(6)178(5)0(2)-Sn(2)-0( 1)O(3)-Sn( 2)-O( 2)C(lO)-Sn(2)-0(1)C( 10)-Sn(2)-0(3)C( 14)-Sn(2)-~( 10)C(14)-Sn(2)-0(3)Sn(2)-0( 1)-Sn( 1)B( 1 )-0(3)-Sn(2)C(1)-B(1)-0(3)72.3( 9)166(1)119(1)94( 1 )122( 1)95(2)1 12.4( 7)134(3)1 15(3)four molecules of C,,H,,B,O,Sn per unit cell.The space grouppossibilities were therefore P4,22, P4,22, P4,, P4,, P4,, P4,/m ofthe tetragonal system and P2, from the monoclinic class, and aPatterson synthesis was run on them all; P4,22 and P4,22 wereunlikely as they both require eight molecules per unit cell andthey both failed to yield any heavy-atom positions and hadunfavourable R(int) values of 0.28 23; P4,, P4, and P4, alsofailed to produce any heavy-atom positions but had morereasonable R(int) values of 0.1010.Although P4,/m managedto yield two tin positions (at 0.5, 0.5, 0.25 and 0.8215, 0.0171,0.000 with site occupancy factors of 0.25 and 0.50, respectively)and the map also contained another high peak with an intensityapproximately 80% of that given for the tin positions, and wasinconsistent with the available chemical evidence. The completestructure was solved, and subsequently refined, in space groupP2, [R(int) = 0.0851) with two molecules, identical structurallywithin the bounds of experimental error, per asymmetric unit.Hydrogen atoms were included at calculated positions [d(C-H)1.08 A] with fixed isotropic thermal parameters (0.05 81').Itwould appear that, as shown in the packing diagram (Fig. 3), thefour-fold helical hydrogen bonding found within this structureis responsible for the tetragonal pseudo-symmetry observed. Inthe final stages of refinement the atoms of both Sn(O,B), unitswere treated anisotropically. Atomic coordinates and selectedgeometric data are given in Tables 2 and 3, respectively. Theasymmetric unit, incorporating the atomic numbering schemeused in both the Tables and text, is shown in Fig. 1.The unit cell for compound 6b was determined from 12reflections in the 8 range 11-17'. Other experimental details aregiven in Table 1. The data collected showed systematic absencesh00, h odd, OkO, k odd, 00/, 1 odd, Okl, k + I odd and h01, h + 1odd, though the latter appears to be more apparent than realas no space group requires more than the first four absenceslisted without the need for additional conditions which were notfound.The apparent hOl condition is probably a consequenceof the high degree of pseudo-symmetry in the molecule. Of theavailable tetragonal space groups, Palm, PJn2 and P4,nmnyielded heavy-atom positions from the Patterson syntheses innumbers and positions inconsistent with the chemical formula.The structure could be solved in both P4, and P4,nm, withgenerally the same limitations in both cases [the But groups onSn(1) could not be located in either space group], so the finaldata presented relate to the higher-symmetry option (P4,nm),which requires all the systematic absences (save h01, h + I odd).The But groups on Sn( 1) appeared as a smear of electron densityfrom which chemically consistent atom positions could not berefined.However, the spectral data for this compound and therequirements of the unit-cell volume leave no doubt surround-ing the existence of these two groups. In the light of thesedifficulties, the final stages of refinement only involveJ. CHEM. SOC. DALTON TRANS. 1992 3 509anisotropic treatment of the heavy-atom positions. Atomiccoordinates and selected geometric data are given in Tables 4and 5, respectively. The asymmetric unit, incorporating theatomic numbering scheme used in both the Tables and text, isshown in Fig.4.Additional material available from the Cambridge Crystallo-graphic Data Centre comprises H-atom coordinates, thermalparameters and remaining bond lengths and angles.References123456789101 11213Part 2, P. Brown, M. F. Mahon and K. C. Molloy, J. Organomet.Chem., 1992,435,265.K. C. Molloy, Adv. Organomet. Chem., 1991,33,171.P. Brown, M. F. Mahon and K. C. Molloy, J. Chem. SOC., Chem.Cummun., 1989,1621.M. F. Mahon, K. C. Molloy and P. C. Waterfield, J . Organumer.Chem., 1989,361, C5.P. Brown, K. C. Molloy and M. F. Mahon, in Chemistry andTechnulugy of Silicon and Tin, eds. V. G. Kumar Das, S. W. Ng andM. Gielen, Oxford Science Publications, Oxford, 1992, p. 559.P. Brown, M. F. Mahon and K. C.Molloy, J. Chem. SOC., DaltonTrans., 1990,2643.C . L. Christ and J. R. Clark, Phys. Chem. 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Kandil and A. L. Allred, J. Chem. SUC. A, 1970,2987.34 International Tables for X-ray Crystallography, Kynoch Press,35 G. M. Sheldrick, SHELX 76, A program for crystal structure36 G. M. Sheldrick, SHELX 86, A program for the solution of crystal37 N. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983,39, 158.131, 557.Chem. Commun., 1990,1116.3636.50.1983,254,23.Chem., 1984,267,237.Birmingham, 1974, vol. 4.determinations, University of Cambridge, 1976.structures, University of Gottingen, 1986.Receioed 6th July 1992; Paper 2/03527
ISSN:1477-9226
DOI:10.1039/DT9920003503
出版商:RSC
年代:1992
数据来源: RSC