J. CHEM. SOC. DALTON TRANS. 1992 3189Solid-state and Solution Studies of Tungsten(v1)Organoimidoalkoxides tWilliam Clegg, R. John Errington" and Carl RedshawDepartment of Chemistry, The University of Newcastle upon Tyne, Newcastle upon Tyne, NE7 7RU, UKThe arylimidoalkoxides, [W(NC,H4Me-4)(0R),] (R = Me or Pr') have been shown by X-ray diffractionstudies to adopt binuclear, alkoxide- bridged structures in the solid state. The alkoxide bridges areasymmetric [2.072(7) and 2.1 81 (6) A, R = Me; 2.029(4) and 2.243(3) A, R = Pri] and coplanar with theterminal arylimido ligands, the longer W-0 bonds being trans to the short WEN bonds [1.749(8) A,R = Me; 1.738(4) A, R = Pri]. Proton NMR studies show that these structures are dynamic in solution,although much less so than their 0x0 analogues.The bimetallic imidoalkoxide, [{W(NC,H,Me-4) -(OC6Hll)5Li,C~(C,Hl10H)}2]~C6Hl,0H, obtained from an attempted preparation of [W( NC,H,Me-4) -(OC6Hll)4], has been shown by a single-crystal X-ray diffraction study to have a dimeric structureanalogous to the known rhenium oxoisopropoxide, [{ReO(OPr'),Li,Cl(thf )},]-2thf (thf =tetrahydrofuran). A tungsten (v) imidochloroalkoxide, [N Bun4] [W,( N Ph),(p-OMe) (p-CI),Cl4] has alsobeen crystallographically characterised and has a distorted confacial bioctahedral structure in whichone of the bridging chlorines is trans to both terminal imido groups and the W-W distance is2.695( 1 ) A.The successful use of organoimido ancillary ligands to provideelectronic flexibility and steric control in the design ofhomogeneous alkene metathesis catalysts and the involvementof organoimido species in industrially important catalyticammoxidation processes has stimulated synthetic efforts intransition-metal organoimido chemistry during recent years.3Our interest in 0x0 and organoimido compounds of the earliertransition metals prompted us to synthesise a range of tungstenalkoxo derivatives in order to investigate and compare theirsolution properties. We have described the solid-state structuresand solution dynamics of oxoalkoxides [WO(OR),] in aprevious paper,, and we report here our results concerning theanalogous organoimidoalkoxides [ W(NR)(OR'),].Of the previously reported tungsten imidotetraalkoxides[W(NPh)(OR),] (R = Me lY5 Et 2,6 But 3597), [W(NMe)-(OMe),] 4,' and [W(NBu')(OR),] (R = Pr' 5, But 6),8 only 1has been crystallographically characterised.This imprecisedetermination showed a dimeric, centrosymmetric structuresimilar to those of the p-tolylimidochloroanalogues, [ W(NC,H4Me-4)CI4] 7, [WO(OMe),] 8 and[WO(OC6Hl 1)4] 9 respectively. In all of these structures, thestrongly n-bonding terminal organoimido or 0x0 ligands arecoplanar with the bridging chloro or alkoxo ligands and trans tothe longer bonds in the asymmetric bridges. This is consistentwith the large trans influence usually observed for these ligandsin do c~mplexes.~ The 'H NMR spectra reported for 1,2 and 4indicate that dimeric structures persist in solution, whereas for3,5 and 6, spectra are consistent with mononuclear structures.Our studies of the oxoalkoxides [WO(OR),] have shownthat for primary and secondary alkoxides the dimeric struc-tures observed in the solid state are dynamic in s o l ~ t i o n .~ Theexact nature of the dynamic processes involved depends on thesteric requirements of the alkyl group. When R = Pr', amonomer/dimer equilibrium exists in solution but for R = Meor Et dissociation into monomers does not occur duringintramolecular alkoxide exchange. By comparison, Bradley etal." have found the single-line 'H NMR spectrum ofand oxoalkoxo1- Supplementary data available: see Instructions for Authors, J. Chem.SOC., Dalton Trans., 1992, Issue 1 , pp. xx-xxv.[WO(OBu'),] to be invariant down to 193 K, showing that thetert-butyl group is too bulky to allow dimerisation with aconcomitant increase in the co-ordination number of tungstenfrom five to six.These dynamic alkoxo complexes provided an opportunity tocompare the relative trans effects of 0x0 and organoimidoligands in [W(E)(OR),] compounds (E = 0 or NR).Since wehad already structurally characterised the chloro complexes[{W(NC6H4Me-4)C1,},] and [W(NC,H4Me-4)CIS] - , l wechose to prepare a range ofp-tolylimido alkoxides and comparetheir solid-state and solution properties with those of analogousoxoal koxides.Results and DiscussionThe arylimidoalkoxides were prepared from [W(NC6H,Me-4)-Cl,] by literature Hence, [W(NC6H,Me-4)-(OMe),] 10 was obtained using Bu'NH2-MeOH, whereasmetathesis with LiOPr' was used for [W(NC6H,Me-4)-(OPri)4] 11 to avoid the formation of an amine adduct.However, an attempt to obtain [W(NC6H,Me-4)(0C6H1 1)4]12 from the chloride 7 and lithium cyclohexoxide resulted in theisolation of the mixed-metal alkoxide [( W(NC,H,Me-for X-ray diffraction were grown from acetonitrile (10 and 11) orby slow diffusion of hexane into a tetrahydrofuran (thf) solution4)(0C6H 1 1)sLi2C1(C6H1 10H)}2]=C6H1 10H 13.Singlecrystals(13).C(4)Fig. 1atoms are omitted from all structure diagrams for clarity)A view of the molecular structure of complex 10 (Hydroge3190 J. CHEM. SOC. DALTON TRANS. 19927)UC(22)Fig. 2 A view of the molecular structure of complex 11Table 1 Selected bond lengths (A) and angles (”) for complex 10w-O( 1) 2.072( 7) w-O(2) 1.922(6)W-0(3) 1.886(8) W-0(4) 1.898(6)O( 1 )-C( 1) 1.438( 15) 0(2)-C(2) 1.383( 13)0(3)-C(3) 1.442(14) 0(4)-C(4) 1.41 l(14)N(5)-C(5 1) 1.394( 12)W-N(5) 1.749(8) W-O( 1’) 2.18 l(6)O( l’)-W-O(2)0(2)-W-O( 3)0(2)-W-0(4)0(1’)-W-N(5)0(3)-W-N(5)0(3)-W-O( 1)N(5kW-0( 1)O( 1 ’)-w-O( 1)w-O( 1)-W’W-O(2)-C(2)W-O(4)-C(4)82.2(2)88.8(3)165.8(3)168.2(3)1 02.7( 4)7 1 3 3 )160.1(3)96.8(3)108.5(3)130.1(6)138.0(7)O( 1 ’ )-W-0(3)O(l’)-W-O(4)O( 3)-W-0(4)O( 2)-W-N( 5 )0(4)-W-N(5)0(2)-W-O( 1)W’-O( 1 )-C( 1)C( 1 )-0(1)-W0(4)-W-O( 1)W-O(3)-C(3)W-N( 5)-C( 5 1)Symmetry operation for primed atoms: 1 - x, 1 - y , 1 - i.88.9(3)83.7(3)93.0(3)95.9(3)9733)85.2(3)88.4(3)120.1(7)1 25.1 (7)126.8(7)174.1(7)Table 2 Atomic coordinates for complex 10x0.428 12(4)0.398 9(7)0.260 8( 14)0.564 6(6)0.541 3(13)0.516 3(9)0.553 2( 14)0.326 9(8)0.181 O(12)0.280 O(8)0.169 l(10)0.030 6( 12)- 0.080 2( 13)-0.053 7( 13)0.086 8( 12)0.197 7(13)- 0.172 6(22)Y0.422 32(3)0.448 7(6)0.442 9( 13)0.286 7(6)0.167 2(11)0.427 3(6)0.315 4(12)0.583 9(6)0.627 4( 13)0.315 7(7)0.221 7(10)0.249 4(12)0.157 6(15)0.033 9( 13)0.008 3( 11)0.1009(11).0.071 7(16)0.406 67(3)0.540 O( 5 )0.581 3(9)0.443 6(5)0.485 2(9)0.296 9(5)0.243 3(8)0.385 6(5)0.373 8(10)0.386 4(6)0.376 2(7)0.403 5(9)0.392 5( 10)0.354 5(9)0.326 5(9)0.336 2(9)0.347 8( 14)Solid-state Structures of [W(NC6H,Me-4)(0Me),] 10,[W(NC6H4Me-4)(0Pri),] 11 and [(W(NC6H4Me-4)-(OC6Hl 1)5LiZC1(C6H1 10H))2]*C6Hl 1 0 H 13.-As expected,the binuclear imidoalkoxide compounds 10 and 11 adoptcentrosymmetric distorted edge-shared bioctahedral geometriesanalogous to the phenylimido compound 1 and the 0x0-alkoxides [WO(OMe),] and [WO(OC6Hl 1)4].The structuresare shown in Figs. 1 and 2 with relevant bond distances andangles in Tables 1 and 3 and atomic coordinates in Tables 2 and4 respectively.The short WEN distances and the large WNC angles areTable 3 Selected bond lengths (A) and angles (”) for complex 11w-O( 1) 2.029(4) w-O(2) 1.927(3)W-0(3) 1.905(4) W-0(4) 1.9 14( 5 )W-N 1.738(4) W-O(1’) 2.243(3)O(1)-C(11) 1.461(8) 0(2)-C(21) 1.381(7)0(3)-C(31) 1.417(8) 0(4)-C(41) 1.364( 1 1)N-C( 5 1 ) 1.397(6)O( 1)-W-0(2)O(2)-W-O( 3)0(2)-W-0(4)O( 1 kW-NO(3)-W-NO(1)-w-O(1’)w-O( 1 )-W’w-O( 2)-C( 2 1 )W-O(4)-C(41)0(3)-W-0(1’)N-W-O( 1’)89.8( 1)164.0(2)84.1(2)99.8(2)97.1(2)69.9( 1)81.8( 1)16932)110.1(1)132.1(3)137.4(4)O( 1)-W-0(3)O( 1)-W-0(4)0(3)-W-0(4)0(2)-W-NO(4 jW-N0(2)-W-0(1’)0(4)-W-O( 1’)w-O( 1 )-c( 1 1)C(l1)-O(1)-W’W-O(3)-C(3 1)W-N-C( 5 1)Symmetry operation for primed atoms: 1 - x, 1 - y, 1 - z.9 1.9(2)159.3( 1)88.7(2)98.2(2)1 OO.7(2)83.9( 1)89.8( 1)130.0(3)119.7(3)1 38.3( 5 )177.4(4)Table 4 Atomic coordinates for complex I IX0.460 17(2)0.378 2(3)0.243 2(6)0.107 8(6)0.244 l(8)0.577 8(4)0.616 4(7)0.569 6(9)0.786 7(9)0.395 2(4)0.264 3( 12)0.277 4(25)0.240 O(20)0.599 7(4)0.597 2(8)0.755 2(9)0.522 1 (10)0.312 4(4)0.198 4(5)0.205 l(7)0.089 9(8)-0.031 l(7)-0.034 9(7)0.078 6(7)- 0.157 6(9)Y0.575 88(2)0.502 4(3)0.485 O(6)0.629 2(7)0.385 5(7)0.376 4(3)0.317 6(6)0.201 8(8)0.255 O(9)0.761 l(4)0.900 4(8)0.996 2( 12)0.964 7( 1 1)0.612 l(4)0.723 9(9)0.701 7(10)0.748 2( 12)0.633 2(4)0.676 l(5)0.581 8(7)0.621 3(8)0.757 O(8)0.850 6(7)0.813 5(7)0.800 3( 10)Z0.631 32(2)0.521 O(2)0.531 5 ( 5 )0.529 7(7)0.620 9(6)0.679 2(3)0.780 7(5)0.808 8(7)0.782 7(8)0.560 l(3)0.561 8(7)0.621 l(16)0.460 2(9)0.697 8(3)0.753 8(6)0.750 O(7)0.864 O(7)0.735 3(3)0.822 2(4)0.902 8(5)0.989 3(6)0.996 3(5)0.915 7(6)0.829 9(6)1.090 7(7)similar to those we have observed in other tungstenp-tolylimidocompounds 9 * 1 ’ and also to those in structurally characterisedphenylimido a l k o x i d e ~ ~ , ~ , ’ ~ [except for 1 for which a ratherimprecise value of 1.61(4) A was reported].We can thereforeassign a W-N bond order of close to three and address thequestion of whether, and to what extent, the W-N bond order isreduced from three by competitive W-OR 7c bonding. Assumingfor the moment that this would be reflected in the structuralparameters of the imido ligand, then variation of the ligand set inoctahedral complexes of the type [ W(NR)L,L’] might beexpected to provide structural evidence for such competition formetal 7c orbitals.We have now structurally characterised a rangeofp-tolylimidochloro and alkoxo complexes and the W-N bondlengths and WNC angles are collected in Table 5 forcomparison. Alkoxides are generally regarded as better TC donorsthan chloro ligands, so greater TC donation from the alkoxoligands might be expected to result in longer W-N distances andsmaller WNC angles. Although the bond lengths in Table 5might at first appear to follow this trend, the differences are smalland are not likely to be significant given the standard deviations.If we now turn our attention to the alkoxide ligands, it i3191 J. CHEM. SOC. DALTON TRANS. 1992Table 5 Tungsten-nitrogen distances and WNC angles in p-tolylimido tungsten complexesCompound[ { (NC6H4Me-4)C14 ) 21[ P( CH Ph)Ph 3] [W (NC,H4Me-4)C1 5 ]W-NjA1.7 12( 18)1.74 l(4)1.709(11)[W(NC6H,Me-4)Cl,(thf)] 1.711(7)[{ W(NC6H4Me-4)(0Me)4)21 1.749(8)I 1 [{ W(NC6H4Me-4)(0Pri),)z] 1.738(4)13 [{W(NC6H4Me-4)(0C6H,,),Li2CI(C,H, IOH)}2]*C6H,OH 1.746(6)WNC/"177.3(15)170.8(5)173.5( 12)177.4(4)174.1(7)177.4(4)1 7 5.6( 5 )Ref.91 lal l b1 laThis workThis workThis workTable 6(OR),} 2 1Torsion angles EEW-O-C in dimeric alkoxides [{W(E)-Compound E R Torsion angle/"to C( 1) to C(2) to C(3)8 0 Me -163.9 152.2 53.5-162.8 152.2 54.29 0 C6H1, -42.1 -42.1 -67.710 NC6H4Me-4 Me 11.5 -30.3 -48.9I 1 NC,H,Me-4 Pr' -44.0 - 12.8 -47.9possible that their orientation and W-0 bond lengths mightreveal any W-OR x bonding.We have calculated the O=W-0-C torsion angles in tungsten oxoalkoxides, [WO(OR)4],4and in Table 6 these are combined with the analogousN=W-0-C torsion angles for 10 and 11.Using a labellingscheme as shown in the diagram below, values of 0 or 180" areoptimum for x interaction with d,, while +90" is ideal forinteraction with d,, or d,, orbitals, On inspection of Table 6 itcan be seen that in each of the imidoalkoxides 10 and 11 one ofthe trans axial alkoxo ligands is oriented to enable preferential xinteraction with the d,, orbital. This is also the case for theoxomethoxide 8, but in the oxocyclohexoxide 9, perhaps forsteric reasons, it is the equatorial, terminal alkoxo group whichis best oriented for x interaction with the metal (via the d,,orbital).We are therefore unable to reach any firm conclusionsregarding the relative degrees of W-E x bonding in these 0x0and organoimido compounds by considering the bond lengthsand orientations of the terminal ligands.However, the NMRstudies discussed in the next section demonstrate that thesubstitution of an organoimido group for an 0x0 ligand doeshave a significant effect on the lability of this type of binuclearcomplex. We were therefore interested to see if the different transeffects of 0x0 and organoimido ligands might be reflected in thebond lengths and angles around the alkoxide bridges. Table 7shows a collection of parameters for the bridging region of the0x0- and organoimido-alkoxides. The longer W-0 bond transto the 0x0 or imido ligand is the one most likely to break in anysolution dynamic process.We shall discuss the comparativesolution behaviour of these molecules in the next section, butpoint out here that the imidomethoxide 10 has the shortestW-O,,,,, and the longest W-OCi, bond lengths, whereas theimidoisopropoxide 11 has similar bridging dimensions to theoxomethoxide 8. In fact, if we define A as the difference betweenW-O,,,,, and W-OCi, to reflect the strength of the bridgingFig. 3 A view of the molecular structure of complex 13. In this Figureand in Fig. 4, organic groups are represented by line drawings for clarityinteractions (where a larger A implies a more labile dimer), thenA is the same (0.21 8,) for all except the imidomethoxide 10 (0.11A).These results show that the bridging interactions in thesecompounds are determined by a combination of the lransinfluence of the strongly x-bonding ligand (E) and the stericrequirements of the bridging alkoxide. For the less bulkymethoxides, the greater trans influence of the 0x0 ligand resultsin a longer W-O,,,, in 8, whereas in the secondary alkoxidessteric effects become significant, resulting in similar bridgingW-0 distances for 9 and 11. On this basis, we would expect 10to be the least dynamic of these compounds in solution, and thisis borne out by our NMR studies.The stronger trans influence of the 0x0 ligand in 8 comparedwith the p-tolylimido ligand in 10 is in accord with previousexpectations where the order of trans influence has been given asnitrido > 0x0 > i m i d ~ , ~ but it should be noted that in thecrystal structure of the compound [ W (NBu')( 0)Cl (bipy)](bipy = 2,2'-bipyridine) l 3 the W-Nbipy bond trans to NBu' is0.022 8, longer than that trans to the 0x0 ligand.This isprobably due to the inductive effect of the Bu' group and servesto illustrate the electronic flexibility of the NR group in co-ordination chemistry.We were keen to obtain the crystal structure of the cyclo-hexoxo derivative 12 for a direct comparison with the 0x0analogue 9, but our efforts to prepare 12 by treating[W(NC,H,Me-4)C14] with LiOC,H, , resulted instead in theformation of the mixed-metal alkoxide 13. A view of themolecule is shown in Fig. 3 and bond distances and angles andatomic coordinates are given in Tables 8 and 9.This dimericspecies can be viewed as resulting from the incorporation ofLiCl into the notional heterometallic imidoalkoxide [ W(NC,-H4Me-4)(0C,H, 1)5Li(C6H , ,OH)] and is structurally analo-gous to the previously reported l4 oxoisopropoxide of rhenium[{Re0(0Pr'),Li2C1(thf)},]~2thf 15 shown in Fig. 4. A recentreview l5 reflects the increasing interest in heterometallicalkoxides, and the structure of a related halide-free sodiumtungsten oxoethoxide [{ WO(OEt),Na(EtOH),},] 16 has alsobeen described.16 The trinuclear MM', cores present in thes3192 J. CHEM. SOC. DALTON TRANS. 1992Table 7 Bridging parameters in dimeric alkoxides [{ W(E)(OR),},]Compound E R W-ocisiA ~ - 0 t r o n s i A A el” w-w/A Ref.8 0 Me 2.029( 7) 2.254(7) 0.21 (av.) 110.3(2) 3.517 49 0 C6H1 1 2.044(4) 2.250(4) 0.2 1 110.9(2) 3.539 410 NC,H,Me-4 Me 2.072(7) 2.18 l(6) 0.1 12.035(6) 2.230(6) 11 1.0(2) 3.5181 0 8 3 3) 3.453 This work11 NC6H,Me-4 Pr’ 2.029(4) 2.243( 3) 0.2 1 1 10.1( 1) 3.504 This workTable 8 Selected bond lengths (A) and angles (”) for complex 13W-N( 1)W-0(3)W-O( 5 )N(l)-C(11)0(3)-C(3 1)0(4)-Li( 2)0(5)-Li( 1)0(6)-Li( 1)CI-Li( 1)CI-Li( 1’)0(7)-C(7 1)1.746(6)1.904(4)1.976(4)1.403(9)1.442(9)1.926(12)1.978( 13)1.98 1 (12)2.439( 13)2.327( 14)1.446( 10)N( 1EW-0(2)0(2)-W-0(3)0(2)-W-0(4)N(lFW-0(5)0(3)-W-O( 5)N( 1 )-W-O( 6)0(3)-W-0(6)O( 5)-W-0(6)W-O(4)-c(41)W-0(2)-€(2 1)C(41)-0(4)-Li(2)W-O(5)-Li( 1)C(6 1 )-O(6)-Li( 1)C(61)-0(6)-Li(2)Li( 1 )-Cl-Li( 2)Li(2)-CI--Li( 1’)0(5)-Li( 1)-C10(5)-Li( 1)-Cl’Cl-Li( 1)-Cl’0(4ELi(2)-Cl0(4)-Li( 2)-O( 7)Cl-Li(2)-0(7)W-0(6)-€(61)99.4(2)90.3(2)163.5(2)9 7.8 (2)164.1(2)174.2(2)85.3(2)78.9(2)128.6(5)124.1(3)128.3(5)101.8(4)122.3(3)122.2(6)120.8(4)70.3(4)1464 5 )122.5(7)122.6(5)1 17.0(5)1 19.9(8)97.3(4)97.7(5)N( 1 )-W-0(3)N( 1)-W-0(4)0(3)-W-0(4)O( 2 )-W-0 ( 5 )0(4)-W-0(5)0(2)-W-0(6)0(4)-W-0(6)W-N( 1 )-C( 1 1)W-O(3)-C(3 1)W-0(5)-€(51)W-O(4)-Li(2)C(51)-0(5)-Li( 1)W-O(6)-Li( 1)W-O(6)-Li( 2)Li( 1)-0(6)-Li(2)Li( 1)-Cl-Li( 1’)0(5)-Li( 1)-0(6)O(6)-Li( 1 )-C10(6)-Li( 1 )-Cl’0(4)-Li(2)-0(6)0(6tLi(2)-Cl0(6)-Li(2)-0(7)Li(2)-0(7)-C(71)Symmetry operation for primed atoms: 1 - x, 1 - y, - z .1.9 12(5)2.005(5)2.097(4)1.428(8)1.43 1( 10)1.45 l(9)1.988( 14)2.417(12)1.962( 12)1.43 1 (7)9 7.8 (2)97.0(2)88.6(2)90.5(2)86.2(2)8 5.5 (2)78.1(2)1 7 5.6( 5 )132.5(5)102.1 ( 5 )13 1 S(4)126.0(5)9734)96.9(4)89.6(5)82.7(4)8 1.7(5)95.7(5)137.8(7)8 2.6( 5 )9 6.2( 5 )143.2(7)137.3(6)c;Fig.4drawn using coordinates from ref. 14A view of the molecular structure of [(ReO(OPr’),Li,Cl(thf)),lcompounds are represented diagrammatically above by (a), (b)and (c) and it is readily apparent that a considerable variation inmetal and ligand set can be tolerated by this basic structuralunit. The structural parameters in the MOs octahedra (M = Wor Re) are very similar, and in all three cases the W-0 bondlengths trans to E (E = NC6H4Me or 0) are somewhat shorterthan in the binuclear compounds discussed above or in the thfadduct [W(NC6H,Me-4)C14(thf)] [2.237(6) A].’ lo The reasonfor the lack of any significant trans influence from the multiplybonded terminal ligands in this type of heterometallic structureis not obvious.The presence of an extra non-co-ordinateddisordered alcohol in 13 can be rationalised by hydrogenbonding between O(7) and O(8) (0 0 distance 2.720 A),but in the rhenium isopropoxide 16 this type of interaction isnot present and the extra thf molecules are simply occupyingspace in the lattice as solvent molecules of crystallisation.Solution H NMR Studies of’ Organoimidoalkoxides[W(NC6H,Me-4)(0R),].-We invariably found the initialproducts from the attempted preparations of these alkoxides tobe mixtures of compounds.as has previously been noted for thephenylimido compound L5 In most cases, however, carefulrecrystallisation provided samples of single compounds whichwere sufficiently pure for ‘H NMR investigations.The ‘H NMR spectrum of the methoxide 10 is shown in Fig.5. The methoxide region contains a well resolved 2: 1 : 1 pattern(in addition to a few minor impurity peaks) consistent with thJ. CHEM. SOC. DALTON TRANS. 1992 3 193Table 9 Atomic coordinates for complex 13Atom X Y0.563 94(3)0.685 5 ( 5 )0.777 l(6)0.881 3(7)0.971 6(7)0.964 4(7)0.859 8(8)0.767 6(7)1.063 4(8)0.528 6(4)0.533 2(6)0.427 2(7)0.429 8(8)0.544 6(9)0.653 4(8)0.648 37)0.441 O(4)0.441 3(7)0.403 2(8)0.276 7( 10)0.I88 8(9)0.225 O(9)0.355 l(8)0.563 4(4)0.666 8(6)0.665 O(6)0.773 3(8)0.777 5(8)0.774 O(7)0.383 04(2)0.334 7(5)0.294 l(5)0.326 3(7)0.284 l(7)0.211 l(7)0.182 l(7)0.221 3(6)0.168 9(9)0.243 7(4)0.154 9(6)0.113 2(7)0.019 l(7)-0.078 O(7)-0.035 9(7)0.058 2(6)0.425 9(4)0.458 8(7)0.374 3(8)0.376 5(10)0.496 O( 11)0.578 9(9)0.574 3(7)0.545 3(3)0.581 6(6)0.624 7(6)0.668 7(8)0.758 7(8)0.718 4(7)Z0.251 04(2)0.303 3(3)0.350 2(4)0.330 O(5)0.375 8(5)0.462 8(4)0.417 6(4)0.491 l(6)0.257 3(2)0.320 5(4)0.326 2(5)0.394 3(5)0.385 3(6)0.375 6(5)0.308 9(4)0.333 6(2)0.406 3(4)0.469 9(4)0.469 6(6)0.474 9(7)0.409 6(6)0.410 9(5)0.225 3(2)0.294 4(4)0.289 4(5)0.220 8(6)0.147 O(5)0.442 9(4)0.220 7(4)X0.665 8(7)0.655 l(4)0.775 7(6)0.776 l(7)0.900 2(9)0.955 3(8)0.957 O(8)0.830 8(7)0.426 5(3)0.314 2(5)0.311 7(7)0.191 8(8)0.090 4( 8)0.092 7(7)0.213 5(6)0.472 2(2)0.527 8(10)0.428 9(10)0.327 3(5)0.230 7(7)0.1 15 4(8)0.014 9(9)0.039 3(9)0.156 l(9)0.259 3(8)0.379 4(14)0.380 O(12)0.394 2(12)0.511 7(13)Y0.676 5(6)0.362 5(4)0.297 9(6)0.191 7(6)0.125 6(8)0.198 6(9)0.303 5(9)0.369 7(7)0.452 8(3)0.425 8(6)0.343 3(7)0.318 5(8)0.428 O(9)0.515 O(8)0.535 5(7)0.634 8(2)0.433 5(11)0.612 5(10)0.768 4(5)0.825 5(7)0.863 l(7)0.924 3(9)0.985 5(11)0.922 3(9)0.891 2( 11)1.074 6(9)1.037 5(10)1.021 9(9)0.991 6(9) -z0.152 4(4)0.148 5(2)0.125 l(4)0.098 O(5)0.064 6(6)0.001 6(6)0.028 7(6)0.061 5(5)0.181 5(2)0.199 6(4)0.149 6( 5 )0.165 9(6)0.153 7(6)0.200 8(6)0.186 O(5)0.030 3( 1)0.081 5(7)0.168 3(7)0.178 l(4)0.231 9(5)0.199 5(6)0.254 3(6)0.277 6(7)0.307 l(6)0.252 O(6)0.041 8(8)0.009 7(8)0.037 8(7)0.067 5(7)8 7 6 5 4 3 26Fig. 5 300 MHz 'H NMR spectrum of complex 10 in [ZH,]toluene.Solvent peaks are indicated by asteriskssolid-state structure shown in Fig. 1. These lines did notbroaden appreciably when the temperature of the sample wasraised to 350 K, indicating that the bridging bonds in 10 aremuch less labile than those in the oxomethoxide 8 for which wehave observed coalescence in the 'H NMR spectrum at around325 K.Although there was no evidence for site exchange withincreasing temperature, a spin-polarisation transfer experimentwith inversion of the central methoxide resonance (Fig.6 )demonstrated that there is slow exchange between all three sitesin solution. One other interesting feature of this experiment wasthe observation of a positive nuclear Overhauser effect (NOE)for the aromatic doublet at 6 7.3. Using the crystal-structuredetermination to estimate the closest approach between theortho hydrogens of the imido group and the hydrogens of themethoxides in the bridging plane (assuming normal C-H bondlengths and allowing free rotation about W-N, N-C, W-0 andC-0 bonds to bring the relevant atoms as close together aspossible) an assignment of the central peak to the terminalmethoxide (closest approach ca.1.70 A) rather than thebridging methoxide (closest approach ca. 1.95 A) is possible.At 305 K the 'H NMR spectrum of 11 shows the slightlybroadened methyl and methine resonances of only one iso-propoxide environment in addition to associated methyl andaromatic peaks of the imido group and some minor impuritypeaks [Fig. 7(a)]. The bulkier isopropoxide 11 is therefore muchmore dynamic than the methoxide 10. The results of a variable-temperature 'H NMR study are shown in Fig. 7 and thes3194!*J. CHEM. SOC. DALTON TRANS. 1992NMR spectrum of this omp pound.^ In the arylimidoiso-propoxide 11, steric effects again facilitate the formation of Bbut, because of the weaker trans effect of the imido group,rotation can still occur before the second bond dissociation, andintramolecular site exchange in A (E = NC,H,Me; R = Pr') isobserved in the 'H NMR spectrum.The approximate AGSvalues for alkoxide site exchange in 8 and 11 are 68 and 54 kJmol-' respectively at coalescence.The 'H and 13C chemical shifts of the NCH, methylenegroup in [{W(NBu")(OMe),),] are respectively 1.03 and 7.33ppm upfield of those in [{W(NBu")Cl,},]. This presumablyR R R8 7 6 56Fig. 610 with inversion of the central methoxide peak300 MHz 'H polarisation-transfer NMR spectrum of complexT /K305RARBRCincreasing temperature of peaks due to a mononuclearcompound.If we represent the bond-breaking process involved in thedynamics of these binuclear alkoxides [{ W(E)(OR),},] by A-Cabove, we can begin to rationalise the subtle interplay of factorsaffecting the differences in solution behaviour of the variouscompounds.In the oxomethoxide 8 the first bridging bondbreaks fairly readily to give B (E = 0; R = Me) and themethoxide ligands do not restrict the rotation indicated whichresults in alkoxide site exchange. Because of the weaker transeffect of the arylimido ligand, the bridging bonds in 10 arestronger and the compound is much less dynamic in solutionthan 8. The introduction of bulkier alkoxides causes stericcompression, and in the oxoisopropoxide [ WO(OPr'),] thismakes further W-0 bond dissociation to give C more favour-able than rotation of the WO(OPr'), fragments in B.Hence, A7 6 5 4 3 26Fig. 7in [2H,]toluene. Solvent peaks are indicated by asterisksVariable-temperature 300 MHz 'H NMR spectra of complex 11suggest that an intramolecular redistribution of the typeproposed for the oxomethoxide 84 rather than a monomer/dimer equilibrium is responsible for this dynamic behaviour.Hence, the spectrum of the dimeric solid-state structure is frozenout at 210K (the presence of four doublets in the high-fieldregion confirming the diastereotopic nature of the CH, groupsin the trans-axial OPr' ligands) and as the temperature is raisedthe isopropoxide peaks gradually broaden and then coalesce.We could see no evidence for the appearance and growth withmonomeric, trigonal-bipyramidal structure of [W(NBu')-(0Pri),] based on its 'H NMR spectrum, which showed thepresence of two types of isopropoxide in the ratio of 3 : 1.This isconsistent with the general picture of solution dynamicsoutlined above.In our attempts to obtain the cyclohexoxide 12 we triedtreating [W(NC,H4Me-4)C1,] with cyclohexanol and tert-butylamine, although Nielson et a/.' had shown that a similarreaction involving W(NPh)Cl,, Pr'OH and Bu'NH, producedthe amine adduct [W(NPh)(OPr'),(Bu'NH,)]. It was evidentfrom microanalysis results and from 'H NMR and IR spectrathat our product was impure and contained some Bu'NH,. The'H NMR spectrum contains well separated methyl andaromatic resonances for two p-tolylimido groups in addition tobroad cyclohexyl resonances between 6 4.2 and 5.2 (methinehydrogens) and between 6 1.2 and 2.2 (ring methylenes).A sharpBut peak is present at 6 1.22 and a broad peak at 6 3.75 ispossibly due to NH,. This suggests that a mixture of approxi-mately equal amounts of 12 and the amine adduct [W(NC,H,-Me-4)(0C6H 1)4(B~tNH2)] has been produced.Crystal Structure of [ NBu",] [ W (NPh),( 0 M e)C1,] .-In anattempt to prepare a mixed oxidation-state polynuclear organo-imido compound, the phenylimidomethoxide 1 was treated withthe tetra-n-butylammonium salt of the binuclear tungsten(vJ. CHEM. SOC. DALTON TRANS. 1992W)Fig. 8 A view of the molecular structure of [W,(NPh),(OMe)Cl,]-Table 10 Selected bond lengths (A) and angles (") for complex 172.695( 1)2.42 l(4)2.3 76(3)1.705(7)2.423(3)2.361(2)1.722(7)1.429( 10)W(2)-W( l)-C1( 1)C1( l)-W(l)-CI(2)C1( 1)-W( 1)-C1(3)W(2)-W( 1)-C1(4)C1(2tW( 1)-C1(4)W(2)-W( 1 W ( 1 )C1(2)-W( 1 )-O( 1)Cl(4)-W(ltO(l)O(lkW( lkN(1)W( I)-W(2)-C1(2)W( I)-W(2 jCI(5)C1( 2)-W( 2)-C1( 5 )CI( l)-W(2)-C1(6)C1( 5)-W(2)-C1(6)CI( 1)-W(2)-0( 1)W( 1 )-W(2tN(2)W( l)-Cl( I)-W(2)W( 1)-O(1)-W(2)W(2)-O( 1)-C( 1)Cl(lkW(1)-N(1)C1(3)-W( 1)-N( 1)C1(5)-W(2)-0( 1)C1(2)-W(2kN(2)C1(6>-W( 2)-N( 2)W( 2)-N(2)-C(2 1 )59.2( 1)76.3( 1)92.7( 1)127.7( 1)163.9( 1)47.6( 1)103.5(2)83.7(2)160.9(2)99.8(2)97.5(2)56.2( 1)133.2(1)83.7( 1)94.1(1)85.4(1)72.7(2)159.3(2)10 1.6( 2)90.7(2)10 1.3( 2)61.7(1)84.1(2)135.2(7)173.7(5)2.627(3)2.386(2)2.024( 5 )2.632( 3)2.362( 3)2.002(5)1.3 55( 13)1.416( 12)56.2( 1)133.9(1)83.q 1)92.7(1)8 5 3 1)72.q 1)161.2(2)101.9(2)90.8 (2)102.5(2)5 9 4 1)76.2( 1)91.1(1)128.1( 1)165.2( 1)48.3(1)104.1 (2)83.1(2)160.4(2)102.0(2)97.1(3)67.6( 1)134.3(6)170.9(5)anion '' [W,(NPh),C17]-.An X-ray crystal structure analysisof the red prisms obtained from dichloromethane-hexaneshowed that ligand exchange had resulted in substitution of oneof the bridging chlorides in the Wv starting material by amethoxide. The anion of [NBu",][W,(NPh),(OMe)Cl,] 17 isshown in Fig. 8 and bond distances and angles are given inTable 10 with atomic coordinates in Table 11.Presumably theother product is [(W(NPh)(OMe),CI},] which remains insolution.This anion is one of a family of confacial-bioctahedraltungsten(v) complexes and has the same gross structuralfeatures as the chloro derivatives [W2(E)2(p-C1)3C14]- (E = 0,NEt or NPh).' Again, the trans influence of the organoimidoligand is evident, the trans W-Cl bridging bonds being3195Table 11 Atomic coordinates for complex 17X0.505 56(2)0.687 39(2)0.563 3(2)0.534 5(2)0.334 l(2)0.451 8(2)0.736 7(2)0.830 9(2)0.646 5(4)0.693 5(9)0.503 O(4)0.495 O(5)0.541 6(6)0.529 l(7)0.471 9(10)0.427 9(8)0.438 9(7)0.732 2(5)0.757 8(6)0.789 O(8)0.814 O( 10)0.806 l(12)0.770 4( 14)0.749 4( 10)0.284 l(5)0.350 5(7)0.327 9(6)0.401 3(7)0.508 7(6)0.320 9(8)0.262 9( 14)0.284 3(20)0.399 O(22)0.173 3(6)0.146 6(6)0.031 8(7)0.007 O( 1 1)0.292 O(6)0.400 4(6)0.398 9( 13)0.360 5(32)Y0.581 50(2)0.510 21(2)0.449 O( 1)0.478 3(2)0.534 l(2)0.651 5(2)0.374 8(2)0.505 9(2)0.604 3(3)0.672 4(7)0.658 8(4)0.713 7(4)0.790 l(5)0.844 l(5)0.821 7(7)0.743 8(7)0.689 O(6)0.569 9(4)0.620 2(6)0.699 7(6)0.749 2(9)0.713 O(11)0.638 7( 11)0.585 7(8)0.321 O(5)0.309 5(5)0.233 9(8)0.232 l(9)0.209 9( 1 1)0.399 7(7)0.422 O( 1 1)0.512 2(14)0.525 4(21)0.325 9(6)0.398 O(7)0.406 6(8)0.482 7( 10)0.245 8(8)0.226 1( 11)0.1 50 2( 10)0.177 7(15)z0.728 Ol(2)0.729 47(2)0.809 5( 1)0.638 7(2)0.694 2(2)0.827 l(2)0.701 O(2)0.827 9( 1)0.788 4(3)0.822 9(8)0.664 2(4)0.602 l(4)0.612 O(5)0.552 3(5)0.485 7(6)0.477 3(5)0.535 6(5)0.665 4(4)0.608 6(5)0.623 4(6)0.567 2(8)0.498 6(9)0.483 5(8)0.539 O(6)0.837 4(5)0.781 6(5)0.729 7(8)0.675 7(5)0.717 2(7)0.879 6(6)0.939 7( 1 1)0.966 5(18)0.993 l(19)0.799 8(5)0.745 8(7)0.719 O(7)0.668 2( 11)0.889 6(7)0.931 l(7)0.982 4(6)1.052 O(12)considerably longer than those cis to NPh.The methoxide is cisto both imido ligands, facilitating any IT interactions with metalorbitals not used for IT bonding to the imido groups. Thestructural effects of introducing a bridging methoxide can beappreciated by considering the bond lengths and angles in Table12. The W-OMe bond distances are slightly smaller than theshorter bridging bond lengths in the [{ W(E)(OR),),] dimers(E = 0 or NR) discussed earlier, and are typical of p-ORdistances observed in a range of lower oxidation-state molyb-denum and tungsten alkoxides.Since these distances areshorter than the W-C1 bridging bonds, the core of the moleculecontracts slightly resulting in smaller W-Cl-W bridging anglesand a shorter W-W distance in the methoxide 17.All of these anions are diamagnetic and the question arises asto whether a direct metal-metal bond is present. Although theW-W distance of 2.695 A compares with the distances observedin d ' 4 ' compounds containing M,(p-OR), (M = Mo or W)where single bonds have been assigned, l 8 a theoretical analysisof the various factors which might determine moleculargeometry in M2L9 complexes19 concluded that in only aminority of examples is direct metal-metal bonding important,and that a delocalised bonding scheme involving orbitals fromthe bridging ligands is more appropriate.In solution, both 'H and 13C NMR spectra of 17 contain twomethoxide resonances in CD,CN and CD,Cl, respectively. Thedifference in the chemical shifts of these peaks suggests that amixture of isomers is present with the methoxide in eitherterminal or bridging positions3196 J.CHEM. SOC. DALTON TRANS. 1992Table 12 Selected bond lengths (A) and angles (") in confacial bioctahedral tungsten(v) 0x0 and organoimido anionsAnion W-E w-w w-x W-Y w-z wxw WYW wzw XWY xwz YWZ~W202C~71 - * 1.67 2.849 2.434 2.420 2.606 71.7 72.1 66.3 106.8 76.0 77.0CW,(NEt),CI,I - * 1.69 2.839 2.432 2.416 2.585 71.0 71.6 66.8 106.7 78.1 77.3CW2(NPh),Cl,I - * 1.72 2.835 2.423 2.440 2.575 71.6 71.8 66.6 106.7 76.8 77.117 [W,(NPh),(OMe)Cl,]- 1.71 2.695 2.422 (Cl) 2.013 (OMe) 2.630 67.6 84.1 61.7 103.8 76.3 72.6* Ref.17.ExperimentalAll manipulations were carried out under dry, oxygen-freeconditions using standard Schlenk techniques, or in a dry-boxfitted with a recirculation system. Hydrocarbon, thf and E t 2 0solvents were dried over and distilled from sodium-benzo-phenone immediately prior to use. Methanol was distilled overmagnesium methoxide. Propan-2-01 and cyclohexanol weredistilled from the corresponding sodium alkoxides and storedover 4 A molecular sieves, and Bu'OH was used as its benzeneazeotrope.Infrared spectra were recorded as Nujol mullsbetween CsI plates on a Perkin Elmer 598 spectrometer andNMR spectra were recorded on Bruker WP 200 or WM 300spectrometers. Elemental analyses were performed by themicroanalytical service, the University of Newcastle upon Tyne.Prepurutions.--[W(NC6H,Me-4)(0Me),] 10. Methanol (1.0cm3, 25.3 mmol) and tert-butylamine (2.5 cm3, 23.8 mmol) wereadded to [W(NC6H,Me-4)Cl,] (2.28 g, 5.3 mmol) suspendedin benzene (25 cm3). The mixture was stirred for 24 h, filteredand the solvent removed in uucuo. The resulting gum wasextracted with hot hexane (25 cm3) and after removal of thesolvent, the residue was recrystallised from acetonitrile to givegolden prisms (0.92 g, 42%) (Found: C, 31.0; H, 4.4; N, 3.5.Cl1Hl9NO4W requires C, 32.3; H, 4.5; N, 4.0%).IR: 1598w,1564w, 1503m, 1362s, 12 18w, 1 172w, 1 155m, 1 105m, 1075s,1050s, 1030m, 1019m, 1006m, 829s, 728w, 702w, 587s, 558w,540s, 520s (br), 473m, 444m, 349w, 341m, 300w and 238w cm-';6,(300.14 MHz, C,D,CD,) 7.29, 7.27, 7.12, 7.10 (4 H,NC,H,Me), 5.01 [6 H, s,(OCH,),],4.91 (3 H, s, OCH,),4.80(3 H, s, OCH,) and 2.42 (3 H, s, NC,H,CH,); 6,(50.32 MHz,CD,CN), 167.47, 137.52, 128.61, 127.67 (NC6H,Me), 64.21,62.26,62.09 (OCH,) and 19.94 (NC6H,CH3).[W(NC6H,Me-4)(0Pri),] 11. Lithium isopropoxide (1.73 g,6.2 mmol) was added to a solution of [W(NC6H,Me-4)Cl,] inthf (40 cm3) at - 70 "C and the mixture was allowed to warm toroom temperature.Volatiles were removed after stirring for 15 hand, after extraction with ether and solvent removal, the residuewas recrystallised from acetonitrile (35 cm3) to give goldenprisms (1.35 g, 42%) (Found: C, 42.4; H, 6.8; N, 2.7.C19H35N04W requires C, 43.4; H, 6.9; N, 2.7%). IR: 1598w,1 5 8 4 ~ ~ 1560w, 1500m, 1325m, 1168m, 1125s, 1020w, 975s (br),844m, 822m, 728w, 622w, 600m, 567w and 472w cm-'; 6,(300.14H, br s, OCHMe,) and 2.37 (3 H, s, NC,&+CH,); 6,(50.32MHz, CD3CN) 146.00, 129.50, 128.49, 114.75 (NC,H,Me),76.01 (OCHMe,), 25.63 (NC,H,CH,) and 24.67 [OCH-(CH3) 2 1 -15.1 mmol) and tert-butylamine (1.59 cm3, 15.1 mmol) wereadded to [W(NC6H4Me-4)C14] (1.63 g, 3.8 mmol) in hexane (30cm3) and the mixture was stirred for 24 h.The solution wasfiltered and cooled to -25 "C to give a yellow crystallineproduct (0.6 g) which is probably a mixture of 12 and[W(NC6H,Me-4)(0C6H, 1)4(NH2B~f)] (Found: C, 54.1; H,MHz, C6D5CD3) 7.31,7.29,7.15, 7.12 (4 H, NC6H,Me), 5.48 (4[W(NC6H4Me-4)(0C6Hl 1)4] 12. Cyclohexanol (1.57 Cm3,7.5; N, 2.9. C66H113N304W2 requires C, 54.9; H, 7.9; N, 2.9%).IR: 3330w, 3270w, 1620w, 1563m, 1498m, 1316m, 1268m,1252m, 1220m, 1181w, 1149w, 1130m, 1067s (br), 1020s, 975s(br), 927m, 913w, 890m, 865w, 848s, 819s, 791m, 752w, 702w,667s (br), 625m, 555 (sh), 548m, 535m, 514m, 498w, 462m, 458m,433w, 409m, 380m, 312m, 300m and 275m cm-'; 6,(300.14(8 H, br m, OCH), 3.75 (2 H, br, NH,), 2.44 (3 H, s,1.29 (80 H, br m, CH,) and 1.22 [9 H, s, H2NC(CH3),]; 6,(75.47(NC,H,Me), 83.72 (br, OCH), 50.40 (H,NCMe,), 36.56 (br,CH,), 31.99 [C(CH,),], 26.8 (NC6H,CH3) and 25.06 (br,MHz, CDZCI2) 7.15,7.12,6.95,6.92 (8 H, NC,H,Me), 4.25-5.05NC,H,CH,), 2.21 (3 H, S, NC,H,CH,), 2.02, 1.99, 1.71, 1.46,MHz, CD2C12) 136.00, 130.30, 129.16, 127.58, 116.80CH2).OH 13.Lithium cyclohexoxide (0.97 g, 9.15 mmol) wasadded to a solution of [W(NC6H,Me-4)C1,] (0.98 g, 2.28mmol) in thf (40 cm3) at 0 "C. The resulting yellow solution wasstirred for 24 h, filtered and the solvent removed under reducedpressure to give a yellow solid (1.41 g, 68%). Crystals suitable forX-ray diffraction were obtained from toluene-hexane at-25 "C (Found: C, 52.9; H, 8.0; N, 1.4. C49H86CILi2N07Wrequires C, 52.9; H, 7.5; N, 1.5%).IR: 3480m, 1500m, 1319w,1307w, 1268m, 1 1 OW, 1 13 1 m, 1092m, 1070s, 1 0 3 6 ~ ~ 994s, 980s,931w, 894m, 852m, 846m, 821s, 792m, 741m, 716m, 688m, 667s,648m, 628s, 540m, 520s, 470m, 439m and 390w cm-'; 6,(300.14(NC6H,Me), 5.2-3.8 (br m, OCH), 3.52 (m, CHOH), 2.64 [d,3J(HH) 4.3 Hz, CHOH], 2.23 (s. NC6H,CH3), 1.87, 1.77, 1.60and 1.28 (multiplets, CH,).[W(NC6H,Me-4)(0Bu'),] 14. A solution of lithium tert-butoxide (1.46 g, 18.2 mmol) in ether (20 cm3) was added to[W(NC,H4Me-4)CI,] (1.96 g, 4.55 mmol) in ether (30 cm3) andthe mixture was stirred for 15 h. After filtration, removal of thesolvent from the filtrate gave a yellow solid (0.66 g). This wasshown to contain several products by 'H NMR, but recrystal-lisation from acetonitrile gave a single compound.IR: 1493w,1352s, 1231w (br), 1166s (br), 1020w, 967m, 938s, 903w, 813m(br), 660w, 635w, 549w (br) and 470w cm-'; 6,(200.13 MHz,[{ W(NC6H4Me-4)(0C6H1 1)5Li2C1(C6H1 10H)2}21'C6Hl 1-MHz, CD3CN) 7.31, 7.29, 7.14, 7.11, 6.97, 6.94, 6.61, 6.58CD3CN) 7.17, 7.15, 6.60, 6.58 (4 H, NC,H,Me), 2.42 (3 H, S,NC6H4CH3) and 1.48 [36 H, S, OC(CH,)3].[W(NBu")CI4]. A mixture of WOCl, (1.55 g, 4.55 mmol)and Bu"NC0 (0.52 cm3, 4.55 mmol) in octane (70 cm3) washeated under reflux for 15 h. The resulting brownish solutionwas cooled to -25 "C to deposit an orange solid which wasfiltered off, washed with hexane and dried in uacuo (1.57 g, 87%)(Found: C, 12.6; H, 2.3; N, 3.5. C4H9Cl,NW requires C, 12.1; H,2.3; N, 3.5"/,); 6,(300.14 MHz, C6D6) 6.02 [2 H, t, 3J(HH) 6.3Hz, NCH,], 1.45 (2 H, m, NCH,CH,), 1.25 [2 H, m,N(CH2),CH2] and 0.72 [3 H, t, ,J(HH) 7.3 Hz, N(CH,),CH,];6,(75.47 MHz, C6D6) 68.38 (NCH,), 33.19 (NCH2CH2), 21.38[N(CH2)2CH2] and 13.98 [N(CH,),CH,].[(W(NBu")(OMe),},]. Methanol (0.52 cm', 12.8 mmol) wasadded to a solution of [W(NBu")Cl,] (1.27 g, 3.2 mmol) in thJ.CHEM. SOC. DALTON TRANS. 1992 3197Table 13 Crystallographic dataCompoundFormulaMCrystal systemSpace groupalAbiAC I Aa/"PI"ri"UjA3Nmm 'F ( o wCrystai sizeimmTransmission factorsZD,/crn-'2%l,Xl"Reflections measuredUnique reflectionsObserved reflectionsNo. of refined parametersRR' = (XWA'EWF,,~)?Goodness of fitMean, max. shift1e.s.d.Max., min.electron densityie k3Rint10826.3Monoclinic9.1611(8)10.101 8(6)15.2OO7( 10)9092.483(6)901405.421.9528.407920.12 x 0.25 x 0.350.05O-O.1585025242464203 70.0321550.04760.05771.59O.OO9,0.060C22H38N208W2p2 1 I C1.86, -2.19111050.7Triclinic10.197(2)10.333(2)12.339(3)87.08( 1)83.05(2)61.36(1)1132.611.5405.235240.46 x 0.54 x 0.620.1484.225506500398 136500.0322270.02730.02971.990.02 1,0.2 16C38H70N208W2Pi1.24, -0.5813C92H160C12Li4N2013W21968.7TriclinicPi11.908(5)12.582(5)17.940(8)79.12(2)79.54(3)7 1 .OO( 3)2474.811.3212.4810240.30 x 0.60 x 0.800.1774.242457076642356260.0425270.03930.03752.03O.OO3,0.0091.24, - 1.53171036.1Monoclinic13.448(6)16.057(7)18.394( 7)90101.82(5)903887.741.7706.4820080.40 x 0.40 x 0.600.03 14.0685010 379681450600.0203710.04270.035 11.430.036,0.420C29H49C16N30W2m,ln1.15, -0.91(40 cm3).Ammonia was immediately bubbled through thesolution for 5 min, and the mixture was then stirred for 16 h. Thesuspension was filtered and solvent removed in uucuo to give ayellow glassy solid (0.27 g, 60%) (Found: C, 24.6; H, 5.6; N, 3.7.C8H21N0,W requires C, 25.6; H, 5.6; N, 3.7%). IR: 1 3 0 0 ~ ~1260m, 1160m, 1105m, 1075s, 1020m (br), 952m, 918w, 895w,802m, 728s, 568m (br) and 510m cm-'; S,(300.14 MHz,C,D,CD3)4.99 [2 H,t, 3J(HH)4.6,NCH2],4.86(6 H, OCH,),4.83 (3 H,OCH,),4.66(3 H,0CH,),1.67(2H,m,NCH,CH2),1.60 [2 H, m, N(CH,),CH,] and 1.03 [3 H, t, 3J(HH) 7.2 Hz,N(CH2),CH3]; 6,(50.32 MHz, C6D,CD3) 65.35 (OCH,), 63.29(OCH,), 62.70 [(OCH,),], 61.05 [NCH,, 3J(CW) 15 Hz], 36.70(NCH,CH2),21.50[N(CH,),CH,]and 14.77 [N(CH,),CH,].[NBun,][W,(NPh),(OMe)C16] 17.The compound [W-(NPh)(OMe),] (0.45 g, 1.13 mmol) was added to a solutionof [NBu",][W,(NPh),CI,] (1.17 g, 1.12 mmol) in CH,CI, (15cm3). After 12 h a hexane layer was added and orange-redprisms were produced over the course of several days (0.79 g,68%) (Found: C, 33.6; H, 4.8; N, 4.0. C29H,&16N,0W2requires C, 35.1; H, 4.7; N, 4.0%). IR: 1580w, 1565w, 1174w,1159w, 1075m, 1061m, 1050m, 1031s, 995m, 895w, 881w, 775m,766s, 741m, 729m, 691m, 627w, 558w, 546m, 472w, 390m, 347m,329s, 301m, 280w and 249w cm-'; S,(300.14 MHz, CD,CN)7.8-6.7 (10 H, series of complex multiplets, NC6HS), 5.05 (s)and 4.89 (s) (3 H, OCH,), 3.09 (8 H, m, NCH,), 1.61 (8 H, m,NCH2CH,), 1.35 [8 H, m, N(CH,),CH,] and 0.99 [12 H, t,(CH,),CH,]; S,(50.32 MHz, CD,CN) 154.70, 128.08, 128.00,127.84, 126.89, 125.92 (NC6H,), 68.59, 65.17 (OCH,), 59.3 1(NCH2), 24.34 (NCH,CH,), 19.97 [N(CH,),CH,] and 13.94CN(CH2) 3 CH3I.X - Ray CvL'stalZography.-Data were measured at room tem-perature on a Stoe-Siemens diffractometer withmonochromated Mo-Ka radiation (h = 0.710 73 ), fromcrystals sealed in Lindemann capillaries.Crystallographic dataare summarised in Table 13. Cell parameters were refined ineach case from 28 values of 32 reflections (20-25") measuredwith w 9 scans; on-line profile fitting was used for 17.*'Corrections were made for intensity decay and for absorption(semiempirically). Atoms were located from Patterson andr p h i t e -difference syntheses and refined anisotropically by blocked-cascade least-squares methods ,' on F for reflections withF > 40(F); weighting was of the form w = l/02(F), withcontributions from both counting statistics and an analysis ofvariance.22 Hydrogen atoms were included in calculatedpositions for 11 (except methyl groups), 13 (except OH groups)and 17, with isotropic thermal parameters. The cation bondlengths and angles for 17 were restrained, as the atoms appearedto be somewhat disordered.The unco-ordinated cyclohexanolmolecule in 13 lies on a centre of symmetry, so the OH group isdisordered over two sites on opposite sides of the ring, eachwithin hydrogen-bonding distance of the OH group of acyclohexanol molecule co-ordinated to lithium.An isotropicextinction parameter x was refined to 2.4(6) x l t 7 for 13, suchthat F,' = FJ(1 + xFC2/sin 28)*; extinction effects wereinsignificant for the other structures. Atomic scattering factorswere taken from ref. 23.Additional material available from the Cambridge Crystallo-graphic Data Centre comprises H-atom coordinates, thermalparameters and remaining bond lengths and angles.AcknowledgementsWe thank the SERC for financial support and for an EarmarkedStudentship (to C. R.). We are also grateful to Dr. M. N. S . Hillfor his assistance with NMR experiments.References1 R. R. Schrock, J. S. Murdzek, G. Bazan, J. Robbins, M. DiMare and2 J. D. Burrington and R. K. Grasselli, J. Catal., 1979,59,79.3 W. A. Nugent and J. M. Mayer, Metal-LigandMultiple Bonds, Wiley,4 W. Clegg, R. J. Errington, P. Kraxner and C. Redshaw, J. Chem. SOC.,5 A. J. Nielson, J. M. Waters and D. C. Bradley, Polyhedron, 1985,4,285.6 P. A. Bates, A. J. Nielson and J. M. Waters, Polyhedron, 1987,6, 163.7 S. F. Pedersen and R. R. Schrock, J. Am. Chem. SOC., 1982,104,7483.8 D. C. Bradley, A. J. Howes, M. B. Hursthouse and J. D. Runnacles,M. ORegan, J. Am. Chem. SOC., 1990,112,3875.New York, 1988.Dalton Trans., 1992, 1431.Polyhedron, 199 1, 10,4773 198 J. CHEM. SOC. DALTON TRANS. 19929 W. Clegg, R. J. Errington and C. Redshaw, Acta Crystallogr., Sect. C,1987,43,2223.10 D. C. Bradley, M. H. Chisholm, M. W. Extine and M. E. Stager,Inorg. Chem., 1977, 16, 1794.1 1 (a) D. C. Bradley, R. J. Errington, M. B. Hursthouse, R. L. Short,B. R. Ashcroft, G. R. Clark, A. J. Nielson and C. E. F. Rickard, J.Chem. SOC., Dalton Trans., 1987,2067; (b) W. Clegg, R. J. Erringtonand C. Redshaw, Acfa Crystallogr., Sect. C, 1989,45, 164.12 F. A. Cottonand E. S. Shamshoum, J. Am. Chem. SOC., 1984,106,3222.13 W. Clegg, R. J. Errington, D. C. R. Hockless and C. Redshaw,14 P. G. Edwards, G. Wilkinson, M. B. Hursthouse and K. M. A. Malik,15 K. G. Caulton and L. G. Hubert-Pfalzgraf, Chem. Rev., 1990,90,969.16 N. Y. Turova, V. G. Kessler and S. I. Kucheiko, Polyhedron, 199 1,10,unpublished work.J. Chem. SOC., Dalton Trans., 1980,2467.2617.17 D. C. Bradley, R. J. Errington, M. B. Hursthouse and R. L. Short, J.Chem. SOC., Dalton Trans., 1990, 1043.18 M. H. Chisholm, Polyhedron, 1983,2,681.19 R. H. Summerville and R. Hoffmann, J. Am. Chem. Soc., 1979, 101,20 W. Clegg, Acta Crystallogr., Sect. A, 1981,37,22.21 G. M. Sheldrick, SHELXTL, an integrated system for solving,refining and displaying crystal structures from diffraction data,Revision 5, University of Gottingen, 1985.22 Wang Hong and B. E. Robertson, in Structures and Statistics inCrystallography, ed. A. J. C. Wilson, Adenine Press, New York, 1985,23 International Tables for X-Ray Crystallography, Kynoch Press,382 1.pp. 125-136.Birmingham, 1974, vol. 4, pp. 99, 149.Received 26th June 1992; Paper 2/03367