DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, 3941–3946 3941 Reactions of transition-metal nitrido compounds with B(C6F5)3 : crystal structure of [Re{NB(C6F5)3}(PMe2Ph)(S2CNMe2)2] Linda H. Doerrer, Andrew J. Graham and Malcolm L. H. Green* Inorganic Chemistry Laboratory, South Parks Road, Oxford, UK OX1 3QR. E-mail : malcolm.green@chem.ox.ac.uk Received 13th July 1998, Accepted 2nd October 1998 The transition-metal nitrido complexes [Re(N)(PR3)(S2CNR92)2] (PR3 = PMe2Ph, R9 = Me; PR3 = PMePh2, R9 = Et 1), [Re(N)(Cl)(PMePh2)2(S2CNMe2)] 2, [Mo(N)(S2CNR2)3] (R = Me or Et) and [NBun 4][Os(N)(1,2-S2C6H4)2] reacted with the strong Lewis acid B(C6F5)3 to yield the adducts [Re{NB(C6F5)3}(PR3)(S2CNR92)2] (PR3 = PMe2Ph, R9 = Me 3*; PR3 = PMePh2, R9 = Et 4), [Re{NB(C6F5)3}(Cl)(PMePh2)2(S2CNMe2)] 5, [Mo{NB(C6F5)3}(S2CNR2)3] (R = Me 6 or 7) and [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] 8 (* indicates that the compound has been structurally characterised).Reactions of 3, 6 and 8 with competing strong Lewis bases have revealed diVerences in the stability of the M]] ] N–B interaction depending on the steric crowding around the metal centre.Reaction of 8 with MeO3SCF3 causes the formation of [Os{NB(C6F5)3}{1,2-(S)(SMe)C6H4}(1,2-S2C6H4)] 9. Recently we have been exploring the varied chemistry of the strong Lewis acid B(C6F5)3 which is crystalline and easily synthesized. As well as mediating unusual and unexpected reactions, 1,2 it has been shown to form relatively stable adducts with transition metal oxo complexes.3,4 Transition metal nitrido complexes are another class of nucleophiles that might be expected to react with strong Lewis acids; indeed reactions between rhenium nitrido compounds and boron trihalides have been reported.5,6 However, adducts with triarylboranes have only previously been demonstrated by indirect reaction 7 and electrophilic attack at nitrido moieties bound to other metals has been confined to carbocationic Lewis acids.8,9 We here describe studies into the reactivity of B(C6F5)3 with transition metal nitrido complexes.† Results and discussion The new rhenium(V) nitrido complexes [Re(N)(PMePh2)- (S2CNEt2)2] 1 and [Re(N)(Cl)(PMePh2)2(S2CNMe2)] 2 were prepared by reaction of [Re(N)Cl2(PMePh2)3] 11 with 2 equivalents of NaS2CNEt2?3H2O and 1 equivalent of NaS2CNMe2? H2O respectively in refluxing methanol.The preparations used were analogous to those used by Ritter and Abram12 to prepare [Re(N)(PMe2Ph)(S2CNEt2)2] and [Re(N)(Cl)(PMe2Ph)2(S2- CNMe2)]. Characterisation was undertaken by means of microanalysis and IR and NMR spectroscopies; these data are summarised in Table 1.Assignments were straightforward; the Re]] ] N stretches in the IR spectra were assigned by analogy with those of previously reported complexes. Treatment of each of the transition-metal nitrido complexes [Re(N)(PR3)(S2CNR92)2] (PR3 = PMe2Ph, R9 = Me; PR3 = PMe- Ph2, R9 = Et 1), [Re(N)(Cl)(PMePh2)2(S2CNMe2)] 2, [Mo(N)- (S2CNR2)3] (R = Me or Et) and [NBun 4][Os(N)(1,2-S2C6H4)2] with an excess of B(C6F5)3 in dichloromethane at ambient temperature yields the nitridometal–Lewis acid adducts as purple [Re{NB(C6F5)3}(PR3)(S2CNR92)2] (PR3 = PMe2Ph, R9 = Me 3; PR3 = PMePh2, R9 = Et 4), orange [Re{NB(C6F5)3}(Cl)- (PMePh2)2(S2CNMe2)] 5, cream and red-brown [Mo{NB- (C6F5)3}(S2CNR2)3] (R = Me 6 or Et 7) and olive-green [NBun 4]- † During the revision of this manuscript a report of work demonstrating diVerent reactivity between arylborane species and osmium nitrido compounds was published.10 [Os{NB(C6F5)3}(1,2-S2C6H4)2] 8 respectively (Scheme 1).These compounds are all highly soluble in dichloromethane but virtually insoluble in hydrocarbon solvents and removal of the excess of borane by washing thoroughly with hexanes was generally suYcent to obtain analytically pure product. The compounds 3–8 are reasonably air- and moisture-tolerant in the solid state and can be stored indefinitely under an inert atmosphere without decomposition.Yields were generally quite high (ca. 60–90%). Compounds 3–8 have been characterised by standard techniques, namely 1H, 11B, 13C, 19F and 31P NMR and IR spectroscopies, microanalysis and, in the case of 3, 4 and 6, FAB (Fast Atom Bombardment) mass spectrometry (Table 1). A single crystal determination of compound 3 has been carried out; crystals of 4 were also obtained but they proved to be of insuf- ficient quality to obtain a properly refined structure although the connectivity between atoms could be verified.As expected, an upfield shift of the 11B-{1H} NMR spectroscopic resonance of B(C6F5)3 (d 51) to d 23 to 26 is observed on adduct formation. This is consistent with the presence of a four-co-ordinate boron species and hence with the expected formation of an M]] ] N–B dative bond. Infrared spectroscopy was in the main rather uninformative as regards the strength of the M]] ] N–B interaction since pentafluorophenyl groups display strong absorptions in the range 900–1100 cm21, preventing unambiguous assignment of the M]] ] N stretch.One might expect that the nitridometal complex–Lewis acid interaction would weaken the M]] ] N bond, as is found to be the case with Lewis acid adducts of oxometal complexes.13 However, in practice, an increase in the M]] ] N stretching frequency is usually observed, e.g.the Re]] ] N stretch in [AsPh4][Re(N)Br4] is observed to move from 1099 to 1170 cm21 on addition of BBr3.14 This is often attributed to resonance between the B–N and M]] ] N stretches; however one of the referees has suggested an alternative explanation based on Molecular Orbital theory. The “nitrogen lone pair” MO in the parent nitrido compound has significant M–N s-antibonding character. Upon co-ordination of the Lewis acid this orbital gains some B–N bonding character hence increasing the M–N stretching frequency.In general, IR stretching frequencies are more sensitive to such changes in antibonding/bonding character than are bond distances. Tentative assignments of the M]] ] N stretch in compounds 3 to 8, based on the premise that they increase upon borane co-3942 J. Chem. Soc., Dalton Trans., 1998, 3941–3946 Scheme 1 Reagents and conditions: (i) excess of B(C6F5)3 in CH2Cl2; (ii) excess of MeO3CF3 in CH2Cl2. N Re S PR3 S S S C CNR'2 N Re S PR3 S S S C CNR'2 N Re S Ph2MeP S Ph2MeP N Mo S S S S S S CNR2 R2NC CNR2 N Mo S S S S S S CNR2 R2NC CNR2 N Os S S S S N Os S S S S N Os S S S S Me CNMe2 Cl N Re S Ph2MeP S Ph2MeP CNMe2 Cl B(C6F5)3 B(C6F5)3 B(C6F5)3 B(C6F5)3 [Bun 4N] [Bun 4N] i i i i PR3 = PMe2Ph, R' = Me; PR3 = PMePh2, R' = Et 1 PR3 = PMe2Ph, R' = Me 3; PR3 = PMePh2, R' = Et 4 R'2N R'2 N 2 5 R = Me 6, Et 7 8 B(C6F5)3 9 ii ordination, are given in Table 1.The C6F5 regions of the 13C-{1H} and 19F NMR spectra of compounds 3 to 9 have been assigned by analogy with those of B(C6F5)3 15 and also with those of other published adducts.16 For compounds 3 to 5, the phenyl resonances in the 13C-{1H} NMR spectra were assigned by examination of the magnitude of nJPC; for compound 4, a 13C–1H correlation experiment was performed to assign the downfield region of the 1H NMR spectrum.Other assignments are straightforward and are not discussed further. The molecular structure of compound 3 is shown in Fig. 1; principal bond distances and angles are given in Table 2 . The rhenium centre has an octahedral co-ordination environment with the nitride–borane unit occupying an axial site and the phosphine cis to it. The starting nitrido complex has not been structurally characterised, however a single crystal X-ray study has been performed on the closely related compound [Re(N)- (PMe2Ph)(S2CNEt2)2].12 Comparison of the two structures reveals the expected features, namely an extremely small increase in Re–N bond distance on Lewis acid co-ordination [from 1.666(6) to 1.700(4) Å], an almost linear Re]] ] N–B moiety [170.9(3)8] and a significant diminishing of the trans influence of the nitrido ligand (reduction in the diVerence between the Re–Strans and Re–Scis distances from ca. 0.35 to ca. 0.25 Å). Table 3 shows the structurally characterised borane adducts of octahedral rhenium nitrido complexes found in the literature and demonstrates the generality of all three of these features.Crystallographically characterised starting metal nitrido compounds are included for comparison purposes.J. Chem. Soc., Dalton Trans., 1998, 3941–3946 3943 Table 1 Analytical and spectroscopic data for compounds 1–9 Compounda 1 [Re(N)(PMePh2)(S2CNEt2)2] Orange-brown C, 40.2 (39.6); H, 4.7 (4.8); N, 5.8 (6.0); P, 4.6 (4.4) IR: 1358s, 1302s, 1273s, 1212s, 1146s, 1096s, 1076s, 1054s [n(Re–N)], 914s, 888s NMR Data b 1H: 1.04 (dd, 6 H, 3JHH = 7.1, 7.2, NCH2CH3), 1.36 (dd, 6 H, 3JHH = 7.2, 7.2, NCH2CH3), 2.31 (d, 3 H, 2JPH = 8.8, PCH3), 3.36, 3.58, 3.71 and 3.87 (m, 2 H each, NCH2CH3), 7.3– 7.8 (m, 10 H, PC6H5) 13C-{1H}: 12.45 and 12.84 (s, NCH2CH3), 18.02 (d, 1JCP = 36.7, PCH3), 45.14 and 46.03 (s, NCH2CH3), 128.38 (d, 2JCP = 11.2, PC6H5, Co), 131.56 (s, PC6H5, Cp), 134.04 (d, 1JCP = 48.5, PC6H5, Cipso), 135.17 (d, 3JCP = 8.9, PC6H5, Cm), 202.66 and 223.87 (s, S2CNEt2) 31P-{1H}: 25.05 (s) 2 [Re(N)(Cl)(PMePh2)2(S2CNMe2)] Yellow-brown C, 46.5 (46.1); H, 4.1 (4.3); N, 4.0 (3.7) IR: 1261s, 1094s, 1060s [n(Re–N)], 1020s, 800s 1H: 2.13 (d, 6 H, 2JPH = 8.9, PCH3), 3.24 (s, 6 H, NCH3), 7.1–7.7 (m, 20 H, PC6H5) 31P-{1H}: 210.77 (s) 3 [Re{NB(C6F5)3}(PMe2Ph)(S2CNMe2)2] Lavender C, 35.4 (35.2); H, 2.1 (2.1); B, 0.7 (1.0); N, 3.2 (3.85) Mass: 579, [M 2 B(C6F5)3]1 IR: 2727s, 1304s, 1281s, 1156s, 1092s [n(Re–N)] d 1H: 1.81 and 1.97 (d, 3 H each, 2JPH = 9.6, PCH3), 2.67, 2.98, 3.28 and 3.35 (s, 3 H each, NCH3), 7.3–7.4 (m, 5 H, PC6H5) 11B-{1H}: 23.9 (s) 13C-{1H}: 15.82 (d, 1JCP = 33.6, PCH3), 16.04 (d, 1JCP = 39.3, PCH3), 39.07,c 39.17 and 39.71 (s, NCH3), 117.5 (br s, BC6F5, Cipso), 127.32 (d, 2JCP = 9.7, PC6H5, Co), 130.03 (s, PC6H5, Cp), 131.37 (d, 3JCP = 8.3, PC6H5, Cm), 134.28 (d, 1JCP = 53.1, PC6H5, Cipso), 136.89 (d, 1JCF = 257, BC6F5, Cm), 139.42 (d, 1JCF = 247, BC6F5, Cp), 147.77 (d, 1JCF = 241, BC6F5, Co), 201.75 and 228.20 (s, S2CNMe2) 31P-{1H}: 226.57 (s) 4 [Re{NB(C6F5)3}(PMePh2)(S2CNEt2)2] e Purple C, 41.3 (41.2); H, 3.05 (3.0); B, 0.85 (0.9); N, 3.4 (3.4); P, 2.6 (2.5) Mass: 1209, M1; 1042, [M 2 C6F5]1; 842, [M 2 PMePh2 2 C6F5]1; 697, [M 2 B(C6F5)3]1; 581, [M 2 B(C6F5)3 2 4Et]1; 549, [M 2 B(C6F5)3 2 S2- CNEt2]1; 497, [M 2 B(C6F5)3 2 PMePh2]1; 399, [M 2 B(C6F5)3 2 2S2CNEt2]1 IR: 1303m, 1276m, 1147m, 1089m [n(Re–N)],d 978s 1H: 0.86 [d, 3 H, 3JHH = 6.5 (CH3)2CHOH], 0.94, 1.10, 1.25 and 1.37 (dd, 3 H each, 3JHH = 7.0, 7.0, NCH2CH3), 2.20 (d, 3 H, 2JPH = 9.0, PCH3), 3.22, 3.29, 3.42, 3.52, 3.59, 3.72, 3.78 and 3.81 (m, 1 H each, NCH2CH3), 3.73 [m, 0.5 H, (CH3)2CHOH], 7.22 (dd, 2 H, 3JPH = 8.5, 3JHH = 8.5, PC6H5, Ho), 7.29 (t, 1 H, 3JHH = 8.5, PC6H5, Hp), 7.36 (dd, 2 H, 3JHH = 8.5, 8.5, PC6H5, Hm), 7.42 (m, 2 H, PC6H5, Ho), 7.43 (m, 1 H, PC6H5, Hp), 7.65 (dd, 2 H, 3JHH = 8.5, 8.5, PC6H5, Hm) 11B-{1H}: 23.4 (s) 13C-{1H}: 1.10 [s, (CH3)2CHOH], 12.01, 12.43, 12.58 and 12.67 (s, NCH2CH3), 17.22, (d, 1JCP = 36.8, PCH3), 22.68 [s, (CH3)2CHOH], 44.72, 44.96, 45.00 and 45.98 (s, NCH2CH3), 119.0 (br s, BC6F5, Cipso), 128.02 and 128.38 (d, 2JCP = 11.0, PC6H5, Co), 130.23 and 130.93 (s, PC6H5, Cp), 132.2 and 133.40 (d, 3JCP = 9.2, PC6H5, Cm), 133.7 and 136.88 (d, 1JCP = 49.2, PC6H5, Cipso), 136.81 (d, 1JCF = 271, BC6F5, Cm), 139.52 (d, 1JCF = 245, BC6F5, Cp), 148.02 (d, 1JCF = 241, BC6F5, Co), 199.95 and 229.78 (s, S2CNEt2) 19F: 2168.79 (dd, 6 F, 3JFF = 22.6, 20.7, BC6F5, Fm), 2163.90 (t, 3 F, 3JFF = 20.7, BC6F5, Fp), 2133.80 (d, 6 F, 3JFF = 22.6, BC6F5, Fo) 31P-{1H}: 212.86 (s) 5 [Re{NB(C6F5)3}(Cl)(PMePh2)2(S2CNMe2)] Orange C, 44.5 (44.5); H, 3.3 (2.5); N, 1.9 (2.2) IR: 1099w [n(Re–N)],d 970w, 895m, 722m 1H: 1.79 (d, 6 H, 2JPH = 9.5, PCH3), 3.16 (s, 6 H, NCH3), 7.0–7.8 (m, 20 H, PC6H5) 11B-{1H}: 22.7 (s) 13C-{1H}: 15.31 (d, 1JCP = 36.6, PCH3), 19.17 (d, 1JCP = 38.3, PCH3), 38.58 and 39.65 (s, NCH3), 120.1 (br s, BC6F5, Cipso), 127.84, 128.39, 129.01, 130.17, 130.92, 131.28, 132.18, 132.62 and 133.32 (PC6H5), 134.37 (d, 1JCP = 59.6, PC6H5, Cipso), 135.82 (d, 1JCP = 58.9, PC6H5, Cipso), 136.68 (d, 1JCF = 252, BC6F5, Cm), 139.27 (d, 1JCF = 263, BC6F5, Cp), 148.03 (d, 1JCF = 253, BC6F5, Co), 191.15 (s, S2CNMe2) 31P-{1H}: 216.73 (s) 6 [Mo{NB(C6F5)3}(S2CNMe2)3] Cream C, 33.6 (33.0); H, 1.9 (1.85); B, 1.0 (1.1); N, 4.9 (5.7) Mass: 984, M1; 773, [M 2 C6F5 2 MNe2]1; 697, [M 2 C6F5 2 S2CNMe2]1; 472, [M 2 B(C6F5)3]1; 352, [M 2 B(C6F3)3 2 S2CNMe2]1 IR: 1645w, 1559m, 1514m, 1305m, 1156m, 1082m (br) [n(Re–N)],d 979m (br) 1H: 3.19 (s, 3 H, NCH3), 3.25 (s, 6 H, NCH3), 3.34 (s, 6 H, NCH3), 3.38 (s, 3 H, NCH3) 11B-{1H}: 26.5 (s) 13C-{1H}: 35.63, 37.36, 40.68 and 41.10 (s, NCH3),f 119.0 (br s, BC6F5, Cipso), 136.86 (d, 1JCF = 241, BC6F5, Cm), 139.28 (d, 1JCF = 247, BC6F5, Cp), 147.81 (d, 1JCF = 239, BC6F5, Co), 200.78 and 203.62 (s, S2CNMe2) g 19F: 2168.98 (m, 6 F, BC6F5, Fm), 2163.87 (t, 3 F, 3JFF = 26.3, BC6F5, Fp), 2134.17 (d, 6 F, 3JFF = 18.8, BC6F5, Fo) 7 [Mo{NB(C6F5)3}(S2CNEt2)3] Red-brown C, 38.7 (37.2); H, 3.1 (2.8); B, 1.0 (1.0); N, 4.6 (5.25) IR: 1302s, 1262s, 1209m, 1152m, 1089m [n(Re–N)],d 976s 1H: 1.11–1.46 (m, 18 H, NCH2CH3), 3.61–3.81 (m, 12 H, NCH2CH3) 11B-{1H}: 26.6 (s) 13C-{1H}: 11.77, 12.23, 12.36 and 12.48 (2, NCH2CH3),f 43.31, 44.46, 45.58 and 46.64 (s, NCH2CH3),f 119.8 (br s, BC6F5, Cipso), 136.87 (d, 1JCF = 255, BC6F5, Cm), 139.24 (d, 1JCF = 248, BC6F5, Cp), 147.81 (d, 1JCF = 240, BC6F5, Co), 199.39 and 202.38 (s, S2CNEt2) g 8 [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] Olive-green C, 44.9 (44.6); H, 3.25 (3.6); B, 1.2 (0.9); N, 2.0 (2.3) IR: 1644m, 1515s, 1283m, 1275m, 1097s, 979s, 794m 1H: 0.90 [t, 12 H, 3JHH = 7.1, N(CH2)3CH3], 1.26 [m, 8 H, N(CH2)2CH2CH3], 1.37 (m, 8 H, NCH2CH2CH2CH3), 2.63 [m, 8 H, NCH2(CH2)2CH3], 7.03 and 7.68 (m, AA9BB9 spin system, 8 H, S2C6H4) 11B-{1H}: 23.7 (s) 13C-{1H}: 13.32 [s, N(CH2)3CH3], 19.72 [s, N(CH2)2CH2CH3], 23.68 (s, NCH2CH2- CH2CH3), 58.98 [s, NCH2(CH2)2CH3], 114.0 (br s, BC6F5, Cipso), 124.69 and 127.90 (s, S2C6H4), 136.67 (d, 1JCF = 238, BC6F5, Cm), 139.56 (d, 1JCF = 228, BC6F5, Cp), 147.56 (d, 1JCF = 246, BC6F5, Co), 149.77 (s, S2C6H4, Cipso) 19F: 2168.80 (m, 6 F, BC6F5, Fm), 2162.99 (t, 3 F, 3JFF = 20.7, BC6F5, Fp), 2134.72 (d, 6 F, 3JFF = 24.0, BC6F5, Fo) 9 [Os{NB(C6F5)3}{1,2-(S)(SMe)C6H4}(1,2-S2C6H4)] Dark green oil h 1H: 3.06 (s, SCH3), 7.0–7.8 (br, C6H4) 11B-{1H}: 22.3 (s) 13C-{1H}: 33.5 (br s, SCH3), 118.7 (br s, BC6F5, Cipso), 122.17, 127.01, 128.36, 128.97, 130.47 and 132.27 [br s, S2C6H4 and (S)(SCH3)C6H4], 136.90, (d, 1JCF = 246, BC6F5, Cm), 140.30 (d, 1JCF = 267, BC6F5, Cp), 148.12 (d, 1JCF = 240, BC6F5, Co) a Analytical data given as found (calculated) in %.Mass spectral data (Fast Atom Bombardment) given as m/z (assignment), selected IR data (cm21) as Nujol mulls. b At probe temperature. Data given as: chemical shift (d) (multiplicity, relative intensity, J in Hz, assignment).All obtained in CD2Cl2. c Two coincident resonances. d Tentative assignment, see text. e Crystallised with 0.5 molecule of PriOH. f Resonances in 2:2:1:1 intensity ratio. g Resonances in 2 : 1 intensity ratio. h Oil too sensitive to obtain microanalytical data.3944 J. Chem. Soc., Dalton Trans., 1998, 3941–3946 The NMR spectra of compounds 3–5 reveal that there is a lowering of symmetry upon co-ordination of the Lewis acid. For instance, compound 1 displays 2 methyl and 4 methylene resonances in its 1H NMR spectrum whereas 4 and 8 signals respectively are observed for the B(C6F5)3 adduct 4.This may be attributed to restriction of free rotation about the Re–P bond upon addition of the bulky triarylborane. A further point of interest is provided by compound 5 where there is apparently only one dithiocarbamate methyl environment and one phosphine methyl environment in the 1H NMR spectrum but two distinct resonances for each in the 13C-{1H} NMR spectrum.This has been attributed to the diVerent timescales involved in 1H and 13C-{1H} NMR spectroscopy. The adducts 6 and 7 display 4 distinct dithiocarbamate resonances in their 1H and 13C-{1H} NMR spectra with intensity ratios 1:2:2:1; this is in agreement with published data for the compound [Mo(NCPh3)- (S2CNMe2)3][BF4].8 The NMR spectra of compound 8 are similar to those of the parent nitrido complex and are not discussed further.In order to test the strength of the M]] ] N–B interaction, the reactions of compounds 3, 6 and 8 with a series of competing Lewis bases were attempted. The bases used were NEt3, PMe3 Fig. 1 Molecular structure of [Re{NB(C6F5)3}(PMe2Ph)(S2CNMe2)2] 3 showing the atom numbering scheme. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level. Table 2 Selected bond distances (Å) and angles (8) for compound 3 B(1)–N(3) Re–N(3) Re–S(1) Re–S(2) Re–S(3) Re–S(4) Re–P(1) 1.548(7) 1.700(4) 2.3769(12) 2.4350(15) 2.6090(12) 2.4608(13) 2.4154(15) B(1)–N(3)–Re C(20)–B(1)–C(30) C(30)–B(1)–C(40) C(20)–B(1)–C(40) C(20)–B(1)–N(3) C(30)–B(1)–N(3) C(40)–B(1)–N(3) 170.9(3) 103.3(4) 114.5(4) 114.7(4) 109.0(4) 115.2(4) 100.4(4) and THF and in all cases an excess of base was added to a dichloromethane solution of the adduct and after 1 h stirring the reaction residues were analysed by NMR spectroscopy.Tetrahydrofuran was shown to cause no alteration to either the 1H or 11B-{1H} NMR spectra of all 3 compounds, however NEt3 and PMe3 had diVering eVects depending on the metal centre.For the rhenium complex 3 no eVect was observed on Lewis base addition, whereas for the osmium compound 8, addition of L (L = PMe3 or NEt3) caused quantitative formation of the parent nitrido compound and L?B(C6F5)3 within 1 h. The molybdenum compound 6 displayed intermediate stability with approximately 50% displacement of the parent nitrido complex by the competing Lewis base over 1 h.The diVerence in stability of these 3 metal nitrido complex–Lewis acid adducts is probably due to steric factors since the Re]] ] N–B moiety in 3 is protected by the bulky cis tertiary phosphine and the Os]] ] N–B linkage in 8 is exposed by the ‘tied back’ dithiolate ligands. Compound 6 displays intermediate steric hindrance. Following the work of Sellmann et al.9 who demonstrated the presence of two nucleophilic sites on the compound [NBun 4]- [Os(N)(1,2-S2C6H4)2], the B(C6F5)3 adduct of this metal nitrido complex was treated with 2 competing Lewis acids, namely [Ph3C][BF4] and MeO3SCF3.As expected, the bulky trityl cation displaced the borane at the less hindered nitrido moiety to yield the known compound [Os(NCPh3)(1,2-S2C6H4)2].9 However, reaction of [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] 8 with an excess of methyl triflate in dichloromethane yields, after extraction into toluene, the olive-green oil [Os{NB(C6F5)3}{1,2- (S)(SMe)C6H4}(1,2-S2C6H4)] 9 in which Lewis acids are coordinated to both nucleophilic sites.This adduct has been characterised by NMR spectroscopy only since the oil was too sensitive to obtain meaningful microanalytical data. This indicates that the methyl group is relatively mobile and can move between the 4 sulfur donors. In conclusion, we have demonstrated that the nitrido group in transition metal nitrido complexes is suYciently nucleophilic to form a dative bond with the Lewis acid B(C6F5)3.These adducts are the first reported from direct reactions between a triarylborane and a transition metal nitrido complex. The M]] ] N–B interaction is reasonably strong as demonstrated by the relative stability of the adducts towards atmospheric oxygen and moisture, although stability towards competing strong Lewis bases seems to vary from metal to metal and is probably a function of steric crowding. Experimental All preparations and manipulations of air and/or moisture sensitive materials were carried out under an atmosphere of dinitrogen using standard Schlenk line techniques or in an inert-atmosphere glove-box containing dinitrogen.Dinitrogen was purified before use by passage through a drying column filled with activated molecular sieves (4 Å) and a deoxygenating column filled with either manganese(II) oxide suspended on vermiculite (Schlenk line) or BASF catalyst (glove-box).Solvents were predried over activated 4 Å molecular sieves and then distilled from sodium (toluene), sodium–potassium alloy Table 3 Comparison of cis and trans metal–ligand distances and Re–N–B bond angles for some octahedral rhenium(V) nitrido complexes and their Lewis acid adducts Compound 3 [Re{NB(C6F5)3}(PMePh2)(S2CNMe2)2] [Re(N)(PMe2Ph)(S2CNEt2)2] 12 [Re(NBCl3)(PMe2Ph)(S2CNEt2)2] 6 [Re(NBPh3)(PMe2Ph)(S2CNEt2)2] 7 [Re(N)Cl2(PMe2Ph)3] 17 [Re(NBCl3)Cl2(PMe2Ph)3] 18 Re–Ltrans/Å 2.6090 2.793(2) 2.565(2) 2.579(4) 2.633(2) 2.439(3) Re–Lcis/Å 2.3769(12)–2.4608(13) 2.396(1)–2.449(1) 2.376(2)–2.455(2) 2.362(4)–2.431(4) 2.442(2) b 2.394(3) b B–N–Re/8 170.9(3) a 170.5(3) 170.9(9) a 176.5(6) Re–N/Å 1.700(4) 1.666(6) 1.704(3) 1.653(12) 1.660(8) 1.728(7) a Not applicable. b Re–Clcis distance.J.Chem. Soc., Dalton Trans., 1998, 3941–3946 3945 [pentane and light petroleum (bp 40–60 8C)], potassium (THF) or calcium hydride (dichloromethane) under a slow continuous stream of dinitrogen.The Analar solvents methanol and PriOH were used as supplied without drying and degassed by bubbling dinitrogen through them for 15 min. Deuteriated dichloromethane for NMR spectroscopy was dried over calcium hydride and deoxygenated by three freeze–pump–thaw cycles. Deuteriochloroform was used as supplied. The NMR spectra were recorded on either a Varian Unity- Plus 500 (1H, 11B, 13C, 19F and 31P at 499.87, 160.38, 123.70, 470.28 and 202.35 MHz respectively) or a Bruker AM300 spectrometer (1H, 11B, 13C and 31P at 300.13, 96.25, 75.5 and 121.6 MHz respectively).They were referenced internally using the residual protio-solvent (1H) and solvent (13C) resonances and measured relative to tetramethylsilane (d 0), or referenced externally to BF3?Et2O (11B, d 0), CFCl3 (19F, d 0) or 85% H3PO4 (31P, d 0). Chemical shifts are quoted in d (ppm); a positive sign indicates a downfield shift relative to the standard. Fast atom bombardment mass spectra were obtained by the EPSRC Mass Spectrometry Service at the University College of Swansea under the supervision of Dr J.A. Ballantine; infrared spectra as Nujol mulls between NaCl plates on a Perkin-Elmer 1710 FTIR spectrometer in the range 400 to 4000 cm21. Elemental analyses were obtained by the microanalytical department of the Inorganic Chemistry Laboratory. The compounds [Re(N)Cl2(PMePh2)3],11 [Re(N)(PMe2Ph)- (S2CNMe2)2],12 [Mo(N)(S2CNR2)3] (R = Me or Et),19 [NBun 4][Os(N)(1,2-S2C6H4)2]9 and B(C6F5)3 1,20 were prepared by literature methods.Preparations [Re(N)(PMePh2)(S2CNEt2)2] 1. To a stirred solution of [Re(N)Cl2(PMePh2)3] (0.300 g, 0.34 mmol) in methanol (30 cm3), NaS2CNEt2?3H2O (0.233 g, 1.03 mmol) in methanol (15 cm3) was added. The reaction mixture, which immediately changed from yellow to orange, was heated to reflux for 1 h before being allowed to cool to room temperature. The solvent was removed in vacuo and the resulting, rather oily, orange solid washed with PriOH (20 cm3). Recrystallisation from PriOH and dichloromethane (15 cm3 of a 1 : 1 mixture) at 280 8C aVorded complex 1 analytically pure.Yield: 0.116 g (48%). [Re(N)(Cl)(PMePh2)2(S2CNMe2)] 2. The complex [Re(N)- Cl2(PMePh2)3] (0.436 g, 0.500 mmol) was dissolved in methanol (20 cm3) and a solution of NaS2CNMe2?H2O (72 mg, 0.500 mmol) in methanol (15 cm3) was added causing immediate darkening of the reaction mixture.The mixture was heated to reflux for 1 h after which time it was cooled to ambient temperature and concentrated to half volume. This led to precipitation of the product which was isolated analytically pure by filtration and washing with PriOH (2 × 10 cm3). Yield: 0.201 g (53%). [Re{NB(C6F5)3}(PMe2Ph)(S2CNMe2)2] 3. To a stirred solution of [Re(N)(PMe2Ph)(S2CNMe2)2] (0.289 g, 0.500 mmol) in dichloromethane (20 cm3) was added B(C6F5)3 (0.280 g, 0.547 mmol) in dichloromethane (15 cm3).Upon stirring overnight the solution darkened somewhat and the solvent was removed under vacuum to yield a grey oily solid. The product was aVorded analytically pure by trituration with pentane (2 × 15 cm3) and drying overnight in vacuo. Single crystals suitable for analysis by X-ray diVraction were grown by slow vapour diffusion of pentane into a dichloromethane (20 cm3) solution of complex 3 (ca. 20 mg). Yield: 0.300 g (55%). [Re{NB(C6F5)3}(PMePh2)(S2CNEt2)2] 4. To a stirred solution of [Re(N)(PMePh2)(S2CNEt2)2] 1 (90 mg, 0.129 mmol) in dichloromethane (15 cm3), B(C6F5)3 (72 mg, 0.140 mmol) in dichloromethane (5 cm3) was added.An immediate change from yellow to violet was observed. After 1 h of stirring, light petroleum (30 cm3) was added but no solid precipitated overnight. Hence the volatiles were removed under vacuum and the resulting oily solid triturated with light petroleum (20 cm3) to yield the product as a lavender powder. Crystallisation by slow evaporation of a solution of the product in PriOH and dichloromethane (10 cm3 of a 1 : 1 mixture) led to its isolation as purple single crystals which proved to be of insuYcient quality for analysis by X-ray diVraction.Microanalysis and NMR spectroscopy identified this product as pure complex 4?0.5 PriOH. Yield: 0.104 g (65%). [Re{NB(C6F5)3}(Cl)(PMePh2)2(S2CNMe2)] 5. To a stirred solution of [Re(N)(Cl)(PMePh2)2(S2CNMe2)] 2 (0.180 g, 0.238 mmol) in dichloromethane (15 cm3) a solution of B(C6F5)3 (0.144 g, 0.281 mmol) in dichloromethane (5 cm3) was added dropwise.An immediate change from yellow to orange-red was observed. Stirring was maintained for 3 h after which time the solvent was removed under vacuum and the resulting red oily solid triturated with pentane (20 cm3). This aVorded the product as a dark orange powder which was dried in vacuo overnight and shown to be pure by microanalysis. Yield: 0.199 g (66%). [Mo{NB(C6F5)3}(S2CNMe2)3] 6.To a stirred suspension of [Mo(N)(S2CNMe2)3] (0.200 g, 0.425 mmol) in dichloromethane (30 cm3) a solution of B(C6F5)3 (0.250 g, 0.488 mmol) in dichloromethane (15 cm3) was slowly added. Stirring was maintained for 48 h after which time all solid material had dissolved and the solution had changed from orange to red. Volatiles were removed in vacuo to yield a brown oily solid which was rendered as an orange powder by trituration with pentane (40 cm3). The yellow microcrystalline solid was obtained analytically pure by cooling a solution in dichloromethane (15 cm3) to 280 8C.Yield: 0.251 g (60%). [Mo{NB(C6F5)3}(S2CNEt2)3] 7. To a stirred suspension of [Mo(N)(S2CNEt2)3] (0.250 g, 0.451 mmol) in dichloromethane (30 cm3) a solution of B(C6F5)3 (0.245 g, 0.479 mmol) in dichloromethane (15 cm3) was slowly added. Stirring was maintained for 48 h after which time all solid material had dissolved and the solution had changed from brown to red.Volatiles were removed in vacuo to yield a brown-red oil. This failed to crystallise from a solution in dichloromethane–pentane (30 cm3 of a 1 : 4 mixture) and was rendered as a solid by sonication for 15 min in pentane (30 cm3). The red-brown foamy solid product was isolated by filtration and dried overnight in vacuo. Yield: 0.101 g (21%). [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] 8. To a stirred solution of [NBun 4][Os(N)(1,2-S2C6H4)2] (0.450 g, 0.619 mmol) in dichloromethane (40 cm3), B(C6F5)3 (0.450 g, 0.879 mmol) in dichloromethane (20 cm3) was added.An immediate change from yellow to deep red was observed and after 1 h of stirring the volatiles were removed under vacuum. The resulting oily green solid was triturated with pentane (20 cm3) to yield the product. It was isolated analytically pure as an olive-green powder by filtration and drying under vacuum. Yield: 0.675 g (88%). [Os{NB(C6F5)3}{1,2-(S)(SMe)C6H4}(1,2-S2C6H4)] 9. The complex [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] 8 (200 mg, 0.160 mmol) and MeO3SCF3 (50 mg, 0.305 mmol) were combined in a dry-box and dissolved in dichloromethane (15 cm3).The reaction mixture was stirred for 1 h without any obvious colour change and then the volatiles were removed under vacuum. Extraction of the oily residues with toluene yielded a red solution. Removal of the solvent from this aVorded the product as an olive-green oil. Vigorous washing with pentane (30 cm3) failed to yield a solid so the product was characterised3946 J.Chem. Soc., Dalton Trans., 1998, 3941–3946 by NMR spectroscopy. It was too air-sensitive to allow satisfactory microanalytical data to be obtained. Reactions with L 5 THF, NEt3 or PMe3 [Re{NB(C6F5)3}(PMe2Ph)(S2CNMe2)2] 3. To a solution of [Re{NB(C6F5)3}(PMe2Ph)(S2CNMe2)2] 3 (20 mg, 0.018 mmol) in dichloromethane (10 cm3) was added an excess of Lewis base; either THF (3 drops), NEt3 (3 drops) or PMe3 (1 cm3 of a 0.105 M solution in light petroleum, 0.105 mmol).No immediate colour change was observed and the reactions were allowed to proceed for 1 h. Volatiles were then removed in vacuo and the residues dried for 2 h. The products were analysed by 1H and 11B-{1H} NMR spectroscopy in CDCl3 and this showed that in all three experiments no reaction of compound 3 had occurred. [Mo{NB(C6F5)3}(S2CNMe2)3] 6. To a solution of [Mo{NB- (C6F5)3}(S2CNMe2)3] 6 (20 mg, 0.020 mmol) in dichloromethane (10 cm3) an excess of Lewis base was added as above.Little immediate colour change was observed and the reactions were allowed to proceed for 1 h. Further treatment and NMR analysis as above showed that in the case where L = THF no decomposition of compound 6 had occurred whereas when L = NEt3 or PMe3 the residue consisted of ca. 50% 6 and 50% [Mo(N)(S2CNMe2)3] plus B(C6F5)3?L. NMR data (CDCl3, 298 K): B(C6F5)3?NEt3, 1H, d 1.46 (m, 9 H, NCH2CH3) and 3.60 (m, 6 H, NCH2CH3); 11B-{1H}, d 24.2 (s); B(C6F5)3?PMe3, 1H, d 1.79 (d, 2JPH = 13.1 Hz, PCH3); 11B-{1H}, d 24.4 (s) [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] 8.To a solution of [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] 8 (20 mg, 0.016 mmol) in dichloromethane (10 cm3) an excess of Lewis base was added as above. Little immediate colour change was observed and the reactions were allowed to proceed for 1 h. Further treatment and NMR analysis as above showed that in the case where L = THF no decomposition of compound 8 had occurred whereas when L = NEt3 or PMe3 the residue consisted entirely of [NBun 4][Os(N)(1,2-S2C6H4)2] 9 and B(C6F5)3?L (NMR spectroscopic data as above).Reaction of [NBun 4][Os{NB(C6F5)3}(1,2-S2C6H4)2] 8 with [Ph3C][BF4] Complex 8 (50 mg, 0.040 mmol) and [Ph3C][BF4] (50 mg, 0.151 mmol) were combined as solids and dissolved in dichloromethane (15 cm3). The mixture was stirred for 30 min after which it appeared to have darkened slightly. The volatiles were removed in vacuo and the whole of the reaction residues analysed by 1H, 11B-{1H} and 13C-{1H} NMR spectroscopy in CDCl3. This confirmed the formation of the known compound [Os(NCPh3)- (1,2-S2C6H4)2],9 B(C6F5)3 and [NBun 4][BF4].Crystallography Single crystals of complex 3 suitable for analysis by X-ray crystallography were grown by slow vapour diVusion of pentane into a solution of 3 in dichloromethane at 298 K. A plate-shaped crystal was selected for diVraction, covered with paratone-N oil under an inert atmosphere and mounted on the end of a glass fibre.Crystal data. C32H23BF15N3PReS4 3, M = 1090.75, triclinic, space group P1� , a = 8.871(5), b = 13.233(1), c = 16.7220(13) Å, a = 80.73(4), b = 77.13(5), g = 86.05(5)8, V = 1887.6 Å3, Z = 2, Dc = 1.92 g cm23, m = 3.62 mm21, purple crystals, crystal dimensions 0.25 × 0.05 × 0.05 mm. Data collection and processing. Data were collected at 125 K on an Enraf-Nonius DIP2000 image plate diVractometer with graphite monochromated Mo-Ka radiation (l = 0.71069 Å). 11663 Reflections were measured (1 < q < 268, ±h, ±k, 1l, 6103 unique giving 5408 with I > 3s(I). The images were processed with the DENZO and SCALEPACK programs.21 Structure solution and refinement. All solution, refinement and graphical calculations were performed using the CRYSTALS22 and CAMERON23 software packages. The structure was solved byirect methods using the SIR 92 program24 and refined by a full-matrix least squares procedure on F.All non-hydrogen atoms were refined with anisotropic displacement parameters. All hydrogen atoms were generated and allowed to ride on their corresponding carbon atoms with fixed thermal parameters. A Chebychev weighting scheme with the parameters 2.84, 0.362 and 2.06 was applied as well as an empirical absorption correction.25 This yielded R = 0.042 and R9 = 0.051 with maximum residual electron density of 1.61 e Å23. CCDC reference number 186/1188. See http://www.rsc.org/suppdata/dt/1998/3941/ for crystallographic files in .cif format.Acknowledgements We thank St John’s College for a Junior Research Fellowship (to L. H. D.) and the EPSRC for support of this work. References 1 A. N. Chernega, A. J. Graham, M. L. H. Green, J. Haggitt, J. Lloyd, C. P. Mehnert, N. Metzler and J. Souter, J. Chem. Soc., Dalton Trans., 1997, 2293. 2 J. R. Galsworthy, M. L. H. Green, N. Maxted and M. Müller, J. Chem. Soc., Dalton Trans., 1998, 387. 3 J.R. Galsworthy, M. L. H. Green, M. Müller and K. Prout, J. Chem. Soc., Dalton Trans., 1997, 1309. 4 J. R. Galsworthy, J. C. Green, M. L. H. Green and M. Müller, J. Chem. Soc., Dalton Trans., 1998, 15. 5 J. Chatt and B. T. Heaton, J. Chem. Soc. A, 1971, 705. 6 S. Ritter and U. Abram, Z. Anorg. Allg. Chem., 1996, 622, 965. 7 S. Ritter and U. Abram, Inorg. Chim. Acta, 1995, 231, 245. 8 M. W. Bishop, J. Chatt, J. R. Dilworth, B. D. Neaves, P. Dahlstrom, J. Hyde and J. Zubieta, J. Organomet. Chem., 1981, 213, 109. 9 D. Sellmann, M. W. Wemple, W. Donaubauer and F. W. Heinemann, Inorg. Chem., 1997, 36, 1397. 10 T. J. Crevier and J. M. Mayer, Angew. Chem., Int. Ed. Engl., 1998, 37, 1891. 11 J. Chatt, J. D. Garforth, N. P. Johnson and G. A. Rowe, J. Chem. Soc., 1964, 1012. 12 S. Ritter and U. Abram, Z. Anorg. Allg. Chem., 1994, 620, 1443. 13 C.-H. Yang, J. A. Ladd and V. L. Goedken, J. Coord. Chem., 1988, 18, 317. 14 W. Kafitz, F. Weller and K. Dehnicke, Z. Anorg Allg. Chem., 1982, 490, 175. 15 A. G. Massey and A. J. Park, J. Organomet. Chem., 1966, 5, 218. 16 J. Karl, G. Erker and R. Fröhlich, J. Am. Chem. Soc., 1997, 119, 11165. 17 E. Forsellani, U. Casellato, R. Graziani and L. Magon, Acta Crystallogr., Sect. B, 1982, 38, 3081. 18 R. Dantona, E. Schweda and J. Strähle, Z. Naturforsch., Teil B, 1984, 39, 733. 19 J. Chatt and J. R. Dilworth, J. Indian Chem. Soc., 1977, 54, 13. 20 A. G. Massey and A. J. Park, J. Organomet. Chem., 1964, 2, 245. 21 Z. Otwinowski and W. Minor, Methods Enzymol., 1996, 276, 307. 22 D. J. Watkin, C. K. Prout, J. R. Carruthers and P. W. Betteridge, CRYSTALS User Guide, Issue 10, Chemical Crystallography Laboratory, University of Oxford, 1996. 23 D. J. Watkin, C. K. Prout and L. J. Pearce, CAMERON, Chemical Crystallography Laboratory, University of Oxford, 1996. 24 A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi, M. C. Burla, G. Polidori and M. Camalli, SIR 92, Program for automatic solution of crystal structures by direct methods, J. Appl. Crystallogr., 1994, 27, 435. 25 N. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983, 39, 158. Paper 8/05425H