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J. CHEM. SOC. DALTON TRANS. 1994 2025New Synthetic Routes to Face-to-face and Open-bookTriazenide-bridged Dirhodium Bipyridyl Complexes withthe [Rh,I4+ Core*Neil G. Connelly,B Till Einig,= Gabriel Garcia Herbosa,a Philippa M. Hopkins,aCarlo Mealli,b A. Guy Orpen,a Georgina M. Rosaira and Fernando Viguriaa School of Chemistry, University of Bristol, Bristol BS8 1 TS, UKI- 50 I32 Firenze, Italylstituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione, C.N. R.,The iodide-abstraction reaction of [{Rh,(p-I)(CO)(bipy)(p-RNNNR),},] [PF,], 1 (bipy = 2,2'-bipyridyl,R = p-tolyl) with AgPF, in MeCN gave [Rh,(CO)(NCMe),(bipy)(p-RNNNR),] [PF,], 2 which slowlydecarbonylated at room temperature to [Rh (NCMe),(bipy)(p-RNNNR),] [PF,], 3. The crystal structureof 3 shows a Rh-Rh single bond [2.534(2) A] and one of the three terminal nitrile ligands axially attachedto the bipy-bound rhodium atom.Complex 3 reacts with Na[S2CNMe,]-2H2O to give [Rh,-(NCMe)(S,CNMe,)(bipy)(p-RNNNR),] [PF,] 4. In CH,CI,, the iodide-abstraction reaction of 1 affords agreen solution containing a carbonyl complex [Rh,(CO)(~olv),(bipy)(p-RNNNR)~]~+ A (soh = CH,CI,),an analogue of 2. Complex A (solv = CH,CI,) reacted with neutral chelating ligands to give the carbonyl-bridged complexes [Rh,(p-CO)(L-L)(bipy) (p-RNNNR),] [PF,], [L-L = bipy 5, 4.4'-dimethyl-2,2'-bipyridyl (dmbipy) 6, 1 ,I 0-phenanthroline (phen) 7, di-2-pyridylamine (dpa) 8, or Ph,PCH,CH,PPh,(dppe) 91 the last of which undergoes reduction with NaBH, to give paramagnetic [Rh,(CO)(dppe-P) (bipy) (p-RNNNR),] [PF,] 11 having a face-to-face structure with a monodentate dppe ligand.WithPh,PCH,PPh, (dppm), A (solv = CH,CI,) afforded [Rh,(p-CO)(dppm) (bipy)(p-RNNNR),] [PF,], 10aX-ray studies on which, as a CH,CI, solvate, reveal a carbonyl-bridged open-book structure with a Rh-Rhdistance of 3.1 79(2) A and a large Rh-C(0)--Rh angle of 108.3". Complex 10a equilibrates with the face-to-face, terminal carbonyl isomer [Rh,(CO) (dppm) (bipy) (p-RNNNR),] [PF,], 10b in solution. Theelectronic structures of the two isomers have been probed by extended- H uckel molecular-orbitalcalculations on the model compound [Rh,H,(CO),]. These show (i) the absence of metal-metal bondingin 10a while 10b has a Rh-Rh c bond, and (ii) that the CO in 10a is best viewed as more ketonic than atypical bridging carbonyl. The reaction of complex A (solv = CH,CI,) with neutral chelating ligands alsogives low yields of [{Rh,(CO)(O,PF,)(p-O,PF,)(bipy)(p-RNNNR),},] 12 the crystal structure of whichshows two dirhodium fragments [Rh-Rh 2.505(4) A] linked by two O,PF, groups bridging acrossaxial and equatorial sites in different [Rh,],' moieties.The reaction of A (soh = CH,CI,) withN-SH ligands yields [Rh,(CO)(N-S)(bipy)(p-RNNNR),] [PF,] (N-S = 1 -methyl-2-sulfanylimidazolate13, 2-sulfanylpyrimidinate 14, 2-sulfanylthiazolinate 15, or 2-sulfanylbenzimidazolate 16). and NaXgives [Rh,(CO)X,(bipy)(p-RNNNR),] (X = CI or NO,).We have previously shown that [Rh,(CO),(bipy)(p-RNNNR),] (bipy = 2,2'-bipyridyl, R = p-tolyl) is activatedtowards carbonyl substitution by one-electron oxidation,the resulting paramagnetic monocation [Rh,(CO),(bipy)(p-RNNNR)J+ acting as the precursor to a wide variety of[Rh213 +-and [Rh2l4+-containing complexes in which twosquare-planar rhodium centres are retained in a face-to-facearrangement. We now give details2 of how the halide-abstraction reactions of one such [Rh2l4' complex, namelylead to a considerable expansion of the range of redox-activedirhodium complexes and, in particular, to novel carbonyl-bridged complexes with dn 'open-book' rather than face-to-face[Rh214+ core.[(Rh2(~L-1)(Co>(bipy>(CI-RN"R),) 21 [PF6i 2 (R = p-tolyl),Results and DiscussionThe addition of AgPF, to [{ Rh,(p-I)(CO)(bipy)(p-RNNNR),},][PF,], 1 (R = p-tolyl) in acetonitrile results in* Supplementary data available: see Instructions for Authors, J.Chem.Soc., Dalton Trans., 1994, Issue 1 , pp. xxiii-xxviii.the precipitation of AgI and the formation of an orange solutionfrom which green [Rh2(CO)(NCMe),(bipy)(p-RNNNR)2]-[PF,], 2 (better prepared in a purer form by the route describedbelow) may be isolated on addition of diethyl ether. Thestructure of complex 2 (Scheme 1) was deduced from theelemental analysis (Table l), from the observation of onecarbonyl band in the IR spectrum (at 2086 cm-'), and from the'H NMR spectrum (Table 2) which showed the presence of twoinequivalent pyridyl rings (of the bipy ligand), two inequivalentnitrile ligands (one axial and one equatorial with respect to therhodium-rhodium bond), and three different methyl resonancesassociated with the tolyl substituents of the triazenide bridges.The two nitrile ligands are assumed to be co-ordinated to thesame rhodium atom, by comparison with the structure of theprecursor 1 (but see below).Once formed, complex 2 reacts further in MeCN.Thereaction is slow at room temperature but more rapid in boilingacetonitrile; after 12 h the reaction mixture shows no carbonylband in the IR spectrum, indicating complete loss of co-ordinated CO. Addition of diethyl ether to the acetonitrilesolution gave the product 3 as an air-stable green powder ingood yield. The C, H and N analyses (Table 1) were consistentwith the formulation [Rh2(NCMe),(bipy)(p-RNNNR),]2026 J.CHEM. soc. DALTON TRANS. 19942 L = MeCN /2+(ii) -3 L = MeCN2+(iii) -4 L = MeCN5 - 1 0 1 Ob L-L = dppm 13 - 16 17- 19Scheme 1 N-N = bipy, R = p-tolyl. (i) AgPF6 in MeCN; (ii) MeCN, heat; (iii) Na[S,CNMe,]; (iu) AgPF, in CHzC12; (u) L-L = bipy, dppe, efc.;(ui) water; (uii) N-S = msim, etc.; (uiii) NaX, X = CI or NO2Table 1 Analytical data for dirhodium triazenide complexes (R = p-tolyl)Analysis (%)YieldComplex (%) Colour ij(CO)"/cm-' C H N~RhZ(Co)(NCMe)Z(bi~~)(~-RN"R)Z~~pF6~2 60 Green 2090 42.3 (42.7) 3.6 (3.5) 11.4 (1 1.6)3 CRhZ(NCMe),(bipy)(p-RN"R)21CPF61 Z 82 Green - 42.9 (43.2) 3.7 (3.7) 12.4 (12.6)4 [Rh2(NCMe)(S,CNMe2)(bipy)(p-RNNNR),][PF6] 77 Brown - 45.9 (46.3) 3.9 (4.1) 12.1 (12.5)5 CRhZ(~-Co>(bipy)Z(CI-RN"R)21 CPF61Z 53 Green 1769 46.0 (45.8) 4.0 (3.4) 10.4 (10.1)~ R h Z ( ~ - C o ) ( d m b i ~ ~ > ( b i ~ ~ ) ( ~ - R N N " ) Z ~ ~ p F 6 ~ Z 74 Green 1777 46.5 (46.6) 3.8 (3.7) 10.5 (10.7)7 [RhZ(~-Co)(phen)(biPY)(C(-R"NR)21[pF612 72 Green 1777' 46.8 (46.8) 3.7 (3.4) 10.5 (10.7)C R h Z ( ~ - C o ) ( d ~ a ) ( b i ~ ~ ) ( ~ - R N N " ) Z ~ ~ p F 6 ~ 2 68 Green 1774' 46.0 (46.1) 3.9 (3.9) 11.3 (11.4y9 [Rh2(~L-Co)(dppe)(biPY)(~-RNNNR)Zl CPF6i 2 79 Green 1760' 51.0 (51.1) 3.9 (3.9) 7.3 (7.3)10 CRhz(~-Co)(d~~m)(bip~)(p-RNNNR),I CPF612 76 Green 17583, 49.5 (49.8) 3.8 (3.8) 7.3 (7.2)'1 1 [Rh2(Co)(dppe-P)(bipy)(~-RN"R)Zl CPF6i 80 Brown 2016 55.3 (55.2) 4.7 (4.3) 7.8 (7.9)'13 [Rhz(C0)(msim)(bipy)(p-RN"R),][PF6] 71 Green 2065 47.0 (47.1) 3.7 (3.7) 12.7 (12.8)14 [RhZ(CO)(spym)(bipy)(~-RNN")21 CPF6i 74 Green 2067 46.0 (45.9) 3.7 (3.5) 12.0 (12.3)g70 Green 2064 45.8 (45.8) 3.6 (3.6) 11.2 (1 1.4)47.6 (47.5) 3.9 (3.5) 11.7 (1 1.9)' 16 [R h,(CO)(sbzim)( bipy)( p-RNNNR),] [PF,] 77 Green 206517 [Rh2(CO)C12(bipy)(p-RN"R)2] 71 Green 2038 51.6 (51.5) 4.2 (4.0) 12.1 (12.3)19 CRhz(Co)(Noz)2(biPY)(CI-RNN")zl 70 Brown 2043 50.0 (50.4) 3.8 (3.9) 15.0 (15.1)a In CH,CI, unless stated otherwise; s = strong, mw = medium weak.for a 0.75 OEt, solvate (confirmed by 'H NMR spectroscopy).(confirmed by 'H NMR spectroscopy).2070mw15 CRhz(CO)(stz)(biPY)(~-RN"R)21CPF,lCalculated values in parentheses. ' In MeCN.' In MeNO,. CalculatedCalculated for a 0.5 CHzC12 solvate Calculated for a 0.5 CH,CI, solvate.[PF,], and both the 'H and 13C NMR spectra (Table 2) showthe presence of three acetonitrile ligands in the ratio 2 : 1.The'H signals for the methyl groups of the triazenide bridges occuras two singlets, in a 1 : 1 ratio, and those for the CdH4 groupsappear as pseudo-triplets (each due to the overlapplng of twodoublets). The signals for the bipyridyl protons are observed inthe ratio 2 : 2 : 2 : 2 showing the pyridyl groups to be equivalent.Taken together, these data are consistent with a structure for 3having a mirror plane including the Rh-Rh axis and bisectingthe planes of the two triazenide bridges. However, the NMRspectra do not define which axial site the third nitrile ligandoccupies. An X-ray diffraction study was therefore carried outon crystals grown by slow diffusion of diethyl ether into anacetonitrile solution of 3J.CHEM. SOC. DALTON TRANS. 1994 2027The structure of the dication of complex 3 is shown in Fig. 1and selected bond lengths and angles are listed in Table 3. TheX-ray diffraction study confirms the presence of three co-ordinated acetonitriles, However, the structure differs from thatof 1 in that although two of the nitrile ligands are equatoriallybound to Rh(2) the third is axially bound to Rh( 1) (i.e. therhodium atom also bearing the bipy ligand). Both rhodiumatoms have near-planar equatorial co-ordination, with a greatermean deviation from the plane at Rh(2) (0.0283 A) than atRh(1) (0.0178 A). The smaller deviation at Rh(1) is possiblyTable 2 Proton and ' 3C NMR spectroscopic data for dirhodium triazenide complexes'Me' MeCompound234789'Hthe1.81 (3 H, s, MeCN), 2.07 (3 H, s, MeCN), 2.27 (3 H, s, C,H,Me), 2.28(3 H, s, C6H4Me), 2.35 (6 H, s, C,H,Me), 7.12-7.42 (16 H, C,H4Me),8.00 (2 H, m, H2), 8.49 (2 H, m, H3), 8.73 [I H, d, J(H4H3) 7, H4 orH"'], 8.76 [lH, d, J(H4H3) 7, H4 or H"'], 9.13 [l H, d, J(H'H2) 5, H'or H"], 9.20 [l H, d, J(H'H2) 5, H' or HI']1.80 (3 H, s, MeCN), 2.06 (6 H, s, MeCN), 2.28 (6 H, s, C,H,Me), 2.32rn-H Of C&Me), 7.90 [2 H, t, J(H2H3) 8, J(HZH') 6, H'], 8.41 [2 H,t, J(H3H2) 8, H3], 8.68 [2 H, d, J(H4H3) 8, H"], 8.98 [2 H, d, J(H'HZ)6, H'lb(6 H, S, C,H,Me), 7.13 (8 H, d, J 9 , O-H Of C,H,Me), 7.36 (8 H, t, J 9,1.83 (3 H, s, MeCN), 2.26 (1 2 H, m, C,H,Me), 2.77 (3 H, s, S,CNMe,),3.02 (3 H, s, S,CNMe,), 7.08 (18 H, m, C,H,Me, H2), 8.13 (2 H, m,H3), 8.29 [l H, d, J(H'H2) 5, H' or HI'], 8.38 r l H, d, J(H1H2) 5, H'or H"], 8.40 [l H, d, J(H4H3) 8, H4 or H"'], 8.46 [l H, d, J(H4H3) 8,H4 or H4']2.27 (12 H, s, C,H,Me), 7.09 [8 H, dd, J(HH) 8, J(HRh) 2, o-H ofC,H,Me], 7.21 [8 H, dd, J(HH) 8, J(HRh) < 1, m-H of C,H,Me],7.49 [2 H, ddd, J(HH) 9, 6, 1.5, H*], 8.21 [2 H, ddd, J(HH) 9, 8, 1.5,H3], 8.24 [2 H, d, J(H'H2) 6, H'ld2.27 (12 H, s, C,H,Me), 2.52 (6 H, s, Me of dmbipy), 7.08 [8 H, dd,J(HH) 8, J(HRh) < 1, m-H of C,H,Me], 7.19 [8 H, dd, J(HH) 8,J(HRh) 2, o-H Of C,H4Me], 7.30 [2 H, d, J(H7H6) 6, H'], 7.49 [2 H,ddd, J(HH) 9,7,1.5, H2], 8.05 [2 H, d, J(H6H7) 6, H6], 8.20 [2 H, ddd,J(HH) 9, 8, 1.5, H3], 8.23 [2 H, d, J(H'HZ) 7, H'], 8.26 (2 H, s, H9),8.41 [2 H, dd, J(HH) 8, 1, H4Id2.27 (6 H, S , C&Me), 2.28 (6 H, S , C&kfe), 7.10 [8 H, d, J(HH), 8, m-H of C,H,Me], 7.26 [8 H, dd, J(HH) 8, J(HRh) 1.5, o-H of C,H,Me],7.47 [2 H, ddd, J(HH) 8, 5, 1.5, H2], 7.80 [2 H, dd, J(HH) 8, 5, H'],8.16 [2 H, td J(HH) 8, 1.5, H3], 8.19 (2 H, s, H"), 8.26 [2 H, d,J(H'H2) 5, H'], 8.34 [2 H, d, J(H4H3) 8, H4], 8.54 [2 H, td, J(HH) 5,1, H6], 8.77 [2 H, dd, J(HH) 8, 1, H8]2.24 (6 H, s, C6H4Me), 2.28 (6 H, s, C,H,Me), 6.92 [S H, d, J(HH) 8,rn-H of C,H,Me], 7.06 [lo H, m, o-H of C,H4Me, H7], 7.35 [2 H, d,J(H9H8) 8, H9], 7.73 [2 H, d, J(H6H7) 6, H6], 7.80 [2 H, ddd, J(HH)8,6, 1, H2], 7.90 [2 H, td, J(HH) 8, < 1, H8], 8.41 [2 H, td, J(HH) 8, 1,H3], 8.66 [2 H, d, J(H"H3) 8, H"], 8.73 [2H, d, J(H'H2) 6, HI], 9.27 (1H, s, NH)bdppe), 6.71 [4 H, d, J(HH) 8],6.86 [4 H, dd, J(HH) 8, 12J6.93 [8 H, d,H, m, H2, H"), 8.23 [2 H, td, J(HH) 8,2, H3], 8.38 [2 H, d, J(H4H3) 8,2.15 (6 H, S, C,H,Me), 2.34 (6 H, S , C&4ML.), 3.00 (4 H, m, CH, ofJ(HH) 81, 7.13-7.37 (20 H, m) (C6H4Me and 0-, m-H of PPh), 7.56 (4~~13.3, 3.4 (MKN), 21.0, 21.1 (C,H,Mt?), 122.0, 123.0,124.5, 125.2 (m-C Of C6H4Me), 122.4, 126.4 (MeCN),126.4, 127.0 (C"), 128.9, 129.5 (C2), 129.7, 129.9,c Of C,H&k), 142.4, 142.8 (c')), 146.4, 146.7, 147.0,147.9 (ips0-C of C6H4Me), 153.5, 154.0 (c'), 157.4,157.6 (C'), 179.7 [d, J(C'03Rh) 61, CO]'2.8 (MeCN), 4.0 (MeCN), 21.4 (C,H,Me), 120.4(MeCN), 124.4, 125.9 (m-C Of C6H4Me), 126.3 (C"),126.6, 126.7 (MeCN), 129.7 (C2), 130.8, 131.2 (o-C of130.4, 130.7 (0-c Of C,jH,Me), 137.2, 138.1, 138.4 ( p -C6H4Me), 138.2, 138.3 (p-c Of C6H4Me), 143.0 (c')),149.4, 149.7 (Ms0-C O f C6H4Me), 155.6, 155.7 (c'),159.3 (C5)b3.6 (MeCN), 20.7 (C6H4Me), 37.9, 38.3 (S,CNMe,),123.2, 123.5 (m-C of C,H,Me), 124.2 (MeCN), 127.2,127.6(o-CofC,H4Me), 129.1 (c"), 129.5 (S,CNMe,,c 2 ) , 139.1, 139.2 (p-c Of C,&Me), 140.3 (c3), 152.2,153.4 (@SO-c Of C6H4Me), 157.6, 157.7 (c'), 158.020.9 (C,H,Me), 123.8 (m-C Of C6H4Me), 125.9 (c"),128.9 (c'), 130.9 (o-c Of C,H4Me), 138.5 (p-c ofC,H,Me), 142.6 (c3), 146.8 (QS0-C Of C6H4Me),21.4, 22.1 C,H,Me), 124.3 (m-C O f C,H,Me), 126.7(c"), 127.3 (c9), 130.3 (c7), 132.0 (0-c Of C6H4Me),139.8 (p-c Of C,H&k), 143.5 (c3), 147.6 (ips0-C ofC,H,&fe), 153.3, (c'), 154.2 (c6), 157.1 (c'), 158.1,158.7 (C8, C'O), 182.1 [t, J(C'03Rh) 46, CO](C')153.3 (C'), 157.7 (C'), 186.0 [t, J(Clo3Rh) 48, CO]''d21.4 (C,H,Me), 124.4, 124.6 (m-C Of C,)I4Me), 126.6(c"), 128.0 (c7), 129.9 (c'), 132.1 (0-c Of C6H4Me),133.6 (c9), 139.9, 140.0 (p-c Of C,H4Me), 142.6(c"), 143.5 (c')), 147.6 (@SO-c O f C6H4Me), 148.9(C'), 154.2, 154.3 (C''), 155.1 (C'), 158.1 (C'), 181.6[t, J(C'03Rh) 49, CO]21.4 (C,H,Me), 117.2, 123.2 ( c 7 , c9), 124.1 (m-C OfC6H4Me), 127.0 (c"), 130.1, (c'), 131.1 (0-c OfC&Me), 139.7, 139.9 (p-c Of C,H4Me), 143.8,144.1 (c3, c8), 147.0, 147.4 (@so-c O f C,H4Me),153.3 (C'), 153.8 (C6), 159.0 (Cs, C'O), 184.7 [t,J(C'03Rh) 48, CO]21.4, 21.6 (C,H,Me), 28.8 [d, J(C3'P) 45, CH, ofdppe], 124.7, 126.2 (m-c of C,H,Me), 126.3 (c"),128.9 [d, J(C3'P) 52, ip~0-C of C,H,P], 130.0 (C2),131.1 (@SO-c Of C,H,P), 131.3, 131.4, 131.7, 131.8,C6H'P; 0-c Of C,H,Me), 140.2 (p-c Of C6H4Me),143.5 (c')), 147.0, 148.7 (iPS0-c O f C,H,Me), 154.1133.9, 134.4, 134.6, 134.7, 134.8 (o-, m-, p-C of(C'), 158.1 (C5)2028 J.CHEM. SOC. DALTON TRANS. 1994Table 2 (continued)Compound 'H 3c101314151617192.19 (6 H, s, C6H4Me), 2.36 (6 H, s, C6H4Me), 4.56 (1 H, ddd, br, CH,of dppm), 4.90 (1 H, ddd, br, CH, of dppm), 6.86 [4 H, dd, J(HH) 8,12],7.04(8 H,m), 7.15 [4H, d,J(HH) 8],7.30-7.66(20 H, mand H2)(C6H4Me and PPh), 8.00 [2 H, d, J(H'H2) 5, H'], 8.34 [2 H, td, J(HH)8, 1, H3], 8.52 [2 H, d, J(H4H3) 8, H4]2.15 (3 H, s, C6H4Me), 2.24 (6 H, S, C6H4Me), 2.41 (3 H, s, C,H4Me),3.06 (3 H, s, NMe), 5.79 [l H, d, J(H6H7) 2, H6], 5.97 [l H, d, J(H7H6)2, H7], 6.72 (4 H, m), 6.98 [2 H, d, J(HH) 81, 7.05 [2 H, d, J(HH) 81,7.24 [2 H, d, J(HH) 8],7.26 [2 H, d, J(HH) 8J7.31 [2 H, d, J(HH) 816, 1, H2'], 8.22 (1 H, m, H3 or H3'), 8.27 (1 H, m, H3 or H3'), 8.31 [l H,d, J(H'H2) 6, H' or H"], 8.42 [l H, d, J(H'H2) 6, H' or H"], 8.44[l H, d, J(H4H3) 8, H4pr H4'], 8.49 [l H, d, J(H4H3) 8, H4 or H4']2.12 (3 H, s, C6H4kfe), 2.23 (6 H, s, C6H4Me), 2.41 (3 H, s, C6H4Me),6.33 [l H, t, J(H7H6) 5, H7], 6.75 [2 H, d, J(H6H7) 5, H6], 6.80 [2 H,d, J(HH) 8],6.91 [2 H, d, J(HH) 8],7.02 [2 H, d, J(HH) 8],7.12 [2 H,d, J(HH) 8],7.39 [2 H, d, J(HH) 8],7.50 [2 H, d, J(HH) 8],7.62 [4 H,d, J(HH) 81 (C,H4Me), 7.64 (1 H, m, H2), 7.72 [l H, t , J(HH) 8, H2'],8.1 (2H, br,H6andH6'),8.31 [l H, t,J(HH)8,H30rH3'],8.37[1 H, t,J(HH) 8, H3 or H3'], 8.42 [l H, d, J(H'H2) 6, H' or H"], 8.55 [l H, d,J(H'H2) 6, H' or H"], 8.58 [l H, d, J(H4H3) 8, H" or H4'], 8.62 [ 1 H,d, J(H4H3) 8, H4 or H4']2.08 [l H, q, J(HH) 10, H6], 2.24 (6 H, s, C,H4Me), 2.27 (3 H, s,2.78 [l H, ddd,J(HH) 8,4,12, H7], 3.43, [ 1 H, ddd, J(HH) 8,4,13, H7'],7.00 [4 H, d, J(HH) 8, m-H Of C,H4Me], 7.02 [4 H, d, J(HH) 8, o-H ofC6H4Me], 7.23 [4 H, d, J(HH) 8, m-H of C6H4Me], 7.30 [2 H, d,J(HH) 8, o-H of C6H4Me], 7.39 [2 H, d, J(HH) 8, o-H of C6H4Me],7.46 [l H, t, J(H2H') 8,6, H2], 7.57 [l H, t, J(H2'H'') 8,6, H"], 8.20 [lH, td, J(HH) 8, c 1, H3 or H3'], 8.28 [l H, td, J(HH) 8, c 1, H3 or H3'],8.25[1 H,d,J(H'H2)6,H'orH''],8.35[1 H,d,J(H'H2)6,H' orH"],8.46 [l H, d, J(H3H4) 8, H4 or H4'], 8.51 [l H, d, J(H3H4) 8, H4 or H4']2.48 (3 H, s, C,H,Me), 5.29 [l H, d, J(H8H7) 8, H8], 6.68 [l H, t ,J(HH) 8, H7], 6.88 [l H, d, J(HH) 8, H"], 6.89 [l H, m, J(HH) 8,H7'], 6.40 [2 H, d, J(HH) 81, 6.99 [2 H, d, J(HH) 81, 7.05 [2 H, d,J(HH) 8],7.23 [2 H, d, J(HH) 8],7.31 (6 H, m), 7.49 [l H, t , J(HH) 8,6, H2'], 7.59 (3 H, m and H2), (C,H4Me), 8.18 [l H, t, J(HH) 8, H3 orH3'], 8.23 [l H, t, J(HH) 8, H3 or H3'], 8.35 [l H, d, J(H'H2) 6, H'],8.41 [l H, d, J(H4H3) 8, H4 or H4'], 8.46 [l H, d, J(H4H3) 8, H4 orH4'], 8.47 [l H, d, J(H'H2) 6, H"], 9.24 (1 H, s, NH)2.24 (3 H, s, C,H,Me), 2.25 (3 H, s, C6H4Me), 2.33 (6 H, s, C6H4Me),7.0-7.5 (16 H, C,H4Me), 7.41 (1 H, m, H2 or H2'), 7.51 (1 H, m, H2 orH2'), 7.95 C1 H, td, J(HH) 5,8,2, H3 or H3'], 8.02 [l H, td, J(HH) 5, 8,2, H3 or H3'], 8.10 [l H, d, J(H4H3) 8, H4 or H4'], 8.18 [l H, d,J(H4H3) 8, H4 or H"'], 8.79 [l H, d, J(H'H2) 6, H' or H"], 8.88 [l H,d, J(H'H2) 6, H' or H"](C,H,Me), 7.51 (3 H, m, O-H Of C,H,Me, H2), 7.58 [ 1 H, ddd, J(HH) 8,C,H,Me), 2.39 (3 H, S, C,H,Me), 2.54 [l H, ddd, J(HH) 8,4, 9, H6'],1.76 (3 H, S, C&Me), 2.23 (3 H, s, C,&fkfe), 2.24 (3 H, s, C,H,Me),21.4, 21.6 (C6H4Me), 39.3 [t, J(C3'P) 30, CH, ofdppm], 124.7, 125.3 (m-C of C,H,$k), 126.6 (C"),127.8 [d, J(c3'P) 53, Qs0-C Of C,H$], 130.0 (c'),131.1 (@SO-c O f C,H,P), 131.4, 131.5, 131.9, 132.1,134.4, 134.6 (0-, m-C O f C,H,P, 0-c Of C,H4Me),133.5, 133.6 @-c O f C~HSP), 140.0, 140.1 (p-c OfC6H4Me), 143.8 (c3), 147.6, 149.3 (Q30-c ofC,H,Me), 154.4 (c'), 158.1 (c5) b'r20.6, 20.8 (C,H,Me), 31.3 (NMe), 115.8 (C6), 129.5(c7), 121.4, 122.5, 122.8, 124.0 (m-C O f C6H4Me),124.1, 124.6 (C", C4'), 127.8, 128.4(C2), 128.3, 129.7,129.8, 130.0 (0-c O f C6H4Me), 135.2, 135.8, 136.6 (p- c O f C,H4Me), 140.5, 141.1 (c3, c3'), 147.7, 148.2,148.5, 148.7 (Qs0-C of C,H&k), 152.7, 153.7 (c',C"), 154.2 (C8), 157.4, 158.2 (C', C"), 184.4 [d,J(C'03Rh) 60, CO]'20.6, 20.7, 20.8 C,H,Me), 114.6 (c7), 121.9, 122.7,123.3, 124.0 (m-C O f C6H4Me), 124.1, 124.8 (c", c4'),O f C6H4Me), 135.6, 136.2, 136.3, 137.0 (p-C O f127.9, 128.4 (C', C2'), 129.0, 129.7, 130.0, 130.4 (o-CC6H4Me), 140.7, 141.2(C3, c3'), 147.2, 147.9, 148.3,148.5 (@so-C of CpH4Me), 151.6, 158.1 (C", C6'),152.5, 153.8(C1,C'), 157.4, 158.3(C5,C5'), 184.4[d,J(C'03Rh) 59, CO], 184.9 (C8)20.6,20.7,20.8 (C,H,kfe), 30.2 (c7), 56.2 (c6), 121.4,122.5, 122.9, 124.2 (m-C of C,H4Me), 124.1, 124.8(C4, C4'), 127.9, 128.5 (C2, C2'), 129.0, 129.8, 129.9,c O f C6H4Me), 140.7, 141.3 (c3, c3'), 147.9, 148.4,130.0 (0-c O f C6H4Me), 135.4, 136.0, 136.3, 136.8 ( p -148.7 (@so-C of CgH4Me),152.5, 153.5 (C', C"),157.5, 158.2, (C5, C5), 184.4 [d, J(C'03Rh) 59, CO],188.3 (C')20.3, 20.7, 20.8 (C,H,Me), 110.3 (c7), 112.4 (c6),115.2 (C')), 121.4, 123.1, 123.2, 123.3 (m-C ofC,H4Me), 123.4, 124.5 (C", C4'), 127.9, 129.4 (C',c2'), 128.5, 129.8, 130.0, 130.3 (0-c O f C6H4Me),135.3, 136.3, 136.9 @-C of C6H4Me), 140.7, 141.2(C3, C3'), 147.4, 148.1, 148.4, 149.9 (@so-C ofC&&k), 152.5, 153.9 (c', c"), 157.8, 158.2 (c',C"), 162.3 (C9), 184.9 [d, J(Clo3Rh) 59, CO]21.0, 21.1 (C,H,Me), 122.5, 123.1, 123.7 (m-C O fC,H,Me), 125.9, 126.2 (c", c"'), 128.6, 128.8 (c2,c"), 126.7, 127.1, 129.4, 129.8 (0-c O f C6H4Me),135.1, 136.1, 139.2, 139.8 (p-C of C,H4Me), 135.9,136.2 (C3, C3'), 148.0, 148.1, 149.1, 149.2 (@so-C ofC,H4Me), 153.8, 155.1 (c', c"), 157.2, 158.6 (c',CSjC2.23 (3 H, S, C,H,fkfe), 2.28 (3 H, S, C,H,Me), 2.36 (6 H, S, C6H4Me),7.067.39 (16 H, C6H4Me), 7.63 (2 H, m, H'), 8.09 (4 H, m, H3 andH4), 8.73 [l H, d, J(H'H2) 6, H' or H"], 8.99 [l H, d, J(H'H2) 6, H'or H"1a J values are in Hz; 2% MHz spectra, in CD,CI, unless stated otherwise.In CD,N02. 400 MHz spectrum. In CD3CN.due to the greater rigidity of the bipyridyl ligand. The Rh-Rhdistance of 2.534(2) 8, is comparable with that of the dication!J!j"h ( p-I)(CO)(bipy)(p-RNNNR)2)21"' [Rh-Rh 2.544( 1)and indicates a single M-M bond. The trans influence ofthe M-M bond is seen in the Rh-N distance of 2.080(9) A forthe axially co-ordinated acetonitrile. This is significantlylonger than the Rh-N distances for the equatorially boundgroups [2.032(8) and 2.01 l(8) 8, respectively]. Similardimensions for the Rh-Rh and Rh-N distances have recentlybeen observed in the closely related tetrakis(acetonitri1e)dication [Rh2(NCMe),(bipy)(p-O2CMe),l2 + which has twoaxial acetonitrile ligands but is otherwise similar to thedication in 3 [Rh-Rh 2.540(1), Rh-NCMe,, 2.209, Rh-N,,1.984 A].Elsewhere we have presented a frontier-orbital rationale forthe observed tendency for face-to-face complexes containingthe [Rh2I4+ core to co-ordinate additional ligands trans to theRh-Rh bond (i.e. in an axial site).The structure of 3, however,differs from that of [(Rh2(p-I)(CO)(bipy)(p-RNNNR)2}2]2 +,the only other [Rh2I4+ complex so far structurally charac-terised in the triazenide-bridged series, in that the latter has theaxial ligand, i.e. the bridging iodide, bound to Rh(2) (therhodium atom not carrying the bipyridyl ligand). The preferencefor co-ordination at one axial site rather than the other mostlikely results from electronic rather than steric factors; ligandaddition will occur at the more electron-deficient site.In allprevious complexes in this class prepared to date Rh(2) carriedat least one equatorial carbonyl ligand, the strong n-acceptoJ. CHEM. SOC. DALTON TRANS. 1994 2029Table 3 Selected bond lengths (A) and angles (") for complex 32.534(2)1.446(11)2.039(7)1.3 19( 13)2.009(8)1.339( 13)2.01 l(8)1.106( 14)1.532(14)1.555(10)Rh(2)-Rh( l)-N(l) 86.1(3)N( 1 )-Rh( 1 W ( 4 ) 88.3(3)N( 1)-Rh( 1)-N(7) 95.2(3)Rh(2)-Rh( l j N ( 8 ) 91.3(2)N(4)-Rh( 1)-"8) 96.4(3)Rh(2)-Rh( 1)-N(9) 172.3(2)N(4)-Rh( 1 W ( 9 ) 89.8(3)N(8FRh( l W ( 9 ) 86.1(3)Rh( l)-Rh(2)-N(6) 85.5( 3)Rh(l)-Rh(2)-N(lO) 99.9(3)N(3)-Rh(2 jN(11) 92.7(3)N(1O)-Rh(2 jN(11) 86.5(3)N(6)-Rh(2)-N( 10) 93.3( 3)1.598( 15)1.289(12)1.409(14)1.279( 13)2.053(7)1.4 1 6( 1 4)2.080(9)1.337(11)2.032(8)125.7(7)116.8(8)118.0(7)126.5(6)110.7(7)125.1 (7)113.2(7)1 15.0(6)114.8(6)120.0(8)176.4(9)177.1( 13)178.7( 14)1.1 12( 14)1.583(8)1.578(12)1.575(9)1.543( 14)1.432( 14)2.060(8)1.296(11)2.047(8)Rh(2)-Rh( 1)-N(4) 83.3(2)Rh(2)-Rh(l)-N(7) 93.6(3)N(4kRh( 1 )-N( 7) 1 75.1 (3)N( 1 )-Rh( 1 )-N(8) 174.3(3)N(7)-Rh( 1)-N(8) 79.9(3)N( 1)-Rh( 1)-N(9) 97.0(3)N(7)-Rh( 1 )-N(9) 93.1 (3)Rh( l)-Rh(2)-N(3) 83.0(3)N(3)-Rh(2)-N(10) 177.0(4)Rh(l)-Rh(2)-N(ll) 99.8(3)N(6FRh(2)-N(ll) 174.7(4)Rh( 1 )-N( 1 )-N(2) 1 2 1.8( 7)N( 3)-R h( 2)-N( 6) 87.3( 3)1.351(12)2.0 14(7)1.083( 16)1.558(8)1.537(13)1.487( 13)1 .53 1 ( 14)1.545( 12)1.300(13)1 1 1.3(8)1 28.2(7)113.8(8)122.4(7)116.1(7)119.7(6)126.1(6)119.0(8)1 25.2( 6)167.1(8)167.3( 12)179.0( 12)Fig.1 The molecular structure of the dication of complex 3 showingthe labelling scheme. All hydrogen atoms have been omitted for clarity;the rhodium atoms are shown as ellipsoids enclosing 50% probabilitydensityligand therefore making Rh(2) relatively electron poor. Withcomplete decarbonylation, the ligand set Rh(2)(NCMe), ismore electron rich than Rh( l)(bipy) and axial co-ordinationoccurs at the latter site.The cyclic voltammogram of complex 3 shows one diffusion-controlled, reversible reduction wave at 0.06 V and an ill definedoxidation wave at 1.29 V.These electron-transfer processesmost likely involve the formation of [Rh,13+- and [Rh2]'+-containing complexes respectively. However, in common withthe other new species described herein, the chemical andelectrochemical oxidation and reduction reactions of 3 arecomplicated and the results of these studies will be detailedelsewhere.Nitrile ligands are generally regarded as substitutionallylabile, [Rh,(NCMe)6(p-0,CMe)z]2 + reacting with bipy or1,lO-phenanthroline (phen) at room temperature to give, forexample, [Rh2(NCMe),(phen)(p-O2CMe),l2 +. In this reactioninitial substitution occurs at adjacent axial-equatorial positionsbut over a period of 48 h the diequatorially substituted isomeris formed. The axial nitrile ligands of [Rh,(NCMe),(p-02CMe)J2+ are weakened by the trans effect of the Rh-Rhbond, and are substitutionally labile whereas the equatorialligands are fairly inert.Somewhat surprisingly, then, thereactivity of 3 is limited. Substitution with neutral ligandssuch as bipy does not occur, either at room temperature orthermally, and reaction was readily observed only withNa[S2CNMe,]-2H,O in acetonitrile, giving [Rh,(NCMe)-(S,CNMe,)(bipy)(p-RNNNR),][PF,I 4 (Tables 1 and 2) as abrown powder in good yield. The 'H NMR spectrum of 4 isconsistent with the asymmetric structure shown in Scheme 1and is similar to that proposed ' for [Rh,(CO)(S,CNMe,)-(bipy)(p-RNNNR),] [PF,] rather than to that determined for3. The methyl resonances for the tolyl groups of the triazenidebridges occur as a complex multiplet centred at 6 2.26 and thepyridyl rings of the bipy ligand are also inequivalent. Inaddition, the signals for the methyl groups of the dithio-carbamate ligand occur as two singlets at 6 2.77 and 3.02suggesting S,CNMe, is bound to Rh(2) at one axial and oneequatorial site.Although complex 3 proved to be relatively inert, thehalide-abstraction reaction of [(Rh,(p-I)(CO)(bipy)(p-RNNNR),),l2+ 1 in CH,Cl, provided a more reactiveprecursor to a wide range of novel dirhodium complexes.Thus,the reaction with AgPF, gave a deep green solution which, afterfiltration to remove precipitated AgI, showed one carbonylband in the IR spectrum [v(CO) 2087 cm-'1; the similarity inenergy of this band to that of 2 suggests the presence ofa weakly solvated species e.g. [R h, (CO)( solv) , (bipy)( p-RN"R),][PF,], A (solv = CH,Cl,). During the reactionIR spectroscopy showed the initial formation of an inter-mediate with one carbonyl band at 2046 cm '; though notisolable, it is most likely the monoiodide cation [Rh,I(CO)-Complex A (solv = CH,Cl,) may be used in situ in CH,Cl,.Alternatively, removal of the solvent from the reaction mixtureand treatment of the residue with tetrahydrofuran (thf) ormethanol gave species which react in the same way, presumablyA (solv = thf or MeOH). These solvated species could not beisolated though they are moderately stable in solution undernitrogen. However, treatment of the residue with MeCN,followed by precipitation with diethyl ether, provides thebest synthetic route to pure [Rh,(CO)(NCMe),(bipy)(p-RN"R),][PF,], 2 (see above).All of the complexes A(solv = CH,Cl,, thf or MeOH) act as precursors to isolable,[Rh2l4+-containing species. Although the CH,Cl, solvent0(solv)(biPY)(~-RN"R)2lCPF,I2030 J. CHEM. SOC. DALTON TRANS. 1994complex has been most routinely used, the use of methanol andthf can provi.de advantages in the synthesis of neutral products(see below).The addition of an equimolar quantity of a neutral bidentateN-donor ligand [L-L = bipy, 4,4'-dimethyl-2,2'-bipyridyl(dmbipy), phen, or di-2-pyridylamine (dpa)] to A (solv =CH,Cl,) in CH,Cl,, and storage of the mixture at 0°Covernight, gave in each case a green microcrystalline precipitatewhich could be purified from acetonitrilediethy1 ether to givethe product in 50-75% yield.Though elemental analysis (C, Hand N) was consistent with the formula [Rh,(CO)(L-L)(bipy)-(p-RNNNR)2][PF6]2, i.e. with a face-to-face structure relatedto that of [Rh,(CO)(S,CNMe,)(bipy)(p-RNNNR),][PF,] 'and 4 above, IR, 'H and 13C NMR spectroscopy (Tables 1and 2) revealed the formation of the novel carbonyl-bridgedcompounds [Rh,(p-CO)(L-L)(bipy)(p-RNNNR),][PF,], 5(L-L = bipy 5, dmbipy 6, phen 7 or dpa 8) with the structureshown in Scheme 1. Each complex shows one IR carbonyl bandin the range 1770-1780 cm-' and the 'H NMR spectrum of 5shows only one signal for the methyl groups of the twotriazenide ligands, two doublets (6 7.09 and 7.21) for the ortho-and rneta-protons of the c6 rings, and three signals for the bipyligands in the ratio 1 : 2 : 1.The 400 MHz ' 3C NMR spectrumshows a triplet at 6 186 for the bridging carbonyl carbon atom[J('3C'03Rh) 48 Hz], one signal for the four methyl groups ofthe triazenide ligands and two equivalent pyridyl rings. Foreach of the compounds 6-8 the 'H NMR spectrum shows twosignals for the RNNNR methyl groups. As the two halves of thebipyridyl ligand are equivalent the ligands L-L must chelateone rhodium atom, binding in trans positions to the twonitrogen atoms of the cis-bridging triazenide ligands. As with 5,each complex exhibits a triplet signal in the 13C NMRspectrum at 6 ca. 180, with a coupling to rhodium of ca. 50 Hz,corresponding to the bridging carbonyl ligand.The reaction of 1 equivalent of dppe with complex A (solv =CH,Cl,) in CH,Cl, is similar to those with the N-N ligandsdescribed above, resulting in an intense green solution fromwhich a green solid was isolated after filtration, reduction ofthe solvent volume, and addition of diethyl ether or hexaneas precipitant; recrystallisation from CH,Cl,diethyl ethergave microcrystals of [Rh,(p-CO)(dppe)(bipy)(p-RNNNR),]-[PF,], 9 (Tables 1 and 2). The IR spectrum is similar to thoseof complexes 5 8 with one absorption in the bridging carbonylregion at 1760 cm ' .Similarly, the 'H NMR spectrum showstwo resonances for the four p-tolyl methyl groups, and equiv-alent pyridyl groups for the bipy ligand. The 13C NMR spec-trum shows two resonances, at 6 21.4 and 21.6, for the methylgroups of the triazenide bridges, and two signals for the 0- andrn-carbons of the C,H, groups, also indicating inequivalentends to the two triazenide bridges.The 31P NMR spectrumshowed a doublet at 6 58.0 [J(31P'03Rh) 127 Hz], indicatingequivalent phosphorus atoms, again in accord with thecarbonyl-bridged structure in Scheme 1. However, the ' 3Csignal for the bridging carbonyl carbon atom was not observed.The reaction between complex A (solv = CH,Cl,) andPh,PCH,PPh, (dppm) is again similar to that with bipy, witha green solid isolated in good yield. Once again the elementalanalysis was consistent with the formula [Rh,(CO)(dppm)-(bipy)(p-RNNNR),][PF,], 10 and the Nujol-mull IR spec-trum showed a bridging carbonyl absorption at 1756 cm-'.However, in CH,Cl,, the IR spectrum unexpectedly showedtwo bands (2070m and 1758s cm-') indicating the presence insolution of a second isomer 10b with a terminal carbonyl ligand,in addition to [Rh,(p-CO)(dppm)(bipy)(p-RNNNR)2][PF6]210a the analogue of 9.Neither the 'H nor 13C NMR spectrumof 10 provided evidence for the nature of the second species. Thesignals for the triazenide C,H, and dppm phenyl protons are,however, broader than those observed for 9, suggestinginterconversion between the major, carbonyl-bridged isomer10a and the minor terminal form lob. The ' 3C NMR spectrumalso shows no evidence for the terminally bound carbonylspecies 10b although a doublet of triplets was observed for thecarbonyl group of 10a at 6 187.5 [J(Clo3Rh) 124, J(C3'P) 71.By contrast, 'P NMR spectroscopy provided good evidenceboth for the terminal isomer 10b and for its equilibration with10a.The room-temperature 31P NMR spectrum of complex 10 in(CD,),CO (50%) showed only one broad signal (6 -25.5)(apart from the well resolved heptet of the [PF,]- anion)suggesting, by comparison with the well defined spectrum of 9,the occurrence of a rapid fluxional process.At - 80 "C thespectrum is well resolved, showing not only a doublet [S - 23.5,J(31P'03Rh) 110.7 Hz] which can be assigned to the twoequivalent phosphorus atoms of the carbonyl-bridged isomer10a, but also a doublet [S - 11.5, J(31P103Rh) 92.7 Hz] and adoublet of doublets [S -90.4, J(31P'03Rh) 58.3 and 64.3 Hz]due to the second, minor component lob.The latter resonancesmay be assigned to an equatorial phosphorus atom (coupled toone Rh atom), and an axial phosphorus atom (coupled to bothRh atoms, the second coupling via the trans M-M bond)respectively, as in the structure shown in Scheme 1.Although the spectroscopic data show the presence of twospecies in solution, an X-ray crystallographic study on 10revealed only the unusual carbonyl-bridged isomer 10a in thesolid state (as implied by the Nujol-mull IR spectrum). Crystalsof the dichloromethane solvate of 10a were grown by the slowdiffusion of hexane into a CH,Cl, solution. The structure isshown in Fig. 2 and important molecular bond lengths andangles are listed in Table 4.The structural study of 10a-2CH2C1,confirms the presence of a bridging carbonyl in the dication, andis in agreement with the molecular structure suggested by thespectroscopic results. The Rh - Rh distance of 3.179(2) A isvery long in comparison with other dirhodium(I1) triazenide-bridged complexes [cf. 2.534(2) for 3 and 2.544(1) for 13suggesting little or no direct interaction between the two metalatoms. The angle of 108.3(11)" for Rh(l)-C(l)-Rh(2) is muchgreater than is common for Rh,(p-CO) species, for which themean value is 84.5°.5 The local geometry at each rhodium atommay be considered as square pyramidal with the Rh-C(l)interaction at the apex of the pyramid. Geometries such as thisare well known for rhodium(I1r) acyl complexes such as[RhCl(C(O)Me)(PMe,Ph),][PF,].For this species the valuesof v(C0) (1 720 cm-') and the Rh-C-Me angle [ 1 12.2(4)'] arecomparable with v(C0) (1758 cm-') and the Rh-C-Rh angle[108.3( 1 l)"] found for 10a. The inference to be drawn is that thep-CO ligand in 10a may be usefully viewed as a metallatedformyl ligand, or more simply as a ketonic (C02-) carbonyl.Fig. 2 The molecular structure of the dication of complex 10a showingthe labelling scheme. Other details as in Fig. J. CHEM. SOC. DALTON TRANS. 1994 203 1Table 4 Selected bond lengths (A) and angles (") for complex 10a*2CH2C12Rh(2)-Rh( 1 )-N(3)N(3)-Rh( 1)-N(6)N(3l-W 1 W ( 7 )Rh(2)-Rh( I)-N(8)N(6)-Rh( 1 )-N(8)Rh(2)-Rh( I)-C(l)N( 6)-R h( 1 )-C( 1 )N(8)-Rh( 1)-C( 1)Rh( 1)-Rh(2)-P(2)Rh( 1 )-Rh( 2)-N( 1 )P(2)-Rh(2)-N( 1)P(l)-Rh(2)-N(4)N(1 )-Rh(2)-N(4)3.179(2)2.086( 15)2.303(6)2.1 lO(15)1.791 (1 8)1.854(20)1.508(24)1.467(25)1.496(22)1.479(23)1.540(44)79.6(4)88.1(6)168.6(6)118.3(4)1 69.3( 5 )3 5.2(6)102.8(7)86.8(8)119.4(1)72.4(4)166.6(4)169.9(5)90.4(6)1.433(22)1.262(21)1.423(24)1.248(23)2.01 9( 14)2.054( 15)2.327(6)1.929(20)1.797(20)1.805(23)1.483(23)86.5( 7)1 OO.O(S)93.3(6)124.0(6)119.1(7)131.1(11)128.1 (1 3)125.9( 14)134.6( 12)125.7( 13)113.7(14)108.3(11)129.3(17)1.478(29)1.556(24)1.540(25)1.192(26)1.29 1 ( 1 9)1.460(26)1.353(30)1.33 l(29)2.075(15)1.992(22)2.150( 15)72.2(4)11 1.8(5)95.4( 6)95.2( 6)79.4(6)9747)92.2(7)112.6(2)73.4(2)96.6(4)76.5(4)98.6( 5 )36.5(7)P(2)-Rh( 2)-C( 1 )N(4)-Rh(2)-C( 1)Rh(2 jP(2)-C(2)Rh(2)-P(2)-C(2 1)R h(2)-N( 1 )-C(27)Rh( 1)-N(3)-C(34)Rh(2)-P(l)-C(3)Rh(2)-N(4)<(4 1 )Rh( 1)-N(7)<(59)Rh( 1 )-N(6)-C(48)Rh( 1)-N(8)-C(64)Rh(l kC(1 to1.833(19)1.828(20)1.453(32)1.465(26)1.473(22)1.714(36)1.296(24)1.456(26)1.275(23)1.372(27)88.4(7)99.6(7)116.1(7)92.7(6)123.9(7)112.4(12)I .571(22)118.0(10)120.1(11)110.3(12)112.2(14)123.3( 1 2)122.2( 14)A corollary is that the rhodium atoms of 10a are formallyRh"'.In order to assess these suggestions, and to probe the bondingin these species, extended-Huckel molecular-orbital (EHMO)calculations were carried out on simple models of complex 10as both the carbonyl-bridged 10a and unbridged 10b isomers(i.e.on [Rh,H,(CO)5] in which hydride ligands replace thetriazenide ligands, and CO replaces the others, of lo}. Idealisedgeometries were employed [all bond angles at rhodium = 90 or1.808, C-0 1.152 A]; Huckel parameters were taken from theliterature. * The calculated total energies for the two isomersof [Rh2H4(C0)5] are similar [within 1 eV ( ~ 9 6 kJ mol-')Iwithout geometry optimisation. Given the crudeness of themodel this is in reasonable accord with the experimentalevidence above. The R h - . - R h overlap population for thebridged isomer with Rho.= Rh distance 3.20 A is slightlynegative (-0.051) indicating no direct Rh Rh bonding (cf0.129 for the non-bridged isomer at the same Rh Rhdistance).The general form of the major interactions betweenthe Rh, unit and the p-CO ligand is indicated in Fig. 3(a).The occupancy of both o and CF* Rh - Rh orbitals arises inthe bridged isomer because of the stabilisation of the latterorbitals by interaction with the in-plane CO 7c* orbital.As a consequence the Rh-Rh bond order is formally zeroin the carbonyl-bridged isomer (and unity in the non-carbonyl-bridged isomer, cf. [Rh,(p-O,CR),L,] adducts 9}.The lowest unoccupied molecular orbitals (LUMOs) are Rh(p-CO) antibonding in character which is in agreement with theobserved Rh-p-CO bond cleavage on reduction of 10 to 11 (seebelow). In accord with the suggestion that the p-CO has ketoniccharacter we calculate a build-up of negative charge on theoxygen of this group (-0.98 e, cf.-0.76 e for terminalcarbonyls in the model for 10a). It is notable that in the crystalstructure of lOa~2CH2Cl2 the shortest intermolecular contactinvolving 0 is a C-H--.O hydrogen bond to an acidichydrogen of the ordered dichloromethane [0 9 - H(65b) 2.46A, 0 H(65b)-C(65) 173, C(l)-O - H(65b) 167"], consist-ent with significant negative charge at 0. The calculationson the unbridged isomer of [Rh,H,(CO),] analogous to lobshowed that the addition of one axial ligand brings aboutsubstantial charge redistribution such that the rhodium withthe axial CO ligand carries the higher fractional charge ( + 1.29,1 80°, Rh-C-0 180", Rh-H 1.60, Rh-Rh 3.20-2.50, Rh--C(O)cf.+ 0.28 for the other rhodium and + 0.97 e for each rhodiumin the bridged isomer). The implication is that the [Rh2I4+ unitmay be usefully viewed as consisting of a square-planarrhodium(1) centre interacting with a square-pyramidal rhodium-(111) centre via a donor-acceptor metal-metal bond [see Fig.3(b)]. In this bond the hybrid orbital arising from interaction ofthe axial CO lone pair and rhodium pz and dZ2 [labelled hybridin Fig. 3(b)] is the acceptor orbital and lies at high energyrelative to the donor d,z on the other rhodium atom. As aconsequence the pair of electrons in the metal-metal o-bondorbital is more localised on the rhodium without the axialcarbonyl and the charge disparity noted above results.The electrochemistry of complexes 9 and 10 appears decep-tively simple.In CH,Cl, the cyclic voltammogram of eachcomplex shows one oxidation wave (1.51 and 1.44 V respec-tively) and two reduction waves (-0.20 and - 0.53, and 0.04and- 0.56 V respectively) all of which appear to be fully reversible.However, the chemical reduction is far from straightforward.On addition of 1 equivalent of NaBH, to 9 in thf a goodyield was obtained of the paramagnetic, [Rh,], +-containingcomplex [Rh,(CO)(dppe-P)(bipy)(p-RNNNR),][PF,] 11,characterised by elemental analysis (Table 1) and by the closesimilarity of its spectroscopic and voltammetric properties tothose of [Rh2(CO)(PPh3)(bipy)(p-RNNNR),] [PF,]. Thus, itshows one IR carbonyl band at 2016 cm-', an anisotropic ESRspectrum at 77 K (in a 2: I thf: CH,Cl, glass) with g, = 2.254,g, = 2.223 and g , = 2.014 and hyperfine coupling to the twoinequivalent rhodium atoms [ A , = 27.1 and 8.0 G (8 x lo4T)], and a cyclic voltammogram with a reversible oxidationwave at 0.85 V and a reversible reduction wave at -0.51 V.Thus, when 9 undergoes one-electron reduction the bridgingcarbonyl reverts to a terminal position.Moreover, the dppeligand becomes monodentate since the face-to-face structuredoes not favour axial site co-ordination in the [Rh,13+ state.On treatment of complex 9 with 2 equivalents of [Co(cp),](cp = q5-C,H5) an air-sensitive green powder can be isolatedwhich shows one carbonyl band at 1949 cm-' and which reactswith air or [Fe(cp),]+ to form 11. Though the green speciescould not be further characterised it is most likely the neutral[Rh2I2+ complex [Rh,(CO)(dppe-P)(bipy)(p-RNNNR),].Though the formation of 11 from 9 would seem to involvea straightforward one-electron process the relationshipbetween the cyclic voltammograms of the two species is no2032 J.CHEM. SOC. DALTON TRANS. 1994tRh2Ld4+ coFig. 3 Schematic diagrams: (a) the metal-(p-CO) interactions inan open-book [Rh,14+ unit with a bridging CO ligand, based onEHMO calculations on [Rh2H4(C0)4(p-,C0)]; (b) the metal-metalinteractions in a face-to-face [Rh,14+ unit with an axial CO ligand,based on EHMO calculations on [Rh,H4(CO)5]clear; the first reduction of 9 occurs at -0.20 V whereas theoxidation wave for 11 is at 0.85 V. Moreover, we have shownthat the addition of a catalytic amount of reductant to 9 causesisomerisation to a second [Rh,14+ complex in which the twotriazenide ligands are cis bound to one rhodium atom andtrans bound to the second." A more detailed study of theelectrochemistry of 9 and the other carbonyl-bridged dirhodiumcomplexes described above will be reported elsewhere.During studies of the synthesis of complexes 5 1 0 from A(solv = CH,Cl,) variable but small quantities of a secondcomplex could occasionally be isolated.For example, afterremoving 6 from the reaction mixture formed from A (solv =CH,Cl,) and dmbipy, addition of hexane to the mother-liquorsgave a green-brown powder 12 in 11% yield. Better yields (40-50%) could be obtained by allowing 1 and AgPF, to reacttogether in CH,Cl, for prolonged periods but the product wasusually contaminated by small amounts of other species whichwere difficult to separate from 12.The IR spectrum of 12 showedone terminal carbonyl band at 2062 cm-' in CH,Cl, but thecomplex could not be further characterised spectroscopically.Crystals of 12 were therefore grown, from hexane-CH,Cl,, andthe structure of its solvate determined by X-ray crystallography.The best refined model for the solvent incorporated a total ofseven carbon atoms per Rh, unit and the formula quotedreflects this. However, hexane seems the more likely solvent ofcry stallisation.The X-ray diffraction study showed complex 12 to be neutraland tetranuclear, i.e. [{Rh2(CO)(0,PF,)(p-02PF2)(bipy)(pRNNNR),},]; its molecular structure is shown in Figs.4 and 5and selected bond lengths and angles are listed in Table 5. Thecomplex consists of two Rh, (CO)(O,PF,)( bipy)(pRN"R),fragments linked by two bridging 02PF2 ligands, with theentire dimer having exact crystallographic C, symmetry. Eachbridging O,PF, ligand occupies an axial site, trans to theRh-Rh vector, on one dirhodium moiety and an equatorial site,trans to a triazenido nitrogen atom, on the other. The remainingequatorial site on this rhodium [Rh(2)] is occupied by aterminal carbonyl ligand. The other rhodium atom [Rh(l)]carries a terminal 02PF, ligand in the axial site with the bipyligand occupying the equatorial sites trans to the triazenidonitrogen atoms.The Rh(lkRh(2) distance [2.505(4) A] lies atthe high end of the usual range' for Rh"-Rh" single bonds inRh,L! species where the six-co-ordinate rhodium atoms carryaxial ligands. The formation of the { [Rh2I4'}, dimer by ligandbridging across axial and equatorial sites in different { [Rh,14+}moieties is reminiscent of a similar structure in 1 in which iodiderather than O,PF, is the bridging ligand. In this case thecarbonyl ligands are cisoid and lie on the same side of theRh,(p-02PF,), ring. In contrast, in 1 the carbonyl ligands aretransoid, lying on the opposite sides of the Rh,(p-I), ring.Other notable features of the structure of 12 include thevariation in Rh-O(POF,) distances, with those in axial sitesbeing substantially longer [Rh( 1 )-O( I) 2.23(2), Rh(2)-O(2)2.382(14), us.Rh(2)-O(3) 2.11(2) A], cf. similar behaviour in3 above. The O,PF, ligands show considerable flexibility inthe P-0-Rh bond angles with the terminal ligand at Rh(1)having a value intermediate between those for the bridgingligand [P( 1)-O(1)-Rh(1) 145.2(1 I), P(2)-0(2)-Rh(2)165.4(1 l), P(2a)-0(3)-Rh(2) 130.8(10)"]. The monoanionicO2PF, ligands presumably arise by partial hydrolysis ' ofThe reactions of anionic ligands with complexes A giveproducts rather different from those formed with the neutralligands described above. Complexes of chelating anionicN-S ligands can be prepared either using the thiols l-methyl-2-sulfanylimidazole (Hmsim), 2-sulfanyl-pyrimidine (Hspym),-thiazoline (Hstz) or -benzimidazole (Hsbzim) directly or thecorresponding sodium thiolates (prepared from the thiol andNaH in thf).Thus, addition of an equimolar quantity of theappropriate ligand to A (solv = CH,Cl,), or of the sodium saltof the ligand to A (solv = thf), gave green solutions from whichthe green salts [Rh, (CO)(N-S)(bipy)( p-RNNNR),] [PF,](N-S = msim 13, spym 14, stz 15 or sbzim 16) were readilyisolated and characterised by elemental analysis and by 'H, I3CNMR and IR spectroscopy (Tables 1 and 2). The complexes 13-16 differ from 5-9 and 10a in showing one carbonyl absorptionband in the IR spectrum at ca. 2065 cm-', indicative of aterminal CO ligand. The 13C NMR spectrum provides furtherevidence for such a CO ligand, with a doublet at 6 ca. 185[J('3C'03Rh) ca.59-60 Hz], showing coupling to only onerhodium atom. The 'H and 13C NMR spectra are otherwisecomplicated, showing all of the bipyridyl protons and carbonsand all of the methyl groups of the bridging triazenides to beinequivalent and therefore that the complexes are highlyasymmetric.The spectroscopic data are consistent with the structureshown in Scheme 1. In the absence of structural data (none ofthe complexes could be crystallised despite repeated attempts)it is not known if the N-S ligands are mono- or bi-dentatethough the loss of the sulfur proton on co-ordination suggeststhe latter is more likely, with the metal chelated by the sulfurand nitrogen atoms. The inequivalence of the two halves of thebipyridyl ligand suggests that the N-S ligands occupy axial andCPF,I-J.CHEM. SOC. DALTON TRANS. 1994 P 2033Fig. 4 Molecular structure of the dimer 12 showing the labelling scheme. Other details as in Fig. 1Fig. 5 Molecular structure of one half of complex 12 showing thelabelling scheme. Dashed lines indicate bonds to Rh(2a) in the secondhalf of the molecule. Other details as in Fig. 1equatorial positions on one of the rhodium atoms although,again, it is not known which of the two donor atoms takes upwhich of the two positions. The proposed structure, containingan axial ligand, is similar to those of other known [Rh2I4+species. The preference for this structure over the p-CO formfound for 5-9 and 10a may be tentatively attributed to theanionic nature of the chelating ligand in these species. It ispossible that the anionic ligand better stabilises the higherformal charge separation in the unbridged isomer noted in theEHMO calculations described above.Each of the cyclic voltammograms of complexes 1S16 inCH,Cl, shows one diffusion-controlled oxidation wave at ca.1.2 V; the waves for 14 and 16 are fully reversible and those for13 and 15 become reversible at scan rates greater than 500 mVs-'.The rather positive values for E", and the irreversible natureof the waves for 13 and 15 at slow scan rates, suggest thatunstable products are formed on oxidation. Each of the cyclicvoltammograms of 13-16 also shows two reduction waves at ca.-0.36 and - 1.13 V respectively. For compounds 13-15 thewaves are ill defined, only becoming reversible at scan ratesgreater than 500 mV s-'.Complex 16 shows one irreversiblereduction wave at -0.35 V, with an associated product waveat -0.22 V. A further product reduction wave is observedat - 1.05 V which becomes reversible only at scan ratesgreater than 500 mV s-'. Again, further chemical studies ofthese oxidation and reduction processes will be reportedlater.Complex A also reacts with salts of simple monoanions togive products with terminal carbonyl ligands. The addition ofan excess of NaCl to A (solv = MeOH) gave, after evaporationof the reaction mixture to dryness and extraction into CH,Cl,,high yields of [Rh,(CO)Cl,(bipy)(p-RNNNR),] 17 as green,air-stable microcrystals. The neutral complex was characterisedby elemental analysis (Table l), by IR and NMR spectroscopy(Table 2), and by the mass spectrum which showed a parent ionat m/z 910.The diiodide analogue of 17, namely [Rh,(CO)I,-(bipy)(p-RNNNR),] 18, has been prepared directly from [Rh,-(CO),(bipy)(p-RNNNR),] and iodine but is considerably lessstable in the solid state. Moreover, the electrochemistry of 17 isfar better defined than that of 18.The cyclic voltammogram of complex 17, from 0.0 to 1.3 V,shows a fully reversible, diffusion-controlled oxidation wavecentred at 1.08 V, corresponding to the formation of the[Rh,] +-containing monocation [Rh,(CO)Cl,(bipy)(p-RNN-NR),]+. On scanning from 0.0 to - 1.3 V [Fig. 6(a)] thevoltammogram shows an irreversible reduction wave at ca.-0.67 V followed by a second, fully reversible, product wavecentred at - 1.12 V.The close similarity in potential of theproduct wave to that for the one-electron reduction of [Rh,(CO)-I(bipy)(p-RNNNR),]' to [Rh,(CO)I(bipy)(p-RNNNR),]( E O = - 1.07 V)' strongly suggests that one-electron reductionof [Rh,(CO)Cl,(bipy>(p-RNNNR),] to [Rh,(CO)CI,(bipy)(p-RN"R),]- (at ca. -0.67 V) is followed by rapid loss ofchloride ion to give [Rh,(CO)Cl(bipy)(p-RNNNR),] {which isreversibly reduced to [Rh,(CO)Cl(bipy)(p-RN"R),]-} . Fur-ther evidence for such a process is shown by scanning from 0.0 to1.3 to - 1.3 to 0.0 V [Fig. 6(h)]. A second product wave at ca.0.22 V appears only after scanning through the wave at -0.67V and corresponds to the oxidation of [Rh,(CO)Cl(bipy)-(p-RNNNR),] to [Rh,(CO)Cl(bipy)(p-RNNNR),] + {cf2034 J.CHEM. SOC. DALTON TRANS. 1994Table 5 Selected bond lengths (A) and angles (") for complex 12-2.3C6H,,174.9(8)85.6(8)96.1(8)85.1(7)98.7( 7)96.3( 5)85.3(5)175.5(4)1 76.2( 9)95.0(9)83.7(7)103.1(7)1.36(2)1.34(2)2 .o 1 (2)2.23(2)2.00(2)2.38(1)1.52(2)1.46(2)81.9(6)81.8(6)92.6(4)145.2(11)130.8(10)123(2)128(2)124(2)129(2)1 16(2)1 16(2)99.3(8)Symmetry transformation used to generate equivalent atoms: a - x + 2, y , - z + i.1.46(2)1.30(2)1.37(2)1.29(3)2.06(2)2.505(4)2.04( 2)1.44(3)79.0(8)178.0(8)95.6(7)80.2(6)82.7(6)95.8(5)9 1 .O( 1 0)90.0(7)172.0(7)93.3(8)90.1(6)C( 1)-Rh(2)-Rh( 1)0(2)-Rh(2)-Rh( 1)N(4)-R h( 2)-R h( 1 )P(2)-0(2)-Rh(2)N(2)-N(3kRh( 1)N(5FN(4tRh(2)N(5)-N(6)-Rh( 1)C(39)-N(7)-Rh(l)C(30)-N( 8)-Rh( 1 )0(5)-C( 1 FRh(2)N(2)-N( 1)-Rh(2)1.42(2)1.55(2)1.49(2)1.18(3)1.35(2)1.41(3)1.29(3)1.37(3)93.5(7)83.0(5)1 7 1 .6(4)165.4( 1 1)123(2)123(2)119.7(14)126(2)126(2)178(2)122(2)0.0 -0.67 -1.12 -1.31 1 I 1 I I1.3 1.08 0.22 -0.67 -1.12 -1.3E / VFig.6and (b) from 0.0 to 1.3 to - 1.3 to 0.0 VCyclic voltammogram of complex 17 (a) from 0.0 to - 1.3 Vthe oxidation of [Rh2(C0)I(bipy)(p-RNNNR),] to [Rh2-(CO)I(bipy)(p-RNNNR),]+ (E" = 0.21 V)}.The reaction between complex A (solv = MeOH) andNaNO, gave [Rh2(C0)(NO2),(bipy)(p-RNNNR),] 19 as abrown precipitate (Tables 1 and 2). The cyclic voltammogramof 19 is qualitatively similar to that of 17, with an ill defined,irreversible reduction peak at ca.-0.74 V accompanied byproduct waves at ca. - 1 .O (reversible) and 0.32 V, probably dueto the formation of [Rh,(CO)(NO,),(bipy)(p-RNNNR),]~and the subsequent loss of nitrite ion to give [Rh,(CO)(NO,)-(biPY)(P-R"NR),I *ConclusionThe halide-abstraction reactions of [(Rh,(p-I)(CO)(bipy)(p-RN"R),},][PF,], in CH,Cl, or MeCN give the labilesolvates [Rh2(CO)(solv),(bipy)(p-RNNNR),12 +- , versatile pre-cursors to a wide range of complexes containing the [Rh2I4+core. Of particular interest are the open-book, carbonyl-bridged complexes [Rh2(p-CO)(L-L)(bipy)(p-RN"R),]-[PF,], which, for L-L = dppm, is in equilibrium in solutionwith the face-to-face, terminal carbonyl isomer [Rh,(CO)-(dPPm)(biPY)(p-R"NR),1 CPF612 *ExperimentalThe preparation, purification and reactions of the complexesdescribed were carried out under an atmosphere of dry nitrogen,using dried, distilled and deoxygenated solvents.Unlessotherwise stated, products were (i) purified by dissolution inCH2C1,, filtration, addition of hexane, and partial evaporationin vacuu to induce precipitation, and are (ii) air-stable solids,dissolving in polar solvents such as CH,Cl, to give moderatelyair-sensitive solutions. The complexes [{Rh,(p-I)(CO)(bipy)(p-18 were prepared by published methods.' The salt AgPF,was obtained from Fluorochem Ltd. and 2,2'-bipyridyl,4,4'-dimethyl-2,2'-bipyridyl, 1 , 10-phenanthroline, 2-sulfanyl-pyrimidine, 2-sulfanylbenzimidazole, 1 -methyl-2-sulfanyl-imidazole, and 2-sulfanylthiazoline were obtained from AldrichChemical Co.The IR spectra were recorded on Nicolet MX5 or 5ZDX FTspectrometers, X-band ESR spectra on a Bruker ESP 300Einstrument and calibrated against a solid sample of thediphenylpicrylhydrazyl (dpph) radical, H and ' 3C NMRspectra on JEOL GX270 or GX400 spectrometers and cali-brated against SiMe, as an internal reference, 31P NMR spectraon a JEOL FX90Q instrument using 85% H3PO4 as anexternal reference and FAB mass spectra at the SERC MassSpectrometry Service Centre at the University College ofSwansea.Electrochemical studies were carried out using anEG&G model 273 potentiostat in conjunction with a three-RN"R)2}21[PF612 and CRh2(Co)12(bipy)(~-RNN")2J.CHEM. SOC. DALTON TRANS. 1994 2035Table 6 Structure analysesFormulaA4Crystal systemSpace group (no.) 4b/AC I Aa/"Pi"Y I"u/A3ZD,/gp( M o-Ka)/mm-'F(000)Crystal size/mm20 rangerScan width, a/'Scan methodTotal dataUnique data'Observed' dataCF' > 2o(f'?1, NoLeast-squaresvariables, N ,R"R'"S"Weights"Largest finaldifference mapfeatures e k331223.6Triclinic10.267(3)1 4.009( 6)18.687(6)95.3 l(4)95.25(3)104.3 l(4)2567(2)21.570.7812280.05 x 0.32 x 0.54-451.5Wyckoff, o7227673742424200.0570.05 11.510.0003 (g)C44H45F12N1 lPZRh2p21lC (14)+0.58, -0.5510a-2CH 'C1,1680.8Monoclinic15.013(5)18.406(6)27.991(8)90103.85(5)907510(4)41.490.8135120.15 x 0.25 x 0.74-450.6Wyckoff, o12 0551 1 6364677C66H60C14F1 2N80P4Rh2n l l n (14)5670.0930.0831.880.0005 ( g )+0.82, -0.7812*2.3C6H2249.2MonoclinicC2/c (1 5)22.820( 17)17.162( 13)27.148(25)90110.92(6)90993 1 (1 4)41.530.8046601.0 x 0.5 x 0.753 4 00.7Wyckoff, o10 63446302306C9ZH 104F8N1 6O 1 0P4Rh431 10.109 (Rl)b0.188 ( w R ~ ) ~1.35O.OS(u), 15(b)+0.85, -0.61R = ~ l A l / ~ l F , I ; R' = (hA'/ZWF,')'; S = CCwA'/(N, - N,)lf; A = F, - F,; w = [o,'(F,) + gF:]-', o,'(F,) = variance in F, dueto counting statistics.Residuals calculated for reflections with P > 20(Fz); wR2 = ~wA2/XwFO4]*; S = [X;A'/(N - N,)]'; R1 = XI F, -F C ~ / ~ ~ ~ , l ~ A = F,' - F,'; N = No + restraints; w = [ocz(FoZ) + (UP)' + bP]-', o,'(F,') = variance in F, due to counting statistics,P = [max(F,',O) + 2FC2]/3.electrode cell.For cyclic voltammetry the auxiliary electrodewas a platinum wire and the working electrode a platinum disc.The reference was an aqueous saturated calomel electrode(SCE) separated from the test solution by a fine-porosity fritand an agar bridge saturated with KCl. Solutions were0. I x 10 mol dm-3 in the test compound and 0.1 mol dm-3 in[NBu,][PF,] as the supporting electrolyte. Under theseconditions the E" values for the couples [Fe(q-C,H,),]+-0.47 and - 0.09 V respectively. Microanalyses were carried outby the staff of the microanalytical service of the School ofChemistry, University of Bristol.LFe(77-C 5 H 5 )21 and LFe(77-C 5 Me51 21 +-[Fe(77 -c ,Me 5 ) 21 areBis(acetonitrile)(2,2'-bipyridyl)carbonylbis(p-di-p-tol~,ltri-azenido-N N3 )dirhodium Bis(hexaJEuorophosphate) , [R h2 (C0)-(NCMe),(bipy)(p-RNNNR)2][PF6]2 2 (R = p-tolyl).-Toa stirred solution of [(Rh2(p-I)(C0)(bipy)(p-RNNNR),),I-[PF,], (0.11 g, 0.05 mmol) in CH2Cl, (40 cm3) was addedAgPF, (0.026 g, 0.1 mmol).After 10 min the green solution wasfiltered through Celite to remove the precipitate of AgI.Acetonitrile (0.5 cm3) was then added to the filtrate to give anorange solution which was treated with hexane (15 cm3). Thesolvent was then reduced in volume in uacuo, giving an oilwhich solidified to an orange solid on stirring.Purification fromCH2C1,-hexane gave a green powder, yield 0.075 g (60%).Tris( acetonitrile)(2,2'-bipyridyl)bis(p-di-p-tolyltriazenido-N'N3)dirhodium Bis(hexajluorophosphate), [Rh,(NCMe),-(~~PY)(~-RNNNR)~][PF,]~ 3.-To a stirred solution of~(Rh2(~-r)(Co)(bi~~)(~-RNNNR)2}2~~pF6~2 (O*I5 g, O o o 7mmol) in acetonitrile (30 cm3) was added AgPF, (0.033 g, 0.13mmol). After 30 min the orange solution was filtered throughCelite and then heated under reflux for 12 h. The orangesolution was then filtered through Celite and the solvent wasevaporated to low volume (ca. 5 cm3) in uacuo. Addition ofdiethyl ether precipitated a green powder which was purifiedfrom acetonitrileediethyl ether, yield 0.135 g (82%).Ace ton it rile( 2,2 ' - bipy r idy 1 )(die thy ldit hiocarbama to) bis( p-di-p- t oly ltriuzenido-N N3)dirhodium HexaJEuorophospha te, [R h -(NCMe)(S,CNMe,)(bipy)(p-RNNNR),I[PF,] 4.-To astirred solution of [Rh,(NCMe) 3( bipy)(p-RNNNR) 2] [PF,](0.1 g, 0.082 mmol) in acetonitrile (30 cm3) was addedNa[S2CNMe,]-2H20 (0.014 g, 0.087 mmol).After 1 h the darkbrown solution was filtered through Celite and the solventevaporated to give a brown oil. Purification afforded theproduct as a brown powder, yield 0.071 g (77%).Bis(2,2'-bipyridyl)(p-carbonyl)bis(p-di-p-tolyltriazenido-N N3)dirhodium Bzs(hexaJEuorophosphu te), [ R h 2( p-CO)( bipy),-(p-RNNNR)2][PF6]2 5.-To a stirred solution of [{Rh2(y-I)(CO)(bipy)(p-RNNNR)2}2][PF6]2 (0.15 g, 0.07 mmol) inCH2C12 (25 cm3) was added AgPF, (0.034 g, 0.14 mmol).After10 min the dark green solution was filtered through Celite toremove AgI. 2,2'-Bipyridyl (0.024 g, 0.15 mmol) was thenadded and the mixture stored at 0 "C for 12 h. The dark greenmicrocrystalline precipitate was purified from acetonitrile-diethyl ether, yield 0.095 g (53%). The complexes [Rh2(p-CO)(L-L)(bipy)(p-RNNNR)2][PF6]2 (L-L = dmbipy 6, phen7, or dpa 8) were prepared similarly. The air-stable solid2036 J. CHEM. SOC. DALTON TRANS. 1994Table 7 Atomic coordinates ( x lo4) for complex 3X10 144(1)9 603(1)4 064(4)7 674(6)3 8 17(9)4 321(9)5 487( 10)2 797( 10)4 849(12)3 349(18)8 569( 1 1)6 698( 10)8 876(12)6 431(12)7 144(17)8 178(11)1030(8)10 753(8)10 lOl(8)8 31 l(8)7 399(8)7 720(8)11 884(7)9 406(8)10 31 l(8)9 092(8)11 428(9)10 192(11) -10054(15) -8 810(11)8 419(12)12 301(14)13 488( 15)11 761(10)12 555(10)13 330(11)Y2 564( 1)8 325(4)5 722(3)7 822(7)8 855(8)8 154(10)8 710(11)9 321(9)7 393(9)6 805(7)4 616(6)5 352(8)6 106(8)5 781(8)5 686(8)1 118(6)1 731(6)2 351(6)358(6)820(6)1 752(6)1 525(6)828(6)2 851(6)3 486(7)91 l(1)- 529(6).1 323(10)- 2 421(11)3 055(8)3 323(9)4 083(11)4876(11)488(7)36(7)- 540(8)z2 723( 1)2 614(1)3 622(2)4 028(3)2 823(4)4 428(4)3 724( 5 )3 502(5)3 353(5)3 892(6)4 087(6)3 959(6)3 800(7)4 286(9)3 236(7)4 829(5)1782(4)1354(4)1605(4)2 098(4)1977(4)2 227(4)3 403(4)3 706(4)2 792(4)3 625(4)2 743(6)2 639(8)4 169(6)4 875(6)3 243(7)3 590(8)1 445(5)1887(6)1551(6)2 975(5)X13 327( 10)14 233(12)12 530( 10)11 762(10)9 686(10)9 461(10)8 910(12)8 564(13)7 888(14)8 779(12)9 337(11)7 825(9)6 817(11)6 373(12)6 920( 1 1)6 462( 14)7 915(12)8 380(10)6 706( 10)5 664( 10)4 724(11)4 780( 10)3 780(11)5 827(11)6 784( 10)13 090(11)14 234(13)14086(13)12 835(11)11 744(10)9 983( 10)8 639(11)7 676(12)8 104(10)10 339(9)Y- 667(8)- 1 245(9)-221(8)344(7)2 914(7)2 575(8)3 lOO(9)3 929( 10)4 471(11)4 282( 10)3 782(9)- 674(7)-1 308(8)- 2 303(9)- 2 656(9)- 3 733( 10)- 2 022(9)- 1 030(8)2 236(7)1822(8)2 363(8)3 294(8)3 843(9)3 689(8)3 177(8)1 895(8)2 292(9)2 278(9)1 926(8)1 543(7)1 165(7)1 181(7)824(8)462(8)478(7)Z810(6)469(6)387(6)692(5)1082(5)353(6)- 153(7)- 458(8)82(7)796(7)1298(7)1801(5)2 084(6)1 805(6)1233(6)924( 7)945(6)1219(5)2 030(5)1 489(5)1287(6)1628(6)1 390(6)2 154(6)2 368(6)3 204(6)3 709(7)4 429(7)4 630(6)4 117(5)4 282(5)4 983(5)5 064(6)4 487(6)3 800(5)dissolve in acetonitrile or nitromethane to give brown solutionswhich decompose slowly in air.(2,2'-Bipyridyl)[ 1,2-bis(diphenylphosphino)ethanel (p-carbonyl)bis(p-di-p-tolyltriazenido-N 'N3)dirhodium Bis(hexa-J-luorophosphate), [Rh2(p-CO)(dppe)(bipy)(p-RNNNR),]-[PF,], !).-To a stirred solution of [(Rh,(p-I)(CO)(bipy)(p-RNNNR),),][PF,], (0.15 g, 0.07 mmol) in CH,Cl, (25 cm3)was added AgPF, (0.04 g, 0.16 mmol).After 10 min the darkgreen solution was filtered through Celite to remove AgI, anddppe (0.054 g, 0.14 mmol) added. After 30 min the intense greensolution was filtered through Celite and reduced in volume invacuo. Addition of diethyl ether gave a green powder which waspurified from CH,Cl,-diethyl ether, yield 0.162 g (79%). Thecompound [Rh,(p-CO>(dppm)(bipy)(p-RNNNR),I[PF,], 10was similarly prepared.(2,2'- Bipyridyl)[ 1,2-bis(diphenylphosphino)ethane- P] carbonyl-bis(p-di-p-tolyltriazenido-N'N3)dirhodium Hexafuorophos-phate, [Rh,(CO)(dppe-P)(bipy)(p-RNNNR),] [PF,] 11 .-Toa stirred solution of [Rh,(p-CO)(dppe)(bipy)(p-RNNNR),]-[PF,], (0.105 g, 0.069 mmol) in thf (30 cm3) was added NaBH,(0.003 g, 0.079 mmol).After 1.5 h the brown solution was filteredthrough Celite and evaporated to low volume in vacuo. Additionof hexane precipitated a brown oily solid, and purification fromCH,Cl,-hexane gave a brown powder, yield 0.076 g (80%).(2,2'- Bipyridyl)carbonylbis(p-di-p-tolyltriazenido-N N 3)( 1 -methyl-2-sulfanylimidazolato)dirhodium Hexafuorophosphate,[Rh2(CO)(msim)(bipy)(p-RNNNR)2][PF6] 13.-To a stirredsolution of [{Rh2(p-I)(CO)(bipy)(p-RNNNR)2)2][PF6]2 (0.15g, 0.065 mmol) in CH,Cl, (40 cm3) was added AgPF, (0.035 g,0.13 mmol). After 30 min the green solution was filtered throughCelite and the filtrate evaporated to dryness. The residue wasthen dissolved in thf ( 5 cm3) and the solution added to amixture of 1 -methyl-2-sulfanylimidazole (0.05 g, 0.13 mmol)and NaH (3 mg, 0.13 mmol) in thf (5 cm3).The solvent wasremoved in vacuo and the residue extracted with CH,Cl, (10cm3). Addition of hexane (10 cm3) and partial removal of thesolvent in uacuo gave a green powder which was purified to givethe green product, yield 0.105 g (71%).(2,2'- Bipyridyl)carbonylbis(p-di-p-tolyltriazenido-N' N3)(2-sulfanylpyrimidinato)dirhodium Hexafuorophosphate, [Rh,-(Co)(spym)(bipy)(p-RNNNR),][PF,] 14.-To a stirredsolution of [{Rh,(p-I)(CO)(bipy)(p-RNNNR),),][PF,], (0.1g, 0.045 mmol) in CH,Cl, (25 cm3) was added AgPF, (0.025 g,0.1 mmol). After 10 min the dark green solution was filteredthrough Celite, and 2-sulfanylpyrimidine (0.01 g, 0.089 mmol)was added.After stirring for 1 h the green solution was filteredthrough Celite and reduced in volume in vacuo. Addition ofhexane gave a green solid; purification from CH,Cl,-hexanegave a green powder, yield 0.073 g (74%).The compounds [Rh2(CO)(N-S)(bipy)(p-RNNNR).2][PF6](N-S = msim 13, stz 15, or sbzim 16 were similarly prepared.(2,2'- Bipyridyl)carbonyldichlorobis( p-di-p-tolyltriazenido-N N3)dirhodium [R h2( CO)Cl2( bipy)(p-RNNNR),] 17.-To a stirred solution of [(Rh,(p-I)(CO)(bipy)(p-RNNNR),),][PF,], (0.1 1 g, 0.05 mmol) in CH,Cl, (40 cm3)was added AgPF, (0.026 g, 0.1 mmol). After 10 min the greensolution was filtered through Celite to remove the precipitate ofAgI and the filtrate was evaporated to dryness in vacuo. Theresidue was then dissolved in MeOH (1 5 cm3), NaCl(O.03 g, 0.J.CHEM. SOC. DALTON TRANS. 1994 2037Table 8 Atomic coordinates ( x lo4) for complex 10a=2CH2C1,* Partial occupancy (in range 0.19-0.74) disordered atom.X4 722( 1)5 462( 1)6 493(4)4 784(4)7 153(7)4 871(6)2 775( 10)4 562( I 1)9 862( 16)10 243(15)9 423(20)9 459(23)10 228(39)8 875(31)9 889(37)7 924(21)6 737( 17)7 508(15)6 336(15)7 491(20)6 755(26)5 724(13)5 324( 16)4 526(18)4 442( 16)5 092( 16)3 894( 14)4 758(10)6 370( 11)6 559(11)6 020(9)4 469( 10)4 266( 1 1)4 428( 10)3 361(10)4 866( 10)4 965( 13)5 659( 12)7 450( 14)8 217(15)8 937(16)8 910(18)8 148(15)7 424( 14)6 976( 12)6 803(15)7 189(18)7 735( 16)7 937( 15)7 524(13)3 647( 14)Y10 626(1)9 952( 1)9 022(3)8 904(3)8 246(5)5 954(4)7 786(8)7 432(10)8 906( 14)7 407( 13)963( 17)1617(18)1697(32)277(27)1 762(39)7 776(18)8 099(9)8 363(10)8 651(17)8 950(13)7 560(15)5 587(10)6 669( 10)5 910(14)5 197(10)6 132(19)6 182(16)9 127(7)10 823(8)11 103(8)11 OlO(8)10 712(8)11 298(9)11 356(7)10 338(8)10 029(9)9 707(13)8 317(10)8 991(10)8 563(12)8 547( 12)8 919(14)9 336( 12)9 381(11)8 797(10)8 161(13)8 048(16)8 547( 13)9 195(12)9 297( 12)8 621(11)z1819(1)2 887( 1)2 897(2)3 lOl(2)2 572(4)1007(5)1018(6)1 274(9)1 020(8)- 119(3)312(11)1 024(20)582( 17)93( 13)- 290( 13)- 836(25)312(7)- 564(7)- 373(11)96(8)-351(9)2 534(9)2 535(10)2 002(8)2 649(9)3 102(7)2 591(14)2 022(5)2 805(5)2 416(6)1986(5)2 986(6)2 750(6)2 325(5)1 515(6)1223(5)2 205(7)2 948(7)3 421(7)3 412(8)3 832(8)4 270( 10)4 256(8)3 851(7)2 388(6)2 133(8)1742(10)1 606(9)1 839(8)2 245(7)2 724(7)X3 467( 16)2 623( 17)1 966(16)2 094(16)3 016(14)4 688( 15)5 446( 17)5 445(20)4 526( 19)3 788(17)3 848( 16)7 025(14)6 725( 14)7 364(15)8 281(16)8 600( 16)7 964( 14)8 990( 18)6 359( 14)7 326(15)7 601(17)6 983(16)6 070(15)5 754(13)7 296(18)4 085(13)3 116(13)2 754(16)3 252( 17)4 215(15)4 620( 14)2 808( 17)4 356( 13)3 791(13)3 722( 15)4 221(16)4 820(13)4 930( 13)4 113(16)2 628(15)1 758(18)1612(21)2 372( 16)3 255(15)4 122(15)4 063( 17)4 917(17)5 730( 17)5 676( 15)3 886(24)Y7 871(12)7 692(15)8 185(13)8 888( 13)9 129(12)8 703( 11)8 551(12)8 390( 14)8 367( 14)8 541(12)8 720( 12)10 985( 10)11 217(10)11 308(11)11 216(11)10 993(12)10 878(10)11 301(15)11 353(10)11 387(11)11 671(12)11 889(12)11 869(11)11 595(9)12 252(14)10 666( 10)10 794(10)10 713(12)10 528(13)10 385( 11)10 463( 1 1)10 471(14)12 073( 11)12 242(11)12 930( 12)13 455( 13)13 319(11)12 622( 10)14 212(13)10 550(12)10 400( 1 3)10 054( 15)9 829( 12)9 989( 12)9 832( 10)9 935( 13)9 263( 13)9 445( 12)9 853(11)7 648(21)Z2 639(8)2 377(8)2 189(8)2 270(8)3 718(8)4 082(8)4 570( 10)4 633( 1 1)4 293(8)3 830(8)3 255(7)3 643(7)4 089(8)4 138(8)3 744(8)3 290(7)4 630(9)1 595(7)1634(8)1 224(8)830(8)1 197(6)3 4 17(6)3 326(7)3 734(8)4 195(9)4 266(8)3 860(7)4 628(9)2 130(7)1658(7)1484(8)1 746(8)2 192(7)2 391(7)1 533(9)1 684(8)1452(9)996( 10)800(9)1 072(8)949(7)504(8)405(9)7 18(8)1 140(8)1 329(13)2 549(7)794(7)379(9)mmol) added, and the mixture stirred for 1 h.The solvent wasthen removed in uacuo and the residue extracted with CH,Cl,(1 5 cm3). Addition of hexane and partial removal of the solventin vacuo gave the green microcrystalline product, yield 0.065 g(71%).(2,2'-Bipyridyl)carbonylbis(~-di-p-tolyltriazenido-N1 N3)-din it r itodzrhodium [ R h, (CO)(NO,), (bip y)( p- RNNNR), ] 1 9.-To a stirred solution of [(Rh2(p-1)(CO)(bipy)(p-RNNNR),},]-[PF6I2 (0.25 g, 0.11 mmol) in CH,Cl, (60 cm3) wasadded AgPF, (0.06 g, 0.22 mmol). After 10 min the greensolution was filtered through Celite to remove the precipitate ofAgI and the filtrate was evaporated to dryness in uacuo. Theresidue was then dissolved in MeOH (15 cm3) and NaNO,(0.03 1 g, 0.45 mmol) was added to give a brown precipitate after5 min. After a further 30 min the volume of the solvent wasreduced in uacuo. The brown solid was then filtered off andwashed with MeOH (2 x 4 cm3), yield 0.150 g (70%).Crystal Structure Determinations of [Rh,(NCMe),-RN"R),][PF6],~2CH2Cl2 10a.2CH2C12 and [ {Rh,(CO)-(0,PF,)(p-02PF,)(bipy)(p-RNNNR)~}2]~2.3C6H14 1202.3-C,H,,.-Many of the details of the structure analyses carriedout on the complexes are listed in Table 6.X-Ray diffractionmeasurements were made at room temperature using Siemensfour-circle P3m diffractometers on single crystals mounted inthin-walled glass capillaries with graphite-monochromatedMo-Ka X-radiation (x = 0.710 73 A). Cell dimensions for eachanalysis were determined from the setting angles of 25, 44 and43 centred reflections respectively.For each structure analysis, intensity data were collected for(biPY)(~-RN"R),ICPF,I, 3, CRh2(C1-CO)(dPPm)(biPY)(C12038 J. CHEM. SOC. DALTON TRANS. 1994Table 9 Atomic coordinates ( x lo4) for complex 12*2.3C6H,,X8 81 l(1)9 077( 1)8 782(4)9 564(4)9 312(11)8 278(10)9 551(12)9 073(8)8 551(8)9 335(7)9 838(7)8 968( 1 1)9 873(9)8 289(9)7 786(9)7 932(9)8 555(8)8 543(9)8 702(8)8 943(9)9 691(8)9 546( 12)8 198(10)8 534( 13)8 457(16)7 972(14)7 849(15)7 623(14)7 774(13)7 379(12)7 230( 13)6 722( 15)6 321(14)5 729(16)6 446( 15)Y2 076( 1)2 331(1)1 446(5)3 201(5)1 988(13)1 658(11)4 049(11)3 216(15)1 757(9)2 770( 10)3 062( 10)654( 12)906( 1 1)1718(11)1817(11)2 070( 12)3 314(10)3 680(12)3 263( 10)879( 10)1 985(11)1461(15)1 196(12)1 312(17)745( 18)2 1 8( 1 7)119(18)622( 15)2 420( 1 5)2 287( 16)2 652( 19)3 107(17)3 512(21)3 264( 18)- 284( 18)z3 673(1)2 869(1)4 905(3)1 784(3)5 252(7)5 129(7)1 894(11)1 246(7)4 363(6)2 139(6)3 286(6)5 009(8)3 018(7)2 525(8)2 646(8)3 147(8)2 825(7)3 240(8)3 692(7)3 681(7)4 173(7)2 087(8)1735(10)1 369(13)1 206(11)728( 12)1 520(12)1 963(11)3 192(10)3 623(11)3 668( 13)3 291(12)3 335(14)2 808( 13)2 955(9)X7 OOO( 12)8 326( 12)8 378(13)8 191(13)7 859( 13)7 629(15)7 796( 14)7 986( 12)8 813(10)8 578( 13)8 71 l(14)9 037( 13)9 lll(14)9 195(12)9 111(12)10 046( 12)10 631(13)10 871(16)10 512(14)9 912(12)9 503(11)9 678( 12)8 665(12)8 534( 12)437136716722 2562 3362 50008276 19 201(12)Y2 888(15)3 793(15)4 599(16)5 061(18)4 704(17)5 137(19)3 932( 18)3 461(16)3 740(13)3 526(16)3 988(17)4 733(16)5 234( 16)4 910(17)4 474( 15)2 558(16)2 486( 17)1712(19)1091(18)1 243(14)623( 13)- 126(14)- 635(15)- 41 2( 14)375( 14)6 5646 7597 2543 2693 2262 5006 1966 2176 871z2 780( 10)2 376(10)2 367( 12)1 906( 12)1 408( 1 1)908( 13)1419(12)1871(11)4 122(8)4 495( 10)4 981(12)5 015(11)5 464( 1 1)4 603(11)4 169(10)4 41 l(10)4 794( 1 I )4 918(13)4 660(11)4 297(9)4 00 l(9)4 084( 10)3 779( 10)3 466(9)3 41 l(9)135714301 2465 4665 0135 0002 5002 0451241unique portions of reciprocal space to the limit of observablediffraction (rather low 28,,, in all three cases due to poorcrystallinity). Corrections were applied for Lorentz, polaris-ation, and long-term intensity fluctuations, the latter on thebasis of the intensities of three check reflections repeatedlymeasured during data collection.Corrections for X-rayabsorption effects were applied on the basis of azimuthal scandata. The structures were solved by heavy-atom (Pattersonor direct and Fourier difference) methods, and refined byfull-matrix least squares against P and against F2 for12*2.3C6H1,.'2 For 3 all rhodium, phosphorus, fluorine andnitrogen atoms were assigned anisotropic displacementparameters. For 10a-2CH2C12 all rhodium, phosphorus,fluorine, oxygen and nitrogen atoms and C1(1), C1(2), C(l) andC(2) were assigned anisotropic displacement parameters. For12-2.3C6H 14 all rhodium, phosphorus, fluorine and oxygenatoms and C( 1) were assigned anisotropic displacementparameters.All other non-hydrogen atoms were assignedisotropic displacement parameters. All hydrogen atoms wereconstrained to ideal geometries with C-H 0.96 8, and assignedfixed isotropic displacement parameters. One of the twomolecules of dichloromethane in 10a.2CH2C1, was severelydisordered and was modelled with partial occupancy atom sites.The solvent in 1?2.3C6Hl4 is also severely disordered, aboutcrystallographic 1 and C2 sites. Nine carbon atom positionswere assigned with total occupancy seven. A variety of modelswas refined all of which were unstable and had unrealisticgeometries. The final model had atom positions and isotropicdisplacement parameters fixed at the values obtained in the bestof these refinements. The model is therefore non-stoichiometric,corresponding to 2.33 hexanes of crystallisation per molecule of12. No hydrogen-atom positions were included in the refinementmodel for solvent molecules.Final difference syntheses showed no chemically significantfeatures, the largest maxima being close to the metal and solventatoms. Refinements converged smoothly to residuals given inTable 6. Tables 7-9 report the positional parameters for thesestructure determinations. All calculations were made withprograms of the SHELXTL PLUS l 2 system and SHELXL93.' Complex neutral-atom scattering factors were taken fromref. 14.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 research studentships (to P. M. H. andG. M. R.) and for funds to purchase the ESR spectrometer, theDireccion General de Investigacion Cientifica y Tecnica(DGICYT) for a research fellowship (to F.V.), the Royal Societyand Consiglio Nazionale delle Ricerche (C. N. R.), Italy for anexchange grant (to C. M. and A. G. O.), and Johnson Mattheyplc for a generous loan of rhodium salts.References1 T. Brauns, C. Carriedo, J. S. Cockayne, N. G. Connelly, G. GarciaHerbosa and A. G. Orpen, J. Chem. SOC., Dalton Trans., 1989,2049.2 N. G. Connelly, T. Einig, G. Garcia Herbosa, P. M. Hopkins,C. Mealli, A. G. Orpen and G. M. Rosair, J. Chem. SOC., Chem.Commun., 1992, 143.3 C. A. Crawford, J. H. Matonic, W. E. Streib, J. C. Huffman, K. R.Dunbar and G. Christou, Znorg. Chem., 1993,32,3125.4 J. M. Casas, R. H. Cayton and M. H. Chisholm, Inorg. Chem.,1991,30,358J. CHEM. SOC. DALTON TRANS. 1994 20395 N. J. Dhillon and A. G. Orpen, personal communication.6 M. A. Bennett, J. C. Jeffery and G. B. Robertson, Inorg. Chem.,1981,20, 323.7 J. Howell, A. Rossi, D. Wallace, I. K. Harak and R. Hoffman,Quantum Chemistry Program Exchange, 1977,10,344; C . Mealli andD. M. Proserpio, J. Chem. Educ., 1990,67, 399.8 R. Hoffman, C. Minot and H. B. Gray, J. Am. Chem. Soc., 1984,106,2001.9 T. R. Felthouse, Prog. Inorg. Chem., 1982,29, 73.10 N. G. Connelly, P. M. Hopkins, A. G. Orpen, G. M. Rosair andF. Viguri, J. Chem. SOC., Dalton Trans., 1992, 2907.11 C. White, S. J. Thompson and P. M. Maitlis, J. Organomet. Chem.,1977,134,319.12 G. M. Sheldrick, SHELXTL PLUS, Revision 4.2, University ofGottingen, 1990.13 G. M. Sheldrick, SHELXL 93 J. Appl. Crystallogr., 1994, inpreparation.14 International Tables for X-Ray Crystallography, Kynoch Press,Birmingham, 1974, vol. 4; International Tables for Crystallography,Kluwer, Dordrecht, 1992, vol. C.Received 3rd February 1994; Paper 4/00664

ISSN:1477-9226    

DOI:10.1039/DT9940002025

出版商:RSC    

年代:1994

数据来源: RSC