Organometallics 1983, 2, 352-355
352
Scheme I
diate such as A, followed by rearrangement of a trimethylsilyl group attached to silicon to an adjacent unsaturated atom as shown in Scheme 11.
S
Acknowledgment. The authors are grateful to Professors A. Nakamura and H. Yasuda, Department of Macromolecular Science, Faculty of Science, Osaka University, for useful discussions. We also express our appreciation to Toshiba Silicon Co., Ltd., and Shin-etsu Chemical Co., Ltd., for a gift of organochlorosilanes.
4
Registry No. 1, 80073-04-7; 2, 84081-97-0; 3, 53268-89-6; 4, 18766-02-4;5,1450-16-4;6,84081-981; 7,79633-980; 8,84081-99-2; 9,84082-00-8; 10,84082-01-9; Ph2MeSiLi,3839-30-3; EtMe2SiC1, 6917-76-6; Ph2MeSiSiMePh2,1172-76-5.
Reactivity of Multisite-Bound Ligands. Nucleophilic Attack at Carbon in Cluster Acetyiides by Isocyanides and Amination of the Products. X-ray Structures of HRu3(CO),[C( CN-t -Bu)CPh] and OS~(CO),[C(C(NH-~-BU)(NH-~-BU))CP~](PP~,)
2
EtMe2SiC1
Shane A. MacLaughiin, James P. Johnson, Nicholas J. Taylor, and Arthur J. Carty’ Guelph-Waterloo Centre, Waterloo Campus Department of Chemistry, University of Waterloo Waterloo, Ontario N2L 3G1, Canada
6
Enrico Sappa
Scheme I1
9
Istituto di Chimica Generale ed Inorganica Universiti di Torino, Corso M. D ’Azeglio 48 Turin, Italy Received August 30, 1982
10
pent-3-ene (g7 and lo8) in a ratio of 131. Fractional recrystallization of the crystals gave 9 in a pure form, but pure 10 could not be obtained. Compound 10 thus obtained was always contaminated with a small amount of 9 (ca. 14%). The production of anion 8 can be understood in terms of the transient formation of a pentacoordinate interme(7) Compound 9: mp 172-173 OC; IH NMR 6 -0.51 (9 H, s, Me,&), -0.25 (9 H, s, Me3Si), 0.28 (9 H, s, Me3Si), 0.78 (3 H, s, MePh,Si), 0:90 (3 H, s, MeSi), 2.15 (1H, s, HC), 6.70-7.00 and 7.15-7.70 (20 H, m, ring protons); mass spectrum, m / e 662 (M+). Anal. Calcd for C39H54Si5:C, 70.62; H, 8.21. Found: C, 70.48; H, 8.33. ( 8 ) Compound 10: ‘H NMR 6 -0.60 (9 H, s, Me3Si), -0.18 (9 H, s, Me3Si),0.21 (9 H, s, Me&), 0.68 (3 H, s, MePhSi), 0.89 (3 H, s, MeSi), 2.15 (1H, s, HC), 7.00-7.45 and 7.54-7.75 (20 H, m, ring protons); mass spectrum, m / e 662 (MS).
0276-7333/83/2302-0352$01.50/0
Summary: Regiospecific addition of the isocyanide tBuNC at the a-carbon atoms of the multisite-bound acetylides in the trinuclear clusters HRu,(CO),(~,-T~-C=CP~) and Os3(C0),(p3-q2-C=CPh)(PPh2) generates carboncarbon bonds via isocyanide-acetylide coupling. X-ray structural analysis of (p-H)Ru3(CO), [C(CN-t -Bu)CPh] has confirmed the synthesis of a new zwitterionic p3-)7’ ligand via nucleophilic attack at carbocationic carbon. Derivatization of the isocyanide adduct Os,(CO),[C(CN-t-Bu)CPh](PPh,) with n-BuNH, affords the carbenium zwitterion Os,(CO),[C(C(NH-t -Bu)(NH-n -Bu)]CPh](PPh,) whose structure has been determined by X-ray analysis. Direct nucleophilic attack by uncharged carbon nucleophiles at carbocationic multisite-bound ligands in clusters may be a useful strategy for the elaboration of unsaturated ligands.
Multisite coordination on the edge or face of a metal cluster is a key step in the activation of small molecules such as CO, olefiis, and acetylenes.’ The simple reactivity patterns of p-v-bound ligands are thus of fundamental significance to the design of strategies for the elaboration of these molecules. In the specific context of CO hydrogenation there is evidence for proton induced cleavage of K ~ - ~ ~ -inC HFe4(C0)13O yielding an exposed carbide carbon atom that on subsequent protonation affords methanea2 Our attention has focussed on the chemical behavior of cluster-bound acetylide~,~ ligands which are (1) Muetterties, E. L.; Stein, J. Chem. Reu. 1979, 79, 479.
(2) Holt, E. M.; Whitmire, K. H.; Shiver, D. F. J . Organomet. Chem. 1981,213,125. See also: Tachikawa, M.; Muetterties, E. L. J. Am. Chem. SOC.1980, 102, 4541. (3) Carty, A. J. Pure Appl. Chem. 1982, 53, 113.
8 1983 American Chemical Society
Organometallics, Vol. 2, No. 2, 1983 353
Communications Scheme I But
h
/Ph
F
Scheme I1 0,"'
H
H
Figure 1. The molecular structure of HRu3(CO),[C(CN-t-Bu)CPh] as drawn by ORTEP to illustrate the nature of the new ligand.
2 -
3 -
Y(&N) 2201 cm-l; 'H NMR (C&) 6 -18.9 (s,Ru-H-Ru), 0.7 (s, C(CH3),), 7.0 (m, Ph). Similarly, slow addition of t-BuNC (47 mg) in heptane (226 (7 mL) to a solution of 0s3(CO),(p3-q2-CWPh)(PPh2) mg, 0.2 mmol) in toluene (10 mL) and heptane (7 mL) gave an orange solution. IR monitoring indicated complete consumption of starting material. Removal of solvent in vacuo and recrystallization of the orange solid from heptane-toluene containing a trace of t-BuNC gave orange crystals of 2 (94%): IR (C7H8)v(C0) 2068 (m), 2046 (vs), 2013 (s), 1994 (m), 1962 (m), v(C-N) 2235 (w), 2190 (w) cm-l; 31PNMR (C6D6) 6(H3PO4) -70.0; 'H NMR (C6D6) 6 0.60 (5, t-Bu), 6.91-7.26 (m), 7.49 (t), 8.13 (dd, Ph). The high-field 31Pchemical shift of the PPh2group in 2 (-70.0 ppm) suggests the absence of a substantial Os-=Os interaction along the edge of the cluster bridged by the phosphido group? The location of the isocyanide in these adducts was established by a single-crystal X-ray structural study of 1.l0 A perspective view of the adduct drawn so as to illustrate the isocyanide-acetylide interaction is shown in Figure 1. In the closed, triangular skeleton, there are two strong Ru-Ru bonds (Ru(1)-Ru(3) = 2.7372 (4) A,Ru(2)-Ru(3) = 2.7497 (4) A)with the third significantly longer (Ru(1)-Ru(2) = 2.9644 (5) A) and bridged by a
structurally and electronically related to CO and the carbides. Previous work has shown that neutral binuclear4 and trinuclear3v5p-q2-acetylidesare unusually sensitive to attack at a-and @-carbonatoms by neutral nucleophiles. Very recently addition of phosphines to HOs3(CO),(p3$-C=CR) has been shown? We describe herein the direct synthesis of carbon-carbon bonds via regiospecific addition of the isocyanide t-BuNC to the a-carbon atoms of the cluster bound p3-q2-acetylidesin HRu3(CO),(C e P h ) and Os3(C0),(C-CPh) (PPh,) ,generating HRu3(CO), [C(CNt-Bu)CPh] (1, Scheme I) and Os,(CO),[C(CN-t-Bu)CPh](PPh,) (2). Facile amination of the latter with nBuNH2 affords Os3(CO),[ C{C(NH-n-Bu)(NH-t-Bu)]CPh](PPh2)(3), a carbenium zwitterion (Scheme 11). The addition of uncharged carbon nucleophiles to cluster-bound unsaturates may thus be a useful synthetic strategy. The similarityin ligand behavior of CO and the isocyanides also suggests that due consideration be given to the possibility of direct attack by CO on p-q-coordinated molecules as a mechanism of C-C bond formation in cluster chemistry. Treatment of (~-H)Ru~(CO)~(~~-~~-C=CP~)~ (0.21 g, 0.32 mmol) in n-heptane (10 mL) at 0 "C with t-BuNC (35 (9) Carty, A. J. Adu. Chem. Ser. 1982, No. 196, 163. (10) Crystals, of R u ~ ~ ~ NareCmonoclinic ~ ~ H ~of ~s ace group P21/c pl, 0.33 mmol) gave a yellow cloudy mixture. Florisil with a = 9.798 (1) A, b = 14.553 (2) A, c = 18.836 (2) @ = 99.30 (1)O, chromatography yielded three products. The last yellow V = 2650.5 A3, 2 = 4, p(calcd) = 1.856 g ~ m - p(measd) ~, = 1.86 g ~ m - and ~, band eluted was judged by its high frequency v(C=N) p (Mo Ka) = 16.96 cm-'. Intensity data were collected on a crystal of dimensions 0.25 X 0.23 X 0.24 mm using 6-28 scans (3.2O < 26 5 50.0°) band to be the product of attack on the acetylide. Cryswith a variable scan speed of 2.,0-29.3' min-' and a scan width of +0.8O tallization from n-heptane at -10 "C overnight afforded below Kal to 0.8O above Ka2 on a Syntex P21diffractometer. From a yellow crystals of an adduct, HRu,(CO),(C=CPh) ( t total of 4709 measured reflections, 3695 had I 1 3 4 and were used in the structure solution and refinement. Two standard reflections moniBuNC) (1) (-20%): IR (C6H12) v(CO), 2080 (m), 2054 (s), tored after every 100 measurements showed no change in intensity over 2024 (vs), 2013 (s), 1997 (m), 1986 (m), 1970 (w), 1956 (w), the course of data collection. With p = 16.96 cm-' for these atoms no
x,
(4) (a) Wong, Y. S.; Paik, H. N.; Chieh, P. C.; Carty, A. J. J. Chem. SOC.Chem. Commun. 1975,309. (b) Carty, A. J.; Taylor, N. J.; Smith, W. F.;Paik, H. N.; Yule, J. E. Ibid. 1976,41. (c) Carty, A. J.; Mott, G. N.; Taylor, N. J.; Ferguson, G.; Khan, M. A.; Roberts,P. J. J. Organomet. Chem. 1978,149,345. (d) Carty, A. J.; Mott, G. N.; Taylor, N. J.; Yule, J. E. J. Am. Chem. SOC.1978,100,3051. (5) Deeming, A. J.; Hasso, S. J. Organomet. Chem. 1976, 112, C39. (6) Henrick, K.; McPartlin, M.; Deeming, A. J.; Hasso, S.; Manning, P. J. Chem. SOC.,Dalton Trans. 1982,899. (7) This hydride was synthesized by a modification of the procedures described for the t-butyl analogue by Sappa and co-workers. See: Sappa, E.; Gambino, 0.; Milone, L.; Cetini, G. J. Organomet. Chem. 1972,39, 169. (8) Satisfactory analyses are available for all compounds described herein.
absorption correction was deemed necessary. Transmission factors varied between 0.59 and 0.74. The three ruthenium atoms were located in a Patterson synthesis and light atoms via a subsequent Fourier map. Refinement of all non-hydrogen atoms with isotropic parameters gave a value R (R = CIFoI- IFcl/CIFol)of 0.067. Two cycles of refinement with anisotropic coefficients reduced R to 0.034. A difference map a t this stage allowed the location of all hydrogen atoms. These were included in subsequent refinements. The converged R and R, (R, = [CwlFoI lFc1)2/Cw(lFo1)2]'/2) values were 0.024 and 0.027. A final difference map was featureless. Scattering factors were taken from the compilations of ref l l a and, for hydrogen, the data of Stewart a t al.llb Both real and imaginary components of anomalous dispersion were applied to corrections for the ruthenium atoms. Computer programs used have been described in detail elsewhere.4d (11) (a) "International Tables for X-ray Crystallography"; Kynoch Press: Birmingham, England, 1974; Vol. IV. (b) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J. Chem. Phys. 1965,42,3175.
354 Organometallics, Vol. 2, No. 2, 1983
CIS)
Figure 2. An ORTEP plot of the structure of the zwitterionic carbenium species O~(CO),[C(C(NH-t-Bu)(NH-n-Bu))CPh] PPh,. T h e open edge of the Os3 triangle is between Os(1) and os(3).
hydride (Ru(l)-H(l) = L.67 (5) A, Ru(2)-H(1) = 1.73 (5) A). The isocyanide is attached via C(12) to the original a-carbon atom of the acetylide C(l1). Thus nucleophilic attack on the p3-q2-acetylideby t-BuNC has resulted in the formation of a strong carbon-carbon bond (C(11)-C(12) = 1.400 (5) A).', The "carbon-coordinated" isocyanide is essentially linear (C(ll)-C(l2)-N = 175.2 (3)O, C(12)N-C(13) = 174.6 ( 2 ) O ) but the acetylide, previously coordinated as a perpendicular acetyleneI3 to Ru(1) and Ru(2), is now best described in terms of parallel interactions with Ru(1) and Ru(2) and an q2 bond to Ru(3). The C(l0)-C(11)bond length (1.415 (3) A) is considerably longer than in the tert-butyl analogue of the parent hydride (1.315 (3) A).'* On the basis of spectroscopic data and subsequent chemical behavior (vide infra) the osmium cluster Os3(CO),(C=CPh)(PPh,)(t-BuNC)has a closely related structure but with a three-electron donor PPhz group replacing a metal-metal bond and p-hydride in 1. Although carbon-carbon bond formation by nucleophilic attack on a coordinated ligand is a well-established principle of organometallic ~hemistry,'~ the direct synthesis of C-C bonds on the face of a neutral cluster via coupling of a neutral carbon nucleophile with a multisite-bound ligand has few precedents.16 Direct coupling of surface bound carbide and carbon monoxide has been documented as a possible mechanism for C-C bond formation in carbon monoxide hydrogenation" and CO attack on a mononuclear manganese carbene generating a metallocyclopropanone has been reported.ls The closest analogies are (12) The covalent radius of an sp-hybridized carbon atom is 0.70 A. Thus a single bond between two sp carbon atoms should have a bond length of -1.40 A. If C(11) (Figure 1) is considered as close to sp2, then a predicted C(ll)-C(12)single bond would have a length of -1.44 A. The measured distance is compatible with a strong single bond. (13) For a recent account of perpendicular and parallel metal-acetylene interactions see: Hoffman, D. M.; Hoffman, R.; Fisel, C. R. J. Am. Chem. SOC. 1982, 104, 3858. (14) Catti, M.; Gervasio, G.; Mason, S. A. J. Chem. SOC.,Dalton Trans. 1977, 2260. (15) See for example: Collman, J. P.; Hegedus, L. S. "Principles and Applications of Organotransition Metal Chemistry"; University Science Books: Mill Valley, CA, 1980. For a recent discussion of metal acetylide reactivity see: Kostic, W. M.; Fenske, R. F. Organometallics 1982, I , 974. (16) We have briefly reported activation of edge bridging acetylides in binuclear complexes to attack by carbenes and isocyanides: (a) Carty, A. J.; Taylor, N. J.; Smith, W. F.; Lappert, M. F.; Pye, P. L. J. Chem. SOC., Chem. Commun. 1978,1017. (b) Carty, A. J.; Mott, G. N.; Taylor, N. J. J. Organomet. Chem. 1981,212, C54. (17) See, for example, ref 1, p 487. (18) Herrmann, W. A,; Plank, J.; Ziegler, M. L.; Weidenhammer, K. J . Am. Chem. SOC.1979,101, 3134.
Communications the formation of C-C bonds in reactions of the neutral iron carbide cluster Fe4(C0)13Cwith C0,19 the generation of acylium species [CO~(CO)~CCO]+ from CO,(CO)~CC~ in the presence of a Lewis acid,20and the synthesis of the ketenylidene complex H20s3(CO)&CCO)via thermal loss of CO Some of these reactions from OS~(CO)~~(~-CO)(~-CH~).~~ may however involve intramolecular CO m i g r a t i o r ~ s . ~ ~ ~ ~ ~ The isolation of clusters 1 and 2 suggested the possibility of further derivatizing the unsaturated fragment derived from the acetylide and isocyanide. Treatment of 2 (63 mg, 0.053 mmol) in toluene at 0 OC with n-BuNH, (5 mL) and removal of volatiles in vacuo followed by recrystallization from heptane-toluene(1:l) afforded Os,(CO),[C(C(NH-tBu)(NH-n-Bu)JCPh](PPh,) (3) in 98% yield.22 Analogous CH3NH2and EtNH, derivatives have been characterized. The structure of 323(Figure 2) confirms that the amine has added across the "carbon-coordinated" isocyanide converting the isocyanide to a carbene with retention of the C(l1)-C(12) bond in 2. The new hydrocarbyl ligand is coordinated to Os(1) and Os(3) via u bonds to C(l0) and C(11) and as in 2 via an q2 interaction with 042). Within the aminocarbene moiety the C(12)-N(1) (1.327 (22) A) and C(12)-N(2) (1.321 (22) A) distances indicate substantial C-N multiple bonding; C(l2) has strictly planar stereochemistry. The Os3cluster is an open triangle with the Os(l)-.Os(3) distance of 3.850 (1)A being nonbonding, and as expected from the 31Pshift (see also 2) the Os(l)-P-Os(3) angle of 105.0 (0)' is large. Careful IR and NMR monitoring of the reactions leading to 1 and 2 shows that attack by RNC on the acetylide has a very high regioselectivity. Indeed we have been unable to detect any products derived from attack a t C, of the acetylide. This regioselectivity and the facility of subsequent amination suggests that the exposed a-carbon atom in these multisite-bound acetylides is exceptionally electrophilic. Such electrophilicity and hence regioselectivity to nucleophilic attack should be open to exploitation in organometallic and organic synthesis.
Acknowledgment. We are grateful to NSERC (A.J.C.) and NATO (A.J.C. and E.S.) for financial support of this work.
(19) Bradley, J. S.; Ansell, G. B.; Hill, E. W. J. Am. Chem. SOC.1979, 101, 7417.
(20) Seyferth, D.; Williams, G. H.; Nivert, C. L. Inorg. Chem. 1977,16, 758. (21) Sievert, A. C.; Strickland, D. S.; Shapley, J. R.; Steinmetz, G. R.; Geoffroy, G. L. Organometallics 1982, 1, 214. (22) 3 Ir (C7Hs) v(C0) 2065 (m), 2039 (s), 2005 (m), 1994 (s), 1969 (m), 1957 (m), 1950 (m), 1924 (w), u(NH) 3419 (w), 3354 (w) cm-'; 'H NMR (CDzCl2-CHCl3)6 0.9-1.55 (m, CH2CH2CH3),1.35 (s, t-Bu), 3.10, 3.30 (m, CHZN),7.00-8.00 (m, Ph), 31PNMR (CD2ClZ-CHC1,) 6-72.5. (23) Crystals of O S ~ P O ~ N C are~ monoclinic ~ H ~ ~ of space group P2'/n with Q = 12.012 (5) A, b = 15.260 (6) A, c = 20.937 (7) A, 0 = 91.18 (3)O, V = 3837 (3) A3, Z = 4, p(calcd) 2.187 gcm-,, p(measd) 2.19 g . ~ m -F~ ,(OOO) = 2360, and p (Mo K a ) = 106.40 cm-'. A prismlike crystal was rounded to a sphere of diameter 0.11 mm for data collection. From a total of 4159 measured intensities collected out to 28 = 42.0' with graphite-monochromated Mo K a radiation (X = 0.71069A) and 8-28 scans on a Syntex P2, automatic diffractometer, 2875 reflections having I t 30(0 were considered as observed and used in the structure solution and refinement. Standard reflections monitored throughout the course of data collection varied in intensity by only 1 2 % . A spherical absorption correction lia(wR = 0.59) was applied to the observed data. The osmium and phosphorus atoms were located in a Patterson map and light atoms in subsequent Fourier syntheses. Refinement proceeded with isotropic temperature parameters to R = 0.059. With anisotropic coefficients for osmium and phosphorus and isotropic coefficient for C, N, and 0 atoms the final R and R , values were 0.040 and 0.046. Since the data crystal was of poorer quality than for the ruthenium complex and the diffraction data less precise, no effort was made to locate hydrogen atoms. A final difference map was however featureless, with maximum peak heights at the level of 1.2 e A3 in the vicinity of the osmium atoms.
Organometallics 1983,2, 355-356
355
Scheme I
Registry No. 1,82647-62-9; 2, 82647-60-7;3, 84081-57-2; (p-
H)RU~(CO),(~~-?’-C~CP~), 82647-61-8; OS~(CO),(~~-V’-CE CPh)(PPh,),82640-93-5; t-BuNC, 7188-38-7; n-BuNH,, 109-73-9; Ru,7440-18-8; OS, 7440-04-2. Supplementary Material Available: Table I, atomic positions, Table 11, anisotropic thermal parameters, Table 111, bond lengths and angles for (p-H)(Ru3(C0),[C(CN-t-Bu)CPh], Table IV, atomic positions and thermal parameters, Table V, bond ;N-lr-L lengths and angles for 0s3(CO),[C(C(NH-t-Bu)(NH-n-Bu))CPh](PPh’), and listings of structure factor amplitudes for both compounds (44 pages). Ordering information is given on any masthead page. of a number of rhodium and iridium amides which not only may be readily prepared in high yields as crystalline solids but are thermally stable under inert atmosphere, both in the solid state and in solution. In addition, some of these Amides of Rhodium and Irldlum Stabilized as Hybrld complexes show unusual catalytic hydrogenation behavior Multidentate Ligands with simple olefins under very mild reaction conditions. Reaction of LiN(SiMezCH,PPhz)2 with a variety of Mlchael D. Fryzuk’ and Patricia A. MacNeli rhodium precursors in cold toluene or ether solutions, Department of Chemistry, University of British Columbia followed by extraction with hexane, results in high yields Vancouver, British Columbia, Canada V6T 1Y6 of the rhodium(1) amido phosphines 1-5 (eq 3). All of Received August 24, 1982 these complexes are highly air- and moisture-sensitive crystalline solids; they are typically recrystallized from Summary: A variety of rhodium and iridium amido phoshexane at -30 “C to give analytically pure products in phine derivatives have been isolated and fully character7 0 4 0 % yields. ized. These complexes are exceptionally stable, a unique (Rh(CO)zC1)2 feature of group 8 transition-metal amides, owing to the (Rh(COE)2Cd2 fiPp“2 incorporation of the amido function as a part of a “hybrid” Me,Si I LiN(SiMe2CH2PPh2), + [Rh(C2H4),C112 ligand. The catalytic homogeneous hydrogenation activity :N-RhL Rh( PMe3)4+CI Me& I of these rhodium and iridium species has also been inRh(PPhJ,CI 2h: (3) vestigated. ~
Although amides of the.“hard” early transition metals are well-known, such complexes of the “soft” later metals are very rare. The paucity of amide derivatives of the group 8 metals may be ascribed to unfavorable hard/soft pair interactions as well as kinetic instability. Attempts to isolate rhodium alkylamides were owing to decomposition via @ elimination of the metal-amide bond (eq 1). The incorporation of a ligand having no RhC1(PPh3),
LiNMez
RhH(PPhJ3
+ CH2=NMe
(1)
@-hydrogensresulted in the synthesis of the first rhodium amide2 (eq 2). However, although this complex is stable RhC1(PPh3)3
LiN(SiMe&
Rh(PPh3)2N(SiMe3)2(2)
under inert atmospheres in the solid state, decomposition, with concomitant elimination of HN(SiMe3)2,occurs at 25 “C in benzene solution (tip = 12 h). We have previously described3 the use of the hybrid ligand strategy in the design of novel transition-metal amido phosphine complexes. The term “hybrid” refers to a ligand system that contains both “hard” and “soft” donors linked in a chelating manner. To date, we have used this approach to prepare amido phosphine derivatives of Ni(11),Pd(11),Pt(II),4,5 Zr(IV), and Hf(1V) illustrating the versatile coordinating ability of this ligand type. We now wish to report the isolation and characterization ,6y7
(1) Diamond, S. E.; Mares, F. J. Organomet. Chem. 1977,142,C55.
(2)Cetinkaya, B.; Lappert, M. F.; Torroni, S. J. Chem. Soc., Chem. Commun. 1979,843. (3)Fryzuk, M.D.; MacNeil, P. A. J.Am. Chem. SOC.1981,103,3592. (4)Fryzuk, M. D.; MacNeil, P. A. Organometallics 1982,1, 918. (5)Fryzuk, M. D.; MacNeil, P. A. Organometallics 1982, 1, 1540. (6)Frvzuk, M. D.; Rettig, S. J.; Williams, H. D., submitted for publication in Inorg. Chem. (7)Fryzuk, M. D.;Williams, H. D. Organometallics 1983,2, 162.
L:
1
2 3 4 5
co
cyclooctene C2H4
PMe, PPh,
In all of these complexes, the hybrid ligand is coordinated in a tridentate fashion, binding to the rhodium center through both phosphines and the amide nitrogen, resulting in a square-planar, 16-electron species. The exclusive trans disposition of the chelating phosphines was established by the presence of a virtual triplet8 for the CH2Pprotons at -1.8 ppm in the IH NMR (Japp y 5 Hz). Further support for this trans configuration was given by the the chemical shift difference of 0.6-1.0 ppm between the ortho and para/meta protons of the P-phenyl substituents, when the spectrum is recorded in deuterated aromatic solvent^.^ Deuteriobenzene solutions of these complexes, sealed in NMR tubes under nitrogen, show no decomposition, even after several months at 25 “C. The analogous iridium derivatives may be prepared in a similar manner or, more simply, via reaction of the iridium cyclooctene amide (6) with the desired neutral ligand at room temperature in toluene (Scheme I). In contrast to the previous preparation of the rhodium analogues, the solvent used in the synthesis of the iridium amides is crucial; when diethyl ether is employed, inseparable mixtures of products are formed whereas the use of toluene results in high yields of the pure complexes. Once again, the lH NMR spectra of these derivatives indicate that all are square-planar complexes with trans disposed phosphines. It should be noted that only one other iridium amide complex, Ir(C0D)(N(SiMe3),](PEt3), has been prepared to date.1° Rhodium and iridium amides have also been synthesized ~~
~~~
(8)Brookes, P.R.; Shaw, B. L. J. Chem. SOC.A 1967,1079. (9)Moore, D. S.;Robinson, S. D. Inorg. Chim. Acta 1981,53,L171.
0 1983 American Chemical Society
