4034
Organometallics 1996, 14, 4034-4036
Synthesis, Photophysics, Ion-Binding Studies, and Structural Characterization of Organometallic Rhenium(1)Crown Complexes Vivian Wing-Wah Yam,* Keith Man-Chung Wong, Vicky Wing-Man Lee, Kenneth Kam-Wing Lo, and Kung-Kai Cheung Department of Chemistry, The University of Hong Kong, Pokfilam Road, Hong Kong Received May 9, 1995@ Chart 1
Summary: A series of Re(I) complexes of [Re(L)(CO)&Il (1, L = LI = N-(2-pyridinylmethylene)-2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13benzopentaoxacyclononadecan16-ylamine; 2, L = LZ = N-(2-pyridinylmethylene)phenylamine) and [Re(phen)(CO)&C')l+ (3,L' = L3 = 1-(4-pyridinylformyl)aza-15-crown-5; 4, L' = Lq = 4-(N,Ndiethy1formamido)pyridine) have been synthesized and their photophysical and cation binding properties studied. The X-ray crystal structure of 3 has also been determined. There has been a growing interest in the study of host-guest interactions, in particular a revival of interest in the crown ethers and related inclusion compounds owing to the recent developments in molecular recognition studies and the design of molecular switches and probes.1,2 Although there have been numerous reports on the metal-to-ligand charge transfer (MLCT) excited state chemistry of rhenium(1) d i i m i n e ~their , ~ potential as metal ion probes, unlike the case for their ruthenium(11) analogues, has been relatively unexplored. Although there has been a report on the synthesis of rhenium(1) crown compound^,^ there has been, to the best of our knowledge, no application of this class of compounds in ion-binding studies. In this communication, we report the synthesis, photophysics, and first cation-binding properties of a series of rhenium(1)crown complexes. The first crystal structure characterization of a rhenium(1) crown complex will also be described. Reaction of Re(C0)sCl with L1 in benzene at reflux under a nitrogen atmosphere followed by addition of petroleum ether produced [Re(Ll)(CO)&l] (1) in high @Abstractpublished in Advance ACS Abstracts, August 15, 1995. (1)See for example: (a) Cooper, S. R. Crown Compounds: Toward Future Applications; VCH: New York, 1992. (b) Gokel, G. Crown Ethers and Cryptands. In Monographs in Supramolecular Chemistry; Stoddart, J. F., Ed.; Royal Society of Chemistry: Cambridge, U.K., 1991. ( c )Cram, D. J.; Cram, J. M. Container Molecules and Their Guests. In Monographs in Supramolecular Chemistry; Stoddart, J. F., Ed.; Royal Society of Chemistry: Cambridge, U.K., 1994. (d) Atwood, J. L.; Davies, J. E. D.; MacNicol, D. D. Inclusion Compounds: Key Organic Host Systems; Oxford University Press: New York, 1991; Vol. 4. (e) Vogtle, F.Supramolecular Chemistry; Wiley: Chichester, U.K., 1993. (2)See for example: (a) Pullman, A. Chem. Reu. 1991,91, 793. (b) de Silva, P. A,; de Silva, S. A. J . Chem. Soc., Chem. Commun. 1986, 1709. (c) Beer, P. D. Chem. SOC.Reu. 1989,18, 409. (d) Beer, P. D. Adu. Inorg. Chem. 1992,39, 79. (e) Anson, C. E.; Creaser, C. S.; Stephenson, G. R. J . Chem. SOC.,Chem. Commun. 1994,2175.(0 Yam, V. W.-W.; Lo, K. K.-W.; Cheung, K.-K. Inorg. Chem. 1995,34, 4013. ( g ) Todd, M. D.; Dong, Y.; Horney, J.; Yoon, D. I.; Hupp, J. T. Inorg. Chem. 1993,32,2001. (3)See for example: (a) Horvath, 0.; Stevenson, K. L. Charge Transfer Photochemistry of Coordination Compounds; VCH: New York, 1993. (b) Balzani, V.; Scandola, F. Supramolecular Photochemistry; Ellis Horwood: Chichester, U.K., 1991. (c) Wrighton, M. S.; Morse, D. L. J . A m . Chem. SOC.1974,96, 998. (d) Tapolsky, G.;Duesing, R.; Meyer, T. J. Inorg. Chem. 1990,29,2285. (e) Shaw, J. R.; Schmehl, R. H. J . A m . Chem. SOC.1991,113, 389. (0 Lin, R.;Fu, Y.; Brock, C. P.; Guarr, T. F. Inorg. Chem. 1992,31, 4346. (g)Dominey, R. N.; Hauser, B.; Hubbard, J.; Dunham, J. Inorg. Chem. 1991,30, 4754. (4) Yoon, D. I.; Berg-Brennan, C. A,; Lu, H.; Hupp, J. T. Inorg. Chem. 1992,31, 3192.
L2
/ OH"/\
\
L3
L4
yield. Similar reaction with LZ gave the non-crown analogue [Re(L2)(CO)&lI W 3 g On the other hand, reaction of [Re(phen)(CO)3(MeCN)lOTfwith L3 in THF at reflux under a nitrogen atmosphere afforded [Re(phen)(CO)3(L3)1+(31,isolated as the PFs- salt. Similar reaction with Lq gave the non-crown analogue [Re(phen)(CO)3(L4)IPFs(4). All newly synthesized complexes gave satisfactory elemental analyses and were characterized by 'H NMR spectroscopy and positive FAB-MS.5 The crystal structure of 3 has been determined by X-ray crystallography.6 A perspective drawing of the cation of 3 with atomic numbering is depicted in Figure 1. The coordination geometry at the Re atom is a distorted octahedron with the three carbonyl ligands arranged in a facial fashion. The trans angles subtended by the Re atom and the two coordinated atoms trans to each other are in the range 172.0(9)-176(1)", showing a slight deviation from an ideal octahedral geometry. The Re-C-0 bond angles of 170(2)-177(2)" are slightly distorted from linearity. The N(l)-Re-N(2) bond angle (74.9(7)"),exceptionally smaller than go", is a consequence of the steric requirement of the chelatin phen ligand. The Re-C(l) bond distance of 1.76(3) f i s shorter than the Re-C bonds (1.90(3)A) cis to the pyridyl unit bearing the crown. This is also in line with the longer C(1)-0(1)bond distance (1.27(3) A) relative to C(2)-0(2) and C(3)-0(3) (1.16(3) and 1.18(3) A). This is understandable, given the poor n-accepting ability of the pyridine ligand trans to the C(1) atom, which would enhance the Re-C(l) metal to ligand n back-bonding. On the other hand, 1 , l O phenanthroline is a better n-acceptor ligand. Similar observations have been reported in related Re(1) The amido carbon atom C(21) is sp2-
0276-733319512314-4034$09.00/0 0 1995 American Chemical Society
Organometallics, Vol. 14,No.9, 1995 4035
Communications
I
I
I
I
100
4ao
IW
OW
ilnm
Figure 2. Electronic absorption spectrum of 1 in anhydrous methanol (106.8 pM)upon addition of Ba(C10&. The insert shows a plot of Ad(Ao - A) versus the reciprocal of [Ba2+]. The absorbance was monitored at I = 410 nm.
01
Figure 1. Perspective drawing of the complex cation of 3 with atomic numbering scheme. Thermal ellipsoids are shown at the 25%probability level. Selected bond lengths (A) and angles (deg): Re(l)-N(l), 2.19(2);Re(l)-N(2), 2.18(2); Re(l)-N(3), 2.17(2); Re(l)-C(l), 1.76(3);Re(l)-C(2), 1.90(3);Re(l)-C(3), 1.90(3);C(l)-O(l), 1.27(3);C(2)-0(2), 1,16(3);C(3)-0(3), 1.18(3);C(21)-0(4), 1.25(3);N(l)-Re(l)-N(Z), 74.9(7);N(l)-Re(l)-N(3), 82.4(7);N(l)-Re(l)C(1), lOO(1); N(1)-Re( l)-C(Z), 172.0(9);N(l)-Re(l)-C(3), 101.2(9);N(Z)-Re(l)-N(3), 84.5(7);NG!)-Re(l)-C(l), 98(1); N(2)-Re( l)-C(Z), 98.1(9);N(Z)-Re(l)-C(3), 175.5(9); N(3)-Re(l)-C(l), 176(1);N(3)-Re(l)-C(2), 9329); N(3)Re(1)-C(3), 92.9(9);C(l)-Re(l)-C(Z), 84(1);C(1)-Re( 1)C(3),84(1);C(Z)-Re(l)-C(3), 85(1);Re(l)-C(l)-O(l), 170(2); Re(l)-C(2)-0(2), 176(2); Re(l)-C(3)-0(3), 177(2); 0(4)-C(21)-N(4), 122(2);0(4)-C(21)-C(18), 116(2);N(4)C(21)-C(18), 121(2). hybridized with bond angles subtended at C(21) typical of sp2 hybridization (116(2)-122(2)"). I t is interesting to note that the C(1)-0(1) bond distance is similar to C(21)-0(4) (1.25(3) A), approaching that for a C-0 double bond. All other bond distances and angles have typical values. (5) 1: lH NMR (270 MHz, CDCl3,298 K, relative to TMS) 6 3.7-4.2 (m, 16H, -0CHz-), 6.9 (d, lH, aryl H meta to -N=CH), 7.1 (dd, l H , aryl H ortho to -N=CH), 7.2 (d, l H , aryl H ortho to -0CHz and -N=CH), 7.6 (m, l H , pyridyl HI, 8.0 (d, 1H, pyridyl HI, 8.1 (td, 1H, pyridyl H), 8.8 (s, l H , -CH=N), 9.0 (d, l H , pyridyl H ortho to N); IR (Nujol mull, KBr, cm-'1 u(C10) 2017 (s), 1913 (SI, 1895 (s); positive FAB-MS ion clusters at mlz 677 {M}+, 642 {M - Cl}+; UV-vis (Ilnm (€,,/dm3 mol-' cm-l)) MeOH, 274 (15 985) and 399 (91501, CHzClz, 275 (15 145) and 414 (8675). Anal. Found: C, 40.4; H, 3.8; N, 4.1. Calcd for 1: C, 40.7; H, 3.5; N, 4.1. 2: 'H NMR (270 MHz, CDC13, 298 K, relative to TMS) d 7.5 (m, 5H, aryl Hs), 7.7-8.1 (m, 3H, pyridyl Hs), 8.8 (s, l H , -CH-N), 9.1 (m, l H , pyridyl H ortho to N); IR (Nujol mull, KBr, cm-1) v(C10) 2023 (s), 1919 (SI, 1884 (s); positive FAB-MS ion clusters at mlz 487 {M}+,459 {M - CO}+, 452 {M - C1}+; W-vis (Ilnm (cmax/dm3mol-l cm-'1) MeOH, 264 sh (92701, 313 (90501, and 410 (3715). Anal. Found: C, 37.3; H, 1.6; N, 6.1. Calcd for 2: C, 36.9; H, 2.1; N, 5.7. 3:lH NMR (270 MHz, acetone-&, 298 K, relative to TMS) d 3.3-3.7 (m, 20H, crown protons), 7.4 (dd, 2H, pyridyl H's), 8.4 (m, 4H, phen Hs), 8.7 (dd, 2H, pyridyl H's), 9.1 (dd, 2H, phen Hs), 9.9 (dd, 2H, phen H's); IR (Nujol mull, KBr, cm-') Y(CE0) 2028 (SI, 1939 (s), and 1926 (s), u(C=O) 1637 (s); positive FAB-MS ion clusters at m/z 774 {M}+, 746 {M - CO}', 450 {M - L3}+, 422 {M - L3 - CO}+; UV-vis (Ilnm (cmaXldm3 mol-' cm-')) MeOH, 275 (28 2101, 326 sh (7300), and 370 sh (3590). Anal. Found: C, 40.3; H, 3.3; N, 6.1. Calcd for 3: C, 40.5; H, 3.5; N, 6.1. 4: 1H NMR (270 MHz, CDzClz, 298 K, relative to TMS) 6 1.0 (t, 3H, -CH3), 1.1 (t, 3H, -CH3), 3.0 (9, 2H, -NCH2), 3.4 (q, 2H, -NCH*), 7.2 (dd, 2H, pyridyl Hs), 8.1 (dd, 2H, phen Hs), 8.2 (dd, 2H, phen Hs), 8.3 (dd, 2H, pyridyl Hs), 8.8 (dd, 2H, phen H's), 9.6 (dd, 2H, phen Hs); IR (Nujol mull, KBr, cm-') u(CEO) 2034 (s), 1928 (s), and 1909 (s), v(C=O) 1641 (SI; positive FABMS ion clusters at mlz 628 {M}-, 600 {M - CO}+, 450 {M - L4}+, 422 {M - L4 - CO}+; UV-vis (Ilnm (c,,ddm3 mol-' cm-')) MeOH, 275 (30 220), 327 sh (73451, and 369 sh (4005). Anal. Found: C, 39.0; H, 2.7; N, 6.9. Calcd for 4: C, 38.8; H, 2.9; N, 7.2.
Table 1. Photophysical Data for Complexes 1-4 complex medium ( T K ) L l n m (sdus) solid (298) solid (77) CHzClz (298) solid (298) solid (77) CHzClz (298) solid (298) solid (77) MeOH (298) solid (298) solid (77) MeOH (298)
665 633,691 717 (
