Organometallics 1996, 14,245-250
245
Size-Selective Reactions of
~~~-MO(CO)~{P~~P(CH~CH~O),CH~CH~PP~~-P,P) (n = 4,5) Metallacrown Ethers with Mercury(I1) Salts. Crystal Structure of cis-Mo(C0)4{ - P h 2 P (CH2CH20)&H2CH2PPh2-P,P90,0’,0”,0”’, O””}*HgCl2, an Unusual Bimetallic Complex Containing a Molecular Cleft Gary M. Gray* and Christina H. Duffey Department of Chemistry, The University of Alabama at Birmingham, UAB Station, Birmingham, Alabama 35294 Received May 31, 1994@ The reactions of mercury(I1) salts with cis-Mo(CO)4{P~zP(CHZCHZO),CH~CHZPP~Z-P,P} (n = 5 (l),4 (2)) metallacrown ethers are surprisingly complex, and the product depends upon the size of the metallacrown ether ring and the anion in the mercury(I1) salt. The reaction of HgC12 and 1 gives the bimetallic metallacrown ether complex, cis-Mo(CO)4@P h ~ P ( C H ~ C H ~ O ) ~ C H ~ C H ~ P P h ~ - ~ , P , 0 , 0 ’ , 0 ” , 0 , 0 ”3, ” }because * H g C 1the ~ , metallacrown ether ring is sufficiently large to accommodate the Hg2+. “he X-ray crystal structure of 3 (triclinic space group Pi,a = 10.387(2)A, b = 13.0359(7)A, c = 17.710(3)A, a = 69.401(7)”, /3 = 81.32(1)”,y = 87.15(1)”;V = 2218.8 A3;Z = 2; R = 5.82; R, = 7.19; GOF = 1.996 for 497 parameters and 7737 out of 9505 unique reflections) has been determined. The coordination environment of the Hg2+is a hexagonal bipyramid with one missing equatorial ligand, axial chlorides, and equatorial ether oxygens. The open coordination site points toward the molybdenum, and the Mo-Hg distance is 6.8854(6) A. In contrast, the reaction of HgClz and 2 results in the isomerization of 2 to trans-Mo(CO)4{P~zP(CHZCHZO)~CHZCHZPP~ZP,P’}, 4. The Hg2+,which is too large to fit in the metallacrown ether ring in 2, catalyzes this isomerization, perhaps via coordination to the metallacrown ether and a lone pair on one of the carbonyl oxygens. Finally, the reaction of Hg(NO&H20 and 1 results in the oxidation of the molybdenum carbonyl complex and the formation of a Hg2+ complex of Ph2P(CH&H20)&H&H2PPh2. This mercury complex is not formed when Hg(N03)2*H20is stirred with PhzP(CHzCH20)5CHzCHzPPhzindicating that the metallacrown ether is required for the reaction to occur.
Introduction Metallacrown ethers are formed when RzPX(CH2(R = Ph, O-alkyl; X = -,0; n L 3) CHZO),CHZCH~XPRZ ligands chelate transition m e t a l ~ . l - These ~ complexes are of interest because they contain both a transition metal complex, which may catalyze a variety of organic reactions, and a crown ether, which may act as a phasetransfer catalyst. Studies of these metallacrown ethers have shown that they, like the crown ethers, are capable
* Abstract published in Advance ACS Abstracts, November 15,1994. (1)(a) Powell, J.; Kuksis, A.; May, C.J.; Nyberg, S.C.;Smith, S. J.
J.Am. Chem. SOC.1981,103,5941. (b)Powell, J.; Nyberg, S.C.;Smith, S. J. Znorg. Chim. Acta 1983,76, L75. (c) Powell, J.; Ng, K. S.;Ng, W. W.; Nyberg, S.C.J. Organomet. Chem. 1983,243,C1. (d) Powell, J.; Gregg, M.; Kuskis, A.; Meindl, P. J.Am. Chem. SOC.1983,105,1064.
(e) Powell, J.; Gregg, M. R.; Kuksis, A.; May, C. J.; Smith, S. J. Organometallics 1989,8,2918.(0Powell, J.; Kuskis, A.; May, C.J.; Meindl, P. E.; Smith, S.J. Organometallics 1989,8,2933. (g) Powell, J.; Gregg, M. R.; Meindl, P. E. Organometallics 1989,8, 2942. (h) Powell, J.; Lough, A.; Wang, F. Organometallics 1992,11, 2289. (2) (a) Alcock, N. W.; Brown, J. M.; Jeffery, J. C. J. Chem. SOC., Chem. Commun. 1974,829. (b) Alcock, N. W.; Brown, J. M.; Jeffery, J. C.J.Chem. Soc., Dalton Trans. 1976,583.(c) Thewissen, D. H. W.; Timmer, K.; Noltes, J. G.; Marsman, J. W.; Laine, R. M. Znorg. Chim. (d) Timmer, K.; Thewissen, D. H. W. Znorg. Chim. Acta 1985,97,143. Acta 1985,100,235.(e) Timmer, K., Thewissen, H. M. D.; Marsman, J. W. Recl. Trav. Chim. Pays-Bas 1988,107,248. (3)(a) Varshney, A.; Gray, G. M. Znorg. Chem. 1991,30,1748. (b) Varshney, A.;Webster, M. L.; Gray, G. M. Znorg. Chem. 1992,31,2580. (4)Gray, G. M.;Duffey, C. H. Organometallics, in press.
0276-7333/95/2314-0245$09.00fO
of coordinating alkali metal cations and that the stabilities of the resulting complexes depend upon the relative sizes of the cation and the metallacrown ether cavity.’~~ These studies have also shown that carbonyl ligands in metallacrown ether complexes are activated toward nucleophilic attack by organolithium reagents when the cavity is of the appropriate size to bind the Li+.l Little is known about the conformational changes that occur when these metallacrown ethers bind hard metal cations because no X-ray crystal structures of such complexes have been reported. In addition, nothing is known about the abilities of the metallacrown ether complexes to bind heavy metal cations such as Hg2+. In this paper, we report the results of a synthetic and NMR spectroscopic study of the reactions of Hg2+salts with metallacrown ethers of the type cis-Mo(COk(Ph2P(CH2CH20),CH2CH2PPh2-P$”}(n = 5 (1)or n = 4 (2)). We also report the X-ray crystal structure of cisM o ( C O ) ~Ph2P( { CH2CH20)5CH2CH2PPh2-P,P’,O, O , O , O , O } ~ H g C l3, ~ and , discuss the significance of this structure. Experimental Section All manipulations were carried out under a atmosphere of nitrogen. The solvents were of reagent grade and were used
0 1995 American Chemical Society
246 Organometallics, Vol. 14, No. 1, 1995
Gray and Duffey
Table 1. NMR Data for the Metallacrown Ethers and their HgClz Complexes 1 2 3 4 5 6 6 5 4 3 2
1 2 3 4 5 5 4 3 2 1
0
0
0
0
PPh2
P compd 1" 2" 36 46
56
6"
&31P)(ppm) 20.44 s 20.11 s 21.20 s 32.54 s 27.83 sd 20.11 s
Ph2P
c1 I'J(HgP)I (Hz)
9861
IJ(W(Hz) 13c
W3C) (ppm) 66.94 bs 67.71 bs 67.33 bs
27.37 d 31.22 aq
37d 15c
64.53 bs 67.57 aq
+ 3J(P'C)I.
0
0
c2
W3C) (ppm) 32.87 aq 31.32 aq 32.28 aq
Data from ref 3a. Data from this work. IIJ(PC)
1
nnnnnn
A A A A A Ph2P
2w
IIJ(PC)I. I2J(PC)
as received. Literature procedures were used to prepare cis-
IJ(PC)I (Hz)
9'
0
0
0
PPhp
C3-C6 W3C) (ppm) 69.96 s, 70.34 s, 70.47 s, 70.47 s 70.16 s, 70.25 s, 70.65 s 69.91 s, 69.91 s, 70.02 s, 70.07 s 70.00 s, 70.07 s, 70.07 s, 70.30 s 69.81 s, 69.99 s, 69.99 s, 69.99 s
+ 4J(P'C)I.
colorless to yellow to dark brown to beige and a beige solid
precipitated. The reaction mixture was then filtered, and the MO(CO)~{P~~P(CH~CH~O)~CH~CH~PP~~-P,P'} (n = 5 (l),4 filtrate evaporated t o dryness to yield 0.126 g of a foamy white solid, 5, which appeared to be a Hg(N03)~complex of the The 31P{1H},13C{'H}, and 'H NMR spectra were recorded P ~ ~ P ( C H ~ C H ~ O ) & H ~ Cligand HZ.PP on~ the ~ basis of its 31P on a GE NT-300, wide-bore, multinuclear NMR spectrometer. and NMR spectra. The 31PNMR spectra were referenced to external 85% phosphoric acid, and the I3C and 'H NMR spectra were referenced X-ray Structure Determination of 3. A colorless, needleto internal tetramethylsilane. Chemical shifts that are downlike crystal of 3 was grown by slowly diffusing hexanes into a field from those of the reference compounds are reported as THF solution of the complex. The crystal was mounted on a positive. The 31Pand aliphatic 13C NMR data for the comglass fiber with epoxy cement, and the cell constants were plexes are given in Table 1. Infrared spectra of dilute obtained from least-squares refinement of 25 reflections with dichloromethane solutions of the carbonyl complexes in a 0.2 25 5 8 5 35". All measurements were carried out at 23 "C on an Enraf-Nonius CAD4 diffractometer using graphite monomm KBr solution cell were run on a Nicolet IR44 FTIR spectrometer. The background for these measurements was chromated Cu Ka radiation (1= 1.5418 A). pure dichloromethane in the same cell. Elemental analyses Data were collected by 0-28 scans. The crystal decayed of the compounds were performed by Atlantic Microlab, Inc., 12.3%during the data collection, and a linear decay correction Norcross, GA. was applied. An analytical absorption correction (using the C ~ S - M O ( C O ) ~ { ~ - P ~ ~ P ( C H Z C H Z O ) ~ C H ~ C H ZCrystal P P ~ ~and - P , Abscor ~, programs) was also applied to the data. 0 , 0 , 0 , 0 , 0 } ~ H g C 13~ . ,A mixture of 0.176 g (0.213 mmol) Of the 9505 independent reflections measured, 7737 had Z > of 1and 0.301 g (1.11mmol) of HgCl2 in 3 mL of chloroform3 d n and were used for structure solution and refinement. dl was stirred at ambient temperature for 4 h and then filtered The structure was solved by heavy-atom methods and through diatomaceous earth. The filtrate was allowed to stand refined by a full-matrix least squares procedure that miniin the dark for 2 days and then refiltered. This filtrate was mized w(lFol- IFc1)2, where w = l/u2(Fo),using the MolEN evaporated to dryness to give a quantitative yield of crude package of programs. All non-hydrogen atoms were refined 3. Recrystallization from a dichloromethane-methanol mixanisotropically. The hydrogen atoms were placed in calculated ture yielded analytically pure 3. Anal. Calc (found) for positions (C-H = 0.96 A, UISO(H)= 1.3U1so(C))and were not C ~ ~ H U C ~ ~ H ~ OC, QM 58.11 O P(58.26); ~: H, 5.36 (5.42). 'H NMR refined. Data were weighted using a non-Poisson scheme. A (CDC13): 6 7.507 and 7.352 (Ph, m, 5H); 6 3.652 (C5 and C6 secondary extinction correction was applied to the data,5 and methylenes; m, 4H), 3.578 (C4 methylene; m, 2H), 3.405 (C3 the extinction coefficient was refined. In the last stage of the methylene; m, 2), 3.274 (C2 methylene, t, I3J(HH)l= 7.6 Hz, refinement no parameter varied by more than 0.01 of its 2H), 2.805 (C1methylene, t, I3J(HH)l= 7.6 Hz, 2H). IR [v(CO)l standard deviation, and the final difference Fourier map had (CH2C12): 2022 m, 1919 sh, 1909 s, 1886 sh cm-'. no interpretable peaks. Atomic scattering factors were taken Reaction of C ~ ~ - M O ( C ~ ) ~ { P ~ S ( C H ~ C H Z O ) ~ C H Zfrom C H ~the P ~compilations Zof Cromer and Weber: and those for H Pr}, 2, and HgClz. A mixture of 0.098 g (0.129 mmol) of 2 were taken from the ref 7. Corrections for anomalous disperand 0.170 g (0.626 mmol) of HgCl2 in 2.0 mL of chloroform-dl sion were taken from the compilations of Cromer and Lieberwas stirred in the dark at ambient temperature for 70 h. The mans and applied t o chlorine, mercury, molybdenum, and mixture was then filtered through a 0.2 pm syringe filter. The phosphorus. Data for the X-ray structure analyses are given residue was washed with two, 0.50 mL portions of chloroformin Table 2. Positional parameters are given in Table 3. Values dl, and these were also filtered through the syringe filter and of selected bond lengths and angles and torsion angles are combined with the reaction mixture. A quantitative 31PNMR given in Tables 4-6. Tables of hydrogen atomic positional and spectrum was taken of the filtrate. This spectrum contained thermal parameters, thermal parameters, torsion angles, and a singlet at 20.19 ppm due to 1 and a singlet at 32.54 ppm least squares planes are available as supplementary material. due to truns-Mo(CO)r{P~~P(CHZCH~O)&H~CHZPP~~-P,P'}, 4, An ORTEPQdrawing of the molecule is given in Figure 1. in a 46.3 to 53.7 ratio (from integration). Reaction of cis-Mo(CO)r(PhzPMe)z and HgC12. The Results and Discussion reaction of 0.078 g (0.129 mmol) of ci~-Mo(CO)4(PhzPMe)z and 0.170 g (0.626 mmol) of HgCl2 in 2.0 mL of chloroform-dl was carried out using the procedure described for the reaction of 2 Previous studies of cis-Mo(C0)4{Ph2P(CH2CH20)nand HgC12. A quantitative 31PNMR spectrum of the filtrate CH~CHZPP~~-P,F"} (n= 5 (1),4 (2)) metallacrown ethers contained a singlet at 15.44 ppm due to &-Mo(CO)*(Ph2PMe)2 have shown that 1 weakly coordinates to Li+ and and a singlet at 28.49 ppm due to trans-Mo(C0)4(PhzPMe)zin a 79.2 t o 20.8 ratio (from integration). ( 5 ) Zachariasen, W. H. Acta Crystallogr. 196.3, 16, 1139. Reaction of cis-Mo(CO)r{PhS(CH&H2O)~CHZCHPPhr (6) Cromer, D. T.; Waber, D. T. Acta Crystallogr. 1966,18, 104. (7) International Tables for Crystallography; Hahn,T., Ed.; The Pp},2, and Hg(NOs)z.HzO. A mixture 0.20 g (0.24 mmol) Kynoch Press: Birmingham, U.K., 1974; Vol. IV,p 72. of 1 and 0.425 g (1.24 mmol) of Hg(N03)2*H20in 25 mL of (8)Cromer, D.T.;Lieberman, D. J. J. Chem. Phys. 1970,53, 1891. dichloromethane was stirred at ambient temperature for 24 (9) Johnson, C. K. ORTEPZZ. Report ORNL-5138; Oak Ridge Nah. During this time, the color of the solution changed from tional Laboratory: Oak Ridge, TN, 1976. (2)).3a
Reactions of Metallacrown Ethers with Hg(II) Salts Table 2. Data Collection and Structure Solution and Refinement Parameters for 3 formula
Mw
p:G(A) b
c (A)
a (de@
B (deg)
Y (deg)
v (A31
Z dCdc(dcm3) cyst diamens (mm) h m u , hmjn
k m u , kmin
kdMn (“C)
C&&12HgMOOgPz
1098.18
P1 10.387(2) 13.0359(7) 17.710(3) 69.401(7) 81.32(1) 87.15(1) 2218.8 2 1.644 0.13x 0.17x 0.70 12,0 -16,16 -21,21 1.54184 23 111.825 0.1-74
Organometallics, Vol. 14, No. 1, 1995 247 Table 3. Positional Parameters and Isotropic Thermal Factors (Az)for J atom Hg Mo
c12 P1
P2 0 1
02 03 04 05 06 07 08
09
c1
c2 c3 c4 c5 linear c7 12.3 C8 analytical c9 38.46,5.83 c10 9505 c11 1.34 c12 7737 C13 497 C14 W(lF0 - I F C V C15 non-Poisson (w = l/u2(Fo)) C16 0.03 C17 Zachariesen C18 1.995x c19 5.82 c20 7.19 Rw (%) c21 GOF‘ 1.996 c22 max, min resid electron density (e/A3) 3.109,-0.175 C23 max shifuerror 0.01 C24 C25 C26 C27 C28 strongly coordinates to Na+ but that 2 strongly coordiC29 nates to Li+ and weakly coordinates to Na+.3a Because C30 C31 Na+ and Hg2+have similar ionic radii (for coordination C32 number 6: Na+, 1.16A, and Hg2+,1.16&,lo we expected c33 that 1 would strongly bind Hg2+but that 2 would not. c34 This picture, however, is much too simplistic. c35 Reaction of C ~ S - M O ( C O ) ~ ( P ~ ~ P ( C H ~ C H ~ O ) & C36 H~c37 CH2PPh2-PQ’}, 1, and HgC12. The reaction of 1 with C38 HgC12 in dichloromethane, shown in eq 1, yields only c39 C40 temp abs coeff (cm-’) 8 limits (deg) decay corr decay (%) abs corr Tmu. Trmn (%) reflns measd scan width (deg) reflns with I ?. 3u(Z) no. of variables function minimized weighting scheme instrumental uncertainty factor secondary extinction corr type minimized extinction coeff R (%)
X
0.33142(3) 0.06877(5) 0.1926(3) 0.2349(2) -0.0437(2) -0.1089(7) 0.2031(6) 0.2650(8) -0.1272(6) 0.4733(5) 0.5579(6) 0.4390(6) 0.1972(6) 0.0908(5) -0.0459(8) 0.1559(8) 0.1965(8) -0.0586(7) 0.3048(6) 0.5720(7) 0.6408(8)
0.620(1) 0.524(1) 0.347(1) 0.285(1) 0.144(1) 0.0356(9) -0.0070(7) 0.0604(7) 0.3782(6) 0.4751(7) 0.5794(7) 0.5911(8) 0.4929(9) 0.3868(8) 0.1971(6) 0.2902(7) 0.2567(9) 0.1272(9) 0.0344(8) 0.067l(7) -0.1229(7) -0.0794(8) -0.1314(9) -0.232( 1) -0.2784(9) -0.2265(7) -0.1699(6) -0.2795(7) -0.3655(7) -0.3459(8) -0.2363(8) -0.1481(7)
Y
Z
B
0.58858(2) 1.02894(4) 0.5003(2) 0.8943(1) 0.8863(1) 1.2231(5) 1.2104(4) 1.0859(7) 1.008l(5) 0.6686(4) 0.4760(4) 0.4195(4) 0.5082(4) 0.6996(4) 1.1481(6) 1.1436(6) 1.0624(6) 1.0103(6) 0.7905(5) 0.5960(6) 0.5518(6) 0.4190(7) 0.3504(7) 0.3626(6) 0.4404(7) 0.5944(7) 0.6459(7) 0.7501(6) 0.8144(6) 0.9720(5) 0.999l(6) 1.0632(6) 1.1027(6) 1.0796(6) 1.0159(6) 0.8094(5) 0.7704(6) 0.7040(7) 0.6773(7) 0.7121(6) 0.7771(6) 0.7764(5) 0.6706(6) 0.5952(7) 0.6245(8) 0.7294(7) 0.8065(6) 0.9352(5) 0.8745(6) 0.9109(7) 1.0109(7) 1.0691(7) 1.0338(6)
0.67593(2) 0.77377(3) 0.7910(1) 0.84785(9) 0.73701(9) 0.6893(4) 0.8132(4) 0.6102(4) 0.9345(4) 0.7860(3) 0.7473(3) 0.6315(3) 0.574l(3) 0.5990(3) 0.7190(5) 0.7994(4) 0.6689(5) 0.8778(4) 0.8039(4) 0.8189(4) 0.7565(5) 0.6959(5) 0.6834(5) 0.6077(5) 0.5420(5) 0.5139(5) 0.5544(5) 0.6389(4) 0.6780(4) 0.8445(4) 0.7775(4) 0.7712(5) 0.8320(6) 0.8980(4) 0.9052(4) 0.9555(4) 1.0073(4) 1.0877(4) 1.1186(5) 1.0688(5) 0.9876(4) 0.8255(4) 0.8522(5) 0.9262(5) 0.9754(5) 0.9490(5) 0.8753(4) 0.6700(4) 0.6776(4) 0.6205(4) 0.5570(5) 0.5493(4) 0.6052(4)
3.733(6) 2.576(9) 6.05(6) 2.62(3) 2.78(3) 7.0(2) 5.9(1) 8.3(2) 5.7(1) 3.5(1) 4.4(1) 4.8(1) 4.9(1) 3.8(1) 4.2(2) 3.9(2) 4.3(2) 3.6(1) 3.2(1) 3.8(1) 4.2(2) 5.4(2) 5.9(2) 5.3(2) 5.1(2) 5.1(2) 5.6(2) 4.1(2) 3.6(1) 2.9(1) 3.7(1) 4.5(2) 4.8(2) 4.7(2) 4.1(2) 3.0(1) 3.7(1) 4.4(2) 4.8(2) 4.5(2) 3.5(1) 3.2(1) 4.2(2) 5.5(2) 5.6(2) 4.9(2) 3.7(2) 3.1(1) 3.4(1) 4.3(2) 4.8(2) 4.5(2) 3.7(1)
Anisotropically refined atoms are given in the form of the isotropic equivalent displacement parameter defined as (4/3)[a2B(l,l) b2B(2,2) c2B(3,3)-t ab(cos y)B(1,2) ac(cos /3)B(1,3) bc(cos a)B(2,3)].
+
+
+
+
The shift in the 31PNMR resonance of 1 upon coordination of the HgClz is in the opposite direction and approximately twice as large as the shift that occurs I upon coordination of NaBPh, to 1 to form cis-Mo(CO)&Ph~P~CH~”~0)~CH~CH~PPh~-P,P’,O,O’,O’’,O”’, O}*NaBPh,, 6.3a The shifts in the methylene 13CNMR resonances of 1 upon coordination of the HgCl2 are in the same directions as those observed upon coordination of NaBPh, t o 1 but are of somewhat different magnitudes. These differences are not surprising given the different coordination geometries preferred by Hg2+and 3 Na+ and the flexibility of the metallacrown ether ring inH1. the bimetallic complex, C ~ ~ - M O ( C O ) ~ C ~ - P ~ ~ P ( C H ~ C ~O)~CH~CH~PPh~-P,P’,O,O,O,O,O}~HgCl2,3. This complex is quite stable in solution and can be recrystallized.
(10) (a) Shannon, R.; Prewitt, C. T.Acta Crystallogr. 1966,B25,925. (b) Shannon, R. Acta Crystallogr. 1976, A32, 751.
Gray and Duffey
248 Organometallics, Vol. 14, No. 1, 1995 Table 4. Selected Bond Lengths (A) for 3 Hg-Cl1 Hg-C12 Hg-05 Hg-06 Hg-07 Hg-08 Hg-09 Mo-P1 Mo-P2 Mo-C1 Mo-C2 Mo-C~ Mo-C4 P1-C5 P1-C17 Pl-C23 P2-Cl6 P2-C29 P2-C35 01-c1
2.281(2) 2.276(2) 3.085(6) 2.921(6) 2.727(6) 2.921(7) 3.078(5) 2.558(2) 2.557(2) 1.969(8) 1.999(9) 2.036(7) 2.046(7) 1.854(7) 1.823(7) 1.830(6) 1.842(8) 1.826(5) 1.84l(7) 1.16(1)
02-c2 03-C3 04-C4 05-C6 05-C7 06-C8 06-C9 07-C10 07-Cll 08-C12 08-C13 09-C14 09-C15 C5-C6 C7-C8 C9-C10 Cll-c12 C13-Cl4 C15-Cl6
c20
1.13(1) 1.12(1) 1.132(9) 1.434(9) 1.408(8) 1.41(1) 1.43(1) 1.42(1) 1.43(1) 1.43(1) 1.405(9) 1.42(1) 1.417(9) 1.484(9) 1.49(1) 1.46(2) 1.46(1) 1.50(1) 1.51(1)
Table 5. Selected Bond Angles (deg) for 3 Cll-Hg-C12 C11-Hg-05 C11-Hg-06 C11-Hg-07 C11-Hg-08 Cll-Hg-09 C12-Hg-05 C12-Hg-06 C12-Hg-07 C12-Hg-08 C12-Hg-09 05-Hg-06 06-Hg-07 07-Hg-08 08-Hg-09 P1-M0-n P1-Mo-C1 Pl-Mo-C2 Pl-Mo-C3 P1 -Mo-C4 P2-Mo-C 1 P2-Mo-C2 P2-Mo-C3 P2-Mo-C4
169.41(9) 88.5( 1) 92.4(1) 88.2(1) 92.4(1) 88.2(1) 86.1(1) 92.3(1) 102.4(1) 93.1(1) 87.4(1) 57.4( 1) 60.8(2) 61.4(2) 56.2(2) 94.57(5) 172.2(3) 86.7(2) 88.5(2) 94.1(2) 93.2(3) 178.4(2) 89.9(3) 94.5(2)
M0-Pl-U Mo-Pl-Cl7 Mo-Pl-C23 Mo-P2-C16 Mo-P2-C29 Mo-P2-C35 C6-05-C7 C8-06-C9 C10-07-Cll C12-08-C13 C14-09-C15 Pl-C5-C6 05-C6-C5 05-C7-C8 06-C8-C7 06-C9-C10 07-ClO-C9 07-Cll-C12 08-C12-Cll 08-Cl3-Cl4 09-Cl4-Cl3 09-Cl5-Cl6 P2-Cl6-Cl5
118.0(3) 102.6(3) 103.6(3) 102.6(3) 100.8(3) 103.6(3) 112.0(5) 113.1(6) 114.6(6) 113.7(6) 110.9(6) 117.9(5) 108.4(6) 109.8(6) 108.4(6) 109.4(8) 108.4(6) 109.3(7) 109.5(7) 108.9(6) 108.1(7) 107.6(6) 117.2(5)
c21
c19
c22
C36
c37-49c38
Figure 1. ORTEP drawing of the molecular structure of 3. Thermal ellipsoids are drawn at the 50% probability level, and hydrogens are omitted for clarity.
ring in 2 is sufficiently flexible that coordination of HgC12 does not greatly perturb the coordination environment of the molybdenum. The coordination environment of the Hg2+ ion is unusual. The Hg2+is coordinated to all five oxygens in the metallacrown ether and to both chlorides. The oxygens are in a nearly planar arrangement (largest deviations from the least squares plane through the five oxygens are 0.141(6)A for 0 7 and -0.107(6) A for 08). The chlorides are trans to each other, and the mercurychloride bonds are perpendicular to the least squares plane through the five ether oxygens. Because the 0-Hg-0 angles are all close to 60” and not 72”, the coordination environment of the Hg2+is better described as a hexagonal bipyramid with a missing equatorial ligand than as the more common pentagonal bipyramid. The open coordination site in the hexagonal bipyramid is pointed toward the molybdenum. This, together Table 6. Selected Torsional Angles (deg) for 3 and with the Mo-Hg bond distance of 6.8854(6)A, suggests Hg( CH~C~~0(C~~~H~0)&H~CH~-O,O’,O”,O”’,O’’’,O”’’)Cl~, 9 that it might be possible to bridge a ligand between the 3 9” metals in bimetallic,metallacrown ether complexes. One C3-01-C2-C1 -170 C7-05-C6-C5 -176.2(6) difficulty with this is that the protons on C5 and C16 C2-01-C3-C4 171 C6-05-C7-C8 -174.3(6) are pointed into the cavity between the Mo and the Hg C5-02-C4-C3 170 C9-06-C8-C7 -173.2(5) (distances (A): H5-Hl6, 2.719; H5-Hl6, 3.178; H5’C4-02-C5-C6 - 174 C8-06-C9-C10 -174.6(6) H16, 2.184; H5’-H16‘, 3.322) and would interfer with 174.4(7) C7-03-C6-C5 -176 Cl1-07-ClO-C9 a ligand bridging between the two metals. However, it -168.1(7) C6-03-C7-C8 - 179 C10-07-Cll-C12 172.9(8) C9-04-C8-C7 178 C13-08-Cl2-Cll seems likely that this could be avoided by rotation about 169.3(7) C8-04-C9-C10 177 C12-08-Cl3-Cl4 the Mo-P bonds. This occurs rapidly in solution as Cll-05-ClO-C9 -178 C15-09-Cl4-Cl3 180.0(6) indicated by the equivalence of the phenyl groups on -174.6(6) C10-05-Cll-Cl2 -80 Cl4-09-Cl5-Cl6 the phosphines and thus should not introduce a great -73.1(7) Ol-C3-C4-02 -77 05-C7-C8-06 7 1.9(8) 02-C5-C6-03 72 06-C9-C10-07 deal of strain into the molecule. -72.2(9) 03-C7-C8-04 -71 07-C11-C12-08 The asymmetric coordination environment of the Hg2+ 04-C9-C10-05 73 0 8 -C 13-C 14-09 68.2(8) ion in 3 is unlike that observed for Hg2+coordinated to Data from ref 14b. crown ethers and azacrown ethers. With larger crown ethers such as 1,4,10,13-tetraoxa-7,16-diazacyclooctaThe X-ray crystal structure of 3 is shown in Figure 1 decane and 18-crown-6, the Hg2+ coordinates in the and contains a number of interesting features. The center of the crown with the ether oxygens symcoordinationgeometry of the molybdenum is a distorted metrically arranged around the Hg2+ and with trans octahedron similar to that observed in other cis-Momonodentate anionic 1igands.ll With smaller crown (CO)1(P-donor 1igand)z complexes. The Pl-Mo-P2 ethers such as 15-crown-5,the Hg2+is too small to fit angle (94.57(5)”) is similar to those in cis-Mo(CO)r{Ph2P(CH2CH20)3CH2CH2PPh2-P,P}, 7 (93.78(2)0),3a (a) Malmsten, L.-A.Acta Crystallogr. 1979,B35,1702.(b)Paige, and c ~ s - P ~ C ~ ~ { P ~ ~ P ( C H ~ C H ~ O ) ~ C H8~ C H C. ~ (11) P PRichardson, ~ ~ - P ,M.P F. }, R.; Can. J.Chem. 1984,62,332. (c) Drew, M. G . B.; Lee, K. C.; Mok, K. F. Znorg. Chim.Acta 1989,155, 39. (99.03(6)0).3b This suggests that the metallacrown ether
Reactions of Metallacrown Ethers with Hg(II) Salts into the crown and coordinates above the crown with cis monodentate anionic ligands.12 Very similar behavior is also observed in Pb2+ crown ethers ~omp1exes.l~ The Hg2+ coordination environment in 3 closely resembles that in complexes with linear ethylene oxide 01igomers.l~This resemblance is seen in the similarity of the torsion angles for equivalent bonds in 3 and in
Organometallics, Vol. 14, No. 1, 1995 249 nism is similar, in many respects, to the mechanism suggested by Powell for the activation of carbonyls to attack by alkyl- and aryllithiums in related metallacrown ethers.‘
Reaction of c~s-Mo(CO)~{P~~P(CH~CH~O)&H~ CHzPPh2-PQ’), 2, and Hg(NOs)a*HaO. In an attempt to synthesize a Hg2+ complex with less strongly coor-
Hg(CH~CH~0(CH~CH~0)~CH~CH~-O,O,O’,0,0”’’)dinating anions, Hg(N03)2-H20was added to a dichloCl2, 9, shown in Table 6. The only major difference in romethane solution of 1. This caused the color of the these angles is between that for C14-09-Cl5-Cl6 in solution to change from colorless to deep brown and 3 and that for C10-05-Cll-C12 in 9, and this is t o finally to beige and a beige solid to precipitate from the be expected because the polyether is cyclic in 3 and solution. A 31PNMR spectrum of the methylene chloacyclic in 9. This striking similarity in torsion angles ride soluble portion of the reaction mixture contained a suggests that presence of the large transition metal single resonance that was a superimposed singlet and complex in the ring allows metallacrown ethers to adopt doublet. The relative intensities of the singlet and a larger variety of coordination modes than can the doublet and magnitude of the coupling constant indicrown ethers and therefore resemble the open chain cated that the diphenylphosphino groups in the polyethers in this regard. PhzP(CH&H20)5CH&H2PPhz ligand were coordinated Reaction of c~s-Mo(CO)~(P~~P(CH~CH~O)~CH~to mercury. This suggests that the nitrate oxidized the CH2PPh2-PQ’}, 2, and HgCl2. In contrast to the molybdenum, hence the color change, allowing the above results, when a chloroform-dl solution of 2 is diphenylphosphino groups of the PhzP(CHzCH20)5CHzstirred with excess HgC12 in the dark at ambient CH2PPh2 ligand to cooordinate to the mercury, as shown temperature, truns-Mo(C0)4{P ~ ~ P ( C H ~ C H ~ O ~ C H Z C in H Zeq- 3. The formulation for the product is supported PPhz-PQ’}, 4, is formed, as shown in eq 2. This P O ?
2
4
isomerization is 53.7% complete after 70 h in the presence of HgClz but does not occur to any appreciable extent during this time if HgC12 is not present. We recently reported that this reaction occurs very slowly in the dark (15% isomerization after 24 days at 5 “C) and rapidly when 1 is irradiated with W light (12 min a t 21 “ 0 . 4 In order to better understand the mechanism of this isomerization, we carried out a similar isomerization of cis-Mo(CO)4(Ph2PMe)~to trans-Mo(C0)4(PhzPMe)~in chloroform-dl solution in the presence of HgC12. This isomerization also occurs but at a much lower rate than the isomerization of 2 t o 4. This suggests that the Hgz+ facilitates the loss of the carbonyl by binding t o the lone pair on the oxygen and weakening the metal carbon bonds as demonstrated by Shriver with a variety of Lewis acids and metal carbonyl ~omp1exes.l~The increased rate of the isomerization of 2 to 4 by HgClz could result from initial binding of the HgC12 to the metallacrown ether in 2 followed by coordination of a carbonyl oxygen to the Hg2+. The crystal structure of cis-Mo(CO)4(pu-Ph2P(CHzCHzO)sCHzCHzPPhz-P,P’, 0,O,0”,0”’,O}.HgC1~,3, discussed above, suggests that bridging of a carbonyl between the Mo and the Hg2+ in these complexes is possible. The proposed mecha(12)Byriel, K. A.;Dunster, K. R.; Gahan, L. R.; Kennard, C. H. L.; Latten, J. L. Inorg. Chim. Acta 1992,196,35. (13)Byriel, K. A.;Dunster, K. R.; Gahan, L. R.; Kennard, C. H. L.; Latten, J. L. Swann, I. L. Polyhedron 1992,10,1205. (14)(a) Iwamoto, R. Bull. Chem. Soc. Jpn. 1973, 46, 1115. (b) Iwamoto, R.Bull. Chem. Soc. Jpn. 1973,46,1115. (c) Iwamoto, R.Bull. Chem. SOC.Jpn. 1973,46,1123. (15)Shriver, D. F.J. Orgunomet. Chem. 1975,94,25and references therein.
by the presence of resonances for all the ligand carbons and the absence of carbonyl resonances in its 13CNMR spectrum and by the absence of CEO stretches in its IR spectrum. This formulation is also supported by the fact that no reaction is observed when the PhzP(CH2CH20)5CH2CH2PPh2ligand is stirred with Hg(N03)2.H20 in dichloromethane, indicating that the metallacrown ether is needed as a template for this reaction t o occur. The only problem with this explanation is that all of the 13C NMR resonances of the Ph2P(CH2CH20)5CH2CH2PPh2 ligand appear to be doublets, suggesting that only one phosphorus is coordinated to each Hg2+. However, these doublets could also result if lZJ(PP)lis small, which would be the case if the complex is fluxional. Unfortunately, we have been unable to either purify or crystallize this material to prove the exact nature of the product.
Conclusions The reactions of Hg2+ salts with the cis-Mo(C0)4-
{P~~P(CHZCH~O),CH~CH~PP~~-PJ”} (n = 4,5) metallacrown ethers are surprisingly complex. The nature of the product depends on the the size of the metallacrown ether and the reactivity of the anions. The sizeselective reactions of the metallacrown ethers with Hg2+ are particularly fascinating because it might be possible to employ them in sensors for Hg2+and related anions. The coordination environment of the Hg2+ in cis-
Mo(C~)~{~-P~~P(CH~CH~O)~CH~CH~PP 0 , O , O , O , O } ~ H g Cisl ~a hexagonal bipyramid with
Gray and Duffey
250 Organometallics, Vol. 14, No. 1, 1995
an empty equatorial site pointing toward the molybdenum. This is quite interesting because it suggests that is should be possible to bridge a bifunctional ligand, such as carbon monoxide or carbon dioxide, between the two metals in these complexes. This type of bridging may be the reason that HgC12 catalyzes the isomerization of c ~ s - M o ( C O )Ph2P(CH2CH20)4CH2CH2PPh2P,P'} ~{ much more rapidly than it does the isomerization of cisMo(CO)r(PhzPMe)z. In bimetallic metallacrown ethers containing Pt-group metal complexes, such bridging
could give rise to catalytic activities and selectivities that are quite different from those of monometallic Ptgroup metal complex catalysts. Supplementary Material Available: Tables listing positional and thermal parameters for hydrogens, temperature factors, bond lengths, bond angles, torsion angles, and least squares planes for 3 (10pages). Ordering information is given on any current masthead page.
OM940409V
