Hidai et al.
/ Mo(CO)(N~)(P~~PCH~CH~PP~~)~.~/~C~H~
H. M. Pohlit, T. H. Lin, W. R. Erwin, and R. M. Lemmon. J. Am. Chem. SOC., 91, 5421 (1969); J. Phys. Chem., 75, 2555 (1971). G. M. Jenkins and D . R . Wiles, J. Chem. Soc., Chem. Commun., 1177 (1972). H. D. Hagstrum, Phys. Rev., 96, 336 (1954); 150, 495 (1966); 119, 940 (1960); Surf. Scl., 54, 197 (1976); Metals, 6, 309 (1972). H. D. Hagstrum. Phys. Rev., 122, 83 (1961). H. F. Winters and D . E. Horne, Surf. Sci., 24, 587 (1971); H. F. Winters, J. Appl. Phys., 43, 4809 (1972); H. F. Winters and P. Sigmund, ibid., 45, 4760 (1974). G. M. Lancaster, J. A. Taylor, A. Ignatiev, and J. W. Rabalais, J. Electron Spectrosc. Relat. Phenom., in press. F. R. McFeely, S. P. Kowalezyk, L. Ley, R . G. Cavel, R. A. Poliak, and D. A. Shirley, Phys. Rev., 9, 5268 (1974). C. R. Ginnard and W. M. Riggs, Anal. Chem., 44, 1310 (1972). R. F. Willis, B. Fitton, and G. S. Painter, Phys. Rev. Sect. 6, 9, 1926
4441
(1974). (18) P. M. Williams, D . Latham, and J. Wood, J. Electron Spectrosc. Relat. Phenom, 7 , 2 8 1 (1975). A. M. Bradshaw and U. Krause, Verlag Chem., 1095 (1975). G. Henning, J. Chem. Phys., 19, 922 (1951); M. L. Dzurus and G. R. Henning, J. Am. Chem. SOC., 9, 1051 (1957); G. Henning, J. Chem. fhys., 20, 1438 (1952); H. Selig, P. K. Gallagher, and L. B. Ebert, inorg. Nucl. Chem. Lett., 13,427 (1977); M. E. Vol'pin, Yu. N. Nivokov, N. D. Lapkina, V. I. Kasatochkin, Yu. T. Struckhov, M. E. Kazahov. R. A. Stukan, V. A. Povitskij, Yu. S. Karimov, and A. V. Zuarikina. J. Am. Chem. SOC., 97, 3366 (1975). V. Franchetti, B.H. Solka, W. E. Baitinger, J. W. Amy, and R. G. Cooks, Int. J. Mass. Spectrom. /on Phys., 23, 29 (1977). The projected range is defined as the mean penetration depth for ions traveling normal to the surface; see P. D. Townsend, J. C. Kelly, and M. E. W. Hartley, "Ion Implantation, Sputtering, and Their Applications", Academic Press, New York, N.Y., 1976.
Preparation and Properties of Dinitrogen-Molybdenum Complexes. 6. Syntheses and Molecular Structures of a Five-Coordinate Mo(0) Complex M o ( C O ) ( P ~ ~ P C H ~ C H and ~ P Pa ~ ~ ) ~ Related Six-Coordinate Complex MO( CO)( N2)(Ph2PCH2CH2PPh2)2*V$C6H6 Maki Sato,2aTakashi Tatsumi,2a Teruyuki Kodama,2aMasanobu Hidai,*2a Tokiko Uchida,2band Yasuzo UchidaZa Contribution f r o m the Department of Industrial Chemistry, Faculty of Engineering, Uniuersity of Tokyo, Hongo, Tokyo 113, Japan, and Department of Industrial Chemistry, Faculty of Science and Technology, Science Unicersity of Tokyo, Noda, Chiba 278, Japan. Receiued January 24, 1977
Abstract: The reaction of trans-Mo(N2)2(dpe)2 (dpe = PhzPCH2CH2PPh2) with benzyl propionate at reflux in benzene under dinitrogen yielded tr~ns-Mo(CO)(N2)(dpe)2.~/2C6H6. On bubbling argon gas into a solution of the latter complex, a stable five-coordinate complex Mo(CO)(dpe)z was obtained and this reaction was reversible. The structures of those two complexes have been determined from three-dimensional x-ray counter data. The complex Mo(CO)(dpe)z crystallizes in the monoclinic system with the space group P21/n, with the following cell dimensions: a = 17.849 (3). b = 24.295 (4), c = 10.939 (2) A; p = 99.1 17 (4)O, V = 4683.5 (13) A3, and Z = 4. The molybdenum atom has square-pyramidal coordination with four phosphorus atoms as a basal plane and an axial linear carbonyl ligand (average Mo-P = 2.452 (2) A, Mo-C = 1.903 (9) A, and C - 0 = 1.192 ( 1 2) A). The nearest hydrogen is 2.98 ( 1 1) A from molybdenum, suggesting van der Waals contact of the ortho hydrogen atom of one of the dpe phenyl groups with the metal. The complex Mo(CO)(Nz)(dpe)2.'/2C6H6 crystallizes in the monoclinic system with the space group C2/c, with the following cell dimensions: a = 48.50 ( 6 ) ,b = 11.07 ( I ) , c = 18.25 (2) A: p = 97.98 (3)O, V = 9699 (22) A3, and Z = 8. The molybdenum atom has octahedral coordination with average Mo-P = 2.448 (4) A, Mo-C = 1.973 (16) A, Mo-N = 2.068 ( 1 2) A, C - 0 = 1.1 27 (20) A, and N - h = 1.087 ( 1 8) A. Bond distances in two complexes are compared and discussed.
In a previous c o m m ~ n i c a t i o n ,we ~ briefly reported that a stable five-coordinate Mo(0) complex, Mo(CO)(dpe)Z (dpe = Ph2PCH2CH2PPh2) ( I ) , was obtained on bubbling argon gas into a benzene solution of trans-Mo(CO)(N2)(dpe)2. ]/2C6H6 (2) and this reaction was reversible. Since structural information on metal sites which have the capacity to bind dinitrogen as a ligand is strongly desirable, it seems of special interest to determine the molecular structure of 1. Furthermore, the five-coordinate M(0) complexes (M = Cr, Mo, or W ) are frequently postulated as the intermediates in Sy1 processes of six-coordinate group 6 metal complexes4 and the structures of such species have been extensively studied by trapping them in low-temperature solid mat rice^.^ Although a few examples of five-coordinate d6 complexes of Ru(I1) and Rh(II1) have been established by x-ray diffraction studies,6 none is, to the best of our knowledge, known for group 6 transition metal complexes.' W e wish here to report the synthesis 0002-7863/78/1500-4447$01 .OO/O
and the molecular structure of the first example of a stable five-coordinate d6 molybdenum complex 1, as well as of the dinitrogen complex 2.
Experimental Section All reactions were carried out under an atmosphere of pure dinitrogen or argon using purified dioxygen-free solvents and standard Schlenk-tube techniques. The complex trans- M o ( N ~ ) ~ ( d p e )was z prepared by the published method.8 Infrared spectra were recorded from KBr pellets using a Nihon-bunko IRA1 double-beam spectrometer. Preparation of trans-Mo(COXNzXdpe)2.l/zC6H6 (2). Method A. Dimethylformamide (DMF) (19.0 g, 0.26 mol) was added to a solution of trans-Mo(N2)2(dpe)2 (2.0 g, 2.1 mmol) in benzene (80 mL) under dinitrogen. The mixture was heated under reflux for 20 min, during which the orange solution had become dark red. After cooling, n-hexane (100 mL) was added and the precipitate formed was filtered off, washed with ether and n-hexane, and dried in vacuo to yield dark
0 1978 American Chemical Societj
4448
Journal of t h e A m e r i c a n Chemical S o c i e t y
Table 1. Summary of Crystal Data compd formula formula wt a, A
b, 8, C.
A
density, g/cm3 (calcd) systematic absences space group F(000) crystal dimensions cm-I maximum absorption effects
p,
/
100:14
Table 11. Summary of Intensity Collection and Refinement
Mo(CO)(dpe)z Mo(CO)(dPe)2 C53H480P4MO 920.8 1 17.849 (3) 24.295 (4) 10.939 (2) 99.117 (4) 4683.5 (13) 4 1.31 hOl, h I odd OkO, k odd
+
P21ln
1904 0.3 X 0.3 X 0.7 mm 4.5 27%
/ July 5, 1978
987.88 48.50, (6) 11.07 (1) 18.25 (2) 97.98 (3) 9699 (22) 8 1.35 khl, h k odd hOl, I odd c2/c 4088 0.1 X 0.7 X 0.6 mm
+
4.4 27%
red crystals of Mo(CO)(DMF)(dpe)z (1.6 g, 76%).9 Anal. Calcd for C56H5=,N02P4Mo: C, 67.7; H , 5.6; N , 1.4. Found: C, 67.1; H, 5.7; N , 1.3. When Mo(CO)(DMF)(dpe)z (1.6 g) was recrystallized from benzeneln-hexane under a dinitrogen atmosphere, dinitrogen replaced the D M F ligand from the complex to give orange crystals, which were separated, washed with n-hexane, and dried in vacuo to yield 2 (1 .O g, 63%). Anal. Calcd for C56HjlN~OP4Mo:C, 68.1; H, 5.2; N,2.8. Found: C, 67.9; H, 5.4; N , 3.2. The presence of benzene in 2 was checked by gas chromatographic analysis of a toluene solution of
2. Method B. Benzyl propionate (3.4 g, 21 mmol) was added to a solution of frans-Mo(N2)z(dpe)2 (2.0 g, 2.1 mmol) in benzene (60 mL). The mixture was heated under reflux for 30 min, during which the solution had become dark brown. On cooling under dinitrogen, the dark brown solution changed rapidly to orange. Addition of n-hexane (80 mL) deposited orange crystals, which were filtered off, washed with n-hexane, and dried in vacuo to yield 2 (1.1 g, 53%). When toluene was used as solvent instead of benzene, 2 was obtained similarly in a moderate yield (54%); however, in this case orange crystals of 2 were mixed with a small amount (3%) of yellow crystals of ci~-Mo(CO)z(dpe)2.~O Gas chromatographic analysis of the reaction system disclosed the formation of ethylene, ethane, and benzene as decarbonylated products. Preparation of Mo(C0Xdpe)z(1). Argon gas was bubbled through a solution of 2 (99 mg, 0.10 mmol) in benzene ( I O mL) at 50 'C for 3 min. The original orange color changed rapidly to dark brown. On addition of n-hexane (1 5 mL) to the resulting solution under an argon atmosphere, black crystals were formed, which were filtered off, washed with n-hexane, and dried in vacuo to yield 1 (48 mg, 52%). P ~69.1; M OH :, 5.2; N , 0.0. Found: C, Anal. Calcd for C ~ ~ H ~ ~ O C, 68.7; H , 5.3; N, 0.0. Reaction of Mo(COXdpe)2(1) with Dinitrogen. Under a dinitrogen atmosphere benzene ( 5 mL) was added to crystals of 1 (46 mg, 0.05 mmol). The moment the complex dissolved, the solution became orange. Addition of n-hexane ( I O mL) deposited orange crystals of frans-M0(CO)(N2)(dpe)2.~/2CgH6 (2, 37 mg, 75%). Reaction of Mo(C0Xdpe)z (1) with Carbon Monoxide. Carbon monoxide was bubbled through a solution of 1 (95 mg, 0.10 mmol) in benzene (IO mL) at room temperature. The color of the solution immediately changed to yellowish orange and after a few minutes n-hexane (1 5 mL) was added to deposit yellowish-orange crystals, which were filtered off, washed with n-hexane, and dried in vacuo to yield frans-Mo(CO)2(dpe)2 (29 rng, 30%) ( u (CEO) 1812 cm-1). Anal. Calcd for C54H4gOlP4Mo: C, 68.4; H , 5.1, N , 0.0. Found: C , 68.9; H , 5.0; N , 0.0. When the above reaction solution was allowed to stand for several hours and then n-hexane was added, the well-known compound cisMo(CO)z(dpe)210 was exclusively isolated as yellow crystals. Crystal Preparation. Dark red crystals of 1 and orange crystals of 2 were precipitated in the form of plates from benzeneln-hexane under argon and dinitrogen atmosphere, respectively, and were sealed in
used data (Fa 1 3 a F a ) total data 20 limits scan speed (28) scan length, min background weighting schemeo
R b (isotropic) R w C(isotropic) R (anisotropic) R , (anisotropic) R (final) R , (final) (I
Mo(COI(N2)(dPe)2 * 'hC6H6
7122
3606
13 341 20 I60' 2'/min 1 0.45 tan 0 measd for I O s a t each end of the scan w = 0.7 for IFoI < 19 w = 1.0 for 19 5 IF,l I 7 6 w = (76/1F01)2 for 76 < IF01 0.108 0.135 0.09 1 0.108 0.076 0.087
5496 20 5 42.5' 2'/min 1 0.45 tan 0 measd for 10 s at each end of the scan w = 0.7 for IFa(< 38 w = I .O for 38 5 lFol 5 76 w = (76/1F,1)2 for 76 < IF01 0.1 10 0.146 0.088 0.120 0.084 0.120
+
+
The scale of F, is approximately equal to absolute scale. R = - I F c I I / z I F o l . 'Rw = [xw(JFoI- I F ~ ( ) * / Z W I F ~ ) ~ ] ' / ~ .
ZIIFoI
Pyrex glass capillaries under the same atmosphere for x-ray data collection. Crystallographic Data. The crystals of 2 belonged to the monoclinic system with the absent spectra: hkl, h k odd; h01, I odd, that were characteristic of the centrosymmetric space group C2/c or the noncentrosymmetric space group Cc. The centrosymmetric space group was shown to be the correct one on the basis of the following results: (a) the acceptable positional parameters, thermal parameters, and agreement indexes in the successful refinements; (b) the clear and distinct location of all the 48 unique hydrogen atoms except solvent hydrogens in a difference Fourier map. Lattice parameters of both crystals were determined by a least-squares fit to the setting angles for 12 hand-centered reflections with 20' < 20 < 32' for the complex 1 and 16' < 20 < 3 1' for the complex 2 using the average of positive and negative 28 angles for Mo Kcu. Because of air sensitivity and good solubility of the complexes, only approximate densities, values of which were between those of chloroform ( d = 1.49) and glycerol (d = 1.26), could be observable by flotation. Table 1 shows the pertinent crystal information for both crystals. Data collection was carried out with LiF-monochromatized Mo Kcu ( A = 0.7107 A) radiation, using a Rigaku automated four-circle diffractometer by 28-w scan technique. Four standard reflections for each complex were monitored every 50 measurements to check any unfavorable effects. The systematic changes in the intensities were not observed. The variation of their intensities was within 2.3% for the crystal of 1 and 5.5% for the crystal of 2, respectively. Lorentz and polarization corrections were applied in the usual manner, but no absorption correction was made since maximum absorption effects (pR) are 0.63 and 0.62 for 1 and 2, respectively. Table I I shows the details of intensity collections and refinements of both crystals. Structure Refinement.]]The Patterson synthesis was used to locate the molybdenum atom for each complex. Subsequent Fourier syntheses revealed the positions of all the nonhydrogen atoms except the carbon atoms of the solvated benzene of the complex 2 because of the disorder of it. The structures were refined by block-diagonal leastsquares technique for nonhydrogen atoms first with isotropic thermal parameters, then with anisotropic thermal parameters. The quantity minimized was B w ( ( F , ( - I F c ( ) 2where in the case of 2, disordered benzene was neglected in F,.The atomic scattering factors were taken from the International TablesLzaand the anomalous terms for M o and P were those of Cromer and Liberman'2b and were included in F,. At this stage, difference Fourier syntheses showed clear peaks of hydrogen atoms of both complexes except those of the solvated molecule in the complex 2. Then we carried out block-diagonal least-squares calculations including the positional parameters of the hydrogen atoms,
+
4449
Table IIIa. Positional and Thermal Parameters for the
Table IVa. Positional and Thermal Parameters for the
Nonhydrogen Atoms of Mo(CO)(dpe)2
Nonhydrogen Atoms of Mo(CO)(N2)(dpe)r1/2C6H6
2
Y
no
iin!ii
ll051ll
135211j
247121
16712!
294121
PI11
1338111
1031111
2855121
335191
4151111
PI21
12961li
2120111
2778121
296181
410110~
4361101 iizia!
Pi31
1146111 3426111
*tern
'lib
'33
'12
'11
"23
10131
19121
4171
25111
-22181
3417)
-12161
-10171
46151
111161
-111171
341181
~ 1 8 1 -61161
316181
4lOliOI
0171
-3171
681151
4251101
350191 4201101
-15171
ioa18i
36171
32111
65161
311701
6170161
11541571
8451491
5601361
1271461
4151371
1471171
5161411
5651471
4241371
1271421
li1i321
1001391
3471691
4491.1
5861611
-76'621
5181841
1461581
7141901
-501581
1875141 2058141
1694141
5169171
103141
1362131
1955111
1291351
4881451
5661461
371lzr
451311
671361
c121
360141
1922111
2289171
5011411
361291
-371291
-621131
4189141
2017141
495711~
65:154!
4931431
11351
-17!31!
101181
CI41
4141141
1492131
4298181
2861321 3341361 3061351
4711411
c131
5461471
641i501
451321
-171331
5971481
4201441
4531421
451311
-121351
6551611
.3841139l
6861651
1471671
2111511
-1171681
c 1 1 1 1 1 1214151
875131
C l 1 1 2 1 1841161
988161 948111
1165171 5791101 -7201111
13151115 1
.1 7 1 6 1 1 1 2 1
6081681
C l 1 1 4 1 1105191
719161 -14251111
14691123 1 ,, 1 9 2 1 1 0 7 1
581(691
CI1151
501181
651161
-8681111
12431111 1 129111181
770180i
Cill61
2151105
1631921 -3061911
-8'701
891751
-441701
-41751
231691
-1ai6s, 691861
-661691 -18,571
721151
781158'
9101831
6 6 7 611 -1001621
359131
3600171
4091381
5251481
191'431
-140141
3C69191
856170'
59016C.
6751501
C11231
1306171
-645141
1 7 2 5 1 1 1 1 12281981
463159'
9 4 8 , 8 2 1 -15916:1
CIl24l
1109161
-642141
48851101
aio!w
6671681
6261731
-111571
3:1581
1141561
C11251
96616,
-154151
51121101
9111771
6651661
861173,
-651581
2451601
1961561
C11261 1 0 2 7 1 6 1
359141
47881101
8341681
5161541
7841661
-1149'
2551541
C l l l l i
919141
2868131
3739171
3121321
484'421
3891351
881291
CI2121
300151
1204141
izi)!ai
5601481
8241691
4761431
2211471
451321
-:91361
105,511
-241471
-61-11
-1071541
211811
671941 -121991
2441931 -521731
-541911
18,651
-511691
551781
-341751
951941
871991 691981
621901
1391481
18!1311 -771821
481271
-91311
2011831
-481361
-2031451
-22(1191
255110'11
10111241
59611131
-4311731
1967191
5141521
866170
351441 -2381541
3618141
5201191
6431561
izi1641
718!611 5581571
2591511
16615i
59148)
1831451 -2491491
3358141
5682 I71
862 1661
8111701
3791401
1001561
151401 -1591451
C12161 1261141
2952131
4955171
4951431
4861461
4361401
-31121
C I l 2 1 1 1173141
2719131
1351161
3311331
6271491
2801321
21151 241321
221251
391311
661761
C12221
1620161
3264141
1454181
9441701
saoiss!
5 4 4 1 4 8 1 -1131551
1781461
201471
1611901
C 0 2 3 1 1114181
3556151
7161691 -1441111
240!681
1621581
C l l 2 4 1 1685111
3292151
-711191
9161761
10941901
6061571
-981141
931521
2521651
1211161
Cl1251 1 4 7 l l l l
2157151
-839181
9181791
17011961
1511451 -1071701
121411
-331511
-41011071
C12161 1314151
2462141
428i101 i z i 5 ~ 1 0 5 1 i 4 2 1 7 4 1
216111
5251411
7241591
4261421
-1181431
151351
2614131
2708171
4081371
427141~
2878141
2776191
4841411
6941611
7021581
-69143,
1701421
241481
2959151
16651121
6371611
7781741
12991931
-391541
5381651
1181681
481311
1381301
2685122
80111131 1 6 0 7 1 2 5 6 '
38611661 - 5 9 2 1 1 5 9 1
1 1 8 6 2 1 3 1 1 6 2 5 1 2 8 6 1 268114111 - 4 6 6 1 2 0 4 1
-3'1131
-31311
C13141 4402171
2187151
5501111
10661911
9251841
9451831
20.71711
6251121
1161671
Cl3151
3731171
2520161
465191
10251881
132111061
4801561
1131801
2551561
1141631
CO161 3364161
2435151
1526181
1 1 6 5 1 2 6 8 1 -87512791 84011971 -74211991
-111411
C11131 0 9 2 1 6 1
4331381
25111111
2115130
-481341
C I l l Z l 4468151
C13111 3169141
1041.271
51951 501871
301(10l!
984161
3608141
-611681
-8711061
cIa1o
22151
2118OL -8oi631 -1611911
2081851
C11151
Cl2lll
1561591 -1401761
-291341
-3131141 -1621771
-128 5 1 1
39:69i
11671
1541641 -1B8166I
-111391
533161
-211341 331521
-271561
102,701
C l l 2 l 1 1218141 C i l l Z i 1364161
4~41101
-251601
4 8 ~ 1 7 3 1- 1 1 8 1 8 0 1 1011731
1c15,
lS$I?! 1011171
4065!21
0
CI1131 1771181
-916:
4055121
C O l CIlI
323161
16131
1183111
1086111 1683131
PI41
'22
171711
-1441851 -17111071 -9511071 4811041
-5aiazi
-13170
-981821
-198wii
-2541991
31991
-13511201
16111051
16011061
-8711141
18190
-41011211
881801
-1511851
111691
-1l8167i
1381611
9231141
3921431
Cl3211 3314141
3012131
4998111
3171341
6121501
4111E11
-61331
-221451 361291 - 1 5 2 0 7 1
1191851
321921
C13221
3235151
2941141
6755181
5481481
7011601
4911461
-501431
871371 -2191421
-571891
10311061
Cl323i
319316L
3409151
ioii1'1i
640!59!
105019i1
6931601
491581
5 9 1 4 1 1 -1221601
18811051 -19311051
C l 3 2 4 1 3209111
1925151
65241111
8311i61
1139!991
8071741
1151691
C13251 3267111
4005141
52941121
9681641
5211611
11731971
-161511
961721 - 1 7 3 1 6 1 1
-551881
C13261 3324161
3545141
4518191
7861651
5501551
6751581
711481
1281491
-891461
991691
591751
C14111 3561141
588111
2833171
4091371
3881381
1341381
621301
1131291
281311
611141
-461721
Cl4121
181141
1725181
5191451
5811521
5321461
-201391
1911311
201401
1211811
3171961
8171731
2451451
91481
2881961
249llOll
2141641 - 1 6 6 1 5 5 1 1401891 211531 1561601 41461
2461931
3786151
C l 4 1 3 1 3196161 C l 4 1 4 1 3590111
424141 -114151
C 1 4 1 5 1 3 3 7 5 1 1 0 1 -311151
C1416l
727181
7131601
1611551
5231511
-161541
127011001
1241121
6581631
-31691
18651111 198411531
5681701
8 1 6 ( 8 0 1 -223181)
5041531
8101101
151411
81591 - 5 1 9 1 6 9 1
3362181
41141
2890191
146611071
5681611
C14211 3 5 5 9 1 1 1 Cl4221 2 9 5 5 1 5 1
619131
5438161
5451431
474140
3111341
1051351
411301
501311
514141
6051191
5921531
6961631
195'641
1801471
2191411
3991521
9891851
9491681
1064i901
3211721
4411711
5451141
12151961
8061141
5101521
4031701
2551511
2131521
181581 1291441
422174)
Cl4211 3 0 4 1 1 7 1
114151
70481121
-891661
C14241 3103111
-141151
C l 4 2 5 1 4312161
-36161
67961101
8111131
135311131
8081141
5161761
C14261 4 2 3 7 1 5 1
350151
5836191
593155:
1201!97!
1921161
3441591
1319191
-011201
123071 601731
1051lOOl -1001931
151801 -111731 -1241641
-641811
-123091
-261981
-171196l
10011241
-641841
49411321
-411791
1351951
-131781
ir1215ai
while their isotropic thermal parameters were fixed at 6.0 A2. After the final refinement, the standard deviations of observations of unit weight [ 2 w ( ( F o (- IFc1)2/(mwere 3.41 and 10.7, respectively, where the numbers of reflections ( m )were 7 122 and 3606 and the numbers of refined parameters ( n ) were 725 and 743, respectively. In the final cycle, no parameter shifted by more than 0.3 of its estimated standard deviation. Analyses of w(JF,I as functions of setting angles, F,, and Miller indexes revealed that agreement was not good a t low angles of the complex 2.This is to be expected in view of our inadequate treatment for the rather ill-defined solvent molecule. The maximum densities in the final difference Fourier syntheses were 0.7 and 0.8 e / A 3 for 1 and 2, respectively. The positional and thermal parameters obtained from the last cycle of refinement are listed in Tables IIIa,b and IVa,b with the associated standard deviations estimated from the inverse matrix. A listing of the observed and calculated structure amplitudes used in the refinements is available.
Results and Discussion Synthesis of a Five-Coordinate Molybdenum(0)Complex Mo(CO)(dpe)2(1) from trans-Mo(N2)2(dpe)z.The molybdenum bis(dinitrogen) complex trans-Mo(N2)2(dpe)2 (3) reacts with
D M F in benzene at reflux to yield a dark red complex Mo(CO)(DMF)(dpe)z. The only other example of carbon monoxide abstraction from amides was found in a rhodium c0mplex.1~Infrared measurements show absorptions assignable to v ( C ~ 0at) 1690 cm-' and v(C=O) at 1630 cm-', where the v(C=O) of the D M F ligand is ca. 30 cm-I lower than that of free DMF. The molybdenum carbonyl complex with a strong u donor, Mo(PMe3)(C0)5, shows v(C=O) bands at 2071, 1952, and 1943 cm-',I4 while the analogous complex containing DMF, Mo(DMF)(CO)s, exhibits v(C=O) bands at 2068, 1924, and 1847 cm-I.l5 CottonI5 attributed this lower shift of v(C=O) bands in the latter complex to the r-donor capacity of DMF, which can be understood by considering the bonding in terms of the hybridization of the canonical forms, as shown here. The
'H
' H
exceedingly low v ( C ~ 0 band ) of the complex M o ( C 0 ) (DMF)(dpe)z described here may be, therefore, due to both
4450
Journal of the American Chemical Society
1
100:14
1 July 5,1978
Figure 3. Perspective view of Mo(CO)(N2)(dpe)?.l/&H6. The shapes of the atoms in this drawing represent 50%0 probability contours of thermal motions. Figure 1. Perspective view of Mo(CO)(dpe)z. The shapes of the atoms in this drawing represent 50% probability contours of thermal motions.
c1
a benzene solution of 2 changes rapidly to dark brown. From this solution, an unsaturated complex 1 is isolated as black crystals. The infrared spectrum of 1 exhibits a band a t 1807 cm-’ assignable to v ( C E 0 ) . This reaction is reversible and, dissolved in benzene under dinitrogen, 1 is easily reconverted to 2.
2
trans-Mo~CO)(Nz)(dpe)2 Mo(CO)(dpej2 2 N2 1
Figure 2. Perspective view of Mo(CO)(dpe)z. The shapes of the atoms in this drawing represent 50% probability contours of thermal motions.
the strong a-donor property of dpe ligands and the strong r-donor property of the D M F ligand.16 This complex can be recrystallized from benzene under an argon atmosphere, but is completely converted to 2 on recrystallization under dinitrogen.
3
Mo(CO)(DMF) ( d ~ e ) ~ trans- Mo(CO)(N2) (dpe)2 DMF 2 On the other hand, 2 can be directly obtained from the reaction of 3 with benzyl propionate in toluene a t reflux under dinitrogen. In this reaction, ethylene, ethane, and benzene are detected as decarbonylated products.’’ The infrared spectrum of 2 shows medium bands a t 2110 and 2080 cm-l, which change position to 2036 and 2009 cm-l upon I5N substitution and are therefore associated with v(N==N), and strong bands a t 18 12 and 1789 cm-l assignable to v ( C ~ 0 )The . splitting of u ( N r N j and v ( C ~ 0is)due to a crystal effect since such splitting was not observed in solution (v(C@) 1799 cm-l and u ( N r N ) 2128 cm-l in benzene). A sharp singlet observed at -69 ppm (relative to 85% H3P04) in the 3 1 PNMR spectrum indicates a trans configuration of 2. The dinitrogen ligand of 2 is very labile in solution, which is consistent with the high v ( NEN) caused by the presence of a strong n-acceptor CO ligand in the trans position. Thus, on removing dinitrogen in vacuo or with a stream of argon, the original orange color of
Structures of Mo(COXdpe)2 (1) and Mo(CO)(N~)(dpe)y */2C6H6(2).The structure of 1 consists of discrete, well-separated monomers. A perspective view of the complex, showing the numbering scheme, is shown in Figures 1 and 2. The carbon ring atoms are labeled as C(xyz), x being the first ring index [( 1)-(4)], y the second index [(1)-(2)], and z the position of the atom [(1)-(6)]. The carbon C ( x y z ) attaches P(x). The hydrogen atom of phenyl group H(xyz) bonds to C(xyz), and the methylene hydrogen atom H(xy) bonds to C(x). This five-coordinate complex has a nearly square-pyramidal structure with four phosphorus atoms as a basal plane and a linear carbonyl ligand in the axial position. The minimum angle between thevector from Mo to C(5) and the four phosphorus atoms’ least-squares planei8 is 87.4’ and it may be regarded as perpendicular. The structure of the complex 1 is not unexpected, because substantial evidence has been presented that five-coordinate group 6 metal(0) carbonyls and their derivatives exhibit square-pyramidal rather than trigonal bipyramidal geometry.4b9c9S,19Furthermore the predominant square-pyramidal intermediates of SNI processes have been shown to contain the best n-accepting ligand in the axial p o s i t i ~ n .As ~ ~expected, -~~ the complex 1 has an axial carbonyl ligand, which is compatible with the finding that the reaction of 1 with carbon monoxide results in the formation of trans-Mo(CO)z(dpe)2, followed by isomerization to the thermodynamically more stable cis isomer.20 The molybdenum atom of the five-coordinate complex 1 is displaced 0.13 8, out of the least-squares plane18 defined by the four coordinated phosphorus atoms toward the carbon atom of the carbonyl ligand, indicating that the molybdenum atom and the four phosphorus atoms lie nearly in the same plane. This is consistent with Hoffmann’s prediction2) that the conformation of a n MLS molecule, if it is a square pyramid, will clearly depend upon the number of the d electrons and d6 systems will favor a “flat” square pyramid. In the case of another d6 square-pyramidal complex, R u C I ~ ( P P ~ the ~)~,~~
Hidai et al.
/ Mo(CO) (N2J(Ph 2PCH2CH2PPh 2) 2-'/2C,jHg
445 1
Table V. Selected Distances (A) and Angles (deg)
MO-C( 5) Mo-N(I) Mo-P( 1 ) Mo-P(2) MO-P(3) MO-P(4) C(5)-0 N(l)-N(2) P( I)-C( I ) P( 1)-C( 1 I I ) P( 1)-C( 121) P(2)-C(2) P(2)-C(211) P(2)-C(22 I ) P(3)-C(3) P(3)-C(311) P(3)-c(32 1) P(4)-C(4) P(4)-C(411) P(4)-C(421) C-C (phenyl) C-H (phenyl) nonbonded distance Mo-H( 1 12)
Bond Distances 1.903 (9) 2.438 (2) 2.448 (2) 2.453 (2) 2.468 (2) 1.192 (12) 1.871 (8) 1.865 (9) 1.851 (8) 1.891 (8) 1.864 (8) 1.866 (8) 1.865 (9) 1.846 (8) 1.849 (9) 1.892 (9) 1.856 (7) 1.867 (8) av I .394 (25) av 0.97 (I 0)
1.973 (16) 2.068 ( 1 2) 2.459 (4) 2.447 (4) 2.435 (4) 2.452 (4) 1.127 (20) 1.087 (18) 1.852 (17) 1.847 (14) 1.805 (1 4) 1.840 ( 1 6) 1.829 (18) 1.825 ( 1 6) 1.829 (16) 1.817 (17) 1.831 (15) 1.845 ( 1 7) 1.842 ( 1 5) 1.854 (16) av 1.377 (32) av 1.01 ( 1 I )
Figure 4. Perspective view of M o ( C O ) ( N * ) ( ~ ~ ~ ) ~ . IThe / ~ Cshapes ~H~. of the atoms in this drawing represent 50% probability contours of thermal motions.
Any other significant intra- and intermolecular contacts are not observed. The maximum and minimum C-C bond distances are 1.450 (19) and 1.347 (21) A, respectively, while the C--H bond distances are 1.18 (1 1) and 0.77 ( I 1) A, respectively. We conclude that the complex 1 has a five-coordinate, 16-electron molybdenum atom, and therefore can readily combine with gaseous dinitrogen of other two-electron donating species to form six-coordinate 18-electron systems. The reversibility of the dinitrogen coordination is probably due to the tendency of the ortho hydrogen of one of the dpe phenyl groups to block this unused octahedral site, as well as the nitrogen ligand being weakly bound. Various substrates other than dinitrogen such as amines, pyridines, olefins, and amides react with 1 to yield complexes of the type trans-Mo(C0)L(dpe)2. In these reactions, the bulkiness of the substrate has a large effect in its reactivity toward l.3-22 The structure of 2 also consists of discrete, well-separated monomer and solvent molecules. A perspective view of the complex, showing the numbering scheme, is shown in Figures 3 and 4. The carbon and hydrogen atoms are named in the same way. This six-coordinate complex has octahedral geometry, with four phosphorus atoms as a basal plane and dinitrogen and carbonyl ligands in the trans axial positions. There are no significant intra- and intermolecular contacts. The maximum and minimum C-C bond distances are 1.428 (26) and 1.264 (50) A, respectively, while the C-H bond distances are 1.44 (22) and 0.83 (20) A, respectively. The solvent molecule exists near the C 2 axis, but we cannot refine the position of the molecule because of its disorder. There is a high electron density sphere ( 1 .O-2.2 e/A3) (radius ca. 1.7 A) at the center
2.98 ( 1 1) Bond Angles
C(S)-Mo-N( 1) C(5)-Mo-P( I ) C ( 5)-Mo-P( 2) C(5)-Mo-P(3) C(5)-Mo-P(4) N ( I)-Mo-P( 1) N ( 1 )- Mo-P( 2) N ( 1)- Mo-P(3) N ( I)-Mo-P(4) P( I)-Mo-P(2) P( 3)-Mo-P(4) P( I)-MO-P(3) P( 2)-Mo-P(4) P( I)-MO-P(4) P( 2)-Mo-P( 3) Mo-C( 5)-O Mo-N( I)-N(2)
90.36 (27) 92.15 (27) 95.05 (27) 95.04 (27)
79.81 (7) 79.75 (7) 174.60 (7) 172.81 (7) 99.83 (7) 99.92 (7) 178.6 (8)
174.61 (59) 85.05 (48) 87.30 (48) 100.37 (48) 90.16 (48) 90.78 (36) 95.29 (36) 84.07 (36) 87.64 (36) 79.29 (1 3) 79.48 ( 1 3) 172.89 (14) 174.60 ( 1 4) 105.26 ( 1 3) 96.28 ( 1 3) 175.0 (14) 177.0 ( 1 2)
displacement from the basal plane is 0.456 A, which may be ascribed to the bulkiness of the axial phosphine ligand. In the complex 1, the nearest hydrogen, H( 112), is 2.95 (1 1 ) A from molybdenum, suggesting van der Waals contact of the ortho hydrogen of one of the dpe phenyl groups with the metal. Table VI. Distances and IR Spectra of Carbonyl Ligands
distances, -
complexe
v(C=O), cm-1
MdCO)(dpe)2" 1807 M O ( C O ) ( N ~ ) ( ~ P ~ ) ~ . ~ / ~ C ~ H ~ "1812 1791 Mo(C0)3(cot)' I887 I734 2020 Mo(C0)4(d~m)~ 1919 1907 1881 Mo(C0)3( trien) 1898 1758
Mo-C
c-0
1.903 (9) 1.973 ( 1 6)
1.192 (12) 1.127 (20)
*
1.99 ( I )
*
*
1.93 ( I )
* 1.18 (2)
1.15 ( I )
* 2.05 (3)
*
* 1.943 (6)
* 1.152 (9)
1.12 ( I )
Carbonyls trans to the C=C Carbonyls trans to the phosphorus atoms Two mutually trans carbonyls Carbonyls trans to the nitrogen atoms
This work. J. S. McKechnie and I. C. Paul, J . Am. Chem. Soc., 88,5927 (1966); S. Winstein, H. D. Kaesz, C. G. Kreter, and E. C. Friedrich, ibid., 87, 3267 (1965). K. K. Cheung, T. F. Lai, and K. S. Mok, J . Chem. Soc. A , 1644 (1971); J. Chatt and H. R. Watson, J . Chem. Soc., 4980 (1961). F. A. Cotton and R. M. Wing, Inorg. Chem., 4,314 (1965); ref 15. e dpe = Ph*PCH*CH*PPh?;cot = cyclooctatetraene; dprn = PhzPCH2PPh2; trien = diethylenetriamine. f *, average value.
4452
Journal of the American Chemical Society
1 100:14 /
J u l y 5, I978
(x = '/z, y = 0.16, z = l/4), but there are not suitable peaks for Supplementary Material Available: Tables IIIb and IVb, positional parameters for the hydrogen atoms of Mo(CO)(dpe)z and Mo(C0)carbon atoms. (N2)(dpe)2.'&H6, respectively, and the table of observed and calSelected bond distances and angles are shown in Table V. culated structure amplitudes (18 pages). Ordering information is given The average Mo-P distances of 2.452 (2) and 2.448 (4) 8, on any current masthead page. found in the complexes 1 and 2, respectively, are nearly equal to that of 2.454 ( 1 ) 8, found in the complex 3,23but shorter than that of 2.541 (4) 8, found in [ M O F ( N Z H ~ ) ( ~ ~ ~ ) ~References ] [ B F ~ and ]~~ Notes and 2.559 ( 5 ) 8, in M0Br*(C0)3(dpe).~~ The average P-Mo-P (1) Part 5: M. Hidai, Y. Mizobe, and Y. Uchida, J. Am. Chem. SOC.,98, 7824 angles of 79.79 (7) and 79.39 (13)' found in the complexes 1 (1976). (2) (a) University of Tokyo; (b) Science University of Tokyo. and 2, respectively, are essentially equal to those found in the (3) T. Tatsumi. H. Tominaga, M. Hidai, and Y. Uchida, J. Organomet. Chem., other three complexes. Transition metal-phosphorus bonds 114, C27 (1976). are usually considered to have some double bond character (4) See, e.g., (a) W. D. Covey and T. L. Brown, lnorg. Chem., 12, 2620 (1973); (b) D. J. Darensbourg and H. H. Nelson, Ill, J. Am. Chem. SOC.,96, 651 1 presumably through back-donation (dr-d*r) from the metal, (1974); (c) D. J. Darensbourg, G. R. Dobson, and A. Moradi-Araghi, J. Orwhich greatly depends upon the electron density of the metal. ganomet. Chem., 116, C17 (1976). (5) See, e.g., (a) R. N. Perutz and J. J. Turner, J. Am. Chem. SOC.,97, 4791 The shorter average Mo-P distances of the molybdenum ze(1975);(b) J. K. Burdett. R. N. Per&, M. Poiiakoff, and J. J. Turner, J. Chem. rovalent complexes 1 and 2 compared with those of high-valent SOC.,Chem. Commun., 157 (1975); (c) J. D. Black and P. S . Braterman. molybdenum complexes reflect the greater back-donation from J. Organomet. Chem., 63, C19 (1973); (d) J. Am. Chem. SOC.,97, 2908 (1975). the metal to phosphorus ligands, which results in the shortening (6) (a) J. L. la Placa and J. A. Ibers. Inorg. Chem., 4, 778 (1965); (b) A. C. of the metal-phosphorus distances. Skapski and P. G. H. Troughton, Chem. Commun., 1230 (1968); (c) P. G. H. Troughton and A. C. Skapski, ibid., 575 (1968); (d) C. Masters, W. S. The Mo-C(5) distance of 1.903 (9) A found in the complex McDonald, G. Raper, and B. L. Show, ibid., 210 (1971); (e) K. W. Muir and 1 is one of the shortest Mo-C distances and the C - 0 distance J . A. ibers, Inorg. Chem., 9, 440 (1970). of 1.192 (1 2) 8, is one of the longest C - 0 distances, as shown (7) An apparently five-coordinate complex M ~ ( c ~ H ~ ) ( dhas p e )been ~ reported: T. Ito, T. Kokubo, T. Yamamoto, A. Yamarnoto, and S.Ikeda, J. Chem. SOC., in Table VI. On the other hand, the complex 2, which has diDalton Trans. 1783 (1974). Osborn et al., however, formulated the complex nitrogen in the trans position of the carbonyl ligands, shows as M O ( C ~ H , ) , ( ~ ~J. ~ )W. ~ : Byrne, H. U. Blaser, and J. A. Osborn, J. Am. Chem. SOC.,97, 3871 (1975). the longer Mo-C distance of 1.973 (16) 8, and the shorter C - 0 (8) (a) M. Hidai, K. Tominari, and Y. Uchida, J. Am. Chem. Soc., 94, 110 (1972); distance of 1.127 (20) 8,. (b) M. Hidai, K. Tominari, Y. Uchida. and A. Misono, lnorg. Synth., 15, 25 Goldberg and Raymond applied the "constrained model" (1974). This compound is more easily obtained in a pure state from the reaction (9) to the polycarbonyl tungsten complex, W(CO)5of Mo(CO)(N2)(dpe)2with DMF. (O=PPh2CHPPh3),26 in which they assumed a constant C - 0 (10) J. Chatt and H. R. Watson, J. Chem. SOC.,4980 (1961). (1 1) The UNICS program system for the HITAC 8700/6800 computers was distance since four equatorial carbonyl ligands are chemically employed at Tokyo University Computer Centre: Sakurai's RSLC-3 lattice equivalent. However, their constrained model could not be constants program; Ueda's PAMI Patterson and minimum function program; applied in this work, since both complexes 1 and 2 are monoIwasaki's ANSFR-P Fourier synthesis program: Ashida's HBLS-4 block-diagonal least-square and Fourier program; Ashida's DAPH distance, angle, carbonyl complexes. Insofar as this work, the differences of best plane, etc., program; and Jonson's ORTEP thermal ellipsoid plot proC - 0 or Mo-C distances of 1 and 2 are significant. These facts gram, (12) (a) D. T. Cromer and J. T. Waber, "International Tables for X-Ray Crystalsuggest that, in the complex 1, the carbonyl ligand accepts a lography", Vol. IV, Kynoch Press, Birmingham, England, 1974, Table 2.2A; considerable back-donation from the molybdenum atom and (b) D. T. Cromer and D. Liberman, ibid., Table 2.3.1. the shorter Mo-C distance and the longer C - 0 distance are (13) A . Rusina and A. A. VlcBk, Nature (London), 206, 295 (1965). (14) R. Pioiblanc and M. Bigorgne, Bull. SOC.Chim. Fr., 1301 (1962). presumably ascribable to the absence of any ligand in the trans (15) F. A. Cotton, Inorg. Chem., 3, 702 (1964). position competing for bonding electrons. In the complex 2, (16) The coordination of DMF In the complex Mo(CO)(DMF)(dpe)zthrough the nitrogen lone pair is excluded since (1) the five-coordinate complex 1 however, the Mo-C distance becomes longer, since both dicombines only with small primary and secondary amines to give Mo(C0)nitrogen and carbonyl ligands have to compete for bonding (amine)(dpe)2and it does not combine with tertiary amines such as NMe3 and (2) other bulky formamides such as HCONEt2and HCONPhZalso give electrons. analogous complexes. These results will be described in detail in a following The Mo-N-N linkage in the complex 2 is essentially linear paper. and the Mo-N distance and the N - N distance are 2.068 ( 1 2) (17) The mechanism of carbon monoxide abstraction with 3 from amides and esters will be discussed in a following paper. and 1.087 (1 8) A, respectively. The C-Mo-N linkage is also (18) Equation of the piane is 0.3579X + 0.0001 Y - 0 . 9 3 3 8 2 + 2,1829 = 0, nearly linear and the N-Mo-P angles are within the range of where the coefficients of X, Y, Zare equal to the direction cosines with 84.1 (4)-95.3 (4)'. The N-N distance of the complex 2 is respect to the axes a, b, c ' . The deviations (A) are P(1) -0.019, P(2) 0.020, P(3) -0.020, P(4)0.020, and Mo 0.135, respectively. All atoms except the shorter by 0.038 8, than the N - N distance of the complex 3,23 molybdenum atom were given unit weight in the calculation of the leastand the Mo-N distance is longer by 0.054 8, than that of the squares plane, and the molybdenum atom was given zero weight. (19) J. K. Burdett, Inorg. Chem., 14, 375 (1975). complex 3. Since the carbonyl ligand is a much stronger r (20) L. K. Holden, A. H. Mawby, D. C. Smith, and R. Whyman, J. Organomet. acceptor compared with the dinitrogen ligand, the backChem., 55, 343 (1973). donation from the molybdenum atom to the dinitrogen ligand (21) A. R. Rossi and R. Hoffmann, lnorg. Chem., 14, 365 (1975). (22) This wili be separately reported in a following paper. in the complex 2 does not occur as much as in the complex 3, (23) T. Uchida, Y. Uchida, M. Hidai, and T. Kodama, Acta Crystallogr.. Sect. 8, which is substantiated by the Mo-N and N-N distances ob31, 1197 (1975). (24) M. Hidai. M. Sato, M. Harakawa, T. Kodama, and Y. Uchida, Inorg. Chem., served and the higher v ( N r N ) at 21 10 and 2080 cm-' of the 15, 2694 (1976). complex 2 compared with v(N=N) a t 2020 and 1970 cm-I (25) M. G. 8. Drew, J. Chem. SOC.,Dalton Trans., 1329 (1972). of the complex 3.8 (26) S. Z. Goldberg and K. N. Raymond, lnorg. Chem., 12, 2923 (1973).
