Cationic Phosphenium Complexes of Group 6 Transition Metals

Hiroshi Nakazawa, Yoshitaka Yamaguchi, Kazumori Kawamura, and Katsuhiko Miyoshi. Organometallics 1997 16 (21), 4626-4635. Abstract | Full Text HTML ...
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Organometallics 1995, 14, 4173-4182

4173

Cationic Phosphenium Complexes of Group 6 Transition Metals: Reactivity, Isomerization, and X-ray Structures Hiroshi Nakazawa,*zt Yoshitaka Yamaguchi,+Tsutomu Mizuta,? and Katsuhiko Miyoshi*9$ Coordination Chemistry Laboratories, Institute for Molecular Science, MyodaGi, Okazaki 444, Japan, and Department of Chemistry, Faculty of Science, Hiroshima University, Higashi-Hiroshima 739, Japan Received April 19, 1 9 9 P The reaction of cationic diamino-substituted phosphenium complexes of group 6 transition

-

I

I

metals mer-[(bpy)(C0)3M{PN(Me)CH2CH2NMe}l+ (M = Cr, Mo, W)with L (L = PN(Me)CH21

CHzNMe(0R) (R = Me, Et), PPh3) proceeds with substitution of L for CO to produce [(bpy)-

(C0)2LM{PN(Me)CHzCH2NMe}]+. During the reaction, the phosphenium ligand remains intact. The product consists of trans (two phosphorus ligands are mutually trans) and cis isomers, and they equilibrate. The cis form is electronically and the trans form is sterically favored. A similar reaction takes place when cationic monoamino-substituted phosphenium r complexes are treated. Complexes trans-[(bpy)(CO)2{PN(Me)CH2CH2NMe(OMe)}Mo{PN-

-

I

I

(Me)CH2CH2NMe)].OTf (trans-2a.OTf)(OTf = S03CFd and trans-[(phen)(CO)z{PN(t-Bu)CH2-

,

1

CH20(0Me)}Mo{PN(t-Bu)CH~CH20}l*OTECH~Cl~ (trans-2j*OTfCH2Cl2)have been characterized by X-ray diffraction. The bond distance of Mo-P(phosphenium) is significant1 shorter than t h a t of Mo-P(phosphite) for both complexes: for trans-2a, 2.254 vs 2.495 and, for trans-2j72.238 vs 2.529 indicating a significant double bond character between Mo and P(phosphenium). For both complexes, the P-N bond distances in phosphenium and in phosphite ligands are almost equal, indicating t h a t there is no significant N P(phosphenium) n donation. The role of the amino groups on the phosphenium phosphorus is probably to protect the approach of a nucleophile to phosphenium phosphorus by high pn lone pair density flanking the phosphenium center.

A

A

A,

1

-

Introduction Since the first discovery of cationic transition-metal phosphenium complexes in 1978 by Parry et al.,l some such complexes have been prepared for several kinds of transition Phosphenium phosphorus in

-

n

/

' +

LnM-p\

Phosphenium

Cationic transition-metal phosphenium complex

these complexes takes sp2 hybridization, so that it has lone pair electrons coordinating to a transition metal and a vacant p orbital accepting some electron density Institute for Molecular Science. Hiroshima University. @Abstractpublished in Advance ACS Abstracts, August 1, 1995. (1)Montemayor, R. G.; Sauer, D.T.; Fleming, S.;Bennett, D.W.; Thomas, M. G.; Parry, R. W. J . Am. Chem. SOC.1978,100,2231.(b) Bennett, D. W.; Parry, R. W. J. Am. Chem. SOC.1979,101, 755. (2) Cowley, A. H.; Kemp, R. A. Chem. Rev. 1985,85,367. (3)Sanchez, M.; Mazieres, M. R.; Lamande, L.; Wolf, R. I n Multiple Bonds and Low Coordination i n Phosphorus Chemistry; Regitz, M., Scherer, 0. J., Eds.; Thieme: New York, 1990;Chapter D1. (4) (a) Day, V. W.; Tavanaiepour, I.; Abdel-meguid, S. S.; Kirner, J. F.; Goh, L.-Y.; Muetterties, E. L. Inorg. Chem. 1982,21,657.(b) Choi, H. W.; Gavin, R. M.; Muetterties, E. L. J . Chem. SOC.,Chem. Commun. 1979,1085. (c) Muetterties, E. L.; Kirner, J. F.; Evans, W. J.; Watson, P. L.; Abdel-meguid, S. S.; Tavanaiepour, I.; Day, V. W. Proc. Natl. Acad. Sci. U S A . 1978,75, 1056.

from a transition-metal d orbital. The phosphenium phosphorus can be thus considered to have the same electronic configuration as a carbene carbon or a silylene silicon in their transition-metal complexes. It is known that a carbene carbon and a silylene silicon in transition-metal complexes are very electrophilic and these complexes are stabilized by adduct formation with a Lewis b a ~ e . We ~ , ~here report the reactions of cationic phosphenium complexes of group 6 transition metals formulated as [(bpy)(C0)3M{PN(Me)CH2CH2NMe}l+ (bpy = 2,2'-bipyridine; M = Cr, Mo, W) with a trivalent phosphorus compound as a Lewis base and also report the geometrical isomerization and the crystal structures of the products. (5)(a) Cowley, A. H.; Kemp, R. A,; Ebsworth, E. A. V.; Rankin, D. W. H.; Walkinshaw, M. D. J . Organomet. Chem. 1984,265,C19. (b) Cowley, A. H.; Kemp, R. A.; Wilburn, J. C. Inorg. Chem. 1981,20,4289. (6)(a) Nakazawa, H.; Ohta, M.; Yoneda, H. Inorg. Chem. 1988,27, 973. (b) Nakazawa, H.; Ohta, M.; Miyoshi, K.; Yoneda, H. Organometallics 1989,8,638. ( c ) Nakazawa, H.; Yamaguchi, Y.; Miyoshi, K. J . Organomet. Chem. 1994,465,193. (d) Nakazawa, H.; Yamaguchi, Y.; Mizuta, T.; Ichimura, S.; Miyoshi, K. Organometallics, in press. (7)Electrically neutral transition-metal complexes described as [L,MPR21 can be considered a s phosphenium complexes if one thinks that they consist of L,M- and +PR2. However, in this paper we focus on electrically cationic transition-metal complexes described a s [La. MPR21+. (8)For carbene complexes see: Fischer, H. I n The Chemistry ofthe Metal-carbon Bond; Hartley, F. R., Patai, S., Eds.; John Wiley & Sons: New York, 1982;p 207,Vol. 1.

0276-733319512314-4173$09.00/0 0 1995 American Chemical Society

Nakazawa et al.

4174 Organometallics, Vol. 14, No. 9, 1995

Table 1. 31P N M R Data"

Results and Discussion Formation of [(bpy)(CO)&M(PN-N)I+ (L= Trivalent Phosphorus Compound). Recently we reported a preparative method for cationic phosphenium complexes of group 6 transition metals as shown in eq 1,6b,c

Q

Q l+

s! l +

cis-2x

lx

X

b C

d 277.32 (s) e

242.72 ( s j (JPW =

U

561.1 Hz) mer

fac

234.02 (d, J = 27.5 Hz; 222.16 (d, J = 268.6 Hz; (Jpw = 518.8 Hz) ( J p w = 589.0 Hz) 149.61 (d, J = 54.9 Hz) 144.28 (d, J = 326.6 Hz) 149.73 (d, J = 54.9 Hz) 235.57 (d, J = 326.6 Hz) 241.94 (d, J = 54.9 Hz) 242.36 (d, J = 54.9 Hz) 139.89 (d, J = 320.5 Hz) 227.52 (d, J = 320.5 Hz) 157.15 (d, J = 58.0 Hz) 152.70 (d, J = 369.2 Hz) 214.93 (d, J = 58.0 Hz) 224.47 (d, J = 369.2 Hz) 134.04 (d, J = 42.8 Hz) 130.12 (d, J = 271.6 Hz) 258.43 (d, J = 42.8 Hz) 242.29 (d, J = 271.6 Hz) 140.41 (d, J = 317.4 Hz) 228.10 (d, J = 317.4 Hz)

M E Cr Mo, W

where an alkoxy group on the coordinating phosphite is abstracted as an anion by BFyOEt2. The facial and meridional isomers of the product are the kinetic and thermodynamic products, respectively.6c Although the reactions are very clean and the products are stable in the solution unless exposed t o air, these phosphenium complexes have not been isolated so far due to the high reactivity. Therefore, [(bpy)(C0)3M(PN(Me)CH2CH21

NMe}l+ prepared in situ was used as a starting complex in the reaction with trivalent phosphorus compounds. A CHzCl2 solution containing a starting cationic phosphenium complex prepared according to eq 1 was cooled to -78 "C, an equimolar amount of a trivalent phosphorus compound (L) was added, and then the solution was allowed to warm to room temperature. The results are shown in eq 2, and the 31PNMR data are summarized in Table 1.

p l+

L

l+

L

l+

u l a : M = Mo

cis-2s : M = Mo, L = P(N-N)(OMe) cis-2b : M = Mo, L = P(N-N)(OEt)

trank2s : M = Mo, L = P(N-N)(OMe) trans-2b : M = Mo. L = P(N-N)(OEt)

CIS-2C : M = Mo, L = PPh3

trans-2c : M = Mo, L = PPh, Irans-2d : M Cr, L = P(N-N)(OMe)

cis-2e : M = W. L = P(N-N)(OMe)

IrankZe : M =W, L = P(N-N)(OMe)

I d : M = Cr le:M=W

trans-2x

130.15 (d, J = 274.7 Hz) 242.18 (d, J = 274.7 Hz) 126.52 (d, J = 274.6 Hz) 241.88 (d, J = 274.6 Hz) 35.84 (d, J = 180.1 Hz) 246.93 (d, J = 180.1Hz) 149.22 (d, J = 91.6 Hz) 248.56 (d, J = 91.6 Hz) 126.09 (d, J = 27.5 Hz; 119.56 (d, J = 268.6 Hz; (Jpw = 271.6 Hz) ( J p w = 329.6 Hz)

135.00 (d, J = 42.7 Hz) 257.71 (d, J = 42.7 Hz) 131.32 (d, J = 42.7 Hz) 256.74 (d, J = 42.7 Hz) 34.15 (d, J = 27.5 Hz) 257.64 (d, J = 27.5 Hz)

a 269.39 (s)

N-N = N(Me)CH,CH,NMe

In the case of reaction of l a with iN(MeICH2CH2-

f 253.84 (s)

g

h i 269.04(s) j a

In CH2C12.

bands at 1912 and 1834 cm-l (relatively broad compared with the absorption bands for la) in the YCO region in the IR spectrum, indicating that one carbonyl ligand in l a is replaced by L. The 31PNMR spectrum showed four doublets, 257.71 (d, J = 42.7 Hz), 242.18 (d, J = 274.7 Hz), 135.00 (d, J = 42.7 Hz),and 130.15 (d, J = 274.7 Hz). The first and third doublets were relatively weaker than the other two in intensity (The ratio was 24/76 (see Table 2)). The first two chemical shifts are in the region due to phosphenium ligands, and the last two ones are in that due to coordinating phosphites.6b,c This observation suggests that two geometrical isomers are formed and both of them have one phosphenium

-

7

ligand (PN(Me)CH2CH2NMe+)and one diamino-substituted phosphite ligand (PN(Me)CH2CH2NMe(OMe)). The coupling constants observed here indicate that in one isomer two phosphorus ligands are mutually cis (cis isomer) and in the other isomer they are trans (trans isomer). The trans .isomer can be depicted uniquely as shown in eq 2, whereas there are three possible structures (A-C) for the cis isomer.

1

NMe(OMe),the reaction mixture showed two absorption

(9) For leading references of silylene complexes see: (a) Zybill, C.; Muller, G. Angew. Chem., Int. Ed. Engl. 1987,26, 669. (b) Zybill, C.; Wilkinson, D. L.; Leis, C.; Muller, G. Angew. Chem., Int. Ed. Engl. 1989, 28, 203. ( c ) Probst, R.; Leis, C.; Gamper, S.; Herdtweck, E.; Zybill, C.; Auner, N. Angew. Chem., Int.Ed. Engl. 1991,30, 1132. (d) Leis, C.; Wilkinson, D. L.; Handwerker, H.; Zybill, C.; Muller, G. Organometallics 1992, 11, 514. (e) Straus, D. A,; Tilley, T. D.; Rheingold, A. L.; Geib, S. J. J . Am. Chem. SOC.1987, 109, 5872. (0 Straus, D. A,; Zhang, C.; Quimbita, G. E.; Grumbine, S. D.; Heyn, R. H.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J . J . Am. Chem. SOC.1990, 112, 2673. (g) Grumbine, S. D.; Chadha, R. K.; Tilley, T. D. J . A m . 1992,114, 1518. (h) Grumbine, S. D.; Tilley, T. D.; Arnold, Chem. SOC. F. P.; Rheingold, A. L. J . A m . Chem. SOC.1993, 115, 7884. (i) Ueno, K.; Tobita, H.; Shimoi, M.; Ogino, H. J . A m . Chem. SOC.1988, 110, 4092. (jj Tobita, H.; Ueno, K.; Shimoi, M.; Ogino, H. J . A m . Chem. SOC.1990,112, 3415. (k)Takeuchi, T.; Tobita, H.; Ogino, H. Organometallics 1991, I O , 835. (1) Corriu, R.; Lanneau, G.; Priou, C. Angew. Chem., Int. Ed. Engl. 1991, 30, 1130. (m) Woo, L. K.; Smith, D. A,; Young, V. G., Jr. Organometallics 1991,10,3977. (n) Lee, K. E.; Arif, A. M.; Gladysz, J. A. Chem. Ber. 1991,124,309. (01 Jutzi, P.; Mohrke, A. Angew. Chem., Int. Ed. Engl. 1990,29, 893.

Chl'

l+

7

+

l+

U

A

B

C

In order to determine the structure of the cis form, the 13C NMR spectrum of the reaction mixture was measured. The resonance pattern in the CO region gave us the clue. The apparent triplet observed a t 224.39 ppm with Jcp = 18.2 Hz as a main peak can be assigned to the trans isomer. In addition, two doublet of doublets were observed a t 226.05 ppm with JCP= 18.2 Hz and 11.8 Hz and a t 213.89 ppm with Jcp = 57.0 Hz and 16.1 Hz. Therefore, the possibility of C can be ruled out,

Cationic Phosphenium Complexes

Organometallics, Vol. 14,No. 9,1995 4175

Scheme 1

the OR group, whereas the middle point between the two phosphorus ligands for phosphite (phosphenium) complexes is not.

-

The reactions of l a with PN(Me)CHsCHzNMe(OEt) and PPh3, and the reactions of Cr complex Id and W complex l e with PN(Me)CH2CH2NMe(OMe), showed basically similar results to those of the reaction of l a

-

because the two CO ligands in C are magnetically equal. Since it has been demonstrated that the phosphenium ligand PN(Me)CHzCH2NMe+ is a stronger n-acceptor than a CO 1igand,lb@the phosphenium ligand is highly likely to prefer situating trans to bpy to trans to CO. Therefore, we propose that the cis isomer formed in the reaction has a structure A rather than B. Recently, Ogino and his co-workers reported the preparative methods and the X-ray structures of donorstabilized bis(sily1ene)complexes for FegiJ and Mn.gk They proposed that these complexes are formed from a n alkoxy-substituted silyl (silylene) complex, which is not detected because of the coordination of the alkoxy oxygen to the silylene silicon.

In the case of cis-2a, the 31PNMR resonances are diagnostic of a phosphite (phosphenium) structure. The cyclization product (which may be referred to as a bis(phosphenium) complex) is not observed.

Muetterties also reported the X-ray structure of [Mo{P(OMe)~}~{P(OMe)2}lPF~, which does not take a cyclization form but has a discrete phosphenium ligand.4a Therefore, a phosphenium ligand seems to have inherently less tendency to take a base-stabilized form, but a silylene ligand has the tendency, even though phosphenium and silylene ligands are isoelectronic. In other words, as shown in Scheme 1,the middle point between the two silicon ligands for alkoxy-substituted silyl (silylene) complexes is the energy minimum position for

with PN(Me)CH2CHzNMe(OMe);i.e., the phosphenium ligand remains intact and CO/L exchange reaction takes place resulting in the cis and trans isomer formation (shown in eq 2). In the case of the Cr complex, only the trans isomer was detected. The reason will be discussed later. The starting phosphenium complex of W ( l e )exists mainly as the fac form. However monitoring the reaction with L by the 31PNMR spectra revealed that the isomerization from fac to mer forms was immediately completed by the addition of L, and then the C O L exchange reaction took place gradually. So, it can be said that, even in the case of the W complex, the reaction of the mer isomer with L eventually takes place. The promotion of the fac-mer isomerization by the addition

-

of PN(Me)CH&HzNMe(OMe), HOEt, or O T f was observed. The details will be reported elsewhere. Although every reaction shown in eq 2 takes place cleanly to give only cis-2 and transd (in the Cr case, only trans-2d1, several attempts to isolate these products in the solid state were unsuccessful presumably due to their high reactivity. However, it was found that only transda could be isolated as a S03CF3- ( O T f ) salt when l a prepared from fac-[(bpy)(C0)3Mo{PN(Me)CH21

CH2NMe(OMe)}l and Me3SiS03CF3 (TMSaOTD in place

of BFs.OEt2 was treated with PN(Me)CHzCHzNMe(OMe). The reaction mixture contains cis-2a and trans2a, but after workup only trans-2a.OTf was obtained as reddish orange crystals. The X-ray structure will be shown below. Formation of [(bpy)(CO)&M{PN-O}]+ and [(bpy)(CO)&M(PO-O}l+. Next we examined the reaction of cationic complexes containing monoamino-substituted phosphenium ligand with monoamino phosphite. I f

-

prepared from fac-[(bpy)(CO)3Mo{PN(Me)CH2CH20)(0Me)}] with BF30OEt2 reacted with PN(Me)CHzCH20(OMe) to give cis-2f and trans-2f (eq 3).

1f

CIS-21

trans-21

In the reaction of 3g with BFs.OEt2 o r TMS-OTf, the corresponding phosphenium complex [(bpy)(CO)aMoI

{PN(t-Bu)CH2CH20)1+was formed, but some other Mo complexes were also formed. So the resulting solution could not be used for the next reaction. However, the treatment of 3g with TMSmOTf in the presence of a n

4176 Organometallics, Vol. 14, No. 9, 1995

Nakazawa et al.

equimolar amount of PN(t-Bu)CH2CHzb(OMe)showed a clean reaction t o give trans-2g without the cis isomer (eq 4).

Table 2. Cis-Trans Isomer Ratio of [(bpy)(C0)2LM(phosphenium)l+ X

cis-2x

trans-2x

a

24 28 7

76 72 93

d

0

100

e

22 69

78 31

b C

p'.

0

0'

\

OMe

TMS.OT1

f

v

0

100

h i

63 23

37 77

j

0

100

g

trans-2g

3g

-

In order to examine the reaction of cationic phosphenium complex having no amino substituent with phosphite, we attempted the preparation of [(bpy)(CO)sMo-

Scheme 2 s!

l+

1+

,

l+

{ POCMe2CMe20}]+ in the reaction of fac-[(bpy)(CO)~-

Mo{POCMe2CMe~O(OMe)}lwith BF3.OEt2. However, the product in this reaction was not the cationic phosphenium complex but a fluorinated complex, fac-[(bpy)-

(C0)~Mo{POCMe~CMe~0(F)}l. Thus, we sought another preparative method and found that a diphosphite complex, 4h, reacts with TMSeOTf to give cis-2h and trans-2h (eq 5 ) . The resonance pattern in the CO region +

$0 O,i,OMe TMSaOTf

+

____c

(5)

X trans-2h

4h

in the I3C NMR spectrum of the reaction mixture is consistent with the formation of trans-2h and cis-2h which corresponds to structure A type (vide supra): 221.78 ppm (t, JCP = 18.4 Hz) due to transdh and 220.15 ppm (dd, JCP = 25.7, 21.9 Hz) and 209.28 ppm (dd, JCP = 69.6, 19.5 Hz) due to c i s d h . Formation of [(phen)(CO)zLM{PN-N}l+and [(phen)(CO)zLM{PN-O}l+.phen analogues of trans2a (diamino-substituted) and trans-2g (monoaminosubstituted) were prepared according to eqs 6 and 7, +

s l +"3 OMe

cia-21

li

trans-2i

+ TMS-OTf

-

(7)

-

ClS.2

respectively. Changing bpy to phen (trans-2a trans2i and transdg trans-%) exerted no significant effect

trans2

on the 31P NMR data (chemical shifts and coupling constants). A single crystal of trans-2j was obtained; thus, it was subjected to X-ray analysis (vide infra). Cis and Trans Isomers of [(bpy)(CO)zLM(phosphenium)l+. As mentioned above, a meridional isomer of [(bpy)(C0)3M(phosphenium)l+reacts with a trivalent phosphorus compound (L) to give [(bpy)(CO)aLM(phosphenium)l+by CO/L exchange reaction. The product consists of the cis and trans isomers, and their ratio depends on the kind of M, the substituent on the phosphenium phosphorus, and L. Table 2 shows the isomer ratios. Before looking at the ratios, it is pertinent to check whether the two isomers are at equilibrium or not. The isolated trans-2a was redissolved in CH2C12, and the intensity change of resonances in the 31PNMR spectra was monitored. Immediately after the dissolution, trans-2a was the main component, but a small amount of cisSa was already present; the cis-2altrans-2a ratio was 6/94. The amount of cis-2a increased gradually with time at the cost of the amount of trans-2a, and after 48 h the apparent change ceased. The final ratio was 24/76. Therefore, it was confirmed that the trans isomer is in equilibrium with the cis isomer. Although cis-2 and trans-2 are in equilibrium, cis-2 may be formed first in the reaction of 1 with L (Scheme 2); a phosphenium ligand is a strong x acceptor, so three CO ligands in 1, especially two CO ligands mutually trans, are activated by it. Thus, one of the two CO ligands is readily replaced by L to give cis-2, which then isomerizes to trans-2 to reach the equilibrium. It should be noted here that a non-phosphenium complex, [(bpy)-

-

NU

-

1

(C0)3Mo{PN(Me)CH2CHzNMe(OMe)}l, does not undergo CO/L exchange reaction at room temperature. Now, let us consider the isomer ratios shown in Table 2. First, we compare the ratios for 2a, 2 d , and 2e t o elucidate the effect of a central metal on the equilibrium. The ratios for Mo (24176) and for W (22178) are almost equal, whereas the cis isomer for Cr was not detected. It is suggested that Cr, having a smaller radius than Mo or W (Cr = 1.25 A, Mo = 1.36 A, and W = 1.37 A), is too small to accept the two large ligands in the cis configuration. The P-P coupling constant for the Cr complex (transdd)is 91.6 Hz, whereas those for the Mo

Cationic Phosphenium Complexes

Organometallics, Vol. 14, No. 9, 1995 4177 c21

C25

C38

c1 12 C14 c14

Figure 1. ORTEP drawing of trans-2a (50% probability ellipsoids) showing the numbering system. All hydrogen atoms are omitted for clarity. and W complexes (trans-2aand trans-2e)are 274.7 and 268.6 Hz, respectively. It is suggested that the phosphite and/or the phosphenium may not closely approach the small Cr to make a sufficient bond due to the steric repulsion with the other ligands (bpy and two CO ligands) on the Cr. The ratio of 7/93 for 2c can be rationalized also by steric effects, if PPh3 is assumed to be bulkier than $N(Me)CH2CH2NMe(OMe). bpy and phosphite ligands serve as o-donors and also a weak n-acceptors, and the n-acidity is weaker for bpy than for phosphite.6cJ0 Therefore, the cis form of 2, where a phosphenium ligand being a strong n acid is trans to bpy, is electronically favored over the trans form, where a phosphenium ligand is trans to phosphite. This is embodied by the JPW values of 2e. JPW is 518.8 Hz for trans-2e but is 589.0 Hz for cis-2e, indicating that the phosphenium ligand is bonded more strongly to W for the cis form than for the trans form. n-Acidity of a phosphenium ligand seems stronger for 2 f than for 2a, so it is expected that the cisltrans ratio is greater for 2 f than 2a. Actually the equilibrium of 2 f is shifted toward the cis form. 2g has the phosphenium ligand electronically similar to that of 2 f , but cis2 g has not been detected. This may come from the bulkiness of a t-Bu group. cis-2j has also not been detected presumably for the same reason. The equilibrium is on a critical balance, but basically it can be said that the cis form is electronically and the trans form is sterically favored. Crystal Structures of trans-2a.OTf and truns2j.OTf.CH2Cl2. X-ray structure analyses of transSa-OTf and truns-2j*OTf.CH&l2 were undertaken. The ORTEP drawings of trans-2a and trans-@ are displayed in Figures 1 and 2, respectively. The crystal data and (10)Chisholm, M. H.; Connor, J. A,; Huffman, J. C.; Kober, E. M.; Overton, C. Inorg. Chem. 1984, 23, 2298.

@

c11

Figure 2. ORTEP drawing of trans-2j (50% probability ellipsoids) showing the numbering system. All hydrogen atoms are omitted for clarity. Table 3. Summary of Crystal Data for truns-2a.OTf and truns-2j.0TfCH&12 trans-2a.OTf formula fw cryst syst space group cell consts a,A

b, A

c,

A

a, deg

P, deg Y,deg

v, A3

z

Dcaicd,

g Cm-3

p , cm-'

cryst size, mm radiation (1,A) scan technique scan range, deg scan rate, deg min-' no. of unique data no. of unique data with F, > 3u(F0)

R RW

trans-2j.OTfCHzClz

C Z ~ H ~ I F ~ M O N ~C-~ ~ H ~ ~ C I ~ F ~ M O N ~ O&S 08P2S 722.50 889.53 monoclinic triclinic P1 P21n 19.155(2) 13.604(2) 11.798(2)

3042.6(7) 4 1.58 5.89 0.66 x 0.40 x 0.12 Mo Ka (0.710 73) w-20 3 < 30 < 55 6.0 6993 4601

10.230(3) 11.299(4) 17.043(4) 96.25(2) 99.82(2) 91.83(3) 1927(1) 2 1.39 5.25 0.55 x 0.26 x 0.05 Mo K a (0.710 73) w-20 3 < 20 < 55 6.0 6783 3373

0.050 0.059

0.099 0.062

98.22(1)

the selected bond distances and angles for trans-2wOTf and trans-2iOTf.CH2Cl2 are listed in Tables 3-5. The final atomic coordinates for non-hydrogen atoms are presented in Tables 6 and 7. Both complexes have pseudooctahedral geometries around the Mo atom, and two phosphorus atoms are coordinated to the Mo in mutually trans positions. The most interesting structural feature is that the bond distance of Mo-P(phosphenium) is significantly shorter than that of Mo-P(phosphite) for both complexes: for transda, Mo-P(phosphenium) = 2.254 A, Mo-P(phosphite) = 2.495 A; for trans-2j, Mo-P(phosphenium) =

Nakazawa et al.

4178 Organometallics, Vol. 14, No. 9, 1995 Table 4. Intramolecular Distances (A)and Angles (deg) with Esd's in Parentheses for truns-2a.OTf Mo-C1 Mo-C~ Mo-N32 Mo-P1 Mo-N31 Mo-P~ Pl-Nll Pl-Nl2 P2-021 P2-N21 P2-N22 01-c1

Bond Distances 1.953(6) 02-c2 1.966(6) 021-C25 2.244(4) Nll-C12 2.254(1) Nll-Cll 2.255(4) N12-Cl4 2.495(1) N12-Cl3 1.642(5) N21-C22 1.644(5) N21-C21 1.611(4) N22-C24 1.648(5) N22-C23 1.662(5) C12-Cl3 1.158(7) C22-C23

1.148(7) 1.44(1) 1.449(8) 1.46(1) 1.43(1) 1.453(8) 1.44(1) 1.46(1) 1.44(1) 1.44(1) 1.50(1) 1.49(1)

Bond Angles

Cl-Mo-C2 Cl-Mo-N32 C1-Mo-P1 Cl-Mo-N31 C1-Mo-P2 C2-Mo-N32 C2-Mo-Pl C2-Mo-N31 C2-Mo-P2 N32-Mo-Pl N32-Mo-N31 N32-Mo-P2 Pl-Mo-N31 Pl-Mo-P2 N31-Mo-P2 N11-P1-N12 N11-P1 -Mo N12-Pl-Mo 021-P2-N21 0 2 1-P2-N22 N21-P2-N22 0 2 1-P2-Mo

90.1(2) 98.9(2) 84.2(2) 169.3(2) 85.3(2) 168.2(2) 84.1(2) 98.3(2) 88.0(2) 104.3(1) 71.9(2) 85.2(1) 103.1(1) 166.85(5) 88.4(1) 92.6(2) 132.7(2) 132.7(2) 109.5(3) 107.6(2) 90.9(3) 108.2(2)

N21-P2-Mo N22 -P2 -Mo C25-021-P2 ClS-Nll-Cll ClB-Nll-Pl Cll-Nll-Pl C14-Nl2-Cl3 C14-Nl2-Pl C13-Nl2-Pl C22-N21-C21 C22-N21-P2 C21-N21-P2 C24-N22-C23 C24-N22-P2 C23-N22-P2 01-C 1-Mo 02-C2-M0 Nll-Cl2-Cl3 N12-Cl3-Cl2 N21-C22-C23 N22-C23-C22

120.6(2) 118.7(2) 121.1(4) 118.3(6) 116.3(4) 125.2(4) 118.6(5) 125.4(4) 115.9(4) 119.2(6) 117.1(5) 123.6(5) 120.0(6) 122.9(5) 116.4(5) 179.1(4) 178.3(5) 107.3(6) 107.6(5) 107.3(6) 107.8(7)

2.238 A,Mo-P(phosphite1 = 2.529 A. Normal Mo-P dative bond distances are reported to fall in the range 2.40-2.57 A.2 The observation that the Mo-P(phosphenium) bond is about 10% shorter than the Mo-P dative bond is consistent with double bond character in the phosphenium complex. Another structural feature of interest is concerned with the P-N bond distance. For both trans-2a and trans-2j, the P-N bond distances (A)in phosphenium and in phosphite ligands are almost equal: 1.642 (PlN l l ) , 1.644 (Pl-N12), 1.648 (P2-N21), and 1.662 (P2N22) for transda and 1.65 (Pl-N11) and 1.63 (P2N21) for trans-2j. This observation gives an insight into the role of an amino group on a phosphenium phosphorus (vide infra). Although the geometry around the coordinating phosphite phosphorus is pseudotetrahedral, the geometry around the phosphenium phosphorus is planar: the sum of angles at the phosphorus is 358.0' for trans-2a and 359.1' for trans-2j. For nitrogen atoms both in phosphenium and in phosphite ligands, the trigonal-planar geometry is indicated: the s u m of angles is 359.8' (Nll), 359.9' (N12), 359.9' (N211, and 359.3' (N22) for trans2a and 359.2' (N11) and 359.0' (N21) for trans-2j. The orientation of the phosphenium ligand is interleastesting. With trans-2a the Mo-Pl-Nll-Nl2 squares mean plane bisects the Cl-Mo-N32 and C2Mo-N31 angles, making a bisect angle of 47.07' with the N31-Mo-C1 vector, and with trans-2j the Mo-P1N l l - 0 1 1 least-squares mean plane bisects the C1Mo-C2 and N31-Mo-N32 angles, making a bisect angle of 38.85' with the N31-Mo-C1 vector.

Nll

30.05" trans-2a

trans-2j

Two cationic phosphenium complexes of transition metals have been characterized by X-ray diffraction so far.4a,5aOne of them is a Mo complex, [Mo(P(0Me)3}~{P(OMe)2}]PF64ain which the phosphenium ligand is oriented in the similar way; the least-squares mean plane makes a dihedral angle of 23.80' with that determined by Mo and four phosphorus atoms involving the phosphenium phosphorus. Muetterties mentioned that the phosphenium is oriented in such a way as to minimize repulsion with the trimethyl phosphite liga n d ~ In . ~the ~ case of trans-2a and trans-%,no significant steric repulsion exists between the phosphenium ligand and equatorial ligands (bpy (phen) and 2 CO ligands). So the phosphenium orientation found here seems to be inherent. The X-ray structure of trans-2j implies intramolecular CH-n interaction. The distance between C16 and the least-squares mean plane of the phen ring is 3.133 A, which is significantly shorter than the sum of the C-H bond distance (1.09 the van der Waals radius of H (1.20 and that of an aromatic ring (1.7 A).11 The CH-n interaction may be the reason for the different orientation (about 90') of the phosphenium ligands in trans-2a and in trans-2j. Double-Bond Character between a Transition Metal and a Phosphenium Phosphorus. A cationic phosphenium complex has been described in the resonance forms shown in Scheme 3. R2 corresponds to a transition-metal phosphenium complex where a plus charge is located on the phosphorus and a phosphenium cation coordinates to a transition metal through its lone pair. The bond between M and P in R2 can be seen as a dative bond. If a sufficient electron density flows from the filled d orbital of a transition metal into the vacant p orbital on the phosphorus, the plus charge would be located on a transition metal and the M-P bond would become a double bond (Rl). The n-electron donation to the empty p orbital of the phosphorus may occur not only from M but also from the two other substituents on the phosphorus (X and Y). These features are depicted in R3 and RA. In relation t o this study, it is useful to note that Arduengo and co-workers recently reported the preparation of the first isolable crystalline carbene (imidazol2-ylidene) and claimed that there is no convincing

A),

A),

R

m y Y R R 1midazol-2-ylidene

evidence that n-delocalization is an important feature of the carbene; that is, the nitrogen lone pairs do not (11)The van der Waals distance between two parallel benzene nuclei is usually a t least 3.4 A. ( a ) Fessner, W.-D.; Sedelmeier, G.; Spurr, P. R.; Rihs, G.; Prinzbach, H. J . Am. Chem. SOC.1987,109, 4626. (b) Vogtle, F.; Neumann, P. Top. Curr. Chem. 1974, 48,67.

Organometallics, Vol. 14, No. 9, 1995 4179

Cationic Phosphenium Complexes Table 5. Intramolecular Distances (A)and Angles (deg) with Esd’s in Parentheses for truns-2jOTf-CHzClz

atom

Bond Distances

Mo-C1 Mo-C2 Mo-P1 Mo-N.31 Mo-N32 Mo-P~ P1-011 Pl-Nll P2-021 P2-022 P2-N21

0141 02-c2 011-c12 021-c22 Q22-C27 Nll-Cll Nll-C13 N21-C23 N21-C21 Cll-c12 c21-c22

1 . W 1) 1.94(1) 2.238(4) 2.240(9) 2.256(9) 2.529(4) 1.602(7) 1.65(1) 1.59(1) 1.627(9) 1.63(1)

Mo P1 P2 01 02 021 N11 N12 N21 N22 N3 1 N32

Bond Angles -

Cl-Mo-C2 C1-Mo-P1 Cl-Mo-N31 C1-Mo-N32 C1-M o - P ~ C2-Mo-Pl C2-Mo-N31 C2-Mo-N32 C2-Mo-P2 Pl-Mo-N31 Pl-Mo-N32 Pl-Mo-P2 N3 1-Mo-N32 N31-Mo-P2 N32 -Mo -P2 Oll-Pl-Nll 011-P1-Mo N11-P1-Mo 021-P2-022 021-P2-N21

c1

022-P2-N21 021-P2-M0 022-P2-M0 N21-P2-Mo c12-011-Pl C22-021-P2 C27-022-P2 Cll-Nll-Cl3 Cll-Nll-Pl C13-Nll-Pl C23-N21-C21 C23-N21-P2 C21-N21-P2 Nll-Cll-ClB Oll-C12-Cll C22-C21-N21 c21-c22-021 01-C1-Mo 0 2 -C2-MO

84.1(5) 89.8(4) 169.4(5) 100.8(4) 90.0(4) 82.5(4) 100.8(4) 172.7(4) 81.5(4) 100.1(3) 102.9(3) 163.9(1) 73.6(3) 81.5(3) 93.0(3) 93.4(4) 118.8(3) 146.9(3) 103.4(5) 95.0(6)

c2 c11 c12 C13 C14 c21 c22 C23 C24 C25 C30 C31 C32 c33 c34 c35 C36 c37 C38 c39

s1

Scheme 3

S1’

n

R1

R2

R4

R3

show significant delocalization into either the carboncarbon double bond or the carbene center.12 The reason for the stability of the carbene is ascribed to the high electron density on the nitrogen flanking the carbene center to repel nucleophiles that might otherwise react with the carbenic carbon. Let us consider the role of amino groups in cationic phosphenium complexes. Studies on amino-substituted phosphorus compounds reveal that at least one nitrogen atom bonded to a phosphorus atom is sp2-hybridizedfor trivalent tricoordinated (D),13trivalent tetracoordinated /

D P -

\

D

M+PE

/

\

-Pt-

I

/

/

I F

Table 6. Positional Parameters and Equivalent Isotropic Thermal Parameters (A2)with Esd’s in Parentheses for trans-2aOTf

M G

n

(El4and F),15and pentavalent tetracoordinated (GI6and H)17 phosphorus. Therefore, it can be said that a nitrogen on a phosphorus shows N P n-donation (from a filled p orbital on N t o an empty d or a D* orbital on

-

(12) ( a ) Arduengo, A. J., 111; Harlow, R. L.; Kline, M. J . A m . Chem. SOC.1991, 113, 361. (b) Arduengo, J. A,, 111; Rasika Dias, H. V.; Dixson, D. A,; Harlow, R. L.; Klooster, W. T.; Koetzle, T. F. J . Am. Chem. SOC.1994, 116, 6812 and references cited therein.

F1 F2 F3 F3’ 0 41 042 043 044 C40 C40‘

X

0.13274(2) 0.11571(7) 0.13113(7) 0.1161(3) -0.0303(2) 0.0616(2) 0.0590(3) 0.1383(3) 0.1385(3) 0.1996(3) 0.1625(2) 0.2503(2) 0.1222(3) 0.0297(3) 0.0160(4) 0.0480(4) 0.0994(4) 0.1898(4) 0.0935(5) 0.1897(5) 0.2305(6) 0.2214(6) 0.0485(5) 0.1171(3) 0.1353(4) 0.2024(4) 0.2498(4) 0.2293(3) 0.2780(3) 0.3499(3) 0.3938(3) 0.3661(3) 0.2949(3) -0.1174 -0.0930 -0.0328 -0.1120 -0.0156 -0.1396 -0.1523 -0.0688 -0.1727 -0.0447 -0.0655 -0.0972

Y

z

-0.05071(3) -0.1403( 1) 0.07390(9) 0.1290(3) -0.0663(4) 0.1407(3) -0.2269(4) -0.1233(4) 0.0398(4) 0.1493(4) -0.1649(3) -0.0473(3) 0.0616(4) -0.0598(4) -0.2814(6) -0.2444(6) -0.1806(6) -0.0547(6) -0.0344(6) 0.0909(7) 0.1560(7) 0.2160(7) 0.2234(6) -0.2299(4) -0.2918(5) -0.2891(5) -0.2259(5) -0.1642(4) -0.0983(4) -0.0934(5) -0.0389(6) 0.0110(6) 0.0070(5) -0.4856 -0.5127 -0.3647 -0.4326 -0.5204 -0.3421 -0.5653 -0.4829 -0.4143 -0.5699 -0.4553 -0.4019

-0.27855(3) -0.4408(1) -0.1238( 1) -0.4433(4) -0.2905(4) -0.1550(4) -0.4869(4) -0.5687(4) 0.0114(4) -0.0942(4) -0.1416(3) -0.2299(3) -0.3828(5) -0.2877(4) -0.4161(7) -0.6093(6) -0.6608(5) -0.5960(6) 0.0538(7) 0.0916(6) 0.0241(8) -0.1771(9) -0.0852(9) -0.1048(5) -0.0144(6) 0.0436(6) 0.0068(5) -0.0866(4) -0.1362(4) -0.0938(6) -0.1505(7) -0.2473(7) -0.2830(6) -0.2692 -0.2447 -0.1440 -0.0572 -0.1070 -0.2288 -0.2376 -0.3464 -0.3030 -0.1713 -0.1337 -0.1716

B(eq)

P) to some extent irrespective of the valency and coordination number of the phosphorus atom or the existence of a bond between the phosphorus atom and a transition metal. If we say the n-donation is a “background n-donation”, there may be back-ground n-donation, in trans-2a and trans-2j, from N t o phosphenium (13)(a)Morris, E. D., Jr.; Nordman, C. E. Inorg. Chem. 1969, 8, 1673. (b) Cowley, A. H.; Dewar, M. J . S.; Jackson, W. R.; Jennings, W. B. J . Am. Chem. SOC.1970,92,1085. (c) Cowley, A. H.; Dewar, M. J. S.;Jackson, W. R.; Jennings, W. B. J . Am. Chem. SOC.1970, 92, 5206. (d) Csizmadia, I. G.; Cowley, A. H.; Taylor, M. W.; Wolfe, S.J . Chem. Soc., Chem. Commun. 1974, 432. (e) Remming, C.; Songstad, J. Acta Chem. Scand. 1978, A32, 689. (0 Cowley, A. H.; Mitchell, D. J.; Whangbo, M.-H.; Wolfe, S. J . A m . Chem. SOC.1979, 101, 5224. (g) R ~ m m i n gC.; , Songstad, J . Acta Chem. Scand. 1982, A36, 665. (14)Cowley, A. H.; Davis, R. E.; Remadna, K. Inorg. Chem. 1981, 20, 2146. (15) ( a ) Romming, C.; Songstad, J. Acta Chem. Scand. 1980, A34, 631. (b) Nevstad, G. 0.;Maartmann-Moe, K.; Remming, C.; Songstad, J . Acta Chem. Scand. 1985, A39, 523. (16) ( a ) Romming, C.; Songstad, J. Acta Chem. Scand. 1979, A33, 187. (b) R ~ m m i n gC.; , Iversen, A. J.;Songstad, J. Acta Chem. Scand. 1980, A34, 333. (c) Maartmann-Moe, K.; Remming, C.; Songstad, J. Acta Chem. Scand. 1982, A36, 757. (d) Romming, C.; MaartmannMoe, K.; Songstad, J . Acta Chem. Scand. 1984,A38,349. (e) Nevstad, G. 0.;R ~ m m i n gC.; , Songstad, J. Acta Chem. Scand. 1986, A39, 691. (17) ( a ) Nakazawa, H.; Kadoi, Y.; Mizuta, T.; Miyoshi, K.; Yoneda, H. J . Organomet. Chem. 1989,366,333. (b) Nakazawa, H.; Kadoi, Y.; Itoh, T.; Mizuta, T.; Miyoshi, K. organometallics 1991, 10, 766.

Nakazawa et al.

4180 Organometallics, Vol. 14, No. 9, 1995

Table 7. Positional Parameters and Equivalent Isotropic Thermal Parameters ( k ) with Esd's in Parentheses for truns-2jj.OTfCHzClz atom Mo P1 P2 01 02 011

021 022 N11 N21 N3 1 N32

c1

c2 c11 c12 C13 C14 C15 C16 c21 e22 C23 C24 C25 C26 C27 C30 C31 C32 c33 e34 e35 C36 c37 C38 c39 C40 C41 S F1 F2 F3 031 032 033 C50

c11 c12 C51

X

0.0271(1) 0.1035(3) -0.0947(3) -0.2094(9) -0.1539(8) O.OOlO(7) -0.050(1)

-0.2504(8) 0.2348(9) -0.090(1) 0.1885(8) 0.1588(9) -0.115(1)

-0.083(1) 0.203(1) 0.060(1) 0.378(1) 0.431(1) 0.456(1) 0.391(1) -0.040(2) -0.024(2) -0.121(2) 0.006(2) -0.172(2) -0.212(2) -0.344( 1) 0.208(1) 0.298(1) 0.370(1) 0.358(1) 0.265(1) 0.251(1) 0.334(1) 0.326(1) 0.237(2) 0.152(1) 0.434(1) 0.422(1) -0.3532(5) -0.382(2) -0.195(1) -0.358(1) -0.274(2) -0.483(1) -0.318(1) -0.310(3) 0.2899(5) 0.1130(8) 0.262(2)

Y

2

-0.2342(1) -0.2602(3) -0.2595(3) -0.1022(8) -0.4572(7) -0.3034(7) -0.3769(8) -0.2902(9) -0.2740(8) -0.177(1) -0.3146(8) -0.0807(8) -0.152(1) -0.375(1) -0.338(1) -0.322(1) -0.24% 1) -0.156(1) -0.354(1) -0.178(1) -0.246(2) -0.365(2)

0.09393(7) -0.0219(2) 0.2088(2) 0.0128(6) 0.0156(5) -0.1028(4) 0.2479(6) 0.1704(5) -0.0662(5) 0.2942(7) 0.1742(6) 0.1636(6) 0.0443(7) 0.0467(7) -0.1472(8) -0.1741(8) -0.0307(7) -0.0826(9) -0.031(1) 0.0528(9) 0.364(1) 0.333(1) 0.310(1) 0.347(1) 0.234(1) 0.366(1) 0.2152(9) 0.1793(8) 0.2362(9) 0.2946(9) 0.2932(8) 0.2325(6) 0.2239(8) 0.2752(9) 0.2584(9) 0.1983(9) 0.1494(8) 0.3506(9) 0.3393(9) 0.3573(3) 0.5029(7) 0.482(1) 0.4523(6) 0.3191(9) 0.3328(9) 0.3695(6) 0.452(2) 0.4696(3) 0.3972(5) 0.450(1)

-0.050(1)

0.020(2) -0.002(2) -0.035(1) -0.325(1) -0.429(1) -0.474(1) -0.394(1) -0.272(1) -0.234(1) -0.111(1)

-0.024(1) 0.094(1) 0.122(1) 0.033(1) -0.181(2) -0.064(1) 0.3647(5) 0.378(1) 0.329(2) 0.207(1) 0.297(2) 0.344(1) 0.485(1) 0.327(2) 0.1956(5) 0.3533(6) 0.341(1)

B(eq)

For example, the Mo-P bond distances become shorter in the order 2.254 A (trans-2a),2.238 A (trans-2j))and 2.229 A ([Mo{(P(OMe)~}~(P(OMe)z)l+), which corresponds to the replacement of the substituent atoms on the phosphenium phosphorus from N to 0. And the P-P coupling constants become greater on going from 2a to 2f and to 2h for both the cis and trans isomers, cis-2a (42.7 Hz) cis9f (54.9 Hz) cis9h (58.0 Hz), and trans-2a (274.7 Hz) trans-2f (326.6 Hz) trans2h (369.2 Hz). These tendencies indicate that an 0-substituent rather than an N-substituent makes an M-P(phosphenium) double bond stronger. The reason may come from the greater electronegativity of 0 than that of N. That is, the o-interaction, not n-interaction, between phosphenium phosphorus and its substituents (X and Y in Scheme 3) may affect the M-P double-bond character to some extent.

- -

-

-

Experimental Section General Remarks. All reactions were carried out under an atmosphere of dry nitrogen by using Schlenk tube techniques. All solvents were purified by distillation: toluene, p-xylene, and hexane were distilled from sodium metal, and CH2Clz and CH3CN were distilled from P z O ~ All . solvents were stored under a nitrogen atmosphere. BF3.OEt2 and TMSOTf ld,6cle,6cand were distilled prior to use. Complexes la,6b,c li,6bwere prepared by the literature methods. IR spectra (cm-') were recorded on a Shimadzu FTIR-8100 spectrometer. JEOL PMX-60, EX-270, and EX-400 instruments were used to obtain 'H, 13C,and 31PNMR spectra. 'H and 13C NMR data were referenced to (CH&Si, and 31PNMR data were referenced to 85% H3P04. Preparation of the 2a-e and 2i Complexes. A solution of the phosphenium complex (la, Id, le, l i ) in CHzClz (10 mL) was cooled to -78 "C, and an equimolar amount of the corresponding phosphite or phosphine was added. The solution was then allowed to warm to room temperature. The resulting solution was subjected to spectroscopic measurements. IR (YCO,in CH2C12): 1912, 1834 for 2a; 1912, 1835 for 2b; 1909, 1831 for 2c; 1904, 1827 for 2d, 1906, 1825 for 2e; 1913, 1836 for 2i. r

Isolation of trans-2a. A solution offac-[Mo(bpy)(C0)3{PNI

(Me)CHzCHzNMe(OMe)}] (210 mg, 0.43 mmol) in CHzClz (10 mL) was cooled to -78 "C, and TMSeOTf (78 pL, 96 mg, 0.43 mmol) was added. After being warmed to room temperature,

phosphorus as well as to phosphite phosphorus. Howthe solution was again cooled to -78 "C, and then PN(Me)ever, from the X-ray structures of trans-2a and transCHzCHzNMe(0Me) (65 pL, 66 mg, 0.44 mmol) was added. 2j, extra n-donation like in R3 and R4 may not exist. After the solution was allowed to warm to room temperature, The P-N bond lengths observed in our system are hexane (16 mL) was added. Keeping the solution in a obviously longer than those of [P(N-i-Pr~)~1[AlC1~1(1.613 refrigerator resulted in the formation of reddish orange A); transition-metal-free phosphenium has been procrystals, which were collected by filtration, washed with posed t o involve extra z-donation.ls The role of the hexane, and dried in vacuo to give trans-2a.OTf(214 mg, 0.30 amino groups on the phosphenium phosphorus may be, mmol, 68%). Anal. Calcd for C Z Z H ~ ~ F ~ M O N & C, ~ P36.58; ZS: H, 4.32; N, 11.63. Found: C, 36.12; H, 4.63; N, 11.68. IR (YCO, as is proposed for the imidazol-2-ylidene system, to in CH2Clz): 1912, 1834. 31PNMR (6,in CHzClZ): 130.10 (d, protect the approach of a nucleophile to phosphenium phosphorus by high pn lone pair density flanking the phosphenium center. 274.7 Hz, 6N(Me)CH&H2NMe). 'H NMR (6, in CD2C12): 2.32 The substituents on the phosphenium phosphorus (d, J = 11.7 Hz, 6H, PN(CH3)CH&HzN(CH3)(0Me)), 2.82 (d, affect the M-P(phosphenium) double-bond character. (18)(a) Thomas, M. G.; Schultz, C. W.; Parry, R. W. Inorg. Chem. 1977,16, 994. (b) Cowley, A. H.; Cushner, M. C.; Szobota, J. S. J. Am. Chem. SOC.1978,100, 7784. ( c ) Cowley, A. H.; Cushner, M. C.; Lattman, M.; Mckee, M. L.; Szobota, J. S.; Wilburn, J. C. Pure Appl. Chem. 1980,52,789. (d) Trinquler, G.; Marre, M.-R. J . Phys. Chem. 1983,87,1903

-

r-

J = 11.7 Hz, 6H, PN(CH~)CHZCH~N(CH~)), 2.87 (m, 2H, PN-

-

(Me)CHzCHzNMe(OMe)),3.10 (d, J = 10.7 Hz, 3H, OCH3), 3.17 I

(m, 2H, PN(Me)CHzCHzNMe(OMe)),3.53 (d, J = 6.4 Hz, 4H, PN(Me)CHzCH2NMe), 7.49-9.10 (m, 8H, bpy). 13C NMR (6,

-

Organometallics, Vol. 14,No.9, 1995 4181

Cationic Phosphenium Complexes

,

3.62 ~ ) )(m, , lH, PN(t-Bu)CH2CHzOin CDzC12): 32.50 (d, J = 12.8 Hz, PN(CH~)CHZCH~N(CH~)- P N ( ~ - B u ) C H ~ C H ~ O ( O M (OMe)),33.85 (d, J = 17.2 Hz, PN(CH~)CH~CHZN(CH~)), 51.57 (d, J = 4.0 Hz, OCH3), 52.64 (m, NCHz), 123.62 (s, bpy), 125.78 (s, bpy), 139.18 (s, bpy), 153.38 (9, bpy), 155.30 (s, bpy), 224.39 (t, J = 18.2 Hz, CO). Preparation of I f and 2f. A solution of M0(bpy)(C0)~

4.06 (OMe)),3.66 (quart, J = 7.3 Hz, 2H, PN(~-BU)CH~CHZO),

(1000 mg, 2.75 mmol) and PN(MeICHzCHzO(0Me) (0.48 mL, 520 mg, 3.86 mmol) in toluene (35 mL) was refluxed for 1 h. Standing the reaction mixture for 1 night a t room temperature yielded a reddish purple powder, which was collected by filtration, washed with hexane, and then dried in vacuo to give

1

fac-[Mo(bpy)(C0)3{PN(Me)CH~CH~0(OMe)}l (730 mg, 1.55

Hz, PN(C(CH3)3}CHzCH20(0Me)), 55.93 (d, J = 6.1 Hz, PN{C-

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mmol, 56%). Anal. Calcd for C ~ ~ H ~ ~ M O NC,~43.33; O ~ P H, : 3.85; N, 8.92. Found: C, 43.24; H, 4.07; N, 8.94. IR (YCO,in CH2C12): 1924, 1827, 1794. 31PNMR (8, in CH2C12): 157.00 (s). 'H NMR (6, in acetone-&): 2.53 (d, J = 10.6 Hz, 3H, NCHd, 2.72-3.50 (m, 2H, NCHz), 3.21 (d, J = 10.4 Hz, 3H, OCH3), 3.51-4.56 (m, 2H, OCH2), 7.34-9.26 (m, 8H, bpy). Procedures similar to those for l a and 2 a were applied t o

(m, l H , PN(t-Bu)CHzCHzO(OMe)),4.41 (tdd, J = 7.3, 7.3, 2.3

Hz, 2H, PN(t-Bu)CH2CHzO), 7.47-8.97 (m, 8H, bpy). 13C NMR (6, in CD2ClZ): 28.56 (d, J = 3.7 Hz, +N{C(CH3)3}CHzCHzO(OMe)), 29.63 (d, J = 4.9 Hz, ~N{C(CH&}CH~CHZO), I

I

I

43.95 (s, PN{C(CH~)~}CHZCHZO(OM~)), 46.77 (s, PN{C(CH3)3}I

CHzCHzO), 50.30 (d, J = 12.2 Hz, OCH3), 52.04 (d, J = 7.4 I

I

I

, (CH3)3}CH&H20), 67.04 (d, J = 9.8 Hz, PN{C(CH3)3}-

I

I

CH&HzO(OMe)),68.04 (d, J = 8.5 Hz, dN{C(CH3)3}CH2CH20), 123.27 (s, bpy), 123.47 (s, bpy), 125.37 (s, bpy), 125.50 (s, bpy), 139.21 (s, bpy), 153.04 (s, bpy), 153.12 (s, bpy), 154.72 (s, bpy), 154.86 (s, bpy), 223.63 (t, J = 18.3 Hz, CO), 223.97 (t, J = 18.3 Hz, CO). Due to the chirality of the phosphorus atom, bpy carbons ( a resonance a t 139.21 ppm is not separated obtain I f from fac-[Mo(bpy)(C0)~{PN(Me~CH~CH~0~0Me~}l cleanly) and two CO carbons are diastereotopically observed. I Preparation of 4 h and 2h. A solution of Mo(bpy)(C0)4 and BF3-OEt2, and to obtain 2f from If and PN(Me)CHz-

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1

CH20(0Me). IR ( V C O , in CH2C12): 1915, 1839 for 2f. Preparation of 3g and 2g. A solution of Mo(bpy)(CO)4 (2014 mg, 5.53 mmol) in CH3CN (120 mL) was refluxed for 5 h to give Mo(bpy)(CO)3(NCCH3)(IR (YCO): 1909, 1789). The solvent was removed under reduced pressure. The residue was

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dissolved in THF (70 mL), and PN(t-Bu)CHzCHzO(OMe)(1.23 mL, 1280 mg, 7.21 mmol) was added to the solution. After being refluxed for 1 h, the solution was concentrated to ca. 30 mL. Addition of hexane (80 mL) resulted in the formation of a reddish purple powder, which was washed with hexane several times and dried in vacuo to give 3g (2763 mg, 5.37 mmol, 97%). Anal. Calcd for CzoH24MoN305P: C, 46.79; H, 4.68; N, 8.19. Found: C, 47.12; H, 4.72; N, 7.81. IR (YCO, in CHzC12): 1920, 1819, 1793. 31P NMR (8, in CHzClZ): 149.24 (SI. 'H NMR (6, in acetone-&): 1.17 (s, 9H, t-Bu), 2.82 (m, lH, NCHz), 3.18 (m, lH, NCHz), 3.21 (d, J = 10.7 Hz, 3H, OCH3), 3.35 (m, lH, OCHz), 3.94 (m, lH, OCH2), 7.50-9.15 (m, 8H, bpy). 13C NMR (6, in CDzClZ): 29.11 (d, J = 4.9 Hz, NC(CH&), 44.24 (s, NC(CH&), 50.02 (d, J = 8.5 Hz, OCH3), 51.93 (d, J = 7.3 Hz, NCHz), 66.97 (d, J = 9.8 Hz, OCH2), 121.63 (s, bpy), 121.87 (s, bpy), 124.62 (s, bpy), 124.74 (s, bpy), 136.55 (s, bpy), 136.60 (s, bpy), 153.04 (s, bpy), 153.15 (s, bpy), 155.04 (s, bpy), 155.15 (s, bpy), 217.24 (d, J = 62.2 Hz, CO trans to P), 228.42 (d, J = 13.4 Hz, CO cis to P), 228.48 (d, J = 12.2 Hz, CO cis to P). Due to the chirality of the phosphorus atom, bpy carbons and two CO carbons cis to P are diastereotopically observed.

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(2103 mg, 5.78 mmol) and POCMenCMezO(OMe1 (2.95 mL, 3080 mg, 17.30 mmol) in p-xylene (120 mL) was refluxed for 14.5 h. ARer the solvent was removed under reduced pressure, the residue was washed with hexane several times to give 4 h as a bluish purple powder (2104 mg, 3.17 mmol, 55%). Anal. 47.00; H, 5.76; N, 4.22. Calcd for C ~ ~ H ~ ~ M O N ~C,O & : Found: C, 47.10; H, 5.82; N, 4.08. IR ( V C O , in CH2C12): 1842, 1761. 31PNMR ( 6 , in CHzC12): 176.11 (s). 'H NMR (6, in acetone-&): 0.68 (s, 12H, CH3), 1.17 (s, 12H, CH3), 3.54 (t, J = 5.7 Hz, 6H, OCH3), 7.39-9.15 (m, 8H, bpy). I3C NMR (6, in acetone-&): 25.48 (s, C(CH&), 25.70 (s, C(CH3)2),51.32 (s, OCH3), 84.73 (t, J = 3.7 Hz, C(CH3)2), 122.68 (s, bpy), 124.85 (5, bpy), 135.94 (s, bpy), 153.04(s,bpy), 155.65 (s, bpy), 231.12 (t, J = 15.3 Hz, CO). A solution of 4 h (261 mg, 0.39 mmol) in CH2C12 (10 mL) was cooled to -78 "C, and TMSOTf (70pL, 86 mg, 0.39 mmol) was added; then the solution was allowed to warm to room temperature. The resulting solution was subjected to IR and 31PNMR measurements, showing the formation of trans-2h. IR (YCO,in CH2C12): 1958, 1887. Preparation of 3j and 2j. A solution of M ~ ( p h e n ) ( C O ) ~ (1384 mg, 3.57 mmol) in CH3CN (100 mL) was refluxed for 4 h to give Mo(phen)(CO)3(NCCHs)(IR (VCO): 1909, 1789 cm-'). The solvent was removed under reduced pressure. The residue

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was dissolved in THF (70 mL), and PN(t-Bu)CH&HzO(OMe) (760 pL, 790 mg, 4.46 mmol) was added to the solution. After being refluxed for 1 h, the solution was concentrated to ca. 35 mL. Addition of hexane (100 mL) resulted in the formation I A solution of 3g (307 mg, 0.60 mmol) and PN(t-Bu)CHzof a reddish purple powder, which was washed with hexane 1 several times and dried in vacuo to give 3j (1824 mg, 3.39 CH20(0Me) (100 ,uL, 104 mg, 0.59 mmol) in CHzClz (10 mL) mmol, 95%). Anal. Calcd for C ~ ~ H ~ ~ M O N C,~49.17; O ~ P H, : was cooled to -78 "C, and TMS-OTf (110 ,uL,-l35 mg, 0.61 4.50; N, 7.82. Found: C, 49.24; H, 4.36; N, 7.75. IR ( V C O , in mmol) was added. The solution was then allowed to warm to CH2C12): 1920, 1820, 1793. 31PNMR (6, in CH2C12): 149.46 room temperature. Addition of hexane (5 mL) and toluene (8 (s). 'H NMR (8, in acetone-&): 1.02 (s, 9H, t-Bu), 2.58 (m, mL) and cooling the solution resulted in the formation of 2H, NCHz), 3.10 (d, J = 10.3 Hz, 3H, OCH3), 3.88 (m, 2H, reddish purple crystals, which was washed with hexane OCHz), 7.88-9.52 (m, 8H, phen). 13C NMR (6, in CDzC12): several times and dried in vacuo to give trans-2gOTf.2CH229.02 (d, J = 4.9 Hz, NC(CH3)3),44.19 (s, NC(CH3)3), 50.50 Clz (388 mg, 0.41 mmol, 68%). Anal. Calcd for Cz~H41C14F3(d, J = 8.6 Hz, OCH3), 51.84 (d, J = 7.3 Hz, NCHZ),66.94 (d, MoN4O8P2S: C, 35.39; H, 4.35; N, 5.90. Found: C, 35.02; H, J = 9.7 Hz, OCHz), 123.95 (s, phen), 124.10 (s, phen), 127.06 4.44; N, 6.41. IR ( V C O , in CH2Clz): 1932, 1853. 31PNMR (6, (s, phen), 127.13 (s, phen), 129.88 (s, phen), 130.04 (s, phen), in CHZC12): 139.89 (d, J p p = 320.5 Hz, PN(t-Bu)CHzCHzO(O135.60 (s, phen), 146.65 (s, phen), 146.70 (s, phen), 152.75 (d, J = 2.4 Hz, phen), 152.90 (d, J = 2.4 Hz, phen), 217.26 (d, J Me)),227.52 (d, J p p = 320.5 Hz, PN(t-Bu)CH&HzO). 'H NMR = 62.3 Hz, CO trans to P), 228.36 (d, J = 13.4 Hz, CO cis to P), 228.47 (d, J = 13.5 Hz, CO cis to P). Due to the chirality (6, in CD2C12): 1.15 ( s , 9H, PN{C(CH&}CHzCH26(0Me)), 1.19 I of the phosphorus atom, phen carbons (a resonance at 135.60 (s, 9H, $N{C(CH&}CH2CH2b), 2.89 (m, l H , PN(t-Bu)CHzppm is not separated cleanly) and two CO carbons cis to P are I diastereotopically observed. CH20(0Me)), 3.21 (d, J = 11.2 Hz, 3H, POCHs), 3.23 (m, lH,

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Nakazawa et al.

4182 Organometallics, Vol. 14, No. 9, 1995 I trans-2j.OTfCHzClz

were individually sealed under N2 in a thin-walled glass capillary, mounted on a Mac Science MXC3 1 diffractometer, and irradiated with graphite-monochromated CHzO(0Me) (56 pL, 58 mg, 0.33 mmol) in CHzClz (10 mL) was Mo Ka radiation (A = 0.710 73 A). Unit-cell dimensions were cooled to -78 "C, and TMSOTf(60pL, 74 mg, 0.33 mmol) was obtained by least squares from the angular setting of 30 added. After the solution was allowed t o warm t o room accurately centered reflections with 10" < 28 < 25". Reflection temperature, hexane (16 mL) was added. Keeping the solution intensities were collected in the usual manner at 25 "C, and in a refrigerator resulted in the formation of reddish orange three check reflections measured after every 100 reflections crystals, which were collected by filtration, washed with showed no decrease in intensity. P21h and Pi were selected hexane, and dried in vacuo to give truns-2j.OTfCH2Cl2 (251 N ~space O B -groups for trans-2a.OTf and trans-2jOTf.CH2Clz, mg, 0.28 mmol, 86%). Anal. Calcd for C ~ ~ H ~ ~ C ~ ~ F ~ M O as respectively, which led to successful refinements. P2S: C, 39.16; H, 4.42; N, 6.30. Found: C, 39.20; H, 4.28; N, 6.76. IR (YCO,in CH2Clz): 1933, 1855. 31PNMR (6, in CHzThe structures were solved by direct methods with the program Monte Carlo-M~1tan.l~For truns-2a.OTf, the OTf Clz): 140.41 (d, J p p = 317.4 Hz, PN(t-Bu)CH2CH20(OMe)), was disordered in very close positions. Even if the OTf was I 'H NMR (6, located in the two positions in a certain probability, they were 228.10 (d, J p p = 317.4 Hz, PN(~-Bu)CH~CHZO). fused after refinement. Therefore, the OTf was fixed in the in CD2C12): 1.00 (s, 9H, PN{C(CH3)3}CHzCHzO(OMe)), 1.12 two positions estimated from difference Fourier maps with a I respective weight of 0.5. The positions of hydrogen atoms for (s, 9H, $N{C(CH~)~}CHZCHZ~), 2.65 (m, l H , PN(t-Bu)CHztrans-2a.OTf were determined from subsequent difference CHZO(OMe)), 3.09 (d, J = 11.2 Hz, 3H, OCH3), 3.12 (m, l H , Fourier maps, and those for truns-2j*OTfiCH2Cl~were calculated by assuming idealized geometries. Absorption and PN(t-Bu)CHzCHzO(OMe)),3.50 (m, l H , PN(t-Bu)CHzCH20extinction corrections were then applied,20z21 and several cycles (OMe)), 3.66 (quart, J = 7.3 Hz, 2H, PN(t-Bu)CHzCHzO),3.98 of a full-matrix least-squares refinement with anisotropic temperature factors for non-hydrogen atoms led to final R, (m, l H , PN(t-Bu)CHzCHzO(OMe)),4.42 (quint, J = 7.1 Hz, 2H, values of 0.059 and 0.062 for trans-2aOTfand truns-aOTfCH2PN(t-Bu)CH&H20), 7.87-9.35 (m, 8H, phen). 13C NMR (6, Clz, respectively. All calculations were performed on a Titan I 750 computer using the program system Crystan-G.lg in CDzC12): 28.18 (s, ~ N { C ( C H ~ ) ~ } C H Z C H ~ O ( O 29.39 M ~ )(s, ),

A solution of 3j (178 mg, 0.33 mmol) and PN(t-Bu)CHZ-

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,

bN(C(CH3)3}CH2CHzO), 43.63 (s, $N{C(CH3)3}CHzCHz~OMe)), 46.58 (s,PN{C(CH3)3}CHzCHzO),50.12 (d, J = 12.2 Hz, OCHd, 51.62 (d, J = 6.1 Hz, $N{CCH3)3}CHzCHzO(OMe)),55.67 (d, J = 4.9 Hz, f"{C(CH3)3}CHzCHzb), 66.83 (d, J = 9.8 Hz, I

I

dN{C(CH3)3}CH~CH20(0Me)), 67.99 (d, J = 8.5 Hz, PN{C(CI

Acknowledgment. This work was supported by the Grant-in-Aid for Scientific Research on Priority Area of Reactive Organometallics No. 06227250 from the Ministry of Education, Science, and Culture of Japan.

H3)3}CH2CH20), 124.33 (6, phen), 124.51 (s, phen), 127.15 (6, phen), 127.24 (s, phen), 129.79 (5, phen), 130.03 (S, Phen), 138.09 (s, phen), 145.23 (s, phen), 145.42 (8,phen), 153.13 (S, phen), 223.46 (t, J = 22.0 Hz, CO), 223.79 (t, J = 22.0 Hz, 0). Due to the chirality of the phosphorus atom, phen carbons (two resonances at 138.09 and 153.13 ppm are not separated cleanly) and two CO carbons are diastereotopically observed. X-ray Structure D e t e r m i n a t i o n f o r truns-2a.OTf and trans-2j.OTECH&lz. Single crystals of trans-2a.OTf and

S u p p o r t i n g I n f o r m a t i o n Available: Additional structural data for complexes trans-2aOTf and truns-2j-OTfCH2Clz, including tables of thermal parameters and distances and angles (7 pages). Ordering information is given on any current masthead page. OM950287M (19)Furusaki, A. Acta Crystallogr., Sect. A 1979, A35, 220. (20) Katayama, C . Acta Crystallogr., Sect. A 1986, A42, 19. (21) Coppens, P.;Hamilton, W. C . Acta Crystallogr., Sect. A 1970, A26, 71.