Preparation of cis-Mo(CO)2(Ph2P(CH2)nPPh2)2 (n = 1, 2, 3) from cis-dicarbonylbis(norbornadiene)molybdenum and crystal structure of [cis-Mo(CO)2(Ph2P(CH2)3PPh2)2]

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Journal of Organometallic Chemistry 561 (1998) 153 – 155

Formation of isocyanide complexes via acylation of diaminocarbene

complexes

Jian-Yang Cho

a

_{, Chi-Li Chen}

a

_{, Tung-Ying Hsieh}

a

_{, Fu-Mei Kiang}

b

_{, Gene-Hsiang Lee}

a

_,

Shie-Ming Peng

a

_{, Shiuh-Tzung Liu}

a,

_*

a_{Department of Chemistry, National Taiwan Uni}_{6ersity, Taipei, Taiwan}₁₀₆_{, ROC} b_{Department of Pharmacy, China Medical College, Taichung, Taiwan, ROC}

Received 16 December 1997; received in revised form 25 February 1998

Abstract

Treatment of cyclic diaminocarbene tungsten complexes (CO)5WCNRCH2CH2N ¸¹¹¹¹¹¹¹º

H [R = Ph, Et] with acylating agents resulted in the formation of isocyanide complexes via the cleavage of C – N bond. Crystal structure of (CO)5WCN(CH2)2N(Ph)COPh 2a

1. Introduction

The diaminocarbene species known as a ‘bottle-able carbene’ has received much attention recently [1 – 5]. Such carbenes can be considered typical nucle-ophilic ligands which allow them to become a good p-donor towards various metal and non-metal ions [5 – 8]. In the structural analysis, the distance of C (car-bene) – N appears to be intermediate between typical single-bond and double-bond lengths (Scheme 1), in-dicating the resonance stabilization by the better donor nitrogen atoms. It is also known that aminocarbene complexes with primary or secondary amine moieties can react with acylating agents in various fashions. For example, aminocarbene (CO)5CrC(NH2)R can be converted to 2-azaallenyl

complexes via the reaction of NH2 group with acyl

chloride [9], whereas the N-acylated product was ob-tained when (CO)5CrC(NHR)Ar reacted with acetic

anhydride in the presence of base [10]. In the previ-ous work, we were able to prepare the stable di-aminocarbene group 6 metal complexes 1 with secondary amine moiety in the molecule [11]. Here we report the reaction of cyclic diaminocarbene com-plexes with acylating agents to yield the correspond-ing isocyanide species.

2. Results and discussion

Instead of granting the N-acylated carbene product, treatment of diaminocarbene 1a with benzoyl chloride in the presence of pyridine at reflux for 12 h resulted in the formation of the isocyanide complex 2a (Scheme 2). Scheme 1.

* Corresponding author. Fax: + 886 223636359.

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J.-Y. Cho et al./Journal of Organometallic Chemistry561 (1998) 153 – 155

154

Scheme 2.

Scheme 3.

complexes. Both reactions of 1b with benzoyl chloride and 1b with acetic anhydride provide the corresponding isocyanide complexes 2b and 2c, respectively [14]. Other acylating agents such as acetyl bromide or acetyl chloride provide the same result whereas di-tert-butyl dicarbonate (t-BuOCO)2O does not react with diaminocarbene

com-plexes at all. In the previous study, we have found that the deprotonation of 1a or 1b with sodium hydride accompa-nied with alkylation yielded the N-alkylated carbene complexes [11]. However, deprotonation of 1a by n-butyllithium followed by the treatment of benzoyl chlo-ride at r.t. resulted in the recovery of the starting material, whereas the isocyanide product 2a was obtained when the reaction was carried out at refluxing temperature.

It is reported by Do¨tz and coworkers that the N-acy-lated aminocarbene complexes can be obtained effec-tively by the treatment of carbene complexes with acylating agents in the presence of dimethylaminopy-ridine(DMAP) as the catalyst [10]. However, attempts to prepare the N-acylated diaminocarbene of 1 under Do¨tz conditions or even under refluxing THF solution failed and the starting material was recovered. This result indicates that the reactivity of diaminocarbene complexes is quite different from a simple aminocarbene species such as (CO)5CrC(NHR)Ar.

Formation of the isocyanide complex is presumably via the ring-opening of the cyclic carbene to form an isocyanide intermediate 3 followed by the acylation of secondary amine to yield the product (Scheme 3). The first step involves the cleavage of C – N bond, which is the reversed process of the addition of amine to isocyanide moiety, a known approach to prepare diaminocarbenes [11]. Unfortunately, it is not possible to detect the intermediate 3 via monitoring the sample of 1 by NMR spectrometer even at higher temperature indicating that the carbene species is thermodynamically more stable than the isocyanide form. However, the amine moiety of 3 is once acylated, the nitrogen atom becomes less nucleophilic and is not able to form the carbene species. In this investigation, the available data indicates that the stable class of diaminocarbene complex can undergo the cleavage of C – N bond thermally to form the isocyanide functionality.

Acknowledgements

We thank the National Science Council of the Re-public of China for financial support (NSC87-2113-M002-10).

Complex 2a was characterized by both spectral and X-ray crystal structural analyses. The infrared spectrum for 2a showed a characteristic band at 2176 cm− 1_{, which is}

consistent with the coordinated isocyanide stretching absorption, and metal-carbonyl stretching frequencies at 2069, 1947 cm− 1_{. The}13_{C-NMR chemical shift at}d 144.6

is typical for the coordinated isocyanide which provides another information of the structure proposed. Neverthe-less, the structure of 2a was further confirmed by single-crystal X-ray diffraction and the ORTEP plot is presented in Fig. 1 [12].

As expected, the tungsten atom is in an octahedral environment, since it is bound to an isocyanide and five carbonyl ligands. The W-ligands distances are similar to those reported for analogous (CO)5WCNR species [13].

All bond distances and bond angles are in normal ranges as illustrated in Fig. 1. The distance of tungsten to isocyanide ligand [W-C6 2.120(6) A˚ ] is similar to that of CH3C[CH2NCW(CO)5]3[2.08(2) A˚ ] ([13]a). The distance

of carbonyl ligand trans to isocyanide [W-C3 2.001(8)] appears to be shorter than those cis to it. The distance of C6-N1 [1.136(8) A˚ ] is attributed to the CN in the coordinated isocyanide.

Conversion of diaminocarbene to the isocyanide com-plex appears to be a trend in such tungsten carbene

Fig. 1. ORTEP Plot of 2a. W-C6 2.120(6), W-C1 2.028(9), W-C2 2.027(8), W-C3 2.001(8), W-C4 2.041(9), W-C5 2.031(8), W-C6-N1 177.8(5), C1-W-C6 90.0(3), C6-W-C3 179.3(3).

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J.-Y. Cho et al./Journal of Organometallic Chemistry561 (1998) 153 – 155 155

References

[1] N. Wiberg, Angew. Chem. Int. Ed. Engl. 7 (1968) 766. [2] A.J. Arduengo III, J.R. Goerlich, W.J. Marshall, J. Am. Chem.

Soc. 117 (1995) 11027, and references therein.

[3] R.W. Alder, P.R. Allen, M. Murray, A.G. Orpen, Angew. Chem. Int. Ed. Engl. 35 (1996) 1121.

[4] D. Enders, K. Breuer, J. Runsink, J.H. Teles, Liebigs Ann. (1996) 2019.

[5] M. Regitz, Angew. Chem. Intl. Ed. Engl. 35 (1996) 725, and references therein.

[6] (a) U. Kernbach, M. Ramm, P. Luger, W.P. Fehlhammer, Angew. Chem. Int. Ed. Engl. 35 (1996) 310. (b) N. Kuhn, H. Bohnen, J. Fahl, D. Bla¨ser, R. Boese, Chem. Ber. 129 (1996) 1579. (c) D. Enders, H. Gielen, G. Raabe, J. Runsink, J. H. Teles, Chem. Ber. 129 (1996) 1483. (d) A. J. Arduengo III, R. Krafczyk, W. J. Marshall, R. Schmutzler, J. Am. Chem. Soc. 119 (1997) 3381. (e) H. Schumann, M. Glanz, J. Winterfeld, H. Hemling, N. Kuhn, T. Kratz, Chem. Ber. 127 (1994) 2369. (f) J.A. Chamizo, P.B. Hitchcock, H.A. Jasim, M.F. Lappert, J. Organomet. Chem. 451 (1993) 89, and references therein. [7] (a) W.A. Herrmann, M. Elison, J. Fischer, C. Ko¨cher, G.R.J.

Artus, Chem. Eur. J. 2 (1996) 772. (b) W.A. Herrmann, M. Elison, J. Fischer, C. Ko¨cher, G. R.J. Artus, Angew. Chem. Int. Ed. Engl. 34 (1995) 2371, and references therein.

[8] M.F. Lappert, P.L. Pye, J. Chem. Soc. Dalton Trans (1977) 1283.

[9] R. Aumann, S. Althaus, C. Kru¨ger, P. Betz, Chem. Ber. 122 (1989) 357.

[10] (a) K.H. Do¨tz, D. Grotjahn, K. Harms, Angew. Chem. Int. Ed. Engl. 28 (1989) 1384. (b) D.B. Grotjahn, F.E.K. Kroll, T.

Scha¨fer, K. Harms, K.H. Do¨tz, Organometallics 11 (1992) 298. [11] C.-Y. Liu, D.-Y. Chen, G.-H. Lee, S.-M. Peng, S.-T. Liu,

Organometallics 15 (1996) 1055.

[12] 2a: a light yellow crystalline solid (48%), m.p. 125 – 126°C(dec); 1_{H-NMR (200 MHz, CDCl}

3)d 7.33–7.05 (m, 10 H, Ar–H), 4.24 (t, J = 5.4 Hz, 2H), 4.08 (t, J = 5.4 Hz, 2H);13_C-NMR_{d 195.8,} 194.2(W – CO), 171.0, 144.6 (W – CN – ), 143.0, 134.7, 130.3, 129.7, 128.9, 127.4.127.3, 49.6, 42.2. Elemental Anal. Calcd for C21H14N2O6W: C, 43.93; H, 2.46; N, 4.88. Found: C, 43.48; H, 2.51; N, 4.91.; Crystal data: C21H14N2O6W, Fw = 574.2, Mono-clinic P21/n, a = 12.975(3) A˚ , b=13.417(3) A˚, c=13.590(3) A˚, b=113.56(2)°, V=2168.4(8) A˚3_{, Z = 4, DCalcd= 1.759 g cm}− 3_,

F(000) = 1100, m(Mo–Ka) 54.763 cm− 1_{, crystal size 0.15 ×} 0.35 × 0.50. T = 298 K, CAD 4 diffractometer, 3811 unique reflections [2693 observed, I\2.0s(I)], Rf=0.029, Rw=0.030. GoF = 1.48.

[13] (a) F.E. Hahn, M. Tamm, J. Organomet. Chem. 410 (1991) C9. (b) W.P. Fehlhammer, G. Zinner, G. Beck, J. Fuchs, J. Organomet. Chem. 379 (1989) 277. (c) M. Fritz, D. Rieger, E. Ba¨r, G. Beck, J. Fuchs, G. Holzmann, W.P. Fehlhammer, Inorg. Chim. Acta, 198 (1992) 513. [14] 2b: IR(CH2Cl2) 2171 cm− 1₍_nC N), 2069, 1946 cm− 1(nCO), 1641 cm− 1₍_{nN – CO}_); 1_{H-NMR (200 MHz, CDCl} 3)d 7.5–7.23 (m, 5 H), 4.05 (t, J = 6.0 Hz, 2H), 3.73 (t, J = 6.0 Hz, 2H), 3.40 (q, J = 6.6 Hz, 2H), 1.17 (t, J = 6.6 Hz, 3H); 13_C-NMR _{d 195.7,} 194.1(JP – W= 67 Hz), 170.8, 144.1 (W – CN – ), 133.4, 129.6, 128.6, 126.0, 45.9, 44.9, 42.2, 14.3. 2c: IR(CH2Cl2) 2173 cm− 1 (_nC_N), 2065, 1944 cm− 1₍_nCO_{), 1640 cm}− 1 ₍_{nN – Co}_); 1_H-NMR (200 MHz,CDC13) d 3.92 (t, J=6.0 Hz, 2 H), 3.60 (t, J=6.0 Hz, 2H), 3.46 (q, J = 6.6 Hz, 2H), 2.10 (s, 3H), 1.51 (t, J = 6.6 Hz, 3H). .