научная статья по теме PHOTOCHEMICAL REACTIONS OF CIS-[( 4-NBD)M(CO)4] (NBD = NORBORNADIENE; M = CR, MO) OLEFIN COMPLEXES WITH LIGAND, CONTAINING S AND N DONOR ATOMS Химия

КООРДИНАЦИОННАЯ ХИМИЯ, 2007, том 33, № 12, с. 902-906

УДК 541.49

PHOTOCHEMICAL REACTIONS OF m-[(n4-NBD)M(CO)4] (NBD = NORBORNADIENE; M = Cr, Mo) OLEFIN COMPLEXES WITH LIGAND, CONTAINING S AND N DONOR ATOMS

© 2007 E. Subasi*, S. Karahan*, and A. Ercag**

*Department of Chemistry, Faculty of Science and Literature, Dokuz Eylul University, 35160 Izmir, Turkey ** Department of Chemistry, Faculty of Engineering, Istanbul University, 34850 Istanbul, Turkey

Received August 17, 2006

New complexes cis-[M(CO)4-DABRd] (M = Cr (I), Mo (II) andfac-[M(CO)3-SAT] (M = Cr (III), Mo (IV)) have been synthesized by the photochemical reactions of cis-[(n4-NBD)M(CO)4] (NBD is norbornadiene; M = = Cr, Mo) with 5-(4-dimethylaminobenzylidene) rhodanine (DABRd) and salicylidene-3-amino-1,2,4-triazole (SAT) ligands and characterized by elemental analysis, FT-IR and XH NMR spectroscopy, and mass spectrometry. The spectroscopic studies show that the DABRd ligand acts as a bidentate ligand coordinating via both NH-(S)C=S sulfur donor atoms in I and II and SAT ligand behaves as a tridentate ligand coordinating via its all imine nitrogen -C=N- donor atoms in III and IV to the metal center.

INTRODUCTION

Photosubstitution of VI group metal carbonyls is a highly efficient process which provides convenient access to a large variety of mono- and polysubstituted derivatives [1]. Carbonyl compounds with sulfur and nitrogen donor ligands continue to attract considerable attention not only on account of their fascinating structural chemistry but also because of their ability to act as electron reservoirs and their potential in catalysis [2]. Features of the chemistry of these molecules which are currently of interest include the mechanisms and sites of substitution as well, as the modification of reactivity accompanying carbonyl replacement by donor ligands [3].

Photosubstitutions of CO with the formation of M(CO)5L (M = Cr, Mo, W) from VIB group metal carbonyls M(CO)6 were studied with a variety of c-donor ligands L (L are Schiff base derivatives) [4]. In order to contribute to these studies, we tried to substitute these ligands to the metal center as bi- or polydentate chelates. Along with our continued interest in the photochemical synthesis and structural aspects of VIB group metal carbonyls led us to launch an exploratory investigation into the photolytic behavior of the c/s-[(n4-NBD)M(CO)4] (NBD is norbornadiene) complexes in the presence of ligands containing sulfur and nitrogen donor atoms [5].

Initially, here we describe a particularly convenient photochemical route to the synthesis of c/s-[(n4-NBD)M(CO)4] (M = Cr, Mo). Then we investigated the behavior of c7s-[(n4-NBD)M(CO)4] (M = Cr, Mo) with the title ligands 5-(4-dimethylaminobenzylidene)rhoda-nine (DABRd) and salicylidene-3-amino-1,2,4-triazole (SAT), which contain the pentagonal heterocycle rhodanine and 1,2,4-triazole ring, respectively. New complexes c7s-[M(CO)4-DABRd] (M = Cr (I), Mo (II))

and /ac-[M(CO)3-SAT] (M = Cr (III), Mo (IV)) have been synthesized by the photochemical reactions of [(n4-NBD)M(CO)4] (M = Cr, Mo) with DABRd and SAT ligands and characterized by elemental analysis, FT-IR and NMR spectroscopy, and mass spectrometry. The spectroscopic studies show that DABRd ligand acts as a bidentate ligand coordinating via both sulfur NH-(S)C=S donor atoms in I and II, and SAT ligand behaves as a tridentate ligand coordinating via its all imine nitrogen -C=N- donor atoms in III and IV to the metal center.

EXPERIMENTAL

Materials and methods. All reactions and manipulations were carried out under argon and in argon-saturated solvents using Schlenk techniques. All solvents were dried and degassed using standard techniques [6]. All organic solvents and silica gel were purchased from Merck and M(CO)6 (M = Cr, Mo, W) were from Ald-rich. DABRd [7] and SAT [8] were prepared by literature methods. Elemental analyses were performed on a LECOCHNS-O-9320 instrument at the Technical and Scientific Research Council of Turkey, (TUBITAK). FT-IR spectra of samples were recorded in KBr at the Dokuz Eylul University on a Varian 1000 FT spectrophotometer. NMR spectra were recorded in DMSO on a 500 MHz High Performance Digital FT-NMR instrument at the Ege University and chemical shifts were referenced to tetramethylsilane (TMS). Electron impact mass spectra (Micromass VG Platform-II LC-MS) were recorded at the TUBITAK. Photochemical reactions in a preparative scale were carried out in a water-cooled quartz-walled immersion well reactor equipped with a Philips HPK 125-W high-pressure mercury lamp [9].

PHOTOCHEMICAL REACTIONS OF ds-[(n4-NBD)M(CO)4]

903

Synthesis of the [(n4-NBD)M(CO)4] [M = Cr, Mo, W] complexes were carried out by the photochemical reactions of [ M(CO)6] (M = Cr, Mo, W) with NBD. The yields were 56-72%.

M(CO)6 + NBD —c7s-[(n4-NBD)M(CO)4],

Hexane

M = Cr, Mo

M(CO)6 + NBD c/S-[(n4-NBD)M(CO)4]

Hexane

+ [W(CO)5]2(^-NBD). M = W.

(1)

(2)

These complexes were prepared by similar methods, for example, a method for c/s-[M(CO)4-DABRd]

is the following. Cr(CO)6 (0.22 g, 1 mmol) and NBD (0.276 g, 3 mmol) were dissolved in hexane (70 ml) and the solution was irradiated for 2 h using a 125 W medium-pressure mercury lamp through a quartz-walled immersion well reactor. During the irradiation, the solution changed from colorless to yellow. After irradiation the solvent was evaporated under the vacuum yielding a yellow solid. After subliming out any traces of unre-acted white hexa-carbonylchromate(O) at 25-50°C, the probe is cleaned and the sublimation is continued at 70-90°C to give 0.16 g (72%) yield of bright golden yellow crystalline [(n4-NBD)Cr(CO)4].

Syntheses of the c/s-[M(CO)4-DABRd] (M = Cr (I), Mo (II)) and/ac-[M(CO)3-SAT] (M = Cr (III), Mo (IV)) complexes were carried out by the photochemical reactions of c/5-[(n4-NBD)M(CO)4] (M Cr, Mo) DABRd and SAT. The yields were 40-60%.

cis-[(n4-NBD)M(CO)4] + DABRd M = Cr, Mo

hv

THF*

-NBD

HN-

C

/vc=ch^]H \ /S

OC-M-CO

/ \

OC CO

cis-[M(CO)4-DABRd], M = Cr (I); Mo (II)

CH3

CH3

(3)

HN

N

cis-[(n4-NBD)M(CO)4] + SAT M = Cr, Mo

hv

THF HC C -NBD, -CO HC^, /C

w

OH

(4)

M—CO

OC^ \o

/ac-[M(CO)3-SAT], M = Cr (III); Mo (IV)

These complexes were prepared by similar methods, for example, a method for [Cr(CO)4-DABRd] is the following. The c7s-[(n4-NBD)Cr(CO)4] complexe (0.256 g, 1 mmol) were dissolved in THF (80-100 ml), and the solution was irradiated for 1.5 h using a 125 W medium-pressure mercury lamp through a quartz-walled immersion well reactor. During the irradiation, the solution changed from yellow to lightbrown. After irradiation and cooling system was cut off from the photochemical reactor, DABRd (0.27 g, 1 mmol) was added to the solution and mixed under argon atmosphere for 3 h. Then solvent was evaporated under vacuum yielding a brown solid, which was extracted with CH2Cl2 (10 ml). Addition of petroleum ether (50 cm3) re-

sulted in precipitation of a dark brown solid, which was washed with petroleum ether, dried under vacuum, and shown to be [Cr(CO)4-DABRd] (I). The yield was 62%.

RESULTS AND DISCUSSION

Treatment of the photochemically produced M(CO)5. The intermediates with the ligands in THF led to the expected monosubstituted complexes [10]. These 16-electron M(CO)5 fragments react avidly with any available donor to form M(CO)5L species, where L is a chelating bidentate ligand, and rapid continuation to the chelating M(CO)4L or bridging M2(CO)10L products can occur. Moreover, photochemical occurence of M(CO)4

Table 1. The elemental analysis data and physical properties for olefin and I-IV complexes

Complex Empirical formula (M.w.) Content (found/calcd), % Color Yield,

C H N S %

[(n4-NBD)Cr(CO)4] CrCnH8O4 (256) 50.95/51.56 3.10/3.13 Yellow 72

[(n4-NBD)Mo(CO)4] MoCnH8O4 (300) 43.67/44.00 2.56/2.66 Yellow 66

[(n4-NBD)W(CO)4] + + [W(CO)5]2(|>NBD) WCnH8O4 + W2C1VH8O!0 (388 + 740) 29.67/29.78 1.36/1.42 Yellow 56

I C16H12O5GN2S2 (428) 44.77/44.86 2.75/2.80 6.60/6.54 14.05/14.95 Brown 62

II Ci6Hi2O5MoN2S2 (472) 40.37/40.68 2.35/2.54 5.60/5.93 13.05/13.56 Brown 54

III C12H8O4CrN4 (324) 44.37/44.44 2.35/2.45 17.06/17.28 Brown 60

IV C12H8O4MoN4 (368) 38.87/39.13 1.95/2.17 18.06/18.48 Brown 47

(M = Re), M(CO)3, and M(CO)2 (M = Mn) from [Re(CO)5Br] and [Mn(CO)3Cp] have been done [11]. In this photochemical complexation study, we considered it worthwhile to irradiate cis-[(n4-NBD)M(CO)4] (M = Cr, Mo, W) in the presence of rhodanine and 1,2,4-triazole derivative ligands, because they have never been investigated and can be interesting examples for substitution reactions.

Photolysis of M(CO)6 (M = Cr, Mo, W) in the presence of NBD afforded high yields of the olefin-substi-tuted derivatives cis-[(n4-NBD)M(CO)4] (M = Cr, Mo, W). The relatively stable cis-[(n4-NBD)M(CO)4] (M = = Cr, Mo) complexes could be isolated as pure solids (eq. (1)), while the cis-[(n4-NBD)W(CO)4] complex was found to be contaminated with [W(CO)5]2(^-NBD) (eq. (2)). Therefore, only the cis-[(n4-NBD)M(CO)4] (M = Cr, Mo) complexes were reacted with the title ligands as shown in eq. (1). Assignments of the FT-IR spectra were made by reference to literature data and the data is in accord with the previous publications on the related complexes [12].

New complexes cis-[M(CO)4-DABRd] (M = Cr (I), Mo (II)) and /ac-[M(CO)3-SAT] (M = Cr (III), Mo (IV)) have been synthesized by the photochemical reactions of [(n4-NBD)M(CO)4] (M = Cr, Mo) with DABRd and SAT ligands and characterized by elemental analysis, FT-IR and XH NMR spectroscopy, and mass spectrometry. The photochemical reactions of [(n4-NBD)M(CO)4] (M = Cr, Mo) with DABRd and SAT proceed in this expected manner to yield the hitherto unknown series of complexes I-IV eqs. (1), (2). The analytical results and some physical properties of the novel complexes I-IV are summarized in Table 1. The complexes are air-stable and soluble in chlorinated solvents.

As shown in Table 2, th

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