научная статья по теме SYNTHESIS OF BINUCLEAR COPPER(I) COMPLEXES CONTAINING 2-PICOLINIC ACID Химия

Текст научной статьи на тему «SYNTHESIS OF BINUCLEAR COPPER(I) COMPLEXES CONTAINING 2-PICOLINIC ACID»

ЖУРНАЛ НЕОРГАНИЧЕСКОЙ ХИМИИ, 2004, том 49, № 12, с. 1971-1977

КООРДИНАЦИОННЫЕ ^^^^^^^^^^^^ СОЕДИНЕНИЯ

УДК 541.49

SYNTHESIS OF BINUCLEAR COPPER(I) COMPLEXES CONTAINING

2-PICOLINIC ACID

© 2004 r. Liu Yingfana, b, Zhao Dongc, Yang Ruinac, *, Zhu Jingc, Sun Yuana, Zhang Chuanjianc

aZhengzhou University of Light Industry, Zhengzhou 450002, P. R.China bState Key Laboratory of Coordination Chemistry, Nanjing University 210093, P. R. China cHenan Institute of Chemistry, Zhengzhou 450002, P. R. China Поступила в редакцию 26.03.2004 г.

Abstract-Binuclear copper(I) complex [Cu2(dppm)2(C6H5O2N)2](NO3)2 (C6H5O2N = 2-picolinic acid, dppm = = Ph2PCH2PPh2) has been synthesized and characterized by specific elemental analyses, t.g., 31P-NMR, electronic conductivity and c.v. waves have also been measured. The X-ray crystal structure of the complex shows that dppm coordinates as a bridging bidentate ligand to the copper(I) atoms with tetrahedral coordination structure, and NO- behaves as a free ion in the newly prepared binuclear copper(I) complex.

Keywords: copper, dppm, 2-picolinic acid, complex, binuclear

Dicopper unities are of particular interest in copper® chemistry, having been recognized as active sites of several copper biosystems, in which the proximity of the two metal atoms offers an appropriate two site binding to small molecules [1]. In synthetic chemistry, the carboxylato group was found to have a good ability to form dinuclear complexes with copper(I) centers in close proximity, highly reactive with carbon monoxide, acetylenes, quinoline, isocyanides and azocompounds [2, 3]. Bis(diphenylphosphino)methane is one of the diphosphine ligands most suitable to lock together two metal atoms in close proximity. Many examples of bi-nuclear or polynuclear complexes containing the eight-membered ring M(^-dppm)2M' are known with a variety of metals and stereochemistries [4, 5]. In general, this has consisted of trans-bound, bridging dppm ligands to give a planar M2P4 core structure with the two metal atoms held in close proximity to each other (regardless of whether a metal-metal bond is present or not). This feature is presumably one of the chief reasons for the unusual bonding, reactivity, and catalytic properties of M2(dppm)2 compounds. In the present paper we describe an easy way to synthesize copper(I) complexes using the diphosphine ligand dppm as ligand reductant, where dppm, acting as a bridging ligand, forms binuclear complexes.

We now report the preparation and structure of binuclear dppm copper(I) complex [Cu2(dppm)2(C6H5O2N)2](NO3)2 containing the mixed ligands dppm and 2-picolinic acid.

* Author to whom all correspondence should be addressed. E-mail: sunstarw@yahoo.com.cn

EXPERIMENTAL

General considerations

All reactions were carried out under N2 using standard Schlenk techniques. Commercially available purest samples of various chemicals were used for the preparation of the complexes. All solvents were dried by standard methods and distilled under nitrogen prior to use. The ligand dppm was prepared by an advanced method [4]. Elemental analyses were performed on an ERBA-1106 instrument (Italy). Copper and phosphor content were determined using a JA96-975 ICP-AES (Inductively Coupled Plasmas Atomic Emission Spectrometer). I.r. spectra were recorded on a Nicolet 170SX IR spectrophotometer. TG-DTA spectra were recorded on a PE-TGS-2 instrument. Conductivity measurement was carried out in MeOH solutions thermostatted at 25° using a Shanghai DDS-11A conducto-meter and DJS-1 type platinum black electrode. Melting point was determined on an electrothermal apparatus and is uncorrected. 31P-NMR spectra were measured in CDCl3 with 85% H3PO4 as external reference on a Bruker AV300 NMR spectrometer. *H NMR spectrum was obtained on the same NMR spectrometer with 31P NMR operating at the frequency of 300 MHz at 297 K. Electrospray mass spectra (ES-MS) were recorded on a LCQ system (Finngan, MAT, USA) using methanol as the mobile phase. The spray voltage, tube lens offset, capillary voltage and capillary temperature were set at 4.5 kV, 20.0 V, 7.0 V and 200°C, respectively, and the quoted m/z values are for the major peaks in the isotope distribution. XPS spectra were recorded on a VG ESCALAB MK II instrument using AlKa radiation. High voltage, electric current and vac-

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Table 1. Crystal data and structure refinement for the title complex

Empirical formula C62H54Cu2N4OioP4

Formula weight 1266.06

Crystal system Triclinic

Space group P1

Unit cell dimensions a = 11.820(2) Ä, a = 92.06(3)°

b = 11.990(2) Ä, ß = 114.22(3)°

c = 12.970(3) Ä, y = 113.75(3)°

Cell volume (Ä3) 1489.1(5)

Crystal size 0.30 x 0.30 x 0.20 mm

Z 2

F(000) 652

Dcalc (g ' cm-3) 1.412

Absorption coefficient (cm-1) 8.83

Reflections collected/unique 5512/5234

20 Range, deg 3.5 < 20 < 50

Index ranges 0 < h <14, -14 < k <13, -15 < l < 14

Reflections observed I > 2.0o(I) 4145

Refinement method Full-matrix least-squares on F2

Data/restraints/parameters 5234/0/373

Goodness-of-fit on F2 0.905

Final R indices [I > 2o(I)] R1 = 0.0336, wR2 = 0.1058

R indices (all data) R1 = 0.0515, wR2 = 0.1182

Largest diff. peak and hole 0.308 and -0.260 e ■ Ä-3

uum were set at 12.5 kV, 20 mA and 6 x 10-8 mbar, respectively. Cyclic voltammograms were obtained in CH2Cl2 (0.1M Bu4NClO4) by using an MEC-12A analyzer and a conventional three-electrode system at 25°C. The platinum working electrode was in the form of a disc and used in a stationary mode, the auxiliary electrode was a platinum plate with an area of 2 x x 8 mm2, the reference electrode was a saturated calomel electrode (SEC).

Synthesis of the complexes

[Cu(dppm)(NO3)]2. Dppm (2 mmol, 0.768 g) was added to hot EtOH (60 cm3) to form a colorless solution. Then while heated and stirred, in the solution was added solid Cu(NO3)2 ■ 3H2O (1 mmol, 0.241 g) during 30 min. The addition of the first portion of Cu(NO3)2 ■ 3H2O caused the colorless solution immediately turn to grey and then light yellow. The addition of the remaining Cu(NO3)2 ■ 3H2O caused precipitation of a white powder. The mixture was stirred and heated at its reflux temperature for 30 min, then cooled, filtered out and washed with MeOH and Et2O, then dried in vacuum at room temperature. Colorless cubic crystals were obtained by recrystalization of the product

[Cu(dppm)(NO3)]2 from CH2Cl2 and MeOH. (Yield: 66%). For C50H44Cu2P4N2O6 anal. Calcd. (%): C, 58.88; H, 4.35; N, 2.75; P, 12.15; Cu, 12.46. Found (%): C, 58.68; H, 4.21; N, 2.61; P, 12.01; Cu, 12.36. -XH NMR (300 MHz, CDCl3): 5 3.18 (s, 4 H, CH2 of dppm), 7.30-7.73 (m, 40 H, C6H5).

[Cu2(dppm)2(C6H5O2N)2](NO3)2. 2-Picolinic acid (2 mmol, 0.246 g) was added to a suspension of [Cu(dppm) (NO3)]2 (1 mmol, 1.019 g) in MeOH (60 cm3). The mixture was stirred for 12 h at room temperature. Concentration of the resulting solution and addition of diethyl ether (20 cm3) led to the precipitation of a yellow solid which was recrystallized from dichloromethane and ethanol, and vacuum dried. Yield: 56%. For C62H54Cu2N4O10P4 anal. Calcd. (%): C, 58.82; H, 4.30; N, 4.43; P, 9.79; Cu, 10.04. Found (%): C, 58.63; H, 4.21; N, 4.33; P, 9.63; Cu, 9.96. - *H NMR (300 MHz, CDCl3): 5 3.20 (s, 4 H, CH2 of dppm), 6.947.70 (m, 48 H, C6H5, C5H4N), 12.16 (2 H, COOH of 2-picolinic acid), -31P NMR (CDCl3): -14.4 ppm (s).

Table 2. Final non-hydrogen atomic coordinates and thermal parameters (A2)

Atom X/a Y/b Z/c Ueq

Cu 0.67040(3) 0.52126(3) 0.64626(3) 0.03637(13)

P(1) 0.57104(7) 0.31653(6) 0.57175(5) 0.03326(17)

P(2) 0.71397(6) 0.70310(6) 0.58927(5) 0.03202(16)

O(5) 0.63063(19) 0.58583(18) 0.78144(15) 0.0438(4)

C(53) 0.8089(3) 0.8424(3) 0.4459(2) 0.0421(6)

N(1) 0.8564(2) 0.5663(2) 0.8020(2) 0.0451(5)

C(44) 0.5502(3) 0.2675(3) 0.7720(2) 0.0407(6)

C(45) 0.5269(3) 0.1939(3) 0.8482(3) 0.0564(8)

C(2) 0.5857(3) 0.7608(2) 0.5705(2) 0.0370(6)

C(55) 0.6892(3) 0.6193(3) 0.3762(2) 0.0426(6)

C(54) 0.7417(2) 0.7241(2) 0.4618(2) 0.0334(5)

C(43) 0.5300(3) 0.2146(2) 0.6659(2) 0.0369(6)

O(4) 0.7368(3) 0.6791(3) 0.97014(18) 0.0740(7)

N(2) 0.4770(4) 0.7395(3) 0.8674(2) 0.0701(8)

C(1) 0.7324(3) 0.6286(3) 0.8778(2) 0.0467(7)

C(35) 0.7011(3) 0.2856(3) 0.5513(2) 0.0417(6)

O(3) 0.5139(3) 0.6753(3) 0.9378(2) 0.0874(8)

C(52) 0.8223(3) 0.8541(3) 0.3455(3) 0.0521(7)

C(24) 0.8774(3) 0.8257(2) 0.7064(2) 0.0404(6)

C(56) 0.7029(3) 0.6319(3) 0.2752(3) 0.0569(8)

C(25) 0.9999(3) 0.8203(3) 0.7257(3) 0.0539(7)

O(2) 0.5564(4) 0.8019(3) 0.8304(3) 0.0972(9)

C(46) 0.4849(4) 0.0672(4) 0.8181(3) 0.0656(9)

C(14) 0.8639(3) 0.6244(3) 0.8966(2) 0.0472(7)

C(51) 0.7693(3) 0.7489(3) 0.2607(3) 0.0573(8)

C(42) 0.4825(4) 0.0861(3) 0.6358(3) 0.0573(8)

C(34) 0.7340(3) 0.3238(3) 0.4635(3) 0.0588(8)

C(13) 0.9700(3) 0.5591(3) 0.8118(3) 0.0595(8)

C(23) 0.8852(4) 0.9168(3) 0.7811(3) 0.0596(8)

C(15) 0.9837(4) 0.6770(3) 1.0020(3) 0.0715(10)

C(26) 1.1257(3) 0.9019(4) 0.8180(3) 0.0728(11)

O(1) 0.3629(4) 0.7341(5) 0.8388(3) 0.1311(15)

C(36) 0.7759(4) 0.2327(4) 0.6270(3) 0.0663(9)

C(41) 0.4607(4) 0.0137(3) 0.7125(4) 0.0709(10)

C(32) 0.9165(4) 0.2641(5) 0.5299(4) 0.0850(13)

C(12) 1.0944(4) 0.6112(4) 0.9146(4) 0.0810(12)

C(33) 0.8434(4) 0.3149(4) 0.4547(4) 0.0779(11)

C(22) 1.0149(5) 1.0011(3) 0.8728(3) 0.0813(12)

C(31) 0.8838(4) 0.2225(5) 0.6161(4) 0.0860(13)

C(21) 1.1327(4) 0.9925(4) 0.8903(3) 0.0881(15)

C(11) 1.1000(4) 0.6698(4) 1.0097(4) 0.0874(13)

X-ray data collection and structure determination sponding to the ion

A single crystal of dimensions (0.3 x 0.3 x 0.2 mm) of the title complex was selected and mounted on an automatic Enraf-Nonius CAD-4 four-circle diffracto-meter equipped with a graphite monochromator employing MoKa radiatoion (X = 0.71073 A). A total of 5512 unique reflections (Rint = 0.1136) were measured at room temperature with 3.5° < 20 < 50°. No significant change was detected in the intensity of the three standard reflections. Lorentz, polarization and absorption corrections were applied to the inten

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