Reactivity of alkynyl Pd(II) azido complexes toward organic isocyanides, isothiocyanates, and nitriles

Inorganica Chimica Acta 358 (2005) 650–658 www.elsevier.com/locate/ica

Reactivity of alkynyl Pd(II) azido complexes toward organic isocyanides, isothiocyanates, and nitriles Yong-Joo Kim

a,*

, Seung-Ha Lee a, Sung-Hyun Lee a, Sang Il Jeon a, Mi S. Lim b, Soon W. Lee b

a b

Department of Chemistry, Kangnung National University, Kangnung 120, Kangnung 210-702, Korea Department of Chemistry, Sungkyunkwan University, Natural Science Campus, Suwon 440-746, Korea Received 4 August 2004; accepted 28 September 2004 Available online 22 October 2004

Abstract Alkynyl Pd(II) azido complexes of the type [Pd(N3)(C„CAR)L2] (1–3) were obtained by reactions of aqueous NaN3 with [Pd(Cl)(C„CAR)L2] (R = Ph or C(O)OMe). Treating compounds 1–3 with organic isocyanides (R–NC) afforded novel complexes, trans-[Pd(C„CAPh)(N@C@NAR)(PMe3)2] (R = 2,6-Me2C6H3 (4) or 2,6-Et2C6H3 (5)) and trans-[Pd(C„CAR)(CN4-t-Bu)L2] (6: L = PMe3, R = Ph; 7: L = PEt3, R = C(O)OMe; 8: L = PMe3, R = C(O)OMe), which contain either a carbodiimido or a C-coordinated tetrazolato group. Reactions of compounds 1 and 2 with R–N@C@S (R = 2,6-Me2C6H3 or CH2CH3) and 1,4-phenylene diisothiocyanate (C6H4(N@C@S)2) smoothly proceeded to give tetrazole–thiolato complexes, trans-[Pd(C„CPh)(SCN4–R)L2] (L = PMe3, R = Et (9) or 2,6-Me2C6H3 (10); L = PEt3, R = 2,6-Me2C6H3 (11)), and a phenylene-bridged dinuclear Pd(II) tetrazole–thiolato complex, [(PEt3)2(C„CPh)Pd(SCN4-(l-C6H4)–SCN4)Pd(C„CPh)(PEt3)2] (12), respectively. Complexes 9–12 contain the Pd–S bond that is formed by the dipolar cycloaddition of the organic isothiocyanate to the Pd–azido bond. In contrast, the vcorresponding reactions of compounds 1and 2 with C6F5CN and Me3SiCN (organic nitriles, R–CN) gave an N-coordinated Pd(II)-tetrazolato compound {trans-[Pd(C„CAPh)(N4C–C6F5)(PMe3)2] (13)} and a mixture of Pd(II)-cyano complexes {trans[Pd(C„CAPh)(CN)(PEt3)2] (14) and [Pd(CN)2(PEt3)2] (15)}, respectively. Bis(phosphine) bis(cyano) complexes of Pd and Ni, [M(CN)2L2] (L = PEt3, PMe3; L2 = DEPE), could be obtained independently by the reactions of [M(N3)2L2] with excess Me3SiCN in organic solvents.
2004 Elsevier B.V. All rights reserved. Keywords: Azido; Cycloaddition; Alkynyl; Carbodiimide; Palladium

1. Introduction Dipolar cycloaddition of unsaturated organic compounds such as isocyanide, nitrile, and alkyne to an azido ligand, which gives metal complexes containing C- or N-coordinated heterocycles, has been an interesting subject for many decades [1–18]. We recently reported several late transition-metal complexes containing such *

Corresponding author. Tel.: +82 33 640 2308; fax: +82 33 647 1183. E-mail address: [email protected] (Y.-J. Kim). 0020-1693/$ - see front matter
2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2004.09.056

heterocycles (C-coordinated), which were prepared by treating bis(phosphine) metal complexes of bis(azido) [M(N3)2(PR3)2] and mono(azido) methyl or phenyl [M(N3)(R)(PR3)2] (R = Me or Ph) with organic isocyanides [19]. Although many derivatives of late transition-metal mono- or bis(azido) complexes have been employed to study on the formation of metal complexes containing the heterocycles mentioned above, azido metal–alkynyl complexes have been relatively unexplored. The alkynyl ligand exhibits interesting properties such as cluster formation involving the bridging alkynyl ligand in multinuclear complexes [20–22], its conversion

Y.-J. Kim et al. / Inorganica Chimica Acta 358 (2005) 650–658

to the corresponding vinylidene species [23], and its potential optical or liquid crystalline properties as a molecular wire having linear AC„C units [24]. We here wish to report the preparation of alkynyl palladium(II)azido complexes and their reactivity toward organic isocyanides and organic pseudo-halides (isothiocyanates and nitriles).

651

reactions of 1–3 with tert-butyl isocyanide gave Pd(II) complexes having a C-coordinated tetrazolato ring, trans-Pd[(C„CAR)(CN4–t-Bu)L2] (R = Ph, L = PMe3 (6) or PEt3 (7); R = C(O)OMe, L = PMe3, (8)), as shown in Eq. (4). Carbodiimido complexes 4–8 were isolated in high yields and characterized by IR, NMR, and elemental analyses. Molecular structures of 5 and 6 were determined by X-ray crystallography. R

2. Results and discussion

L

Alkynyl palladium(II) azido complexes 1–3 have been prepared by usual coupling reactions and then subsequent metathetical substitution with NaN3 as shown in Eqs. (1) and (2). These complexes have been obtained as white crystalline solids in high yields and characterized by IR, NMR, and elemental analyses. Formation of those complexes can be readily conformed by monitoring the strong absorption bands in the range of 2050–2100 cm
1 due to the N3 and C„C stretching bands. CuBr, Et2NH R H

R (1eq)

Pd

Cl

ð1Þ

L Pd

L Cl

L R

N3

Ph

L

Pd

R N=C=N

L L = PMe3, R = Me, 4 L = PMe3, R = Et, 5

R

ð3Þ L

L

CN R

Pd

N3

N R

Pd

N

N N L R = Ph L = PMe3, 6; PEt3, 7 R = C(O)OMe L = PMe3, 8

ð4Þ L

R

Pd

L

L PdCl2L2

Ph

CN

NaN3 R

Pd

N3

ð2Þ

L

L R = Ph, L = PMe3 (1), PEt3, (2) R = MeO(CO), L = PMe3 (3)

2.1. Reactions with isocyanides As mentioned in Section 1, we recently reported that bis(phosphine) group 10 metal complexes, [M(N3)2(PR3)2] and [M(N3)(R)(PR3)2] (R = Me or Ph), reacted with various isocyanides to give complexes containing carbodiimido or tetrazolato groups through cyclodaddition of isocyanides to the metal–azido bond [19]. On the basis of these results, we have examined the reactivity of alkynyl palladium(II) azido complexes toward isocyanides as shown in Eq. (3). Treatment of the isocyanide with the azido complex caused immediate evolution of nitrogen gas, and their reaction was monitored by the IR spectra, which showed the disappearance of an asymmetric stretching N3 band at ca. 2050 cm
1 and the appearance of new strong bands at ca. 2170 cm
1 and 2117–2128 cm
1 due to the carbodiimido (N@C@N) and C„C groups, respectively, in the products, trans[Pd(C„CPh)(N@C@NAR)(PMe3)2] (R = 2,6-Me2C6H3 (4) or 2,6-Et2C6H3 (5)). On the other hand, analogous

No other products (for example, an imino-bonded complex formed by the isocyanide insertion into the Pd–C bond) were observed. The formation of carbodiimido Pd(II) complexes appears to involve an initial formation of a C-coordinated tetrazolato ring by the cycloaddition of isocyanide into the palladium–azido bond and then the subsequent ring conversion to an end-on NCN group with the elimination of N2 to give a final product. In a recent work, we reported that the formation of the carbodiimido or C-coordinated tetrazolato group was dependent not only on the type of an attacking isocyanide and but also on the steric bulk of alkyl substituents on the aryl ring that might facilitate N2 elimination from the tetrazolato ring to give the corresponding carbodiimido group [19a,19b]. Figs. 1 and 2 show the molecular structures of trans[Pd(C„CPh)(N@C@NAC6H3-2,6-Et2)(PMe3)2] (5) and trans-[Pd(C„CPh)(CN4-t-Bu)(PMe3)2] (6), respectively. Crystal data are summarized in Table 1. Fig. 1 clearly shows the square-planar geometry of complex 5, which contains two PMe3, one alkynyl, and one end-on carbodiimido (NCN–C6H3-2,6-Et2) ligands. The linear phenylethynyl group is located trans to the carbodiimido group. A triplet in 13C{1H} NMR, which is coupled with two phosphine ligands and corresponds to the alkynyl carbon (Ca„C or C„Cb) directly bonded to the Pd metal, supports the trans-geometry of the complexes. Furthermore, a singlet at
12.3 ppm in 31P{1H} NMR also supports the trans-structure. The phenyl ring in the carbodiimido ligand is nearly perpendicular to the

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Y.-J. Kim et al. / Inorganica Chimica Acta 358 (2005) 650–658

˚ ) and angles (): Fig. 1. ORTEP drawing[34] of 5 showing the atom-labeling scheme and 50% probability thermal ellipsoids. Selected bond lengths (A Pd1–C7 1.941(3), Pd1–N1 2.035(3), Pd1–P2 2.3023(8), Pd1–P1 2.3086(8), N1–C15 1.156(4), N2–C15 1.252(4), N2–C16 1.386(4), C7–C8 1.202(4), C8– C9 1.439(4); C7–Pd1–N1 177.0(1), P2–Pd1–P1 174.72(3), C15–N1–Pd1 160.0(3), C15–N2–C16 133.0(3), N1–C15–N2 171.7(4), C8–C7–Pd1 177.5(3), C7–C8–C9 177.6(3).

2.2. Reactions with organic pseudo-halides

˚ ) and angles (): Fig. 2. ORTEP drawing of 6. Selected bond lengths (A Pd1–C7 2.005(5), Pd1–C15 2.036(4), N1–C15 1.352(4), N1–N2 1.360(4), N2–N3 1.280(5), N3–N4 1.367(5), N4–C15 1.348(5), C7–C8 1.195(6); C7–Pd1–C15 178.2(1), C15–Pd1–P1 92.45(9), C15–Pd1–P2 93.03(9), P1–Pd1–P2 170.66(4), C15–N1–N2 110.0(3), N2–N1–C16 119.6(3), N3–N2–N1 106.5(3), N2–N3–N4 110.7(3), C15–N4–N3 107.3(3), C8–C7–Pd1 172.9(4).

equatorial plane with the dihedral angle of 84.58(9). The Pd–N bond length of 5 is close to the previously reported one in trans-[Pd(CN4–R)(N@C@NAR)(PMe3)2] ˚ ) [19b], but it is slightly shorter than (2.030(5) A that in trans-[Pd(Ph)(N@C@NAC6H3-2,6-Me2)(PMe3)2] ˚ ) [19c], suggesting a weaker trans-influence of (2.087(3) A the phenylethynyl group than the phenyl ring. The asymmetric nitrogen–carbon bonds (1.156(4) and ˚ ) in the carbodiimido (N@C@N) group of 5 1.252(4) A have also been observed for those in other carbodiimido complexes [19a]. Fig. 2 shows the structure of 6 possessing the C-coordinated tetrazolato ring. A triplet signal at 164 ppm in 13C{1H} NMR due to the carbon of the tetrazolato ring strongly supports the C-coordination of the ring to the Pd metal.

In order to examine the scope of the reactivity of the alkynyl Pd(II) azido complexes, we have treated them with RAN@C@S (R = 2,6-Me2C6H3 or CH2CH3) and 1,4-phenylene diisothiocyanate (C6H4(N@C@S)2). These reactions as shown in Eq. (5), dipolar cycloaddition of an organic RAN@C@S into the Pd–azido bond, proceeded smoothly at room temperature to give tetrazole–thiolato complexes, trans-[Pd(C„CPh)(SCN4–R)L2] (L = PEt3, R = 2,6-Me2C6H3 (9); L = PMe3, R = Et (10) or 2,6-Me2C6H3 (11)). As shown in Eq. (6), the same reaction with 1,4-phenylene diisothiocyanate (2:1 ratio) also produced a phenylene-bridged dinuclear Pd(II) tetrazole–thiolato complex, [(PEt3)2 (C„CPh)Pd(SCN4-(l-C6H4)–SCN4)Pd(C„CPh)(PEt3)2] (12). Complexes 9–12 were characterized by spectroscopic and analytical methods. Formulation of 12 was also confirmed by FAB(+) mass spectra. The reaction completion can be readily confirmed by monitoring the disappearance of m(N3) band at 2030 cm
1, which results from the dipolar cycloaddition of the isothiocyanates into the Pd–azido bond. Integration ratios in each of the 1H NMR spectra of 9–12 are consistent with the proposed structures. A signal at 161–164 ppm in 13C{1H} NMR corresponds to the carbon atom of the tetrazolato ring, [S–(CN4–R)]. A singlet in 31 P{1H} NMR also supports the proposed trans-structure. These spectral data strongly indicate the absence of N-bonded tetrazoline compounds M[N4(R)(C@S)], which can adopt an N1- or an N2-bonded form. Fig. 3 shows an ORTEP drawing of trans-[Pd(C„CPh)(SCN4–C6H3-2,6-Me2)(PMe3)2] (11). The molecular structure of 11 clearly shows an S-coordinated tetrazolato ring.

Y.-J. Kim et al. / Inorganica Chimica Acta 358 (2005) 650–658

653

Table 1 X-ray data collection and structure refinement for 5, 6, 11, and 18

Formula Fw Tmperature (K) Crystal size (mm3) Crystal system Space group ˚) a (A ˚) b (A ˚) c (A a () b () c () ˚ 3) V (A Z dcalc (g cm
3) l (mm
1) F(000) Tmin Tmax Number of reflections measured Number of reflections unique Number of reflections with I > 2r(I) Number of parameters refined ˚
3) Maximum in Dq (e A ˚ Minimum in Dq (e A
3) Goodness of fitness on F2 1.053 R wR2a 0.0775 R (all data) wR2a (all data) P P a wR2 ¼ ½wðF 2o
F 2c Þ2 = ½wðF 2o Þ2 1=2 .

5

6

11

18

C25H36N2P2Pd 532.90 295(2) 0.24 · 0.22 · 0.20 triclinic P 1 9.832(1) 12.246(2) 13.028(1) 65.519(7) 73.463(10) 87.496(8) 1363.4(3) 2 1.298 0.811 552 0.7891 0.8413 4927 4629 4081 272 0.435
0.399 1.021 0.0300 0.0899 0.0367 0.0813

C19H32N4P2Pd 484.83 296(2) 0.40 · 0.24 · 0.22 monoclinic P21/c 20.586(18) 9.5410(9) 12.2037(9)

C23H32N4P2SPd 564.93 293(2) 0.20 · 0.15 · 0.08 triclinic P 1 9.405(2) 13.239(2) 13.321(2) 119.69(1) 97.16(2) 103.09(2) 1347.4(4) 2 1.392 0.902 580 0.8304 0.9377 4609 4324 3080 280 0.293
0.353 1.090 0.0455 0.0527 0.0775 0.1102

C12H24N2P2Pd 364.67 293(2) 0.20 · 0.18 · 0.16 monoclinic C2/c 18.376(2) 8.525(1) 10.255(1)

˚ ) and angles (): Fig. 3. ORTEP drawing of 11. Selected bond lengths (A Pd1–C8 1.966(5), Pd1–P1 2.306(2), Pd1–P2 2.316(2), Pd1–S1 2.357(2), S1–C15 1.716(5), N1–C15 1.324(6), N1–N2 1.371(6), N2–N3 1.289(6), N3–N4 1.359(6), N4–C15 1.363(6), C7–C8 1.209(7); C8–Pd1–P1 85.1(2), C8–Pd1–P2 85.9(2), P1–Pd1–P2 170.06(5), C8–Pd1–S1 178.0(2), P1–Pd1–S1 95.99(6), P2–Pd1–S1 93.18(6), C15–S1–Pd1 106.3(2), C15–N1–N2 105.8(4), N3–N2–N1 111.6(4), N2–N3–N4 106.1(4), N3–N4–C15 108.5(4).

96.455(6) 2381.7(4) 4 1.352 0.923 1000 0.4453 0.5235 4388 4167 3433 236 0.439
0.551 1.009 0.0364 0.0962 0.0481 0.0956

1596.4(3) 4 1.517 1.346 744 0.7293 0.9273 1399 1359 1356 78 0.241
0.298 0.0202 0.0211 0.0534

(Eqs. (5) and (6)) also gave tetrazole–thiolato Pd(II) complexes having alkynyl ligands. Although several studies [5f,6,10,14,26] on the cycloaddition of organic isothiocyanates into the transition-metal azido complexes to give N-bonded tetrazoline-5-thione, (M[N4(C@S)]) complexes have been reported, the case of tetrazole–thiolato complex formation did not appear in the literature until our recent work. It is worth noting that Beck et al. [27] previously prepared anionic tetrazole–thiolato Pd(II) and Pt(II) complexes in a way different from ours: (a) by the metathesis of metal halides with alkali metal salts of tetrazole mercaptan or (b) by the reactions of metal halides with alkyl mercaptan in the presence of amine. L Ph

Pd L

Recently, we reported that reactions of bis(azido)– Pd(II) complexes with organic isothiocyanates gave tetrazole–thiolato complexes [25]. Our present work

96.402(8)

L N3

R N

R-NCS Ph

Pd

S

N N

N

L L = PEt3, R = 2,6-Me2C6H3, 9 L = PMe3, R = CH2CH3, 10; 2,6-Me2C6H3, 11

ð5Þ

654

Y.-J. Kim et al. / Inorganica Chimica Acta 358 (2005) 650–658 PEt3 SCN

Ph

Pd

NCS

N3 ( 2:1)

PEt3 PEt3 Ph

Pd

PEt3 S

S N

PEt3 N N

N

N

N

Pd

N

Ph

PEt3

N

12

ð6Þ We have also examined dipolar cycloaddition reactions between alkynyl Pd(II) azido complexes and organic nitriles such as C6F5CN and Me3SiCN. Treatment of 1 with excess C6F5CN at room temperature gave an N-coordinated tetrazolato compound, trans[Pd(C„CPh)(N4C–C6F5)(PMe3)2] (13), as shown in Eq. (7). 1H and 31P{1H} NMR spectra of the crude product, which show two virtual triplets (integration ratio of 8:92) due to PMe3 ligands in the 1H NMR and two singlets in the 31P{1H} NMR, suggest the presence of a mixture of N1 or N2-coordinated tetrazolato isomers. By fractional recrystallization of the crude reaction product, a pure tetrazolato complex 13 could be isolated as white solids in 37% yield. PMe3 Ph

Pd PMe3

PMe3 N3

C6F5CN

N Ph

Pd

N

PMe3

N

C

C6F5

N 13

ð7Þ IR spectrum of 13 shows a characteristic C„C band without the N3 band of the starting material. Earlier works by Beck and co-workers [5c,6] and several other research groups [14b,14c,28,29] demonstrated the similar N1- or N2-coordination modes in the tetrazolato Pd(II) or Pt(II) complexes. In particular, Paul and Nag [14a] observed that both N1 and N2-bound tetrazo-

lato isomers were formed by the reactions of Ni(II) azido complexes with benzonitrile derivatives with the relative abundances dependent on the reaction stoichiometry and that the N2-bound isomer was a sole product in the case of p-NO2C6H5CN. Interestingly, similar reactions of 2 with excess Me3SiCN at room temperature led to the formation of unusual metal cyano complexes, trans-[Pd(C„CPh)(CN)(PEt3)2] (14, 85%) and [Pd(CN)2(PEt3)2] (15, trace), as a mixture (Eq. (8)). PEt3

PEt3

Me3SiCN Ph

Pd PEt3

N3

Ph

Pd PEt3

CN + Pd(CN)2(PEt3)2 15 14

ð8Þ Complex 14 is soluble in diethyl ether and so can be readily extracted from the mixture. IR spectrum of 14 shows a strong absorption band at 2108 cm
1 due to m(CN), which is overlapped with a weak m(C„C) band. In the 13C{1H} NMR spectrum of 14, a triplet at 136.0 (J = 13 Hz) ppm due to the C„N and two triplets at 105.0 (J = 17 Hz) and 110.9 (J = 4 Hz) ppm, corresponding to the Ca„C and C„Cb, respectively, strongly support the presence of a cyano group and an alkynyl group coordinated to the Pd center. The same reaction with 1 also produced a mixture of [Pd(C„CPh)(CN)(PMe3)2] (16) and [Pd(CN)2(PMe3)2] (17), but quite similar solubility of these complexes prohibited the isolation of a pure alkynyl Pd(II) cyano complex (16). Bis(cyano) palladium(II) complexes 15 and 17 could be independently prepared from [Pd(N3)2L2] (L = PEt3, PMe3, or DEPE) and two equivalent or excess Me3SiCN as shown in Eq. (9). Furthermore, this synthetic method could successfully apply to the preparation of a nickel(II) analog Ni(CN)2(PEt3)2. Fig. 4 shows the molecular structure of 18. Considering the structures of cyano pal-

˚ ) and angles (): Pd1–C6 2.034(2), Pd1–P1 2.2792(6), N1–C6 1.139(3); C6–Pd1–P1 174.03(7), Fig. 4. ORTEP drawing of 18. Selected bond lengths (A N1–C6–Pd1 177.0(2).

Y.-J. Kim et al. / Inorganica Chimica Acta 358 (2005) 650–658

ladium and nickel complexes 14–19, an order of trans-effect strengths among ligands appears to be azido < alkynyl, cyano in our reaction systems. M(N3)2L2 + 2 Me3SiCN

M(CN)2L2 M = Pd L = PEt3, 15 L = PMe3, 17 L-L = DEPE, 18 M = Ni L = PEt3, 19

ð9Þ

The formation of cyano complexes 14 and 15 (Eq. (8)) indicates that Pd–C (alkynyl) and Pd–N bonds are cleaved by the relatively weak nucleophile (CN
) to give metal cyano complexes. However, we could not observe that other types of organic nitriles (R–CN) gave such cyano complexes. There are a couple of examples demonstrating the replacement of carbon-donor ligands by the CN
agent (in the form of Me3SiCN). For example, Tsuji et al. [30] reported palladium-catalyzed cyanation in reactions between Me3SiCN and allylic acetate or carbonates. In this study, Me3SiCN converted a p-allyl palladium acetate complex to a cyano Pd(II) complex. Moreover, Butenscho¨n and co-workers recently reported the transformation of a cyclopentadienyl Co(I) ethane complex to a dicyano Co(III) complex by the oxidative addition of Me3SiCN [31]. Generally, transition-metal cyano complexes are prepared from transition-metal halides and alkali metal cyanide by metathesis in alcohol or aqueous media. Therefore, the formation of the cyano complexes with Me3SiCN (Eqs. (8) and (9)) can be an efficient way of introducing the cyano group to metal–azido complexes in organic solvents, and this type of cyanation may be expanded to prepare other pseudo-halogen compounds of transition metals. In summary, we prepared three novel alkynyl Pd(II) azido complexes and examined their reactivity toward organic isocyanides, isothiocyanates, and nitriles. Depending on the organic substrates, complexes containing five-membered heterocycles (C- or N-coordinated tetrazolato or tetrazole–thiolato) or carbodimido groups were formed. These results show an overall agreement with those previously found in bis(azido) group 10 metal complexes [19a]. One interesting finding in this study is that Me3SiCN can serve as an efficient agent in introducing the cyano group into the transition-metal azido complexes in organic solvents to give cyano or bis(cyano) Pd(II) and Ni(II) complexes.

3. Experimental 3.1. General All manipulations of air-sensitive compounds were performed under N2 or Ar by standard Schlenk tech-

655

niques. Solvents were distilled from Na-benzophenone. The analytical laboratory at the Kangnung National University carried out elemental analyses using CE instruments EA1110. IR spectra were recorded on a Perkin–Elmer BX spectrophotometer. NMR (1H, 13 C{1H}, and 31P{1H}) spectra were obtained on a JEOL Lamda 300 MHz spectrometer. Chemical shifts were referenced to internal Me4Si and to external 85% H3PO4. [PdCl(C„CAR)L2] (R = Ph, C(O)OMe; L = PMe3, PEt3)2 were prepared by the literature method [32]. 3.2. Preparation of trans-[Pd(N3)(C„CAR)L2] (R = Ph, L = PMe3 (1), PEt3 (2); R = (CO)OMe, L = PMe3 (3)) To a THF solution (10 ml) of [PdCl(C„CPh)(PMe3)2] (0.344 g, 0.87 mmol) was added an aqueous solution of NaN3 (0.113 g, 1.74 mmol) by a cannula. After stirring the reaction mixture for 24 h at room temperature, the solvent was completely evaporated. The residue was then extracted with CH2Cl2. The collected extract was reduced to 3 ml under vacuum. Addition of n-hexane (10 ml) caused separation of pale brown solids, which were freshly chromatographed from alumina (elutant, CH2Cl2) and then recrystallized from ether to give white solids (83%) of [Pd(N3) (C„CPh)(PMe3)2] (1). IR (KBr, cm
1): 2120 (w, C„C), 2046 (s, br, N3). 1H NMR (CDCl3, d): 1.58 (t, 18 H, J = 3.5 Hz, PMe3) 7.17–7.31 (m, 5 H, Ph). 13 C{1H} NMR (CDCl3, d): 14.1 (t, J = 16 Hz, P(CH3)3), 93.7 (t, J = 19 Hz, Ca„C), 108.0 (t, J = 5.3 Hz, C„Cb), 126.1, 127.0, 128.1, 130.9 (t, J = 1.6 Hz). 31 P{1H} NMR (CDCl3, d):
14.8(s). Anal. Calc. for C14H23N3P2Pd: C, 41.86; H, 5.77; N, 10.46. Found: C41.97; H, 5.91; N, 9.21%. Complexes 2 and 3 were similarly prepared. Complex 2 (79 %): IR (KBr, cm
1): 2117 (w, C„C), 2052 (s, br, N3). 1H NMR (CDCl3Hz, d): 1.24 (q, 18 H, J = 7.9 Hz, P(CH2CH3)3), 1.96 (m, 12 H, P(CH2CH3)3), 7.15–7.27 (m, 5 H, Ph). 13C{1H} NMR (CDCl3, d): 8.34 (s, P(CH2C H3)3), 15.4 (t, J = 14 Hz, P(CH2CH3)3), 93.4 (br s, Ca„C), 108.0 (t, J = 5 Hz, C„Cb), 125.8, 127.6, 128.1, 130.7 (t, J = 1 Hz). 31P{1H} NMR (CDCl3, d):
13.6(s). Anal. Calc. for C20H35N3P2Pd: C, 49.44; H, 7.26; N, 8.65. Found: C, 49.40; H, 7.20; N, 8.21%. Complex 3 (82%): IR (KBr, cm
1): 2128 (w, C„C), 2059 (s, br, N3), 1687 (s, br, CO). 1H NMR (CDCl3, d): 1.55 (t, 18 H, J = 3.7 Hz, PMe3), 3.68 (s, 3 H, Me). 13 C{1H} NMR (CDCl3, d): 13.9 (t, J = 16 Hz, P(CH3)3), 51.9 (s, Me), 100.0 (t, J = 5.0 Hz, C„Cb), 104.2 (t, J = 19 Hz, Ca„C), 154.2 (t, J = 1.2 Hz, CO(O)). 31P{1H} NMR (CDCl3, d):
14.2(s). Anal. Calc. for C10H21N3O2P2Pd: C, 31.31; H, 5.52; N, 10.95. Found: C, 31.78; H, 5.45; N, 10.69%.

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3.3. Reactions with organic isocyanides To a Schlenk flask containing complex 1 (0.285 g, 0.71 mmol) were sequentially added CH2Cl2 (7 ml) and 2,6-dimethylphenyl isocyanide (0.094 g, 0.72 mmol). The initial colorless solution immediately turned to pale yellow with the evolution of nitrogen. After stirring for 2 h at room temperature, the reaction mixture was completely evaporated under vacuum, and then the resulting residue was solidified with ether. The solids were filtered and washed with hexane (5 ml). Recrystallization from ether gave yellow crystals of 4, trans-[Pd(C„CPh) (N@C@NAC6H3-2,6-Me2)(PMe3)2] (0.203 g, 57%). IR (KBr, cm
1): 2175 (s, br, N@C@N), 2122 (w, br, C„C). 1H NMR (CDCl3, d): 1.56 (t, 18 H, J = 3.5 Hz, PMe3), 2.35 (s, Me), 6.67–6.72 (m, 1 H, Ph), 6.90– 6.93 (m, 2 H, Ph), 6.93–7.31 (m, 5 H, Ph). 13C{1H} NMR (CDCl3, d): 14.1 (t, J = 16 Hz, P(CH3)3), 18.9 (s, Me), 94.6 (s, br, Ca„C), 108.6 (t, J = 5.6 Hz, C„Cb) 119.4, 125.6, 126.6, 127.3, 127.7, 130.4, 130.6, 143.8 (s, Ph). The carbon atom of tetrazolato ring, CN4 and of carbodiimido ligand, NCN, was not confirmed due to weak intensity. 31P{1H} NMR (CDCl3, d):
12.3(s). Anal. Calc. for C23H32N2P2Pd: C, 54.72; H, 6.39; N, 5.55. Found: C, 54.32; H, 6.51; N, 5.86%. Complex 5, trans-[Pd(C„CPh)(N@C@NAC6H3– 2,6-Et2)(PMe3)2], was analogously prepared (52%). IR (KBr, cm
1): 2170 (s, br, N@C@N), 2122 (w, br, C„C). 1H NMR (CDCl3, d): 1.24 (t, 6 H, J = 7.5 Hz, CH2CH3), 1.54 (t, 18 H, J = 3.5 Hz, PMe3), 2.79 (q, 4 H, J = 7.5 Hz, CH2), 6.77–6.79 (m, 1 H, Ph), 6.81–6.93 (m, 2 H, Ph), 6.93–7.31 (m, 5 H, Ph). 13C{1H} NMR (CDCl3, d): 14.5 (t, J = 15 Hz, P(CH3)3), 14.7 (s, CH3), 25.5 (s, CH2), 94.9 (t, J = 19 Hz, Ca„C), 108.0 (t, J = 5.6 Hz, C„Cb), 119.4, 125.6, 126.6, 127.3, 127.7, 130.4, 130.6, 143.8 (s, Ph). The carbon atom of tetrazolato ring, CN4, was not confirmed due to weak intensity. 31P{1H} NMR (CDCl3, d):
12.3 (s). Anal. Calc. for C25H36N2P2Pd: C, 56.34; H, 6.81; N, 5.26. Found: C, 56.35; H, 6.90; N, 5.29%. Complex 6, trans-[Pd(C„CPh)(CN4-t-Bu)(PMe3)2] (0.227 g, 66%). IR (KBr, cm
1): 2102 (w, C„C). 1H NMR (CDCl3, d): 1.37 (t, 18 H, J = 3.5 Hz, PMe3), 1.79 (s, 9 H, C(CH3)3), 7.16–7.35 (m, 5 H, Ph). 13 C{1H} NMR (CDCl3, d): 15.6 (t, J = 16 Hz, P(CH3)3), 31.3 (s, C(CH3)3), 57.7 (s, C(CH3)3), 108.6 (t, J = 20 Hz, Ca„C), 109.6 (t, J = 3.7 Hz, C„Cb), 125.8, 127.5 (br t), 128.1, 130.9 (t, J = 1.2 Hz), 164.0 (t, J = 9.2 Hz, CN4). 31P{1H} NMR (CDCl3, d):
13.9 (s). Anal. Calc. for C19H52N4P2Pd: C, 47.07; H, 6.65; N, 11.56. Found: C, 47.16; H, 6.60; N, 11.58%. Complex 7, trans-[Pd(C„CPh)(CN4-t-Bu)(PEt3)2] (41%). IR (KBr, cm
1): 2107 (s, C„C). 1H NMR (CDCl3, d): 1.13 (q, 18 H, J = 7.9 Hz, P(CH2CH3)3), 1.71 (m, 12 H, P(CH2CH3)3), 1.79 (s, C(CH3)3), 7.15– 7.30 (m, 5 H, Ph). 13C{1H} NMR (CDCl3, d): 8.17 (s,

P(CH2CH3)3), 16.4 (t, J = 14 Hz, P(CH2CH3)3), 31.1 (s, C(CH3)3), 57.6 (s, C(CH3)3), 108.3 (t, J = 19 Hz, Ca„C), 109.6 (t, J = 3.7 Hz, C„Cb), 125.4, 128.0, 128.1 (br t), 130.6 (t, J = 1.2 Hz), 162.8 (t, J = 10 Hz, CN4). 31P{1H} NMR (CDCl3, d): 15.6 (s). Anal. Calc. for C25H44N4P2Pd: C, 52.77; H, 7.79; N, 9.85. Found: C, 52.99; H, 7.90; N, 10.32%. Complex 8, trans-[Pd(C„CAC(O)OMe)(CN4-tBu)(PMe3)2] (86%). IR (KBr, cm
1): 2110 (s, C„C), 1694 (s, br, CO). 1H NMR (CDCl3, d): 1.34 (t, 18 H, J = 3.7 Hz, PMe3), 1.76 (s, 9 H, C(CH3)3), 3.70 (s, 3 H, Me). 13C{1H} NMR (CDCl3, d): 15.3 (t, J = 16 Hz, P(CH3)3), 31.2 (s, C(CH3)3), 51.8 (s, Me), 57.7 (s, C(CH3)3), 101.4 (t, J = 3.7 Hz, C„Cb), 117.5 (t, J = 20 Hz, Ca„C), 154.2 (s, C(O)O), 164.0 (t, J = 9.2 Hz, CN4). 31P{1H} NMR (CDCl3, d):
13.7 (s). Anal. Calc. for C15H30N4O2P2Pd: C, 38.60; H, 6.48; N, 12.00. Found: C, 38.22; H, 6.47; N, 11.81%. 3.4. Reactions with organic isothiocyanates To a Schlenk flask containing [Pd(N3)(C„CPh)(PEt3)2] (0.207 g, 0.43 mmol) were added CH2Cl2 (2 ml) and 2,6-dimethylphenyl isothiocyanate (0.076 g, 0.47 mmol) in sequential order. After stirring for 18 h at room temperature, the reaction mixture was completely evaporated under vacuum and then the resulting residue was solidified with hexane. The solids were filtered and washed with hexane (5 ml · 2). Recrystallization from CH2Cl2/ether gave pale yellow crystals of 9, trans-[Pd(C„CPh)(SCN4–C6H3-2,6-Me2)(PEt3)2] (0.227 g, 82%). IR (KBr, cm
1): 2111 (s, C„C). 1H NMR (CDCl3, d): 1.18 (q, 18 H, J = 8.1 Hz, P(CH2CH3)3), 1.92 (m, 12 H, P(CH2CH3)3), 2.04 (s, CH3), 7.17–7.33 (m, 8 H, Ph). 13C{1H} NMR (CDCl3, d): 8.38 (s, P(CH2CH3)3), 15.7 (t, J = 14 Hz, P(CH2CH3)3), 17.7 (s, CH3), 108.1 (s, Ca„C), 125.7, 127.7, 128.1, 128.4, 129.9, 130.7 (t, J = 2 Hz), 133.7, 136.1, 163.7 (s, CN4). 31P{1H} NMR (CDCl3, d): 15.1 (s). Anal. Calc. for C29H44N4P2SPd: C, 53.66; H, 6.83; N, 8.63. Found: C, 53.53; H, 6.74; N, 8.39%. Complex 10, trans-[Pd(C„CPh)(SCN4–Et)(PMe3)2] (61%), was similarly prepared. IR (KBr, cm
1): 2113 (s, C„C). 1H NMR (CDCl3, d): 1.49 (t, J = 7.3 Hz, 3 H, CH3), 1.51 (t, 18 H, J = 3.5 Hz, PMe3), 4.33 (q, J = 7.3 Hz, 2 H, CH2), 7.17–7.34 (m, 5 H, Ph). 13 C{1H} NMR (CDCl3, d): 14.2 (s, CH3), 14.9 (t, J = 16 Hz, P(CH3)3), 42.1 (s, CH2), 107.8 (t, J = 5.6 Hz, C„Cb), 126.0, 128.1, 130.8, 161.6 (br s, CN4). The carbon atom of Ca was not confirmed due to weak intensity. 31P{1H} NMR (CDCl3, d):
12.7 (s). Anal. Calc. for C17H28N4P2SPd: C, 41.77; H, 5.77; N, 11.46. Found: C, 41.47; H, 5.83; N, 11.03%. Complex 11, trans-[Pd(C„CPh)(SCN4–C6H3-2,6Me2)(PMe3)2] (71%): IR (KBr, cm
1): 2112 (s, C„C). 1 H NMR (CDCl3, d): 1.55 (t, 18 H, J = 3.7 Hz,

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P(CH3)3), 2.03 (s, CH3), 7.17–7.35 (m, 8 H, Ph). 13 C{1H} NMR (CDCl3, d): 14.9 (t, J = 16 Hz, P(CH3)3), 17.8 (s, CH3), 107.9 (t, J = 5.6 Hz, C„Cb), 126.0, 127.2, 128.1, 128.5, 130.1, 130.8 (t, J = 2 Hz), 133.5, 136.1, 162.6 (br s, CN4). The carbon atom of Ca was not confirmed due to weak intensity. 31P{1H} NMR (CDCl3, d):
13.7 (s). Anal. Calc. for C23H32N4P2SPd: C, 48.90; H, 5.71; N, 9.92. Found: C, 48.71; H, 5.83; N, 9.56%. Complex 12, [(PEt3)2(C„CPh)Pd(SCN4-(l-C6H4)– SCN4)Pd(C„CPh)(PEt3)2] (37%): IR (KBr, cm
1): 2113 (s, C„C). 1H NMR (CDCl3, d): 1.19 (q, 36 H, J = 8.3 Hz, P(CH2CH3)3), 1.90 (m, 24 H, P(CH2CH3)3), 2.04 (s, CH3), 7.17–7.33 (m, 10 H, Ph), 8.23 (s, 4 H, Ph). 13 C{1H} NMR (CDCl3, d): 8.37 (s, P(CH2CH3)3), 15.7 (t, J = 14 Hz, P(CH2CH3)3), 98.5 (br, Ca„C), 108.0 (s, t, J = 5.6 Hz, C„Cb), 123.7, 125.8, 127.7, 128.1, 130.7 (t, J = 2 Hz), 135.6, 162.6 (s, CN4). 31P{1H} NMR (CDCl3, d): 17.9 (s). Anal. Calc. for C48H74N8P4S2Pd2: C, 49.53; H, 6.41; N, 9.63. Found: C, 49.27; H, 6.33; N, 10.06%. FAB mass spectrum: m/z 1164 (M+). 3.5. Reactions with organic nitriles To a Schlenk flask containing complex 1 (0.258 g, 0.64 mmol) were sequentially added CH2Cl2 (3 ml) and C6F5CN (0.372 g, 1.92 mmol). After stirring for 14 h at room temperature, the reaction mixture was completely evaporated under vacuum, and then the resulting residue was solidified with ether. The solids were filtered and washed with hexane (3 ml · 2). Repeated recrystallization from CH2Cl2/hexane gave white crystals of 13, trans-[Pd(C„CPh)(N4C–C6F5)(PMe3)2] (0.142 g, 37%). IR (KBr, cm
1): 2125 (s, C„C). 1H NMR (CDCl3, d): 1.42 (t, J = 3.8Hz, PMe3), 7.20–7.35 (m, Ph). 13C{1H} NMR (CDCl3, d): 14.1 (t, J = 16 Hz, P(CH3)3), 109.0 (t, J = 3.7 Hz, C„Cb), 126.3, 128.1, 128.2, 130.9 (t, J = 2 Hz). The carbon atom (CN4) of the tetrazolato ring was not confirmed due to its weak intensity. 31P{1H} NMR (CDCl3, d):
12.6 (s). Anal. Calc. for C21H23N4F5P2Pd: C, 42.41; H, 3.90; N, 9.42. Found: C, 42.56; H, 4.14; N, 9.15%. To a Schlenk flask containing complex 2 (0.150 g, 0.31 mmol) were added CH2Cl2 (4 ml) and Me3SiCN (0.092 g, 0.62 mmol) in sequential order. After stirring for 18 h at room temperature, the reaction mixture was fully evaporated, treated with diethyl ether, and then stored at freezer to give white solids. The solids were filtered and washed with ether (3 ml · 2) to give white solids of [Pd(CN)2(PEt3)2] (15) in a trace amount. The collected filtrate was evaporated to give white solids. Recrystallization from diethyl ether/hexane gave white crystals of 14, trans-[Pd(C„CPh)(CN)(PEt3)2] (0.124 g, 85 %). IR (KBr, cm
1): 2108 (s, C„N and C„C). 1H NMR (CDCl3, d): 1.21 (q, 18 H, J = 7.9 Hz, P(CH2CH3)3), 2.06 (m, 12 H, P(CH2CH3)3), 7.15–

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7.28 (m, 5 H, Ph). 13C{1H} NMR (CDCl3, d): 8.49 (s, P(CH2CH3)3), 17.3 (t, J = 15 Hz, P(CH2CH3)3), 105.0 (t, J = 17 Hz, Ca„C), 110.9 (t, J = 4 Hz, C„Cb), 125.8, 127.6 (t, J = 2 Hz), 128.1, 130.7 (t, J = 1.2 Hz), 136.0 (t, J = 13 Hz, CN). 31P{1H} NMR(CDCl3, d): 20.3 (s). Anal. Calc. for C21H35NP2Pd: C, 53.68; H, 7.51; N, 2.98. Found: C, 53.33; H, 7.67; N, 3.01%. Complex 15 was independently prepared by the following method. To a Schlenk flask containing complex 2 (0.350 g, 0.82 mmol) were sequentially added CH2Cl2 (5 ml) and Me3SiCN (0.203g, 2.05 mmol). After stirring for 18 h at room temperature, the reaction mixture was fully evaporated to give white solids. The solids were filtered and washed with ether (3 ml · 2) to give white solids of 15, [Pd(CN)2(PEt3)2] (0.300 g, 93% ). IR (KBr, cm
1): 2123 (s, C„N). 1H NMR (CDCl3, d): 1.21 (q, 18 H, J = 8 Hz, P(CH2CH3)3), 2.08 (m, 12 H, P(CH2CH3)3). 13C{1H} NMR (75 MHz, CDCl3, d): 8.41 (s, P(CH2CH3)3), 17.6 (t, J = 15 Hz, P(CH2CH3)3), 130.8 (t, J = 15 Hz, CN). 31P{1H} NMR (CDCl3, d): 20.0 (s). Anal. Calc. for C14H30N2P2Pd: C, 42.59; H, 7.66; N, 7.10. Found: C, 42.83; H, 7.85; N, 7.25%. Complexes 17–19 were analogously prepared. Complex 17, [Pd(CN)2(PMe3)2] (94%). IR (KBr, cm
1): 2123 (CN). 1H NMR (CDCl3, d): 1.70 (br s, PMe3). 13 C{1H} NMR (CDCl3, d): 16.4 (s, P(CH3)3), 131.2 (s, CN). 31P{1H} NMR (CDCl3, d):
14.8 (s). Anal. Calc. for C8H18N2P2Pd: C, 30.93; H, 5.84; N, 9.02. Found: C,31.05; H, 5.88; N, 8.87%. Complex 18, [Pd(CN)2(depe)] (87%). IR (KBr, cm
1): 2127 (CN). 1H NMR (CDCl3, d): 1.28 (dt, 12 H, J = 7.6 Hz, P(CH2CH3)2) 2.13 (m, 12 H, PCH2). 13C{1H} NMR (CDCl3, d): 9.09 (s, P(CH2CH3)3), 19.3 (dd, J = 2 Hz, 30 Hz, PCH2), 24.0 (d, J = 43 Hz, PCH2), 24.0 (dd, J = 11 Hz, 9.0 Hz, PCH2), 130.9 (dd, J = 128 Hz, 19 Hz, CN). 31 P{1H} NMR (CDCl3, d): 9.09 (s). Anal. Calc. for C12H24N2P2Pd: C, 39.52; H, 6.63; N, 7.68. Found: C, 39.86; H, 6.75; N, 7.62%. Complex 19, [Ni(CN)2(PEt3)2] (86 %). IR (KBr, cm
1): 2104 (CN). 1H NMR (CDCl3, d): 1.24 (q, 18 H, J = 8 Hz, P(CH2CH3)3), 2.01 (m, 12 H, P(CH2CH3)3). 13C{1H} NMR (CDCl3, d): 8.38 (s, P(CH2CH3)3), 17.0 (t, J = 15 Hz, P(CH2CH3)3), 133.6 (t, J = 35 Hz, CN). 31P{1H} NMR (CDCl3, d): 24.8 (s). Anal. Calc. for C14H30N2P2Ni: C, 48.45; H, 8.71; N, 8.07. Found: C, 48.78; H, 8.51; N, 7.86%. 3.6. X-ray structure determination All X-ray data were collected with a Siemens P4 diffractometer equipped with a Mo X-ray tube and a graphite-crystal monochromator. Intensity data were empirically corrected for absorption with w-scan data. All calculations were carried out with the use of SHELXTL programs [33]. All structures were solved by direct methods. All non-hydrogen atoms were refined

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anisotropically. All hydrogen atoms were generated in ideal positions and refined in a riding mode. [10] [11]

4. Supplementary material [12]

Crystallographic data for the structural analysis have been deposited at the Cambridge Crystallographic Data Centre, CCDC Nos. 232839–232842 for compounds 5, 6, 11, and 18. Copies of this information may be obtained free of charge from: The director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +441223-336-033; e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk).

Acknowledgement This work was supported by Grant R05-2002-00000559-0 from the Basic Research Program of the Korea Science and Engineering Foundation.

[13] [14]

[15]

[16] [17] [18] [19]

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