POryhedron Vol. 3, No. 3, pp. 317-323, 1984 Printed in Great Britain.

0277-5387/84 S3.00 + .OO 0 1984 krgamon Ress Ltd.

FURTHER STUDIES ON ORGANONICKEL COMPOUNDS: THE SYNTHESIS OF SOME NEW

ALKYL-, ACYL- AND CYCLOPENTADIENYL- DERIVATIVES AND THE CRYSTAL STRUCTURE OF

TRANS- ~i(CH,SiMe,),(PMe3)2]

ERNEST0 CARMONA,* MARGARITA PANEQUE and MANUEL L. POVEDA Departamento de Quimica Inorginica, Facultad de Quimica, Universidad de Sevilla,

Sevilla, Spain

ROBIN D. ROGERS* Department of Chemistry, Northern Illinois University, Dekalb, IL 60115, U.S.A.

and

JERRY L. ATWOOD* Department of Chemistry, University of Alabama, University, AL 35486, U.S.A.

(Received 28 June 1983; accepted 25 July 1983)

Abstract-The complex [NiCl,(PMe,),] reacts with one equivalent of Mg(CH,CMe,)Cl to yield the monoalkyl derivative trans-[Ni(CH,CMe,)Cl(PMe,)j, which can be carbonylated at room temperature and pressure to afford the acyl [Ni(COCH,CMe,)Cl(PMe,),1. Other related alkyl and acyl complexes of composition [Ni(R)(NCS)(PMe,M (R = CH,CMe,, COCH,CMe,) and [Ni(R)(q-C,H,)L] (L = PMe,, R = CH,CMe,, COCH,CMq; L = PPh,, R = CH,CMe,Ph) have been similarly prepared. Dialkyl derivatives [NiR,(dmpe)] (R = CH,SiMe,, CH,CMe,Ph; dmpe = 1,2_bis(dimethylphosphine)ethane, Me2PCH2 CH,PMe,) have been obtained by phosphine replacement of the labile pyridine and NNN’N’-tetramethylethylenediamine ligands in the corresponding [Ni(CH,SiMe,),@y)d and [Ni(CH2CMe2Ph)z(tmen)] complexes. A single-crystal X-ray determination carried out on the previously reported trimetylphosphine derivative [Ni(CH,SiMe,)z(PMe,)d shows the complex belongs to the orthorhombic space group Pbcn, with a = 14.345(4), b = 12.656(3), c = 12.815(3) A, Z = 4 and R 0.077 for 535 independent observed reflections. The phosphine ligands occupy mutually tram positions P-Ni-P 146.9(3)0 in a distorted square-planar arrangement.

In spite of the high reactivity and instability often associated with a-bonded organonickel(I1) com- pounds, a large number of alkyl and acyl deriva- tives of composition [NiX(R)LJ and miR,LJ is already known.’ As a continuation of our own work in this area,2 we have carried out the syn- thesis and characterization of several new alkyl- and acyl-complexes of Ni(I1) stabilized by phos- phine ligands. This paper deals with (i) neopentyl- and neopentylcarbonyl-complexes of composition

W(R)X(PMe3M and lYWOWWMe3)21 (X = Cl,NCS), (ii) cyclopentadienyl derivatives

*Authors to whom correspondence should be addressed.

lNi(R)(q -C,H,)L] (L = PMe,, R = CH,CMe,; L = PPh,, R = CH,CMe,Ph) and [(C,H,)Ni- (COCH,CMe,)(PMe,)] and (iii) dialkyl complexes [NiR,(dmpe)] (R = CH,SiMe,, CH,CMe,Ph; dmpe = Me,PCH,C H2PMe2). In addition, the crystal structure of the previously preparedZb PMe, deriv- ative [Ni(CH2SiMe,)2(PMe3)2] is also reported. Analytical and spectral data for the new com- pounds are collected in Table 1.

RESULTS AND DISCUSSION

[Ni(CH,CMe,)X(PMe,),] and [Ni(COCH,CMe,)- X(PMe,)J complexes

The addition of 1 equiv of the Grignard reagent

317

318 E. CARMONA et al.

Table 1. Analytical and spectroscopic data for the new alkyl- and acyl-derivatives of nickel(W

AnalysIsa %I IWR data0

IUCH cr Compound CaloUr C H Me-P orCEMe W_&13 Othera

(1) [Ni(CH,Care3)Cl(~~[e3~2~ Yellow 41.6 (41.3) (%

I.24btg 1.428 0.72bth

(2) (Ia(COCIi2CI!le3)(:l(WIe3)21 YellowC (t::;) (E,

f 1.3Ibe 0.94s 2.98s

(3) [N~(cH~c~~~~~)(I~s)(~~I~~)~‘] Orangea (t:::) (%b

l.IObs I.299 0.47bs

(4) [Ni(COCH2CMe3)(NCS)(~e3)23 YellowC'd (4% (5:;)

f 1.23ba 0.866 2.81e

(5) [(7'C5H5,)Ni(CI12~~e3)(PMe3)1 Green 57.9 (57.6) (k:,

0.97di 1.276 0.95di 5.356 (CP)

(6) [(7-C5H5)Ni(CWH2CMe3)(PMe3j] RedC 56.0 (56.2) (::t,

I.OIdi I.198 3.018 5.346 (CP)

(7) [(p-C5H5)NI(CH2CMe2Ph)(PPh3)] Green (E) (66%

I.348 I. 302 5.IOa (CP)

(8) [Ni(CH2Sia~e3)2(dmPe)] Yellow tt:::, (E,

1.04dj 0.45s _ 0,23mk 0.93&x$PP)

(9) [Ni(CH,C~e,Ph),(dmPe)] Yellow 65.0 (65.7) &

0.70dj 1.86~ I.86mk 0.82mk(CH2P)

aCalculeted values are in parentheses. bNS 4.1 (4.1). ' s(CO) 1650 cm-'. d ~(NCS) 2085 cm-'.

eIn C6H6 solution. 'In CH2C12. gJ(HP)app = 35. hJ(HP) 14Eis. iJ(HP) 9H5. ‘J(HP) 8Hs. kCcmplex multlplet.

Mg(CH,CMe,)Cl to a suspension of lJGCl,(PMe,)J in Et,0 produces [Ni(CH,CMe,)Cl (PMe,),], (l), as yellow-brown crystals, in 60% yield. Formation of the dialkyl derivative is not detected, and the use of an excess of the alkylating reagent produces instead extensive decomposition and hence lower yields in complex 1.

IR and ‘H NMR spectroscopic studies suggest 1 has a tram stereochemistry similar to that found for other wi(R)X(PMe,),J complexes.2” Thus, the ‘H NMR spectrum shows, in the methyl- phosphine region, a triplet at 6 1.24 ppm charac- teristic of bis-phosphine complexes with strong coupling between the phosphorus nuclei; a slightly broad triplet, at 0.72 ppm, is due to coupling of the NiCH,R protons to two equivalent phosphorus nuclei. In the presence of traces of free PMe,, these signals collapse to singlets, clearly indicating fast exchange of free and complexed PMe,, possibly through a 5-coordinate intermediate species.3 For- mation of j-coordinate derivatives is well documented1*3*4 for complexes of this type and species of this sort have been postulated as inter- mediates in a number of their reactions, e.g. CO or alkyne insertions into the Ni-C bonds.

On bubbling CO through a solution of 1, at room temperature and pressure, a smooth, essen- tially quantitative reaction takes place, with formation of the corresponding acyl,

[Ni(COCH,CMe3)C1(PMe3)~, (21, eqn (11,

[Ni(CH,CMe,)Cl(PMe,)J + CO-,

/Ni(COCH,CMe3)C1(PMe3)z]. (1)

Complex 2 is a yellow crystalline very thermally stable solid, which can be indefinitely stored at room temperature under N2, without noticeable loss of carbon monoxide. Although sparingly solu- ble in petroleum it is very soluble in Et,O, THF and aromatic hydrocarbons. While the presence of a strong IR band at ca. 1650 cm-’ clearly indicates the existence of an acyl group coordinated to the nickel atom in the normal or monohapto fashion, the similarity of its ‘H NMR spectrum with that of 1, is again indicative of tram geometry. Both 1 and 2 react with KNCS in acetone or tetrahydrofuran (THF) to yield the corresponding thiocyanate de- rivatives [Ni(CH,CMe3)(NCS)(PMe3)& (3) and [Ni(COCH,CMe,)(NCS)(PMe,),l, (4) in high yield. Pertinent IR and ‘H NMR data for these com- plexes are included in Table 1 and require no further comment.

Cyclopentadienyl derivatives pi(R)(q-C,H,)L] and

INWW~ -W-WI Although complexes of composition

miR(t&H,)] are still unknown, closed-shell de- rivatives of the type [NiR(q-C,H,)L], in which the

Further studies on organonickel compounds 319

Ni(R)Cp unit is stabilized by a donor ligand have been known for many years.’ More recently we have showr? that the neophyl derivative [Ni(CH,CMe,Ph)Cl(PMe&j reacts almost in- stantly with TlCp, in acetone, to afford

lNiR(rl -GHdPM41, ew (2),

wi(CH,CMe,Ph)C1(PMes)d + TlCp+

[Ni(CH,CMe,Ph)(q -C,H,)(PMe,)] + PMe, + TlCl. (2)

Surprisingly, no reaction is observed when complex 1 and TlCp are stirred in acetone, at room temperature, for a period of ca. 2-3 hr. The neopentyl derivative, [Ni(CH,CMe,)(q - C,H,)(PMe,)], (5), can however be obtained in high yield by using the more nucleophilic NaCp in diethyl ether solution. By an analogous pro- cedure, the corresponding acyl derivative [Ni(COCH,CMe,)(q-C,H,)(PMe,)], (6) can be ob- tained from 2 and NaCp. It is important to note that complex 6 is not formed when 5 is reacted with carbon monoxide. The lack of reactivity towards CO can be explained by the inability of the complex to dissociate PMe, to form a reactive, sixteen- electron intermediate. This is in accord with the results of ‘H NMR studies carried out for this and other related compounds.28

Infrared and ‘H NMR studies for complexes 5 and 6 are in agreement with the proposed formu- lations (see Table 1). Thus a singlet is observed for the Cp protons, indicating pentahapto coordi- nation to the nickel atom, while the neopentyl- methylene protons in 5 give rise to a doublet, with J(H-P) 9 Hz. On the other hand the addition of free PMe, to solutions of either 5 or 6 produces no changes in the spectrum, separate responses being observed for the free and the coordinated ligand. Thus, phosphine dissociation, if any, must be slow on the NMR time scale.

Finally, interaction of the complex miCl(q-C,H,)(PPh,)] with the neophyl Grignard reagent takes place as in eqn (3), affording the corresponding alkyl derivative 7

INiCl@-C,H,)(PPh,)] + Mg(R)Cl-,

[Ni(R)(q-C,H,)(PPh,)] + MgCl, R = CH*CMe,Ph.

(3)

The neophyl derivative 7 is a green crystalline solid, moderately air stable, which shows physical and spectral properties similar to those of the previously reported trimethylsilylmethyl and neo- pentyl analogues.‘~5

Dialkyl complexes [NiR,(dmpe)]. The X-ray struc- ture of [Ni(CH,SiMe,),(PMe,)d.

Although dialkyl derivatives of Ni(I1) of com- position miR,Lrj cannot be preparedzb by reacting miCl,q complexes with an excess of the Grignard reagent, a number of complexes of this type can be obtained in good yields by taking advantage of the facility with which the unstable complexes mi(CH,SiMe,),(py)d and [Ni(CH,CMe,Ph),(tmen)] lose the nitrogen-containing ligands in solution. Using this we have now carried out the synthesis of the dmpe analogues miR,(dmpe)], eqn (4),

W(CH2SiMe&yM + dmpe-+

[Ni(CH,SiMe,),(dmpe)], 8 + 2py

~i(CH,CMe,Ph),(tmen)] + dmpe+

pi(CH,CMe,Ph),(dmpe)], 9 + tmen. (4)

Compounds 8 and 9 can be isolated as yellow, air-sensitive crystals, which are soluble in petro- leum, benzene and non-hydrocarbon solvents.

Table 2. Crystal data and summary of intensity data collection and structure refinement

Wd Ni(CH2SMe3)2@fe3)2

Ma1 Wt. 385.3

Space group Pbcn

Cell constants

a. ; 14.345(4)

0 b, A 12.656(3)

0 c. A 12.815(3)

O3 Cell vol. A 2326.6

Molecules/unit cell 4

-3 p'(dalc), B cm 1.10

-1 P(calC), cm 10.58

Radiation &Ku

Max crystal dimension, m 0.25 x 0.40 x 0.55

Scan width 0.80 + 0.20 tane

Standard reflections 600, 040, 004

Decay of standards 39%

Reflections mea&lured 1012

28 range 36'

Reflections collected 535

No. of parameters varied 87

COF 1.93

R 0.077

Rw 0.076

320 E. CARMONA et al.

For R = CH,CMe,, the instability of the pyri- dine or tmen intermediates has precluded iso- lation of analytically pure samples of

INW-WW2(dmpe)l. While the IR spectra of 8 and 9 show absorp-

tions characteristic of the alkyl and phosphine ligands, the ‘H NMR spectra are complex, due not only to the complexity of the spin system involved but also because of fortuitous similarities in the chemical shifts of some of the phosphine and alkyl groups protons. This makes the assignment of the resonances difficult and therefore, in some cases (see Table l), we merely point out the position of the bands. The chemical shifts observed for the P-Me protons have similar values to those found in other dmpe complexes.6

We have shown recently that addition of a slight excess of PMe, to a petroleum solution of cis-[Ni(CH,SiMe,),(py),] yields [Ni(CH,SiMe,),- (PMe,)J in almost quantitative yield.2b ‘H and 3’P NMR studies for this complex suggest the presence in solution of cis and tram isomers in a ca. 4: 1 ratio, the isomerization being slow on the NMR time scale, even in the presence of free base. An X-ray crystal structure determination shows the tram geometry to be the preferred in the solid state. The molecular structure and atom-labeling scheme

for [Ni(CH,SiMe,),(PMe,)J are presented in Fig. 1. The molecule resides on a crystallographic two- fold axis containing the Ni atom. The overall geometry is that of a distorted square-planar ar- rangement with trans-phosphines (P-Ni-P’ = 146.9(3)“-Table 3).

Although high standard deviations in the bond distances and angles, a result of crystal decom- position (see experimental section), rule out a detailed study of the bonding in the title com- pound, some comparisons can be made. The Ni-P bond length, 2.158(4)& is somewhat shorter than the 2.206 and 2.201 A averages found for [Ni(CH2SiMe3)Cl(PMe3)Jti and Ni(COCH*Si- Me,)Cl(PMe,),,*” respectively. The title compound also exhibits a smaller P-Ni-P bond angle (146.9(3)” vs 164.0 and 167.6”). Correspondingly, a slightly longer Ni-C bond length of 2.08(2)A is found in [Ni(CH,SiMe,),(PMe,)J than in [Ni(CH,SiMe,)Cl(PMe,),1 (1.95A), mi(COCH,Si- Me,)Cl(PMe,),] (1.84A) and [Ni(CH,SiMe,),- (NC,H,),] (1.89( 1)A).2b The C-Ni-C angle in the title compound is 170(l)“.

EXPERIMENTAL

Microanalyses were by Pascher Microanalytical Laboratory, Bonn. The spectroscopic instruments

Fig. 1. Molecular structure and atom-labeling scheme for Ni(CH,SiMe,X(PMe,),. The atoms are represented by their 50% probability ellipsoids for thermal motion. The molecule resides on a

crystallographic two-fold axis.

Further studies on organonickel compounds

Table 3. Bond lengths (A) and bond angles (“) for Ni(CH,SiMe,)#Me,),

Atom xla

Ni 0.0000

P 0.1432(3)

Si -0.0080(4)

C(l) -0.023(l)

C(2) 0.118(l)

C(3) -0.086(2)

C(4) -0.034(2)

C(5) 0.150(l)

C(6) 0.2390)

C(7) 0.195(l)

Y/b

0.1291(3)

0.0805(4)

0.2789(5)

0.143(2)

0.336(2)

0.376(2)

0.293(2)

-0.051(2)

0.150(2)

0.055(2)

zlc

0.2500

0.2690(4)

0.4499(4)

0.409(l)

0.435(2)

0.385(2)

0.597(l)

0.217(2)

0.202(l)

0.398(2)

321

used were a Perkin-Elmer model 577 for IR spec- tra and a Perkin-Elmer Rl2A for ‘H NMR spec- tra. All preparations and other operations were carried out under oxygen-free nitrogen, following conventional Schlenk techniques. Solvents were dried and degassed before use. The light petroleum used had b.p. 4060°C. PMe3,7 NiCl,(PMe,),* and wiR,LJ(L = py, tmen)2b were prepared according to literature methods.

Chloro(neopentyl)bis(trimethylphosphine)nickel(ZZ)

(1) To a stirred suspension of llViCl,(PMe,)J (1.5 g,

cu. 5.3 mmol) in diethyl ether (80 cm’) cooled at - 60°C was added Mg(CH,CMe,)Cl (11.5 cm3 of a cu. 0.6 mol dmm3 diethyl ether solution, a slight excess). The mixture was stirred at this temperature for 30 min, then at 0°C for 2-3 hr, and finally at room temperature for 1 hr. The solvent was re- moved in uucuo and the residue extracted with 60 cm3 of light petroleum. The solution was centri- fuged and the product crystalized as light brown needles by removing part of the solvent and cool- ing at -30°C. Yield 60%.

Chloro(neopentylcarbonyl)bis(trimethylphosphine)- nickel(ZZ), (2)

Carbon monoxide was bubbled, at room tem- perature and pressure, through a solution of the alkyl-complex 1 (0.31 g, cu. 1 mmol) in diethyl ether (30 cm’) for about 10min. The resulting solution, which had considerably faded was evapo- rated to dryness, the residue dissolved in 20 cm3 of Et20 and the mixture centrifuged to remove a small amount of an insoluble material. Cooling overnight at - 30°C afforded the title compound as yellow microcrystals. They were filtered off and dried in uacuo. Yield 90%. Crystals of analytical

purity can be obtained by recrystallisation from Et,0 at 5°C.

Thiocyanate(neopentyl)bis(trimethylphosphine)nic- kel(ZZ), (3)

Complex 1 (0.3 g, cu. 1 mmol) and an excess of KNCS, previously dried by heating at 110°C for cu. 24 hr, were stirred in THF or acetone (20 cm3) for 1 hr at room temperature. The solvent was stripped off under reduced pressure and the residue extracted with an Et,O-petroleum mixture. After centrifugation and cooling at -30°C the product was obtained as golden plates in ca. 70% yield. The neopentylcarbonyl derivative, [Ni(COCH;CMe,)- (NCS)(PMe,)d (4), can be obtained similarly from [Ni(COCH,CMe,)(PMe,)J and KNCS. The com- pound crystallised as yellow microcrystals from Et,O-acetone.

(rl-cyclopentadienyl)neopentyl(trimethyle)- nickel(ZZ), (5)

A stirred solution of [Ni(CH,CMe3)Cl(PMe3)J, 1, (0.23 g, cu. 0.7 mmol) in Et20 (2Ocm’) was reacted at room temperature with an equi- molecular amount of NaCp (0.7cm3 of a cu. 1 .O mol dme3 diethyl ether solution). A fine precip- itate of NaCl immediately appeared and the colour of the solution changed to green-yellow. The mix- ture was stirred for 30 min and then evaporated to dryness. Petroleum ether was added (30 cm3) and the suspension centrifuged. Green-yellow crystals were obtained in cu. 75% yield after removing part of the solvent and cooling at -80°C.

The reaction of the acyl complex [Ni(COCH2CMe3)Cl(PMe3)J with NaCp was car- ried out in a similar way to give [Ni(q-C,H,) (COCH2CMe3)(PMe3)], (6), as red crystals from light petroleum.

322 E. CARMONA et al.

(n-cyclopentadienyl)neophyl(triphenyZphosphine) nickel (II), (7)

To a stirred and cold (-80°C) suspension of [(q-C,H,)NiCl(PPh,)] (0.84 g, cu. 2 mmol) in Et,0 (40cm3) 2 equiv of neophyl Grignard reagent (in Et,0 solution) were added via syringe. The cold bath was then removed and the mixture stirred at room temperature for l-2 hr until complete dis- sappearance of the red starting material. The sol- vent was removed in vacua and the residue extrac- ted with light petroleum (30 cm3). The green suspension was centrifuged and the volume of the solution partially reduced in vacua. Cooling at - 30°C afforded the product as green crystals in cu.

40% yield Analytically pure samples were obtained by recrystallisation of the crude product from petroleum at -30°C.

Bis(trimethylsilylmethyl)- and bis(neophyl)-( 1,2- bis(dimethyZphosphine)ethane)nickeZ(ZZ), (8) and

(9) To a solid sample of pi(CH,SiMe,),(py)J

(0.64 g, cu. 1.6 mmol) a cold (- 60°C) solution of dmpe (0.32cm3, cu. 1.6 mmol) in light petro- leum (20 cm3) was added. The mixture was allowed to reach room temperature with stirring, when the brown crystals of the pyridine complex dissolved to give a yellow solution. The stirring was continued for 30 min and the solvent evaporated to dryness. Extraction with petroleum (20 cm’) and cooling at - 30°C gave the title compound as yellow crystals in almost quantitative yield. The complex was recrystallised from petroleum at 5°C.

. . procedure starting

&CH,~~~~h)2(tmen)] afforded [N&k: CMe,Ph),(dmpe)] as yellow crystals from petro- leum in cu. 15% yield.

X-Ray data collection, structure determination and

refinement for [Ni(CH,SiMe,),(PMe,)J Single crystals of the air-sensitive compound

were sealed under N, in thin-walled glass capillar- ies. Final lattice parameters as determined from a least-squares refinement of ((sin 0)/n)* values for 15 reflections (0 > 20”) accurately centered in the diffractometer are given in Table 2. The space group was uniquely determined as Pbcn from the systematic absences.

Data were collected on an Enraf-Nonius CAD-4 diffractometer by the 8-28 scan technique. The method has been previously described.’ A sum- mary of data collection parameters is given in

tAtomic coordinates have also been deposited with the Cambridge Crystallographic Data Centre.

Table 2. During data collection the crystal slowly decomposed in the X-ray beam. The intensities were corrected for Lorentz, polarization, and, de- composition effects, but not for absorption.

Calculations were carried out with the SHELX system of computer programs.” Neutral atom scattering factors for Ni, P, Si and C were taken from Cromer and Waber,” and the scattering for nickel, was corrected for the real and imaginary components of anomalous dispersion using the table of Cromer and Liberman.‘* Scattering factors for H were from Ref. 13.

The position of the nickel atom was revealed by the inspection of a Patterson map. A difference Fourier map phased on the nickel atom readily revealed the positions of the nonhydrogen atoms. Least-squares refinement with isotropic thermal parameters led to R = Z [IF01 - (F,.II/cI~,I = 0.099. As a result of the problems associated with crystal decomposition, the hydrogen atoms could not be located and were not included in any refinement. Refinement with anisotropic temperature factors led to final values of R = 0.077 and R, = 0.076. A final difference Fourier showed no feature greater than 0.5 e-/A3. The weighting scheme was based on unit weights; no systematic variation of w(l~~l- IF,/) vs IF,I or (sin 0)/n was noted. The final values of the positional and thermal parameters have been deposited as supplementary material with the Editor, from whom copies are available on request.?

Acknowledgements-We thank the Spanish C.A.I.C.Y.T. (EC.) and the U.S.A. National Science Foundation (R.D.R. and J.L.A.)

1.

2.

3.

4.

5.

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Further studies on organonickel compounds 323

6. See for instance S. J. Holmes, D. N. Clark, H. W. Turner and R. R. Schrock, J. Am. Chem. Sot. 1982, 104, 6322.

7. W. Wolfsberger and H. Schmidbaur, Synth. React. Inorg. Met.-Org. Chem. 1974, 4, 149.

8. 0. Dahl, Acta Chem. Stand. 1969, 23, 2342. 9. J. Holton, M. F. Lapper-t, D. G. H. Ballard, R.

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10. SHELX, a system of computer programs for X-ray structures determination by G. M. Sheldrick, 1976.

11. D. T. Cromer and J. T. Waber, Acta Cryst. 1965, 18, 104.

12. D. T. Cromer and D. Liberman, J. Chem. Phys. 1970, 53, 1891.

13. International Tables for X-ray Crystallography, Vol. 4, p. 72. Kynoch Press, Birmingham (1974).