J.C.S. Faraduy I, 1980,76,2519-2530Complexation and Chemisorption of Trimethylphosphineon Ni ZeolitesBY ROBERT A. SCHOONHEYDT," DIRK VAN WOUWE AND HUGo LEEMANCentrum voor Oppervlaktescheikunde en Collo'idale Scheikunde,De Croylaan 42, B-3030 Leuven (Heverlee), BelgiumReceived 8th February, 1980After room temperature saturation of dehydrated NiY with trimethylphosphine two complexes areformed in the supercages. They are identified and quantified by reflectance spectroscopy as0.9[Ni(PMe3)J2+ per unit cell and W[(0,)3-Ni-PMe3]2+ per unit cell (0, is a lattice oxygen). Theformer is diamagnetic and trigonal bipyramidnl. the latter is paramagnetic and compressed tetrahedral.[Ni(PMe&I2 +. is only stable in excess PMe,, while the mono-phosphine complex is stable to z 383 K inuucuo.On NIX only the paramagnetic compressed tetrahedral complex is formed. The ligand fieldparameters of this complex were calculated.Chemisorption on lattice and extralattice oxygens gives strongly held O=PMe,, O=P (OMe3)3 and arange of decomposition products such as CO, COz, H20, hydrocarbons and oxygenated P on thesurface. These products were qualitatively identified by i.r. and mass spectrometry.The coordination of 3d transition metal ions in the zeolite cavities primarilydepends on the ligand field strength of surface oxygens relative to that of theadsorbed coordinating molecules. With ligands such as H20, NH,, ethylene-diammine and methylisocyanide the zeolite acts as a solvent. With ligands such asNO, CO, acetylene and olefins zeolitic oxygens remain in the coordination sphere.In this way unusual complexes can be stabilized on the surface.'Y2 The ultimategoal of these studies is not only to characterize these complexes but also to applythis knowledge to develop so-called "heterogenized homogeneous catalysts".,4Usually, these catalysts are phosphine-based. On zeolites, only the smallest ter-tiary phosphines can be adsorbed. Recently it was reported that PMe, reducedCu2+ to Cu' in zeolite Y, whereas on COY the formation of a low spin complex,formulated as lattice-bonded [Co(PMe,),] +, was evidenced by reflectance spec-troscopy and e . ~ . r . ~ * ~ These data illustrate the versatility of transition metal ionzeolites towards PMe3. In this paper we present our results on the interaction ofPMe, with NIX and NiY zeolites.Ni2+ is an interesting cation because the electro-nic spectra of Ni(PMe3)xX2 (x = 2 4 ) and of [Ni(PMe&I2' are well described inthe literature.'EXPERIMENTALSAMPLESLinde NaY and NaX were stirred for 1.728 x lo6 s in 0.1 moldmP3 solutions of NaC1,washed until Cl--free, air-dried and stored in a desiccator over saturated NH,Cl. Nix and NiYwere prepared from these stock samples by ion-exchange at room temperature for 8.64 x lo5 sin 0.01 moldmP3 NiC12 solutions at a so1id:liquid ratio of 1 gdmP3. After exchange, the2512520 Ni2+-PMe3 COMPLEXES ON ZEOLITESsamples were washed until Cl--free, air-dried and stored over saturated NH,Cl solution in adessicator prior to analysis.Chemical analysis for the exchangeable cation content yielded forNiY17:1.33meq Na'g-l, 2.66meqNi2+ g-' and 0.3meqH+g-'; for NiX28:4.17meqNi2+ g- ' and 2.04 meq Na' 8-l. The numbers following the sample symbols are the number ofNi2+ per unit cell.TRIMETHYLPHOSPHINEAn ampoule of PMe, from Strem Chemicals was connected to a vacuum line and frozen inliquid air. PMe, was purified by evacuation at liquid air temperature and then at slightly belowits freezing point. The mass spectrum after these treatments gave no indication of componentsother than PMe,.PROCEDURES AND TECHNIQUESREFLECT A N CE SPECTROSCOPYThe samples were treated simultaneously in the reflectance cells and the McBain balances,both connected to the same vacuum line, in order to attribute specific weight changes tospectral variations.Prior to adsorption of PMe, two pretreatments were performed. The firstone consisted of heating NiY17 and Nix28 in uucuo at 713 and 733 K, respectively, untilconstant weight. In the second pretreatment both samples were similarly dehydrated, O2 wasallowed to adsorb at room temperature and it was then desorbed at 373K until constantweight.Reflectance spectra of the pretreated samples were recorded before and after O2 adsorptionand after O2 removal. PMe, was allowed to adsorb at room temperature. During adsorptionthe samples were kept at ambient temperature with a water jacket around the reflectance cells.Reflectance spectra of the samples saturated with PMe, and after evacuation of PMe, wererecorded at several temperatures between 293 and 573 K.Spectra were recorded on a Cary 17instrument in the type I reflectance mode. The reference was BaSO,. The spectra were tape-recorded, computer-processed and plotted as F(R,) against wavenumber (5000-50000 cm- ')after subtraction of the baseline.INFRARED SPECTROSCOPY AND MASS SPECTROMETRYThin self-supporting zeolite wafers (5-10 mg cm-2) were dehydrated in uucuo at 683 K for3600 s prior to saturation with PMe,. 1.r. spectra were recorded after the pretreatment, aftersaturation with PMe, and after evacuation up to 573 K on a Beckman IR12 double beamgrating instrument in the range 1200-3800cm-'. For the analysis of the desorption productsz 2 g zeolite were connected to the empty i.r. cell through a side arm, pretreated as describedfor the reflectance measurements and saturated with PMe,.The gaseous desorption productswere collected in the i.r. cell and their spectra recorded in the range 1000-3800cm-'. For themass spectrometric analysis of the desorption products z500mg zeolite were loaded in aU-shaped quartz reactor, dehydrated and saturated with PMe, as described for the reflectancemeasurements. During desorption the gaseous desorption products circulated through the zeo-lite bed in a closed circuit. Aliquots of gases were conducted to the Balzers quadrupole massspectrometer QMG 101 A for analysis. The mass range analysed was 0-100.RESULTSPretreatment results in a weight loss which corresponds to 295 and 256 H 2 0UC-' for Nix28 and NiYl7, respectively.At room temperature Nix28 adsorbs 9-8O2 molecules per unit cell and NiY17 8.4. In both cases 5 O2 UC-' remainadsorbed after desorption at 373 K.The reflectance spectra obtained are identical to published spectra and are notreproduced her^.^.^ O2 has no effect on the spectrum of dehydrated Nix28 buR . A , SCHOONHEYDT, D. VAN WOUWE AND H . LEEMAN 2521eliminates the 14 100 cm-' band in the reflectance spectrum of NiY17. This bandwas previously ascribed to Ni +. * y 9The adsorption of PMe, is a fast, exothermic process. The zeolites in the reflec-tance cells must be kept in a constant temperature water bath to avoid excessiveheating. Table 1 gives the amount adsorbed after saturation and desorption atdifferent temperatures in vacuum.Only a minor fraction can be desorbed, even at473 K. This is indicative of chemisorption, while the colour changes accompanyingadsorption are in indirect proof of complexation of Ni2+. The numbers in table 1TABLE AMOUNTS OF PMe, ADSORBED (MOLECULES PER UNIT CELL)saturation with P(CH3j3desorption of P(CH3 j3at 323 Kat 373 Kat 418 Kat 473 K47.5 42.343.4 37.936.7 34.636.7 31.531.7 27.8are calculated as if the residual molecules on the surface are PMe,. Experiments tobe described below indicate that this is not the case due to chemisorption anddecomposition of PMe, upon high temperature evacuation. The adsorption of O2in the pretreatment step had no effect on the subsequent PMe, adsorption.REFLECTANCE SPECTROSCOPYTwo types of complexes are formed as evidenced by the reflectance spectra offig.1 and 2. One complex (I), only formed on NiY17, is characterized by absorptionbands at 18 300 and 34250 cm- '. These bands are removed by room temperatureevacuation of excess PMe,. The second complex (11) is formed on NiX28 and onNiY17 and is thermally stable up to 381 K. It is characterized by 3 bands in then.i.r.-visible region. The position of these band maxima are: 860&8800, 22000 and26000 cm- ' for NiX28; 800&8400, 21 000 and 26500 cm- ' for NiY17. While thefirst two bands are broad and asymmetric, the third is sharp. A broad absorptionencompasses the U.V. region, from which 3 bands are resolved upon desorption ofPMe, above 381 K. They are located at 33500, 38000 and 45000cm-1.Above381 K the spectra of the dehydrated Ni-zeolites are almost completely recovered,although in the U.V. region the 33 500 cm- band remains very pronounced.Thc disappearance of complex (I) on NiY 17 is accompanied by an increase in the8400 and 26 500 cm- ' bands of complex (11). These bands further increase withheating in vacuo up to 381 K. This increase in the intensity of the band withtemperature also occurs on NiX28. These phenomena are indicative of the fact thatcomplex (I) is transformed to complex (11) and that not all the Ni2+ is complexedafter saturation at room temperature.INFRARED SPECTROSCOPY A N D MASS SPECTROMETRYThe regeneration of lattice-bonded Ni2 +, as evidenced by reflectance spectro-scopy, is in contrast to the large amounts of residual PMe, on the surface.Chemi-sorption on lattice oxygens was suspected and this is shown by the ix. spectra offig. 3. Intense absorptions are found in the regions were gaseous PMe, absorb2522 Ni2+-PMe3 COMPLEXES ON ZEOLITES10'1 05 14 23 32 41wavenumber/103 cm-FIG. 2.-Reflectance spectra of PMe, adsorbed on NiX28: (1) saturated; (2) evacuated at 323 K for6.05 x 10's; (3) evacuated at 381 K for 3.24 x 10'sR . A . SCHOONHEYDT, D. VAN WOUWE AND H . LEEMAN 25233100 2900 1750 1550 1350wavenumber/cm -FIG. 3.-1.r. spectra of PMe, on NiY17: (1) evacuated at 683 K for 2700 s; (2) saturated with PMe,; ( 3 )evacuated at room temperature; (4) evacuated at 593 K for 7200 s.(1 282-1348, 141 7-1440 and 285G2970 cm- I).However, the forms of the band sys-tems are distorted with respect to those of gaseous PMe, (see fig. 4). Additionally, abroad asymmetric band around 1660 cm- is generated which intensifies with timeof contact. This band can be removed by evacuation at 373 K but for the elimin-ation of the low frequency shoulder at 1605 cm-' temperatures above 573 K arenecessary. This evacuation procedure leads to 3 groups of bands: a triplet withabsorption maxima at 1305, 1318 and 1345 cm-', a doublet with maxima at 1422and 1432 cm-' and a doublet with bands centered at 2922 and 2998 cm-'. Thelatter is broader than the former due to a low frequency shoulder. The i.r. spectra ofthe gaseous desorption products are shown in fig. 4. PMe, is the only desorptionproduct at 383 K (spectrum 1).At 438 K supplementary bands are revealed at1080crn-' (a weak broad band at 1140cm-' accompanies the 1080cm-' band)and in the CH stretching region, but only a band at 2885 cm-' is clearly resolvedfrom the C-H stretching of PMe3. Above 473 K the rotation-vibration spectrumof CH4 is superposed on the PMe, spectrum. The band centres of the CH4 spec-trum are at 3010 and 1310cm-'.The mass spectral analysis (fig. 5) of the gaseous desorption products confirmsand complements the i.r. data in that PMe3 is the main detectable desorptionproduct below 423 K, but it remains visible in the gas phase at all desorptiontemperatures. At z 500 K CH4 is detected, also in agreement with the i.r. data. Notdetectable by i.r. spectroscopy but clearly visible in the mass spectra are (i) H2which starts to desorb at ~ 4 5 3 K and (ii) a range of products, all of which aredesorbed above ~4450 K.They have characteristic masses at 27, 28, 29, 30 and 322524 Ni2+-PMe3 COMPLEXES ON ZEOLITES3200 2800 1500 1300 1100wavenumber/cm -FIG. 4.--I.r. spectra of gaseous desorption products of PMe,-saturated NiY 17 : (1) after desorption at383 K, p = 20.79 Pa; (2) after desorption at 438 K, p = 48.52 Pa; (3) after desorption at 483 K,p = 138.63 Pa; (4) after desorption at 553 K, p = 97.04 Pa.at 41,42,43,44 and at 71, 72 and 73. There is considerable overlap with the PMe,spectrum, but at the highest temperatures (spectra 4 and 5 ) these masses are clearlyvisible. There is also an effect due to the pretreatment: NiY17 pretreated in O2gives greater quantities of masses 43 and 44 than 41 and 42.The reverse holds forpretreatment il.7 vacuo. Desorption from Nix28 gives the same products but theamount of PMe3 with respect to the other products i s higher than for NiY17.dFIG. 5.-Mass spectra of PMe, and of products desorbed from NiY17 after saturated with PMe3: (1)PMe,; (2) desorption at 453 K; ( 3 ) desorption at 473 K; (4) desorption at 507 K; (5) desorption at 638 KR . A . SCHOONHEYDT, D . VAN WOUWE AND H . LEEMAN 2525DISCUSSIONThe reflectance spectra of Ni-zeolites saturated with PMe, can be interpreted interms of 2 Ni2+-PMe3 complexes without recourse to reduction of Ni2+ as in thecase of C U ~ + . ~ This is in agreement with the fact that in dehydrated faujasite-typezeolites Cu2+ is more easily reducible than Ni2+, not only by H2 but also by othermolecules such as CO, NH3 and ethylenediammine.' O-' This difference in behav-ior conforms with the difference in electrochemical potential^'^ and with ligandfield calculations.'The spectrum of complex (I) is interpreted as that of a spin-paired[Ni(PMe3),I2+ complex.The spectrum of complex (11) is ascribed to a high spinpseudotetrahedral species [(O,),Ni--PMe,] + where 0, stands for lattice oxygen.Evidence for these interpretations is given below.The known complexes of Ni2+ with PMe3, Ni(PMe,),X, (x = 2, 3, 4) and[Ni(PMe3),I2 +, are diamagnetic. In solution bis complexes are the most stable andexcess phosphine is necessary to incorporate more than 2 PMe, molecules in thecoordination sphere of Ni2+.7316 A similar situation exists in the supercages of thezeolites where an equilibrium is established between the surface complexes anduncoordinated PMe, :(Z0-),Ni2+ 3 (ZO-),Ni2+-PMe3 + [Ni(PMe,),l2+ + 3ZO-.(1)The reaction is driven to the right on NiY17 but stops at the pseudotetrahedralcomplex formation on NiX28. This is due to the larger Ni2+ content and thuslower PMe3:Ni2+ ratio in the supercages of NiX28. Other factors affecting thecoordination are the chemisorption of PMe, on surface oxygens and the differencein lattice negative charge density between X and Y.The diamagnetic trigonal bipyramidal complex [Ni(PMe,),] + is proposed onthe basis of the similarity of its spectrum with that of the same complex in solu-tion.I6 In the latter case the ' A ; + 'E'(e''4e'4 -+ e"4 e ', a;') transition is at19200cm-' with a band width of 5000cm-'.The symmetry forbidden and there-fore weak transition ' A ; -+ 'E" (e"4e'4+ ~ , " ~ e ' ~ a ' : ) is at 27800 cm-' and thea(PMe,)+ d(Ni) charge transfer band is around 38000 cm-'. We have ' A ; + ' E 'at 18300cm-' with a bandwidth of SOOOcm-' and o(PMe3)+d(Ni) at34250cm-'. The weak ' A ; + 'E" transition is not seen and is probably hidden bythe 26 500 cm- ' band of the pseudotetrahedral complex. We have eliminated[Ni(PMe,),] +, [Ni(PMe,),] + and [Ni(PMe,),] + as possibilities. Indeed, thefirst 2 cases have, in the homogeneous phase, approximate C2" symmetry andtherefore a system of 3 d-d absorption bands.[Ni(PMe3),I2+ is planar with a verybroad absorption (half band width = 10000 cm- ') encompassing 3 component^.^None of these features is seen in our spectrum.The change of environment from EPA solution (5 : 5 : 2 mixture of diethyl ether,isopentane and ethanol) to the zeolitic supercage slightly affects the ' A; + 'E' tran-sition (red shift of 900 cm-') but effects the L.M.C.T. much more, as evidenced bythe 3750crn-' red shift. This is a solution effect, the zeolite acting as a non-coordinating, anionic solvent. We now analyse the effect in terms of the opticalelectronegativity parameters.' The change in spin pairing energy, ASPE, in goingfrom d8 to d9 during the charge transfer transition is -4/3 D with D = 7B.Then,for the L.M.C.T. transition we have:PMe?(11) (1)vzt = v,, - ASPE = 30000 [xopt(Ni) - xopt(PMe3)] = 30000 AXnpt2526 Ni2+-PMe, COMPLEXES ON ZEOLITESFor B = 500 cm-', Axopt. = 1.3 and 1.4 in the supercages and in EPA solution,respectively. With jlopt(Ni) = 2.0-2.1 this gives xopt(PMe,) = 0.7-0.8 and 0.6-0.7,respectively. There is therefore a slight increase, of 0.1, in optical electronegativityof PMe, in the zeolite. This means more electron-attracting power or less basiccharacter. In other words one could speak of less a-donor capacity in the zeolite.This should also be reflected in the redox potential for these complexes. The effectis too small and hardly out of the experimental accuracy range to attempt ameasurement or a calculation.Note, however, that this red shift of L.M.C.T. bandsfor immobilized complexes appears to be a general phenomenon, as we have de-scribed a similar situation for Cu(en)$+(en = ethylenediammine) on the surface ofclay minerals.The spectrum of complex (IT) with one band in the range 5000-10000cm-1 ischaracteristic of a high spin complex. As all the complexes Ni(PMe3)xX2 withx = 2--5 are diamagneti~,~ the only possibility is that our spectrum is that of apseudotetrahedral complex with 1 PMe, and 3 lattice oxygens in the coordinationsphere of Ni2+. PMe, is a stronger ligand than the lattice oxygens. The complex isthen compressed tetrahedral with an idealized C3" symmetry. The general C3" casewas treated by Klier et al.I5 We have applied their general ligand field potential toour case with the following 2 assumptions: (i) the angle p, 0-Ni-P, equals 100";(ii) G;/G: = Gy/Gy = 10, where P and 0 refer to PMe, and lattice oxygens, re-spectively.G2 and G4 denote the radial integrals:-Ze2 4nR5 9 for point charges. 9G4 = 740 (r4)ion with Y40 = ~ -The ligand field energy diagrams with which we were able to fit the experimentalband maxima are shown in fig. 6. The following assignments are made:,E(,F) --+ ,E(,F), ,A,(,F): 8000-8800 cm-',E(,F) -+ 3 ~ , ( 3 ~ ) , ,A,(,F): 21 000-22000 cm-',E(,F) + ,E(,P): 26500 cm?Calculations of the ligand field and interelectronic repulsion parameters, based onthese assignments, give physically meaningful values which are summarized intable 2. Thus, PMe, is 2.1-2.3 times stronger a ligand than the lattice oxygens andthe orbital reduction factor is in the range 0.88-0.57.This indicates appreciabledeviation from the ionic bonding model but this is expected with a strong electron-rich ligand such as PMe, in the coordination sphere. The absorptions in the U.V.region cannot assist our interpretation. In the temperature range of the thermalstability of the complexes there is only one broad and unresolved band. Above381 K, the complexes are destroyed and the U.V. absorption must be ascribed tocharge transfer bands from the modified surface (modified by chemisorption) tobare Ni2 ions.Before adsorption of PMe, all the Ni2+ is in the small cavities, at least forNiY 17.' Adsorption of PMe, induces migration of Ni2 + to the supercages, until anew equilibrium is attained with complexed Ni2 + in the supercages and residual,uncomplexed Ni2+ in the small cavities.An upper limit to the number of[Ni(PMe3),l2 + complexes can be estimated from the intensity changes of the 800R . A . SCHOONHEYDT, D . VAN WOUWE AND H. LEEMAN 2527/FIG. 6.-Energy level diagram of &orbitals of Ni2+ in compressed tetrahedral configuration[(0J3NiPMe3I2+; right hand side G:/Gz = 2.1; left hand side G:/G? = 2.3.and 26500 cm-' bands of complex (11) upon evacuation (fig. 1). The assumptionsare (i) equal scattering coefficients for all the spectra of fig. 1; (ii) all the Ni2+ ofNiY17 is in the form of complex (11) after evacuation at 381 K. The fact that theband intensity of complex (11) was increased by the 381 K evacuation with respectTABLE 2.-RANGE OF RACAH'S PARAMETER B (Cm-') AND LIGAND FIELD PARAMETERS (Cm-l) FOR(O,),-Ni-PMe, ON Nix28 AND NiY17GSIIB 5.5-7.7 6-8B 872-590 918-653GSI 43604131 5508-5224GP, 10 028-950 1 11 567-1097010 m P e t 7428-7038 8568-812610 D&t 323G3 1 11 408G3872528 Ni2+-PMe3 COMPLEXES ON ZEOLITESto the room temperature evacuation favours this assumption ; (iii) [Ni(PMe,),12 + iscompletely converted to [(O,),-Ni-PMe,] + upon room temperature evacua-tion.The increase in the bands of the latter complex favours this assumption.We have after saturation with PMe, 0.9[Ni(PMe3),l2’ and 6 8 pseudotetrahed-ral complexes. In this way only 10.5-12.5 PMe, molecules are complexed to Ni2+,going up to 17 at 381 K.Most of the adsorbed PMe, is then available for chemi-sorption as shown by the desorption data in table 1. The same holds for Nix28 butnot all the Ni2+ can be transformed into the pseudotetrahedral complex even at381 K and an estimate of the number of complexes present in the supercages aftersaturation is not possible.CHEMISORPTION OF PMe,The low temperature desorption of PMe, covers the decomposition temperatureof the complexes and is therefore due to desorption of physisorbed and coordin-ated PMe,. The species remaining on the surface can be divided in 2 groups: (i)chemisorbed species absorbing at 1305-1345, 1422-1432 and 2910-3000 cm-(spectrum 4 of fig. 4). The latter spectrum is in very good agreement with that ofO=PMe, (1292-1305-1 340; 1420-1437; 2923-2999 cm- 1).20 Therefore it rep-resents strongly adsorbed O-PMe, molecules according to the reactionZ-0 + PMe,’-Z--O====PMe,. (2)Additional evidence for the formation of chemisorbed O=PMe3 comes from theaverage bond energies M-C and M-0 with M = Si, A1 and P.21-23 These aresummarized in table 3.It shows that P has a stronger affinity for 0 than Si and A1and that the Si-C and Al-C bonds are stronger than the P-C bonds. However,the fact that PMe, is found in the gas phase even after high temperature desorptionindicates that at least on some lattice oxygens reaction (2) is reversible. The pres-ence of the 1600-1660 cm- ’ band system is indicative of a strong chemisorptionprocess resulting in destruction of PMe, molecules. This band was not found in thegas phase spectra.Therefore, either the partial pressure of the components was toolow or these species react upon desorption. Note that the gas phase spectraobtained after desorption in the range 423483 K contain, besides the PMe, bands,the 1080, 1140 and 2885 cm-’ bands. We suggest that these bands are due to thephosphorester O=P(PCH3),. Indeed, 1080 and 1140cm-1 are in the range offrequencies for a P-0-CH3 vibration (101G1088 cm-’) and a H3C-0-Pvibration (1 168-1200 cm- ’), r e s p e c t i ~ e l y . ~ ~ ~ ~ ~ Secondly, its boiling point underatmospheric pressure is 470.4 K but is 358 K at 319.97. Pa.21 This range includesthe desorption temperature of our experiments. Therefore, in the presence of “reac-tive” oxygens, reaction (2) proceeds further:\ -.(3)Si ,“O====P(CH,), O=P(OCH,),/// A1 ’and eventually complete oxydation occurs to C02, H 2 0 and oxygenated P.The1600-1660 cm- band includes the deformation band of water, which can subse-quently be incorporated in PMe, following reaction (3). We have not detected C 0 2on the solid phase, but according to the mass spectra C 0 2 is desorbed at hightemperatures. It can result from a thermal decomposition of PMe, analogous tR . A . SCHOONHEYDT, D. VAN WOUWE A N D H. LEEMAN 2529TABLE 3.-AVERAGE BOND ENERGIES (kJ mol- ’) OF M-C AND M-O (M = P, si, Al)P-C in P(CH3)3 :263 P-0 : 397 P=0:585Si-C in Si(CH3)4: 301 Si-0 : 207AI-C in Al(CH,), : 255 A1-0 : 272NMe, or from a carbonate- or formate-like material, formed together with H 2 0and absorbing in the 160&1660 cm-’ range.26-29 The thermal decomposition ofthe phosphine molecules also accounts for the presence of H2, CH4, CO, ethylene,ethane, propane, n-pentane, acetone and propanol, all characterized by peaks inmass spectra in the ranges 26-30 and 3943.CONCLUSIONSThis report shows that zeolites are versatile supports for the synthesis of phos-phine complexes.Thus, we have synthesized [Ni(PMe,),] + and [Ni(0,),PMe3] + by simple gas phase adsorption of PMe, an dehydrated Nix28 and NiY17 zeolites.[Ni(PMe,),]’+ is only stable in excess PMe, and is converted to [Ni(Ol),PMe3]2fby room temperature evacuation of PMe,. [Ni(0,),PMe3I2+ is stable to evacua-tion up to ~ 3 8 1 K.It is a compressed tetrahedral, paramagnetic complex, whosespectral properties can be explained in C3v symmetry. A similar complex has notyet been found in solution chemistry. The spectrum of [Ni(PMe,),l2+ agrees withthat of a diamagnetic, trigonal bipyramidal complex. The fact that it is only formedin the supercages of zeolite Y shows that the PMe,:Ni ratio in the supercages iscritical. However, extensive chemisorption occurs which hampers the complexation.Additional experiments at low Ni-levels are necessary in order to separate theinfluence of the Ni-content and the chemisorption on the complexation of Ni byPMe, in the supercages.This work was sponsored partially by the Petroleum Research Foundation (PRFnr. 10706-AC5) and partially by the Belgian Government (Ministerie voor Wetens-chapsbeleid). R.A.S.acknowledges a grant as “Onderzoeksleider” of the “NationaalFonds voor Wetenschappelijk Onderzoek”. The authors thank Prof. J. B. Uytter-hoeven for his interest in this work.J. H. Lunsford, A.C.S. Symp. Series. 1977, 40, 473.Catalysis, Helerogeneous and Homogeneous, ed. B. Delmon and G. Jannes (Elsevier, Amsterdam,1975).Relations entre Catalysr Homogene et Catalyse HitirogGrze (Editions du CNRS, Paris, 1978).2 C . Naccache and Y. Ben Taarit, Acta Phys. et Chem. Szeged, 1978, 24, 23.’R. G . Herman. Inorq. Chim. Acta, 1979. 34. 119.6 R . A. Schoonheydt, D. Van Wouwe, M. Van Hove, E. F. Vansant and J. H. Lunsford, J.C.S. Chem.’A. Merle, M. Dartigucnave and Y.Dartiguenake, J . Mol. Swuct., 1972. 13. 413.8E. Garbowski, M. Primet and M.-V. Mathieu, Adv. Chem. Ser., 1977, 40, 281.‘E, D. Garbowski, M.-V. Mathieu and M. Primet, Chcm. Phys. Lt)tters, 1977, 49, 247.loY. Y. Huang, J . Catalysis, 1973, 30, 187.“1. E. Maxwell and E. Drent, J. Catalysis, 1976, 41, 412.”P. Peigneur, J. H. Lunsford, W. de Wilde and R. A. Schoonheydt, J. Phys. Chem., 1977, 81, 1179.13P. A. Jacobs, H. Nijs, J. Verdonck, E. G. Derouane, J.-P. Gilson and A. J. Sirnoens, J.C.S. Faraday I,l4 J. B. Uytterhoeven, Acta Phys. et Chem. Szeged, 1978, 24, 53.Comm., 1980, 33.1979, 75. 1 1962530 NiZf-PMe3 COMPLEXES ON ZEOLITES"K. Klier, P. J. Hutta and R. Kellerman, A.C.S. Symp. Ser. 1977, 40, 108.16J. W. Dawson, T.J. McLennan, W. Robinson, A. Merle, M. Dartiguenave, Y. Dartiguenave and H. B.Gray, J . Amer. Chem. SOC., 1974, 96, 4428.A. B. P. Lever, Inorganic Electronic Spectroscopy (Elsevier, Amsterdam, 1968). ' R. A. Schoonheydt, A. Maes, A. Cremers and J. B. Uytterhoeven, J . Phys. Chem., in press.19P. Gallezot and €3. Imelik, J . Phys. Chem., 1973, 77, 652.'OL. W. Daasch and D. C. Smith, J . Chem. Phys., 1951, 19, 22.21 Handbook of Physics and Chemistry, ed. R. C. Weast, (The Chemical Rubber Co., Cleveland, Ohio,22L. Maier, Progr. Inorg. Chem., 1963, 5, 27.23D. J. C. Jates, G. W. Dembinski, W. R. Kroll and J. J. Elliott, J . Phys. Chem., 1969, 73, 91 I.24L. C. Thomas and R. A. Chittenden, Spectrochim. Acta, 1964, 20,489.52nd edn, 1971).L. C. Thomas, The Identification of Functional Groups in Organophosphorus Compounds (AcademicPress, New York, 1974), chap. 3.26P. A. Jacobs and J. B. Uytterhoeven, J . Catalysis, 1972, 26, 175.27P. A. Jacobs, B. K. G. Theng and J. B. Uytterhoeven, J. Catalysis, 1972, 2, 191.'*P. A. Jacobs, F. H. Van Cauwelaert, E. F. Vansant and J. B. Uytterhoeven, J.C.S. Faraduy I, 1973, 69,29P. A. Jacobs, F. H. Van Cauwelaert and E. F. Vansant, J.C.S. Faraday I , 1973,69, 2130.1056.(PAPER 0/232