Synthesis of Platinum-Triruthenium Clusters Using the Zero-Valent Platinum Reagent Pt(nb)3: X-Ray Crystal Structures of Ru3Pt(CO)11(P-iPr3)2, Ru3Pt(μ-H)(μ3-η3-MeCCHCMe)(CO)9(P-iPr3),

Journal of Cluster Science, Vol. 12, No. 1, 2001

Synthesis of Platinum-Triruthenium Clusters Using theZero-Valent Platinum Reagent Pt(nb)3 :X-Ray Crystal Structures of Ru3Pt(CO)11(P-iPr3)2 ,Ru3Pt(+-H)(+3 -'3-MeCCHCMe)(CO)9(P-iPr3),Ru3Pt(+3 -'2-PhCCPh)(CO)10(P-iPr3),Ru3Pt(+-H)(+4 -N)(CO)10(P-iPr3) andRu3Pt(+-H)(+4 -'2-NO)(CO)10(P-iPr3)

David Ellis1 and Louis J. Farrugia2, 3

Received April 26, 2000

The complexes Pt(nb)3&n(P-iPr3)n (n=1, 2, nb=bicyclo[2.2.1]hept-2-ene),prepared in situ from Pt(nb)3 , are useful reagents for addition of Pt(P-iPr3)n

fragments to saturated triruthenium clusters. The complexes Ru3 Pt(CO)11(P-iPr3)2 (1), Ru3Pt(+-H)(+3 -'3-MeCCHCMe)(CO)9(P-iPr3) (2), Ru3 Pt(+3 -'2-PhCCPh)(CO)10(P-iPr3) (3), Ru3 Pt(+-H)(+4 -N)(CO)10(P-iPr3) (4) andRu3Pt(+-H)(+4-'2-NO)(CO)10(P-iPr3) (5) have been prepared in this fashion.All complexes have been characterized spectroscopically and by single crystalX-ray determinations. Clusters 1�3 all have 60 cluster valence electrons (CVE)but exhibit differing metal skeletal geometries. Cluster 1 exhibits a planar-rhom-boidal metal skeleton with 5 metal�metal bonds and with minor disorder in themetal atoms. Cluster 2 has a distorted tetrahedral metal arrangement, whilecluster 3 has a butterfly framework (butterfly angle=118.93(2)%). Clusters 4 and5 posseses 62 CVE and spiked triangular metal frameworks. Cluster 4 containsa +4 -nitrido ligand, while cluster 5 has a highly unusual +4 -'2-nitrosyl ligandwith a very long nitrosyl N�O distance of 1.366(5) A1 .

KEY WORDS: Mixed-metal; ruthenium; platinum; carbonyl cluster; allyl;alkyne; nitrido; +4 -'2-nitrosyl; X-ray structure.

243

1040-7278�01�0300-0243�19.50�0 � 2001 Plenum Publishing Corporation

1 Present address: Department of Chemistry, Heriot-Watt University, Edinburgh EH14 4AS,Scotland.

2 Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland.3 To whom correspondence should be addressed.

INTRODUCTION

Both homo- [1] and hetero-metallic [2] clusters containing platinum areof interest because of their variable skeletal structures and electron counts[3]. In certain cases the Pt atom can behave as a ``normal'' transitionmetal with a formal 18 electron count, while in other instances the Pt atomhas a formal 16 electron count. This can lead to apparently anomalousskeletal structures when related to the cluster valence electron count(CVE), and clusters with the same number of CVE may have differing coregeometries. It is difficult, if not impossible, to predict the skeletal core of aPt-containing cluster from the CVE count, unless it is known whether thePt atom is behaving as an 18 or 16 electron center. This is usually notknown a priori, but may be ascertained from the structure, since the 16electron count is usually associated with a planar coordination geometry atthe Pt center. Any ``prediction'' of the skeletal geometry is, in most cases,merely a post-rationalisation of the crystal structure.

The synthesis of mixed-metal clusters containing platinum has relied toa large extent on the use of zero-valent olefin precursors such as Pt(COD)2 ,Pt(PR3)(C2H4) and Pt(PR3)2(C2H4) [2, 4]. These are prepared in severalstages, often in only poor to moderate overall yields. We have previouslyreported [5] that the stable crystalline trisolefin complex Pt(nb)3 (nb=bicyclo[2.2.1]hept-2-ene), which is a precursor [6] in the preparation ofPt(COD)2 , is itself a useful reagent for the preparation of mixed-metalclusters. Treatment of Pt(nb)3 in situ with one or two moles of a phosphineleads to Pt(nb)3&n(PR3)n (n=1, 2) which are useful sources of the reactivefragments ``Pt(PR3)'' and ``Pt(PR3)2'' without the necessity of isolating thephosphine-olefin complexes. We herein report further examples of the useof these reagents in generating new Ru3Pt clusters, and the X-ray struc-tures of the resultant compounds. A preliminary report of this work hasappeared in a NATO ASI volume [7].

EXPERIMENTAL

The starting materials Pt(nb)3 (nb=bicyclo[2.2.1]hept-2-ene) [6],Ru3(+-H)(+3 -'3-MeCCHCMe)(CO)9 [8], Ru3(+3 -'2-PhCCPh)(CO)10 [9]and Ru3(+-H)(+-NO)(CO)10 [10] were prepared by literature methods.General experimental techniques were as previously described [5].

Preparation of Ru3 Pt(CO)11(P-iPr3)2 (1)

Pt(nb)3 (0.67 g, 1.4 mmol) was dissolved in 20 ml hexane and cooledto 0%C. A solution of P-iPr3 in hexane (2.9 mmol) was added and this

244 Ellis and Farrugia

mixture stirred for 5 min and then added to a cooled solution of Ru3

(CO)12 (0.897 g, 1.4 mmol) in 200 ml dichloromethane. The mixture wasstirred as it equilibrated to room temperature over 1 hour and the solutionturned an intense purple color. The solvent was removed under vacuumand the residue extracted with hexane, leaving a small amount of unreactedRu3(CO)12 . The extract was reduced in volume to 15 ml and chromato-graphed on a Florosil (100�200 mesh) column. Elution with hexane gaveunreacted Ru3(CO)12 , elution with 50 dichloromethane�hexane gave asmall quantity of Ru3(CO)11(P-iPr3) [t0.2 mmol, identified spectroscopi-cally 31P NMR (CDCl3) $ 51.9, IR (&(CO)�cm&1, CH2Cl2 solution) 2078 w,2026 vs, 2001 vs, 1972 s, 1792 s] as an orange band. The complex 1 was theneluted with 350 dichloromethane�hexane as a dark purple band. Cluster 1was recrystallised from dichloromethane�hexane mixture to give dark-purplevirtually black crystals (0.96 g, 0.85 mmol, 610 yield). Anal. Calcd forC29 H42O11 P2 Pt Ru3 ; C, 30.91; H, 3.76. Found: C, 31.03; H, 3.700. IR(&(CO)�cm&1, CH2Cl2 solution) 2078 w, 2026 s, 2002 vs, 1972 m, br, 1842m, br, 1792 m, br. 1H (CDCl3 , 298 K) $ 2.5�2.1 (overlapped multiplet, 6H,CH ), 1.3�1.1 (overlapped pair of dd, 36H, CH3). 31P (CDCl3 , 298 K) $62.5 (s, 1P, Ru�P), 89.1 (s, 1P, Pt�P, J(Pt�P)=4485 Hz).

An analogous reaction using PCy3 instead of P-iPr3 afforded blackcrystals of Ru3 Pt(CO)11(PCy3)2 in similar yields. IR (&(CO)�cm&1,CH2 Cl2 solution) 2076 vw, 2060 w, 2024 s, 2000 vs, 1970 m, br, 1840 m,br, 1790 m, br. 1H (CDCl3 , 298 K) $ 2.15�1.05 (m, 66H, C6 H11).

Preparation of Ru3 Pt(+-H)(+3 -'3-MeCCHCMe)(CO)9(P-iPr3) (2)

A similar reaction of Ru3(+-H)(+3 -'3-MeCCHCMe)(CO)9 (1.10 g,1.77 mmol) with Pt(nb)2(P-iPr3) (1.77 mmol) followed by chromatographicwork-up gave dark-green almost black crystals of Ru3Pt(+-H)(+3 -'3-MeCCHCMe)(CO)9(P-iPr3) (2) (0.88 g, 510 yield). Small quantities ofgreen and purple unidentified side products were also obtained. Anal.Calcd for C23H29O9PPt Ru3 ; C, 28.23; H, 2.99. Found: C, 28.35; H,2.930. IR (&(CO)�cm&1, hexane solution) 2074 w, 2056 m, 2022 s, 2006 m,1996 w, 1978 w, 1792 w. 1H (CDCl3 , 298 K) $ 6.17 (d, 1H, MeCCHCMe),2.80 (s, 6H, MeCCHCMe), 2.54 (m, 3H, CHMe2), 1.29 (dd, 18H, CHMe2),&20.08 (dd, 1H, Ru(+-H )Ru, J=1.72, 3.0 Hz). 31P (CDCl3 , 298 K) $ 90.4(s, 1P, Pt�P, J(Pt�P)=5581 Hz).

Preparation of Ru3Pt(+3 -'2-PhCCPh)(CO)10(P-iPr3) (3)

A similar reaction of Ru3(+3 -PhCCPh)(CO)10 (0.210 g, 0.28 mmol)with Pt(nb)2(P-iPr3) (0.28 mmol) followed by chromatographic work-up

245Synthesis of Platinum-Triruthenium Clusters

gave three bands. The first yellow-orange band was identified as thephosphine derivative of the starting cluster Ru3(+3 -'2-PhCCPh)(CO)10(P-iPr3) (300 yield), the second deep red band gave red-brown crystals ofRu3 Pt(+3 -'2-PhCCPh)(CO)10(P-iPr3) (3) (0.12 g, 400 yield) while a thirdminor red band was unidentified. Data for 3: Anal. Calcd for C33 H31O10

PPt Ru3 ; C, 35.49; H, 2.80. Found: C, 34.61; H, 2.960. IR (&(CO)�cm&1,hexane solution) 2068 s, 2030 vs 2024 vs, 2008 m, 1992 m, 1978 m, 1962m, 1846 w, 1802 w. 1H (CDCl3 , 298 K) $ 7.1 (m, 10H, C6 H5), 2.75 (m, 3H,CHMe2), 1.29 (dd, 18H, CHMe2). 31P (CDCl3 , 298 K) $ 71.3 (s, Pt�P,J(Pt�P)=4478 Hz).

The side-product Ru3(+3 -'2-PhCCPh)(CO)9(P-iPr3) was identifiedspectroscopically and by a single crystal X-ray determination. Anal. Calcd.for C32H31O9PRu3 ; C, 43.00; H, 3.50. Found: C, 43.98; H, 3.690. IR(&(CO)�cm&1, hexane solution) 2076 s, 2040 vs, 2018 vs, 2000 m, 1984 m,1948 vw, 1876 w. 1H (CDCl3 , 298 K) $ 6.9 (m, 10H, C6H5), 2.05 (m, 3H,CHMe2), 1.12 (dd, 18H, CHMe2). 31P (CDCl3 , 298 K) $ 49.8 (s, Ru�P).Crystal data: a=9.354(2), b=11.952(3), c=18.644(3) A1 , :=98.097(15),;=100.405(14), #=110.321(18)%, V=1875.1(7) A1 3, Z=2, triclinic, spacegroup P1, R(Rw)=0.0297(0.0787) for 2359 reflections with Fo>4_(Fo).Unidentified and partially occupied solvent molecules were present in thelattice, which is presumably the reason for the high carbon analysis.

Preparation of Ru3 Pt(+-H)(+4 -N)(CO)10(P-iPr3) (4) andRu3Pt(+-H)(+4 -'2-NO)(CO)10(P-iPr3) (5)

A similar reaction of Ru3(+-H)(+-NO)(CO)10 (0.45 g, 0.73 mmol) withPt(nb)2(P-iPr3) (0.75 mmol) followed by chromatographic work-up gavetwo isolable clusters in low yield. The first orange band gave cluster 4(0.104 g, 150 yield) as red-orange crystals and a second yellow band gavecluster 5 (0.086 g, 120 yield) as yellow-orange crystals.

Data for 4: Anal. Calcd for C19H22NO10PPtRu3 ; C, 23.93; H, 2.37;N, 1.47. Found: C, 24.69; H, 2.53; N, 1.300. IR (&(CO)�cm&1, hexanesolution) 2082 w, 2056 s, 2038 vs, 2018 s, 2006 m, 1990 m, br, 1966 w. 1H(CDCl3 , 298 K) $ 2.55 (septet, 3H, CHMe2), 1.33 (dd, 18H, CHMe2),&16.24 (s, 1H, Ru(+-H )Ru, J(Pt�H)=17 Hz). 31P (CDCl3 , 298 K) $ 55.2(s, Pt�P, J(Pt�P)=3106 Hz).

Data for 5: Anal. Calcd for C19H22NO10PPtRu3 ; C, 23.54; H, 2.29;N, 1.44. Found: C, 23.66; H, 2.37; N, 1.270. IR (&(CO)�cm&1, hexanesolution) 2088 w, 2064 s, 2044 vs, 2020 vs, 2012 sh, 1996 w, 1962 w, 1636w, br. 1H (CDCl3 , 298 K) $ 2.62 (septet, 3H, CHMe2), 1.32 (dd, 18H,CHMe2), &16.73 (s, 1H, Ru(+-H )Ru). 31P (CDCl3 , 298 K) $ 46.4 (s,Pt�P, J(Pt�P)=2796 Hz).


Crystallographic Procedures

Full details of data collection procedures and structure refinements forthe crystallographic studies are given in Table I. Each crystal was attachedto a glass fiber using acrylic resin, and mounted on goniometer head in ageneral position. Data were collected at ambient temperature (nominally291 K) in bisecting mode on an Enraf-Nonius TurboCAD4 diffractometer,running under CAD4-Express software, and using graphite monochromatedX-radiation (*=0.71073 A1 ). Precise unit cell dimensions were determinedby refinement of the setting angles of 25 high-angle reflections which wereflagged during data collection. Standard reflections were measured every2 h during data collection, and an interpolated correction was applied tothe reflection data where necessary. Lorentz-polarization corrections andan empirical absorption correction by the method of Stuart and Walker[11] were applied to all data sets. Structures were solved by ab initio directmethods using SHELXS-97 [12] and refined by full-matrix least-squareson F 2 (SHELXL-97 [12]) using all the unique data and the weightingscheme w=[_2(Fo)2+(AP)2+BP]&1 where P=[F 2

o �3+2F 2c �3]. Calcula-

tions were carried out using the WinGX package [13] of crystallographicprograms for MS-Windows. Thermal ellipsoid plots were obtained usingthe program ORTEP-3 for Windows [14].

RESULTS AND DISCUSSION

The reaction of Ru3(CO)12 with Pt(nb)2(P-iPr3), prepared in situ byreaction of Pt(nb)3 with one mole of phosphine, gave good yields of theintense purple cluster Ru3Pt(CO)11(P-iPr3)2 (1) as the only isolable Pt�Rucluster. Significant amounts of the phosphine substituted product Ru3

(CO)11(P-iPr3) were also obtained. Once the stoichiometry of 1 was estab-lished, it was found (unsurprisingly) that higher yields were obtained usingPt(nb)(P-iPr3)2 . Cluster 1 was characterized by spectroscopic means and asingle crystal X-ray structure. An ORTEP view is shown in Fig. 1. TheRu3 Pt metal skeleton adopts an essentially planar-rhomboidal geometrywith 5 metal�metal bonds, the torsion angle Pt1�Ru1�Ru3�Ru2 being&177.11(3)%. Cluster 1 has 60 cluster valence electrons (CVE) and mighttherefore be expected to adopt a tetrahedral geometry with 6 metal�metalbonds. The coordination geometry of the Pt center is planar and we maytherefore assume a 16 electron count. The observed geometry is thusconsistent with the CVE count, allowing for the anomalous behavior ofPt [2, 3b, 3c]. Each Ru�Pt edge bears a bridging carbonyl ligand. TheCO(1) ligand forms a virtually symmetrical bridge between the metals, asjudged by the M�C distances and the angles O1�C1�Ru1=139.9(6)% and



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Fig. 1. ORTEP drawing of the molecular structure and atomic labeling scheme forRu3Pt(CO)11(P-iPr3)2 , (1), with thermal ellipsoids drawn at the 300 probability level.Important metrical parameters: Pt1�Ru1=2.6889(7), Pt1�Ru3=2.7013(7), Ru1�Ru2=2.9021(9), Ru1�Ru3=2.9065(9), Ru2�Ru3=2.9074(9), Pt1�P1=2.2855(19), Pt1�C1=2.071(8), Pt1�C2=2.031(8), Ru1�C1=2.070(7), Ru3�C2=2.141(8), Ru2�P2=2.3832(19) A1 ,torsion angle Pt1�Ru1�Ru3�Ru2= &177.11(3)%.

O1�C1�Pt1=138.8(6)%, while the CO(2) ligand forms a slightly more asym-metric bridge, with O2�C2�Pt1=141.7(7)% and O2�C2�Ru3=137.6(7)%.

The geometry found in 1 is very similar to that previously observed byFarrar and coworkers [15] for the closely related cluster Os3Pt(CO)11

(PPh3)2 . In this latter species the bridging carbonyls are noticeably moreasymmetric than in 1. The three RuL4 sub-units in 1 are all slightly skewedabout their pseudo-C2 axes relative to the Ru3 plane, and hence display asmall D3 distortion, which is very commonly found in phosphine andphosphite substituted of M3(CO)12 (M=Ru, Os) [16]. At the end of thestructural analysis, a careful investigation of difference electron densitymaps revealed a set of three peaks of t1�2 e A1 &3. These peaks wereatomic in appearance, and could be satisfactorily refined as partiallyoccupied metal atoms. Our previous work [17] suggests that they are dueto a second, albeit quite minor orientation of the metal skeleton present ast20 of the major orientation. This is shown in Fig. 2. It is orthogonal tothe plane of the major orientation and one of the minor Ru atoms must lieclose to the major Pt atom Pt1 and was undetected. The observed metal�metal distances are consistent with this interpretation. In view of our pre-vious work [17] it is likely that this disorder is dynamic in origin, thoughwe have no evidence either way in this instance.

The reaction of Pt(nb)2(P-iPr3) with Ru3(+-H)(+3 -'3-MeCCHCMe)(CO)9 gave modest yields of the dark green cluster Ru3 Pt(+-H)(+3 -'3-MeCCHCMe)(CO)9(P-iPr3) (2), as well as two uncharacterized Ru�Ptclusters as minor products and small amounts of Ru3(+-H)(+3 -'3-



Fig. 2. ORTEP drawing of the disordered metal framework in (1). Important metricalparameters: Pt1a�Ru2a=2.72(4), Pt1a�Ru1a=2.72(4), Ru1�Ru2a=2.78(5), Pt1a�P2=2.24(8), Pt1�Ru2a=3.09(4), Pt1�Ru1a=2.61(4) A1 .

MeCCHCMe)(CO)8(P-iPr3). Cluster 2 has been characterized by spec-troscopic means and by a single crystal X-ray study. An ORTEP view of2 is shown in Fig. 3. The metal skeleton adopts a slightly irregulartetrahedral geometry. The coordination geometry of the Pt center is dis-tinctly non-planar and we may assume an 18 electron count at this atom.The CVE count for 2 is 60, which is the norm for a tetrahedral metal

Fig. 3. ORTEP drawing of the molecular structure and atomic labeling scheme for Ru3Pt(+-H)(+3-'3-MeCCHCMe)(CO)9(P-iPr3), (2), with thermal ellipsoids drawn at the 300 prob-ability level. Important metrical parameters: Pt�Ru1=2.7521(8), Pt�Ru2=2.7469(8),Pt�Ru3=2.9591(8), Ru1�Ru2=2.8992(10), Ru1�Ru3=2.8815(10), Ru2�Ru3=2.9059(10),Pt�P=2.271(2), Pt�C1=1.948(9), Ru1�C1=2.093(9), Ru1�C11=2.233(9), Ru1�C12=2.234(9), Ru1�C13=2.258(9), Ru2�C13=2.064(10), Ru3�C11=2.063(9) A1 .


skeleton. The position of the hydride ligand was determined from potentialenergy calculations [18] and is consistent with the 1H NMR spectrum,which shows no detectable 195Pt coupling for the hydride signal at $&20.08.

The Pt�Ru1 edge is bridged by a marginally asymmetric carbonylligand, as can be seen in the M�C distances and the angles O1�C1�Pt=135.7(8) and O1�C1�Ru1=138.5(7)%. If the orientation of this bridgingCO ligand is ignored, the molecule posseses an idealized mirror plane pass-ing through Pt, Ru1, P and C12; see Fig. 3. However the bridging carbonylgroup CO(1) destroys this idealized symmetry, since it lies well off thepseudo mirror-plane (distances from mean-plane are C1=1.048(9), O1=1.886(7) A1 ). This deviation from idealized mirror-symmetry is furtheramplified by the discrepancy between the Pt�Ru2 distance of 2.7469(8) A1compared with the Pt�Ru3 distance of 2.9591(8) A1 . There is no obviousrationalization for this structural irregularity, but an EXAFS study on 2[7] has shown that these distances are maintained in the instantaneousstructure in solution.

The reaction of Pt(nb)2(P-iPr3) with Ru3(+3 -'2-PhCCPh)(CO)10

affords modest yields (t400) of the mixed-metal cluster Ru3Pt(+3 -'2-PhCCPh)(CO)10(P-iPr3) (3) as well as significant quantities of the side-product Ru3(+3 -'2-PhCCPh)(CO)9(P-iPr3). Both complexes were identifiedby spectroscopic means and single crystal X-ray structures��see Experi-mental and deposited material for information on Ru3(+3 -'2-PhCCPh)(CO)9(P-iPr3). An ORTEP view of 3 is shown in Fig. 4. Cluster 3 is a 60CVE complex with a butterfly metal skeleton. The butterfly angle, definedby the torsion Pt1�Ru1�Ru2�Ru3 is &118.93(2)%. The ligand dispositionin 3 is somewhat asymmetric. Atom Ru1 bears three terminal CO groups,while Ru2 bears two such ligands. The two Pt�Ru bonding vectors arebridged by a CO ligand. Carbonyl CO(14) is more asymmetrically bridgedand more strongly bonded to the Pt center than CO(22), as seen in theassociated distances and angles O14�C14�Pt1=144.8(6), O14�C14�Ru1=134.8(6), O22�C22�Pt1=140.4(6) and O22�C22�Ru2=140.4(6)%. Thealkyne ligand is bonded to the three Ru atoms in the typical +3 -'2-& bondingmode found in numerous alkyne clusters [19], as well as in the precursorcluster [9]. The formal electron-deficiency at Ru2 is reflected in shorterbonding distances of this atom to Pt1, Ru3 and C1, compared with thosecorresponding distances for Ru1.

The reaction of Pt(nb)2(P-iPr3) with Ru3(+-H)(+-NO)(CO)10 affordedonly poor yields of two mixed-metal clusters Ru3Pt(+-H)(+4 -N)(CO)10(P-iPr3) (4) and Ru3Pt(+-H)(+4 -'2-NO)(CO)10(P-iPr3) (5). Both clusterswere characterized spectroscopically and by single crystal X-ray structures.ORTEP views of are shown in Figs. 5 and 6 respectively. They both



Fig. 4. ORTEP drawing of the molecular structure and atomic labeling scheme forRu3Pt(+3-'2-PhCCPh)(CO)10(P-iPr3)(3), with thermal ellipsoids drawn at the 300 prob-ability level. Important metrical parameters: Pt1�Ru1=2.7229(6), Pt1�Ru2=2.6963(6), Pt1�P1=2.2979(17), Pt1�C14=1.986(7), Pt1�C22=2.093(7), Ru1�Ru2=2.8223(7), Ru1�Ru3=2.8285(8), Ru2�Ru3=2.6946(8), Ru1�C14=2.220(7), Ru1�C2=2.197(6), Ru2�C22=2.135(7), Ru2�C1=2.072(6), Ru3�C1=2.264(6), Ru3�C2=2.172(6) A1 , torsion angle Pt1�Ru1�Ru2�Ru3= &118.93(2)%.

contain 62 CVE and both have the spiked triangular metal geometry [20]with the platinum atom as the ``spike.'' This geometry has been seen pre-viously in several Ru3Pt and Os3 Pt species [21]. Cluster 4 contains a +4 -nitrido ligand which is, within experimental error, equally bonded to thethree Ru atoms and has a slightly shorter bond to the Pt center. Due tothis bonding arrangement the Pt�Ru1 vector is ``pulled over'' towards theRu3 triangle, and makes an acute angle of 81.5% with the trirutheniumplane. Although transition-metal nitrido-clusters with a variety ofnuclearities have been known for some time [22], all the crystallographi-cally characterized examples of tetranuclear clusters with an M4(+4 -N)arrangement are from the Group 8 metals and all contain a butterfly metalarrangement. Complex 4 is, to our knowledge, the first example of anM4(+4-N) cluster which has a spiked-triangular metal skeleton. Thehydride ligand positions in 4 and 5 were obtained from potential energyminimisation calculations [18] and are consistent with the 1H NMR spectrain that no significant 195Pt coupling was observed for the hydride signals.

Cluster 5 contains a highly unusual +4-'2-nitrosyl ligand, and abroadly similar metal skeleton and ligand arangement to that found in 4.The nitrogen atom is bonded to the three Ru atoms slightly asymmetrically[Ru�N distances 1.991(4)�2.120(4) A1 ], while the Pt } } } N distance of2.598(3) A1 is too long to be considered bonding. The oxygen atom of thenitrosyl is also bonded to the Pt center [Pt�O11=1.992(3) A1 ]. Due to this



Fig. 5. ORTEP drawing of the molecular structure and atomic labeling scheme for Ru3Pt(+-H)(+4-N)(CO)10(P-iPr3)(4), with thermal ellipsoids drawn at the 300 probability level.Important metrical parameters: Pt�Ru1=2.7174(11), Ru1�Ru2=2.7293(11), Ru1�Ru3=2.7279(12), Ru2�Ru3=2.8210(12), Pt�P=2.298(2), Pt�N=1.939(7), Ru1�N=2.071(7),Ru2�N=2.004(7), Ru3�N=2.017(7) A1 .

bonding arrangement the Pt�Ru1 vector is forced away from the Ru3 tri-angle, and makes an obtuse angle of 99.0% with the triruthenium plane.A search of the Cambridge Structural Database reveals there is only oneother example of a crystallographically characterized cluster containing a+4 -'2-nitrosyl ligand, namely [Mo2Co2(+4-'2-NO)[t-BuP(C6H4)PBu-t](CO)6(C5 H5)2]+BF&

4 (6) reported some 10 years ago by Kyba et al. [23].This has a butterfly metal skeleton, with a nitrosyl N�O distance of1.27(7) A1 . In cluster 5 the corresponding N�O distance is 1.366(5) A1 , whichrepresents an even greater degree of N�O ``activation'' than observed in 6.A very broad IR band at 1636 cm&1 is tentatively assigned to the &(NO)stretch. In view of the N�O bond ``activation'' seen in 5, it is tempting tosuggest that 5 is an intermediate in the formation of the nitrido cluster 4.However we have no evidence that this is the case; solutions of 5 are quitestable under nitrogen atmosphere and show no NMR signals from 4, evenon standing for several days.

CONCLUSIONS

The complexes Pt(nb)3&n(P-iPr3)n (n=1, 2, nb=bicyclo[2.2.1]hept-2-ene), prepared in situ from Pt(nb)3 are effective synthons for the preparation,



Fig. 6. ORTEP drawing of the molecular structure and atomic labeling scheme for Ru3Pt(+-H)(+4-NO)(CO)10(P-iPr3) (5), with thermal ellipsoids drawn at the 300 probability level.Important metrical parameters: Pt�Ru1=2.7109(5), Ru1�Ru2=2.7239(6), Ru1�Ru3=2.7267(7), Pt�P=2.3188(14), Pt�O11=1.992(3), Pt } } } N=2.598(3), Ru1�N=2.120(4),Ru2�N=1.991(4), Ru3�N=1.995(4), N�O11=1.366(5) A1 .

in variable yields, of triruthenium-platinum clusters. A significant side reac-tion is the formation of phosphine substituted triruthenium precursors. Theresultant mixed-metal clusters display differing metal skeletal geometrieseven when possessing the same cluster valence electron count. There seemsno obvious reason for this, other than the well established [2, 3] propen-sity for platinum containing clusters to display such behavior. This workprovides a further illustration of the subtle factors involved in determiningthe metal-skeletal geometry of platinum-containing clusters.

SUPPLEMENTARY MATERIALS AVAILABLE

Crystallographic data for the structural analyses have been depositedwith the Cambridge Crystallographic Data Center, CCDC Nos. 143769,143770, 143771, 143772, 143773, and 143774 for compounds 1�5 andRu3(+3 -'2-PhCCPh)(CO)9(P-iPr3) respectively. Copies of this informationmay be obtained free of charge from the Director, CCDC, 12 Union Road,Cambridge CB2 1EZ, UK [Fax. (int code) +44 (1223)336-033 or e-mail:deposit�ccdc.cam.ac.uk or www: http:��www.ccdc.cam.ac.uk]. Tables ofobserved and calculated structure factors, complete listings of bond lengths


and bond angles, and anisotropic thermal parameters for the structuralanalyses are also available from LJF on request.

ACKNOWLEDGMENTS

The EPSRC is thanked for a grant towards the purchase of a CAD4diffractometer and Oxford Cryostream system and for grant GR�H 30809for a PDRA position (D.E.).

REFERENCES

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Documents

Synthesis of Platinum-Triruthenium Clusters Using the Zero-Valent Platinum Reagent Pt(nb)3: X-Ray Crystal Structures of Ru3Pt(CO)11(P-iPr3)2, Ru3Pt(μ-H)(μ3-η3-MeCCHCMe)(CO)9(P-iPr3),