J. CHEM. SOC. DALTON TRANS. 1990 Halogenation Reactions of Electron-rich Diphosphazane Ligand-bridged Derivatives of Dicobalt Octacarbonyl Crystal Structures of [Co,(p-I)- (p-C0)(C0)2{p-( MeO),PN( Et)P(OMe),},] BPh and [Co( CO),{P( OMe),},- {(MeO),PN( Et)P(OMe),-xP}]BPh,t Neil J. Bailey John S. Field," Raymond J. Haines and Lesley A. Rix Unit of Metal Cluster Chemistry Department of Chemistry University of Natal P. 0. Box 375 Pietermaritzburg 3200 South Africa (R = M e or Pr') by I, Br, or freshly distilled CCI affords the cations [Co2(p-X)(p-CO)(CO),{p-(RO),PN(Et)P(OR),},]+ (X = I Br or CI Halogenation of [Co,( CO),{p- (RO),PN (Et) P(OR),},] {p-(MeO),PN(Et)P(OMe),}{~-(MeO),PN(Et)P(O)(OMe)}]. respectively). A single-crystal X-ray diffraction study on [Co,(p-I) (p-CO) (CO),{p- (MeO),PN( Et) P(OMe),},] BPh confirms that these cations have A-frame structures with a neutral ligand CO occupying a bridging site additional to the bridging halogen atom.For R = M e (only) the cations slowly undergo a Michaelis-Arbusov type rearrangement initiated by attack of halide ions at a co-ordinated phosphorus atom to give the neutral complexes [Co,(p-X)(p-CO) (CO),- The latter could not be isolated but [Co,(p-I)(p-CO)(CO),{p-( Pr'O),PN(Et) P(OPr'),}{p-(Pr'O),PN( Et)P(O)(OPr'))] is readily isolated from the reaction of [Co,(p-I) (p-CO) ( CO),{p- (Pr'O),PN (Et) P(0Pri),},] + with hydride ions. When undistilled (Analar grade) rather than freshly distilled CCI is used t o chlorinate [CO,(CO),- Et complexes [M2(p-CO)(CO)p{p-(RO)2PN(Et)P(OR)2}2] (M = {p-(MeO),PN(Et)P(OMe),},] an unexpected product viz.[Co(CO),{P(OMe),},{(MeO),- PN( Et) P(OM~),-KP}] + is formed; this cation contains one cobalt atom bonded to two trimethyl phosphite ligands two carbonyl ligands and a pendant diphosphazane ligand as confirmed Et X-ray crystal log rap h ical ly. We are making extensive use of diphosphazane ligands of the type R2PN(Et)PR2 (R = aryl alkyl aryloxy or alkoxy group) to bridge two metal atoms in dinuclear or polynuclear com- plexes thereby stabilizing them to fragmentation to mono- nuclear species. For example an extensive chemistry of the Fe or Ru R = Me or Pr')' has been developed in which the two metal atoms are held in close proximity to each other by the bridging ligands during a reaction.Another consequence of this approach is that the presence of a bridging bidentate donor ligand leads to an increase in the electron density at the metal atom centres with the result that complexes containing these ligands are electron-rich. For this reason the [M,(p-C0)- (CO)4{p-(RO),PN(Et)P(OR)2)2] (R = Me or Pr') complexes are susceptible to attack by a wide range of electrophilic reagents especially protons and halogens leading to a host of new products some with fascinating structures and others with potential as multicentred catalysts.2 Of relevance here is our use of diphosphazane ligands to synthesize tetrasubstituted derivatives of [co2(co)8] viz. [Co,(CO),{ p-(RO)2PN(Et)P(OR),),1 (1; R = Me or Pr') in which the two cobalt atoms are bridged by two diphosphazane ligands.The bridging ligands are expected to hold the two cobalt atoms in close proximity to each other during a reaction in contrast to [co2(co)8] itself where for example substitu- tion of CO by Group 15 donor ligands frequently leads to fragmentation and formation of mononuclear p r o d ~ c t s . ~ More- over complexes (1) are electron-rich and as such are expected to be very susceptible to attack by electrophilic reagents. Thus the original aim of this work was to develop the chemistry of complexes (1) and in particular to attempt the synthesis of dicobalt dihydrido complexes of the type [CO,H,(CO)~{~- phen ylborate. (RO),PN(Et)P(OR),),] as well as the disubstituted derivatives [Co,H,(CO),{p-(RO),PN(Et)P(OR)2)]; the latter could be 266 1 l+ regarded as dinuclear analogues of the mononuclear commerci- ally useful hydroformylation catalyst [COH(CO>,(PBU,)].~ Our approach to the conversion of complexes (1) into dihydrido species has been two-fold.One has been to treat them with protons the result being the formation of complexes of the type rCo,(p-H)(CO),{ C1-(Ro),PN(Et)P(oR>2),1+ (R = Me or Pri); unfortunately subsequent addition of hydride ions merely served to deprotonate the cation rather than to result in the formation of the desired dihydrido complex.6 The other approach is represented here; complexes (1) are treated with halogenating agents with the aim of synthesizing compounds which can be used as precursors for the synthesis of dicobalt dihydrido complexes.t ~-Carbonyl-~-iodo-bis(~-1,1,3,3-tetramethoxydiphosphazane- 1 KP' 2~P~)-bis(dicarbonylcobalt) (Co-Co) and dicarbonyl( 1 I ,3,3- tetramethoxydiphosphazane-KP)bis(trimethyl ph0sphite)cobalt tetra- Supplementary data available see Instructions for Authors J. Chem. SOC. Dalton Trans. 1990 Issue 1 pp. xix-xxii. Analysis" (%) N C Complex H 2.1 (2.3) 2.2 (2.1) 3.3 (3.2) 5.2 (4.9) 6.6 (6.5) 4.2 (3.8) 42.1 (42.3) 49.4 (49.6) 20.3 (20.3) 1.9 (2.1) 2.9 (2.9) 2.4 (2.3) 6.9 (6.8) 5.4 (5.6) 7.2 (6.9) 51.7 (51.5) 48.2 (48.5) 53.7 (53.3) 2662 Table 1. Characterization data for the new complexes cc0,(p-I)(cl-c0)(c0)~{ p-(MeO),PN(Et)P- (OMe),) 2lBPh4 [Co,(p-I)(p-CO)(CO) { p-( Pr'O) PN( Et)P- (OPr')z)zlBPh4 [Co,(p-Br)(p-CO)(CO),{ p-(MeO),PN(Et)P- (OMe)z)zIPF [Co,(p-Br)(p-CO)(CO) (p-( Pr'O),PN(Et)P- (opr')z} zIBPh4 [Co ,(p-Cl)(p-CO)(CO) { p-( MeO) PN( Et)P- (OMe)z} 2lBPh4 [Co,(p-Cl)(p-CO)(CO),{ p-(Pr'O),PN(Et)P- (OPr')z)zlBPh4 l!c0(c0)2 CP(OMe)3 >Z ((Me0)2 PN(Et)P- (OM~),-KP)]BP~ 6.3 (6.1) 50.4 (50.1) 1.8 (1.5) 2.7 (2.9) (6.1) (34.7) hexafluorophosphate followed by crystallization of the pre- cipitate which separated from the toluene solution from dichloromethane-light petroleum.Analytical and spectroscopic data (Table 1) characterize the compounds as [Co,(p-X)(p-C0)- J. CHEM. SOC. DALTON TRANS. 1990 1.r. data,b v(CO)/cm-' 31P-{1 H} N.m.r.data G/p.p.m. 1995w(sh) 1980s 1845s 145.06(s) 1 985w(sh) 1 965s 1 850s 135.45(s) 1995w(sh) 1982s 1 850s 144.75(s) 1982w(sh) 1957s 1850s 135.92(s) 1 998w(sh) 1982s 1 855s 144.83(s) 1 980w(sh) 1 965s 1 857s 136.16(s) 103.97(s) 141.88(s) 143.97(s) 102.2 147Xd9' 1967s 1 940s 1 827s (CO)2{p(RO)2PN(Et)P(OR)2}2]Z (2; X = Br OT I R = Me or Pr' Z = BPh4 or PF,) formulations which were confirmed by a complete X-ray crystal-structure determination on [Co2(p-I)- [ C O ~ ( ~ - I ) ( ~ - C O ) ( C ~ ) ~ { ~ - ( P ~ ' ~ ) P N ( E ~ ) P ( O P ~ ~ ) ~ } 34.5 6.1 { p-(Pr'O),PN(Et)P(O)(OPr'))l a Calculated values in parentheses. Measured in dichloromethane. ' Measured in CDCI at 22 "C relative to external H,PO,. At -90 "C. ' Centres of complex multiplets.i C(14) Figure 1. Perspective view of [Co,(p-I)(p-CO)(CO),( p-(MeO),PN(Et)- P(OMe),},]+ showing the atom labelling scheme. There are two cations in the asymmetric unit labelled A and B (p-CO)(CO),{p-(MeO)2PN(Et)P(OMe)2}2]BPh4 (see below). Bromination of complexes (1) could also be achieved using carbon tetrabromide as the halogenating agent. Indeed chlorination of complexes (1) was best achieved by using excess carbon tetrachloride as the halogenating agent; the reaction was carried out in toluene in the presence of sodium tetraphenylborate and the precipitate which separated from the toluene solution was crystallized from dichloromethane-light petroleum to give orange crystals of [Co,(p-Cl)(p-CO)(CO),- {p-(RO)2PN(Et)P(OR)2}2]BPh (R = Me or Pri).Table 1 gives the characterizing analytical and spectroscopic data. It should be noted that unlessfreshly distilled carbon tetrachloride is used the reaction takes a different route (see below). Halo- genation of complexes (1) therefore parallels the iodination of the stoicheiometrically equivalent,' but structurally differ- ent,* [Co2(C0),{p-Ph2PCH2PPh2)23 complex; in the latter reaction the cation [Co,(p-I)(p-CO)(CO),{ p-Ph,PCH,- PPh,},]' is formed; thus in all these halogenation reactions formally a 'halogenonium ion' adds across the metal-metal bond with loss of carbon monoxide and formation of a bridging carbonyl group. The band patterns in the v(C0) region of the i.r. spectra of cations (2) (Table 1) are very similar to those reported for CRh2(~-X>(CI-Co)(Co)2{~-(R0)2pN(Et)P(OR)2} 21 + (X = CL Br or I; R = Me or Ph),' [Co2(p-I)(p-CO)(CO),(p-Me,- Results and Discussion Halogenation of [CO~(CO),(~-(RO)~PN(E~)P(OR),),I (1) in toluene using 1 equivalent of iodine or bromine resulted in the formation of a new compound as evidenced by the appearance of new peaks in the v(C0) region of the i.r.spectrum of the reaction mixture; in particular a strong band in the bridging carbonyl region appeared. The product was best obtained as an orange crystalline material by carrying out the reaction in the presence of either sodium tetraphenylborate or ammonium * Distances and angles given in the text are averaged over both crystallographically independent but structurally equivalent molecules in the asymmetric unit.PCH2PMe,)(p-Ph,PCH,PPh2)]+,'o [Rh2(P-Cl)(CL-CO)- (C0)2{p-Ph2PCH2PPh2}2] +,11 and [Ir2(p-C1)(p-CO)(CO)2- {p-Ph2PCH2PPh2}2]+.12 X-Ray analyses of the last three complexes showed that they have A-frame structures with a neutral ligand CO occupying a bridging site in addition to the halogen Cations (2) are expected to have similar structures but in order to establish this unambiguously a single- crystal X-ray diffraction study was carried out on [Co,(p-I)(p- CO)(CO) { p-(MeO) PN(Et)P(OMe),} ,] BPh,. Figure 1 gives a perspective view of the cation while Table 2 summarizes the important interatomic distances and angles.* The cation does 2 030s 1 985s J. CHEM. SOC. DALTON TRANS. 1990 Table 2. Selected interatomic distances (A) and angles (") for [Co,(~-1)(~-C0)(C0),{~-(Me0),PN(Et)P(0Me),~~]BPh~ I(1A)-Co(1A) Co( IA)-Co(2A) Co( lA)-P(4A) Co(lAw(3A) Co(2A)-P(3A) Co(2A)-C(3A) 2.6 lO(2) 2.503(2) 2.1 73(5) 1.93( 1) 2.177(5) 1.93(1) P ( l A ) - - * P(2A) 2.837(7) Co( 1 A)-I( 1 A)-Co(2A) I(1A)-Co(1A)-P(1A) I(1A)-Co( 1A)-C( 1A) Co(2A)-Co( 1 A)-P( 1 A) Co(2A)-Co( lA)-C(lA) P( 1 A)-Co( 1A)-P(4A) 57.1(1) 88.4( 1) 136.3(5) 95.2( I) 162.0( 5) 167.9(2) 97.3(5) 94.4(5) 6 1.2( 1) 91.6( 1) 110.7(4) 94.2(1) P( 1 A)-Co( 1 A)-C(3A) P(4A)-Co( 1A)-C(3A) I(IA)-Co(2A jCo(1A) I( lA)-Co(2AtP(3A) I( lA)-Co(2A)-C(3A) Co( 1 A)-Co(2A)-P(3A) Co( lA)-Co(2A)-C(3A) P(2A)-Co(2A)-C(2A) P( 3A)-Co(2A)-C(2A) 49.5(4) 87.4(6) 85.2(6) C( 2A)-Co(2A)-C( 3A) 1 18.0(6) indeed have the expected A-frame structure; in fact the symmetry of the cation approximates closely to C,h.The average Co-Co-C(0) angle of 164.4O reflects a slightly more linear arrangement along the metal-metal bond than in [Rh,- I( 1A)-Co(2A) Co( 1 A)-P( 1 A) Co( 1 A)-C( 1 A) Co(2A)-P(2A) Co( 2A)-C(2A) 2.623(2) 2.174( 5 ) 1.72(2) 2.174( 5 ) 1.77(1) P(3A) P(4A) 2.8 50( 7) I( 1 A)-Co( 1 A)-Co(2A) I( 1 A)-Co( 1A)-P(4A) I( 1A)-Co( 1A)-C(3A) Co(2A)-Co( 1 A)-P(4A) Co(2A)-Co( 1 A)-C(3A) P( 1 A)-Co( 1 A)-€( 1 A) 6 t .7( 1) 90.5(1) 11 1.3(4) 94.9( 1) 49.6(4) 86.8(7) P(4A)-Co( 1 A)-C( 1 A) C( 1 A)-Co( 1 A)<( 3A) I( lA)-Co(2A)-P(2A) 85.6(6) 112.5(6) 91.7(1) I( lA)-Co(2A)-C(2A) 131.3(5) Co( 1 A)-Co(2A)-P(2A) 9 3 3 1) Co( lA)-Co(2A)-C(2A) 167.5( 5 ) 172.3(2) P(2A)-Co(2A)-P(3A) P(2A)-Co(2A)-C(3A) P(3A)-Co(2A)-C(3A) CO( 1 A)-C(3A)-Co(2A) 92.6(5) 92.7(5) 80.9(5) 2.604( 2) 2.498(2) 2.179(4) 1.92(1) 2.18 l(5) 1.92( 1) P( 1 B) I( 1 B)-Co( 1 B) Co( 1 B)-Co(2B) Co( 1 B)-P(4B) Co(lB)-C(3B) Co(2B)-P(3B) Co(2B)-C(3A) P(2B) 2.862(7) Co( 1 B)-I( 1 B)-Co(2B) I( 1 B)-Co( 1 B)-P( 1B) I( 1 B)-Co( 1B)-C( 1B) 57.0( 1) 90.7( 1) 135.8(6) Co(2B)-Co( 1 B)-P( 1B) 95.4( 1) Co(2B)-Co( 1 B)-C( 1 B) 1 62.1(6) 167.3(2) P( 1 B)-Co( 1 B)-P(4B) P( 1 B)-Co( 1 B)-C(3B) P(4B)-Co( 1 B)-C(3B) I( 1 B)-Co(2B)-Co( 1 B) I( lB)-Co(2B)-P(3B) I( IB)-Co(2B)-C(3B) 94.8(5) 97.4(5) 61.0(1) 92.6(1) 110.3(4) 94.3( 1) 49.4(4) 8 5.3( 8) 86.7(8) Co( 1 B)-Co(2B)-P(3B) Co( lB)-Co(2B)-C(3B) P(2B)-Co(2B)-C(2B) P( 3 B)-Co( 2B)-C(2B) C(2B)-Co(2B)-C(3B) 116.8(8) observed; the band pattern in the v(C0) region remains similar but the peaks shift to lower wavenumbers e.g.after standing I( 1 B)-Co(2B) Co( lB)-P( 1 B) Co( 1 B w ( 1 B) Co(2B)-P(2B) Co(2B)-C(2B) P(3B) P(4B) I( 1 B)-Co( 1 B)-Co(2B) I( 1 B)-Co( 1 B)-P(4B) I( 1 B)-Co( 1 B)-C( 3B) Co(2B)-Co( 1B)-P(4B) Co(2B)-Co( 1 B)-C(3B) P( 1 B)-Co( 1 B)-C( 1 B) P(4B)-Co( 1 B)-C( 1 B) C( IB)-Co( 1 B)-C(3B) I( 1 B)-Co(2B)-P(2B) I( 1 B)-Co(2B)-C( 3B) Co( 1 B)-Co(2B)-P(2B) Co( 1 B)-Co(2B)-C(2B) B) P(2B)-Co(2B)-P(3 P(2B)-Co(2B)-C(3B) P( 3B)-Co( 2B)-C( 3B) Co( lB)-C(3B)-Co(2B) (p-CI)(p-CO)(C0)2{p-Ph2PCH2PPh2}2]+ and [Ir&-Cl)- solution affords new peaks at 1 970(sh) 1 950s and 1 815m cm-' measured in dichloromethane.On the basis that (p-CO)(CO) ( p-Ph PCH PPh } ,] + where the corresponding angles are 162.2(3) and 153.9(3)O respectively,"*12 but is or I) is attacked by halide ions forming [Fe,(p-X)(CO),{p- similar to the value of 166.4(3)O reported for the average Co-Co-C(0) angle in [CO,(~-I)(~-CO)(CO)~(~-M~,PCH,- propose that the cation has undergone a Michaelis-Arbusov PMe,)(p-Ph,PCH,PPh,)] + . l o Significantly the terminal car- type rearrangement reaction,' 7,1 involving attack of a halide bony1 groups bend away from the bridging iodine atom towards ion at a co-ordinated phosphorus atom with formation of the bridging carbonyl group.The Co(l)-C0(2) bond length of neutral complexes of the type [Co,(p-X)(p-CO)(CO),- 2.510(2) A is shorter than the values reported for cobalt metal l 3 (2.593 A) [co,(c0)8] l4 [2.524(2) A] [CO,(T~~-CSHS)- Despite several attempts including addition of excess of halide (P-PMe2)(CO),I the CCo,(C1-I)(~L-Co)(Co)2{~-(Me0)2pN(Et)P(OMe)2}21+ ions to facilitate the rearrangement reaction it was not possible to isolate the rearrangement product. It was possible however F o ~ ( ~ - H ) ( ~ - P P ~ ~ ) ( C O ) ~ ( ~ - P ~ P C H P P ~ ) ~ [2.637( 1) to isolate a Michaelis-Arbusov rearrangement product from the reaction of a stronger nucleophile uiz.H- with [Co,(p-I)- { p-(MeO),PN(Et)P(OMe),} (p-(MeO),PN(Et)P(O)(OMe)}]. (MeO),PN(Et)P(OMe),){p-(MeO),PN(Et)P(O)(OMe)}] we [2.593(2) A] [c02(~-I)(cl-c0)(c0)2(~- Me,PCH,PMe,)(p-Ph,PCH2PPh2)] + l o [2.555(2) A] and 1 but is consistent with a single bond; certainly electron counting predicts the presence of a single bond between the metal atoms. Interestingly the Co-Co distance is significantly shorter than the 'bite' of the bridging diphosphazane ligands (average P P distance 2.843 A); in fact this is to the best of our knowledge the shortest reported distance between two atoms bridged by diphosphazane ligands of the type R,PN(R')PR (R = alkyl aryl alkoxy or aryloxy group; R' = alkyl group). + The halogenation reactions of complexes (1) contrast their protonation reactions since in the latter CO loss does not occur; complexes (1) react with protons to form bridging - 90 "C.There are two sets of resonances one of ca. fifteen lines hydrido species of the type [CO,(~-H)(CO),{~-(RO)~PN(E~)- centred at 147.55 p.p.m. and the other of ca. eight lines centred at P(OR),},]+ (R = Me or Pri).6 Yet it is apparent that a tetracarbonyl complex is a likely intermediate in the halo- genation reactions and for this reason the iodination and bromination of complexes (1) were monitored at regular time intervals using i.r. spectroscopy. No evidence for the transient During the course of our studies on the chlorination of formation of a tetracarbonyl intermediate was obtained complexes (1) using carbon tetrachloride we observed that even in the presence of added carbon monoxide in fact the when undistilled (Analar grade BDH) rather than freshly reaction is complete after ca.2 min. Significantly if a soh- distilled carbon tetrachloride was used (under otherwise identi- tion of [Co,(p-X>(p-CO)(CO) { p-(RO)2PN(Et)P(OR)2} ,]X cal conditions) v(C0) peaks appeared in the i.r. spectrum of (X = C1 Br or I; R = Me only) in dichloromethane is left the reaction mixture which could not be attributed to the ex- to stand for 2-3 d a change in the i.r. spectrum is indeed pound [Co2(p-I)(p-CO)(CO)2(p-(Pri0)2PN(Et)P(OPri)2}{p- (Pr'O) PN(Et)P(O)( OPr')}] was separated and subsequently crystallized from light petroleum. Table 1 gives the characteriz- ing data especially significant being the P-{ 'H) n.m.r.data at 102.2 p.p.m.; both are complex multiplets the overall pattern being very similar to that for [Fe2(p-X)(C0),!p-(MeO),- PN(Et)P(OMe) ,} ( p-(MeO) PN(Et)P(O)(OMe)}] and t ypi- cal for an ABCX system. [Fe2(p-X)(CO)4(p-(Me0)2PN(Et)P(OMe)2}2] + (X = C1 Br (p-CO)(CO),(p-(Pr'O)2PN(Et)P(OPri)2}2]+. This reaction originally attempted with the aim of synthesizing a dihydrido complex was carried out in dichloromethane using NaBH as the hydride source; an i.r. spectrum of the reaction mixture showed mostly starting material but also new v(C0) peaks at lower wavenumbers. Using column chromatography the com- pected product i.e. [Co2(p-C1)(p-CO)(C0)2{p-(R0)2PN(Et)- 2663 2.630( 2) 2.171 (5) 1.72(2) 2.18 l(5) 1.74(2) 2.860(7) 62.0( 1 ) 87.9( 1) 1 1 1.4(4) 95.0( 1) 49.4(4) 86.7( 1) 85.6(7) 1 12.8(7) 9 0 3 I ) 110.3(4) 94.2( 1 ) 166.1(7) 171.4(2) 93.8(5) 92.5(5) 81.2(6) 2664 Figure 2.Perspective view of [Co(CO),{ P(OMe),},{(MeO),PN(Et)- p(oMe),-~P)] + showing the atom labelling scheme Table 3. Selected interatomic distances (A) and angles (") for [Co(CO),{ P(OMe),} { (MeOj2PN(Et)P(OMe),-~P)]BPh 2.186( 5) 1.68(3) 1.65(2) 2.166(6) 2.209(6) 1.75(2) co-P(2) co-C( 1) P( 3)-N N-C( 13) co-P( 1 ) CO-P(3) co-C(2) P(4)-N 1.53( 3) 1.72(2) 172.4(3) 94.0(2) 89.6(7) 88.3(10) 119.7(10) 124.9(13) 122.7(17) P( l)-Co-P(3) P( I)-Co-C(2) P(2)-Co-C( 1) P(3)-Co-C(1) C(l)-Co-C(2) P(3)-N-C(13) P( 1 )-Co-P(2) P( l)-Co-C( 1 j P(2)-Co-P(3) P(2)-Co-C(2) P(3)-Co-C(2) P(3)-N-P(4) P(4)-N-C(13) 85.0( 10) 92.4(2) 91.3(7) 1 15.3(7) 1 16.0( 11) 119.3(16) P(OR),},]Cl (R = Me or Pr').Typically these unexpected peaks were found at ca 2 030 and ca. 1 980 cm-' characteristic of some new compound which contained terminal carbonyl groups only. Unfortunately it was not possible to isolate this compound when dichloromethane was used as the solvent but it was possible to isolate yellow crystals from the reaction of [Co2(CO),{p-(MeO)2PN(Et)P(OMe)2}2] with Analar grade carbon tetrachloride in the presence of NaBPh when methanol was used as the solvent. The analytical and spectroscopic data in Table 1 are consistent with the compound being [Co(CO),- { P(OMe)3)2{(MeO)2PN(Et)P(OMe)2-~P}]BPh,; of note is the presence of three peaks in the 31P-{1H} n.m.r.spectrum indicative of three inequivalent phosphorus atoms in the compound. However a single-crystal X-ray diffraction study was necessary to establish fully the identity and structure of this compound. Figure 2 gives a perspective view of the cation while Table 3 summarizes some important distances and angles. The cation is indeed mononuclear the geometry at the cobalt atom being trigonal bipyramidal with the axial positions occupied by P(OMe) groups and the equatorial positions by two carbonyl groups and by a pendant diphosphazane ligand. Clearly some 'impurity' in the Analar grade carbon tetrachloride causes the chlorination reaction to proceed via a different route to that occurring when freshly distilled carbon tetrachloride is used.In particular cleavage of Co-Co Co-P and P-N bonds must J. CHEM. SOC. DALTON TRANS. 1990 occur to yield eventually a mononuclear complex with a pendant diphosphazane ligand two carbonyl ligands and two co-ordinated P(OMe),Cl groups the latter being rapidly solvolysed to give trimethyl phosphite ligands if methanol is used as solvent. No attempt has been made to ascertain the nature of the 'impurity' in the Analar grade carbon tetrachloride but it can be noted that on every occasion that the chlorination of complexes (1) was attempted with Analar grade carbon tetrachloride the unexpected mononuclear product was ob- tained.Experimental Although none of the compounds reported here is particularly air-sensitive all the manipulations (reactions chromatography and recrystallizations) described below were carried out under inert atmospheres of either dinitrogen or argon. Proton and 31P-{ 'H} n.m.r. data were obtained on a Varian FT80A instrument at 20 "C using deuteriated solvent as internal lock and reference ('H SiMe, 6 = 0; 31P 85% H3P04 in D,O 6 = 0 downfield positive). Infrared spectra were recorded on a Perkin-Elmer 457 grating spectrometer. Microanalysis for C H and N was performed in the Microanalytical laboratory of the Department of Chemistry University of Natal Pietermaritz- burg. The compounds [Co2(C0),{ p-(RO)2PN(Et)P(OR)2}2] (R = Me or Pr') were prepared as described previ~usly.~ Synthese~.-[Co,(p-X)(p-CO)(CO)~ (p-(RO),PN(Et)- P(OR),},]Z (X = Br or I R = Me or Pr' Z = ,BPh or PF,).An equimolar amount of NaBPh (NH,PF in the case of X = Br R = Me) dissolved in the minimum of methanol was added to a solution of [Co2(CO),{p-(RO)2PN(Et)P(OR)2}2J (0.200 g) in toluene (25 cm3). An equimolar amount of iodine (or bromine) dissolved in the minimum of toluene was added dropwise to the stirred solution over a period of ca. 10 min. The solution was stirred for a further 30 min during which time a precipitate separated. The solution was filtered and the precipitate crystallized from dichloromethane-light petroleum (b.p. 60-80°C) to give an orange crystalline solid. Typical yield 80%.cc02 (p-cl) (p:co) ( c o ) 2 { p-(RO) 2 PN(Et)P(OR) 2 } 2 1 BPh4 (R = Me or Pr'). Equimolar amounts (ca. 0.5 mmol) of carbon tetrachloride (freshly distilled) and NaBPh were dissolved in toluene (35 cm3) to which sufficient methanol had been added to ensure dissolution of the NaBPh,. The solution was stirred and [CO,(CO),{~-(RO)~PN(E~)P(OR),),I (0.30 mmol) dissolved in dichloromethane (10 cm3) was added dropwise over a period of ca. 10 min. The reaction mixture was stirred for a further 2-3 h by which time a green oil had precipitated. The solvent was removed in uacuo and the oily residue recrystallized from dichlorometbane-light petroleum (60-80 "C) to produce red- orange crystals of [Co (p-Cl)( p-CO)(CO) { p-(RO) PN( E t)- P(OR),},]BPh (R = Me or Pri).Yield 75%. [CO~(~-I>(~-CO)(CO)~ { ~ - ( P r ~ 0 ) ~ PN(Et)P(OPr'),} { p- (Pr'O),PN(Et)P(O)(OPr')}]. A solution of [Co,(p-I)(p-C0)- (CO),{ ~-(P~'O),PN(E~)P(OPI-')~}~]I (ca. 0.3 mmol) was pre- pared by addition of an equimolar amount of iodine to a stirred solution of [Co2(C0),{ p-(Pr'O),PN(Et)P(OPr'),) 2] (0.3 1 g 0.30 mmol) in methanol (25 cm3). The i.r. spectrum of the solution confirmed the clean formation of [Co,(p-I)(p-CO)- (CO)2{p-(PriO)2PN(Et)P(OPri)2}2] Cv(C0) see Table 13. A large excess of NaBH (ca. 0.5 g) was added and the solution stirred for ca. 1 h. The solution was filtered through Celite the solvent removed in uacuo and the residue extracted with toluene. The volume of the toluene extract was reduced and the concentrate subjected to column chromatography on alumina (Activity 111 15 x 2 cm column) using dichloromethane-light -+ J.CHEM. SOC. DALTON TRANS. 1990 Table 4. Atomic co-ordinates ( x lo4) for [CO,(~-I)(~-CO)(CO)~~~-(M~O)~PN(E~)P(OM~)~}~]BP~~ Xla 4 744( 1) 3 296(2) 4 810(2) 1842(3) 3 493(4) 6 309(4) 4 598(4) 1 375(13) 6 324( 1 1) 3 280(10) 1446(11) 486( 1 1) 3 978(23) 3 340( 17) 7 087( 19) 7 576(19) 4 960( 10) 4 148(10) 2 170(12) 5 997(10) 2 150(15) 5 752(14) 3 612(12) 1156(19) 279(21) 4 989(36) 2 874(22) 6 579(27) 8 001(28) 4 161(22) 3 794(17) 1 195(18) 1341(21) 6 951(19) 7 849(21) 3 568( 1) 5 692(2) 5 720(2) 5 414(4) 5 454(4) 5 949(3) 5 713(3) 6 438( 13) 6 293(14) 8 127(10) 4 lOl(12) 6 326(13) 6 415(12) 4 245(14) 5 187(9) 7 325(10) 4 593(9) 6 827(10) 5 369(12) 5 623(9) 6 168(16) 6 121(19) 7 058( 13) 3 520(19) 7 655(20) Atom C(6B) C(7B) C(8B) C(9B) C(1OB) C(11B) C(12B) C(13B) C(14B) C( 15B) B(A) C( 16A) C( 17A) C( 18A) C(19A) C(20A) C(21A) C(22A) C(23A) C(24A) C(25A) C(26A) C(27A) C(28A) C(29A) C(30A) C(31A) C(32A) C(33A) C(34A) C(35A) C(36A) C(37A) C(38A) C(39A) B(B) C( 16B) C( 17B) C( 18B) C(19B) C(20B) C(21B) C(22B) C(23B) C(24B) C(25B) C(26B) C(27B) C(28B) C(29B) C(30B) C(31B) C(32B) C(33B) C(34B) C(35B) C(36B) C(37B) C(38B) C(39B) Z l c 3 813(1) 4 736( 1) 4 978( 1) 4 571(2) 4 924(2) 5 052(2) 4 749(2) 4 902(6) 5 502(5) 6 037(5) 3 894(5) 4 951(5) 4 412(10) 5 437(9) 5 575( 10) 4 640(9) 4 147(5) 5 202( 5 ) 4 669(6) 4 918(5) 4 819(7) 5 318(7) 5 523(6) 3 587(9) 5 658( 10) 4 182(16) 6 094( 1 1) 6 179(14) 4 192(14) 3 749( 1 1) 5 866(8) 4 627(9) 3 922( 10) 4 976( 10) 4 450( 10) 768( 1) 1 142(1) 230( 1) 1837(2) 795(2) -452(2) 6W2) 2 115(6) - 809(7) 591(5) 2 294(6) 2 342(6) 641(6) 748(7) - 1 033(5) - 799( 5 ) 763(4) 649(5) 1571(6) - 159(4) 1715(8) - 389( 10) 643(7) 2 61 l(9) 2 176(10) Xla 7 716(25) 3 476(26) 3 969( 17) 8 019(20) 4 162(14) 8 128(17) 5 236(17) 3 855(23) 5 535(13) 4 151(15) 840( 15) 124(14) - 861( 18) -1 551(20) - 1 291(20) - 406( 17) 347( 15) 109(14) - 1 060(16) - 1 773(19) -1 321(19) - 21 7( 17) 488( 15) 2 365( 13) 3 002( 15) 4 298( 19) 4 951(20) 4 294( 19) 3 041(15) 906( 13) 1117(14) 1 244( 18) 1114(17) 91 3( 17) 78 1 (1 7) - 1 066( 16) -2 559(12) -2 871(13) - 4 099( 15) - 5 063( 19) -4 766(16) - 3 524(14) -828(14) - 1 577(16) -1 264(20) - 174(23) 634(21) 3 lO(20) - 168(13) 93 1( 18) 1701(21) 1398(22) 3 57(20) - 428( 16) - 845( 15) -900(17) - 794( 19) - 653(22) - 669( 19) - 764( 17) 679( 12) 265( 13) - 993(8) - 1 208(10) 1419(7) 534(8) Ylb 2 745(1) 3 238( 1) 2 155(1) 2 772(2) 1 540(2) 2 645(2) 3 877(2) 4 389(7) 9 16(6) 2 644(5) 2 961(6) 2 951(6) 1 043(12) 956(9) 2 399( 10) 2 474( 10) 4 380(6) 4 413(5) 1945(6) 3 468(6) 3 940(8) 1408(8) 2 673(7) 3 659(10) 2 828( 1 1) 707( 19) 1 083(12) 2 263( 14) 2 118(15) 4 728(12) 4 197(9) 1565(10) 1409(11) 3 896( 10) 3 998(11) 2 521(1) 1901(1) 2 844(1) 2 535(2) 3 619(2) 2 193(2) 1 136(2) 795(7) 3 883(8) 2 203(5) 2 592(6) 2 332(7) 4 121(7) 4 171(8) 2 466(5) 1977(5) 743(5) 5 0 4 w 3 341(7) 1430(5) 1234(9) 3 461(11) 2 275(7) 2 048( 10) 2 160(11) petroleum (b.p.60-80°C) as eluant. The first fraction con- tained the starting complex the second yielded an unidentifiable Sodium tetraphenylborate (0.10 g 0.30 mmol) was dissolved in pink oil while in U ~ C U O removal of the solvent from the third a mixture of methanol (25 cm3) and carbon tetrachloride (50 fraction gave a black residue; recrystallization of the latter from cm3). (Note The carbon tetrachloride was taken from a bottle light petroleum (b.p. 6&80 "C) afforded red crystals of [Co2- of BDH Analar grade and used without further purification.) (p-I)@-CO)(CO),( p-( Pr'O),PN(Et)P(OPr'),) (p-(Pri0)2PN- (Et)P(O)(OPr')}]. Yield 50 mg 15% based on [ C O ~ ( C O ) ~ ( ~ - mmol) was added and the solution stirred for 3 h. The solvent (PriO)2PN(Et)P(OPri)2) ,I.was removed in uacuo and the oily residue dissolved in [CO(CO),(P(OM~)~}~((M~O)~PN(E~)P(OM~)~-KP}]BP~~. Solid [CO,(CO),{~-(M~O),PN(E~)P(OM~)~}~] (0.20 g 0.30 2665 Z I C 2 014(8) 2 140(11) - 553(6) - 653(7) 2 490(8) 2 391(7) Ylb 3 861(14) 4 462( 14) 2 865(9) 2 434( 1 1) 44 1(7) 589(9) 3 833(9) 4 192(12) 947(7) 1019(8) 9 fw8) 9 @w8) 9 21 l(10) 8 736( 1 1) 8 091(11) 7 901(9) 8 361(8) 9 869(8) 10 328(9) 10 523( 10) 10 259( 10) 9 811(9) 9 633(8) 9 293(7) 8 751(8) 8 559(10) 8 864( 1 1) 9 464(10) 9 637(8) 10 21 l(7) 10 080(8) 10 610(10) 11 240(10) 11 401(10) 10 902( 10) 5 475(8) 5 810(7) 6 350(7) 6 664(8) 6 459( 10) 5 902(9) 5 W(8) 4 677(8) 4 257(9) 3 538(11) 3 243(12) 3 593(12) 4 331(11) 5 640(7) 5 887(9) 5 969( 12) 5 824( 12) 5 546( 1 1) 5 486(9) 5 868(8) 5 585(9) 5 966( 1 1) 6 612(13) 6 949( 10) 6 567(9) 2 003(9) 1 948( 10) 2 290( 10) 2 664( 8) 2 727(7) 3 117(7) 3 095(8) 3 647( 10) 4 218(9) 4 270(8) 3 687(7) 2 548(6) 2 260(7) 2 247(9) 2 548( 10) 2 802(9) 2 813(7) 1892(7) 1 262(7) 744(9) 807(8) 1410(9) 1 940(9) 2 026(8) 2 263(6) 2 579(6) 2 727(7) 2 530(9) 2 231(8) 2 081(7) 2 095(7) 2 510(8) 2 637( 10) 2 296( 11) 1 889(10) 1 790( 10) 2 468(7) 2 217(9) 2 637( 1 1) 3 238( 11) 3 526( 10) 3 127(8) 1316(8) 801(9) 167(10) 81(11) 557(10) 1 163(8) 2666 Table 5.Atomic co-ordinates ( x lo4) for [Co(CO),{ P(OMe),}2((MeO)2PN(Et)P(OMe),-~~}lBPh ZlC 4 232( 1) 4 513(2) 4 027(2) 3 798(2) 3 085(2) 5 003(9) 3 969(6) 4 315(7) 4 933( 1 1) 4 663(7) 4 345(5) 3 649(5) 3 977(5) Ylb 3 083(2) 4 477(5) 1 595(3) 3 614(3) 3 838(5) 2 503( 19) 3 134(14) 5 301(15) 4 337(25) 4 927( 16) 812(11) 1 349(11) 1350(10) 3 304( 1 1) 4 756(10) 2 874(14) 4 029(16) 3 399(13) 2 718(21) 3 120(16) 5 569(25) 4 215(32) 5 919(26) 677( 19) 3 10( 15) 388( 17) 3 277( 19) 5 371(23) 2 888(22) Xla 1756(2) 2 013(7) 1 547(4) 304(5) 1825(7) 854(22) 4 476( 19) 2 752(21) 2 647(39) 661(22) 1 877(17) 2 357(16) 76( 15) -1 125(15) 249( 15) 2 587( 19) 1343(21) 442( 18) 1272(29) 3 372(21) 3 188(37) 3 678(50) 39 1 (34) 3 201(30) 2 750(21) - 377(24) -1 784(27) - 525(33) 3 738(31) Xla 929(37) - 375(29) -1 527(34) - 1 602(21) - 926( 12) - 1 492(12) - 823( 12) 411(12) 976( 12) 308( 12) -851(13) -1 314(13) 3 844(5) 3 813(5) 2 993(6) 2 652(6) 3 313(6) 4 688(10) 4 069(7) 3 914(11) 5 004(13) 4 770( 1 1) 4 545(8) 3 508(7) 3 81 l(8) 4 233(9) 3 570( 10) 2 781(10) methanol.Cooling to -10°C resulted in the formation of (OM~),-KP)]BP~ over a period of 2-3 d. Yield 0.16 g 60%. yellow crystals of [Co(CO),{P(OMe),),((MeO),PN(Et)P- X- Ray Structural Analysis of [Co,(p-I)@-CO)(CO) { p- (MeO),PN(Et)P(OMe)2}2]BPh4.-Orange crystals were ob- tained by allowing light petroleum (40-60"C) vapour to diffuse slowly into a dichloromethane solution of the compound.Crystal data. C3,H,4BCo21N2011P4 A4 = 1 106.35 tri- clinic space group P1 a = 11.088(3) b = 20.701(5) c = 22.226(8) A a = 77.70(1) p = 79.69(1) y = 77.10(1)" U = 4812.3 A3 2 = 4 D = 1.527 g cm-, F(OO0) = 2 248 h = 0.71069 A p(Mo-K,) = 15.6 cm-' crystal size 0.35 x 0.27 x 0.46 mm. The crystal quality was poor as evidenced by broad ill defined reflection peaks but despite many attempts it was not possible to grow an improved crystal. Data collection. Unit-cell parameters and intensity data were obtained by previously detailed proced~res,~' using a CAD4 diffractometer operating in the -28 scan mode with graphite- monochromatized Mo-K radiation.A total of 17 162 reflec- tions were collected in the range 2 < 8 < 23"; of these 9 833 with I > 4o(I) were used in the solution and refinement of the structure. The reflection intensities were corrected for absorp- tion using the y-scan (empirical) method.,' No significant decay occurred during the data collection. Structure solution and rejinement. Direct methods (I and Co atoms) followed by Fourier-difference syntheses. Full-matrix least-squares refinement with I Co and P anisotropic 0 N scheme u' = 1.497/[02(F) + 0.006F2] gave satisfactory agree- C and B isotropic; H atoms not located.The weighting ment analyses. Final R and R' values are 0.090 and 0.103. Maximum shift/e.s.d. in last least-squares cycle = 0.204. Final Fourier difference map featureless with maximum peak height = 1.5 e A-3. All computations made with the programs SHELX 76 " and SHELX 86.22 Final atomic co-ordinates are listed in Table 4. J. CHEM. SOC. DALTON TRANS. 1990 Z l C 2 542( 12) 3 096(9) 2 944(11) 8 728(7) 9 145(4) 9 367(4) 9 690(4) 9 790(4) 9 568(4) 9 245(4) 8 356(5) 8 269(5) 8 028(5) 7 874(5) 7 961(5) 8 202(5) 8 704(4) 8 330(4) 8 301(4) 8 647(4) 9 021(4) 9 050(4) 6 327(4) 6 706(4) 6 746(4) 6 406(4) 6 027(4) 5 987(4) Ylb 5 002(28) 2 641(21) 3 043(26) 1 944(16) 2 342(11) 3 082(11) 3 484( 1 1) 3 145(11) 2 404(11) 2 003( 1 1) 2 574(10) 3 496( 10) 4 114(10) 3 81 l(10) 2 889(10) 2 271(10) 2 057(9) 2 129(9) 2 153(9) 2 104(9) 2 031(9) 2 008(9) 5 724(6) 5 306(6) 4 306(6) 3 724(6) 4 142(6) 5 142(6) - 585( 13) 607( 13) 1 070(13) 341 (1 3) -3 213(9) -3 807(9) - 5 159(9) - 5 917(9) - 5 323(9) -3 971(9) 1372(13) 1 400(13) 1356(13) 1 285(13) 1 256(13) 1 300(13) X-Ray Structural Analysis of [Co(CO),( P(OMe)3)2- {(MeO)2PN(Et)P(OMe)2-~P)1BPh4.-Yellow crystals were obtained by cooling a methanol solution of the compound to - 10 "C.Crystal data. C3,H,,BCoNOl2P, M = 91 1.06 ortho- rhombic space group P2,2,2, a = 10.291(2) b = 13.875(3) c = 33.415(8) A U = 4 770.9 A3 2 = 4 D = 1.268 g ~ m - ~ F(000) = 1912 h = 0.710 69 A p(Mo-K,) = 5.66 cm-' crystal size 0.46 x 0.58 x 0.89 mm.The crystal quality was poor as evidenced by broad ill defined reflection peaks but despite many attempts it was not possible to obtain a smaller better-defined crystal. were obtained by previously detailed procedures,' ' using a Data collection. Unit-cell parameters and intensity data CAD4 diffractometer operating in the 0-28 scan mode with graphite-monochromatized Mo-K radiation. A total of 3 927 reflections were collected in the range 2 < 8 < 23"; of these 2270 with I > 4 4 0 were used in the solution and refinement of the structure. The reflection intensities were corrected for absorption using the v-scan (empirical) method.,' No significant decay occurred during the data collec- tion.Structure solution and refinement. Patterson function (Co and P atoms) followed by Fourier-difference syntheses. Full-matrix least-squares refinement with Co and P anisotropic 0 N and C located. The weighting scheme w = l.000/[02(F) + 0.001F2] isotropic. Phenyl rings refined as rigid groups; H atoms not gave satisfactory agreement analyses. Final R and R' values are 0.1 1 1 and 0.1 17. Inversion of the atom co-ordinates followed by a complete refinement resulted in an insignificant increase in R'. Maximum shift/e.s.d. in last least-squares cycle = 0.1 1. Final Fourier difference map featureless with maximum peak All computations made with the programs height = 2.0 e SHELX 76 and SHELX 86.22 Final atomic co-ordinates are listed in Table 5.Additional material available from the Cambridge Crystal- J. CHEM. SOC. DALTON TRANS. 1990 lographic Data Centre comprises thermal parameters and remaining bond lengths and angles. Acknowledgements The authors express their sincere thanks to the Foundation for Research Development of the South African Council for Scientific and Industrial Research and the University of Natal for financial support and to Dr. P. van Rooyen of the National Chemical Research Laboratory Council for Scientific and Industrial Research Pretoria for the intensity data collection. L. A. R. also acknowledges the financial support of AECI Limited. References 1 G.de Leeuw J. S. Field R. J. Haines B. McCulloch E. Meintjies C. Monberg G. M. Olivier P. Ramdial C. N. Sampson B. Sigwarth ibid. 1986,310 C42. and N. D. Steen J. Organomet. Chem. 1984,275,99. 2 J. S. Field R. J. Haines and C. N. Sampson J. Chem. Soc. Dalton Trans. 1987 1933; J. S. Field R. J. Haines C. N. Sampson J. Sundermeyer and K. G. Moodley J. Organomet. Chem. 1987,322 C7; J. S. Field R. J. Haines C. N. Sampson and J. Sundermeyer 3 G. de Leeuw J. S. Field R. J. Haines and E. Minshall S. Afr. J. Chem. 1988,41,9. 4 D. J. Thornhill and A. R. Manning J. Chem. SOC. Dalton Trans. 1973,2086; M. Absi-Halabi J. D. Atwood N. P. Forbus and T. L. Brown J. Am. Chem. Soc. 1980,102,6248. 5 F. E. Paulik Catal. Rev. 1972,6,49. 2667 6 L. A. Rix M.Sc. Thesis University of Natal 1989. 7 D. J. Elliot D. G. Holah and A. N. Hughes Inorg. Chim. Acta 1988 142 195. 8 A. N. Hughes and V. R. Magnuson personal communication. 9 E. Meintjies M.Sc. Thesis University of Natal 1978. 10 E. C. Lisic and B. E. Hanson Organometallics 1987,6 512. 11 M. Cowie J. T. Mague and A. R. Sanger J. Am. Chem. SOC. 1978 100,3628. 12 J. T. Mague and A. R. Sanger Inorg. Chem. 1979,18,2060. 13 ‘International Tables for X-Ray Crystallography,’ Kynoch Press Birmingham 1962 table 4.3. 14 G. G. Sumner H. P. Klug and L. E. Alexander Acta Crystallogr. 1964,17,732. 15 E. Keller and H. Vahrenkamp Z. Naturforsch. Teil B 1978,33,537. 16 B. E. Hanson P. E. Fanwick and J. S. Mancini Inorg. Chem. 1982 Chem. 1987,40,1. 21 3811. 17 R. J. Haines and C. R. Nolte J. Organomet. Chem. 1970,24,725; R. J. Haines A. L. du Preez and I. L. Marais ibid. 1971,28,405. 18 T. B. Brill and S. J. Landon Chem. Rev. 1984,84,577. 19 J. L. M. Dillen 0. Meth-Cohn and P. H. van Rooyen S. Afr. J . 20 A. C. T. North D. C. Philips and F. S. Matthews Acta Crystalfogr. 21 G. M. Sheldrick SHELX 76 Program for Crystal Structure Determination University of Cambridge 1976. 22 G. M. Sheldrick SHELX 86 Program for Crystal Structure Sect. A 1968,24,351. Determination University of Gottingen 1986. Received 27th February 1990; Paper 0/00877J