摘要:

J. CHEM. soc. DALTON TRANS. 1986 517Eleven-vertex isocloso Type Rhodaundecaboranes: Crystal Structures andNuclear Magnetic Resonance Properties of [( PMe,Ph),RhHB,oH,(OMe)2]and [(PMe,Ph),RhHB,,H,CI(OMe)] *Hayat Fowkes, Norman N. Greenwood, John 0. Kennedy, and Mark Thornton-PettDepartment of Inorganic and Structural Chemistry, University of 1 eeds, 1 eeds LS2 9JTThe reaction between [RhCI,(PMe,Ph),] and cIoso-[B,,H,,]~- in refluxing MeOH gives [1,1-(PMe2Ph),-l,2-p-H-2,5-(OMe),-isocloso-l -RhB,,H,] as a bright yellow air-stable compound inlow yield. Crystals are triclinic, space group P i with a = 948.8(4), b = 1 675.5(6), c = 1 855.0(6)pm, a = 101.48(3),reaction is the yellow compound [1,1-( PMe,Ph),-1 ,2-p-H-2-CI-5-OMe-isoc/oso-l -RhB,,H,],crystals of which are orthorhombic, space group P2,2,2,, with a = 1 267.5(3), b = 1 269.9(3),c = 1 683.4(3) pm, and Z = 4.In each compound the RhB,, cluster is a closed eleven-vertexdeltahedron, the hexahapto borane-metal linkage being effected via one Rh-H-B and five Rh-Bconnectivities. The metal centre is an 18-electron ds rhodium(iti) atom which can be thought tocontribute four orbitals to the metallaborane cluster bonding scheme, thus inducing ‘isocloso’cluster character. The presence of a bridged metal-hydrogen-boron linkage on the closedpolyhedral cluster is also notable.= 99.55(3), y = 99.82(3)”, and Z = 4. An occasional by-product of theIt has previously been found that the reaction of the iridium(1)complex [Ir(CO)Cl(PPh,),] with the cfoso-[B,oHlo]2- anionin boiling methanol solution yields isomeric nido eleven-vertexcluster compounds of molecular formula [(CO)(PPh,),IrB,,-H, 1(PPh3)J,1 together with a variety of metallaborane andmetallacarborane degradation products which include six-vertex and ten-vertex species, and which include compoundswith either one or two metal centres.2-5 We now report that, bycontrast, the reaction of the rhodium(I1i) complex [RhCl,-(PMe,Ph),J under the same conditions gives the new eleven-vertex species [(PMe,Ph),RhHB,,H,(OMe),l (1) and[(PMe,Ph),RhHB, ,H,CI(OMe) J (2). These have beenc h a r a c t e d by single-crystal X-ray diffraction analysis andby n.m.r. spectroscopy, and each has an isocfoso type con-figuration and electronic structure similar to that recentlyreported for a number of ruthenium and osmiumThese eleven-vertex closed-cluster compounds pose interestingquestions for the development of cluster bonding theory 6 * 7 * 9and the two rhodium species reported here (which are also thefirst structurally characterized polyhedral rhodaboranes) throwadditional light on the nature of the metal-borane bondingwithin this configuration.Results and DiscussionThe reaction between equimolar quantities of [NEt,H],-[BloHloJ and [RhCI,(PMe,Ph),] in boiling methanol for20 min, followed by thin-layer chromatographic separation ofthe reaction products, gave an air-stable bright orange-yellowcrystalline compound, isocfoso-[(PMe,Ph),RhHBl0H8-(OMe),], as the predominant metallaborane product in anisolable yield of 5%.Erratic yields (which appear to dependcritically on the purity of the starting materials) of othermetallaboranes were also obtained and one of these was found* 1,l- Bis(dimet hylpheny1phosphine)- 1,2-p-hydrido-2,5-dimet hoxo-isocloso- 1 -rhodaundecaborane and 2-chloro- 1,l -bis(dimethylphenyl-phosphine)- 1,2-phydrido-5-me&hoxo-isocloso- 1 -rhodaundecaboranerespectively.Supplementary data available (No. SUP 56405, 3 pp.): thermal para-meters. See Instructions for Authors, J. Chem. Soc., Dalton Trans., 1986,Issue 1, pp. xvii-xx. Structure factors are available from the editorialOffice.+lo0 +80 + 60 “+20 0 - 206(” B)/p.p.m.Figure 1. Boron-1 1 n.m.r. spectra of [(PMe,Ph),RhHB,,H,(OMe)z]recorded at 1 1 5.5 MHz (CDCI, solution): (a) the normal spectrum, (6)with H broad-band noise decouplingto be the related compound isocloso-[(PMe,Ph),RhHB,,H,-Cl(0Me)J.The major product of the reaction was thenonaborane adduct B9H1 ,(PMe,Ph) and there was noevidence for significant quantities of any rhodaborane productsanalogous to the wide variety of iridium-containing speciesformed in the related reaction between [Ir(CO)Cl(PPh,),] andcloso-[BloHloJ2 - in methanol.’-’ Conversely, however, thesimilarities between the n.m.r. properties of the two closo typerhodaboranes reported here and the n.m.r. properties of some ofthe yet unidentified components of the iridium reaction indicatethat this latter may produce small amounts of iridaboranes withthe same closed eleven-vertex configuration.The high-field ‘‘B n.m.r.spectrum of [(PMe,Ph),RhHB,,-H8(OMe),] (Figure 1 and Table I), when compared to those ’of ruthenium species such as [ ( P M ~ , P ~ ) , R U B ~ ~ H , ( O M ~ ) ~ ] ,indicate an overall similar geometric and electronic clusterstructure, although with an idealized C, mirror plane ratherthan two-fold CZu symmetry. This is confirmed by the results ofsingle-crystal X-ray diffraction analysis: the unit cell was foundto contain two independent molecules in which the principaldifference, other than Rh-P and P-C bond rotation, was th518 J. CHEM. SOC. DALTON TRANS. 1986Table 1. N.m.r. parameters for [(PMe,Ph),RhHB,,H8(OMe)2] and for [(PM~,P~),RuB,,H,(OM~)~][(PMe,Ph),RhHB, ,H,(OMe),] a C(PMe,Ph),RuB10H8(OMe)~IbIA\AI -7Tentative "B relative "B relativeassignmentsc G("B)/p.p.m." intensity 6( 'H)/p.p.m.'*/ 6( ' ' B)/p.p.m.d.u intensity 6( ' H)/p.p.m.'*/+ 99.9 + 70.7 + 0.7+4.59 (OMe)" + 4.41 (OMe) '}+2.12+90.1+ 3.6+ 7.4+4.30 (OMe)+ 2.25+ 2.41+ 8.5 2 + 3.72(1) i - :;:} 2.69 '*' I11 (8,10)P-me t h yl n + 1.07 O.P + 1.26 O + q r + 1.15sCD,CI, solution at +22 "C.CDCl, solution at +21 "C; data from ref. 22. Numbering as in Figure 2. To low field (high frequency) ofBF,(OEt,). ' To low field (high frequency) of SiMe,. 6('H) related to corresponding directly bound 6(' 'B) by 'H-{' 'B(se1ective)) experiments.CJ "El 'B connectivities and thence assignments established and/or confirmed by 128-MHz ' 'B-' 'B COSY two-dimensional n.m.r.spectroscopy.Selective sharpening of B-methoxy protons in 'H-("B} experiments indicates small couplings 3J(1'B-O-C-'H) of < ca. 2 Hz. Selectivesharpening of 6('H) - 2.69 p.p.m. by irradiation at v(' ' B) corresponding to 6( ' B) + 70.7 p.p.m.; "J( ' ' S ' H ) of 55 f 15 Hz present, probably due to'J("B-'H) [Rh(l)-H-B(2) bridge] rather than 'J("B-Rh-'H)(transoid) (see text). J Vertex (1) occupied by Rh. ' Doublet ['J(103Rh-1H) ca. 14Hz] of triplets [2J(3'P-Rh-'H)(cis) ca. 13 Hz] in 'H-{ "B(broad band)} spectrum. ' Vertex (1) occupied by Ru. [AX,],-type spin systems, X = 'H,A = 31P; intensity distribution corresponds to 12J(31P-Rh-31P)(cis)l of a few tens of Hz; N = ('J + 4J)(3'P-'H) (seep, q, and s). " S(,'P) -5.2p.p.m. at -45 "C in CDCI,; 'J('03Rh-3'P) 108 Hz.Two chemically inequivalent P-methyl groups due to adjacent prochiral centre. N(3'P-'H) 9.7Hz. N(,'P-'H) 9.5 Hz. 6(3'P) -3.8 p.p.m. at - 50 "C in CDCI,. N(3'P-'H) ca. 8 Hz.Table 2. Interatomic distances (pm) for the two independent molecules of isocloso-[(PMe,Ph),RhHB,,H,(OMe),]( i ) To the rhodium atomMolecule A Molecule BRh( 1 )-P( 1) 2 3 5.5( 4) Rh( 1 )-P(2) 237.3(3) Rh( I'j-P( 1 ') 236.0(3) Rh( l')-P(2')Rh( 1 )-B(2) 222.0(8) Rh(lkB(5) 206.7( 9) Rh( l')-B(2') 222.1(7) Rh( l'jB(5')Rh( 1 kB(3) 230.4(7) Rh( 1 )-B(6) 228.4(9) Rh(1')-B(3') 2 3 0 3 7) Rh( l')-B@')Rh( 1 )-B(4) 230.0(8) Rh( 1 kB(7) 23 1.8(9) Rh( 1 ')-B(4') 229.4(9) B( 1 ')-B( 7')Rh(l)-H(1,2) 181(2) Rh(l')-H(l',2') 173(2)194.9( 1 I )177.4( 11)168.2( 11)175.1( 12)1 87.6( 10)173.q 12)182.q 13)177.7( 12)175.7(11)1 7 5 3 12)177.9( 12)19O.8( 10)181.q 12)172.0(11)178.0(9)175.9( 1 1)182.I( 13)176.9(10)182.2( 1 1)177.3( 12)1744 13)B(2')-B(3')B( 2')-B( 8')B(3')-B(4')B( 3')-B( 8 ')B( 3')-B( 9')B(4')-8(5')B( 4 )-B( 9')B(4')-B( 1 0 )B@'b-B(9')B(9')-B( 1 0 )B(9')-B( 1 1')185.q 12)178.8( 12)172.3( 1 I )I77.8( 1 1)175.8( 13)181.9(11)177.4(10)18 I. 1 (1 2)176.3( 12)176.q 1 1)175.8(12)B(2')-B(7')B( 5')-B( 1 0 )B(6')-B(7')B( 7')-B(8')B(7')-B( 1 1 ')B(5')-B(6')B( 6')-B( 1 1 ')B(6')-B( 1 0 )B(8')-B(11')B(lO)-B(lI')(iii) Boron-hydrogenB(2)-H( 1.2) 132(2) B(2')-H( 1',2') 144(2)B(3)-H(3) B(7W(7) 1 I7(2) B( 3')-H( 3') 120(2) B( 7')-H( 7')B(4FW4) 121(2) B(6)-H(6) 1 12(2) B(4')-H( 4') 108( 2) B( 6')-H( 6')B ( W w 119(2) B(10)-H(10) 113(2) B( 8')-H( 8') I lO(2) B( 10)-H( 10')B( 1 1 ')-H( 1 1') B(9)-H(9) 102(1) B(11)-H(11) 110(3) B( 9')- H (9') 96(2)(iv) OthersB(2)-0(2) 137.2( 8) B(5)-0(5) 134.2(9) B( 2')-O( 2') 137.1(9) B( 5')-O( 5')0(2)-c(2) 138.3(8) O( 5 )-c( 5 1 135.7(12) 0(2')-c(2') 140.7(8) 0 ( 5 ' ) - c ( 5 ' )P(l)-C(I 1) 18237) P(2)--C(2 1) 183.3(9) P( l')-c( 1 1 ') 18 1.3(9) P(2')-c(21')P( 1 )-c( 12) 180.7(8) W)-c(22) 179.7(9) P( 1 ')-c( 12') 180.7(10) P(2')-c( 22')P( 1 )-C( 13 1) 17935) P( 2)-c(23 1 ) 1 8 1.7(6) P( 1 ')-c( 13 1') 17935) P(2')-c(231')23 5.7(4)207.8(9)228.4(9)232.8( 9)198.I( 13)178.3(11)171.5(11)179.6(11)174.q 12)186.q 10)177.7( 10)1 84.q 12)1 80.q 12)176.4(11)1 12(2)1 10(2)103( 3)1 26( 2)135.0(8)142.1 ( 10)182.4(8)1 8 2 3 8)18 I.l(6)orientation of the methoxy groups with respect to the B(2)-0(2) related derivative [(PMe,Ph),RhHB,,H,Cl(OMe)] are inbond. A drawing of the two rotamers is given in Figure 2 and Tables 4 and 5, and Figure 3, and the Experimental section.selected interatomic distances and angles are in Tables 2 and 3 The geometries of all three crystallographically independentrespectively. clusters [Figures 2(a), 2(6), and 31 are very similar so we discussThe n.m.r. data and X-ray diffraction results of the closely them as one except where specifically indicated. The grosJ. CHEM. soc. DALTON TRANS. 1986 519Table 3. Selected angles (”) between interatomic vectors for the two independent molecules of isocfoso-[(PMe,Ph),RhHB,,H,(OMe),]( i ) About the rhodium atomMolecule A95.6(2)116.5(3)95.2(3)87.7(3)9743)146.5(2)165.4(1)5 1 .q3)9 1.9( 3)128.9(3)42.9(2)9 1.2(3)88.9(3)72.5(3)50.5(3)(ii) Boron-boron -boronB(3FB(2bB(7) 90.3(5)B(2)-B(3)-B(4) 126.7(6)B(3FB(4kB(5) 123.0(6)(iii) Others0(2)-B(2FRh( 1) 154.q4)0(2)-B(2)-B(7) 124.9(5)0(2)-B(2)-B(8) 109.2(5)0(2)-B(2)-H( 1,2) 100.2( 1 1)B(2)-0(2W(2) 123.1(5)Rh( I )-H( 1,2)-B(2) 89.q 1 1)O(~)-B(W30-) 129.W)109.3(3)160.2(3)154.2(2)103.7(3)9 1.1 (2)94.0(2)49.7(2)91.8(3)43.9(2)90.9(4)88.4(2)73.0(3)49.2(3)95.1(5)126.2(6)124.2(6)130.0(6)130.4(6)132.3(5)126.5(7)125.1(7)Molecule BP( l’)-Rh(l’)-P(2’) 95.2(2)P( 1’)-Rh( l’)-B(2’) 104.9(3)P(l’)-Rh(l’)-B(3’) 92.2(3)P( 1 ’)-Rh( 1 ’)-B(4’) 9 1.8(3)P(l’)-Rh(l’)-B(5’) 106.6(3)P(I’)-Rh(l’)-B(6’) 157.0(2)P( 1’)-Rh( l’)-B(7’) 156.4(2)B(2’)-Rh( l’kB(3’) 48.3(2)B(2’)-Rh( l‘)-B(4‘) 90.8(3)B(2’)-Rh(1‘)-B(5’) 128.4(3)B(3’)-Rh( l‘)-B(4) 44.0(2)B(3’)-Rh( 1’)-B(5’) 90.7(4)B(3’)-Rh( l’)-B(6’) 89.3(3)B(3‘)-Rh( 1 ‘)-B(7’) 7 1.9(3)B(4‘)-Rh( I’)-B(5’) 48.9(2)P(Z’)-Rh( l’kB(2’) 120.8(3)P(2’)-Rh(l‘)-B(3’) 168.4(2)P(2’)-Rh( l’)-B(4’) 144.2(2)P(2’)-Rh( 1’)-B(5’) 95.7(3)P(2’)-Rh( l’)-B(6’) 87.3(3)P(2’)-Rh( l‘)-B(7’) 98.2(3)B(2’)-Rh(l‘)-B(7’) 51.6(3)B(2’)-Rh( l’)-B(6’) 93.3(3)B(6’)-Rh( I ’)-B(7’) 43.6(2)B(5‘)-Rh( 1 ’)-B(7’) 9 1.2(3)B(4)-Rh(l’)-B(7’) 88.5(3)B(4’)-Rh(l’)-B(6’) 73.6(3)B(5’)-Rh( l’)-B(6’) 50.3(3)B(3’)-B(2’)-B( 7‘) 90.3(5) B(4’)-B(5’)-B(6’) 96.2( 5 )B(2’)-B(3’)-B(4’) 128.0(6) B(2’)-B(7’)-B(6‘) 124.7(6)B(3’)-B(4’)-B(5’) 123.6(6) B(5’)-B(6’)-B(7’) 123.5(6)0(2’)-B(2’)-Rh( 1’) 142.9(4) 0(5’)-B(5’)-Rh(l’) 130.3(5)0(2’)-B(2’)-B(3’) 125.5(6) 0(5’)-B(5’)-B(4) 131.9(5)0(2’)-B(2’)-B(7’) 137.1(5) 0(5’)-B(5’)-B(6’) 130.0(6)0(2’)-B(2’)-B(8’) 1 18.9(5) 0(5’)-B(5‘)-B( 10) 126.2(7)0(2’jB(2’)-H(1‘,2’) 94.7(11)B(2’)-0(2’)-€(2’) 124.0(6) B(5‘)-0(5’-(5’) 121.4(6)Rh( 1’)-H( 1’,2‘)-B(2’) 88.5( 12)Figure 2.ORTEP drawings of the crystallographically determined molecular structure of [(PMe,Ph),RhHB,,H,(OMe),l, with selected organylatoms omitted for clarity. The crystal contains two distinct molecular bond-rotamer configurations: (a) molecule A, (b) molecule Bmolecular cluster structure can be seen to be that of an opennidolarachno ten-vertex decaboranyl cluster fragment with theboat open face capped by the metal atom, resulting in ahexahapto borane-metal linkage.The distances B(3)-B(4) andB(6)-B(7), which average at less than 170 pm, are much shorterthan the corresponding diagnostically long distances of 197 pmin nido-decaborane itself.” This indicates that the ten-boronfragment does not have the straightforward nido-decaboranylproperties of a direct nido-B, ,H 14 derivative (see discussionbelow), which is also indicated by the boron-1 1 n.m.r. shieldingbehaviour of the cluster (Table 1). This shielding behaviour isagain substantially different from that of B,,H,, itself, and alsoindeed different from that of arachno-decaboranyl ten-vertexclusters. 11-1520Table 4.Interatomic distances (Dm) for isocloso-[(PMe,Ph),RhHB,,-H,CI(OMe)](i) To the rhodium atomRh(1)-P( 1) 235.6(4)Rh( 1)-B(2) 2 17.6(9)Rh(l)-B(3) 231.6(10)Rh( 1 )-B(4) 230.2(9)Rh(1)-H(1,2) 165.9(29)(ii) Boron-boronB(2t-B(3) 184.3( 13)B(2HW) 176.4( 12)B(3t-B(8) 178.9( 14)B( 3 kB(9) 178.7( 15)B(4t-W 185.8(14)B(4kW9) 174.8( 15)B(4)-B( 10) 182.0( 14)B(8kW9) 177.0(16)B(9)-B(IO) 174.7(17)B(3t-B(4) 174.q 17)B(9>-B( 1 1 )(iii) Boron-hydrogenB(2)-H(1,2) 128(2)B( 3 )-H( 3 1 105(2)J3(4)-H(4) 118(3)B(9tH(9) 1 13(2)B(8>-H(8) 1 17(3)(ic) OthersB(2kCK2) 181.2(10)P(l)-C(Il) 183.1(8)P(lbC(12) 183.3(10)P( 1 kC( 1 3 1) 180.1(6)236.3(4)206.9(9)225.7( 10)228.6(9)189.7( 14)180.8( 1 1)169.9( 17)183.0( 14)176.8( 14)184.8( 14)175.8( 15)180.6( 14)177.0( 17)1753 15)116(2)116(3)107(3)106( 2)136.2(9)179.8( 10)182.1(8)182.5(6)CI cnUFigure 3.ORTEP drawing of the crystallographically determinedmolecular structure of [(PMe2Ph),RhHB,,H,C1(OMe)]That the electronic structure of the RhB,, cluster conforms toidealized C, symmetry, rather than the idealized C,, symmetryexhibited by the previously described rutheniumarises from the presence of a rhodium-bound hydrogen on theplane containing Rh(1) and the two substituted boron atomsB(2) and B(5). The crystallographic results show that this has aRh( 1 )-H-B(2) bridging configuration, rather than Rh( 1)-HJ.CHEM. SOC. DALTON TRANS. 1986Table 5. Selected angles (") between interatomic vectors for isocfoso-[( PMe, Ph), RhHB ,H,CI(OMe)]( i ) About the rhodium atom94.1(2)116.1(3)164.1(2)147.9(3)98.0(3)87.8(3)94.3(3)48.3(3)90.6(4)128.5(4)92.3(4)89.4(4)73.0( 3)50.0(4)44.3(4)(iii) OthersCw--B(2)-B(3) 129.1(7)C1(2tB(2>-B(7) 127.3(6)C1(2)-B(2)-B(8) 1 13.2(6)B(2)-H(1,2 jRh(1) 94.6(15)C1(2>-B(2)-Rh( 1) 146.7(4)C1(2)-B(2)-H( 1,2) 97.3( 14)115.0(3)96.3(3)89.8(3)98.6(3)148.7(3)165.2(3)9 1.7(4)50.2(4)43.9(4)92.2(4)89.5(4)73.1(3)50.3(4)94.2(6)124.4( 7)124.7(7)130.7(4)131.3(7)132.2(7)126.7(6)122.2(6)terminal, which is consistent with the n.m.r.behaviour (Table1): although the novelty of the bonding configuration meansthat the criteria for n.m.r. behaviour are not established, theincidence and magnitude of the coupling "J(*'B-'H) to thishydride of ca. 50 Hz probably favours a one-bond ' J ( "B-'H)[Rh-H-B(2) bridge] coupling rather than a transoid coupling'B(5)-Rh-'H(terminal)], and the couplings 'J( lo3Rh-'H)and 2J(31P-Rh-'H) (cis) of 12-13 Hz are perhaps smallerthan would be expected for straightforward terminal rhodium-hydride behaviour.There is only a slight tilt of the Rh( 1)P( 1)P(2) bonding planeaway from this hydride position [dihedral angle Rh( 1)P( 1)-P(2)/Rh( 1)B(9)B( 1 1) ca. 13" for the methoxochloro com-pound], which indicates that the P( l)P(2)H( 1,2-bridge) bond-ing disposition is not trigonal about the idealized C, axis of theRhB,, unit, but approximates more closely to RhP(l)P(2)digonal in the Rh(l)B(9)B(ll) plane containing the C, axis. Ifthe closed nature of the cluster implies a closo electronthen the neutral Rh(PMe,Ph),H centre is required to con-tribute four electrons to the cluster scheme.The atomic dis-positions then suggest that this is achieved via an octahedral18-electron d6 rhodium(II1) configuration with a four-orbitalinvolvement in the cluster bonding scheme, structure (I), thefour electrons being formally supplied by the two electrons inthe Rh-H bond of the neutral Rh(PMe,Ph),H unit, togetherwith two straightforward metal valence electrons. Significantcontributions to the metal-borane bonding will then presum-ably occur via three, three-centre bonds, Rh( 1)H( 1,2-bridge)-B(2j, Rh(l)B(3)B(4), and Rh(l)B(6)B(7), together with a two-centre bond, Rh( 1)B(5).Apart from the tilt of the Rh( 1 jP( 1)P(2) plane relative to theC, axis of an idealized C,, B,, configuration, there are othernoteworthy cluster distortions attributable to the presence ofthe bridging hydrogen atom.First, the bridged rhodium-borondistance Rh( 1)-B(2) is significantly longer than Rh(1)-B(5); thiJ. CHEM. SOC. DALTON TRANS. 1986 52 1PI II II I (I Pcould be regarded partly as a consequence of the tilt, but alsoconcomitantly as a result of the conversion of a (hypothetical)M( 1)-B(2) two-electron, two-centre bond [e.g.as in structure(II)] to a three-centre M( 1)-H( 1,2)-B(2) linkage, structure (I).For example, in binary boron hydride chemistry, otherwisesimilar hydrogen-bridged uersus unbridged two-electron inter-boron links commonly differ by up to 20 pm or s ~ . ’ ~ Second, theinterboron distances B(2)-B(3) and B(2)-B(7) to the hydrogen-bridged boron atom B(2) appear to be somewhat longer thanthe corresponding positions at the unbridged end of themolecule, and also longer than those in totally unbridgedspecies such as [( PP~,),RuB,,H,(OE~),].~ One explanation ofthis could involve a reduced electron density in these linkages,the withdrawal arising from the presence of the proton in theRu( 1 )-B(2) bonding link. These particular interboron distancesare in any event long (presumably, in the known unbridgedspecies, indicating a weaker bonding interaction) and thereforewould be particularly susceptible to small changes in electrondensity; in this context, therefore, as yet unquantified bondingfactors associated with the C1 (uersus OMe) ligand in[(PMe,Ph),RhHB, ,H,Cl(OMe)] may have to be invoked toaccount for the diminished lengthening observed for thisspecies, although in this case the possibility of some crystallo-graphic disorder can not be rigorously discounted as the C1atom shows slightly higher thermal parameters than might benormally expected.It is in any event interesting that it is thechlorinated atom B(2) which has the hydrogen bridge ratherthan the alkoxo-substituted B(5); the n.m.r.data show that thisdistinction remains in solution.The incidence of a bridging hydrogen atom on a closedmetallaborane cluster is rare, although several instances inmetallacarbaborane chemistry are recognised and it is knownthat [Bl,H,,]2 can readily be protonated in reasonably acidicsolutions.I6 As far as we are aware in formal metallaboranechemistry, however, the only substantiated instances are in thepolymetallic species isocloso-[(CO), ,HFe4BH2],I7 isocloso-[ (CO) , ,HR u4BH ,I, andcloso-[(q5-C5Hs),Co2B4H6] (together with its alkyl-substitutedderivatives).,’ A species tentatively formulated as [(q5-C,H,)-CoB,,H 1 2 ] would also in principle be in this category butthis has not yet been structurally characterized. This rarity isperhaps surprising, since, for a given structural type, it is theincidence of bridging hydrogen atoms in metallacarbaboranesthat is expected to be proportionately the rarer.This arisesbecause, in the metallacarbaboranes, the excess electrons, overthe nominal 2n. that are required for a stable cluster electroncount are supplied by having carbon instead of (boron +hydrogen), and so the presence of bridging hydrogen atoms tosupply electrons is less necessary (for the given structural type).The relative incidences therefore probably reflect the types andvolume of chemistry that happen to have been studied withinthe two general areas.In terms of a metal complex of a polydentate borane ligand,’the (as yet unsynthesized) unsubstituted parent compoundcloso-[ (q 5-C 5H 5)3C03 B3H J, ’[(PMe,Ph),RhHB,,H,,J would be a notional complex be-tween the ten-electron rhodium(u1) centre [Rh(PMe,Ph),13 +and the quadridentate hexahapto ligand [B,,H, ,I3 - [structure(III)]; this last entity can be regarded as being formally derivedfrom the triple deprotonation of what would be an excited-statenido-B, ,HI, configuration of styx 2802 topology rather thanthe configuration of styx 4620 topology that is in fact exhibitedby (ground-state) B, ,H 14 itself.These considerations lend additional support to the similarconclusions made about the metal-borane bonding in therecently reported compounds [(PR,),MB,,H,(OR’),] (M =Ru or Os, PR, = PMe,Ph or PPh,, R’ = Me or Et),637,22which have similar cluster n.m.r.properties to the rhodiumcompounds (e.g. Table l), and therefore similar clusterelectronic structures. These ruthenium and osmium species arealso believed to have an essentially octahedral metal bonding-orbital configuration with a four-orbital, four-electron contri-bution from the metal centre to the cluster bonding scheme[structure (II)], but within the constraints of an overall 16-electron d4 metal configuration, rather than the 18-electron d”one of the rhodium species reported here. The cluster electronicstructures of the rhodium and ruthenium species are related bya notional protonation deprotonation of the two-electronmetal-B(2) bond [cf: structures (I) and (II)]. The four-orbitalinvolvement of the metal centres with the intracluster bonding,rather than the three-orbital involvement implied in classicalcluster bonding theory, merits the descriptor ‘isocloso’ for thesespecies rather than ‘ c l ~ s o ’ .~ It happens that in eleven-vertexclusters the closo and isocloso configurations have similar grossgeometries; ‘9’ in nine-vertex and ten-vertex metallaboranechemistry this is not the case, and markedly different isoclosocompared with closo geometries r e ~ u l t . ~ * ~ ~ - ~ExperimentalGeneral preparative and separatory techniques, and con-ditions for n.m.r. experiments, have been described elsewhererecently. .26Preparation of [ ( PM e , P h ) R h H B , , H (0 Me) ,] ( 1 ) and[(PMe, Ph),RhHB, ,H8C1(OMe)] (2).-[RhCI,(PMe, Ph),],’(1.14 g, 3.63 mmol) and [NEt3H]2[Bl,H,,]28~29 (0.8 g, 2.48mmol) were heated in MeOH (50 cm3) under reflux in anatmosphere of dry nitrogen for 20 min; during this time theorange suspension turned to a dark red solution. The methanolwas removed under reduced pressure at ca.50 “C; the solidresidue was dissolved in CH,CI, ( 5 cm3) and the componentsseparated and purified by repeated preparative-scale t.1.c. onsilica, using dichloromethane-light petroleum (b.p. 60-80 “C)(70:30) as eluant. The first band, of R, ca. 0.6, was not alwayspresent but on occasion was obtained in ca. 2% yield (20 mg); itsyield was not increased by conducting the reaction in thepresence of HCI. It was identified by X-ray crystallography, as[(PMe2Ph),RhHB,,H,C1(OMe)]. At 32 MHz the compoundhad approximate 6( “B) n.m.r.values (CDCI, solution) of-103(1 B), -78(1 B), +10(2B), +3(4B),and -2p.p.m.(2B) (cf: Table 1). The second band, of R, ca. 0.4, was orange andwas identified by multielement n.m.r. spectroscopy and X-raycrystallography as [(PMe,Ph),RhHB1,H8(0Me),] (43 mg,5% yield). Substantial quantities of a further rhodaborane,unstable under the preparative and separatory conditions used,were also present, as were the colourless phosphaboranesBH,(PMe,Ph) and B,H,,(PMe,Ph), both identified by n.m.r.spectroscopy.26X- Rajv Studies.-Intensity data for both compounds werecollected on a Syntex P2, diffractometer operating in the -28scan mode using graphite-monochromatised Mo-K, radiation(A = 71.069 pm) following a standard pr~cedure.~’ The dat522 J.CHEM. SOC. DALTON TRANS. 1986Table 6. Atom co-ordinates ( x 104) for (1)AtomRh( 1 )Rh( 1')P(1)P(2)P( 1 ')P(2')C(11)(312)C(131)C( 132)C( 133)C( 134)C( 135)C( 136)C(2 1 )C(22)C(23 1)C(232)C(233)C(234)C(235)C(236)C(11')C( 12')C( 13 1')C( 132')C( 133')C( 134')C( 135')C( 136')C(21')C(22')C(231')C(232')C(233')C(234')C(235')C(236')B(2)B(3)B(4)B(5)X4 5794 5774 631(2)7 o w 2 )4 856(2)7 029(2)3 434(6)4 046(7)6 353(3)6 878(3)8 2W3)9 129(3)8 W 3 )7 216(3)7 472(6)8 285(6)7 670(4)9 078(4)9 578(4)8 671(4)7 263(4)6 763(4)3 511(7)4 668(7)6 532(3)7 043(3)8 312(3)9 070(3)8 559(3)7 290(3)7 278(6)8 348(6)7 849(3)8 972(3)9 586(3)9 077(3)7 9W3)7 339(3)4 356(6)2 W(6)2 084(6)3 318(7)Y2 2912 4371468(1)3 071(1)2 665( 1)2 353( 1)1862(4)437(4)1 209(2)485(2)897(2)1465(2)1621(2)4 009(4)2 473(5)3 476(2)3 452(2)3 8W2)4 171(2)4 195(2)3 847(2)3 142(5)1683(4)3 310(2)4 083(2)4 608(2)4 360(2)3 587(2)3 062(2)1744(4)3 323(4)1 821(4)2 250(2)1823(2)967(2)539(2)966(2)1 627(4)1438(4)2 066(4)3 069(4)Z84093 4029 301( 1)8 878(1)4 720(1)3 391(1)8 961(4)10 156(3)9 614(2)9 124l2)9 339(2)10 043(2)10 533(2)10 318(2)8 526(4)8 561(5)9 884(2)10 233(2)11 ool(2)11 421(2)11 072(2)10 304(2)5 134(3)5 327(2)5 186(2)5 643(2)6 242(2)6 384(2)5 926(2)2 508(3)3 508(4)4 058(2)4 667(2)5 169(2)5 062(2)4 452(2)3 950(2)7 220(3)7 586(4)8 296(4)8 863(4)4 995(4)r3 847(7)4 295(6)2 765(6)1395(6)1925(7)2 520(7)2 784(6)2 072(6)2 934(7)4 747(7)4 474(7)3 567(7)1717(6)1 606(7)3 1 74(7)2 595(7)4 792(4)6 @w6)3 430(5)2 581(9)2 241(4)755(6)5 728(8)5 233( 13)2 341(13)1 433( 13)4 471(13)5 272( 13)2 329(14)308( 13)1 113(13)2 045( 14)4 235(14)1314(13)2 901(14)5 393( 13)3 965(13)766( I 3)658( 13)3 037( 14)2 079( 14)5 794(5)J'3 412(4)2 775(4)1957(4)2 111(4)3 057(4)2 974(4)1 317(4)2 270(4)3 29 l(4)2 783(4)1 722(4)2 778(4)3 466(4)2 465(4)1 145(3)790(4)3 473(3)4 o w 6 )I47(4)3 m ( 4 )1 774(4)547(2)4 301(2)5 03 l(4)1511(13)758( 13)1 786(13)4 070( 12)3 054(13)1 739(13)1 874(12)3 444(13)3 337(13)1 376( 13)2 148(13)3 748( 13)2 929(12)1216(13)1 235(12)2 913(12)3 959( 13)2 386( 13)Z8 056(4)7 318(3)6 852(4)7 381(4)8 064(4)7 2 17(4)2 943(4)3 229(4)3 337(4)3 151(3)2 267(3)2 1 50(3)2 271(4)2 509(4)2 428(4)1 819(4)6 fw2)6 752(4)9 578(3)9 812(5)3 050(3)2 834(4)3 431(2)3 159(4)7 802( 12)7 467( 12)8 729( 12)8 297( 12)7 071(12)6 241(13)7 163(12)8 231(12)6 841(13)3 357( 13)3 670( 12)3 830(12)1 989( 12)1 879(12)1 957( 12)2 398( 12)2 193(13)1 133(13)Table 7.Atom co-ordinates ( x 10") for (2)AtomRh( 1)P(1)P(2) cu 1)C(11)C( 12)C(131)C( 132)C( 133)C( 134)C( 135)C( 136)C(2 1 )C(22)C(231)C(232)C(233)C(234)C(235)C(236)X2 5851231(1)3 956(1)2 625(3)919(6)1419(3)1 538(5)1631(3)1512(3)3 875(6)5 295(5)4 105(3)4 027(3)4 184(3)4 419(3)- 54(5)1406(3)1 W 3 )4 497(3)4 340(3)Y2 07993 l(2)957( 1)1970(2)1 188(5)925(7)- 432(3)- 1 251(3)- 2 289(3)-2 509(3)- 1 690(3)- 652(3)1 M ( 6 )- 265(3)- 1 251(3)- 2 163(3)- 2 089(3)-1 103(3)- 192(3)548(6)3 5773 165(1)3 144(1)5 846( 1)3 624(5)2 102(4)3 429(3)2 876(3)3 132(3)3 940(3)4 492(3)4 237(3)2 123(4)3 231(5)3 702(2)3 341(2)3 788(2)4 595(2)4 956(2)4 510(2)Y2 61 7(7)3 622(6)2 551(7)1481(7)I485(6)2 561(8)3 201(8)2 503(8)1833(7)2 553(5)2 545(9)2 524( 18)4 398( 17)4 496( 17)728( 17)764( 16)2 403( 17)3 755(17)2 354(18)1415(17)3 M ( 6 )Y2 465(5)3 210(7)3 520(6)3 431(6)3 135(6)3 851(6)3 093(5)4 473(7)4 373(5)4 422(7)2 892(3)3 71 l(6)1 575(17)3 041(17)3 452( 17)3 406(17)2 834(17)4 284(17)5 131(17)4 940(17)5 129(17)4 836(4)4 304(6)3 296(6)2 615(4)3 3 16(6)4 300(6)4 784(5)3 976(8)3 084(5)3 996(7)1820(3)1 246(4)4 485(16)4 536(16)3 061(17)2 929( 16)4 W 1 6 )5 386( 16)4 140(16)2 632( 16)4 112(16J.CHEM. SOC. DALTON TRANS. 1986 523sets for both compounds were corrected for absorption empiri-cally., ' Both compounds were solved via standard heavy-atomtechniques and refined by full-matrix least-squares [for com-pound (1) in two blocks, one molecule per block], using theSHELX program system.,, Refinement for both compoundswas essentially the same with all non-hydrogen atoms assignedanisotropic thermal parameters and phenyl groups included inrefinement as rigid bodies with idealised hexagonal geometry(C-C 139.5 pm).All phenyl and methyl hydrogen atoms wereincluded in calculated positions using AFIX routines in theSHELX program (C-H 108 pm) and were assigned an overallisotropic thermal parameter for each group. All other hydrogenatoms were located experimentally and were freely refined withindividual isotropic thermal parameters. For the methoxo-chloro compound (2), unit weights were applied throughoutwhile for the dimethoxo compound (l), the weighting schemew = l/[a2(F,,) + g(F,)'] was used in which the parameter gwas included in refinement to give a flat analysis of variancewith increasing sin0 and (F/FmaX.)*.Atomic co-ordinates forcompounds (1) and (2) are given in Tables 6 and 7 respectively.Crystal data for compound (1). C,,H,,B,,O,P,Rh, M =558.44, triclinic, a = 948.8(4), b = 1675.5(6), c = 1 855.0(6)pm, a = 101.48(3), p = 99.55(3), y = 99.82(3)", U = 2.786nm3, 2 = 4, space group PT, D, = 1.33 g cm-,, p = 6.63 cm-',F(O00) = 1 152.Data collection. Scans running from l o below K,, to 1" aboveKa2, scan speeds 2.0-29.3' min-', 4.0 < 20 < 45.0". 7 317Unique reflections, 6 764 observed [ I > 1.50(I)], T = 290 K.Structure rejinement.Number of parameters 688, weightingfactor g = O.OOO1, R = 0.0472, R' = 0.0534.Crystal data for compound (2). C,,H,,B,,CIOP,Rh, M =562.88, orthorhombic, a = 1 267.5(3), b = 1269.9(3), c =1683.4(3) pm, c/ = 2.710 nm3, 2 = 4, space group P2,2,2,,D, = 1.27 g ~ m - ~ , p = 7.71 cm--', F(OO0) = 1 144.Data collection. Parameters as for (I). 2 651 Uniquereflections, 2 527 observed [ I > lSa(l)].Structure re$nement. Number of parameters 323, unitweights, R = 0.0348.AcknowledgementsWe thank the S.E.R.C. for support and Dr. D. Reed (Universityof Edinburgh) for services in high-field n.m.r. spectroscopy.References1 J. E. Crook, N. N. Greenwood, and J. D. Kennedy, unpublished work.2 J. E. Crook, Ph.D. Thesis, University of Leeds, 1982, and3 J.E. Crook, N. N. Greenwood, J. D. Kennedy, and W. S. McDonald,unpublished work.J. Chem. SOC., Chem. Commun., 1981,933.4 J. E. Crook, N. N. Greenwood, J. D. Kennedy, and W. S. McDonald,J. Chem. SOC., Chem. Commun., 1982,383.5 J. E. Crook, N. N. Greenwood, J. D. Kennedy, and W. S. McDonald,J. Chem. SOC., Chem. Commun., 1983,83.6 J. E. Crook, M. Elrington, N. N. Greenwood, J. D. Kennedy, andJ. D. Woollins, Polyhedron, 1984,3,901.7 J. E. Crook, M. Elrington, N. N. Greenwood, J. D. Kennedy, M.Thornton-Pett, and J. D. Woollins, J. Chem. SOC., Dalton Trans.,1985,2407.8 M. Elrington, N. N. Greenwood, J. D. Kennedy, and M. Thornton-Pett, J. Chem. SOC., Chem. Commun., 1984, 1398.9 J. D. Kennedy, Prog. Inorg. Chem., 1984,32,591 and unpublished work.10 A.Tippe and W. C. Hamilton, Inorg. Chem., 1969, 8, 464 and refs.therein.11 M. A. Beckett and J. D. Kennedy, J. Chem. SOC., Chem. Commun.,1983,275.12 J. D. Kennedy, in 'NMR in Inorganic and OrganometallicChemistry,' ed. J. Mason, Plenum, New York, in the press.13 J. E. Crook, N. N. Greenwood, J. D. Kennedy, and W. S. McDonald,J. Chem. SOC., Dalton Trans., 1984,2487.14 L. Barton, Top. Curr. Chem., 1982,100,169.15 R. N. Grimes, in 'Metal Interactions with Boron Clusters,' ed. R. N.Grimes, Plenum, New York, 1982, p. 269; R. N. Grimes, in'Comprehensive Organometallic Chemistry,' eds. G. Wilkinson,F. G. A. Stone, and E. W. Abel, Pergamon, Oxford, 1982, vol. 1, p. 459.16 P. A. Wegner, D. M. Adams, F. J. Callabretta, L. T. Spada, and R. G.Unger, J. Am. Chem. SOC., 1973,%, 7513.17 K. S. Wong, W. R. Scheidt, and T. P. Fehlner, J. Am. Chem. SOC.,1982, 104, 11 11.18 C. R. Eady, B. F. G. Johnson, and J. Lewis, J. Chem. SOC., DaltonTrans., 1977, 477.19 J. R. Pipal and R. N. Grimes, Inorg. Chem., 1977, 16, 3255.20 J. R. Pipal and R. N. Grimes, Inorg. Chem., 1979, 18, 252.21 G. J. Zimmerman, L. W. Hall, and L. G. Sneddon, Inorg. Chem.,22 M. Elrington, Ph.D. Thesis, University of Leeds, 1985, and23 J. Bould, Ph.D. Thesis, University of Leeds, 1983.24 J. Bould, J. E. Crook, N. N. Greenwood, J. D. Kennedy, and W. S.25 J. Bould, N. N. Greenwood, J. D. Kennedy, and W. S. McDonald, J.26 M. J. Hails, N. N. Greenwood, J. D. Kennedy, and W. S. McDonald,27 P. R. Brookes and B. L. Shaw, J. Chem. SOC. A, 1967, 1079.28 M. F. Hawthorne and A. R. Pittochelli, J. Am. Chem. SOC., 1959,81,29 M. F. Hawthorne, R. L. Pilling, and R. N. Grimes,J. Am. Chem. SOC.,30 A. Modinos and P. Woodward, J. Chem. SOC., Dalton Trans., 1981,31 N. Walker and P. Stuart, Acta Crystallogr., Sect. A, 1983, 39, 158.32 G. M. Sheldrick, SHELX 76, Program system for X-ray structure1980, 19, 3642.unpublished work.McDonald, J. Chem. SOC., Chem. Commun., 1982, 346.Chem. SOC., Chem. Commun., 1982,465.J. Chem. SOC., Dalton Trans., 1985, 953.5519.1964,86, 5338.1415.determination, University of Cambridge, 1976.Received 17th April 1985; Paper 5163

ISSN:1477-9226    

DOI:10.1039/DT9860000517

出版商:RSC    

年代:1986

数据来源: RSC