Group 10 transition-metal complexes of an ambiphilic PSB-ligand: Investigations into η3(BCC)-triarylborane coordination

Article abstract of DOI:10.1021/om800670e

Reaction of 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9- dimethylthioxanthene (TXPB) with [PdCl₂(COD)] resulted in the formation of [PdCl(μ-Cl)(TXPB)] (3), which can be reduced in a stepwise fashion, forming [Pd(TXPB)] (2) via [{Pd^I(μ-Cl)(TXPB)} ₂] (4). Dinuclear 4 could also be prepared through a comproportionation reaction of palladium(II) complex [PdCl(μ-Cl)(TXPB)] (3) with either [Pd(TXPB)] (2) or [Pd(dba)(TXPB)] (5). In complexes 3 and 4, the TXPB ligand is bound to palladium via the phosphine and thioether donors, with a chloride anion bridging between the metal and the borane unit of TXPB. By contrast, the TXPB ligand in 2 is bound to palladium not only via the phosphine and thioether donors but also through a Pd-(η³-BAr₃) linkage involving boron and the ipsoand ortho-carbon atoms of one B-phenyl ring. The analogous nickel complex, [Ni(TXPB)] (6) also proved accessible by direct reaction of [Ni(COD)₂] with TXPB. In both 2 and 6, short distances (2.02-2.33 A) between the metal and the B-C_ipso-C _ortho unit of TXPB and ¹¹B NMR signals shifted 38-39 ppm to lower frequency of free TXPB confirm the presence of a strong M- {η³(BC)C-BAr₃,} interaction. Reaction of either [Pd₂(dvds)₃] (dvds = 1,3-divinyltetramethyldisiloxane) with TXPB or complex 2 with dvds resulted in rapid formation of [(κ¹-TXPB)Pd(η²:η²2-dvds)] (7). The platinum analogue of complex 7, [(κ¹-TXPB) Pt(η²:η²-dvds)] (8), was also prepared by reaction of [Pt(COD)₂] with dvds, followed by TXPB. In both 7 and 8, the metal is trigonal planar as a result of η²:η²- coordination to dvds and bonding only to the phosphine group of TXPB. To assess the potential for a ligand with the same structural characteristics as TXPB to coordinate via three η¹-interactions, the phosphine analogue of TXPB; 2,7-di-ferf-butyl-4,5-bis(diphenylphosphino)-9,9-dimethylthioxanthene (Thioxantphos) was prepared, and reaction with [PtX₂(COD)] resulted in the clean formation of [PtX(Thioxantphos)]X where X = Cl (9) and I (10). These complexes are square planar with the Thioxantphos ligand coordinated through three η¹-interactions, confirming the steric accessibility of more traditional κ³-coordination in 4,5-disubstituted thioxanthene ligands such as Thioxantphos and TXPB.

Full text of DOI:10.1021/om800670e

Organometallics 2008, 27, 5317–5325
5317
Group 10 Transition-Metal Complexes of an Ambiphilic
PSB-Ligand: Investigations into η3(BCC)-Triarylborane
Coordination
David J. H. Emslie,* Laura E. Harrington,† Hilary A. Jenkins,† Craig M. Robertson,† and
James F. Britten†
Department of Chemistry, McMaster UniVersity, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada
ReceiVed July 15, 2008
Reaction of 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene (TXPB)
with [PdCl2(COD)] resulted in the formation of [PdCl(µ-Cl)(TXPB)] (3), which can be reduced in a
stepwise fashion, forming [Pd(TXPB)] (2) via [{PdI(µ-Cl)(TXPB)}2] (4). Dinuclear 4 could also be
prepared through a comproportionation reaction of palladium(II) complex [PdCl(µ-Cl)(TXPB)] (3) with
either [Pd(TXPB)] (2) or [Pd(dba)(TXPB)] (5). In complexes 3 and 4, the TXPB ligand is bound to
palladium via the phosphine and thioether donors, with a chloride anion bridging between the metal and
the borane unit of TXPB. By contrast, the TXPB ligand in 2 is bound to palladium not only via the
phosphine and thioether donors but also through a Pd-(η3-BAr3) linkage involving boron and the ipso-
and ortho-carbon atoms of one B-phenyl ring. The analogous nickel complex, [Ni(TXPB)] (6) also proved
accessible by direct reaction of [Ni(COD)2] with TXPB. In both 2 and 6, short distances (2.02-2.33 Å)
between the metal and the B-Cipso-Cortho unit of TXPB and 11B NMR signals shifted 38-39 ppm to
lower frequency of free TXPB confirm the presence of a strong M-{η3(BCC)-BAr3} interaction. Reaction
of either [Pd2(dvds)3] (dvds ) 1,3-divinyltetramethyldisiloxane) with TXPB or complex 2 with dvds
resulted in rapid formation of [(κ1-TXPB)Pd(η2:η2-dvds)] (7). The platinum analogue of complex 7,
[(κ1-TXPB)Pt(η2:η2-dvds)] (8), was also prepared by reaction of [Pt(COD)2] with dvds, followed by
TXPB. In both 7 and 8, the metal is trigonal planar as a result of η2:η2-coordination to dvds and bonding
only to the phosphine group of TXPB. To assess the potential for a ligand with the same structural
characteristics as TXPB to coordinate via three η1-interactions, the phosphine analogue of TXPB; 2,7-
di-tert-butyl-4,5-bis(diphenylphosphino)-9,9-dimethylthioxanthene (Thioxantphos) was prepared, and
reaction with [PtX2(COD)] resulted in the clean formation of [PtX(Thioxantphos)]X where X ) Cl (9)
and I (10). These complexes are square planar with the Thioxantphos ligand coordinated through three
η1-interactions, confirming the steric accessibility of more traditional κ3-coordination in 4,5-disubstituted
thioxanthene ligands such as Thioxantphos and TXPB.
σ-acceptors with respect to a coordinated metal.9-11 Besides
fundamental studies into the electronic consequences and
Introduction
A wide variety of compounds containing transition metal-
boron interactions have been reported, including polyhedral
borane and carborane complexes,1 complexes of boron-contain-
ing cyclic π-ligands (e.g., anionic boratabenzenes and dianionic
boroles),2 boryl (LxM-BR2), borylene (LxMdBR), boride, and
borane (LxMfBR3) complexes,3,4 borataalkene {LxM-(η2-
R2BCR2)} complexes,5,6 and metal-(HBR2) σ-complexes.7
However, within this group, borane ligands are unique5,8 as zero-
electron (Z-type) ligands which can be considered to act as
(5) Tantalum borataalkene complexes of the form [Cp2Ta{CH2B-
(C6F5)2}] and [Cp2TaL{CH2B(C6F5)2}] (L ) CO or t-BuNC) have been
investigated, and the η2-borataalkene bonding mode has been considered
either to mirror the Dewar-Chatt-Duncanson model for olefins or to
involve of a covalent Ta-C σ-bond and a metal to boron dative bond. Both
olefin-like reactivity and reactivity that likely involves an η1-coordinated
form of the borataalkene ligand have been observed: (a) Cook, K. S.; Piers,
W. E.; Rettig, S. J Organometallics 1999, 18, 1575. (b) Cook, K. S.; Piers,
W. E.; Woo, T. K.; McDonald, R. Organometallics 2001, 20, 3927. (c)
Cook, K. S.; Piers, W. E.; McDonald, R. J. Am. Chem. Soc. 2002, 124,
5411. (d) Cook, K. S.; Piers, W. E.; Hayes, P. G.; Parvez, M. Organome-
tallics 2002, 21, 2422.
* To whom correspondence should be addressed. Phone: 905-525-9140.
Fax: 905-522-2509. E-mail: emslied@mcmaster.ca.
(6) (a) Zhang, S.; Piers, W. E.; Gao, X.; Parvez, M. J. Am. Chem. Soc.
2000, 122, 5499. (b) Scollard, J. D.; McConville, D. H.; Rettig, S. J.
Organometallics 1997, 16, 1810. (c) Thorn, M. G.; Vilardo, J. S.; Fanwick,
P. E.; Rothwell, I. P. Chem. Commun. 1998, 2427.
† McMaster Analytical X-Ray Diffraction Facility.
(1) (a) Casanova, J. The borane, carborane, carbocation continuum;
Wiley: New York, 1998. (b) Grimes, R. N. Metal Interactions with Boron
Clusters; Plenum Press: New York, 1982.
(7) Kubas, G. J. J. Organomet. Chem. 2001, 635, 37.
(2) (a) Herberich, G. E.; Ohst, H. AdV. Organomet. Chem. 1986, 25,
199. (b) Fu, G. C. AdV. Organomet. Chem. 2001, 47, 101. (c) Herberich,
G. E. In ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone,
F. G. A., Wilkinson, G., Ed.; Pergamon Press: Oxford, 1995; Vol. 1, p
197.
(3) (a) Braunschweig, H.; Colling, M. Coord. Chem. ReV. 2001, 223, 1.
(b) Braunschweig, H.; Kollann, C.; Rais, D. Angew. Chem., Int. Ed. 2006,
45, 5254. (c) Braunschweig, H.; Whittell, G. R. Chem.sEur. J. 2005, 11,
6128. (d) Aldridge, S.; Coombs, D. L. Coord. Chem. ReV. 2004, 248, 535.
(4) Braunschweig, H. Angew. Chem., Int. Ed. 1998, 37, 1786.
(8) Several complexes containing bridging boryl ligands, which may
be considered metal-borane complexes in which one of the borane
substituents is a second metal center (Figure 1, complex D) have been
reported. See, for example: (a) Reference 35. (b) Westcott, S. A.; Marder,
T. B.; Baker, R. T.; Harlow, R. L.; Calabrese, J. C.; Lam, K. C.; Lin, Z.
Polyhedron 2004, 23, 2665. (c) Braunschweig, H.; Radacki, K.; Rais, D.;
Whittell, G. R. Angew. Chem., Int. Ed. 2005, 44, 1192. In parts a and b of
this reference, the boryl ligand adopts an unsymmetrical bridging mode,
while in part c, approximately symmetrical bridging with near tetrahedral
geometry at boron was observed.
10.1021/om800670e CCC: $40.75
2008 American Chemical Society
Publication on Web 09/18/2008

5318 Organometallics, Vol. 27, No. 20, 2008
Emslie et al.
Figure 1. Representative group 10 metal-borane and closely related complexes: A,32,33 B,25,27,30,34 C,21,22,25 D,35 and E.36
metal-ligand interactions involved in metal-borane coordina-
tion, metal-borane complexes are also of great interest for the
development of new catalytic reactivity: (a) as a direct result
of M-BR3 bonding, which increases the coordination number
by one but reduces the d-electron count by two units,10 often
resulting in unusual geometries for a given d-electron config-
uration, (b) due to the potential for pendant or coordinated
borane groups to bind, position and/or activate organic substrates
(bifunctional catalysis), and/or (c) as a result of coligand (e.g.,
Me or Cl) coordination or abstraction.12-18
Despite increased current interest in transition metal-borane
complexes, they are still scarce, perhaps due to difficulties in
the preparation of complexes of this type using boranes that
are not incorporated into an ambiphilic (containing one or more
Lewis basic donor in addition to the borane) ligand framework,
combined with the tendency for potential ambiphilic ligands to
form unreactive or insoluble inter- or intramolecular Lewis
acid-base adducts.19 The first well authenticated4 metal-borane
complex, [CpFe(CO)2(BPh3)]-, was prepared by Burlitch et al.
in 1979.20 However, a crystallographically characterized
metal-borane complex was not reported until 1999 by Hill et
al.; [{κ4-B(mt)3}Ru(CO)(PPh3)] (mt ) N-alkylimazolyl).8 Since
then, various B(mt)3 (Figure 1, parts B and C) as well as
RB(mt)2 and B(taz)3 (taz ) 3,4-dialkyl-5-thioxo-1,2,4-triazolyl)
complexes have been reported by Hill (M ) Ru, Os, Pt, Rh,
Ir)11,21-25 and Parkin (M ) Rh, Ir, Ni, Pd, Fe),26-28 as well as
Connelly, Tatsumi, and Rabinovich (M ) Rh, Ni, and Co,
(17) Both early and late transition-metal complexes of borane-appended
cyclopentadienyl ligands have been reported, and observed reactivity
includes electrophilic addition to the adjacent cyclopentadienyl ring and
coordination of Lewis bases by the borane, followed in certain cases by
C-H bond activation: (a) Herrmann, C.; Kehr, G.; Fro¨hlich, R.; Erker, G.
Eur. J. Inorg. Chem. 2008, 2273. (b) Herrmann, C.; Kehr, G.; Fro¨hlich, R.;
Erker, G. Organometallics 2008, 27, 2328. (c) Hill, M.; Kehr, G.; Erker,
G.; Kataeva, O.; Fro¨hlich, R. Chem. Commun. 2004, 1020. (d) Hill, M.;
Erker, G.; Kehr, G.; Fro¨hlich, R.; Kataeva, O. J. Am. Chem. Soc. 2004,
126, 11046. (e) Hill, M.; Kehr, G.; Fro¨hlich, R.; Erker, G. Eur. J. Inorg.
Chem. 2003, 3583.
(18) See refs 40 and 41 for complexes containing M-Cl-BR3 interac-
tions.
(19) (a) Weis, N.; Pritzkow, H.; Siebert, W. Eur. J. Inorg. Chem. 1999,
7. (b) Go¨rz, D.; Pritzkow, H.; Siebert, W. Eur. J. Inorg. Chem. 2003, 2783.
(c) Mu¨ller, G.; Lachmann, J. Z. Naturforsch. B 1993, 48, 1248. (d) Rathke,
J.; Schaeffer, R. Inorg. Chem. 1972, 11, 1150. (e) Sugihara, Y.; Miyatake,
R.; Takakura, K.; Yano, S. Chem. Commun. 1994, 1925. (f) Giles, R. L.;
Howard, J. A. K.; Patrick, L. G. F.; Probert, M. R.; Smith, G. E.; Whiting,
A. J. Organomet. Chem. 2003, 680, 257. (g) Spies, P.; Fro¨hlich, R.; Kehr,
G.; Erker, G.; Grimme, S. Chem.sEur. J. 2008, 14, 333.
(9) Sircoglou, M.; Bontemps, S.; Mercy, M.; Saffon, N.; Takahashi, M.;
Bouhadir, G.; Maron, L.; Bourissou, D. Angew. Chem., Int. Ed. Engl. 2007,
46, 8583.
(10) Parkin, G. Organometallics 2006, 25, 4744.
(11) Hill, A. F. Organometallics 2006, 25, 4741.
(12) Formal 1,2-addition of X2 or XY across the Fe-BR3 bond in [{κ4-
B(mimtBu)3}Fe(CO)2] has been reported using (O2CPh)2, CHCl3, CHBr3,
or I2/CHCl3. In addition, reaction of [{κ4-B(mimtBu)3}NiCl] with XeF2 gave
[{κ3-FB(mimtBu)3}NiCl], while reaction with I2, CHBr3, or CHCl3 gave
[{κ3-ClB(mimtBu)3}NiX] (X ) I, Br, or Cl), and reaction of [{κ4-
B(mimtBu)3}NiX] (X ) Cl, NCS, or N3) with I2 gave [{κ3-XB(mimtBu)3NiI]:
ref 26.
(20) [CpFe(CO)2(BPh3)]– was characterized spectroscopically, but an
X-ray crystal structure was not obtained. However, X-ray crystal structures
for both the the AlPh3 analogue, [CpFe(CO)2(AlPh3)]–, and the product of
[CpFe(CO)2(BPh3)]– decomposition in THF, [(Ph3BC5H4)Fe2(CO)4-
Cp]–, were obtained: (a) Burlitch, J. M.; Burk, J. H.; Leonowicz, M. E.;
Hughes, R. E. Inorg. Chem. 1979, 18, 1702. (b) Burlitch, J. M.; Leonowicz,
M. E.; Petersen, R. B.; Hughes, R. E. Inorg. Chem. 1979, 18, 1097.
(21) Crossley, I. R.; Hill, A. F.; Willis, A. C. Organometallics 2008,
27, 312.
(13) The reaction of Na[H2B(mt)2] with [RhCl(CS)(PPh3)2] resulted in
formation of [LRhH(PPh3)] [L ) {H(mt)2B}(Ph3P)CdS] in which CS has
been converted to a zwitterionic (R3B)(Ph3P)CdS ligand. This reaction is
considered to proceed via the intermediate [{κ3-HB(mt)2}RhH(CS)(PPh3)]:
ref 24e.
(22) Crossley, I. R.; Hill, A. F. Dalton Trans. 2008, 201.
(14) Reaction of [(dmpe)NiMe2] with Ph2P(CH2)2BR2 (BR2 ) BCy2 or
BBN) resulted in the formation of zwitterionic [(dmpe)NiMe(κ1-Ph2P-
(CH2)2BR2Me)] as a result of methyl abstraction by the borane: ref 34.
(15) Reaction of [Pd2(dba)3] with TXPB gave [Pd(dba)(TXPB)] (5,
Scheme 1) which is best regarded as a zwitterionic η3-boratoxyallyl
complex: ref 39.
(16) A substantial rate enhancement has been reported for the dehy-
drogenative coupling of PhSiH3 by [(Me-Ind)NiMe(PPh3)] in the presence
of Me2PCH2AlMe2. The proposed intermediate in this reactivity is [(Me-
Ind)NiMe{Me2PCH2AlMe2}]. A related rhodium complex, [Cp*RhMe2{κ1-
Me2PCH2AlMe2-OSMe2}], has also been prepared:(a) Fontaine, F.-G.;
Zargarian, D. J. Am. Chem. Soc. 2004, 126, 8786. (b) Thibault, M.-H.;
Boudreau, J.; Mathiotte, S.; Drouin, F.; Sigouin, O.; Michaud, A.; Fontaine,
F.-G. Organometallics 2007, 26, 3807.
(23) (a) Crossley, I. R.; Hill, A. F.; Willis, A. C. Organometallics 2006,
25, 289. (b) Crossley, I. R.; Hill, A. F.; Humphrey, E. R.; Willis, A. C.
Organometallics 2005, 24, 4083. (c) Crossley, I. R.; Foreman, M. R.; St,
J.; Hill, A. F.; White, A. J. P.; Williams, D. J. Chem. Commun. 2005, 221.
(24) (a) Crossley, I. R.; Hill, A. F.; Willis, A. C. Organometallics 2005,
24, 4889. (b) Crossley, I. R.; Hill, A. F.; Willis, A. C. Organometallics
2005, 24, 1062. (c) Foreman, M. R; St, J.; Hill, A. F.; White, A. J. P.;
Williams, D. J. Organometallics 2004, 23, 913. (d) Foreman, M. R. St.-J.;
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2003, 22, 4446. (e) Crossley, I. R.; Hill, A. F.; Willis, A. C. Organometallics
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(25) Crossley, I. R.; Hill, A. F. Organometallics 2004, 23, 5656.

InVestigations into η3(BCC)-Triarylborane Coordination
Organometallics, Vol. 27, No. 20, 2008 5319
Scheme 1. Preparation of Complexes 2-5a
respectively).29-31 All of these complexes were prepared starting
from anionic HB(mt)3, HBR(mt)2, or HB(taz)3 ligands, with the
borane ligand formed through various processes, including
H-migration from boron to a coordinated metal or formal
elimination of HR, HX, or H+ from an initial precursor complex.
In contrast to the ambiphilic ligands described above, which
are generated in situ at a coordinated metal, several free
ambiphilic triarylborane-containing ligands Ph(3-n)B{C6H4(PR2)-
o}n (R ) i-Pr or Ph; n ) 2 or 3) and FluB{C6H4(P-i-Pr2)-o}
(BFlu ) borafluorenyl) were recently reported (2006-2008)
by Bourissou et al. and successfully deployed for the formation
of metal-borane complexes with Rh, Pd, Pt, and Au (Figure
1A).9,32,33,37,38 In 2006, we also reported a free ambiphilic
ligand; a phosphine-thioether-borane ligand based on the rigid
thioxanthene backbone (TXPB; Scheme 1).39 Reaction of TXPB
with 0.5[Rh(µ-Cl)(CO)2}2] gave [(TXPB)Rh(µ-Cl)(CO)] in
which the borane engages in a Rh-Cl-BR3 bridging interaction,
and subsequent reaction with K[CpFe(CO)2] resulted in chloride
substitution to form heterobimetallic [(TXPB)Rh(µ-CO)2Fe(CO)-
Cp] (1). The X-ray crystal structure of 1 revealed the presence
of a unique M-(η3-BAr3) interaction (M ) Rh) involving boron
and the ipso- and ortho-carbon atoms on one B-phenyl ring
(Scheme 1), rather than a more typical M-(η1-BAr3) interac-
tion.40 An interaction of this type between a vinyl- or arylborane
and a metal had not previously been reported, and intriguingly,
only M-(η1-BAr3) interactions have been observed in the
metal-triarylborane complexes reported by Bourissou.
Although in complex 1, close approach of the B-Cipso-Cortho
unit to the metal could perhaps be attributed to the presence
only of an η2-interaction between rhodium and one B-phenyl
ring, or considered simply a consequence of the rigidity of the
TXPB ligand, a significant Rh-{η3(BCC)-BAr3} interaction was
proposed on basis of DFT calculations, a substantial upfield shift
of the 11B NMR signal relative to that of the free ligand, Rh-B,
Rh-Cipso, and Rh-Cortho distances of 2.63(2), 1.97(2), and
2.03(2) Å, respectively, and a relatively short P · · · B distance
[4.77(2) Å]. DFT calculations also highlighted the presence of
significant delocalization within the η3-coordinated BCC unit to
a
Dashed arrows indicate previously reported reactivity.
Scheme 2. Preparation of Complexes 6-8
(26) (a) Pang, K.; Tanski, J. M.; Parkin, G. Chem. Commun. 2008, 1008.
(b) Figueroa, J. S.; Melnick, J. G.; Parkin, G. Inorg. Chem. 2006, 45, 7056.
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(28) Landry, V. K.; Melnick, J. G.; Buccella, D.; Pang, K.; Ulichny,
J. C.; Parkin, G. Inorg. Chem. 2006, 45, 2588.
(29) Blagg, R. J.; Charmant, J. P. H.; Connelly, N. G.; Haddow, M. F.;
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moto, T.; Kawaguchi, H.; Tatsumi, K. Inorg. Chem. 2006, 45, 9914.
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G. P. A.; Incarvito, C. D.; Rheingold, A. L.; Rabinovich, D. Dalton Trans.
2004, 1626.
(32) Bontemps, S.; Sircoglou, M.; Bouhadir, G.; Puschmann, H.;
Howard, J. A. K.; Dyer, P. W.; Miqueu, K.; Bourissou, D. Chem.sEur. J.
2008, 14, 731.
(33) Bontemps, S.; Bouhadir, G.; Gu, W.; Mercy, M.; Chen, C.-H.;
Foxman, B. M.; Maron, L.; Ozerov, O. V.; Bourissou, D. Angew. Chem.,
Int. Ed. 2008, 47, 1481.
(34) Fischbach, A.; Bazinet, P. R.; Waterman, R.; Tilley, T. D.
Organometallics 2008, 27, 1135.
(35) Curtis, D.; Lesley, M. J. G.; Norman, N. C.; Orpen, A. G.; Starbuck,
J. Dalton Trans. 1999, 1687.
(36) Jiang, F.; Shapiro, P. J.; Fahs, F.; Twamley, B. Angew. Chem., Int.
Ed. 2003, 42, 2651.
(37) Bontemps, S.; Gornitzka, H.; Bouhadir, G.; Miqueu, K.; Bourissou,
D. Angew. Chem., Int. Ed. 2006, 45, 1611.
(38) Bontemps, S.; Bouhadir, G.; Miqueu, K.; Bourissou, D. J. Am.
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the extent that for 1, the most appropriate bonding description is
intermediate between that expected for an isolated borane/alkene
complex and a fully delocalized allyl-like complex. However, the
Rh-B distance in 1 is substantially longer than Rh-B in related
Rh-(η1-BR3) complexes (2.09-2.35 Å),23,28,29,32,37 and low
quality X-ray crystallographic data and the bimetallic nature of
1 complicated further analysis in this system.40 Herein, we
describe the synthesis and reactivity of mononuclear and
monoligated [Pd(TXPB)] (2) and [Ni(TXPB)] (6) which contain
M-{η3(BCC)-BAr3} interactions with metal-boron distances

5320 Organometallics, Vol. 27, No. 20, 2008
Emslie et al.
while the palladium centers are distorted square planar
[Pd-Pd′-S ) 168.84(5)°] with an angle of 67° between the
two coordination planes. Preservation of a strong interaction
between the borane and the chloride ligand in solution is
confirmed by an 11B NMR chemical shift of 2 ppm. Complex
4 can also be prepared through a comproportionation reaction
between palladium(II) complex 3 and either of complexes 2 or
5 (vide infra).
Reaction of 3 or 4 with excess Zn, Mg, or [CoCp2] resulted
in the formation of a new yellow-orange product, [Pd(TXPB)]
(2; Scheme 1).43 1H and 31P NMR spectra showed that complex
2 is also produced in high yield via the reaction of [Pd-
(dba)(TXPB)] (5) with LiNEt2 or LiN(SiMe3)2. We were unable
to determine the fate of the dba molecule in this reaction, but
it clearly does not remain intact since 2 reacts rapidly with dba
to reform complex 5 (Scheme 1).
Figure 2. ORTEP of 4 · hexane with solvent, hydrogen atoms, CMe3
groups, and the ortho, meta, and para carbon atoms of all
unsubstituted phenyl rings omitted for clarity (50% thermal
ellipsoids). Selected bond lengths (Å) and angles (deg): Pd-P
2.197(2), Pd-S 2.382(2), Pd-Cl 2.362(2), Pd-Pd′ 2.530(1), B-Cl
1.981(8), P · · · B 5.391(8), P-Pd-S 83.13(7), S-Pd-Cl 97.22(6),
Cl-Pd-Pd′ 93.78(5), P-Pd-Pd′ 85.93(6), P-Pd-Cl 178.14(7),
S-Pd-Pd′ 168.84(5), Pd-Cl-B 104.0(2), Cl-B-C(42) 106.4(4),
Cl-B-C(36) 106.9(5), Cl-B-C(5) 107.0(5), C(5)-B-C(36)
113.5(6), C(5)-B-C(42) 113.7(6), C(36)-B-C(42) 108.9(5),
ligand bend 39.63(28) [ligand bend ) angle between the planes of
the C(4) ring and the C(5) ring].
The peak at 18 ppm in the 31P NMR spectrum of 2 confirms
palladium coordination by the TXPB ligand, and the 11B NMR
chemical shift at 31 ppm is indicative of 4-coordinate boron
(cf. 69 ppm in free TXPB). The solid-state structure of 2 (Figure
3, Table 1) reveals that the TXPB ligand is bound to palladium
not only via the phosphine and thioether donors but also through
a Pd-{η3(BCC)-BAr3} linkage involving the ipso- and ortho-
carbon atoms of one B-phenyl ring.
much more comparable to those observed in group 10 M-(η1-
BR3) complexes. We also report synthesis of palladium and
platinum complexes containing a free pendant borane (7 and
8) and square-planar [PtX(κ3-Thixantphos)]X [X ) Cl (9); I
(10); Thioxantphos ) the phosphine analogue of TXPB (a PSP-
donor)] complexes which highlight the steric accessibility of a
more traditional κ3-bonding mode [involving M-(η1-BAr3)
coordination] for the TXPB ligand.
While the solid-state structures of 1 and 2 reveal a qualita-
tively similar M-{η3(BCC)-BAr3} bonding mode with ap-
proximate trigonal planarity at boron,44 complex 2 exhibits a
substantially shorter M-B distance [2.320(5) vs 2.63(2) Å]. The
M-Cipso, M-Cortho, and P · · · B distances in 2 are also shorter
than those observed in 1 [M-Cipso ) 2.198(4) vs 2.33(2) Å;
M-Cortho ) 2.325(4) vs 2.46(2) Å; P · · · B ) 4.605(5) vs 4.77(2)
Å], indicative of notably stronger M-{η3(BCC)-BAr3} bonding
in complex 2, relative to complex 1, presumably as a result of
reduced steric congestion and increased electron density at the
metal. These data, in combination with the 11B NMR chemical
shift, indicate that the Pd-{η3(BCC)-BAr3} interaction is
electronic in origin and that close Pd-B approach is due to a
bonding interaction between palladium and boron, rather than
sterically imposed as a result of an η2-interaction between
palladium and a B-phenyl ring.
The M-B distance in 2 is comparable to those in related
palladium and platinum Ph(3-n)B{C6H4(P-i-Pr2)-o}n (n ) 2 or
3) complexes (2.22-2.65 Å)32,33 but is longer than those in Pd
and Pt tris(N-alkylimazolyl)borane complexes (2.05-2.16 Å).21,27
The M-B bond distance in 2 also approaches that of 2.200(5)
Å observed in Shapiro’s [PdCl2{η3-PhB(CHPPh3)2}] (Figure 1),
which is described as a palladium(II) complex of an η3-
coordinated zwitterionic boron-bridged diylide ligand.36
The analogous nickel complex, brick-red [Ni(TXPB)] (6), also
proved accessible through direct reaction of [Ni(COD)2] with
Results and Discussion
Reaction of the TXPB ligand with [PdCl2(COD)] gave orange
[PdCl(µ-Cl)(TXPB)] (3) in 87% isolated yield. Complex 3 was
characterized by NMR spectroscopy (31P δ 58 ppm; 11B δ 13
ppm) and elemental analysis, and by analogy with related [Rh(µ-
Cl)(CO)(TXPB)]40 and complex 4 (vide infra), the structure of
3 can be considered to be square planar with one chloride anion
bridging between palladium and the borane unit of TXPB
(Scheme 1).41
The cyclic voltammogram (CV) of 3 in THF showed an
irreversible reduction at Epc ) -0.94 V vs SCE (ν ) 200 mV
s-1) followed by additional reduction peaks at Epc ) -2.55
and -2.75 V. The first reduction peak at -0.94 V is associated
with an irreversible product peak at Epa ) 0.39 V. Addition of
Zn powder, Mg powder, or [CoCp2] to 3 resulted in the
formation of a new bright orange-red product: [{PdI(µ-
Cl)(TXPB)}2] (4; Scheme 1).
(42) (a) Rutherford, N. M.; Olmstead, M. M.; Balch, A. L. Inorg. Chem.
1984, 23, 2833. (b) Schwalbe, M.; Walther, D.; Schreer, H.; Langer, J.;
Go¨rls, H. J. Organomet. Chem. 2006, 691, 4868. (c) Yi, J.; Miyabayashi,
T.; Ohashi, M.; Yamagata, T.; Mashima, K. Inorg. Chem. 2004, 43, 6596.
(d) Vicente, J.; Abad, J.-A.; Mart´ınez-Viviente, E.; Jones, P. G. Organo-
metallics 2002, 21, 4454. (e) Suzuki, T.; Kashiwabara, K.; Fujita, J. Bull.
Chem. Soc. Jpn. 1995, 68, 1619. (f) Yamamoto, Y.; Yamazaki, H. Bull.
Chem. Soc. Jpn. 1985, 58, 1843.
The solid-state structure revealed that 4 (Figure 2; Table 1)
is a rare example of a neutral palladium(I) dimer containing an
unsupported Pd-Pd bond [2.530(1) Å].42 The TXPB ligand is
P,S-coordinated to palladium(I) with the chloride anion bridging
between palladium and the borane unit of TXPB. The geometry
at boron approaches tetrahedral [Σ(C-B-C) ) 336.1(10)°],
(43) It is worth noting that formation of a complex containing a bridging
metal-halide-borane interaction, followed by reduction to simultaneously
remove halides and increase the nucleophilicity of the metal center,
represents a new and potentially very versatile approach to the synthesis of
low-valent metal-borane complexes.
(41) For other examples of metal-chloride-borane bridging interactions,
see: (a) Vergnaud, J.; Ayed, T.; Hussein, K.; Vendier, L.; Grellier, M.;
Bouhadir, G.; Barthelat, J. C.; Sabo-Etienne, S.; Bourissou, D. Dalton Trans.
2007, 2370. (b) Reference 38. (c) Crevier, T. J.; Bennett, B. K.; Soper,
J. D.; Bowman, J. A.; Dehestani, A.; Hrovat, D. A.; Lovell, S.; Kaminsky,
W.; Mayer, J. M. J. Am. Chem. Soc. 2001, 123, 1059. (d) Lancaster, S. J.;
Al-Benna, S.; Thornton-Pett, M.; Bochmann, M. Organometallics 2000,
19, 1599.
(44) In complexes 1, 2, and 6, η3(BCC)-triarylborane coordination
involves the B-phenyl ring oriented into the fold of the TXPB ligand
backbone. However, in complex 1, rhodium is bound to the ortho carbon
positioned closest to C(5), whereas in complexes 2 and 6, the metal is bound
to the ortho carbon positioned furthest from C(5) (see Scheme 1).

InVestigations into η3(BCC)-Triarylborane Coordination
Organometallics, Vol. 27, No. 20, 2008 5321
Table 1. Crystallographic Data Collection and Refinement Parameters for Complexes 4, 2, 6, 7, and 10a
structure
2 · toluene
4 · hexane
6 · 2hexane
7 · 2hexane
10 · 1.74CH2Cl2
formula
formula wt
T (K)
C54H56BPPdS
885.23
173(2)
C
100H110B2Cl2P2Pd2S2
C59H76BNiPS
917.75
173(2)
C61H80B OPPdSSi2
1065.67
100(2)
C
48.74H51.48Cl3.48I2P2PtS
1743.26
173(2)
1303.52
173(2)
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P2(1)/n
15.9022(16)
12.5955(13)
23.306(3)
90
102.427(2)
90
4558.7(9)
4
1.290
0.523
1848
0.20 × 0.10 × 0.02
1.79-28.35
59472
monoclinic
C2/c
31.3273(12)
14.7189(6)
21.3425(8)
90
91.473(2)
90
9837.8(7)
4
1.177
0.536
3632
0.30 × 0.18 × 0.04
1.30-26.49
40938
triclinic
P1
monoclinic
P2(1)/n
17.160(7)
9.849(4)
36.227(16)
90
96.351(7)
90
6085(5)
4
1.163
0.441
2256
0.49 × 0.17 × 0.04
1.96-22.50
47990
triclinic
P1
j
j
11.3711(18)
13.090(2)
16.842(4)
106.206(5)
97.013(5)
106.216(4)
2256.5(7)
2
1.351
0.553
988
0.40 × 0.30 × 0.02
2.11-28.28
28080
9.8451(4)
15.2773(8)
17.2635(9)
84.9360(10)
84.0330(10)
89.1790(10)
2572.4(2)
2
1.683
4.242
1266
0.34 × 0.18 × 0.02
1.34-30.62
38565
R (deg)
ꢀ (deg)
γ (deg)
volume (Å3)
Z
density (calcd; mg/m3)
µ (mm-1
F(000)
)
crystal size (mm3)
θ range for collection (deg)
no. of reflns collected
no. of indep reflns
11361
10198
11009
7967
15429
completeness to θ max (%)
absorption correction
max and min transmission
GOF on F2
99.7
100.0
none
0.98 and 0.81
0.925
98.1
100.0
none
0.9826 and 0.8115
1.052
97.3
analytical
1.0 and 0.83
1.042
numerical
1.000 and 0.818
0.861
numerical
1.000 and 0.838
1.022
final R1 [I > 2σ(I)] (%)
5.67
7.54
5.67
10.53
5.82
a For all complexes: wavelength ) 0.71073 Å, and refinement method ) full-matrix least-squares on F2.
Figure 4. ORTEP of 6 · 2hexane with hydrogen atoms and solvent
omitted for clarity (50% thermal ellipsoids). Selected bond lengths
(Å) and angles (deg): Ni-B 2.297(4), Ni-C(42) 2.019(3), Ni-C(43)
2.081(3), Ni-P 2.190(1), Ni-S 2.1196(8), B-C(42) 1.543(5),
B-C(36) 1.591(5), B-C(5) 1.618(4), C(42)-C(43) 1.453(4),
C(43)-C(44) 1.412(4), C(44)-C(45) 1.372(5), C(45)-C(46)
1.397(4), C(46)-C(47) 1.439(4), C(42)-C(47) 1.374(4), P · · · B
4.449(7), Ni-cent ) 1.82, P-Ni-S 90.41(3), S-Ni-B 80.87(9),
P-Ni-B 164.04(8), S-Ni-cent 116.3, P-Ni-cent 147.7, ligand
bend 52.19(14) [cent ) centroid of B, C(42) and C(43); ligand
bend ) angle between the planes of the C(4) ring and the C(5)
ring].
Figure 3. ORTEP of 2 · toluene with solvent, hydrogen atoms, and
one orientation of a rotationally disordered CMe3 group omitted
for clarity (50% thermal ellipsoids). Selected bond lengths (Å) and
angles (deg): Pd-B 2.320(5), Pd-C(42) 2.198(4), Pd-C(43)
2.325(4), Pd-P 2.343(1), Pd-S 2.316(1), B-C(42) 1.552(6),
B-C(36) 1.579(7), B-C(5) 1.611(6), C(42)-C(43) 1.421(6),
C(43)-C(44) 1.402(6), C(44)-C(45) 1.366(6), C(45)-C(46)
1.394(7), C(46)-C(47) 1.368(6), C(42)-C(47) 1.432(6), P · · · B
4.605(5), Pd-cent 1.99, P-Pd-S 85.04(4), S-Pd-B 79.67(12),
P-Pd-B 162.02(12), S-Pd-cent 114.2, P-Pd-cent 154.9, ligand
bend 54.48(13) [cent ) centroid of B, C(42) and C(43); ligand
bend ) angle between the planes of the C(4) ring and the C(5)
ring].
sible by reaction of 2 with dvds. Complex 7 has an 11B NMR
chemical shift of 74 ppm (cf. 69 ppm for free TXPB), indicative
of a 3-coordinate borane, and a 31P NMR chemical shift of 23.7
ppm, illustrating maintained phosphine coordination to pal-
TXPB. The structure of 6 is similar to that of 2, as determined
by 31P and 11B NMR spectroscopy (δ 33.9 and 30 ppm,
respectively) and X-ray crystallography (Figure 4, Table 1).
However, while the M-B distance of 2.297(4) Å is similar,
albeit somewhat shorter than that observed in 2 [2.320(5) Å],
the Ni-Cipso, Ni-Cortho, and P · · · B distances of 2.019(3),
2.081(3), and 4.449(7) Å reveal closer approach of the
Cipso-Cortho unit to the metal, relative to boron, leading to a
less symmetrical η3-bonding mode in complex 6. As with 2
and complexes of Ph(3-n)B{C6H4(P-i-Pr2)-o}n (n ) 2-3),32,33,37
the M-B bond distance in 6 is somewhat longer than those
observed in related M-(η1-BR3) complexes of tris(N-alkyli-
mazolyl)borane ligands (2.08-2.11 Å for M ) Ni).30,34
Attempted direct preparation of 2 from the reaction of
[Pd2(dvds)3] (dvds ) 1,3-divinyltetramethyldisiloxane) with
TXPB resulted in rapid formation of a new product; [(κ1-
TXPB)Pd(η2:η2-dvds)] (7). This same product was also acces-
1
ladium. The H NMR spectrum of 7 is consistent with a Cs
symmetric compound at temperatures between 40 and -80 °C
(equivalent vinyl groups of the dvds ligand, but inequivalent
methyl groups on silicon), although some dissociation of dvds
to reform complex 2 (up to 5% at 40 °C; slow on the NMR
time scale) is observed in toluene-d8 at temperatures above -40
°C. X-ray quality crystals of 7 · 2hexane were grown from
hexane at -30 °C and confirm a structure in which palladium
is approximately trigonal planar as a result of η2:η2-coordination
to dvds and bonding only to the phosphine group of TXPB
(Figure 5, Table 1; despite a high R factor, the structure of
7 · 2hexane is suitable to establish connectivity and geometry).
The geometry at boron is trigonal planar, and the thioxanthene

5322 Organometallics, Vol. 27, No. 20, 2008
Emslie et al.
Scheme 3. Preparation and Complexation of Thioxantphos
Figure 5. ORTEP of 7 · 2hexane with hydrogen atoms and solvent
omitted for clarity (50% thermal ellipsoids). Selected bond lengths
(Å) and angles (deg): Pd-P 2.308(3), Pd-C(24) 2.180(12),
Pd-C(25) 2.171(11), Pd-C(26) 2.148(11), Pd-C(27) 2.188(12),
P · · · B 5.273(12), C(5)-B-C(61) 119.6(9), C(5)-B-C(71) 118.6(10),
C(61)-B-C(71) 121.8(9), P-Pd-X 113.47, P-Pd-Y 114.55,
X-Pd-Y 131.66, ligand bend 45.85(36) [X ) centroid of C(24)/
C(25); Y ) centroid of C(26)/C(27); ligand bend ) angle between
the planes of the C(4) ring and the C(5) ring].
antphos; 31P δ -10 ppm).48 This ligand was accessible in 67%
yield by dilithiation of TXBr2 followed by reaction with 2 equiv
of ClPPh2 (Scheme 3), and is the sulfur analogue of the popular
Xantphos ligand pioneered by van Leeuwen et al.
Reaction of Thioxantphos with [PtX2(COD)] (X ) Cl and I)
resulted in the clean formation of [PtX(Thioxantphos)]X [X )
Cl (9) and I (10); Scheme 3] with very similar 1H and 13C NMR
spectra and 31P NMR chemical shifts of 41 ppm (1JP,Pt 2429
Hz) and 39 ppm (1JP,Pt 2383 Hz), respectively.49 Observation
of a single 31P NMR signal for 9 and 10, inequivalent CMe2
groups, and insolubility in toluene indicate symmetrical binding
of Thioxantphos via both phosphine donors, a bent ligand
backbone, and iodide displacement by the thioether donor of
Thioxantphos. The solid-state structure of complex 10 (Figure
6; Table 1) confirms that the Thioxantphos ligand is κ3-
coordinated to form a square-planar platinum cation with an
iodide counteranion50,51 and that the thioxanthene backbone of
the ligand adopts a butterfly conformation, as is observed for
complexes of TXPB. The Pt-S bond distance in 10 is 2.252(2)
Å, while the Pt-P bond lengths are 2.318(2) and 2.310(2) Å.52
These bonds are slightly shorter than Pd-S and Pd-P in
complex 2 [2.316(1) and 2.343(1) Å respectively], perhaps due
to the cationic nature of 10. The κ3-coordination mode observed
backbone of TXPB adopts the characteristic butterfly structure
observed in complexes 1-6.
The platinum analogue of complex 7, [(κ1-TXPB)Pt(η2:η2-
dvds)] (8), was also prepared by reaction of [Pt(COD)2] with
dvds, followed by TXPB.45 The 1H and 13C NMR spectra of 8
are extremely similar to those of 7, except that no dvds
dissociation is observed, and the vinyl protons and carbon atoms
show 195Pt satellites and are shifted to lower frequency.46 The
31P NMR signal for 8 is located at 21.1 ppm (1JPt,P 3661 Hz),
and the 11B chemical shift for complex 8 is identical to that of
7 (74 ppm).
The observation of M-{η3(BCC)-BAr3} bonding in 1, 2, and
6 lies in stark contrast to the M-(η1-BAr3) bonding mode
observed in the arylborane complexes [{(κ3-L)Rh(µ-Cl)}2], cis-
[(κ3-L)RhCl(DMAP)],37 trans-[(κ3-L)RhCl(CO)], cis-[(κ3-L)-
MCl2] (M ) Pd or Pt),32 [(κ3-L)AuCl],9 and [(κ2-L′)AuCl]38
(L ) PhB{C6H4(PR2)-o}2; R ) i-Pr or Ph; L′ ) FluB{C6H4-
(P-i-Pr2)-o}; FluB ) borafluorenyl) reported recently by Bour-
issou et al. Analogous M-{η3(BCC)-BAr3} bonding should be
sterically accessible with these ligands, bearing in mind that
M-(η3-BAr3) bonding in 1, 2, and 6 is characterized by
approximate trigonal planarity at boron.47 Therefore, so long
as the coordination environment of the TXPB ligand does not
in fact preclude M-(η1-BAr3) bonding on steric grounds, the
preference for η3-bonding in our system can reasonably be
attributed to complexation with more electron rich and coor-
dinatively unsaturated (with respect to typical coordination
numbers for a given d-electron configuration) metal fragments.
To assess the potential for a ligand with the same structural
characteristics as TXPB to coordinate via three η1-interactions,
we prepared the phosphine analogue of TXPB; 2,7-di-tert-butyl-
4,5-bis(diphenylphosphino)-9,9-dimethylthioxanthene (Thiox-
(48) The coordination behavior of a t-Bu-free version of Thioxantphos
is mentioned in the following paper: Zuideveld, M. A.; Swennenhuis,
B. H. G.; Boele, M. D. K.; Guari, Y.; van Strijdonck, G. P. F.; Reek, J. N. H.;
Kamer, P. C. J.; Goubitz, K.; Fraanje, J.; Lutz, M.; Spek, A. L.; van
Leeuwen, P. W. N. M Dalton Trans. 2002, 2308. However, to the best of
our knowledge, a preparation for this ligand has not been published, and it
has not been mentioned in any subsequent publications.
1
(49) The magnitudes of J195Pt,31P coupling constants in square planar
platinum(II) complexes are known to be very sensitive to the nature of the
ligand in the trans position and the overall charge on the complex. See, for
example: (a) Pidcock, A.; Richards, R. E.; Venanzi, L. M. J. Chem. Soc. A
1966, 1707. (b) Krevor, J. V. Z.; Simonis, U.; Richter, J. A. Inorg. Chem.
1992, 31, 2409.
(50) The ionic nature of 9 and 10 is consistent with their insolubility in
toluene.
(51) For discussion of analogous platinum complexes of the
S(CH2CH2PPh2)2 ligand, see: (a) Andreasen, L. V.; Simonsen, O.; Wernberg,
O Inorg. Chim. Acta 1999, 295, 153. For other d8 metal complexes of PSP
ligands, see: (b) Morohashi, N.; Akahira, Y.; Tanaka, S.; Nishiyama, K.;
Kajiwara, T.; Hattori, T. Chem. Lett. 2008, 37, 418.
(52) Xantphos-type ligands are typically cis κ2(PP)-coordinated with
the xanthene backbone adopting a butterfly conformation: (a) Kamer,
P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Acc. Chem. Res. 2001,
34, 895. However, an approximately planar xanthene backbone has been
observed in complexes where κ3(POP)-coordination is favored: (b) Refer-
ence 48. (c) Sandee, A. J.; van der Veen, L. A.; Reek, J. N. H.; Kamer,
P. C. J.; Lutz, M.; Spek, A. L.; van Leeuwen, P. W. N. M. Angew. Chem.,
Int. Ed. 1999, 38, 3231. (d) Nieczypor, P.; van Leeuwen, P. W. N. M.;
Mol, J. C.; Lutz, M.; Spek, A. L. J. Organomet. Chem. 2001, 625, 58.
(45) [Pt(nb)3] and [Pt(COD)2] react with TXPB to form a mixture of
products.
(46) Krause, J.; Cestaric, G.; Haack, K.-J.; Seevogel, K.; Storm, W.;
Po¨rschke, K.-R. J. Am. Chem. Soc. 1999, 121, 9807.
(47) The complexes [(κ4-L)Pt] and [(κ4-L)AuCl] (L ) B{C6H4(P-i-Pr2)-
o}3) have also been reported. However, for these complexes, metal-aryl
interactions are precluded by κ4-bonding which aligns all B-aryl rings
approximately side-on with respect to the metal; see ref 33.

InVestigations into η3(BCC)-Triarylborane Coordination
Organometallics, Vol. 27, No. 20, 2008 5323
conical centrifuge tubes was used to remove insoluble byproduct
or to collect precipitated products. Residual oxygen and moisture
were removed from the argon stream by passage through an
Oxisorb-W scrubber from Matheson Gas Products. Anhydrous dme
(1,2-dimethoxyethane) and CH2Cl2 were purchased from Aldrich.
Hexanes and toluene were initially dried and distilled at atmospheric
pressure from CaH2 and sodium, respectively. Unless otherwise
noted, all proteo solvents were stored over an appropriate drying
agent (dme, toluene ) Na/Ph2CO; hexanes ) Na/Ph2CO/tetraglyme;
CH2Cl2 ) CaH2) and introduced to reactions via vacuum transfer
with condensation at -78 °C. Deuterated solvents (ACP Chemicals)
were dried over CaH2 (CD2Cl2, C6D5Br) or Na/Ph2CO (C6D6,
THF-d8).
Figure 6. ORTEP of 10 · 1.74CH2Cl2 with hydrogen atoms and
solvent omitted for clarity (50% thermal ellipsoids). Selected bond
lengths (Å) and angles (deg): Pt-P(1) 2.318(2), Pt-P(2) 2.310(2),
Pt-S 2.252(2), Pt-I(1) 2.5824(6), Pt · · · I(2) 8.533(1), I(1) · · · I(2)
7.806(1), P(1) · · · P(2) 4.591(3), P(1)-Pt-S 83.75(6), P(2)-Pt-S
84.16(6), P(2)-Pt-I(1) 96.03(5), P1-Pt-I(1) 96.62(5), P(1)-Pt-
P(2) 165.38(6), S-Pt-I(1) 175.95(4), ligand bend 46.96(24) [ligand
bend ) angle between the planes of the C4 ring and the C5 ring].
[PdCl2(COD)], [PtCl2(COD)], [PtI2(COD)], [Ni(COD)2], [Co-
Co2], and Mg powder (325 mesh, 99%) were purchased from Strem
Chemicals. [Pd2(dba)3], Ph2PCl, 1,3-divinyltetramethyldisiloxane
(dvds), trans,trans-dibenzylideneacetone (dba), Zn powder, LiNEt2,
and LiN(SiMe3)2 were purchased from Sigma-Aldrich. Prior to use,
[CoCp2] was sublimed, and Ph2PCl, COD, COT, and dvds were
distilled from molecular sieves. The compounds TXBr2,39 TXPB,39
[Pd2(dvds)3],46 [Pt(nb)3],55 and [Pt(COD)2]55 were prepared ac-
cording to the literature procedures. Note that in the literature
preparation of [Pt(nb)3], we found that 4-5 times the reported
amount of OEt2 was required to solubilize the Li2[COT] reagent.
NMR spectroscopy (1H, 13C{1H}, 11B, 31P, DEPT-135, COSY,
HSQC, HMBC) was performed on Bruker DRX-500 and AV-600
spectrometers. All 1H NMR and 13C NMR spectra were referenced
relative to SiMe4 through a resonance of the employed deuterated
solvent or proteo impurity of the solvent; C6D6 (δ 7.15 ppm),
C6D5Br (δ 7.30, 7.02, 6.94 ppm), THF-d8 (3.58, 1.73 ppm), and
CD2Cl2 (5.32 ppm) for 1H NMR and C6D6 (δ 128.0 ppm), C6D5Br
(δ130.9, 129.3, 126.1, 122.3 ppm), THF-d8 (67.57, 25.37 ppm),
and CD2Cl2 (54.0 ppm) for 13C NMR. 11B and 31P NMR spectra
were referenced using an external standard of BF3(OEt2) (0.0 ppm)
and 85% H3PO4 in D2O (0.0 ppm), respectively. Electrochemical
studies were carried out using an PAR (Princeton Applied Research)
Model 283 potentiostat (using PAR PowerCV software) in conjunc-
tion with a three-electrode cell under an argon atmosphere. The
auxiliary electrode was a platinum wire, the pseudoreference
electrode a silver wire, and the working electrode a platinum disk
(1.6 mm diameter, Bioanalytical Systems). Solutions were 1 × 10-3
M in test compound and 0.1 M in [N-n-Bu4][PF6] as the supporting
electrolyte. Under these conditions, values of E1/2 (vs SCE) for the
internal calibrant [CoCp2][PF6] are -0.90 and -2.04 V in THF.56
Combustion elemental analyses were performed on a Thermo
EA1112 CHNS/O analyzer by Dr. Steve Kornic of this department.
X-ray crystallographic analyses were performed on suitable crystals
coated in Paratone oil and mounted on either (a) a P4 diffractometer
with a Bruker Mo rotating-anode generator and a SMART1K CCD
area detector or (b) a SMART APEX II diffractometer with a 3
kW Sealed tube Mo generator in the McMaster Analytical X-Ray
(MAX) Diffraction Facility. One of the two molecules of hexane
in 7 · 2hexane, and both molecules of hexane in 6 · 2hexane, were
highly disordered and could not be modeled satisfactorily, so were
treated using the SQUEEZE routine.57 Herein, numbered proton
and carbon atoms refer to the positions of the xanthene backbone
in the TXPB or TXP2 ligands (see Schemes 1 and 3).
for complexes 9 and 10 confirms the steric accessibility of more
traditional κ3-coordination in 4,5-disubstituted thioxanthene
ligands such as Thioxantphos and TXPB [involving a M-(η1-
BR3) interaction in the case of TXPB], providing further
evidence of an electronic origin for the observed M-{η3(BCC)-
BAr3} interactions.
In summary, palladium (2) and nickel (6) complexes contain-
ing unambiguous examples of an η3-bound arylborane were
prepared, either by direct reaction of a zero-valent precursor
with TXPB (in the case of nickel) or by stepwise reduction from
a square planar dihalide complex (in the case of palladium).
The short M-B bond lengths observed in 2 and 6, combined
with previously reported DFT calculations on a related rhodium
complex (1), strongly suggest an electronic origin for the unusual
η3-arylborane coordination mode. This is further supported by
observation of κ3-coordination in platinum(II) Thioxantphos (the
phosphorus-analogue of TXPB) complexes (9 and 10), which
highlight the steric accessibility of bonding via three η1-
interactions in complexes of 4,5-disubstituted thioxanthene
ligands such as TXPB. However, formation of η1-coordinated
arylborane complexes by reaction of [M(TXPB)] with dvds was
prevented by facile displacement of the sulfur donor in the
backbone of the TXPB ligand to form [(κ1-TXPB)M(η2:η2-
dvds)] {M ) Pd (7) and M ) Pt (8)}. Future work will focus
on the oxidative addition reactivity of complexes 2 and 6-8
and their potential in C-C bond-forming catalysis.
Experimental Section
General Details. An argon-filled MBraun UNIlab glovebox
equipped with a -30 °C freezer was employed for the manipulation
and storage of all ligands and complexes,53 and reactions were
performed on a double-manifold high vacuum line using standard
techniques.54 Commonly utilized specialty glassware includes the
swivel frit assembly, J-Young NMR tubes, and thick-walled flasks
equipped with Teflon stopcocks. A Fisher Scientific Ultrasonic FS-
30 bath was used to sonicate reaction mixtures where indicated,
and in some cases, a Fischer Scientific Model 228 centrific
centrifuge in combination with airtight Kimble-Kontes 15 mL
[PdCl2(TXPB)] (3). A solution of [PdCl2(COD)] (125 mg, 4.37
× 10-4 mol) and TXPB (300 mg, 4.37 × 10-4 mol) in CH2Cl2
(15 mL) was stirred at room temperature for 1 h. The resulting
brown-orange solution was evaporated to dryness in vacuo leaving
an oily orange solid to which hexanes (20 mL) was added. After
sonication for 1 h, the mixture was filtered to give an orange solid
(53) Degree of air sensitivity: Thioxantphos, 9 and 10 ) low; TXPB,
3-5, 7 and 8 ) moderate; 1, 2 and 6 ) high.
(54) Burger, B. J.; Bercaw, J. E., Vacuum Line Techniques for Handling
Air-Sensitive Organometallic Compounds. In Experimental Organometallic
Chemistry-A Practicum in Synthesis and Characterization; American
Chemical Society: Washington D.C., 1987; Vol. 357, p 79.
(55) Crascall, L. E.; Spencer, J. L. Inorg. Synth. 1990, 28, 126.
(56) Bard, A. J.; Garcia, E.; Kukharenko, S.; Strelets, V. V. Inorg. Chem.
1993, 32, 3528.
(57) Sluis, P. V. D.; Spek, A. L. Acta Crystallogr. 1990, A46, 194.

5324 Organometallics, Vol. 27, No. 20, 2008
Emslie et al.
which was washed with hexanes (×2) and dried in vacuo. Yield )
s, ipso-BPh2 B), 145.33 (d, J 6 Hz, C10), 143.38 (s, C13), 142.16
(d, J 15 Hz, C12), 140.19 (d, J 44 Hz, C11), 138.21 (d, J 38 Hz,
C4), 135.60 (s, o-BPh2 B), 135.52 (d, J 40 Hz, ipso-PPh2 A and
B), 134.86 (s, m(2)-BPh2 A), 134.56 (d, J 19 Hz, o-PPh2 A), 133.65
(d, J 16 Hz, o-PPh2 B), 132.50 (s, o(5)-BPh2 A), 130.68 (s, p-PPh2
A), 130.38 (s, p-PPh2 B), 129.94 (d, CH3), 129.9 (d, m-PPh2 B),
128.93 (d, J 10 Hz, m-PPh2 A), 128.57 (s, p(3)-BPh2 A), 128.38
(s, p-BPh2 B), 127.68 (s, m-BPh2 B), 127.44 (s, CH6), 125.30 (d,
J 9 Hz, m(4)-BPh2 A), 124.61 (s, CH1), 120.41 (s, CH8), 115.63
(broad s, ipso-BPh2 A), 101.05 (s, o(1)-BPh2 A), 43.43 (s, CMe2),
35.86, 35.70 (2 × s, CMe3), 32.24, 31.49 (2 × s, CMe3), 26.35,
25.94 (2 × s, CMe2).58 31P{1H} (C6D6): δ 17.99 (s). 11B (C6D6):
δ 31 (broad s).59 Anal. Calcd for C47H48PSBPd: C, 71.17; H, 6.10.
Found: C, 70.53; H, 6.47.
1
o
328 mg (87%). H NMR (C6D5Br, 70 C): δ 7.72 (broad s, 1H,
CH1), 7.60 (d, J 8 Hz, 4H, o-BPh2), 7.59 (broad s, 1H, CH8), 7.50
(v broad s, 4H, o-PPh2), 7.47 (broad s, 1H, CH6), 7.22 (t, J 7 Hz,
2H, p-PPh2), 7.14-7.08 (m, 9H, CH3 and m-PPh2 and m-BPh2),
7.06 (d, J 7 Hz, 2H, p-BPh2), 1.69 (broad s, 6H, CMe2), 1.15 (s,
9H, C7CMe3), 1.07 (s, 9H, C2CMe3). 13C{1H} NMR (C6D5Br, 70
oC): δ 153.90 (s, C2CMe3), 151.9 (broad s, C5), 150.8 (broad s,
ipso-BPh2), 150.61 (s, C7CMe3), 145.75 (d, J 14 Hz, C10), 139.55
(s, C13), 136.02 (d, J 19 Hz, C11), 135.00 (s, o-BPh2), 133.89 (s,
CH6), 133.85 (d, J 12 Hz, o-PPh2), 132.11 (s, p-PPh2), 128.73 (s,
CH3), 128.67 (d, J 13 Hz, m-PPh2), 127.38 (d, J 62 Hz, C4 or
ipso-PPh2), 126.82 (s, m-BPh2), 126.68 (s, C12), 126.07 (s, CH1),
125.80 (s, p-BPh2), 120.08 (s, CH8), 42.14 (s, CMe2), 34.87 (s, 2
× C2CMe3), 34.70 (s, 2 × C7CMe3), 31.08 (s, C7CMe3), 30.80 (s,
C2CMe3), 26.85 (broad s, CMe2). 31P{1H} (CD2Cl2): δ 58.42 (s).
11B (CD2Cl2): δ 12.9 (broad s). Anal. Calcd for C47H48PSBCl2Pd:
C, 65.33; H, 5.60. Found: C, 65.33; H, 5.57.
[Ni(TXPB)] · 0.5hexane (6). A mixture of [Ni(COD)2] (40 mg,
1.46 × 10-4 mol) and TXPB (100 mg, 1.46 × 10-4 mol) in toluene
(5 mL) was stirred for 2 h at room temperature. The resulting dark
red-orange solution was then evaporated to dryness, sonicated in
hexanes (5 mL), and filtered to collect a brick red solid which was
washed with hexanes (×2) and dried in vacuuo. Yield 80 mg (70%).
In several instances, this product contained an impurity with 31P
NMR δ 42 ppm. However, this impurity could be removed by
crystallization from dme/hexanes at -30 °C. X-ray quality crystals
[{PdCl(TXPB)}2] (4). A solution of [Pd(dba)(TXPB)] · CH2Cl2
(5) (80 mg, 7.19 × 10-5 mol) and [PdCl2(TXPB)] (3) (62 mg,
7.19 × 10-5 mol) in CH2Cl2 (4 mL) was heated in a sealed flask
at 50 °C for 2 days. The resulting bright red solution was then
layered with hexanes and cooled to -30 °C. After several days,
the orange-brown mother liquors were decanted to leave red crystals
which were dried in vacuo. Yield ) 60 mg (50%). X-ray quality
crystals of 4 · hexane were grown from CH2Cl2/hexane at -30 °C.
1H NMR (CD2Cl2): δ 7.81 (dd, J 12, 8 Hz, 2H, o-PPh2 B), 7.58 (s,
1H, CH1), 7.53 (d, J 2 Hz, 1H, CH8), 7.51 (td, J 7, 2 Hz, 1H,
p-PPh2 A), 7.40 (app td, J 7, 2 Hz, 2H, m-PPh2 A), 7.2-7.1 (m,
10H, BPh2), 7.15 (s, 1H, CH3), 7.12 (d, J 2 Hz, CH6), 7.07 (dd, J
12, 8 Hz, 2H, o-PPh2 B), 6.45 (t, J 7 Hz, 1H, p-PPh2 B), 5.95 (t,
J 6 Hz, 2H, m-PPh2 B), 2.05 (s, 3H, CMe2), 1.25 (s, 9H, C2CMe3),
1.23 (s, 9H, C7CMe3), 0.99 (s, 3H, CMe2). 13C{1H} NMR (CD2Cl2):
δ 153.24, 152.84 (broad s, 2 × ipso-BPh2), 151.10 (s, C2CMe3),
150.08 (broad s, C5), 149.24 (s, C7CMe3), 144.72 (d, J 11 Hz, C10),
140.20 (s, C13), 136.71 (d, J 20 Hz, C11), 136.29 (d, J 14 Hz, o-PPh2
A), 135.17 (d, J 47 Hz, C4), 134.87, 134.72, 127.56, 125.76, 125.47
(5 × s, BPh2), 133.43 (s, CH6), 133.04 (d, J 9 Hz, o-PPh2 B),
131.62 (s, p-PPh2 A), 131.45 (d, J 55 Hz, ipso-PPh2), 130.86 (d, J
57 Hz, ipso-PPh2), 129.31 (s, C12), 129.15 (s, p-PPh2 B), 129.01
(d, 11 Hz, m-PPh2 A), 127.2 (CH3), 127.02 (s, m-PPh2 B), 123.84
(s, CH1), 120.08 (s, CH8), 41.58 (s, CMe2), 35.59 (s, C2CMe3),
35.32 (s, C7CMe3), 31.76 (s, C7CMe3), 31.52 (s, C2CMe3), 28.40,
25.76 (s, CMe2). 31P{1H} (CD2Cl2): δ 36.47 (s). 11B (CD2Cl2): δ
2 (broad s). Anal. Calcd for C94H96P2S2B2Cl2Pd2: C, 68.13; H, 5.84.
Found: C, 67.94; H, 5.96.
[Pd(TXPB)] (2). A mixture of [PdCl2(TXPB)] (3; 200 mg, 2.31
× 10-4 mol) and Mg powder (100 mg, 4.17 mmol) in THF (10
mL) was sonicated for 30 min at room temperature and then stirred
vigorously for 10 min, resulting in a color change from bright
orange-yellow to orange-red. This process was then repeated
resulting in a color change to deep red, and then to yellow-brown.
The mixture was then evaporated to dryness in vacuo, dissolved in
hexanes (5 mL) and filtered through a short column of celite. The
supernatant was evaporated to dryness to yield 2 as a yellow-brown
powder (yield 116 mg, 63%). X-ray quality crystals of 2 · toluene
were grown from toluene at -30 °C. 1H NMR (THF-d8, -30 °C):
δ 7.63 (app t, J 7 Hz, 1H, m(2)-BPh2 A), 7.58 (s, 1H, CH1), 7.49
(s, 1H, CH8), 7.48 (m, 2H, o-BPh2 B), 7.42 (s, 1H, CH6), 7.37 (m,
10H, PPh2 B), 7.29 (t, J 7 Hz, 1H, p-PPh2 A), 7.22 (t, J 7 Hz, 2H,
m-PPh2 A), 7.13 (d, J 7 Hz, 1H, p-BPh2 B), 7.12 (t, J 7 Hz, 2H,
m-BPh2 B), 7.04 (t, J 7 Hz, 1H, p(3)-BPh2 A), 7.03 (app t, J 7 Hz,
1H, m(4)-BPh2 A), 6.83 (d, J 6 Hz, 1H, CH3), 6.62 (d, J 7 Hz, 1H,
o(1)-BPh2 A), 6.53 (d, J 7 Hz, 1H, o(5)-BPh2 A), 6.45 (dd, J 11,
7 Hz, 2H, o-PPh2), 2.09, 1.71 (s, 2 × 3H, CMe2), 1.37, 1.05 (s, 2
× 9H, CMe3).58 13C{1H} NMR (THF-d8, -30 °C): δ 151.34 (s,
C7CMe3), 151.27 (broad s, C5), 151.07 (s, C2CMe3), 147.49 (broad
1
of 6 · 2hexane were also grown from dme/hexane at -30 °C. H
NMR (THF-d8, -30 °C): δ 7.65 (m, 2H, o-PPh2 A), 7.57 (s, 1H,
CH1), 7.48 (s, 1H, CH8), 7.46 (s, 1H, CH6), 7.44 (m, 3H, m- and
p-PPh2 A), 7.41 (d, J 7 Hz, 2H, o-BPh2 B), 7.26 (app t, J 7 Hz,
1H, m(2)-BPh2 A), 7.25 (t, J 7 Hz, 1H, p-PPh2 B), 7.20 (app t, J
7 Hz, 2H, m-PPh2 B), 7.09 (t, J 7 Hz, 1H, p-BPh2 B), 7.07 (app t,
J 7 Hz, 2H, m-BPh2 B), 6.94 (d, J 6 Hz, 1H, CH3), 6.63 (app t, J
7 Hz, 1H, m(4)-BPh2 A), 6.44 (dd, J 10, 7 Hz, 2H, o-PPh2 B),
6.30 (d, J 7 Hz, 1H, o(5)-BPh2 A), 6.26 (t, J 7 Hz, 1H, p(3)-BPh2
A), 5.68 (d, J 7 Hz, 1H, o(1)-BPh2 A), 2.07, 1.62 (s, 2 × 3H,
CMe2), 1.37, 1.12 (s, 2 × 9H, CMe3).58 13C{1H} NMR (THF-d8,
-30 °C): δ 152.11 (broad s, C5), 151.39, 151.24 (s, C2CMe3,
C7CMe3), 148.59 (broad s, ipso-BPh2 B), 144.26 (d, J 8 Hz, C10),
142.50 (d, J 37 Hz, C11), 142.11 (s, C13), 141.90 (d, J 15 Hz, C12),
138.61 (d, J 43 Hz, C4), 137.54 (s, m(2)-BPh2 A), 135.07 (s, o-BPh2
B), 134.64 (d, J 16 Hz, o-PPh2 A), 133.93 (d, J 32 Hz, ipso-PPh2
A), 133.63 (d, J 14 Hz, o-PPh2 B), 131.46 (d, J 31 Hz, ipso-PPh2
B), 131.16 (s, p-PPh2 A), 130.58 (s, o(5)-BPh2 A), 130.10 (d, J 9
Hz, m-PPh2 A), 129.92 (s, p-PPh2 B), 129.76 (d, J 9 Hz, m(4)-
BPh2 A), 128.8 (d, CH3), 128.7 (d, m-PPh2 B), 128.37 (s, m-BPh2
B), 127.10 (s, p-BPh2 B), 126.91 (s, CH8), 124.74 s, CH1), 123.70
(s, p(3)-BPh2 A), 120.47 (s, CH6), 105.36 (broad s, ipso-BPh2 A),
91.37 (s, o(1)-BPh2 A), 42.94 (s, CMe2), 35.94, 35.80 (2 × s,
CMe3), 32.34, 31.59 (2 × s, CMe3), 27.06, 25.00 (2 × s, CMe2).58
31P{1H} (C6D6): δ 33.86 (s). 11B (C6D6): δ 30 (broad s).59 Anal.
Calcd for C50H55PSBNi: C, 76.16; H, 7.03. Found: C, 75.89; H,
7.31.
[(K1-TXPB)Pd(η2:η2-dvds)] (7). A solution of TXPB (100 mg,
1.46 × 10-4 mol) in hexanes (0.8 mL) was added to a solution of
[Pd2(dvds)3] (56 mg, 7.25 × 10-5 mol) in hexanes (0.7 mL)
followed by stirring for 5 min before filtration through a short (0.3
× 1 cm) plug of Celite and elution with hexanes (2 × 0.5 mL).
The resulting orange-brown solution was cooled to -30 °C to yield
a beige-yellow semicrystalline solid. The mother liquors were
removed from the solid at -30 °C before warming to room
temperature, at which point the solid partially dissolved as a result
of liberated lattice solvent. The resulting yellow-orange mixture
was dried in vacuo to yield 7 as a beige solid. Yield ) 112 mg
(79%). X-ray quality crystals of 7 · hexane were grown from hexane
(58) The metal-coordinated B-phenyl ring is labeled A and is numbered
to indicate the position of each carbon and proton relative to the coordinated
ortho position. For example, the coordinated ortho position is labeled “o(1)-
BPh2 A”, while the adjacent meta position is labeled “m(2)-BPh2 A”.
(59) Complex 2 (THF-d8): 31P δ 19.12 ppm (s), 11B δ 30 ppm (broad
s). Complex 6 (THF-d8): 31P δ 34.37 ppm (s), 11B δ 28 ppm (broad s).

InVestigations into η3(BCC)-Triarylborane Coordination
Organometallics, Vol. 27, No. 20, 2008 5325
at -30 °C and mounted without warming above -20 °C to prevent
(CD2Cl2): δ 149.62 (s, C2CMe3), 143.22 (s, C10), 137.50 (d, J 12
Hz, ipso-PPh2), 136.31 (d, J 9 Hz, C4), 136.13 (d, J 10 Hz, C11),
134.58 (d, J 20 Hz, ortho-PPh2), 129.1 (d, m-PPh2), 129.0 (s,
p-PPh2), 128.78 (s, CH3), 122.44 (s, CH1), 41.71 (s, CMe2), 35.31
(s, CMe3), 31.52 (s, CMe3), 25.34 (s, CMe2). 31P{1H} (CD2Cl2): δ
-10.01 (s). Anal. Calcd for C47H48P2S: C, 79.86; H, 6.84. Found:
C, 79.57; H, 6.59.
1
solvent loss. H NMR (C6D6): δ 7.73 (s, 1H, CH8), 7.70 (s, 1H,
CH1), 7.63 (d, J 7 Hz, 4H, o-BPh2), 7.48 (m, 4H, o-PPh2), 7.29 (t,
J 7 Hz, 2H, p-BPh2), 7.28 (s, 1H, CH6), 7.21 (app t, J 7 Hz, 4H,
m-BPh2), 7.16 (d, 1H, CH3), 6.90 (m, 6H, m- and p-PPh2), 3.36
(dd, 3JH,H 16 Hz, 3JH,P 5 Hz, 2H, CHdCH2), 3.32 (dd, 3JH,H 12 Hz,
3JH,P 6 Hz, 2H, CHdCH2), 3.08 (ddd, 3JH,H 16, 12 Hz, 3JH,P 5 Hz,
2H, CHdCH2), 1.82 (s, 6H, CMe2), 1.21 (s, 9H, C7CMe3), 1.17 (s,
9H, C2CMe3), 0.48, -0.05 (s, 2 × 6H, SiMe2). 13C{1H} NMR
(C6D6): δ 148.47 (s, C2CMe3), 148.23 (s, C7CMe3), 144.38 (broad
s, C5), 143.22 (s, C10), 142.53 (broad s, ipso-BPh2), 141.88 (s, C13),
139.13 (s, o-BPh2), 136.48 (d, J 17 Hz, C11), 136.28 (d, J 28 Hz,
ipso-PPh2), 135.77 (d, J 30 Hz, C4), 135.20 (s, C12), 134.57 (d, J
15 Hz, o-PPh2), 132.15 (s, p-BPh2), 130.30 (s, CH6), 129.35 (s,
p-PPh2), 128.29 (d, J 9 Hz, m-PPh2), 127.93 (s, m-BPh2), 126.99
(s, CH3), 122.32 (s, CH8), 121.86 (s, CH1), 69.64 (s, CHdCH2),
[PtCl2(TXP2)] · CH2Cl2 (9). A solution of [PtCl2(COD)] (132
mg, 3.54 × 10-4 mol) and TXP2 (250 mg, 3.54 × 10-4 mol) in
CH2Cl2 (25 mL) was stirred at room temperature for 1 h. The
resulting pale yellow solution was evaporated to lower volume (10
mL) in vacuo, and hexanes (15 mL) was added. The mixture was
then filtered to collect a white solid which was washed with hexanes
and dried in vacuo. Yield ) 245 mg (66%). 1H NMR (CD2Cl2): δ
7.86 (app quart., J 7 Hz, 4H, o-PPh2 A), 7.85 (m, 2H, CH1), 7.73
(app t, J 7 Hz, 2H, p-PPh2 A), 7.69 (app t, J 8 Hz, 4H, m-PPh2 A),
7.61 (app t, J 8 Hz, 2H, p-PPh2 B), 7.50 (app t, J 7 Hz, 4H, m-PPh2
B), 7.41 (app quart, J 7 Hz, 4H, o-PPh2 B), 7.37 (app td, J 5, 1.6
Hz, 2H, CH3), 2.22, 1.56 (s, 2 × 3H, CMe2), 1.28 (s, 18H, CMe3).
13C{1H} NMR (CD2Cl2): δ 157.41 (s, C2CMe3), 144.66 (s, C10),
134.48 (app t, J 15 Hz, C11), 134.22 (app t, J 6 Hz, o-PPh2 B),
134.03 (app t, J 7 Hz, o-PPh2 A), 133.80 (s, p-PPh2 A), 133.54 (s,
p-PPh2 B), 132.79 (app t, J 29 Hz, C4), 131.23 (s, CH3), 130.66
(app t, J 5 Hz, m-PPh2 A), 129.73 (app t, J 5 Hz, m-PPh2 B), 128.06
(s, CH1), 126.74 (app t, J 29 Hz, ipso-PPh2 A), 125.27 (app t, J 32
Hz, ipso-PPh2 B), 44.00 (s, CMe2), 36.11 (s, CMe3), 31.39 (s,
CMe3), 28.30, 24.91 (s, CMe2). 31P{1H} (CD2Cl2): δ 41.46 (s,
1J31P,195Pt 2429 Hz). Anal. Calcd for C48H50P2SCl4Pt: C, 54.50; H,
4.76. Found: C, 54.80; H, 4.64.
2
67.98 (d, JC,P 7 Hz, CHdCH2), 41.21 (s, CMe2), 35.02 (s,
C2CMe3), 34.83 (s, C7CMe3), 31.53 (s, C7CMe3), 31.40 (s,
C2CMe3), 25.33 (s, CMe2), 1.91, -1.05 (2 × s, SiMe2). 31P{1H}
(C6D6): δ 23.8 (s). 11B (C6D6): δ 74 (broad s). Anal. Calcd for
C55H66OPSBSi2Pd: C, 67.44; H, 6.79. Found: C, 67.59; H, 6.99.
[(K1-TXPB)Pt(η2:η2-dvds)] · hexane (8). A solution of dvds (34
mg, 3.13 × 10-4 mol) in hexanes (1 mL) was added to a solution
of [Pt(COD)2] (68 mg, 1.65 × 10-4 mol) in hexanes (1 mL). The
resulting mixture was stirred for 5 min and filtered to give a pale
brown solution, to which a solution of TXPB (113 mg, 1.65 ×
10-4 mol) in hexanes (1 mL) was added. After being stirred for 5
min, the pale brown solution was filtered and cooled to -30 °C to
yield a pale-fawn solid which was dried in vacuo. Yield ) 112 mg
(59%). 1H NMR (C6D6): δ 7.73 (d, J 2 Hz, 1H, CH8), 7.70 (s, 1H,
CH1), 7.63 (d, J 7 Hz, 4H, o-BPh2), 7.49 (m, 4H, o-PPh2), 7.29 (t,
J 7 Hz, 2H, p-BPh2), 7.28 (s, 1H, CH6), 7.24 (d, J 11 Hz, 1H,
CH3), 7.20 (app t, J 7 Hz, 4H, m-BPh2), 6.88 (m, 6H, m- and
[PtI2(TXP2)] · 1.5toluene (10). A mixture of [PtI2(COD)] (70
mg, 1.26 × 10-4 mol) and TXP2 (93 mg, 1.32 × 10-4 mol) in
toluene (4 mL) was stirred at room temperature for 2 h. The
resulting mixture was centrifuged, and the yellow mother liquors
removed to collect a bright yellow powder. Toluene (3 mL) was
again added, and the mixture was stirred and then centrifuged before
removal of the nearly colorless mother liquors. The resulting bright
yellow powder was dried in vacuo. Yield ) 122 mg (72%). X-ray
quality crystals of 4 · 1.74CH2Cl2 were grown from CH2Cl2/hexane
3
3
p-PPh2), 2.49 (dd, JH,H 14 Hz, JH,P 7 Hz, 2H, CHdCH2), 2.49
3
3
3
(dd, JH,H 12 Hz, JH,P 7 Hz, 2H, CHdCH2), 2.49 (ddd, JH,H 14,
12 Hz, 3JH,P 7 Hz, 2H, CHdCH2), 1.80 (s, 6H, CMe2), 1.21 (s, 9H,
C7CMe3), 1.17 (s, 9H, C2CMe3), 0.55, -0.08 (s, 2 × 6H, SiMe2).
13C{1H} NMR (C6D6): δ 148.21 (s, 2 × CCMe3), 144.31 (broad
s, C5), 143.50 (d, J 7 Hz, C10), 142.61 (broad s, ipso-BPh2), 141.94
(s, C13), 139.11 (s, o-BPh2), 136.77 (d, J 12 Hz, C11), 135.23 (d,
J 45 Hz, ipso-PPh2), 135.18 (s, C12), 134.8 (d, C4), 134.49 (d, J
12 Hz, o-PPh2), 132.12 (s, p-BPh2), 130.56 (s, CH6), 129.63 (s,
p-PPh2), 128.08 (d, J 10 Hz, m-PPh2), 127.88 (s, m-BPh2), 127.5
1
at -30 °C. H NMR (CD2Cl2): δ 7.94 (app quart., J 7 Hz, 4H,
o-PPh2 A), 7.85 (s, 2H, CH1), 7.73 (app t, J 7 Hz, 2H, p-PPh2 A),
7.68 (app t, J 7 Hz, 4H, m-PPh2 A), 7.58 (app t, J 7 Hz, 2H, p-PPh2
B), 7.49 (app t, J 7 Hz, 4H, m-PPh2 B), 7.32 (app quart., J 7 Hz,
4H, o-PPh2 B), 7.29 (t, J 5 Hz, 2H, CH3), 2.23, 1.58 (s, 2 × 3H,
CMe2), 1.28 (s, 18H, CMe3). 13C{1H} NMR (CD2Cl2) δ 157.29 (s,
C2CMe3), 144.51 (s, C10), 134.64 (app t, J 7 Hz, o-PPh2 A), 134.38
(app t, J 6 Hz, o-PPh2 B), 134 (C11), 133.82 (s, p-PPh2 A), 133.42
(s, p-PPh2 B), 131.75 (s, CH3), 130.69 (app t, J 5 Hz, m-PPh2 A),
129.38 (app t, J 5 Hz, m-PPh2 B), 127.93 (s, CH1), 127.58 (app t,
J 33 Hz, ipso-PPh2 B), 127.04 (app t, J 29 Hz, ipso-PPh2 B), 44.02
(s, CMe2), 36.15 (s, CMe3), 31.46 (s, CMe3), 28.35, 25.09 (s, CMe2).
31P{1H} (CD2Cl2): δ 38.64 (s, 1J31P,195Pt 2383 Hz). Anal. Calcd for
1
(s, CH3), 122.31 (s, CH1 and CH8), 52.32 (s, JC,Pt 162 Hz,
CHdCH2), 46.56 (d, 2JC,P 11 Hz, 1JC,Pt 117 Hz, CHdCH2), 41.28
(s, CMe2), 35.02 (s, C2CMe3), 34.83 (s, C7CMe3), 31.51 (s,
C7CMe3), 31.36 (s, C2CMe3), 25.24 (s, CMe2), 1.83, -1.63 (2 × s,
SiMe2). 31P{1H} (C6D6): δ 21.1 (s, J
Pt 3361 Hz). 11B (C6D6):
31P,195
δ 74 (broad s). Anal. Calcd for C61H80OPSBSi2Pt: C, 63.14; H,
6.95. Found: C, 63.36; H, 6.43.
2,7-Di-tert-butyl-4,5-bis(diphenylphosphino)-9,9-dimethylthiox-
anthene (TXP2). A 2.0 M solution of n-butyllithium (2.1 mL, 4.13
t
mmol) was added to a solution of Bu2TXBr2 (1.0 g, 2.01 mmol)
C57.5H60P2SI2Pt: C, 53.36; H, 4.67. Found: C, 53.45; H, 4.65.
in toluene (80 mL) at -78 °C. The mixture was then allowed to
warm to room temperature over several hours and stirred for a
further 12 h. After the mixture was cooled to -78 °C, Ph2PCl (0.74
mL, 4.13 mmol) was added, and the solution was allowed to warm
to room temperature, stirred for a further 12 h, filtered, and
evaporated to dryness in vacuo to give a slightly oily white solid.
This was slurried in hexanes (50 mL), sonicated, cooled to -78
°C, and then filtered to collect a white solid which was dried in
vacuo. Yield ) 960 mg (67%). 1H NMR (CD2Cl2): δ 7.54 (d, 4JH,H
1 Hz, 2H, CH1), 7.40-7.30 (m, 20H, PPh2), 6.78 (dd, J ) 4, 1 Hz,
2H, CH3), 1.73 (s, 6H, CMe2), 1.15 (s, 18H, CMe3). 13C{1H} NMR
Acknowledgment. Funding for this work was provided
to D.J.H.E. as a McMaster University Start-Up fund, an
NSERC of Canada Discovery Grant, and CFI and OIT New
Opportunities Grants.
Supporting Information Available: X-ray crystallographic data
in PDF and CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM800670E