A series of pincer-ligated rhodium complexes as catalysts for the dimerization of terminal alkynes

Article abstract of DOI:10.1021/cs5009317

A series of pincer complexes of Rh has been prepared and tested as catalysts for the dimerization of terminal alkynes. The pincers included aryl/bis(phosphinite) POCOP, aryl/bis(phosphine) PCP, and diarylamido/bis(phosphine) PNP ligands. Rh^I co

Full text of DOI:10.1021/cs5009317

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Article
A Series of Pincer-Ligated Rhodium Complexes as
Catalysts for the Dimerization of Terminal Alkynes
Christopher J. Pell, and Oleg V. Ozerov
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/cs5009317 • Publication Date (Web): 22 Aug 2014
Downloaded from http://pubs.acs.org on September 2, 2014
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A Series of PincerꢀLigated Rhodium Complexes as
Catalysts for the Dimerization of Terminal Alkynes
Christopher J. Pell and Oleg V. Ozerov*
Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, TX 77842.
ozerov@chem.tamu.edu
ABSTRACT. A series of pincer complexes of Rh has been prepared and tested as catalysts for the
dimerization of terminal alkynes. The pincers included aryl/bis(phosphinite) POCOP, aryl/bis(phosphine)
PCP, and diarylamido/bis(phosphine) PNP ligands. RhI complexes of the general form (pincer)Rh(SiPr2) or
(pincer)Rh(H2) were used as catalysts. In addition, the apparent donating ability of the pincer ligands was
gauged through the carbonyl stretching frequencies in (pincer)Rh(CO) complexes by IR spectroscopy. All
surveyed Rh complexes acted as catalysts for dimerization of 4ꢀethynyltoluene, 1ꢀhexyne, or
trimethysilylacetylene. The products were a mixture of Eꢀ and gemꢀenyne isomers, with small amounts of
oligomers in some cases. The Zꢀenyne isomers were not observed except in two reactions. None of the
catalysts showed useful selectivity for either the Eꢀ or the gemꢀenyne product. However, the POCOPꢀbased
catalysts bearing PiPr2 donor arms performed faster and possessed apparently greater longevity (up to 20,000
TON) than the previously reported pincer Rh catalysts.
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KEYWORDS. Pincer, alkyne dimerization, rhodium, catalysis, phosphine, enyne
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Introduction
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Alkyne dimerization is a process in which a CspꢀH bond in a terminal alkyne is formally added across
the C≡C bond in another molecule of alkyne. The products of alkyne dimerization, conjugated enynes,
are versatile building blocks for a variety of organic transformations.1 This process is 100% atomꢀ
economical and requires a catalyst.2 The desired role for the catalyst is not limited to enabling a faster
reaction, but formation of the desired product in a selective fashion. In principle, three isomers of a
conjugated enyne arising from dimerization of a terminal alkyne are possible: E, Z, and gem (Scheme
1). In addition, terminal alkynes may undergo dimerization to a butariene,3 cyclotrimerization to arenes,
or oligoꢀ and polymerization to polyenes with various catalysts.4 Catalytic alkyne dimerization has been
investigated using a number of transition metals,5ꢀ12 main group elements,13 and lanthanides.14 While
some of these catalytic systems give mixtures of enyne and oligomeric products, several systems show
excellent selectivity for a specific isomer. A recent NHC palladium (NHC = Nꢀheterocyclic carbene)
catalyst has achieved perfect regioꢀ and stereoselectivity to form the Eꢀenyne with a range of terminal
alkynes possessing various functional groups.10b Palladium has also been used as a selective headꢀtoꢀtail
dimerization catalyst for a range of substituted alkynes when paired with a Brønsted acid.10c Selective
dimerization to form the Zꢀenyne has been primarily the specialty of ruthenium catalysts,7a,b but
lanthanide and zirconium complexes have also shown Zꢀselectivity.12,14
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In the domain of Rhꢀcatalyzed alkyne dimerization, the frontier of cross dimerization is experiencing
advancements. Miura’s group was able to take advantage of sterically different terminal alkynes and a
bulky Rh catalyst to selectively produce Eꢀenynes with a high tolerance for functionalities.11a More
recently, the Xu group showed that a Rh phosphine system could effectively crossꢀdimerize
arylacetylenes with propargylic alcohols, ethers, and amides.11e Headꢀtoꢀtail selective homodimerization
has also been achieved by an NHC Rh catalyst.11c
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Scheme 1. (PNP)Rh complexes and alkyne dimerization.
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Several years ago, we reported that Rh complexes supported by diarylamido/bis(phosphine) PNP
pincer ligands served as efficient catalysts for alkyne dimerization (Scheme 1).15 The more common
member of this family, 1-Rh(H2), produced an unselective mixture of E and gem isomers, but the “tied”
TPNP rhodium catalyst (2-Rh(H2)) enabled selective production of predominantly isomer E for a rather
T
broad selection of terminal alkynes.16 The PNP ligand requires multiꢀstep synthesis and the reactions
catalyzed by 2-Rh(H2) were not particularly fast, on the order of 10 TON/h at 100 °C. We surmised
that there may be other, more easily accessible pincer ligands that could give rise to analogous Rh
catalysts. To this end, we set out to prepare a series of (pincer)Rh complexes and test their prowess in
alkyne dimerization.
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Results and discussion.
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Synthesis of pincer ligands and their Rh complexes. We selected ligands 3-H through 10-H for our
study. We primarily focused on aryl/bis(phosphine) ligands as they are most easily prepared, especially
in the case of aryl/bis(phosphinite) variants (Scheme 2).
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Scheme 2. Synthesis of bis(phosphinite) ligands.
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Ligands, 3-H,17 4-H,18 and 7-H19 have been previously reported and were synthesized as described in
the literature (with some changes in the procedure for 7-H). Ligands 5-H, 6-H and 8-H were prepared
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analogously from 1,7ꢀnaphthalenediol or 3ꢀhydroxybenzyl alcohol, ClPR2 (R = Pr or Bu), and base.
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Ligands 3-H, 5-H, 7-H, and 8-H were obtained as oils of 95% or better purity as judged by H NMR
spectroscopy and were used as is for the synthesis of the Rh complexes. The aryl/bis(PR3) ligands in
this study differ by the size of the substituent on phosphorus, by the size of the pincer rings fused at the
central MꢀC bond (5,5 vs 5,6), and by the difference in the electron richness of the backbone. The
{[5,6]ꢀPCP}ꢀ ligands20 (5-H, 6-H, 7-H, and 8-H) were intended to favor selectivity for the Eꢀenyne
isomer by increasing the steric bulk around the active site of the metal, a strategy that has been used in
several other systems.9, 11a, 15
We also examined a new C2ꢀsymmetric PNP ligand 9-Me, which offered a variation on the
diarylamido backbone (Scheme 3). Diarylamine A was synthesized via BuchwaldꢀHartwig coupling21 of
2,4ꢀdimethylaniline and 2,4ꢀdimethylbromobenzene. Bromination of A with Nꢀbromosuccinimide
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yielded compound B, which was Nꢀmethylated with KN(SiMe3)2 and iodomethane to give C. Treatment
of C with nꢀbutyllithium and ClPiPr2 yielded 9-Me as a white solid. Ligand 9-Me differs from 1 by
possessing methyl groups ortho to the central nitrogen donor. This causes a high barrier to the rotation
about the ArꢀN bond and results in C2ꢀsymmetry on the NMR time scale as seen by the presence of two
methine signals and four doublets of doublets for the PiPr2 methyls.22 The C2ꢀsymmetry of the ligand is
reduced down to C1 once the ligand is metalated with [(COE)2RhCl]2 (COE = cyclooctene) to form (oꢀ
MePNP)Rh(Me)(Cl) (9-Rh(Me)(Cl)). This is evidenced by the appearance of eight signals for the PiPr2
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methyls by H NMR. The P{1H} NMR spectra showed two different doublets of doublets and large
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coupling between the two inequivalent phosphorus donors, JPP = 414 Hz. Reduction of 9-Rh(Me)(Cl)
with NaBH4 in isopropanol yielded the RhI species 9-Rh(H2), which showed atropisomeric C2ꢀ
symmetry. Complexes of ligand 9 differ from other atropisomeric pincer complexes to date due to the
chirality being generated by a twist in the backbone of the ligand and the use of fiveꢀmembered
metallacycles. Previous atropisomeric pincer complexes rely on long pincer “arms” to establish sixꢀ or
sevenꢀmembered metallacycles that twist the structure of the molecule out of planarity.23 The presence
of fiveꢀmembered metallacycles in complexes of 9-Me is notable because smaller metallacycles in
atropisomeric compounds tend to lead to faster rates of atropisomerism that averages the two
conformations.24,25
Scheme 3. Synthesis of the o-MePNP ligand and its Rh complexes.
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Installation of PCP/POCOP ligands into the coordination sphere of Rh is also most conveniently
accomplished via reaction of the ligand precursor with [(COD)RhCl]2 (Scheme 4). This reaction is
ideally accompanied by loss of COD (= 1,5ꢀcyclooctadiene) and insertion of Rh into the central CꢀH
bond to give (pincer)Rh(H)(Cl). However, this reaction appeared to work cleanly only for the relatively
sterically imposing POCOP ligands 4-H, 5-H, 6-H, and 8-H. In other cases, the reaction was not clean.
We previously described these issues in the synthesis of 3-Rh(H)(Cl) where a second equivalent of free
ligand can coordinate to rhodium, resulting in mixtures of sixꢀcoordinate rhodium products.26 For 3-
Rh(H)(Cl), the problem was solved via a twoꢀstep procedure, first preparing a pyridine adduct 3-
Rh(H)(Cl)(py) followed by extraction of pyridine by BF3. A similar approach was successful for the
synthesis of 7-Rh(H)(Cl) (Scheme 4). The reaction of 7-H with [(COD)RhCl]2 in acetonitrile cleanly
gave the acetonitrile adduct 7-Rh(H)(Cl)(NCMe), which in reaction with excess NaOAc released the
coordinated acetonitrile to produce 7-Rh(H)(OAc). Treatment of 7-Rh(H)(OAc) with Me3SiCl after
removal of all of acetonitrile under vacuum resulted in the formation of 7-Rh(H)(Cl). In a yet another
variation, sixꢀcoordinate 10-Rh(H)(OAc) was prepared directly from 10-H27 and [(COD)Rh(OAc)]2
and metathesis with Me3SiCl gave the corresponding fiveꢀcoordinate hydridoꢀchloride complex 10-
Rh(H)(Cl). The fiveꢀcoordinate complexes n-Rh(H)(Cl) (n = 3-8, 10) displayed a hydride resonance in
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the ꢀ24 to ꢀ27 ppm range in the H NMR spectra. Complexes with inequivalent phosphorus donors
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showed strong phosphorusꢀphosphorus coupling in the 31P{1H} NMR spectra, with JPP values in the
400ꢀ430 Hz range.
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Scheme 4. Synthesis of Rh pincer complexes.
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The desired RhI precursors were made from complexes n-Rh(H)(Cl) (n = 3, 5, 6, 7, 8, 10) by treating
them with NaOtBu in the presence of diisopropyl sulfide, which led to clean formation of n-Rh(SiPr2)
(n = 3, 5, 6, 7, 8, 10). We also prepared the 3ꢀhexyne adduct 3-Rh(C6H10) in an analogous fashion. For
ligands 4-H and 9-Me, dihydrogen complexes 4-Rh(H2)28 and 9-Rh(H2) were synthesized. We also
prepared 9-Rh(HD) from which the JHD value of 20 Hz was extracted. Using established29 relationships
between HꢀH distances and JHꢀD coupling, we conclude that 9-Rh(H2) is a “stretched” or “elongated”
dihydrogen complex,30 with a predicted HꢀH distance of 1.1 Å. This matches a previously synthesized
PNPꢀbased rhodium dihydrogen adduct.16 We have previously used SiPr2 as a useful placeholder ligand
in the chemistry of (PNP)Rh complexes: it forms isolable adducts with RhI, dissociates rather easily,
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and has no affinity for coordinating to RhIII complexes.31 The RhI complexes possessed larger JRhꢀP
values compared to the RhIII compounds described above, but lower 2JPꢀP values.
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Scheme 5. Synthesis of Rh(I) pincer carbonyl complexes.
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Treatment of 5-Rh(H)(Cl) and 6-Rh(H)(Cl) with NaOtBu under an atmosphere of CO gave the
corresponding (pincer)Rh(CO) complex (5-Rh(CO) and 6-Rh(CO), Scheme 5). Pincer carbonyl
complexes could also be obtained by treating the (pincer)Rh(SiPr2) complexes (7-Rh(SiPr2) and 8-
Rh(SiPr2)) with an atmosphere of CO to form 7-Rh(CO) and 8-Rh(CO). Complexes n-Rh(CO) (n = 5-
8) were analyzed using IR spectroscopy and compared to the reported CO stretching frequencies of 3-
Rh(CO),32 4-Rh(CO),33 10-Rh(CO)32 to gauge the electron richness34 of the ligand backbone (Table 1).
Not surprisingly, the bis(phosphinite) POCOP ligands showed lower electron donation to the metal
center than the bis(phosphine) PCP ligand, due to the electron withdrawing ability of the oxygen atoms.
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Table 1: Carbonyl stretching frequencies of PCP/POCOP rhodium carbonyl compounds .
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IR νCO (cmꢀ1)
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Complex
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(POCOPiPr)Rh(CO) (3-Rh(CO))
(POCOPtBu)Rh(CO) (4-Rh(CO))
NapthPOCOPiPr)Rh(CO) (5-Rh(CO))
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(
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(POCCH2OPiPr)Rh(CO) (7-Rh(CO))
NapthPOCOPtBu)Rh(CO) (6-Rh(CO))
(
(POCCH2OPtBu)Rh(CO) (8-Rh(CO))
(PCPiPr)Rh(CO) (10-Rh(CO))
Catalysis of alkyne dimerization. We selected three alkynes for the screening of catalysts:
nBuC≡CH, Me3SiC≡CH, and 4ꢀMeC6H4C≡CH. These three substrates did not allow for the evaluation
of the functional group tolerance of the catalysts, but they provided a reasonable sampling of steric and
electronic differences in terminal alkynes. In this study, we were primarily interested in gauging
catalyst activity, longevity, and selectivity. All catalysts were introduced as either RhI diisopropyl
sulfide adducts or as RhI dihydrogen adducts.
Table 2 details the results of our screening in reactions conducted at 80 °C with 1% catalyst loading.
To more closely match the conditions used in our previous study,15 we additionally conducted the
dimerization of the three alkynes using 0.5% 3-Rh(SiPr2) at 100 °C, and found little difference with the
selectivities observed with 1% 3-Rh(SiPr2) at 80 °C.35 We also conducted a comparison of 3-Rh(SiPr2)
and 3-Rh(C6H10) as catalysts in a separate pair of experiments, and found them giving the same
conversion and isomer distribution within errors of measurement, thus confirming the irrelevance of the
placeholder ligand L in n-Rh(L) compounds as catalysts.
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Table 2. Conversion of alkyne and the isomeric distribution of the produced enynes.
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Substrate
4ꢀMeC6H4C≡CH
nBuC≡CH
[Rh] =
Time
3 h
Gem : E : Z : oligomers
29 : 69 : 0 : 2
73: 19 : 0 : 8
% Conversiona
3-Rh(SiPr2)
3-Rh(SiPr2)
3-Rh(SiPr2)
4-Rh(H2)
>97
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>97
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7
3 h
Me3SiC≡CH
4ꢀMeC6H4C≡CH
nBuC≡CH
3 h
63: 35 : 0 : 2
36 h
36 h
36 h
3 h
11: 73 : 0 : 16
84 : 16: 0 : 0
4-Rh(H2)
Me3SiC≡CH
4ꢀMeC6H4C≡CH
nBuC≡CH
76: 24 : 0 : 0
80
>97
95
>97
5
4-Rh(H2)
5-Rh(SiPr2)
5-Rh(SiPr2)
5-Rh(SiPr2)
6-Rh(SiPr2)
6-Rh(SiPr2)
6-Rh(SiPr2)
7-Rh(SiPr2)
7-Rh(SiPr2)
7-Rh(SiPr2)
8-Rh(SiPr2)
8-Rh(SiPr2)
8-Rh(SiPr2)
9-Rh(H2)
24 : 70 : 0 : 6
62 : 31: 0 : 7
3 h
Me3SiC≡CH
4ꢀMeC6H4C≡CH
nBuC≡CH
3 h
10 : 79 : 0 : 11
11 : 46 : 0 : 43
89 : 11 : 0 : 0
25 : 33 : 0 : 42
13 : 62 : 0 : 25
82 : 14 : 0 : 4
19 : 66 : 8 : 7
16 : 11: 0 : 73
74 : 26 : 0 : 0
15 : 60 : 0 : 25
2 : 73 : 0 : 25
29 : 71 : 0 : 0
17 : 53 : 0 : 30
22 : 56 : 0 : 22
36 h
36 h
36 h
36 h
36 h
36 h
36 h
36 h
36 h
70 h
70 h
70 h
36 h
1
Me3SiC≡CH
4ꢀMeC6H4C≡CH
nBuC≡CH
5
>97
47
95
4
Me3SiC≡CH
4ꢀMeC6H4C≡CH
nBuC≡CH
3
Me3SiC≡CH
4ꢀMeC6H4C≡CH
nBuC≡CH
22
74
25
45
94
9-Rh(H2)
Me3SiC≡CH
4ꢀMeC6H4C≡CH
9-Rh(H2)
10-Rh(SiPr2)
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nBuC≡CH
Me3SiC≡CH
36 h
36 h
65 : 18 : 0 : 17
16 : 65 : 1 : 18
63
10-Rh(SiPr2)
10-Rh(SiPr2)
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2
3
>97
4
5
a Fraction of consumed alkyne by 1H NMR spectroscopy versus a 1,4ꢀdioxane internal standard.
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The Z isomer was absent in all but two experiments with Me3SiC≡CH where it was produced in small
amounts, possibly indicating the similarity in mechanism between PCP/POCOP and PNPꢀbased
catalysts (Scheme 6). The appearance of the Z isomer might be indicative of a competing vinylidene
intermediate in the catalytic cycle that is accessible when using a strongly electronꢀdonating terminal
alkyne. It has been shown experimentally that ethynyltrimethylsilane can react with a nominally 14ꢀ
electron RhI compound ([Rh(Cl)(PiPr3)2]2) to give a fiveꢀcoordinate rhodium(III) hydridoalkynyl, which
rearranges to the corresponding vinylidene isomer.36 This mechanism of coupling a vinylidene with an
acetylide is a common motif found in Zꢀselective ruthenium alkyne dimerization catalysts7a,b and was
also considered by Goldman et al. in a study of alkyne dimerization by (pincer)Ir catalysts.37
Scheme 6. Possible alkyne dimerization mechanisms.
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The ratios of gemꢀ vs Eꢀisomers (Table 3) varied depending on the substrate and the supporting
pincer ligand, but none of the catalysts screened in this study demonstrated high selectivity for either the
gemꢀ or the Eꢀproduct. With 1ꢀhexyne, the gemꢀisomer was typically preferred; with 4ꢀethynyltoluene,
the Eꢀisomer typically formed in greater quantity. However, no clear trend can be extracted from these
results as far as analyzing the influence of the nature of the pincer ligand on selectivity. For example,
there is no obvious correlation between νCO stretching frequencies of n-Rh(CO) (Table 1) and the rates
of the dimerization reactions or selectivity. 9-Rh(H2) performed more similarly to 1-Rh(H2) than 2-
Rh(H2): sluggishly and not selectively. It would seem that catalyst 9-Rh(H2) had a high selectivity for
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forming the Eꢀisomer over the gemꢀenyne for 4ꢀethynyltoluene, but by monitoring the reaction by H
NMR over the course of the 70 h reaction time, it was seen that the gem isomer was formed and reacts
further to form oligomeric products, which is a known behavior of 1,3ꢀdiarylbutenynes.38
Table 3. Geminal/E enyne isomer ratios for dimerization catalysts.
1ꢀhexyne
Gem/E
3.8
4ꢀethynyltoluene
Ethynyltrimethylsilane
Gem/E
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0.15
0.34
0.24
0.21
1.5
Gem/E
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3-Rh(SiPr2)
4-Rh(H2)
5.3
3.2
5-Rh(SiPr2)
6-Rh(SiPr2)
7-Rh(SiPr2)
8-Rh(SiPr2)
9-Rh(H2)
2.0
0.13
0.75
0.25
0.28
0.32
0.25
8.1
5.9
2.9
0.4
0.03
0.39
10-Rh(SiPr2)
3.6
With respect to the rates of reaction, (POCOP)ꢀ and (NaptPOCOP)ꢀsupported catalysts bearing PiPr2
arms appeared to work the fastest, and faster than those reported with 2-Rh(H2). Catalysts based on
PtBu2ꢀcontaining ligands 4, 6, and 8 operated much more slowly, presumably owing the prohibitive
steric bulk of the four tertꢀbutyl groups. In an effort to gauge the longevity of the catalyst, we have also
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performed dimerization of Me3SiC≡CH using 0.005% of 3-Rh(SiPr2) at 100 °C, and observed >97%
conversion to the dimerization products after 36 h, amounting to ca. 20,000 turnovers.
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Conclusion
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In summary, we have prepared a series of (pincer)RhI complexes for study as potential catalysts for
alkyne dimerization to enynes. Some of the reported ligands and their Rh complexes are new. Our
findings indicate that aryl/bis(phosphine/phosphinite) PCP or POCOP pincer ligands do result in Rh
catalysts capable of alkyne dimerization. Similarly to the PNPꢀbased catalysts reported previously, the
PCP/POCOP systems produce little to no Zꢀenynes as products, possibly suggesting a common
mechanism. PCPꢀ and POCOPꢀbased Rh compounds with PiPr2 side arms are faster catalysts than the
PNPꢀbased Rh complexes. However, none of the compounds under study in this work displayed
notable selectivity for either Eꢀ or gemꢀenyne isomer. While the isomeric ratios vary considerably as a
function of the catalyst and the alkyne substrate, clear trends are not apparent.
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Experimental
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General Considerations. Unless otherwise specified, all manipulations were performed under an
argon atmosphere using standard Schlenk line or glove box techniques. Toluene, THF, pentane, and
isooctane were dried and deoxygenated (by purging) using a solvent purification system and stored over
molecular sieves in an Arꢀfilled glove box. C6D6 was dried over and distilled from NaK/Ph2CO/18ꢀ
crownꢀ6 and stored over molecular sieves in an Arꢀfilled glove box. Fluorobenzene and 1,4ꢀdioxane
were dried with and then distilled or vacuum transferred from CaH2. Synthesis of 3-H,17 4-H,18 10-H,27
3-Rh(H)(Cl),26 4-Rh(H2),28 [(COD)RhCl]2,39 [(COD)Rh(OAc)]2,40 [(COE)2RhCl]241 was accomplished
according to literature procedures. 7-H was synthesized by modification of a literature procedure.19
NMR spectra were recorded on a Varian NMRS 500 (1H NMR, 499.686 MHz; 13C NMR, 125.659
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MHz; P NMR, 202.298 MHz) spectrometer. Chemical shifts are reported in δ (ppm). For H and C
NMR spectra, the residual solvent peak was used as an internal reference. 31P NMR spectra were
referenced externally using 85% H3PO4 at δ 0 ppm. Alkynes and isopropyl sulfide were freezeꢀpumpedꢀ
thawed to remove oxygen before entering the glovebox. Elemental analyses were performed by CALI
Labs, Inc. (Parsippany, NJ).
Synthesis of (POCOP)Rh(SiPr2) (3-Rh(SiPr2). In a Schlenk flask, 3-Rh(H)(Cl) (298 mg, 0.624
mmol) was dissolved in toluene and was treated with NaOtBu (148 mg, 1.54 mmol), and SiPr2 (82.4 ꢀL,
0.624 mmol). The reaction was stirred for 60 min at RT, the reaction was passed through a pad of Celite
and the volatiles were removed by vacuum and recrystallized from pentane to give a brownꢀyellow solid
(294 mg, 84% yield). 31P{1H} NMR (C6D6): δ 184.8 (d, JRhꢀP = 174 Hz); 1H NMR (C6D6): δ 6.99 (t, 1H,
ArꢀH, J = 7.5 Hz), 6.89 (d, 2H, ArꢀH, J = 8.0 Hz), 2.70 (m, 2H, SCHMe2), 2.20 (m, 4H, CHMe2), 1.29
(apparent q (dvt), 12H, P(CHCH3)2, J = 7 Hz), 1.25 (apparent q (dvt), 12H, P(CHCH3)2, J = 7 Hz), 1.21
(d, 12H, S(CHCH3)2, J = 7 Hz); 13C{1H} NMR (C6D6): δ 167.7 (t, JCꢀP = 9 Hz, ArꢀOP), 140.9 (dt, JRhꢀC
= 35 Hz, JCꢀP = 10 Hz, ArꢀRh), 124.7 (s, Ar), 103.8 (t, JCꢀP = 7 Hz, ArꢀH), 40.9 (s, SCHMe2), 30.6 (dvt,
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JCꢀP = 10 Hz, JRhꢀC = 2 Hz, PCHMe2), 24.1 (s, SCHMe2), 18.7 (t, JCꢀP = 4 Hz, PCHMe2), 17.6 (s,
PCHMe2). Elem. Anal. Found (Calculated) for C24H45O2P2RhS: C, 50.98 (51.24); H, 7.97 (8.06).
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Synthesis of (POCOP)Rh(C6H10) (3-Rh(C6H10)). 3-Rh(H)(Cl) (150 mg, 0.312 mmol) was dissolved
in toluene and treated with NaOtBu (33 mg, 0.343 mmol) and 3ꢀhexyne (39 ꢁL, 0.343 mmol) and stirred
for 2 h. The volatiles were removed under vacuum and the product was extracted with pentane and
filtered through silica and Celite. The volatiles were removed under vacuum to yield a light orange solid
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judged to be >97% pure by 1H NMR spectroscopy (85 mg, 52% yield). P{1H} NMR (C6D6): δ 182.0
(d, JRhꢀP = 166 Hz); 1H NMR (C6D6): δ 6.99 (t, 1H, J = 8 Hz, ArꢀH), 6.93 (d, 2H, J = 8 Hz), 2.47 (q, 4H,
J = 7.5 Hz, hexyneꢀCH2), 2.03 (m, 4H, PCHMe2), 1.24 (apparent q (dvt), 12H, P(CHCH3)2, J = 7 Hz),
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1.16 (t, 6H, J = 7.5 Hz, hexyneꢀCH3), 1.11(apparent q (dvt), 12H, P(CHCH3)2, J = 7.5 Hz); C{1H}
NMR (C6D6): δ 168.7 (vt, JCꢀP = 8.7 Hz, ArꢀOP), 143.3 (dvt, JRhꢀC = 31.0 Hz, JPꢀC = 9.2 Hz, ArꢀRh),
127.3 (s, Ar), 104.2 (t, JCꢀP = 6.6 Hz, ArꢀH), 77.4 (d, JRhꢀC = 6.8 Hz, Rhꢀ(C≡C), 29.9 (dt, JCꢀP = 9.6 Hz,
JRhꢀC = 2.1 Hz, PCHMe2), 20.8 (s, hexyne), 17.6 (t, JCꢀP = 4.5 Hz, PCHMe2), 17.5 (s, PCHMe2), 16.0 (s,
hexyne).
Synthesis of (NaptPOCOP)H (5-H). In a Teflon screwꢀtop flask, 1,7ꢀdihydroxynaphthalene (479 mg,
2.99mmol) was dissolved in THF and ClPiPr2 (956 mg, 6.26 mmol) was added slowly while stirring.
The solution turned from dark to light brown with the dropwise addition of NEt3 (994 mg, 9.82 mmol).
The reaction mixture was heated at 85 ⁰C for 1.5 h. The mixture was then passed through Celite, and the
volatiles were removed under vacuum to produce a thick brown oil that was determined to be >95%
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pure by H NMR spectroscopy (926 mg, 79% yield). P{1H} NMR (C6D6): δ 148.1 (s), 146.9 (s); H
NMR (C6D6): δ 8.41 (t, 1H, J = 2.5 Hz, ArꢀH), 7.56 (t, 1H, J = 2.5 Hz, ArꢀH), 7.53 (d, 1H, J = 9.5 Hz,
ArꢀH), 7.37 (m, 1H, ArꢀH), 7.29 (d, 1H, J = 8 Hz, ArꢀH), 7.15 (m, 1H, ArꢀH), 1.83 (m, 4H, PꢀCHMe2),
1.20 (m, 12H, CH(CH3)2), 1.01 (m, 12H, CH(CH3)2); 13C{1H} NMR (C6D6): δ 157.6 (d, JCꢀP = 8 Hz,
ArꢀOP), 154.9 (d, JCꢀP = 9 Hz, Ar-OP), 131.4 (Ar), 129.8 (Ar), 124.2 (Ar), 121.3 (Ar), 121.1 (d, JCꢀP = 6
Hz, Ar), 111.8 (Ar), 111.7 (Ar), 108.4 (d, JCꢀP = 16 Hz, Ar), 28.7 (d , JCꢀP = 19 Hz, 2 CHMe2), 18.0 (d,
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JCꢀP = 15 Hz, CHMe2), 17.8 (d, JCꢀP = 15 Hz, CHMe2), 17.3 (d, JCꢀP = 5 Hz, CHMe2), 17.24 (d, JCꢀP = 5
Hz, CHMe2).
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Synthesis of (NaptPOCOP)Rh(H)(Cl) (5-Rh(H)(Cl)). In a Teflon screwꢀtop flask, 5 (209 mg, 0.533
mmol) and [(COD)RhCl]2 (131 mg, 1.066 mmol) were dissolved in toluene and stirred overnight at 90
⁰C. The reaction mixture was passed through silica and Celite, and the volatiles were removed under
vacuum. The resulting red solid was dissolved in a minimum amount of toluene and layered with
pentane. A red solid precipitated out of solution (215 mg, 76%). 31P{1H} (C6D6): δ 183.7 (dd, JPꢀP = 424
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Hz, JPꢀRh = 111 Hz), 164.4 (dd, JPꢀP = 418 Hz, JPꢀRh = 121 Hz); H NMR (C6D6): δ 7.38 (t, 2H, J = 8.5
Hz, ArꢀH), 7.20 (d, 1H, J = 9 Hz, ArꢀH), 7.11 (d, 1H, J = 7.5 Hz, ArꢀH), 7.05 (t, 1H, J = 8 Hz, ArꢀH),
2.75 (m, 1H, PCHMe2), 2.64 (m, 1H, PCHMe2), 2.46 (m, 1H, PCHMe2), 2.21 (m, 1H, PCHMe2), 1.35
(dd, 3H, JHꢀP = 17.5 Hz, JHꢀH = 7.5 Hz, PCH(CH3)2), 1.18 (m, 21H, PCH(CH3)2), ꢀ24.10 (apparent dt,
1H, JHꢀRh = 45 Hz, JHꢀP = 15 Hz, RhꢀH); 13C{1H} NMR (C6D6): δ 166.1 (m, ArꢀOP), 154.7 (m, ArꢀOP),
133.1 (s, Ar), 130.1 (d, J = 9 Hz, Ar), 128.4 (Ar), 125.4 (Ar), 123.4 (Ar), 123.1 (m, CꢀRh) 115.5 (d, J =
2.5 Hz, Ar), 115.3 (d, JCꢀP = 13 Hz, Ar), 29.8 (m, PCHMe2), 29.5 (m, PCHMe2) 29.0 (m, PCHMe2),
28.17 (d, JCꢀP = 23 Hz, PCHMe2), 18.7 (d, JCꢀP = 4 Hz, PCHMe2), 18.3 (s, PCHMe2), 18.0 (s, PCHMe2),
17.7 (s, PCHMe2), 17.6 (s, PCHMe2), 17.1 (m, PCHMe2), 16.4 (m, PCHMe2), 16.1 (s, PCHMe2). Elem.
Anal. Found (Calculated) for C22H34ClO2P2Rh: C, 49.91 (49.78); H, 6.24 (6.46).
Synthesis of (NaptPOCOPiPr)Rh(SiPr2) (5-Rh(SiPr2)). In a Schlenk flask, 5-Rh(H)(Cl) (180 mg,
0.339 mmol), NaOtBu (56 mg, 0.509 mmol), and diisopropyl sulfide (100 ꢁL, 0.688 mmol) were
dissolved in toluene. The reaction mixture was stirred for 1 h at RT, and the volatiles were removed
under vacuum. The resulting solid was washed with pentane and dissolved in benzene to be filtered over
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a pad of Celite. The volatiles were removed to yield a dark orange solid (73 mg, 35%). P{1H} NMR
(C6D6): δ 181.6 (dd, JPꢀP = 362 Hz, JPꢀRh = 162 Hz), 156.2 (dd, JPꢀP = 362 Hz, JPꢀRh = 172 Hz); 1H NMR
(C6D6): δ 7.49 (m, 3H, ArꢀH), 7.20 (d, J = 10 Hz, 1H, ArꢀH), 7.15 (t, obscured by benzene peak, 1H,
ArꢀH), 2.71 (m, 2H, S(CHMe2)2), 2.40 (m, 2H, P(CHMe2)2), 2.22 (m, 2H, P(CHMe2)2), 1.30 (dd, 6H, J
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= 7 Hz, J = 5 Hz, PCH(CH3)2), 1.28 (dd, 6H, J = 8 Hz, J = 4 Hz, PCH(CH3)2), 1.27 (dd, 6H, J = 7 Hz, J
= 5 Hz, PCH(CH3)2), 1.25 (dd, 6H, J = 9 Hz, J = 5 Hz, PCH(CH3)2), 1.21 (d, 12H, J = 10 Hz,
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S(CHMe2)); C{1H} NMR (C6D6): δ 166.2 (d, JCꢀP = 16 Hz, ArꢀOP), 156.1 (d, JCꢀP = 3 Hz, , ArꢀOP),
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135.0 (br d, JCꢀRh = 41 Hz, ArꢀRh), 132.6 (Ar), 131.5 (d, J = 12 Hz, Ar), 126.6 (Ar), 123.7 (Ar), 122.2
(Ar), 114.3 (d, J = 15 Hz, Ar), 113.2 (d, J = 5 Hz, Ar), 37.6 (dd, J = 13 Hz, S(CHMe2)2), 31.0 (ddd, JCꢀP
= 13 Hz, J = 5 Hz, J = 3 Hz, P(CHMe2)2), 30.5 (ddd, JCꢀP = 19 Hz, J = 5 Hz, J = 3 Hz, P(CHMe2)2), 24.9
(s, (S(CHMe2)2), 19.2 (dJCꢀP = 9 Hz, P(CHMe2)2), 18.8 (d, JCꢀP = 6 Hz, P(CHMe2)2), 17.8 (s,
P(CHMe2)2), 17.6 (s, P(CHMe2)2). Elem. Anal. Found (Calculated) for C28H47O2P2RhS: C, 54.90
(54.81); H, 7.73 (7.69).
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Synthesis of (NaptPOCOPiPr)Rh(CO) (5-Rh(CO)). In a Teflon screwꢀtop flask, 5-Rh(H)(Cl) (106
mg, 0.200 mmol) was dissolved in toluene and treated with NaOtBu (30 mg, 0.312 mmol). The flask
was then degassed, filled with CO, and stirred at RT for 2 h. The volatiles were removed and product
was extracted with pentane and filtered through silica and Celite. The volatiles were removed and the
product was recrystallized from hexamethyldisiloxane as yellow crystals in >98% purity as judged by
1H NMR (64 mg, 62% yield). 31P{1H} NMR (C6D6): δ 199.3 (dd, JPꢀP = 318 Hz, JPꢀRh = 140 Hz), 170.0
(dd, JPꢀP = 317 Hz, JPꢀRh = 147 Hz); 1H NMR (C6D6): δ 7.52 (dd, 1H, J = 9 Hz, J = 2 Hz), 8.5 (d, 2H, J =
9 Hz), 7.44 (dd, 1H, J = 8 Hz, 2 Hz), 7.20 (dd, 1H, J = 8 Hz, 2 Hz), 7.11 (dd, 1H, apparent t, 8 Hz), 2.13
(m, 4H, CHMe2), 0.87 (dd, 6H, JHꢀP = 17.5 Hz, J = 7 Hz, PCH(Me)2), 0.86 (dd, 6H, JHꢀP = 18 Hz, J = 7
Hz, PCH(Me)2), 0.86 (dd, 6H, JHꢀP = 14.5 Hz, 7 Hz, PCH(Me)2), 0.85 (dd, 6H, JHꢀP = 14 Hz, 7 Hz,
PCH(Me)2). 13C{1H} NMR (C6D6): δ 196.8 (ddd (apparent dt), JRhꢀC = 56 Hz, JCꢀP = 14 Hz, JCꢀP = 14 Hz,
RhꢀCO), 168.0 (dd, JCꢀP = 16 Hz, JCꢀRh = 3 Hz, ArꢀOP), 155.5 (dd (apparent t), JCꢀP = 2 Hz, JCꢀRh = 2 Hz,
ArꢀOP), 137.8 (ddd, JCꢀRh = 31 Hz, JCꢀP = 13 Hz, JCꢀP = 6 Hz, ArꢀRh), 132.0 (m, Ar), 130.3 (s, ArꢀH),
129.9 (d, J = 12 Hz, Ar), 124.9 (s, ArꢀH), 122.7 (s, ArꢀH), 114.9 (d, J = 5 Hz, ArꢀH), 114.8 (d, J = 5 Hz,
ArꢀH), 114.8 (d, J = 15 Hz, ArꢀH), 32.3 (ddd, JCꢀP = 24 Hz, J = 4 Hz, J = 2 Hz, P(CHMe2)2), 30.4
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(apparent dt (ddd), JCꢀP = 22 Hz, J = 3 Hz, P(CHMe2)2), 18.6 (d, JCꢀP = 8 Hz, P(CHMe2)2), 17.9 (d, JCꢀP
7 Hz, P(CHMe2)2), 17.6 (s, P(CHMe2)2), 17.5 (s, P(CHMe2)2). IR: 1950 cmꢀ1, ν CO
=
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Synthesis of 1,7-bis(ditertbutylphosphinyl)naphthalenediol (6-H). In a culture tube, 1,7ꢀ
dihydroxynaphthalene (78 mg, 0.487mmol) was dissolved in THF and NaH (36 mg, 1.5 mmol) was
added slowly. The reaction mixture was refluxed for 4 h and passed through a pad of Celite with diethyl
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ether. The volatiles were removed under vacuum to give a brown solid determined by H NMR
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spectroscopy to be >95% pure (156 mg, 71%). 31P{1H} NMR (C6D6): δ 154.8 (s), 150.5 (s); H NMR
(C6D6): 8.51 (s, 1H, ArꢀH), 7.62 (m, 1H, ArꢀH), 7.55 (d, 1H, J = 9 Hz, ArꢀH), 7.35 (m, 1H, ArꢀH), 7.29
(d, 1H, J = 8 Hz, ArꢀH), 7.18 (d, 1H, J = 8 Hz, ArꢀH), 1.19 (d, 36H, C(CH3)3, JHꢀP = 11 Hz); C{1H}
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NMR (C6D6): δ 158.1 (d, JCꢀP = 10 Hz, ArꢀOP), 155.2 (d, JCꢀP = 9 Hz, ArꢀOP), 131.4 (Ar), 129.7 (Ar),
124.2 (Ar), 121.1 (d, JCꢀP = 6 Hz, Ar), 120.9 (Ar), 111.3 (Ar), 111.2 (Ar), 108.4 (Ar, JCꢀP = 16 Hz), 36.0
(JCꢀP = 16 Hz, PCMe3), 35.8 (JCꢀP = 15 Hz, PCMe3), 27.7 (d, JCꢀP = 2 Hz, PC(CH3)3), 27.6 (d, JCꢀP = 2
Hz, PC(CH3)3). HRMS (ESI+TOF) m/z: [M + H]+ Calcd. for C26H44O2P2 449.2733; found 449.2728
Synthesis of (NapthPOCOPtBu)Rh(H)(Cl) (6-Rh(H)(Cl)). In a Teflon screwꢀtop flask, 6-H (64.4 mg,
0.144 mmol) and [(COD)Rh(Cl)]2 (35.4 mg, 0.717 mmol) were dissolved in toluene and stirred
overnight at 80 °C. The reaction mixture was filtered through Celite and the volatiles were removed
under vacuum. The resulting solid recrystallized from diethyl ether at ꢀ35 °C to yield brown crystals
judged to be >97% pure by 1H NMR (78 mg, 92%). P{1H} NMR (C6D6): δ 184.8 (dd, JPꢀP = 408 Hz,
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JPꢀRh = 115 Hz), 166.5 (dd, JPꢀP = 406 Hz, JPꢀRh = 121 Hz); 1H NMR (C6D6): δ 7.40 (m, 2H, ArꢀH), 7.21
(d, 2H, J = 9 Hz, ArꢀH), 7.07 (m, 2H, ArꢀH), 1.47 (d, 9H, JHꢀP = 14 Hz, PC(CH3)3), 1.42 (d, 9H, JHꢀP
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14 Hz, PC(CH3)3), 1.38 (d, 9H, JHꢀP = 15 Hz, PC(CH3)3), 1.35 (d, 9H, JHꢀP = 15 Hz, PC(CH3)3), ꢀ25.21
(ddd, 1H, JHꢀRh = 46 Hz, JHꢀP = 12 Hz, JHꢀP = 12 Hz); C{1H} NMR (C6D6): δ 167.2 (dd, JCꢀP = 11 Hz,
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CꢀRh = 4 Hz, ArꢀOP), 154.7 (dd, J = 4 Hz, J = 3 Hz, ArꢀOP), 133.06 (Ar), 130.1 (d, J = 8 Hz, Ar), 125.2
(Ar), 123.3 (Ar), 115.47 (Ar), 115.43 (Ar), 115.37 (Ar), 115.27 (Ar), 43.0 (dd, JCꢀP = 8 Hz, JCꢀRh = 6 Hz,
P(CMe3)2), 41.4 (dd, JCꢀP = 9 Hz, JCꢀRh = 6 Hz, P(CMe3)2), 40.4 (ddd, JCꢀP = 20 Hz, J = 5 Hz, J = 1 Hz,
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ACS Catalysis
P(CMe3)2), 38.6 (ddd, JCꢀP = 14 Hz, J = 5 Hz, J = 3 Hz, P(CMe3)2), 28.9 (d, JCꢀP = 6 Hz, P(CMe3)2), 28.8
(d, JCꢀP = 5 Hz, P(CMe3)2), 28.7 (d, JCꢀP = 5 Hz, P(CMe3)2), 28.1 (d, JCꢀP = 5 Hz, P(CMe3)2).
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Synthesis of (NaptPOCOPtBu)Rh(SiPr2) (6-Rh(SiPr2)). In a Schlenk flask, 6-Rh(H)(Cl) (110 mg,
0.187 mmol), NaOtBu (30 mg, 0.281 mmol), diisopropyl sulfide (55 ꢁL, 0.374 mmol) were mixed in
toluene and stirred for 3 h at RT. The volatiles were removed under vacuum, and the resulting solid was
dissolved in pentane and passed through Celite. The resulting brown solid was dissolved in a minimum
of pentane and placed in a ꢀ35 °C freezer overnight to produce brown crystals (59 mg, 47% yield).
31P{1H} NMR (C6D6): δ 185.4 (dd, JPꢀP = 327 Hz, JPꢀRh = 168 Hz), 163.2 (dd, JPꢀP = 323 Hz, JPꢀRh = 175
Hz); 1H NMR (C6D6): δ 7.41 (br s, 2H, ArꢀH), 7.27 (br s, 1H, ArꢀH), 7.15 (br s, 2H, ArꢀH), 2.82 (m, 2H,
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S(CHMe2)2), 1.40 (d, 36H, JHꢀP = 6 Hz, P(CMe3)2), 1.21 (d, 12H, JHꢀH = 4 Hz, S(CHMe2)2); C{1H}
NMR (C6D6): δ 166.8 (d, JCꢀP = 19 Hz, ArꢀOP), 156.1 (d, JCꢀP = 3 Hz, ArꢀOP), 132.8 (Ar), 131.6 (m, Arꢀ
Rh), 126.3 (Ar), 124.1 (Ar), 122.2 (Ar), 114.4 (d, JCꢀP =14 Hz, Ar), 113.32 (Ar), 113.29 (Ar), 41.0 (m,
S(CHMe2)2), 39.7 (m, P(CMe3)2), 38.2 (s, P(CMe3)2) 29.5 (d, JCꢀP = 9 Hz, P(CMe3)2), 29.4 (d, J = 8 Hz,
P(CMe3)2), 24.9 (s, S(CHMe2)). Elem. Anal. Found (calculated) for C32H55O2P2RhS: C, 57.29 (57.48);
H, 8.16 (8.29).
(
NaptPOCOPtBu)Rh(CO) (6-Rh(CO)). In a 10 mL Teflon screwꢀtop flask, 6-Rh(H)(Cl) (50 mg,
0.085 mmol) was dissolved in toluene and treated with NaOtBu (10 mg, 0.10 mmol). The flask was
degassed and filled with CO and stirred overnight at RT. The volatiles were removed under vacuum and
the product was extracted with pentane and filtered through silica and Celite. The volatiles were
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removed to produce a yellow powder judged to be >97% pure by H NMR (30 mg, 61%). 31P{1H}
NMR (C6D6): δ 207.1 (dd, JPꢀP = 306 Hz, JPꢀRh = 140 Hz), 179.7 (dd, JPꢀP = 306 Hz, JPꢀRh = 147 Hz); 1H
NMR (C6D6): δ 7.53 (dd, 1H, J = 2 Hz, J = 9 Hz), 7.44 (t, 2H, J = 8 Hz, ArꢀH), 7.19 (dd, 1H, J = 8 Hz, J
= 2 Hz, ArꢀH), 7.13 (t, 2H, J = 8 Hz, ArꢀH), 1.35 (d, 18H, JHꢀP = 7 Hz, P(CMe3)2), 1.32 (d, 18H, JCꢀP = 7
Hz, P(CMe3)2); 13C{1H} NMR (C6D6): δ 198.7 (ddd (apparent dt), JCꢀRh = 57 Hz, JCꢀP = 14 Hz, RhꢀCO),
168.9 (dd, JCꢀP = 15 Hz, JCꢀRh = 3 Hz, ArꢀOP), 156.4 (m, ArꢀOP), 138.4 (ddd, JCꢀRh = 33 Hz, JCꢀP = 13
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Hz, JCꢀP = 6 Hz, ArꢀRh), 132.0 (s, Ar), 130.2 (s, ArꢀH), 129.3 (d, J = 11 Hz, Ar), 124.7 (s, ArꢀH), 122.6
(s, ArꢀH), 114.8 (d, J = 15 Hz, ArꢀH), 114.5 (d, J = 5 Hz, ArꢀH), 41.3 (ddd, JCꢀP = 17 Hz, J = 4 Hz, J = 2
Hz, P(CMe3)2), 39.9 (apparent dt, JCꢀP = 15 Hz, J = 3 Hz, P(CMe3)2), 28.6 (d, JCꢀP = 7 Hz, P(CMe3)2),
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28.3 (d, JCꢀP = 7 Hz, P(CMe3)2). IR: 1945 cmꢀ1, ν CO
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Synthesis of 1-(iPr2PO)-3-(iPr2POCH2)(C6H4) (7-H).42 To a solution of 3ꢀhydroxybenzyl alcohol
(0.508 g, 4.09 mmol) in THF, triethylamine (1.241 g, 12.3 mmol) was added dropwise while stirring. A
solution of ClPiPr2 (1.290 g, 8.18 mmol) in THF was added slowly while stirring. A precipitate formed
immediately and the reaction was stirred overnight at RT. The reaction mixture was passed through a
pad of Celite, and the solvent was removed under vacuum to produce a colorless oil determined to be
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>95% pure by 1H NMR spectroscopy (1.236 g, 85%). P{1H} NMR (C6D6): δ 155.2 (s), 147.6 (s); H
NMR (C6D6): δ 6.88 (d, 1H, J = 8 Hz, ArꢀH); 6.79 (t, 1H, J = 8 Hz, ArꢀH), 6.62 (d, 1H, ArꢀH, J = 8 Hz,
ArꢀH), 4.43 (d, 2H, JHꢀP = 10 Hz, CH2OP), 1.47 (m, 2H, P(CHMe2)2), 1.37 (m, 2H, P(CHMe2)2), 0.85
(dd, 6H, JHꢀP = 10 Hz, JHꢀH = 9 Hz, PCH(CH3)2), 0.83 (dd, 6H, JHꢀP = 10 Hz, JHꢀH = 9 Hz, PCH(CH3)2) ,
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0.69 (dd, 12H, JHꢀP = 15 Hz, JHꢀH = 7 Hz, PCH(CH3)2); C{1H} NMR (C6D6): δ 160.0 (d, JCꢀP = 9 Hz,
ArꢀOP), 141.9 (d, JCꢀP = 8 Hz, ArꢀCH2OP), 129.6 (ArꢀH), 120.9 (ArꢀH), 118.0 (d, JCꢀP = 11 Hz, ArꢀH),
117.8 (d, JCꢀP = 11 Hz, ArꢀH), 74.4 (d, JCꢀP = 22 Hz, CH2OP), 28.7 (d, JCꢀP = 14 Hz, P(CHMe2)2), 28.5
(d, JCꢀP = 14 Hz, P(CHMe2)2), 18.2 (d, JCꢀP = 20 Hz, P(CHMe2)2), 17.8 (d, JCꢀP = 20 Hz, P(CHMe2)2),
17.3 (d, JCꢀP = 9 Hz, P(CHMe2)2), 17.2 (d, JCꢀP = 9 Hz, P(CHMe2)2).
Synthesis of (POCCH2OPiPr)Rh(H)(Cl)(NCCH3) (7-Rh(H)(Cl)(NCMe)). In a Teflon screwꢀtop
flask, 7-H (419 mg, 1.18 mmol) and [(COD)RhCl]2 (299 mg, 0.59 mmol) were dissolved in acetonitrile
and stirred overnight at 80 °C. The reaction mixture was passed through a pad of silica and Celite. The
volatiles were removed under vacuum and the resulting solid was recrystallized from pentane to produce
square yellow crystals judged to be >95% pure by 1H NMR spectroscopy (520 mg, 97%) 31P{1H} NMR
(C6D6): δ 186.4 (dd, JPꢀP = 428 Hz, JPꢀRh = 119 Hz), 153.9 (dd, JPꢀP = 416 Hz, JPꢀRh = 113 Hz); 1H NMR
(C6D6): δ 6.96 (d, 1H, J = 8 Hz, ArꢀH), 6.82 (t, 1H, J = 8 Hz, ArꢀH), 6.62 (d, 1H, J = 8 Hz, ArꢀH), 4.82
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ACS Catalysis
(m, 2H, CH2OP), 3.09 (m, 1H, CHMe2), 2.55 (m, 1H, CHMe2), 2.49 (m, 1H, CHMe2), 2.19 (m, 1H,
CHMe2), 1.62 (dd, 3H, CH(CH3)2, JHꢀP = 16 Hz, JHꢀH = 7 Hz), 1.57 (br m, 3H, CH(CH3)2), 1.39 (dd,
3H, CH(CH3)2, JHꢀP = 15 Hz, JHꢀH = 7 Hz), 1.31 (m, 6H, CH(CH3)2), 1.20 (m, 6H, CH(CH3)2), 0.82 (dd,
3H, CH(CH3)2, JHꢀP = 15 Hz, JHꢀH = 7 Hz), 0.52 (s, 3H, NCCH3), ꢀ17.95 (br s, 1H, RhꢀH); 13C{1H}
NMR (C6D6): δ 166.4 (d, JCꢀP = 13 Hz, ArꢀOP), 142.8 (d, JCꢀP = 9 Hz , ArꢀCH2OP), 137.0 (m, ArꢀRh),
124.2 (ArꢀH), 121.5 (ArꢀH), 121.2 (NCCH3), 111.5 (d, JCꢀP = 13 Hz, ArꢀH), 76.6 (s, CH2OP), 31.6 (m,
CHMe2), 29.4 (s, CHMe2), 29.1 (s, CHMe2), 27.7 (s, CHMe2), 18.6 (d, J = 5 Hz, CHMe2), 18.5 (s,
CHMe2), 18.2 (s, CHMe2), 18.0 (s, CHMe2), 17.3 (d, J = 3 Hz, CHMe2), 16.7 (d, J = 6 Hz, CHMe2), 16.5
(d, J = 9 Hz, CHMe2), 16.2 (s, CHMe2), 1.2 (s, NCCH3). Elem. Anal. Found (calculated) for
C21H37ClNO2P2Rh: C, 47.07 (47.07); H, 6.98 (6.96).
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Synthesis of (POCCH2OPiPr)Rh(H)(Cl) (7-Rh(H)(Cl)). In a Teflon screwꢀtop flask, 7-
Rh(H)(Cl)(NCMe) (261 mg, 0.483 mmol) was combined with sodium acetate (356 mg, 4.34 mmol) and
dissolved in 1,4ꢀdioxane. The reaction stirred overnight at 90 °C. The resulting orange solution was
passed through a pad of Celite and the volatiles were removed under vacuum to produce 7-Rh(H)(OAc)
as an oily brown solid, which was characterized in situ. The brown solid was dissolved in toluene and
trimethylsilyl chloride (100 ꢁL, 0.788 mmol) was added. The reaction mixture was stirred for 1 h at RT
and the volatiles were removed under vacuum. The oily orange solid produced was washed with
hexamethyldisiloxane and redissolved in toluene to be passed through a plug of Celite. The volatiles
were removed and the orange solid was dissolved in a minimum amount of toluene, layered with
pentane, and then placed in a ꢀ35 ⁰C freezer to produce an orange solid (118 mg, 49%). 31P{1H} NMR
(C6D6): δ 186.7 (dd, JPꢀP = 416 Hz, JPꢀRh = 118 Hz), 157.7 (dd, JPꢀP = 416 Hz, JPꢀRh = 121 Hz); 1H NMR
(C6D6): δ 6.96 (d, 1H, J = 7 Hz, ArꢀH), 6.86 (t, 1H, , J = 8 Hz, ArꢀH), 6.47 (d, 1H, J = 7 Hz, ArꢀH), 4.73
(dd, 1H, J = 17 Hz, J = 13 Hz, CH2OP), 4.55 (dd, 1H, J = 17 Hz, J = 13 Hz, CH2OP), 2.74 (m, 1H,
PCHMe2), 2.58 (m, 1H, PCHMe2), 2.27 (m, 1H, PCHMe2), 2.18 (m, 1H, PCHMe2), 1.32 (dd, 3H, JHꢀP
=
17 Hz, JHꢀH = 8 Hz, PCH(CH3)2), 1.28 (dd, 3H, JHꢀP = 18 Hz, JHꢀH = 8 Hz, PCH(CH3)2), 1.26 (dd, 3H,
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JHꢀP = 17 Hz, JHꢀH = 8 Hz, PCH(CH3)2), 1.20 (dd, 3H, JHꢀP = 18 Hz, JHꢀH = 7 Hz, PCH(CH3)2), 1.09 (dd,
3H, JHꢀP = 17 Hz, JHꢀH = 8 Hz, PCH(CH3)2), 1.07 (m, 6H, PCH(CH3)2), 1.05 (dd, 3H, JHꢀP = 16 Hz, JHꢀH
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= 7 Hz, PCH(CH3)2), ꢀ25.48 (br d, 1H, JHꢀRh = 45 Hz, RhꢀH); 13C{1H} NMR (C6D6): δ 168.7 (dd, JCꢀP
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13 Hz, JCꢀRh = 3.0 Hz, ArꢀOP), 142.3 (d, J = 8 Hz, ArꢀCH2OP), 133.9 (ddd, JCꢀRh = 29 Hz, JCꢀP = 7 Hz,
JCꢀP = 5 Hz, ArꢀRh), 125.6 (ArꢀH), 121.8 (ArꢀH), 112.4 (d, JCꢀP = 12 Hz, ArꢀH), 76.4 (d, JCꢀP = 2 Hz,
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CH2OP), 29.3 (m, PCHMe2), 29.0 (m, PCHMe2), 28.6 (m, PCHMe2), 28.3 (m, PCHMe2), 19.3 (d, JCꢀP
=
4 Hz, PCH(CH3)2), 18.3 (s, PCH(CH3)2), 18.2 (d, JCꢀP = 7 Hz, PCH(CH3)2), 18.0 (d, JCꢀP = 5 Hz,
PCH(CH3)2), 17.9 (s, PCH(CH3)2), 17.1 (d, JCꢀP = 8 Hz, PCH(CH3)2), 16.4 (apparent t (dd), J = 2 Hz,
PCH(CH3)2), 16.1 (dd, J = 4 Hz, J = 2 Hz, PCH(CH3)2). Elem. Anal. Found (calculated) for
C19H34ClO2P2Rh: C, 46.03 (46.12); H, 6.94 (6.93).
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(POCCH2OPiPr)Rh(H)(OAc) (7-Rh(H)(OAc)): P{1H} NMR (C6D6): δ 187.1 (dd, JPꢀP = 416 Hz,
JPꢀRh = 123 Hz), 150.5 (dd, JPꢀP = 416 Hz, JPꢀRh = 119 Hz); 1H NMR (C6D6): δ 6.92 (d, 1H, J = 8 Hz, Arꢀ
H), 6.80 (t, 1H, J = 7 Hz, ArꢀH), 6.51 (d, 1H, J = 8 Hz, ArꢀH), 5.01 (dd, 1H, JHꢀP = 8 Hz, JHꢀH = 12,
CH2OP), 4.65 (dd, 1H, JHꢀP = 29 Hz, JHꢀH = 12 Hz, CH2OP), 2.38 (m, 1H, CHMe2), 2.29 (m, 1H,
CHMe2), 2.21 (m, 1H, CHMe2), 2.06 (m, 1H, CHMe2), 1.93 (s, 3H, O2CCH3), 1.49 (dd, 3H, JHꢀP = 14
Hz, JHꢀH = 8 Hz, CH(CH3)2), 1.31 (dd, 3H, JHꢀP = 15 Hz, JHꢀH = 8 Hz, CH(CH3)2), 1.23 (dd, 3H, JHꢀP = 18
Hz, JHꢀH = 7 Hz, CH(CH3)2), 1.17 (dd, 3H, JHꢀP = 18 Hz, JHꢀH = 7 Hz, CH(CH3)2), 1.16 (dd, 3H, JHꢀP = 15
Hz, JHꢀH = 8 Hz, CH(CH3)2), 1.15 (dd, 3H, JHꢀP = 15 Hz, JHꢀH = 8 Hz, CH(CH3)2), 0.97 (dd, 3H, JHꢀP = 18
Hz, JHꢀH = 7 Hz, CH(CH3)2), 0.89 (dd, 3H, JHꢀP = 16 Hz, JHꢀH = 8 Hz, CH(CH3)2), ꢀ21.05 (ddd, JHꢀRh
27 Hz, JHꢀP = 15 Hz, JHꢀP = 12 Hz, RhꢀH); 13C{1H} NMR (C6D6): δ 183.2 (s, O2CCH3), 167.6 (dd, JCꢀP
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13 Hz, JCꢀRh = 3 Hz, ArꢀOP), 142.2 (d, JCꢀP = 7 Hz, ArCH2OP), 133.5 (br d, JCꢀRh = 31 Hz, ArꢀRh), 124.2
(Ar-H), 121.8 (ArꢀH), 111.5 (d, J = 11 Hz, ArꢀH), 76.6 (s, CH2OP), 31.0 (apparent t (dd), J = 10 Hz,
CHMe2), 28.6 (ddd, JCꢀP = 26 Hz, J = 2 Hz, J = 2 Hz, CHMe2); 28.4 (apparent t (dd), J = 10 Hz,
CHMe2), 28.19 (apparent t (dd), J = 3 Hz, CHMe2), 24.4 (s, O2CCH3), 18.2 (s, CHMe2), 18.0 (d, JCꢀP = 3
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Hz, CHMe2), 17.8 (s, CHMe2), 17.4 (d, JCꢀP = 9 Hz, CHMe2), 16.9 (d, JCꢀP = 6 Hz, CHMe2), 16.5 (s,
CHMe2), 16.4 (dd, JCꢀP = 4 Hz, JCꢀRh = 1 Hz, CHMe2), 16.2 (d, JCꢀP = 10 Hz, CHMe2).
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Rh(H)(Cl) (118 mg, 0.238 mmol) was dissolved in toluene with NaOtBu (40 mg, 0.363 mmol).
Diisopropyl sulfide (50 ꢁL, 0.344 mmol) was added and the mixture was stirred overnight at RT. The
volatiles were removed under vacuum and the brown solid was dissolved in pentane and filtered through
silica and Celite. The volatiles were removed under vacuum and the reaction mixture was dissolved in a
minimum amount of diethyl ether and placed in a ꢀ35 ⁰C freezer to precipitate the product as a reddishꢀ
brown solid. (16.3 mg, 46%). Although this material appears to be pure by NMR spectroscopy, we have
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been unable to obtain satisfactory elemental analysis data. 31P{1H} NMR (C6D6): δ 186.7 (dd, JPꢀP
=
345 Hz, JPꢀRh = 174 Hz), 151.7 (dd, JPꢀP = 347 Hz, JPꢀRh = 176 Hz); 1H NMR (C6D6): δ 7.17 (d, 1H, J = 8
Hz, ArꢀH), 6.96 (t, 1H, J = 7 Hz, ArꢀH), 6.70 (d, 1H, J = 8 Hz, ArꢀH), 4.92 (d, 2H, JHꢀP = 19 Hz,
CH2OP), 2.77 (m, 2H, S(CHMe2)2), 2.23 (overlapping m, 4H, P(CHMe2)2), 1.30 (dd, 6H, JHꢀP = 16 Hz,
JHꢀH = 7 Hz, P(CH(CH3)2)2), 1.26 (d, 12H, JHꢀH = 7 H, S(CH(CH3)2)2), 1.25 (dd, 6H, JHꢀP = 12 Hz, JHꢀH
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7 Hz, P(CH(CH3)2)2), 1.22 (dd, 6H, JHꢀP = 16 Hz, JHꢀH = 7 Hz, P(CH(CH3)2)2), 1.08 (dd, 6H, JHꢀP = 12
Hz, JHꢀH = 7 Hz, P(CH(CH3)2)2); 13C{1H} NMR (C6D6): δ 168.33 (d, JCꢀP = 18 Hz, ArꢀOP), 146.38 (m,
ArꢀRh), 144.38 (d, JCꢀP = 13 Hz, ArꢀOP), 123.68 (ArꢀH), 120.04 (ArꢀH), 110.32 (d, JCꢀP = 14 Hz, ArꢀH),
78.50 (d, JCꢀP = 6 Hz, CH2OP), 41.95 (s, S(CHMe2)2), 37.60 (m (overlapping signals), P(CHMe2)2),
30.95 (m, P(CHMe2)2), 28.96 (dd, JCꢀP = 20 Hz, JCꢀRh = 3 Hz, P(CHMe2), 24.49 (s, S(CHMe2)2), 19.05
(dd, JCꢀP = 9 Hz, JCꢀRh = 1 Hz, P(CH(CH3)2), 18.19 (dd, JCꢀP = 8 Hz, JCꢀRh = 3 Hz, P(CH(CH3)2), 17.81
(s, P(CH(CH3)2), 17.42 (s, P(CH(CH3)2).
Synthesis of (POCCH2OPiPr)Rh(CO) (7-Rh(CO)). In a Teflon capped 10 mL flask, 7-Rh(SiPr2)
(200 mg, 0.35 mmol) was dissolved in toluene and degassed. The flask was then filled with CO and
stirred for 2 h at RT. The reaction mixture was then filtered through Celite and silica and the volatiles
were removed under vacuum. The resulting yellow solid was then dissolved in pentane and placed in a ꢀ
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35 °C freezer to produce yellow crystals judged to be >97% pure by H NMR (97 mg, 57% yield).
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PCHMe2), 1.20 (dd, 6H, PCH(Me)2, JHꢀP = 17.5 Hz, JHꢀH = 7.5 Hz), 1.15 (dd, 6H, PCH(Me)2, JHꢀP = 14.5
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Hz, JHꢀH = 7 Hz), 1.15 (dd, 6H, PCH(Me)2, JHꢀP = 17.5 Hz, JHꢀH = 7 Hz), 1.07 (dd, 6H, PCH(Me)2, JHꢀP
=
13.5 Hz, JHꢀH = 7 Hz); 13C{1H} NMR (C6D6): δ 197.35 (ddd, JRhꢀC = 56 Hz, JPꢀC = 14 Hz, JPꢀC = 13 Hz,
RhꢀCO), 169.88 (dd, JCꢀP = 16 Hz, JCꢀRh = 3 Hz, ArꢀOP), 148.04 (ddd, JRhꢀC = 29 Hz, JCꢀP = 10 Hz, JCꢀP
9 Hz, CꢀRh), 143.02 (d, JCꢀP = 11 Hz, ArꢀCH2OP), 127.51 (s, ArꢀH), 120.35 (s, ArꢀH), 111.37 (d, JCꢀP
=
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14 Hz, ArꢀH), 77.75 (t, JCꢀP = 3 Hz, CH2OP), 31.6 (ddd, JCꢀP = 26 Hz, J = 3 Hz, J = 2 Hz, PCHMe2),
30.69 (ddd, JCꢀP = 22 Hz, J = 4 Hz, J = 3 Hz, PCHMe2), 18.55 (d, JCꢀP = 4 Hz, P(CHMe2)2), 18.48 (s, JCꢀ
P = 5 Hz, P(CHMe2)2) 17.75 (s, P(CHMe2), 17.50 (s, P(CHMe2). IR: 1948 cmꢀ1, νCO.
Synthesis of 1-(tBu2PO)-3-(tBu2POCH2)(C6H4) (8-H). To a solution of 3ꢀhydroxybenzyl alcohol
(0.320 g, 2.64 mmol) in THF, sodium hydride (0.189 g, 7.71 mmol) was added slowly while stirring.
The mixture was refluxed for 1 h, and a solution of ClPtBu2 (0.949 g, 5.25 mmol) in THF was added
dropwise. The reaction was refluxed overnight. The volatiles were removed under vacuum and the
residue was extracted with toluene and filtered through Celite. The solvent was removed under vacuum
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to give a colorless oil determined to be >95% pure by H NMR spectroscopy (0.907 g, 2.20 mmol,
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83%). P{1H} NMR (C6D6): δ 164.6 (s), 153.2 (s); H NMR (C6D6): δ 6.83 (d, 1H, J = 8 Hz, ArꢀH)
6.80 (s, 1H, ArꢀH), 6.74 (t, 1H, J = 8 Hz, ArꢀH), 6.58 (d, 1H, J = 7 Hz, ArꢀH), 4.42 (d, 2H, J = 8 Hz,
CH2OP), 0.78 (d, 18H, JHꢀP = 12 Hz, PC(Me3)2), 0.76 (d, 18H, JHꢀP = 12 Hz, PC(Me3)2); 13C{1H} NMR
(C6D6): δ 160.48 (d, JCꢀP = 9 Hz, ArꢀOP), 141.80 (d, JCꢀP = 9 Hz, Ar-CH2OP), 120.53 (s, ArꢀH), 117.77
(d, JCꢀP = 10 Hz, ArꢀH), 117.54 (d, JCꢀP = 11 Hz, ArꢀH), 75.68 (d, JCꢀP = 23 Hz, CH2OP), 35.73 (d, JCꢀP
27 Hz, P(CMe3)2), 35.41 (d, JCꢀP = 26 Hz, P(CMe3)2), 27.69 (d, JCꢀP = 16 Hz, P(CMe3)2), 27.57 (d, JCꢀP
=
=
17 Hz, P(CMe3)2). HRMS (ESI+TOF) m/z: [M + H]+ Calcd. for C23H44O2P2 413.2733; found 413.2750.
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ACS Catalysis
Synthesis of (POCCH2OPtBu)Rh(H)(Cl) (8-Rh(H)(Cl)). In a Teflon screwꢀtop flask, 8-H (244 mg,
0.591 mmol) and [(COD)RhCl]2 (146 mg, 0.296 mmol) were dissolved in toluene and heated at 90 °C
for 18 h. The reaction mixture was passed through silica and Celite and recrystallized from toluene and
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pentane to produce greenishꢀyellow crystals judged to be >97% pure by H NMR spectroscopy (198
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mg, 61%). P{1H} NMR (C6D6): δ 188.6 (dd, JPꢀP = 398 Hz, JPꢀRh = 117 Hz), 161.7 (dd, JPꢀP = 398 Hz,
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PꢀRh = 117 Hz); 1H NMR (C6D6): δ 6.97 (d, 1H, J = 8 Hz, ArꢀH), 6.89 (t, 1H, J = 7 Hz, , ArꢀH), 6.49 (d,
1H, J = 7 Hz, ArꢀH), 4.73 (dd, 1H, JHꢀP = 16 Hz, JHꢀH = 13 Hz, CH2OP), 4.57 (dd, 1H, JHꢀP = 17 Hz, JHꢀH
= 13 Hz, CH2OP), 1.41 (d, 9H, JHꢀP = 14 Hz, PC(Me3)2), 1.40 (d, 9H, JHꢀP = 13 Hz, PC(Me3)2), 1.39 (d,
9H, JHꢀP = 14 Hz, PC(Me3)2), ꢀ26.84 (apparent dt, 1H, JHꢀRh = 50 Hz, JHꢀP = 12 Hz); 13C{1H} NMR
(C6D6): δ 169.7 (dd, JCꢀP = 12 Hz, JCꢀRh= 3 Hz, ArꢀOP), 142.1 (d, JCꢀP = 6 Hz , ArꢀCH2OP), 134.2 (m, Arꢀ
Rh), 125.7 (ArꢀH), 121.5 (ArꢀH), 112.2 (d, JCꢀP = 12 Hz, ArꢀH), 75.9 (d, JCꢀP = 3 Hz, CH2OP,), 41.3 (dd,
JCꢀP = 10 Hz, JCꢀRh = 6 Hz, PCMe3), 40.6 (dd, JCꢀP = 10 Hz, JCꢀRh = 7 Hz, PCMe3), 39.7 (ddd, JCꢀP = 18
Hz, JCꢀRh = 6 Hz, JCꢀP = 2 Hz, PCMe3), 38.9 (ddd, JCꢀP = 13 Hz, JCꢀRh = 6 Hz, JCꢀP = 3Hz, PCMe3), 29.4
(d, JCꢀP = 5 Hz, PCMe3), 29.2 (d, JCꢀP = 5 Hz, PCMe3), 28.15 (d, JCꢀP = 5 Hz, PCMe3), 28.08 (d, JCꢀP = 5
Hz, PCMe3).
Synthesis of (POCCH2OPtBu)Rh(SiPr2) (8-Rh(SiPr2)). In a Teflon screwꢀcap vial, 8-Rh(H)(Cl)
(150 mg, 0.273 mmol), NaOtBu (45 mg, 0.41 mmol), and diisopropylsulfide (80 ꢁL, 0.546 mmol) were
dissolved in toluene and stirred overnight at RT. The reaction mixture was passed through Celite, and
then the volatiles were removed under vacuum yielding a brown solid, which was recrystallized from
pentane (138 mg, 80%). P{1H} NMR (C6D6): δ 189.3 (dd, JPꢀP = 335 Hz, JPꢀRh = 184 Hz), 160.9 (dd,
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JPꢀP = 331 Hz, JPꢀRh = 176 Hz); 1H NMR (C6D6): δ 6.96 (d, 1H, J = 8 Hz, ArꢀH), 6.86 (t, 1H, J = 8 Hz,
ArꢀH), 6.63 (d, 1H, J = 7 Hz, ArꢀH), 4.87 (d, 2H, JHꢀP = 19 Hz, CH2OP), 2.85 (m, 2H, S(CHMe2)2), 1.44
(d, 18H, JHꢀP = 12 Hz, P(CMe3)2), 1.28 (d, 18H, JHꢀP = 12 Hz, P(CMe3)2), 1.29 (d, 12 H, J = 7 Hz,
S(C(Me2)2)2); 13C{1H} NMR (C6D6): δ 168.4 (d, JCꢀP = 15 Hz, ArꢀOP), 145.2 (m, ArꢀRh), 143.9 (d, JCꢀP
= 9 Hz, ArꢀCH2OP), 123.1 (ArꢀH), 120.0 (ArꢀH), 110.2 (d, JCꢀP = 12 Hz, ArꢀH), 78.3 (d, JCꢀP = 5 Hz,
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CH2OP), 40.9 (s, S(CHMe2)2), 40.2 (m, PC(CH3)3), 39.8 (dd, JCꢀP = 10 Hz, JCꢀRh = 4 Hz, PC(CH3)3),
37.6 (s, PC(CH3)3), 29.8 (d, JCꢀP = 8 Hz, P(CMe3)2), 29.7 (d, JCꢀP = 8 Hz, P(CMe3)2), 25.5 (s,
S(CHMe)2). Elem. Anal. Found (Calculated) for C29H55O2P2RhS: C, 55.09 (55.06); H, 8.57 (8.76); S,
4.93 (5.07).
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Synthesis of (POCCH2OPtBu)Rh(CO) (8-Rh(CO)). In a Teflon capped 10 mL flask, 8-Rh(SiPr2)
(65 mg, 0.104 mmol) was dissolved in toluene and degassed. The flask was then filled with CO and
stirred for 2 h at RT. The reaction mixture was filtered through silica and Celite and the volatiles were
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removed under vacuum, resulting in a yellow solid judged to be >98% pure by H NMR (34 mg, 61%
yield). 31P{1H} NMR (C6D6): δ 210.6 (dd, JPꢀP = 300 Hz, JPꢀRh = 144 Hz), 177.2 (dd, JPꢀP = 300 Hz, JPꢀRh
= 150 Hz); 1H NMR (C6D6): δ 7.14 (d, 1H, J = 8 Hz, ArꢀH), 6.99 (dt, 1H, J = 8 Hz, JHꢀP = 1 Hz, 1H, Arꢀ
H), 6.61 (d, 1H, J = 8 Hz, ArꢀH), 4.78 (d, 2H, JCꢀP = 17 Hz, CH2OP), 1.33 (d, 18H, JCꢀP = 14 Hz,
P(CMe3)2), 1.30 (d, 18H, JCꢀP = 14 Hz, P(CMe3)2); 13C{1H} NMR (C6D6): 199.2 (apparent dt (ddd), JCꢀRh
= 57 Hz, JCꢀP = 14 Hz, RhꢀCO), 170.8 (dd, JCꢀP = 15 Hz, JCꢀRh = 3 Hz, ArꢀOP), 148.6 (apparent dt (ddd),
JCꢀRh = 29 Hz, JCꢀP = 10 Hz, ArꢀRh) 142.5 (d, JCꢀP = 10 Hz, ArꢀCH2OP), 127.3 (s, ArꢀH), 120.0 (s, ArꢀH),
111.2 (d, J = 14 Hz), 77.4 (dd, JCꢀP = 3 Hz, JCꢀRh = 1 Hz, CH2OP), 39.9 (m, contains both P(CMe3)2
signals), 28.9 (d, JCꢀP = 7 Hz, P(CMe3)2), 28.7 (d, JCꢀP = 7 Hz, P(CMe3)2). IR: 1943 cmꢀ1, νCO.
Synthesis of 2,2’4,4’-tetramethyldiphenylamine (A). In a 250 mL Schlenk flask, 2,4ꢀ
dimethylaniline (5.84 mL, 48 mmol), 2,4ꢀdimethylbromobenzene (6.08 mL, 45 mmol),
bis(diphenylphosphino)ferrocene (DPPF, 0.498 g, 0.90 mmol), Pd(OAc)2 (0.100 g, 0.45 mmol Pd), and
NaOCMe2Et (7.06 g, 63 mmol) were refluxed in ca. 100 mL of toluene under argon. After 16 h, the
mixture was filtered through silica and Celite and the filtrate was collected. All of the volatiles were
removed under vacuum and a product judged to be >98% pure by 1H NMR recrystallized from pentane.
Yield: 7.51 g (74%). 1H NMR (CDCl3): δ 7.08 (s, 2H, ArꢀH), 6.98 (d, 2H, J = 8 Hz, ArꢀH), 6.90 (d, 2H,
J = 8 Hz, ArꢀH), 5.11 (br s, 1H, NꢀH), 2.36 (s, 6H, ArꢀCH3), 2.30 (s, 6H, ArꢀCH3); 13C{1H} NMR
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ACS Catalysis
(CDCl3): δ 139.9 (s, NꢀAr), 131.6 (s, ArꢀH), 130.8 (s, ArꢀMe), 127.76 (s, ArꢀMe), 127.75 (s, ArꢀH),
118.7 (s, ArꢀH), 20.8 (s, ArꢀMe), 17.9 (s, ArꢀMe).
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Synthesis of 2,2’-dibromo-4,4’,6,6’-tetramethyldiphenylamine (B). In a Schlenk flask under
ambient atmosphere, A (7.44 g, 33 mmol) was dissolved in dichloromethane. Nꢀbromosuccinimide
(11.75 g, 66 mmol) was added slowly and the reaction mixture was left to stir overnight at RT. The
reaction mixture was then passed through Celite and the volatiles were removed by vacuum. The
resulting brown solid was dissolved in pentane and filtered through silica and Celite. The volatiles were
removed, and a white solid was obtained by recrystallizing the product from ethanol. The purity of
product judged to be >97% by 1H NMR spectroscopy. Yield: 8.91 g (70%). 1H NMR (CDCl3): δ 7.24 (s,
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2H, ArꢀH), 6.81 (s, 2H, ArꢀH), 5.49 (br s, 1H, NꢀH), 2.42 (s, ArꢀMe), 1.80 (s, ArꢀMe); C{1H} NMR
(CDCl3): δ 137.9 (s, ArꢀN), 133.1, 132.1, 131.4, 131.0, 118.4 (s, ArꢀBr), 20.5 (s, ArꢀMe), 19.7 (s, Arꢀ
Me).
Synthesis of N-methyl-2,2’-dibromo-4,4’,6,6’-tetramethyldiphenylamine (C). In a Schlenk flask,
B (1.26 g, 3.3 mmol) was dissolved in THF and treated with KN(SiMe3)2 (5 mL, 3.3 mmol, 0.66 M in
toluene). The solution was stirred at RT for 2 h and iodomethane (410 ꢁL, 6.6 mmol) was added. The
solution was stirred overnight at RT and filtered through Celite and silica gel. The product was isolated
as a yellow solid after recrystallizing from pentane. The purity of the product was judged to be >97%
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pure by H NMR. Yield: 767 mg (58%). 1H NMR (C6D6): δ 7.25 (s, 2H, ArꢀH), 6.56 (s, 2H, ArꢀH),
3.49 (s, 3H, NꢀMe), 1.98 (s, 6H, ArꢀMe), 1.90 (s, 6H, ArꢀMe). 13C{1H} NMR (C6D6): δ 143.6 (s, ArꢀN),
137.0 (s, Ar), 134.3 (s, Ar), 133.9 (s, Ar), 132.6 (s, Ar), 121.2 (s, ArꢀBr), 43.5 (s, NMe), 20.9 (s, ArꢀMe),
20.1 (s, ArꢀMe).
Synthesis of (o-MePNP)Me (9-Me). In a Schlenk flask, C (752 mg, 1.89 mmol) was dissolved in Et2O
and nꢀBuLi (1.6 mL of 2.5M solution in hexanes, 4.0 mmol) was added slowly. The mixture was stirred
for 2 h at RT and ClPiPr2 (635 mg, 4.16 mmol) was added slowly. The reaction was allowed to stir
overnight and the volatiles were removed under vacuum. The dry solid was dissolved in toluene and
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passed through a pad of Celite. Pure product was recrystallized from Et2O to form a white solid (418
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mg, 45%). P{1H} NMR (C6D6): δ ꢀ2.28; H NMR (C6D6): δ 7.10 (s, 2H, ArꢀH), 6.85 (s, 2H, ArꢀH),
3.58 (s, 3H, NꢀMe), 2.40 (s, 6H, ArꢀMe), 2.18 (s, 6H, ArꢀMe), 1.93 (m, 2H, P(CHMe2)2), 1.59 (m, 2H,
P(CHMe2)2), 1.12 (dd, 6H, JHꢀP = 11 Hz, JHꢀH = 7 Hz, P(CHMe2)2), 1.11 (dd, 6H, JHꢀP = 13 Hz, JHꢀH = 7
Hz, P(CHMe2)2), 0.93 (dd, 6H, JHꢀP = 14 Hz, JHꢀH = 7 Hz, P(CHMe2)2), 0.87 (dd, 6H, JHꢀP = 12 Hz, JHꢀH
= 7 Hz, P(CHMe2)2); 13C{1H} NMR (C6D6): δ 154.5 (m, ArꢀN), 134.8 (m, Ar), 134.76 (s, Ar), 133.8 (m,
ArꢀP), 132.5 (s, Ar), 131.7 (s, Ar), 46.7 (m, NꢀMe), 25.6 (m, PCHMe2), 25.4 (m, PCHMe2), 23.8 (t, JCꢀP
= 9 Hz, PCHMe2), 22.3 (t, JCꢀP = 10 Hz, PCHMe2), 21.2 (t, JCꢀP = 8 Hz, PCHMe2), 21.0 (t, JCꢀP = 8 Hz,
PCHMe2), 20.7 (s, ArꢀMe), 19.4 (t, JCꢀP = 7 Hz, ArꢀMe). Elem. Anal. Found (Calculated) for
C29H47NP2: C, 73.75 (73.85); H, 10.15 (10.04).
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Synthesis of (o-MePNP)Rh(Me)(Cl) (9-Rh(Me)(Cl)). In a J. Young tube, 9-Me (104 mg, 0.22 mmol)
and [Rh(COE)2Cl] (79 mg, 0.11 mmol) were dissolved in C6D6 and the solution was heated at 70 °C for
18 h. The reaction mixture was filtered through Celite and silica and recrystallized from THF to produce
a green solid judged to be >95% pure by H NMR spectroscopy (44 mg, 33% yield). 31P{1H} NMR
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(C6D6): δ 35.9 (dd, JPꢀP = 414 Hz, JPꢀRh = 111 Hz), 29.3 (dd, JPꢀP = 415 Hz, J = 109 Hz); H NMR
(C6D6): δ 6.84 (d, 1H, JHꢀP = 8 Hz, ArꢀH), 6.73 (d, 1H, JHꢀP = 6 Hz, ArꢀH), 6.66 (s, 1H, ArꢀH), 2.89 (m,
1H, P(CHMe2)2), 2.46 (m, 3H, RhꢀMe), 2.50ꢀ2.36 (m, 2H, overlapping P(CHMe2)2), 2.26 (m, 1H,
P(CHMe2)2), 2.19 (s, 3H, ArꢀMe), 2.16 (s, 3H, ArꢀMe), 1.72 (s, 3H, ArꢀMe), 1.62 (dd, 3H, JHꢀP = 15 Hz,
JHꢀH = 7 Hz, P(CHMe2)2), 1.61 (s, 3H, ArꢀMe), 1.38 (dd, 3H, JHꢀP = 15 Hz, JHꢀH = 7 Hz, P(CHMe2)2),
1.25 (dd, 3H, JHꢀP = 16 Hz, JHꢀH = 7 Hz, P(CHMe2)2), 1.20 (dd, 3H, JHꢀP = 16 Hz, JHꢀH = 7 Hz,
P(CHMe2)2), 1.16 (dd, 3H, JHꢀP = 15 Hz, JHꢀH = 7 Hz, P(CHMe2)2), 1.11 (dd, 3H, JHꢀP = 14 Hz, JHꢀH = 8
Hz, P(CHMe2)2), 1.06 (dd, 3H, JHꢀP = 13 Hz, JHꢀH = 7 Hz, P(CHMe2)2), 1.57 (dd, 3H, JHꢀP = 13 Hz, JHꢀH
= 6 Hz, P(CHMe2)2); C{1H} NMR (C6D6): δ 162.5 (d, J = 19 Hz, ArꢀN), 162.1 (d, J = 19 Hz, ArꢀN),
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135.3, 134.0, 129.8, 129.5, 129.3 (d, J = 11 Hz), 126.4 (d, J = 7 Hz), 126.3 (d, J = 10 Hz), 125.2 (d, J =
7 Hz), 123.4 (d, J = 39 Hz, ArꢀP), 119.0 (d, J = 39 Hz, ArꢀP), 27.3(m, PCHMe2), 26.6 (m, PCHMe2),
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ACS Catalysis
25.2 (m, PCHMe2), 23.6 (m, PCHMe2), 21.7, 21.1, 20.94, 20.91, 20.7, 20.6, 19.3, 19.0 (d, J = 4 Hz),
18.8, 18.7 (d, J = 4 Hz), 18.3, 17.8, 2.8 (br d, JCꢀRh = 29 Hz, RhꢀMe).
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Synthesis of (o-MePNP)Rh(H2) (9-Rh(H2)). In a Schlenk flask (9-Rh(Me)(Cl)) (180 mg, 0.30 mmol)
and NaBH4 (30 mg, 0.79 mmol) was dissolved in degassed isopropanol and the reaction was stirred for
3 h at RT. The volatiles were removed and the resulting solid was dissolved in diethyl ether and passed
through a pad of Celite and the volatiles were removed under vacuum. Orange crystals were formed (60
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mg, 33%) by slow diffusion of pentane into a saturated toluene solution. P{1H} NMR (C6D6): δ 58.4
(d, JPꢀRh = 130 Hz); 1H NMR (C6D6): δ 6.79ꢀ6.77 (m, 4H, overlapping ArꢀH), 2.23 (s, 6H, ArꢀMe), 2.04
(m, 2H, P(CHMe2)2), 1.96 (m, 2H, P(CHMe2)2), 1.81 (s, 6H, ArꢀMe), 1.41 (apparent q (dvt), 6H, J = 8
Hz, P(CHMe2)2), 1.11 (apparent q (dvt), 6H, J = 7 Hz, P(CHMe2)2), 0.99 (apparent q (dvt), 6H, J = 8
Hz, P(CHMe2)2), 0.93 (apparent q (dvt), 6H, J = 8 Hz, P(CHMe2)2), ꢀ13.4 (dvt, 2H, JRhꢀH = 20 Hz, JPꢀH
=
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9 Hz, RhꢀH2); C{1H} NMR (C6D6): δ 163.8 (dvt, JCꢀP = 12 Hz, JCꢀRh = 2 Hz, ArꢀN), 134.8 (s, ArꢀH),
129.4 (s, ArꢀH), 125.1 (dvt, JCꢀP = 5 Hz, JCꢀRh = 1 Hz, ArꢀMe), 124.9 (vt, J = 4 Hz, ArꢀMe), 122.5 (vt, J =
18 Hz, ArꢀP), 28.0 (dvt, JCꢀRh = 2 Hz, JCꢀP = 10 Hz, P(CHMe2)2, 22.2 (vt, JCꢀP = 13 Hz, P(CHMe2)2),
21.74 (vt, JCꢀP = 4 Hz, P(CHMe2)), 21.68 (s, ArꢀMe), 20. 7 (s, ArꢀMe), 19.4 (vt, JCꢀP = 3 Hz, ,
P(CHMe2)), 18.9 (vt, JCꢀP = 5 Hz, P(CHMe2)), 18.1 (s, P(CHMe2)). Elem. Anal. Found (Calculated) for
C28H46NP2Rh: C, 59.71(59.89); H, 8.07 (8.26).
Observation of (o-MePNP)Rh(HD) (9-Rh(HD)). (9-Rh(Me)(Cl)) (64 mg, 0.11 mmol) and NaBH4 (22
mg, 0.57 mmol) was combined in a mixture of C6D6 and d4ꢀmethanol and stirred at room temperature
for 4 h. The volatiles were removed under vacuum and the product was extracted with diethyl ether and
filtered through a pad of Celite. The volatiles were removed under vacuum, and the solid was washed
with pentane. A mixture containing >85% of (9-Rh(HD)) and (9-Rh(H2)) by 31P{1H} NMR was
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produced. Data for the 1H signal of the H in HD in 9-Rh(HD) follow. H NMR (C6D6): δ ꢀ13.33 (dtvt,
JRhꢀH = 20 Hz, JHꢀD = 20 Hz, JHꢀP = 9 Hz).
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