Comparing the asymmetric dppf-type ligands with their semi-homologous counterparts

Journal of Organometallic Chemistry 860 (2018) 14e29

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Journal of Organometallic Chemistry

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Comparing the asymmetric dppf-type ligands with their

semi-homologous counterparts^*

*

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ꢁ

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Petr Vosahlo, Ivana Císarova, Petr Stepnicka

Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic

a r t i c l e i n f o

a b s t r a c t

Article history:

Two series of asymmetric ferrocene diphosphines, namely the dppf-type ligands R₂PfcPPh₂(protected as

BH₃adducts; fc ¼ ferrocene-1,1⁰-diyl) and their semi-homologous counterparts R₂PfcCH₂PPh₂(both in

free and BH₃-protected form), with diverse PR₂groups (R ¼ cyclohexyl, isopropyl and tert-butyl), were

prepared and further converted into the respective phosphine selenides, R₂P(Se)fcP(Se)Ph₂and R₂P(Se)

fcCH₂P(Se)Ph₂, which were in turn used to evaluate the electronic properties of these diphosphines

Received 13 December 2017

Received in revised form

7 January 2018

Accepted 8 January 2018

Available online 31 January 2018

1

through J_SePcoupling constants. When reacted with [PdCl₂(MeCN)₂] or [PdCl₂(cod)] (cod ¼ cycloocta-

1,5-diene), the dppf-type ligands exclusively afforded the chelate complexes [PdCl₂(R₂PfcPPh₂-k²P,P⁰)],

whereas the more ﬂexible, homologous ligands produced mixtures mainly containing the similar chelate

Keywords:

Ferrocene ligands

Phosphines

Homologous ligands

Palladium complexes

Structure elucidation

complexes [PdCl₂(R₂PfcCH₂PPh₂-k²P,P⁰)] and the P,P⁰-bridged dimers [PdCl₂( (P,P⁰)-R₂PfcCH₂PPh₂)]2.

m

1. Introduction

similarly modiﬁed phosphinoferrocene donors [5] revealed

considerable changes in coordination properties associated with

increased molecular ﬂexibility. These results and our recent ﬁnd-

ings demonstrating that even simple variations of substituents at

the phosphine groups can markedly affect the coordination and

catalytic behavior of phosphinoferrocene donors [6] have led us to

investigate parallel series of dppf and type-2 ligands with different

phosphine substituents (Scheme 1). The properties of these

diphosphines were compared by preparing and structurally char-

acterizing Pd(II) complexes with these ligands and by analyzing the

¹J_SePscalar coupling constants of the corresponding phosphine

diselenides [7].

1,1⁰-Bis(diphenylphosphino)ferrocene (1; dppf) has become a

truly iconic ferrocene ligand thanks to its unique coordination

properties and numerous successful catalytic applications [1,2],

which also triggered the search for analogous donors. Thus far,

most attempts to modify the dppf structure have followed three

main directions, namely (1) altering phosphine substituents, (2)

replacing one of the phosphine groups by another functional

moiety, and (3) introducing an additional substituent to the ferro-

cene core to provide planar-chiral ferrocene ligands. These ap-

proaches have already generated a vast family of ferrocene

phosphines applicable as supporting ligands in coordination com-

pounds and in a range of simple and enantioselective metal-

catalyzed transformations [3].

2. Results and discussion

Recently, we introduced an alternative approach to the design of

ferrocene phosphines based on ligand desymmetrization by

inserting a spacer group between the ferrocene scaffold and a

directly bonded donor substituent. In the case of dppf, this

approach using a simple methylene spacer led to its congener 2 [4]

(Scheme 1). Coordination studies with this ligand and other,

2.1. Synthesis and characterization of dppf-type diphosphines and

their derivatives

Asymmetric, dppf-like diphosphines with one PPh₂substituent

replaced by a dicyclohexylphosphino, diisopropylphosphino or di-

tert-butylphosphino moiety were prepared by lithiation/phosphi-

nylation of 1⁰-(diphenylphosphino)-1-bromoferrocene [8,9] and

were isolated as air-stable borane adducts 3a-c (Scheme 2) rather

than the corresponding, oxidation-sensitive phosphines 1a-c [10].

This procedure typically afforded minor amounts of FcPPh₂,BH₃

(Fc ¼ ferrocenyl) resulting from unwanted protonolysis of the

*

dppf ¼ 1,1⁰-bis(diphenylphosphino)ferrocene.

* Corresponding author.

ꢁ

E-mail address: petr.stepnicka@natur.cuni.cz (P. Stepnicka).

https://doi.org/10.1016/j.jorganchem.2018.01.009

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

15

Compounds 3e5 were characterized by multinuclear NMR

spectroscopy, electrospray ionization mass spectrometry (ESI MS)

and elemental analysis. The ¹H and ¹³C NMR spectra of 3e5

comprise the characteristic signals of the asymmetrically 1,1⁰-

disubstituted ferrocene moiety and of the phosphine moieties. The

presence of the protecting BH₃groups in compounds 3a-c is indi-

cated by very broad, structured resonances due to six BH protons in

the ¹H NMR spectra and broad, doublet-like signals in the ³¹P{¹H}

NMR spectra. The signals of the PPh₂,BH₃moieties are found at

d_Pz 16.3, whereas those of the other phosphine substituents

appear at lower ﬁelds (3a: d_P24.4, 3b: d_P31.8, and 3c: d_P45.4). Upon

conversion to the selenides 4, the ³¹P NMR signals shift to lower

ﬁelds, becoming sharp singlets associated with ⁷⁷Se satellites (I ¼ ½,

natural abundance 7.6%; Note: for further discussion of the ³¹P NMR

parameters, see below). Finally, the ³¹P NMR resonances of com-

plexes 5a-c are consistently shifted to even lower ﬁelds and split

into doublets due to interactions between the non-equivalent

phosphorus atoms, with ²J_PP¼ 22 Hz (in all compounds).

Scheme 1.

In addition to the conventional characterization, the solid-state

structures of adducts 3b and 3c [14] and, mainly, the complete

series of selenides 4a-c and Pd(II) complexes 5a-c were determined

by single-crystal X-ray diffraction analysis. The molecular struc-

tures of adducts 3b and 3c are shown in Fig. 1. In the case of 3b, the

ferrocene substituents are rotated to an intermediate conformation

between eclipsed anticlinal and staggered antiperiplanar [2a] with

lithiated intermediate. Fortunately, this side product could be

separated by chromatography.

In the subsequent reactions, the borane protecting groups [11]

in 3a-c were removed by treatment with 1,4-diazabicyclo[2.2.2]

octane (dabco) [12] in toluene (at elevated temperature). The

resulting free phosphines 1a-c were separated by ﬂash chroma-

tography and, after evaporation, converted into the respective

phosphine selenides 4a-c by reacting with KSeCN [13] in

dichloromethane-methanol. In the complexation reactions, the

eluate containing the free diphosphine was directly added to

the torsion angle C1-Cg1-Cg2-C6 (t), where Cg1 and Cg2 denote the

centroids of the cyclopentadienyl rings C(1e5) and C(6e10),

at ꢀ158.06(9)^ꢁ. The cyclopentadienyl rings are mutually tilted by

7.06(8)^ꢁ, which corresponds to individual Fe-C distances ranging

from 2.019(1) to 2.072(2) Å. The lengths of the pivotal C-P bonds

(C1-P11.793(1) Å and C6-P2 1.794(1) Å), as well as the P-B distances

(P1-B1 1.927(2) Å and P2-B2 1.920(2) Å) in 3b are similar to those

observed in dppf$2BH₃(1.790(3) Å and 1.922(4) Å, respectively)

[PdCl₂(cod)] (cod ¼ h²

:h

²-cycloocta-1,5-diene) dissolved in

dichloromethane, producing the corresponding P,P⁰-chelate com-

plexes 5a-c as the sole products (Scheme 2). Notably, these

simpliﬁed procedures avoiding the isolation of the air-sensitive

diphosphines 1 provided the target compounds at generally good

yields. For instance, the selenides 4 were isolated at 79% (4a), 53%

(4b) and 40% (4c) yields after column chromatography and crys-

tallization (Note: the relatively lower yield of 4c can be explained

by the higher solubility of this compound). Even the complexation

reactions were accomplished with very good isolated yields,

namely 74% for 5a, and 49% for the remaining members of the se-

ries, 5b and 5c.

Scheme 2. Synthesis of adducts 3 and their conversion into selenides 4 and Pd(II)

complexes

5

(R ¼ cyclohexyl (a), isopropyl (b), and tert-butyl (c); dabco ¼ 1,4-

Fig. 1. PLATON plots of the molecular structures of 3b (top) and 3c (bottom) showing

the displacement ellipsoids at 30% probability level.

diazabicyclo[2.2.2]octane, cod ¼ h²

:

h

²-cycloocta-1,5-diene).

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

[15]. In contrast, the ferrocene unit in 3c is tilted by only 3.8(1)^ꢁ(Fe-

C distances in the range 2.041(2)-2.064(2) Å) and adopts a similar,

Table 1

Selected distances and angle for 4a-c (in Å and deg).^a

albeit slightly more opened, conformation with

t

¼ 163.5(1)^ꢁ. The

Parameter

4a

4b

4c

P-C(Ph) distance (C1-P1) in 3c (1.792(2) Å) compares well with that

in 3b, whereas the P-C(t-Bu) distance (C6-P2; 1.812(2) Å) is

somewhat elongated. Similarly, the Ph₂P-B bond in 3c (P1-B1;

1.913(2) Å) is slightly but statistically signiﬁcantly shorter than the

(t-Bu)₂P-B bond (P2-B2; 1.932(3) Å).

Fe-C^b

4

2.029(2)-2.058(2)

2.3(1)

2.024(2)-2.063(2)

1.3(1)

2.032(2)-2.058(2)

2.79(9)

147.9(1)

1.793(2)

2.1124(5)

1.814(2)

t

141.9(2)

1.789(2)

ꢀ145.0(1)

C1-P1

P1-Se1

C6-P2

P2-Se2

1.793(2)

2.1084(7)

1.805(2)

2.1157(5)

1.796(2)

The solid-state structures of the phosphine selenides 4a-c are

presented in Fig. 2. Their geometric parameters outlined in Table 1

indicate that the 1,1⁰-disubstituted ferrocene units in the molecules

of 4a-c have similar conformations near-eclipsed anticlinal

2.1220(8)

2.1090(6)

2.1179(4)

a

Deﬁnition of the parameters:

t is the torsion angle C1-Cg1-Cg2-C6 (t), where

Cg1 and Cg2 stand for the centroids of the cyclopentadienyl rings C(1e5) and

C(6e10), respectively, and 4 is the dihedral angle of the cyclopentadienyl least-

square planes (tilt angle).

(optimal value:

t

¼ 144^ꢁ) and are negligibly tilted (<3^ꢁ). The vari-

b

The range of the individual Fe-C bond distances.

ation of P¼Se bond lengths in the entire series is small (ca. 0.014 Å),

and the individual parameters do not differ much from those re-

ported for analogous dppf-type compounds fc[P(Se)R₂]₂(R/P¼Se

[Å]: Ph/2.103(6) [16], Cy/2.113 and 2.126 [17], i-Pr/2.118 and 2.123

[18], and t-Bu/2.1194(5) and 2.1200(5) [19]), and for R₂P(Se)

fcCONHMe (R ¼ Cy, i-Pr, t-Bu and Ph) [6]. Similarly, only small

variations in the pivotal C-P bonds were observed, even when using

diverse phosphine substituents (e.g., the C6-P2 bond lengths vary

by only 0.013 Å).

practically marginal (<0.01 Å for an individual compound). In all

structures, the P1-Pd-P2 angle associated with the chelating ligand

is the most opened of the interligand angles, which is compensated

by closing adjacent angles, particularly P1-Pd-Cl2. Notably, the

value of the bite angle P1-Pd-P2 lies between those reported for the

analogous complexes featuring the parent dppf (z98e99^ꢁfor

CHCl₃and CH₂Cl₂solvates [20,10d]) and those of the respective

congener fc(PR₂)₂(R ¼ Cy: 102.5^ꢁ[21], R ¼ i-Pr: 103.4^ꢁ[22], and

R ¼ t-Bu: 104.2^ꢁ[23]). The dihedral angle subtended by the

{Pd,Cl1,Cl2} and {Pd,P1,P2} “half-planes”, which can serve as a

measure of coordination sphere distortion, increase from 1.02(3)^ꢁ

in 5c$CH₂Cl₂, and 2.07(2)^ꢁin 5a to 5.45(3)^ꢁin 5b. Again, this in-

crease is apparently unrelated to the steric demands of the phos-

phine substituents.

As mentioned above, the whole series of the Pd(II) complexes

5a-c was structurally characterized (compound 5c in the solvated

form 5c$CH₂Cl₂). The structures are shown in Fig. 3, and the

pertinent structural data are given in Table 2. The compounds are

P,P⁰-chelate complexes similar to those formed by dppf and its

symmetrical analogues with other substituents at the phosphorus

atoms (i.e., fc(PR₂)₂). The chelate coordination reduces the twisting

of the ferrocene scaffold (cf. the

t

angles: 15e26^ꢁ), albeit without

substantial tilting of the ferrocene cyclopentadienyls (the largest

tilt angle is 5.4(1)^ꢁin 5b).

2.2. Synthesis of type-2 donors, their phosphine selenides and Pd(II)

Remarkably, the variation of the Pd-donor distances and even

the interligand angles in the structures of 5a-c are relatively small

and with no clear-cut trends (N.B. some similarities can be

observed between 5a and 5b, particularly in Pd-PR₂bond lengths

and in the P-Pd-Cl and Cl1-Pd-Cl2 angles). For instance, the Pd-P1

distances in the molecule of 5a are slightly shorter than those in

the two remaining compounds, whereas the Pd-P2 distance in

5c$CH₂Cl₂in a similar degree exceeds those in 5a and 5b (by ca.

0.03e0.04 Å). The variation in the non-equivalent Pd-Cl bonds is

complexes

In an initial attempt, the asymmetric, semi-homologous

diphosphines 2 were synthesized by introducing the different

phosphine moiety ﬁrst (in BH₃-protected form). The synthesis was

performed in parallel for the derivatives with the PCy₂and P(i-Pr)₂

substituents, as shown in Scheme 3 (route A). Thus, stepwise lith-

iation and functionalization of 1,1⁰-dibromoferrocene [8,9] was

used to prepare the known P-protected bromides 6a and 6b [6],

Fig. 2. PLATON plots of the molecular structures of 4a-c showing the displacement ellipsoids at 30% probability level.

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

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Fig. 3. PLATON plots of the complex molecules in the structures of 5a, 5b and 5c$CH₂Cl₂. The displacement ellipsoids are shown at 30% probability level.

R₂PfcCH₂OH$BH₃(9a-b; fc ¼ ferrocene-1,1⁰-diyl) at isolated yields

exceeding 90% (95 and 92% after chromatographic puriﬁcation).

The reduction is accompanied by a change in color from an initial

deep red to an orange yellow associated with the replacement of

the conjugated ferrocene substituent (CHO) by a non-conjugated

one (CH₂OH) and can be thus easily followed visually. After the

reduction, the NMR resonances of aldehyde substituent are

replaced by those of the hydroxymethyl group, namely a doublet at

d_H4.4 (³J_HHz 5.5 Hz) and a singlet at d_C60.4 (Note: similar pa-

rameters were reported for Ph₂PfcCH₂OH$BH₃[5f]).

In the following step, the alcohols 9a and 9b were reacted with

diphenylphosphine in the presence of Me₃SiCl and NaI (in excess)

in dry acetonitrile [4,24] to provide the respective diphosphines,

which were isolated as the corresponding adducts 10a and 10b

following BH₃$SMe₂addition and column chromatography. The

yields of the BH₃-protected diphosphines were approximately 30%.

The reaction also produced the deoxygenated products

R₂PfcMe$BH₃(11a-b) (typically at 20% isolated yields) which,

however, corresponds to the ability of the Me₃SiCl-NaI-MeCN re-

agent to promote the reductive removal of reactive OH groups [25].

Compounds 10a-b are characterized by a pair of broad, doublet-like

resonances in the ³¹P{¹H} NMR spectra and signals due to the

methylene group in the newly installed CH₂PPh₂pendant (d_H3.5,

doublet with ²J_PH¼ 10.4 Hz; d_C28.5, doublet with ¹J_PC¼ 34 Hz). The

methyl group in the byproducts 11a and 11b also has a character-

istic signature, consisting of singlets at d_H1.99 and d_C14.6,

approximately.

Table 2

Selected distances and angle for 5a, 5b and 5c$CH₂Cl₂(in Å and deg).^a

Parameter

5a

5b

5c$CH₂Cl₂

Pd-P1

Pd-P2

2.2643(4)

2.2841(4)

2.3458(4)

2.3560(4)

101.28(1)

88.08(1)

2.2900(4)

2.2816(5)

2.3427(5)

2.3378(5)

102.49(2)

87.65(2)

2.2844(5)

2.3222(6)

2.3537(5)

2.3550(6)

101.97(2)

85.70(2)

Pd-Cl1

Pd-Cl2

P1-Pd-P2

Cl1-Pd-Cl2

P1-Pd-Cl2

P2-Pd-Cl1

Fe-C

82.83(2)

83.09(2)

80.12(2)

87.81(1)

87.00(2)

92.22(2)

2.017(2)-2.056(2)

1.94(9)

2.003(2)-2.060(2)

5.4(1)

2.008(2)-2.059(2)

3.2(1)

4

t

ꢀ15.2(1)

ꢀ26.4(1)

ꢀ23.5(2)

a

The parameters are deﬁned as for compounds 4a-c, see footnotes to Table 1.

which were then converted into the respective protected aldehydes

7a and 7b by similar lithium/halogen exchange and formylation

with N,N-dimethylformamide (DMF). The aldehydes were obtained

at good yields (72 and 77% after chromatography) together with

minor amounts of the respective adducts FcPR₂$BH₃(8a-b; 14% in

both cases) resulting from decomposition of the lithiated in-

termediates. The introduction of the formyl substituent was clearly

identiﬁed in the NMR spectra through distinct CHO resonances at

d_H10.0 and d_C194.

A subsequent reduction of aldehydes 7 with borane (namely

with BH₃$SMe₂) [5f] afforded the corresponding alcohols

Scheme 3. Alternative synthetic routes to the semi-homologous diphosphines 2a-c (R ¼ cyclohexyl (a), isopropyl (b), and tert-butyl (c); DMF ¼ N,N-dimethylformamide).

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

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The deprotection of adducts 10a-b was effected by heating to

cyclopentadienyls are tilted by 4.4(1)^ꢁand their substituents as-

70 ^ꢁC in neat morpholine [26] overnight (dabco proved less efﬁ-

cient in this reaction). In the case of 10b, the reaction produced the

target diphosphine 2b at a good yield (76%, after column chroma-

tography). By contrast, a similar reaction with 10a was less efﬁcient

(the yield of 2a was 57%), and the isolated product was typically

contaminated with minor amounts (5e10%) of the partly depro-

tected compound Ph₂PCH₂fcPCy₂$BH₃.

sume a synclinal eclipsed conformation with

t

¼ 76.5(1)^ꢁ. The

formyl substituent (C11 ¼ O ¼ 1.207(2) Å) is slightly rotated from

the plane of its bonding cyclopentadienyl ring C(1e5), and the

torsion angle C2-C1-C11-O is 11.5(3)^ꢁ.

Compound 9b crystallizes (Fig. 5) with two structurally inde-

pendent molecules primarily differing in the mutual orientation of

the substituents at the ferrocene unit (space group P2₁/c). In both

molecules, the cyclopentadienyls adopt a similar, approximately

Rather than optimizing the last two reaction steps, which sub-

stantially reduced the overall yield of the target diphosphines 2

(the yields of 2a and 2b over the ﬁve steps were 9 and 14%,

respectively), we sought an alternative, more efﬁcient procedure.

Speciﬁcally, we decided to introduce the most oxidation-sensitive

dialkylphosphino moiety at a late stage of the synthesis towards

eliminating the additional protection/deprotection steps. In the

modiﬁed synthesis, represented by route B in Scheme 3, we used

the recently reported phosphinoferrocene bromide 13, which is

accessible in three steps from 1,1⁰-dibromoferrocene (via alcohol

12) [5h]. Gratifyingly, the lithiation of 13 with butyllithium in

anhydrous tetrahydrofurane (THF), followed by addition of the

respective chlorophosphine ClPR₂, produced the unprotected

diphosphines 2a-c at 52, 71 and 72% yields, respectively (N.B. the

overall yields of 2a and 2b were 28% and 39% from the same

starting material, which were considerably higher than those of

route A). In addition, minor amounts of the monophosphine

FcCH₂PPh₂were isolated analogously to other reactions involving

lithioferrocene intermediates.

synclinal eclipsed conformation (

t

¼ 73.2(2)^ꢁand ꢀ74.1(2)^ꢁfor

molecules 1 and 2). Considering the conformation of the ferrocene

unit, the molecules are formally pseudoenantiomers because the

rotation of the cyclopentadienyls is prevented in the solid state, and

the CH₂OH groups are positioned in roughly mirror-image posi-

tions with respect to the phosphine substituent (see the overlap in

Fig. 5). In addition, the CH₂OH moiety is directed away from the

ferrocene moiety in molecule 1 (C102-C101-C111-O1 ¼82.4(3)^ꢁ),

The presence of the (diphenylphosphino)methyl groups in 2a-c

is indicated by the signals of the methylene linker (¹H NMR:

1

d_Hz 3.16, ¹³C NMR: d_C30.0, doublet with J_PC¼ 15 Hz) and by the

³¹P NMR resonances at d_Pz ꢀ11.5. The ³¹P NMR signals of the other

phosphine substituents directly bound to the ferrocene unit are

observed at d_Pꢀ7.1, 0.9 and 28.3 for 2a, 2b and 2c, respectively.

The formulation of compounds 7a and 9b was corroborated by

single-crystal X-ray diffraction analysis. The molecular structure of

7a (Fig. 4) is unexceptional considering the data reported for the

analogous

compound

Ph₂PfcCHO

[27].

The

ferrocene

Fig. 5. (top) PLATON plot of molecule 1 in the structure of 9b with displacement el-

lipsoids at 30% probability level. Note: the labelling scheme in molecule 2 is strictly

analogous, and the ﬁrst digit is replaced by 2. (bottom) Overlap of the two independent

molecules. The hydrogen atoms are omitted for clarity.

Fig. 4. PLATON plots of the molecular structure of 7a. The displacement ellipsoids

enclose the 30% probability level.

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

19

whereas this moiety is rotated toward the iron atom in molecule 2

(C202-C201-C211-O2 ¼ ꢀ158.3(2)^ꢁ). In the solid state, the inde-

pendent molecules interact via O-H/O hydrogen bonds to form

dimers, which further assemble into inﬁnite helical chains along

⁷⁷Se satellites. In the case of the CH₂PPh₂substituents, this is also

manifested as a shift of the methylene resonances to a lower ﬁeld

(

d_Hz 4.14; Dd_Hz þ1.0 ppm) and their splitting into doublets

(²J_PHz 12 Hz; Note: the methylene signals in the free phosphines

are observed as singlets). Similar changes are noted also in the ¹³

the

crystallographic

2₁

screw

axis

(O1-H1O/O2:

C

O1/O2 ¼ 2.696(2) Å, angle at H1O ¼ 163^ꢁ; O2-H2O/O1ⁱ:

O2/O1ⁱ¼ 2.649(3) Å, angle at H2O ¼ 170^ꢁ, i ¼ x, 1/2ꢀy, 1/2 þ z).

Similar interactions resulting in the multiplication of the structur-

ally independent molecules were also noted in the crystal struc-

tures of FcCH₂OH [28], Ph₂PfcCH₂OH [27], and Ph₂PfcCH₂OH$BH₃

[5f].

NMR spectra, wherein the methylene resonances appear shifted to

1

a lower ﬁeld (Dd_Cz þ6 ppm), and the J_PCcoupling constants in-

crease (from 15 to 44 Hz).

The comparison of the ³¹P NMR parameters of 4a-c and 14a-c

outlined in Table 3 shows that, although the chemical shifts (d_P) and

1

the J_SePcoupling constants of the invariant P(Se)Ph₂moieties in

Similarly to their dppf-like counterparts, the free phosphines

2a-c were converted into the respective selenides 14a-c by reaction

with potassium selenocyanate in dichloromethane-methanol

(Scheme 4; Note: the polar solvent is required to dissolve the

inorganic reagent) and were isolated at 84, 82 and 58% yields,

respectively, by column chromatography and subsequent crystal-

lization. The selenation of the phosphine moieties results in a shift

of the ³¹P NMR signals to lower ﬁelds and in the emergence of the

both separated series remain largely unchanged, those of the other

phosphinoselenoyl substituents P(Se)R₂expectedly vary. In the

dppf-type compounds, the chemical shifts increase in the series

1

4a < 4b < 4c, whereas the J_SePcoupling constants rise in the

following sequence of the phosphine substituents, Cy z t-Bu < i-

Pr ≪ Ph, suggesting a decrease in donor ability of the phosphorus

atoms in the same order. Overall, the observed coupling constants

are quite similar to those determined for the symmetric com-

pounds fc[P(Se)R₂]₂(R/¹J_SeP[Hz]: Ph/737 [16], Cy/710 [17], i-Pr/716

[18], and t-Bu/700 [19]).

1

The J_SePcoupling constants determined for the P(Se)Ph₂sub-

stituents in 14a-c are 7e8 Hz lower than the respective values in

4a-c, and a similar trend is observed even for the varied P(Se)R₂

substituents, which in turn allows us to classify the homologous

diphosphines 14 as better donors than their dppf-type analogues 4.

1

However, it should be noted that the J_SePcoupling constants are

Scheme 4. Synthesis of phosphine selenides 14a-c (R ¼ cyclohexyl (a), isopropyl (b),

and tert-butyl (c)).

not a simple measure of either electronic or steric properties.

Indeed, the J_SePcoupling constants (in absolute values) were

1

shown to increase with the increasing electron-withdrawing

character of the phosphine substituents (due to the higher s-

character of the phosphorus lone pair) [7] and also correlate with

the basicity (pK_b) of the phosphine ligands [29]. However, they are

also affected by steric factors. In particular, closing the C-P-C angles

in phosphines with bulky substituents reduces the s-character of

Table 3

³¹P NMR shifts (in ppm) and ¹J_SePcoupling constants (in Hz; values in parentheses)

of phosphine selenides 4a-c and 14a-c.^a

Compound

R

d_P(¹J_SeP

)

P(Se)Ph₂

P(Se)R₂

1

4a

4b

4c

14a

14b

14c

Cy

31.7 (736)

31.8 (737)

31.8 (736)

34.0 (729)

33.8 (728)

50.0 (704)

58.2 (710)

74.6 (705)

50.4 (696)

58.8 (702)

75.3 (699)

the phosphorus lone pair and, consequently, decreases the J_SeP

coupling constants [30].

i-Pr

t-Bu

Cy

i-Pr

t-Bu

In addition to spectroscopic characterization, the solid-state

structures of the phosphine selenides 14a-c were determined by

single-crystal X-ray diffraction analysis. The structures are pre-

sented in Fig. 6, and the selected geometric parameters are outlined

in Table 4. The substituents at the central ferrocene units in the

a

The spectra were recorded in CDCl₃. Chemical shifts are given relative to 85%

H₃PO₄.

Fig. 6. PLATON plots of the molecular structures of 14a-c with the displacement ellipsoids scaled to the 30% probability level.

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

20

Table 4

Selected distances and angle for 14a-c (in Å and deg).^a

Parameter

14a

14b

14c

Fe-C

4

2.036(3)-2.067(3)

5.9(2)

2.038(3)-2.056(3)

1.9(2)

2.030(3)-2.062(3)

4.2(2)

t

84.2(2)

1.834(3)

2.1105(7)

1.792(3)

2.1249(7)

112.0(2)

ꢀ74.0(2)

ꢀ76.7(2)

C11-P1

P1-Se1

C6-P2

P2-Se2

C1-C11-P1

1.829(3)

1.834(3)

2.1086(8)

1.790(3)

2.1117(9)

114.4(2)

2.111(1)

1.800(3)

2.1284(9)

113.7(2)

a

The parameters are deﬁned as for 4a-c. See footnotes to Table 1.

Fig. 7. ³¹P{¹H} NMR spectra of the mixture obtained upon reacting stoichiometric

amounts of 2a and [PdCl₂(MeCN)₂] in CDCl₃(bottom) and after heating this mixture to

50 ^ꢁC overnight (top). The signals due to 15a ( ) and 16a (ꢂ) are indicated in the

A

spectra.

featuring the bulky di-tert-butylphosphino substituent proved less

selective and, after equilibration (50 ^ꢁC/overnight), led to a mixture

of 15c and 16c with a modest preference for the dinuclear complex

(15c:16c z 40:60).

Scheme 5. Synthesis of Pd(II) complexes from diphosphines 2a-c (R ¼ cyclohexyl (a),

isopropyl (b), and tert-butyl (c); cod ¼ cyclocta-1,5-diene).

Compounds 15 and 16 could be clearly distinguished based on

their NMR parameters. Thus, complexes 15a-c give rise to a pair of

singlets in the ³¹P NMR spectra, and the signals of the PPh₂donor

occur at d_Pz 29. This is consistent with the NMR data of the cis-

molecules of 14a-c are rotated to closer positions than those in 4a-

c, assuming near-synclinal eclipsed conformations in all cases

(ideal value:

t

¼ 72^ꢁ). This can be associated with decreased steric

chelate complexes [PdCl₂(dppf-k²P,P⁰)]

(d_P34.0 [32]) and

crowding due to the presence of the methylene spacer, which al-

lows placing the P(Se)Ph₂groups away from the ferrocene moiety.

The orientation of the terminal P(Se)Ph₂moieties in the three

compounds is rather similar, as shown by the torsion angles Se1-

P1-C11-C1 of 66.3(2)^ꢁ, 54.3(2)^ꢁand 57.0(3)^ꢁfor 14a-c, and even

the terminal P(Se)R₂substituents are similarly positioned, with the

P2¼Se2 bond roughly parallel to the bonding cyclopentadienyl

ring. Other parameters, including the P¼Se distances, are similar to

those determined for 4a-c.

[PdCl₂(Ph₂PfcCH₂PPh₂-k²P,P⁰)] (d_P18.2 and 24.6, both singlets [4]).

2

Conversely, a pair of doublets with J_PPcoupling constants in the

range 528e541 Hz [33] are observed in the spectra of 16a-c, and the

signals of the PPh₂moieties are found at d_Pz 16.5, which corre-

sponds to the position of the ³¹P NMR signals of the bis-phosphine

complexes trans-[PdCl₂(Ph₂PfcY-

(CH₂)_nOMe [35,5f], (CH₂)_nSMe [36,5i], (CH₂)_nC₅H₄N [5a], CO₂H [37],

PO₃Et₂[38], etc.; n ¼ 0 and 1 in all cases).

k

P)₂] (Y

¼

CH¼CH₂[34],

Our attempts to isolate pure compounds by crystallization of the

reaction mixtures failed. Nevertheless, the crystallization, which is

apparently governed by the relative solubility of the components

(15 vs. 16), provided small amounts of crystalline 15a$CH₂Cl₂, 16b

and 16c, which were structurally characterized. The molecular

structure of 15a$CH₂Cl₂is shown in Fig. 8, and the relevant struc-

tural parameters are outlined in Table 5. Comparison with the pa-

rameters determined for 5a (see Table 2) reveals that the more

ﬂexible ligand 2a coordinates with a slightly larger bite angle (P1-

Pd-P2, by ca. 1.7^ꢁ). This ﬁnding contrasts with the changes observed

when replacing dppf by Ph₂PfcCH₂PPh₂in a similar complex,

decreasing the bite angle by 2e3^ꢁ. Nonetheless, this can be

attributed to steric effects, namely to the presence of the bulky

cyclohexyl groups that occupy a larger volume than ﬂat phenyl

rings. The same effects may explain the signiﬁcant distortion of the

coordination sphere around palladium, where the two half planes,

{Pd, P1, P2} and {Pd, Cl1, Cl2}, are twisted by as much as 13.00(3)^ꢁ.

However, the individual geometric parameters match well those

In contrast to complexation reactions with dppf-type ligands

1a-c, which afforded the complexes 5a-c as the sole products (see

above), the addition of phosphines 2a-c to PdCl₂equivalents (viz.,

[PdCl₂(MeCN)₂] or [PdCl₂(cod)]) produced mixtures of several

Pd(II) complexes, whose relative amounts partly depended on how

the reaction was performed (e.g., whether a ligand solution was

added to a solid Pd precursor or to its solution) and changed over

time [31]. In the case of diphosphines 2a and 2b (Scheme 5), the

reaction mixtures were markedly dominated by the cis-chelate

complexes 15a-b (85e90%) analogous to 5 and also contained mi-

nor amounts of the symmetrical dinuclear complexes 16a-b

(10e15%) as well as some other unidentiﬁed compounds (most

likely the plausible asymmetric dimer also). Upon prolonged

standing at room temperature or after heating to 50 ^ꢁC for several

hours, the unknown minor species nearly disappeared, and the

compounds 15a-b and 16a-b became the dominant products

(>95%), whilst their ratio remained practically unchanged (around

85:15; see Fig. 7). Notably, a similar reaction with ligand 2c

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

21

Table 6

Selected distances and angles for 15b and 15c (in Å and deg).^a

Parameter

15b

15c

Pd-P1

2.3203(8)

2.3615(8)

2.2946(9)

2.2989(8)

84.41(3)

91.13(3)

93.51(3)

91.28(3)

2.042(3)-2.061(3)

4.1(2)

2.3255(8)

2.4214(8)

2.3349(8)

2.2788(8)

83.68(3)

89.82(3)

97.66(3)

89.82(3)

Pd-P2⁰

Pd-Cl1

Pd-Cl2

P1-Pd-Cl1

P1-Pd-Cl2

P2⁰-Pd-Cl1

P2⁰-Pd-Cl2

Fe-C

2.038(3)-2.083(3)

8.0(2)

4

t

81.3(2)

149.5(2)

C11-P1

C1-C11-P1

1.853(3)

114.8(2)

1.844(3)

116.3(2)

a

The parameters are deﬁned as for compounds 4a-c, see footnotes to Table 1. The

prime-labeled atoms are generated by crystallographic inversion.

underlines the symmetric (head-to-tail) character of these dimeric

compounds. Notably, the coordination spheres around the palla-

dium atoms in 16b and 16c are considerably less angularly distorted

than those in 5a-c and 15a, presumably because the bulky phos-

phine moieties are more distant, occupying trans positions. In both

structures, the Pd-Cl1 arms are diverted from the bulky PR₂groups

so that the P1-Pd-Cl1 angles are the most acute and the P2⁰-Pd-Cl1

angles the most opened of the interligand angles, and this depar-

ture from the ideal 90^ꢁis more pronounced in 16c featuring the

bulkier P(t-Bu)₂moiety. The changed disposition of the donor

atoms also affects the Pd-P and the Pd-Cl distances due to different

trans inﬂuence [39] of the donor atoms (P > Cl): the Pd-Cl distances

are shorter than those in the cis-chelate complexes, whereas the

Pd-P bonds are longer. For steric reasons, the Pd-P2⁰distance in 16c

is 0.06 Å longer than that in 16b (Note: the difference between the

Pd-P2 distances in 5b and 5c is much smaller, 0.04 Å). In addition,

the molecules of 16b and 16b differ by mutual orientation of their

substituted ferrocene moieties. The less opened conformation of

Fig. 8. PLATON plot of the complex molecule in the structure of 15a$CH₂Cl₂. The

displacement ellipsoids enclose the 30% probability level.

Table 5

Selected distances and angles for 15a$CH₂Cl₂(in Å and deg).^a

Pd-P1

Pd-P2

Pd-Cl1

Pd-Cl2

Fe-C

2.2901(5)

2.2883(5)

2.3435(5)

2.3606(5)

2.030(2)-2.047(2)

4.7156(5)

1.853(2)

P1-Pd-P2

Cl1-Pd-Cl2

P1-Pd-Cl2

P2-Pd-Cl1

4

102.99(2)

87.11(2)

82.95(2)

88.54(2)

3.80(9)

Fe/Pd

C11-P1

t

ꢀ16.7(1)

C1-C11-P1

122.6 (1)

a

The parameters are deﬁned as for compounds 4a-c, see footnotes to Table 1.

determined for 5a. Even the ferrocene cyclopentadienyls in the

structure of 15a$CH₂Cl₂are rotated similarly to those in 5a,

assuming an intermediate conformation between eclipsed syn-

periplanar (

t

¼ 0^ꢁ) and staggered synclinal (

t

¼ 36^ꢁ), and are tilted

the ferrocene scaffold in 16b (t t

z 80^ꢁ) than in 16c ( z 150^ꢁ) re-

by approximately 4^ꢁ. Because of the chelate coordination, the

CH₂PPh₂group is inclined toward the ferrocene unit at an angle

between the C11-P1 bond and the C(1e5) plane of 34.18(8)^ꢁ.

Complexes 16b and 16c (Fig. 9 and Table 6) crystallize distrib-

uted around the crystallographic inversion centers. Therefore, only

half of their molecules are structurally independent, which

sults in a more compact structure with a shorter Pd/Pd' distance

(6.8777(5) Å vs. 8.3827(6) Å). Furthermore, the bridging confor-

mation also allows the reorientation of the CH₂PPh₂arm to a ste-

rically more relaxed position, away from the ferrocene unit (cf. the

angles between the C11-P1 bonds and the C(1e5) planes of 65.3(2)^ꢁ

and 57.0(2)^ꢁfor 16b and 16c, respectively).

Fig. 9. PLATON plot of the molecular structure of dimeric complexes 16b and 16c showing 30% displacement ellipsoids.

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

22

3. Conclusion

(25 mL), and the solution was cooled to ꢀ78 ^ꢁC in a dry ice/ethanol

bath while stirring. n-Butyllithium (2.2 mL 2.5 M in hexanes,

5.5 mmol) was added continuously stirring at ꢀ78 ^ꢁC for 15 min to

afford an orange suspension. Subsequently, neat chlor-

odicyclohexylphosphine (1.4 mL, 6.0 mmol) was introduced, and

the reaction mixture was stirred with cooling for 30 min, and then

at room temperature for 90 min. The resulting red solution was

treated with an excess of borane-dimethyl sulﬁde (7.5 mL of 2 M

solution in diethyl ether, 15 mmol) and stirred for another 30 min

before quenching by adding saturated aqueous NaHCO₃(a vigorous

effervescence was observed due to decomposition of an excess

BH₃,SMe₂). Then, the mixture was diluted with chloroform (ca.

15 mL) and brine (ca. 10 mL). The organic phase was separated,

washed with brine, dried over anhydrous magnesium sulfate and

Several asymmetric, dppf-type diphosphines with diverse

phosphine substituents were prepared by bromine/lithium ex-

change and phosphinylation from 1⁰-(diphenylphosphino)-1-

bromoferrocene and isolated in the form of air-stable borane ad-

ducts. These compounds were smoothly deprotected with dabco,

and the resulting free diphosphines (requiring no tedious isolation)

were converted into the respective phosphine selenides and P,P⁰-

chelate palladium(II) complexes. The corresponding homologous

ligands containing a methylene spacer between the PPh₂moiety

were prepared via BH₃-protected intermediates (with the varied

PR₂group introduced ﬁrst) and also directly in the free phosphine

form with the PR₂introduced in the last step. The latter synthesis

proved to be more practical, allowing an easier variation of the

varied phosphine substituents and affording substantially higher

yields. The coordination tests with R₂PfcCH₂PPh₂revealed the

concurrent formation of monopalladium chelate complexes

evaporated with chromatographic silica gel (40e63 mm, ca.

10e15 mL). The pre-adsorbed product was transferred onto a silica

gel column packed in hexane-toluene (1:3). Elution with the same

solvent provided

a minor yellow band containing mostly

1

(dominant) and ligand-bridged dimers. Thus, although the J_SeP

FcPPh₂$BH₃, and then a major orange red band due to 3a, which

was isolated as an orange microcrystalline solid after evaporation.

Yield: 2.44 g (82%). The product could be crystallized from hot

heptane.

coupling constants suggest that the homologous diphosphines are

better (stronger) donors than their non-spaced, dppf-type coun-

terparts, the former coordinate less selectively, presumably because

they form larger and less rigid chelate rings.

¹H NMR (399.95 MHz, CDCl₃):

d 0.20e1.50 (br m, 6 H, BH₃),

1.05e1.35 (m, 10 H, Cy), 1.60e1.90 (m, 12 H, Cy), 4.19 (vq, J⁰¼ 1.8 Hz,

2 H, fc), 4.42 (d of vt, J ¼ 0.9, 1.8 Hz, 2 H, fc), 4.45 (vq, J⁰¼ 1.9 Hz, 2 H,

fc), 4.77 (d of vt, J ¼ 1.2, 1.8 Hz, 2 H, fc), 7.39e7.51 (m, 6 H, Ph),

4. Experimental

7.54e7.60 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d 25.87

4.1. General considerations

(d, J_PC¼ 1 Hz, 2 C, CH₂of Cy), 26.79 (s, 2 C, CH₂of Cy), 26.89 (s, 4 C,

CH₂of Cy), 27.17 (d, J_PC¼ 2 Hz, 2 C, CH₂of Cy), 32.44 (d, ¹J_PC¼ 34 Hz,

All reactions were performed in an argon atmosphere using

1

standard

Schlenk

techniques.

1⁰-(Diphenylphosphino)-1-

2 C, CH of Cy), 70.12 (d, J_PC¼ 67 Hz, 1 C, C_ipsoeP of fc), 70.26 (d,

¹J_PC¼ 55 Hz, 1 C, C_ipsoeP of fc), 72.95 (d, J_PC¼ 7 Hz, 2 C, CH of fc),

73.15 (d, J_PC¼ 6 Hz, 2 C, CH of fc), 73.93 (d, J_PC¼ 10 Hz, 2 C, CH of fc),

74.82 (d, J_PC¼ 7 Hz, 2 C, CH of fc), 128.50 (d, J_PC¼ 10 Hz, 4 C, CH of

Ph), 130.85 (d, ¹J_PC¼ 59 Hz, 2 C, C_ipsoeP of Ph), 131.05 (d, ⁴J_PC¼ 2 Hz,

2 C, CH of Ph), 132.58 (d, J_PC¼ 10 Hz, 4 C, CH of Ph). ³¹P{¹H} NMR

bromoferrocene [9], 6a-b [6], 12 and 13 [5h] were prepared ac-

cording to literature methods. Other chemicals were purchased

from commercial suppliers (Alfa-Aesar, Sigma-Aldrich; solvents

from Lach-Ner, Czech Republic) and were used without additional

puriﬁcation. Tetrahydrofuran (THF), methanol and dichloro-

methane were dried using a PureSolv MD5 solvent puriﬁcation

system (Innovative Technology, Amesbury, USA). Acetonitrile was

dried over CaH₂and distilled under an argon atmosphere. Toluene

and triethylamine were dried over sodium metal and distilled

similarly. Morpholine was distilled under argon.

(161.90 MHz, CDCl₃):

d

16.3 (br d, PPh₂), 24.4 (br d, PCy₂). ESI þ MS:

m/z 617 ([MþNa]^þ). Anal. Calc. for C₃₄H₄₆B₂FeP₂(594.14): C 68.73, H

7.80%. Found: C 68.47, H 7.63%.

NMR spectra were recorded at 25 ^ꢁC using a Varian UNITY Inova

400 spectrometer operating at 399.95, 100.58, and 161.90 MHz for

4.3. Synthesis of 1⁰-(diisopropylphosphino)-1-(diphenylphosphino)

ferroceneꢀborane (1/2), adduct 3b

¹H, ¹³C, and ³¹P, respectively. Chemical shifts (

d in ppm) are

expressed relative to the internal SiMe₄standard (¹H and ¹³C) or to

the external 85% aqueous H₃PO₄(³¹P), all set to 0 ppm. In addition

to the usual notation of signal multiplicity [40], vt and vq are used

to denote virtual triplets and quartets in the ¹H NMR spectra arising

from the AA'BB⁰and AA'BB⁰X (A, B ¼ ¹H; X ¼ ³¹P) spin systems

constituted by the protons at the ferrocene cyclopentadienyls. IR

spectra were measured using an FTIR Nicolet 760 instrument in the

range 400e4000 cm^ꢀ1. Conventional low-resolution electrospray

ionization mass spectra (ESI MS) were obtained on a Bruker Esquire

3000 spectrometer using samples dissolved in HPLC-grade meth-

anol. High-resolution (HR) ESI MS measurements were performed

using a Q-tof Micro (Waters) spectrometer. Elemental analyses

were performed in a PE 2400 Series II CHNS/O elemental analyzer

(Perkin Elmer).

The same procedure exploiting chlorodiisopropylphosphine

(1.0 mL, 6.0 mmol) provided adduct 3b as an orange-red crystalline

solid. Yield: 2.21 g (86%). Compound 3b can be recrystallized from

hot heptane.

¹H NMR (399.95 MHz, CDCl₃):

d 0.10e0.95 (br m, 6 H, BH₃), 1.06

(dd, ³J_HH¼ 7.1 Hz, ³J_PH¼ 14.2 Hz, 6 H, CHMe₂), 1.11 (dd, ³J_HH¼ 7.1 Hz,

2

³J_PH¼ 14.9 Hz, 6 H, CHMe₂), 2.04 (d of sept, J_PH¼ 10.1 Hz,

³J_HH¼ 7.1 Hz, 2 H, CHMe₂), 4.22 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.44 (d of vt,

J ¼ 0.9, 1.8 Hz, 2 H, fc), 4.48 (vq, J⁰¼ 1.9 Hz, 2 H, fc), 4.79 (d of vt,

J ¼ 1.2, 1.9 Hz, 2 H, fc), 7.39e7.61 (m, 10 H, Ph). ¹³C{¹H} NMR

2

(100.58 MHz, CDCl₃):

d

17.22 (s, 2 C, CHMe₂), 17.47 (d, J_PC¼ 2 Hz,

1

2 C, CHMe₂), 22.62 (d, J_PC¼ 35 Hz, 2 C, CHMe₂), 69.75 (d,

¹J_PC¼ 55 Hz, 1 C, C_ipsoeP of fc), 70.19 (d, ¹J_PC¼ 67 Hz, 1 C, C_ipsoeP of

fc), 72.83 (d, J_PC¼ 7 Hz, 2 C, CH of fc), 73.18 (d, J_PC¼ 6 Hz, 2 C, CH of

fc), 73.94 (d, J_PC¼ 10 Hz, 2 C, CH of fc), 74.80 (d, J_PC¼ 7 Hz, 2 C, CH of

4.2. Synthesis of 1⁰-(dicyclohexylphosphino)-1-

(diphenylphosphino)ferroceneꢀborane (1/2), adduct 3a

fc), 128.52 (d, J_PC¼ 10 Hz, 4 C, CH of Ph), 130.84 (d, ¹J_PC¼ 59 Hz, 2 C,

4

C

_ipsoeP of Ph), 131.06 (d, J_PC¼ 3 Hz, 2 C, CH of Ph), 132.59 (d,

J_PC¼ 10 Hz, 4 C, CH of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d 16.2

A two-neck, oven-dried reaction ﬂask was charged with 1⁰-

(diphenylphosphino)-1-bromoferrocene (2.24 g, 5.0 mmol) and a

stirring bar. The solid educt was dissolved by adding anhydrous THF

(br d, PPh₂), 31.8 (br d, PiPr₂). ESI þ MS: m/z 537 ([MþNa]^þ), 553

([MþK]^þ). Anal. Calc. for C₂₈H₃₈B₂FeP₂(513.99): C 65.42, H 7.45%.

Found: C 65.11, H 7.58%.

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P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

23

4.4. Synthesis of 1⁰-(di-tert-butylphosphino)-1-

(diphenylphosphino)ferroceneꢀborane (1/2), adduct 3c

¹J_SeP¼ 704 Hz, PCy₂). IR (Nujol): n_max1483 m, 1437 s, 1417 w,

1386 m, 1367 m, 1344 w, 1308 m, 1296 w, 1268 w, 1198 m, 1193 m,

1175 s, 1169 m, 1101 m, 1079 w, 1072 w, 1059 m, 1038 m, 1024 m,

1000 w, 975 w, 923 w, 906 w, 891 w, 885 w, 862 w, 849 m, 841 m,

836 m, 827 w, 819 w, 813 w, 748 m, 740 s, 712 m, 704 m, 694 s, 675

w, 632 m, 620 w, 595 w, 575 s, 551 m, 536 m, 530 m, 526 m, 502 s,

480 s, 469 m, 454 m, 446 m, 432 m, 414 w cm^ꢀ1. ESI þ MS: m/z 749

([MþNa]^þ). Anal. Calc. for C₃₄H₄₀FeP₂Se₂(724.37): C 56.37, H 5.57%.

Found: C 56.32, H 5.49%.

Compound 3c was synthesized and isolated similarly to 3a using

chloro-di-tert-butylphosphine (1.2 mL, 6.0 mmol) as the phosphi-

nylating agent (Note: during the chromatographic puriﬁcation, the

product followed two minor, faster travelling bands, which were

discarded). Yield of 3c: 1.17 g (43%), orange solid. The compound

was crystallized from hot heptane.

¹H NMR (399.95 MHz, CDCl₃):

d 0.20e1.00 (br m, 6 H, BH₃), 1.19

(d, ³J_PH¼ 12.9 Hz, 18 H, CMe₃), 4.29 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.44 (vq,

4.6. Synthesis of 1⁰-(diisopropylphosphinoselenoyl)-1-

(diphenylphosphinoselenoyl)ferrocene, compound 4b

J⁰¼ 1.9 Hz, 2 H, fc), 4.51 (d of vt, J ¼ 0.9, 1.9 Hz, 2 H, fc), 4.80 (d of vt,

J ¼ 1.2, 1.9 Hz, 2 H, fc), 7.39e7.61 (m, 10 H, Ph). ¹³C{¹H} NMR

2

(100.58 MHz, CDCl₃):

d

28.55 (d, J_PC¼ 2 Hz, 6 C, CMe₃), 33.32 (d,

Compound 4b was prepared similarly, starting from 1b (103 mg,

0.2 mmol) and dabco (183 mg, 1.2 mmol) in 3 mL of toluene, and

using KSeCN (55 mg, 0.38 mmol) in dry methanol (15 mL) and

dichloromethane (5 mL) for the subsequent selenation. The product

was crystallized from a mixture of toluene (2 mL) and heptane

¹J_PC¼ 28 Hz, 2 C, CMe₃), 70.18 (d, J_PC¼ 67 Hz, 1 C, C_ipsoeP of fc),

71.78 (d, ¹J_PC¼ 49 Hz, 1 C, C_ipsoeP of fc), 73.03 (d, J_PC¼ 6 Hz, 2 C, CH

of fc), 74.24 (d, J_PC¼ 10 Hz, 2 C, CH of fc), 74.43 (d, J_PC¼ 7 Hz, 2 C, CH

of fc), 75.15 (d, J_PC¼ 7 Hz, 2 C, CH of fc), 128.52 (d, J_PC¼ 10 Hz, 4 C,

1

CH of Ph), 130.88 (d, J_PC¼ 59 Hz, 2 C, C_ipsoeP of Ph), 131.05 (d,

(13 mL). Yield of 4b: 193 mg (53%), orange crystalline solid.

⁴J_PC¼ 2 Hz, 2 C, CH of Ph), 132.61 (d, J_PC¼ 10 Hz, 4 C, CH of Ph). ³¹P

¹H NMR (399.95 MHz, CDCl₃):

d

3

1.10 (dd, J_HH¼ 7.0 Hz,

3

{¹H} NMR (161.90 MHz, CDCl₃):

d

16.3 (br d, PPh₂), 45.4 (br d,

³J_PH¼ 19.7 Hz, 6 H, CHMe₂), 1.14 (dd, J_HH¼ 7.0 Hz, J_PH¼ 20.0 Hz,

3

PtBu₂). ESI þ MS: m/z 565 ([MþNa]^þ), 581 ([MþK]^þ). Anal. Calc. for

6 H, CHMe₂), 2.21 (d of sept, J_PH¼ 8.6 Hz, J_HH¼ 7.0 Hz, 2 H,

CHMe₂), 4.35 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.53 (vq, J⁰¼ 2.1 Hz, 2 H, fc),

4.59 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.91 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 7.40e7.51

(m, 6 H, Ph), 7.66e7.74 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz,

2

3

C

₃₀H₄₂B₂FeP₂(542.05): C 66.47, H 7.81%. Found: C 66.22, H 7.72%.

4.5. Synthesis of 1⁰-(dicyclohexylphosphinoselenoyl)-1-

(diphenylphosphinoselenoyl)ferrocene, compound 4a

CDCl₃):

d

16.86 (d, ²J_PC¼ 1 Hz, 2 C, CHMe₂), 17.53 (d, ²J_PC¼ 2 Hz, 2 C,

CHMe₂), 27.72 (d, ¹J_PC¼ 45 Hz, 2 C, CHMe₂), 73.16 (d, J_PC¼ 10 Hz, 2 C,

A Schlenk tube equipped with a stirring bar was charged with

borane adduct 1a (297 mg, 0.50 mmol), dabco (229 mg, 2.0 mmol)

and anhydrous toluene (5 mL), ﬂushed with argon and sealed with

a glass stopper. After heating to 80 ^ꢁC overnight, the mixture was

cooled to room temperature and transferred to a chromatographic

column (silica gel, hexane-ethyl acetate 3:1; the mobile phase was

deoxygenated by degassing in an ultrasound bath and then by

bubbling with argon). Elution with the same solvent afforded a

single orange band, which was evaporated. The residue was dis-

solved in anhydrous dichloromethane (5 mL) and methanol (15 mL)

and added onto solid potassium selenocyanate (159 mg, 1.1 mmol).

After stirring at room temperature for 24 h, the reaction mixture

was evaporated with chromatographic silica gel. The pre-adsorbed

product was puriﬁed by column chromatography over silica gel

using toluene as the eluent. The ﬁrst yellow band was discarded

and the following, major orange red band, eluted by toluene-ethyl

acetate (20:1) to avoid tailing, was collected and evaporated to

afford the crude product, which was subsequently dissolved in a

boiling mixture of toluene (5 mL) and heptane (15 mL). The solution

was treated with little charcoal, ﬁltered and slowly cooled down to

4 ^ꢁC to afford compound 4a as an orange crystalline solid, which

was isolated by suction and dried under vacuum. Yield: 286 mg

(79%).

CH of fc), 73.85 (d, J_PC¼ 9 Hz, 2 C, CH of fc), 73.91 (d, ¹J_PC¼ 69 Hz,1 C,

C

_ipsoeP of fc), 74.61 (d, J_PC¼ 12 Hz, 2 C, CH of fc), 75.38 (d,

¹J_PC¼ 88 Hz, 1 C, C_ipsoeP of fc), 75.93 (d, J_PC¼ 10 Hz, 2 C, CH of fc),

128.31 (d, J_PC¼ 13 Hz, 4 C, CH of Ph), 131.44 (d, ⁴J_PC¼ 3 Hz, 2 C, CH of

Ph), 132.02 (d, J_PC¼ 11 Hz, 4 C, CH of Ph), 133.04 (d, ¹J_PC¼ 78 Hz, 2 C,

C

_ipsoeP of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d

31.8 (s with ⁷⁷Se

satellites, J_SeP¼ 737 Hz, PPh₂), 58.2 (s with ⁷⁷Se satellites,

¹J_SeP¼ 710 Hz, PiPr₂). IR (Nujol): n_max1435 s, 1415 w, 1405 w,

1387 m, 1368 m, 1333 w, 1308 m, 1244 w, 1188 m, 1172 s, 1099 s, 1071

w, 1063 w, 1057 w, 1043 m, 1026 m, 998 w, 965 w, 931 w, 880 m, 869

w, 850 w, 834 s, 816 w, 760 m, 742 m, 699 s, 691 m, 678 m, 646 m,

633 m, 619 w, 592 w, 571 s, 536 m, 513 m, 505 m, 489 s, 478 s, 459 w,

449 w, 438 w, 419 m, 414 w cm^ꢀ1. ESI þ MS: m/z 669 ([MþNa]^þ).

Anal. Calc. for C₂₈H₃₂FeP₂Se₂(644.25): C 52.20, H 5.01%. Found: C

52.18, H 4.74%.

1

4.7. Synthesis of 1⁰-(di-tert-butylphosphinoselenoyl)-1-

(diphenylphosphinoselenoyl)ferrocene, compound 4c

The synthesis of phosphine selenide 4c was performed as

described for 4a, starting from 1c (108 mg, 0.20 mmol) and dabco

(183 mg, 1.6 mmol) in 3 mL of toluene. The selenation was per-

formed with KSeCN (46 mg, 0.32 mmol) in a mixture of dry

methanol (10 mL) and dichloromethane (5 mL). Isolation, per-

formed as described above (2 mL of toluene and 10 mL of heptane

were used for crystallization), provided compound 4c as an orange

¹H NMR (399.95 MHz, CDCl₃):

d 1.08e1.38 (m, 10 H, Cy),

1.62e1.98 (m, 12 H, Cy), 4.30 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.50 (vq,

J⁰¼ 2.1 Hz, 2 H, fc), 4.59 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.90 (vq, J⁰¼ 1.8 Hz,

2 H, fc), 7.40e7.51 (m, 6 H, Ph), 7.66e7.73 (m, 4 H, Ph). ¹³C{¹H} NMR

crystalline solid. Yield: 54 mg (40%).

3

(100.58 MHz, CDCl₃):

d

25.73 (d, J_PC¼ 2 Hz, 2 C, CH₂of Cy), 26.35 (s,

¹H NMR (399.95 MHz, CDCl₃):

d

1.28 (d, J_PH¼ 15.6 Hz, 18 H,

2 C, CH₂of Cy), 26.37 (d, J_PC¼ 8 Hz, 2 C, CH₂of Cy), 26.52 (d,

J_PC¼ 6 Hz, 2 C, CH₂of Cy), 27.22 (d, J_PC¼ 4 Hz, 2 C, CH₂of Cy), 37.18

(d, ¹J_PC¼ 45 Hz, 2 C, CH of Cy), 73.22 (d, J_PC¼ 10 Hz, 2 C, CH of fc),

73.85 (d, J_PC¼ 9 Hz, 2 C, CH of fc), 74.35 (d, ¹J_PC¼ 69 Hz, 1 C, C_ipsoeP

of fc), 74.63 (d, J_PC¼ 12 Hz, 2 C, CH of fc), 75.28 (d, ¹J_PC¼ 88 Hz, 1 C,

CMe₃), 4.45 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.49 (vq, J⁰¼ 2.1 Hz, 2 H, fc), 4.69

(vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.91 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 7.40e7.51 (m,

6 H, Ph), 7.67e7.74 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d

28.60 (d, ²J_PC¼ 2 Hz, 6 C, CMe₃), 38.14 (d, ¹J_PC¼ 36 Hz, 2 C, CMe₃),

73.68 (d, J_PC¼ 8 Hz, 2 C, CH of fc), 74.79 (d, J_PC¼ 2 Hz, 2 C, CH of fc),

74.90 (d, J_PC¼ 5 Hz, CH of fc), 75.16 (d, ¹J_PC¼ 88 Hz, 1 C, C_ipsoeP of

fc), 76.03 (d, ¹J_PC¼ 61 Hz, 1 C, C_ipsoeP of fc), 76.18 (d, J_PC¼ 10 Hz, 2 C,

CH of fc), 128.31 (d, J_PC¼ 13 Hz, 4 C, CH of Ph), 131.42 (d, ⁴J_PC¼ 3 Hz,

2 C, CH of Ph), 132.04 (d, J_PC¼ 11 Hz, 4 C, CH of Ph), 133.12 (d,

¹J_PC¼ 78 Hz, 2 C, C_ipsoeP of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

C

_ipsoeP of fc), 75.95 (d, J_PC¼ 9 Hz, 2 C, CH of fc), 128.30 (d,

4

J_PC¼ 13 Hz, 4 C, CH of Ph), 131.43 (d, J_PC¼ 3 Hz, 2 C, CH of Ph),

1

132.00 (d, J_PC¼ 11 Hz, 4 C, CH of Ph), 133.07 (d, J_PC¼ 78 Hz, 2 C,

C

_ipsoeP of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d

31.7 (s with ⁷⁷Se

satellites, J_SeP¼ 736 Hz, PPh₂), 50.0 (s with ⁷⁷Se satellites,

1

ꢀ

24

P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

2

4

d

31.8 (s with ⁷⁷Se satellites, ¹J_SeP¼ 736 Hz, PPh₂), 74.6 (s with ⁷⁷Se

fc), 76.85 (dd, J_PC¼ 9 Hz, J_PC¼ 3 Hz, 2 C, CH of fc), 78.58 (dd,

1

3

1

satellites, J_SeP¼ 705 Hz, PtBu₂). IR (Nujol): n_max1477 m, 1436 s,

1409 w, 1366 m, 1361 m, 1332 w, 1310 m, 1195 w, 1173 m, 1158 m,

1099 m, 1072 w, 1053 w, 1037 m, 1030 m, 998 w, 946 w, 939 w, 894

w, 864 w, 848 w, 833 m, 823 m, 807 m, 759 m, 740 m, 712 m, 700 m,

689 m, 636 m, 613 w, 591 w, 595 w, 569 s, 536 m, 513 m, 492 m,

482 s, 461 w, 446 m, 418 w cm^ꢀ1. ESI þ MS: m/z 675 ([MþH]^þ), 697

([MþNa]^þ). Anal. Calc. for C₃₀H₃₆FeP₂Se₂(672.30): C 53.59, H 5.40%.

Found: C 53.47, H 5.17%.

¹J_PC¼ 43 Hz, J_PC¼ 9 Hz, 1 C, C_ipsoeP of fc), 79.33 (dd, J_PC¼ 54 Hz,

³J_PC¼ 6 Hz, 1 C, C_ipsoeP of fc), 128.45 (d, J_PC¼ 11 Hz, 4 C, CH of Ph),

4

1

131.34 (d, J_PC¼ 3 Hz, 2 C, CH of Ph), 133.06 (d, J_PC¼ 58 Hz, 2 C,

C

_ipsoeP of Ph), 135.17 (d, J_PC¼ 12 Hz, 4 C, CH of Ph). ³¹P{¹H} NMR

2

(161.90 MHz, CD₂Cl₂):

d

40.1 (d, J_PP¼ 22 Hz, PPh₂), 66.81 (br s,

PiPr₂). ESI þ MS: m/z 627 ([MeCl]^þ). Anal. Calc. For C₂₈H₃₂FeP₂PdCl₂

(663.67): C 50.67, H 4.86%. Found: C 50.64, H 4.86%.

4.10. Synthesis of dichlorido{1⁰-(di-tert-butylphosphino-

(diphenylphosphino- P)ferrocene}palladium, complex 5c

kP)-1-

4.8. Synthesis of dichlorido{1⁰-(dicyclohexylphosphino-

(diphenylphosphino- P)ferrocene}palladium, complex 5a

kP)-1-

k

Compound 5c was prepared as described above from 1c

(108 mg, 0.20 mmol), resulting in a deep red crystalline solid. Yield:

77 mg (49%). Single crystals were obtained by recrystallization from

Adduct 1a (119 mg, 0.20 mmol) and dabco (92 mg, 0.80 mmol)

were dissolved in anhydrous toluene (2 mL) in a dry Schlenk tube

equipped with a stirring bar, and the resultant mixture was stirred

at 85 ^ꢁC overnight. After cooling to room temperature, the reaction

mixture was transferred to a chromatographic column (silica gel,

hexane-ethyl acetate 3:1). The ﬁrst orange band eluted with the

same solvent was directly added to a dichloromethane solution of

[PdCl₂(cod)] (57 mg, 0.20 mmol in 1e2 mL of the solvent), imme-

diately generating an orange-red precipitate. After the addition was

completed, the mixture was stirred for 30 min and evaporated. The

residue was dissolved in dichloromethane, ﬁltered through a Celite

pad, and the ﬁltrate was precipitated by adding diethyl ether. The

formed solid was redissolved in dichloromethane, and the solution

was layered with diethyl ether and then set aside for crystallization

by liquid phase diffusion. Deep red crystals of 5a, which formed

during several days, were isolated by suction and dried under

vacuum. Yield: 109 mg (74%). Crystals for structure determination

were obtained from chloroform-hexane.

dichloromethane-diethyl ether.

3

¹H NMR (399.95 MHz, CD₂Cl₂):

d

1.61 (d, J_PH¼ 14.7 Hz, 18 H,

CMe₃), 3.96 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.30 (br m, 2 H, fc), 4.52 (br m,

2 H, fc), 4.88 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 7.46e7.53 (m, 6 H, Ph),

7.98e8.06 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CD₂Cl₂):

d 31.89

(d, ²J_PC¼ 3 Hz, 6 C, CMe₃), 41.45 (d, ¹J_PC¼ 19 Hz, 2 C, CMe₃), 72.67 (d,

³J_PC¼ 5 Hz, 2 C, CH of fc), 72.93 (d, J_PC¼ 5 Hz, 2 C, CH of fc), 76.02

3

(br m, 2 C, CH of fc), 76.90 (dd, ¹J_PC¼ 51 Hz, ³J_PC¼ 4 Hz, 1 C, C_ipsoeP

2

4

of fc), 77.86 (dd, J_PC¼ 9 Hz, J_PC¼ 3 Hz, 2 C, CH of fc), 84.65 (dd,

¹J_PC¼ 35 Hz, J_PC¼ 10 Hz, 1 C, C_ipsoeP of fc), 128.41 (d, J_PC¼ 12 Hz,

3

4

4 C, CH of Ph), 131.11 (d, J_PC¼ 2 Hz, 2 C, CH of Ph), 134.06 (d,

¹J_PC¼ 58 Hz, 2 C, C_ipsoeP of Ph), 135.14 (d, J_PC¼ 12 Hz, 4 C, CH of Ph).

³¹P{¹H} NMR (161.90 MHz, CD₂Cl₂):

d

38.8 (d, J_PP¼ 22 Hz, PPh₂),

2

81.6 (d, ²J_PP¼ 22 Hz, PtBu₂). ESI þ MS: m/z 621 ([Me2ClþH]^þ). Anal.

Calc. for C₃₀H₃₆Cl₂FeP₂Pd$0.25CH₂Cl₂(712.91): C 50.96, H 5.16%.

Found: C 50.86, H 5.15%.

¹H NMR (399.95 MHz, CD₂Cl₂):

d 1.20e1.44 (m, 8 H, Cy),

1.65e2.06 (m, 10 H, Cy), 2.38e2.48 (m, 2 H, Cy), 2.64e2.76 (m, 2 H,

Cy), 4.11 (vq, J⁰¼ 1.9 Hz, 2 H, fc), 4.35 (br m, 2 H, fc), 4.44 (br m, 2 H,

fc), 4.70 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 7.45e7.54 (m, 6 H, Ph), 7.94e8.01

4.11. Synthesis of 1⁰-(dicyclohexylphosphino)ferrocene-1-

carbaldehydeꢀborane (1/1), compound 7a

(m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CD₂Cl₂):

d

26.39 (s, 2 C, CH₂

Bromide 6a (1.43 g, 3.0 mmol) was dissolved in anhydrous THF

(30 mL) in a dry, two-necked reaction ﬂask equipped with a stirring

bar, septum and an argon inlet. The solution was cooled in a dry ice/

ethanol bath to ca. ꢀ78 ^ꢁC and then treated with n-butyllithium

(1.4 mL 2.5 M, 3.5 mmol). After stirring at ꢀ78 ^ꢁC for 20 min, dry

N,N-dimethylformamide (1.2 mL, 15 mmol) was added, changing

the color of the reaction mixture from orange red to orange yellow.

The mixture was continuously stirred and cooled for 30 min, and

then left stirring at room temperature for 90 min before quenching

by adding brine and 3 M HCl (ca. 5 mL each), subsequently diluting

with ethyl acetate. The red organic layer was separated, washed

with brine and dried over MgSO₄. The crude product was pre-

adsorbed by evaporation with chromatographic silica gel and

transferred to silica gel column. Eluting with hexane-ethyl acetate

(3:1) ﬁrstly resulted in a yellow band containing FcPCy₂$BH₃(8a)

and then in a red band due to the aldehyde 7a. Both compounds

were isolated by evaporation, resulting in an orange solid (8a;

169 mg, 14%) and a red microcrystalline solid (7a; 913 mg, 72%),

respectively. Single crystals of the aldehyde were obtained from hot

heptane.

of Cy), 27.15 (d, J_PC¼ 12 Hz, 2 C, CH₂of Cy), 27.54 (d, J_PC¼ 13 Hz, 2 C,

CH₂of Cy), 29.90 (s, 2 C, CH₂of Cy), 30.58 (s, 2 C, CH₂of Cy), 37.34 (d,

¹J_PC¼ 29 Hz, 2 C, CH of Cy), 72.77 (d, J_PC¼ 6 Hz, 2 C, CH of fc), 72.89

(d, J_PC¼ 6 Hz, 2 C, CH of fc), 74.79 (d, J_PC¼ 8 Hz, 2 C, CH of fc), 76.94

(d, J_PC¼ 9 Hz, 2 C, CH of fc), 128.42 (d, J_PC¼ 11 Hz, 4 C, CH of Ph),

4

1

131.32 (d, J_PC¼ 2 Hz, 2 C, CH of Ph), 133.09 (d, J_PC¼ 58 Hz, 2 C,

C

_ipsoeP of Ph), 135.21 (d, J_PC¼ 12 Hz, 4 C, CH of Ph). The signals due

to the ferrocene C_ipsoeP were not found. ³¹P{¹H} NMR (161.90 MHz,

2

CD₂Cl₂):

d

39.9 (d, J_PP¼ 22 Hz, PPh₂), 57.8 (d, J_PP¼ 22 Hz, PCy₂).

ESI þ MS: m/z 673 ([Me2ClþH]^þ), 707 ([MeCl]^þ). Anal. Calc. for

C

₃₄H₄₀Cl₂FeP₂Pd (743.75): C 54.90, H 5.42%. Found: C 54.53, H

5.31%.

4.9. Synthesis of dichlorido{1⁰-(diisopropylphosphino-

kP)-1-

(diphenylphosphino-kP)ferrocene}palladium, complex 5b

Complex 5b was obtained similarly to 1b (103 mg, 0.20 mmol)

and was isolated as a burgundy red crystalline solid. Yield: 64.5 mg

(49%). The crystals used for structure determination were grown

from dichloromethane-diethyl ether.

Characterization data for 7a: ¹H NMR (399.95 MHz, CDCl₃):

3

¹H NMR (399.95 MHz, CD₂Cl₂):

d

3

1.20 (dd, J_HH¼ 7.0 Hz,

d 0.18e1.06 (br m, 3 H, BH₃), 1.12e1.38 (m, 10 H, Cy), 1.66e1.74 (m,

³J_PH¼ 16.4 Hz, 6 H, CHMe₂), 1.59 (dd, J_HH¼ 7.0 Hz, J_PH¼ 17.5 Hz,

2 H, Cy), 1.78e1.98 (m, 10 H, Cy), 4.41 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.54 (d

of vt, J ¼ 0.8, 1.8 Hz, 2 H, fc), 4.74 (vt, J⁰¼ 1.9 Hz, 2 H, fc), 4.90 (vt,

J⁰¼ 2.0 Hz, 2 H, fc), 10.02 (s, 1 H, CHO). ¹³C{¹H} NMR (100.58 MHz,

3

2

3

6 H, CHMe₂), 2.93 (d of sept, J_PH¼ 9.9 Hz, J_HH¼ 7.0 Hz, 2 H,

CHMe₂), 4.13 (vq, J⁰¼ 1.9 Hz, 2 H, fc), 4.36 (br m, 2 H, fc), 4.46 (br m,

2 H, fc), 4.73 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 7.45e7.55 (m, 6 H, Ph),

CDCl₃):

d

22.87 (d, J_PC¼ 1 Hz, 2 C, CH₂of Cy), 26.78 (d, J_PC¼ 1 Hz, 2 C,

7.94e8.01 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CD₂Cl₂):

d

19.91

CH₂of Cy), 26.87 (s, 2 C, CH₂of Cy), 26.88 (d, J_PC¼ 2 Hz, 2 C, CH₂of

Cy), 27.19 (d, J_PC¼ 2 Hz, 2 C, CH₂of Cy), 32.25 (d, ¹J_PC¼ 34 Hz, 2 C, CH

of Cy), 70.81 (d, ¹J_PC¼ 54 Hz,1 C, C_ipsoeP of fc), 71.14 (s, 2 C, CH of fc),

72.00 (d, J_PC¼ 6 Hz, 2 C, CH of fc), 73.12 (d, J_PC¼ 7 Hz, 2 C, CH of fc),

2

(s, 2 C, CHMe₂), 20.15 (d, J_PC¼ 2 Hz, 2 C, CHMe₂), 27.65 (d,

¹J_PC¼ 30 Hz, 2 C, CHMe₂), 72.80 (d, J_PC¼ 6 Hz, 2 C, CH of fc), 72.97 (d,

J_PC¼ 6 Hz, 2 C, CH of fc), 74.66 (dd, ²J_PC¼ 7 Hz, ⁴J_PC¼ 1 Hz, 2 C, CH of

ꢀ

P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

25

75.21 (s, 2 C, CH of fc), 79.97 (s, 1 C, C_ipsoeCHO of fc), 193.87 (s, 1 C,

CHO). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

24.2 (br d, PCy₂). IR

4.13. Synthesis of 1-(dicyclohexylphosphino)-1⁰-(hydroxymethyl)

ferroceneꢀborane (1/1), compound 9a

d

(Nujol): n_max2378 m, 2361 m, 2334 m, 1683 s, 1667 s, 1408 w, 1342

w, 1335 w, 1309 w, 1291 w, 1267 w, 1248 m, 1199 w, 1168 m, 1132 w,

1118 w, 1067 m, 1059 m, 1042 m, 1034 m, 1006 w, 922 w, 915 w, 889

w, 878 w, 849 m, 822 m, 766 w, 757 w, 744 m, 635 w, 603 w, 523 m,

506 w, 496 w, 463 w, 443 w, 434 w cm^ꢀ1. ESI þ MS: m/z 447

([MþNa]^þ), 463 ([MþK]^þ). Anal. Calc. for C₂₃H₃₄BFeOP (424.13): C

65.13, H 8.08%. Found: C 65.14, H 7.88%.

A solution of BH₃$SMe₂(1.3 mL of 2 M in diethyl ether,

2.6 mmol) was added to a solution aldehyde 7a (0.85 g, 2.0 mmol)

in anhydrous THF (15 mL) while stirring and cooling on ice. The

reaction was allowed to proceed at 0 ^ꢁC for 90 min whereupon the

color of the reaction mixture changed from red to deep orange, and

then terminated by adding saturated aqueous NaHCO₃(1 mL). The

mixture was partitioned between dichloromethane and water, and

the organic layer was separated, washed with brine, dried over

MgSO₄, and evaporated under vacuum. The crude product was

dissolved in little dichloromethane and evaporated with chro-

matographic silica gel. The pre-adsorbed material was transferred

to silica gel column and eluted with hexane-ethyl acetate (1:1). The

single orange band eluted was collected and evaporated to afford

alcohol 9a as an orange microcrystalline solid. Yield: 813 mg (95%).

Compound 8a: ¹H NMR (399.95 MHz, CDCl₃):

d 0.16e1.04 (br m,

3 H, BH₃), 1.10e1.40 (m, 10 H, Cy), 1.64e1.72 (m, 2 H, Cy), 1.76e2.02

(m, 10 H, Cy), 4.27 (s, 5 H, C₅H₅), 4.33 (vq, J⁰¼ 1.8 Hz, 2 H, C₅H₄), 4.42

(d of vt, J ¼ 0.9, 1.8 Hz, 2 H, C₅H₄). ¹³C{¹H} NMR (100.58 MHz,

CDCl₃):

d

25.95 (d, J_PC¼ 1 Hz, 2 C, CH₂of Cy), 26.87 (s, 2 C, CH₂of

Cy), 26.88 (d, J_PC¼ 3 Hz, 2 C, CH₂of Cy), 26.99 (d, J_PC¼ 5 Hz, 2 C, CH₂

of Cy), 27.14 (d, J_PC¼ 2 Hz, 2 C, CH₂of Cy), 32.44 (d, ¹J_PC¼ 34 Hz, 2 C,

CH of Cy), 68.17 (d, ¹J_PC¼ 57 Hz, 1 C, C_ipsoeP of C₅H₄), 69.87 (s, 5 C,

C₅H₅), 70.41 (d, J_PC¼ 6 Hz, 2 C, CH of C₅H₄), 71.87 (d, J_PC¼ 8 Hz, 2 C,

¹H NMR (399.95 MHz, CDCl₃):

d 0.15e1.16 (br m, 3 H, BH₃),

CH of C₅H₄). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d

24.2 (br d, PCy₂).

1.08e1.36 (m, 10 H, Cy), 1.64e1.72 (m, 2 H, Cy), 1.76e2.03 (m, 10 H,

Cy), 4.25 (vt, J⁰¼ 1.9 Hz, 2 H, fc), 4.31 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.35 (vt,

J⁰¼ 1.9 Hz, 2 H, fc), 4.41 (br d, ³J_HH¼ 5.4 Hz, 2 H, CH₂OH), 4.43 (d of

vt, J ¼ 0.9, 1.8 Hz, 2 H, fc). The signal due to OH proton was not

ESI þ MS: m/z 419 ([MþNa]^þ), 435 ([MþK]^þ). Anal. Calc. for

C

₂₂H₃₄BFeP (396.14): C 66.70, H 8.65%. Found: C 66.64, H 8.68%.

found. ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d 24.0 (br d, PCy₂). The

NMR data are in accordance with the literature [5f].

4.12. Synthesis of 1⁰-(diisopropylphosphino)ferrocene-1-

4.14. Synthesis of 1-(diisopropylphosphino)-1⁰-(hydroxymethyl)

carbaldehydeꢀborane (1/1), compound 7b

ferroceneꢀborane (1/1), compound 9b

Using bromide 6b (1.04 g, 2.6 mmol in 25 mL of THF), 1.3 mL

2.5 M n-butyllithium and N,N-dimethylformamide (1.0 mL,

13 mmol), the procedure described in the previous section afforded

FcP(iPr)₂$BH₃(8b; 117 mg, 14%) as an orange solid, and the desired

aldehyde 7b (698 mg, 77%) as a deep red microcrystalline solid.

Crystals of 7b suitable for X-ray diffraction analysis were grown

from hot heptane.

Using the aforementioned procedure, aldehyde 7b (0.69 g,

2.0 mmol) was converted into alcohol 9b. Yield: 650 mg (92%), or-

ange microcrystalline solid. Single crystals used for structure

determination were obtained from hot heptane.

¹H NMR (399.95 MHz, CDCl₃):

d 0.20e1.06 (br m, 3 H, BH₃), 1.14

(dd, ³J_HH¼ 7.1 Hz, ³J_PH¼ 2.4 Hz, 6 H, CHMe₂), 1.17 (dd, ³J_HH¼ 7.1 Hz,

³J_PH¼ 3.5 Hz, 6 H, CHMe₂), 1.97 (t, ³J_HH¼ 5.8 Hz, 1 H, CH₂OH), 2.13 (d

2

3

Characterization data for 7b: ¹H NMR (399.95 MHz, CDCl₃):

of sept, J_PH¼ 10.1 Hz, J_HH¼ 7.1 Hz, 2 H, CHMe₂), 4.28 (vt,

J⁰¼ 1.9 Hz, 2 H, fc), 4.34 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.36 (vt, J⁰¼ 1.9 Hz,

3

d

0.18e1.04 (br m, 3 H, BH₃), 1.15 (dd, J_HH¼ 7.1 Hz, J_PH¼ 2.9 Hz,

6 H, CHMe₂), 1.18 (dd, ³J_HH¼ 7.1 Hz, ³J_PH¼ 3.9 Hz, 6 H, CHMe₂), 2.14

2 H, fc), 4.42 (d, J_HH¼ 5.6 Hz, 2 H, CH₂OH), 4.45 (d of vt, J ¼ 0.9,

3

2

3

(d of sept, J_PH¼ 10.1 Hz, J_HH¼ 7.1 Hz, 2 H, CHMe₂), 4.43 (vq,

J⁰¼ 1.8 Hz, 2 H, fc), 4.55 (d of vt, J ¼ 0.9, 1.9 Hz, 2 H, fc), 4.76 (vt,

J⁰¼ 1.8 Hz, 2 H, fc), 4.92 (vt, J⁰¼ 1.9 Hz, 2 H, fc), 10.04 (s, 1 H, CHO).

1.9 Hz, 2 H, fc). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d 17.12 (s, 2 C,

CHMe₂), 17.36 (d, ²J_PC¼ 2 Hz, 2 C, CHMe₂), 22.46 (d, ¹J_PC¼ 35 Hz, 2 C,

CHMe₂), 60.43 (s, 1 C, CH₂OH), 67.87 (d, ¹J_PC¼ 56 Hz, 1 C, C_ipsoeP of

fc), 69.28 (s, 2 C, CH of fc), 70.04 (s, 2 C, CH of fc), 70.91 (d, J_PC¼ 6 Hz,

2 C, CH of fc), 72.22 (d, J_PC¼ 7 Hz, 2 C, CH of fc), 89.79 (s, 1 C, C_ip-

¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d 17.12 (s, 2 C, CHMe₂), 17.41 (d,

²J_PC¼ 2 Hz, 2 C, CHMe₂), 22.49 (d, ¹J_PC¼ 34 Hz, 2 C, CHMe₂), 70.13 (d,

¹J_PC¼ 53 Hz, 1 C, C_ipsoeP of fc), 71.16 (s, 2 C, CH of fc), 72.12 (d,

J_PC¼ 6 Hz, 2 C, CH of fc), 73.02 (d, J_PC¼ 7 Hz, 2 C, CH of fc), 72.21 (s,

_soeCH₂OH of fc). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d 31.6 (br m,

PiPr₂). IR (Nujol): n_max3242 br m, 3098 m, 3078 m, 2378 s, 2352 s,

2327 s, 2251 m, 1713 w, 1652 w, 1313 w, 1250 m, 1239 m, 1230 w,

1202 w, 1167 s, 1134 w, 1105 w, 1068 s, 1037 s, 1022 m, 983 m, 954 w,

926 w, 916 w, 888 m, 867 w, 842 m, 835 w, 813 m, 750 m, 691 m,

638 m, 631 m, 586 m, 521 m, 515 m, 492 m, 483 w, 466 m, 450 w, 420

w cm^ꢀ1. ESI þ MS: m/z 369 ([MþNa]^þ), 385 ([MþK]^þ). Anal. Calc. for

2 C, CH of fc), 79.97 (s, 1 C, C_ipsoeCHO of fc), 193.92 (s, 1 C, CHO). ³¹

P

{¹H} NMR (161.90 MHz, CDCl₃):

d 31.9 (br d, PiPr₂). IR (Nujol): n_max

2371 m, 2364 m, 2329 m, 1686 s, 1671 m, 1414 w, 1338 w, 1315 w,

1247 m, 1205 w, 1169 m, 1135 w, 1068 m, 1037 m, 932 w, 888 w,

844 m, 828 m, 741 m, 693 m, 633 m, 589 w, 523 m, 506 m, 489 w,

463 w, 436 w cm^ꢀ1. ESI þ MS: m/z 367 ([MþNa]^þ), 383 ([MþK]^þ).

Anal. Calc. for C₁₇H₂₆BFeOP (344.01): C 59.35, H 7.62%. Found: C

59.29, H 7.48%.

C₁₇H₂₈BFeOP (346.03): C 59.00, H 8.16%. Found: C 59.03, H 8.01%.

4.15. Synthesis of 1⁰-(dicyclohexylphosphino)-1-

Compound 8b: ¹H NMR (399.95 MHz, CDCl₃):

d

0.17e1.02 (br m,

[(diphenylphosphino)methyl]ferroceneꢀborane (1/2), compound

3 H, BH₃), 1.14 (dd, ³J_HH¼ 7.1 Hz, ³J_PH¼ 1.8 Hz, 6 H, CHMe₂), 1.18 (dd,

10a

3

³J_HH¼ 7.1 Hz, J_PH¼ 2.8 Hz, 6 H, CHMe₂), 2.13 (d of sept,

3

²J_PH¼ 10.1 Hz, J_HH¼ 7.1 Hz, 2 H, CHMe₂), 4.29 (s, 5 H, C₅H₅), 4.35

Alcohol 9a (0.77 g, 1.8 mmol) and NaI (0.82 g, 5.5 mmol) were

dissolved in dry acetonitrile (60 mL). Neat chloro-trimethylsilane

(0.56 mL, 4.4 mmol) was added to a stirring mixture, causing an

immediate separation of a ﬁne white precipitate (NaCl). After stir-

ring for 5 min, diphenylphosphine (0.84 mL, 4.8 mmol) was intro-

duced, and the reaction mixture was stirred at room temperature

for 18 h. Then, BH₃$SMe₂(2.7 mL of a 2 M ethereal solution,

5.3 mmol) was added, continuously stirring for another 5 min. The

reaction mixture was quenched by saturated aqueous NaHCO₃

(vq, J⁰¼ 1.7 Hz, 2 H, CH of C₅H₄), 4.43 (d of vt, J ¼ 0.9, 1.9 Hz, 2 H, CH

of C₅H₄). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d 17.16 (s, 2 C, CHMe₂),

17.41 (d, ²J_PC¼ 2 Hz, 2 C, CHMe₂), 22.57 (d, ¹J_PC¼ 35 Hz, 2 C, CHMe₂),

67.45 (d, ¹J_PC¼ 56 Hz,1 C, C_ipsoeP of C₅H₄), 69.89 (s, 5 C, C₅H₅), 70.51

(d, J_PC¼ 6 Hz, 2 C, CH of C₅H₄), 71.77 (d, J_PC¼ 7 Hz, 2 C, CH of C₅H₄).

³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d

31.8 (br m, PiPr₂). ESI þ MS: m/

z 315 ([MeH]^þ), 339 ([MþNa]^þ), 355 ([MþK]^þ). Anal. Calc. for

C

₁₆H₂₆BFeP (316.01): C 60.81, H 8.29%. Found: C 60.79, H 8.19%.

ꢀ

P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

26

(5 mL) and diluted with diethyl ether (60 mL) and brine (20 mL).

The organic layer was separated, washed with brine, dried over

MgSO₄, and evaporated. The solid residue was dissolved in

dichloromethane and evaporated with chromatographic silica gel,

and the pre-adsorbed crude product was transferred to a chro-

matographic column. After elution with hexane removed some

colorless HPPh₂$BH₃, the mobile phase was changed to hexane-

toluene (1:3), which afforded a minor band containing compound

11a (150 mg, 20%; yellow-orange solid). Subsequent elution

removed a minor band containing some impurities and, ﬁnally, an

orange band due to 10a. This band was collected and evaporated

under reduced pressure to afford adduct 10a as an orange micro-

crystalline product. Yield: 300 mg (27%).

C

_ipsoeP of fc), 69.54 (s, 2 C, CH of fc), 71.34 (d, J_PC¼ 6 Hz, 2 C, CH of

fc), 71.99 (d, J_PC¼ 2 Hz, 2 C, CH of fc), 72.90 (d, J_PC¼ 7 Hz, 2 C, CH of

fc), 80.39 (d, ²J_PC¼ 2 Hz, 1 C, C_ipsoeCH₂of fc), 128.59 (d, J_PC¼ 10 Hz,

4 C, CH of Ph), 128.77 (d, ¹J_PC¼ 54 Hz, 2 C, C_ipsoeP of Ph), 131.14 (d,

⁴J_PC¼ 2 Hz, 2 C, CH of Ph), 132.67 (d, J_PC¼ 9 Hz, 4 C, CH of Ph). ³¹P

{¹H} NMR (161.90 MHz, CDCl₃):

d 17.2 (br d, PPh₂), 31.6 (br d, PiPr₂).

ESI þ MS: m/z 551 ([MþNa]^þ), 567 ([MþK]^þ); ESIe MS: m/z 527

([MeH]^e). Anal. Calc. for C₂₉H₄₀B₂FeP₂(528.04): C 65.96, H 7.64%.

Found: C 65.82, H 7.63%.

Compound 11b: yellow-orange solid. ¹H NMR (399.95 MHz,

3

CDCl₃):

d

0.18e1.03 (br m, 3 H, BH₃), 1.14 (dd, J_HH¼ 7.1 Hz,

³J_PH¼ 3.5 Hz, 6 H, CHMe₂), 1.18 (dd, ³J_HH¼ 7.1 Hz, ³J_PH¼ 4.5 Hz, 6 H,

CHMe₂),1.99 (s, 3 H, Me), 2.13 (d of sept, ²J_PH¼ 10.1 Hz, ³J_HH¼ 7.1 Hz,

2 H, CHMe₂), 4.16 (vt, J⁰¼ 1.8 Hz, 2 H, fc), 4.19 (vt, J⁰¼ 1.8 Hz, 2 H, fc),

4.25 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.33 (d of vt, J ¼ 0.9, 1.8 Hz, 2 H, fc). ¹³C

Characterization data for 10a. ¹H NMR (399.95 MHz, CDCl₃):

d

0.20e1.05 (br m, 6 H, BH₃), 1.08e1.36 (m, 10 H, Cy), 1.52e1.95 (m,

12 H, Cy), 3.50 (d, ²J_PH¼ 10.4 Hz, 2 H, CH₂PPh₂), 4.05 (s, 4 H, fc), 4.18

(vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.38 (d of vt, J ¼ 0.9, 1.8 Hz, 2 H, fc),

7.38e7.49 (m, 6 H, Ph), 7.61e7.67 (m, 4 H, Ph). ¹³C{¹H} NMR

{¹H} NMR (100.58 MHz, CDCl₃):

d 14.76 (s, 1 C, Me), 17.44 (s, 2 C,

CHMe₂), 17.69 (d, ²J_PC¼ 2 Hz, 2 C, CHMe₂), 22.85 (d, ¹J_PC¼ 35 Hz, 2 C,

CHMe₂), 67.47 (d, ¹J_PC¼ 57 Hz, 1 C, C_ipsoeP of fc), 69.69 (s, 2 C, CH of

fc), 71.07 (s, 2 C, CH of fc), 71.98 (d, J_PC¼ 7 Hz, 2 C, CH of fc), 72.63 (d,

J_PC¼ 8 Hz, 2 C, CH of fc), 85.76 (s, 1 C, C_ipsoeCH₃of fc). ³¹P{¹H} NMR

(100.58 MHz, CDCl₃):

d

25.91 (d, J_PC¼ 1 Hz, 2 C, CH₂of Cy), 26.79 (s,

2 C, CH₂of Cy), 26.82 (d, J_PC¼ 6 Hz, 2 C, CH₂of Cy), 26.93 (d,

J_PC¼ 8 Hz, 2 C, CH₂of Cy), 27.06 (d, J_PC¼ 2 Hz, 2 C, CH₂of Cy), 28.49

(d, ¹J_PC¼ 34 Hz, 1 C, CH₂PPh₂), 32.29 (d, ¹J_PC¼ 34 Hz, 2 C, CH of Cy),

68.38 (d, ¹J_PC¼ 56 Hz, 1 C, C_ipsoeP of fc), 69.56 (s, 2 C, CH of fc), 71.25

(d, J_PC¼ 7 Hz, 2 C, CH of fc), 71.94 (d, J_PC¼ 2 Hz, 2 C, CH of fc), 73.00

(161.90 MHz, CDCl₃):

d

31.7 (br m, PiPr₂). ESI þ MS: m/z 329

([MeH]^þ), 353 ([MþNa]^þ), 369 ([MþK]^þ). Anal. Calc. for C₁₇H₂₈BFeP

(330.03): C 61.87, H 8.55%. Found: C 62.10, H 8.47%.

2

(d, J_PC¼ 8 Hz, 2 C, CH of fc), 80.34 (d, J_PC¼ 2 Hz, 1 C, C_ipsoeCH₂of

4.17. Synthesis of 1⁰-(dicyclohexylphosphino)-1-

[(diphenylphosphino)methyl]ferrocene (2a) from 10a

fc), 128.59 (d, J_PC¼ 10 Hz, 4 C, CH of Ph), 128.79 (d, ¹J_PC¼ 53 Hz, 2 C,

4

C

_ipsoeP of Ph), 131.14 (d, J_PC¼ 2 Hz, 2 C, CH of Ph), 132.66 (d,

J_PC¼ 9 Hz, 4 C, CH of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d

17.3

An oven-dried Schlenk tube was charged with adduct 10a

(122 mg, 0.20 mmol), ﬁlled with argon (by three vacuum-argon

cycles) and sealed with a septum. Freshly distilled morpholine

(2.0 mL) was added, and the mixture was cooled in dry ice/ethanol

bath until solidiﬁcation, evacuated and then allowed to thaw at

room temperature. This cooling-warming procedure was repeated

three or four times until no gas evolution was observed upon

thawing. Then, the reaction mixture was heated to 70 ^ꢁC overnight

and evaporated, leaving an orange residue, which was puriﬁed by

column chromatography (silica gel, hexane-ethyl acetate 3:1). The

single orange band was collected and evaporated to afford com-

pound 2a as a gummy orange-red solid. Yield 66 mg (57%). The

product typically contained minor amounts of Ph₂PCH₂fcPCy₂$BH₃

[5e10%; ³¹P{¹H} NMR (CDCl₃): ꢀ11.0 (s, PPh₂), 24.1 (br m, PCy₂)].

For analytical data of 2a, see section 4.19.

(br d, PPh₂), 23.9 (br d, PCy₂). ESI þ MS: m/z 609 ([MþH]^þ), 631

([MþNa]^þ), ESIe MS: m/z 607 ([MeH]^e). Anal. Calc. for

C

₃₅H₄₈B₂FeP₂(608.17): C 69.12, H 7.96%. Found: C 68.89, H 7.90%.

Compound 11a. ¹H NMR (399.95 MHz, CDCl₃):

d 0.16e1.04 (br m,

3 H, BH₃), 1.10e1.40 (m, 10 H, Cy), 1.64e1.99 (m, 12 H, Cy), 1.99 (s,

3 H, Me), 4.14 (vt, J⁰¼ 1.8 Hz, 2 H, fc), 4.17 (vt, J⁰¼ 1.8 Hz, 2 H, CH of

fc), 4.23 (vt, J⁰¼ 1.7 Hz, 2 H, CH of fc), 4.32 (d of vt, J ¼ 0.9,1.8 Hz, 2 H,

fc). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d 14.50 (s, 1 C, Me), 25.97 (d,

J_PC¼ 2 Hz, 2 C, CH₂of Cy), 26.89 (d, J_PC¼ 3 Hz, 2 C, CH₂of Cy), 26.92

(s, 2 C, CH₂of Cy), 27.00 (d, J_PC¼ 4 Hz, 2 C, CH₂of Cy), 27.17 (d,

J_PC¼ 2 Hz, 2 C, CH₂of Cy), 32.49 (d, ¹J_PC¼ 35 Hz, 2 C, CH of Cy), 67.99

(d, ¹J_PC¼ 57 Hz, 1 C, C_ipsoeP of fc), 69.39 (s, 2 C, CH of fc), 70.79 (s,

2 C, CH of fc), 71.57 (d, J_PC¼ 7 Hz, 2 C, CH of fc), 72.48 (d, J_PC¼ 8 Hz,

2 C, CH of fc), 85.45 (s, 1 C, C_ipsoeCH₃of fc). ³¹P{¹H} NMR

(161.90 MHz, CDCl₃):

d

24.1 (br d, PCy₂). ESI þ MS: m/z 433

([MþNa]^þ), 449 ([MþK]^þ). Anal. Calc. for C₂₃H₃₆BFeP (410.16): C

4.18. Synthesis of 1⁰-(diisopropylphosphino)-1-

[(diphenylphosphino)methyl]ferrocene (2b) from 10b

67.35, H 8.85%. Found: C 67.22, H 8.55%.

4.16. Synthesis of 1⁰-(diisopropylphosphino)-1-

Applying a similar deprotection procedure, compound 10b

(106 mg, 0.20 mmol) was converted to pure 2b as a red-orange oil.

Yield: 76 mg (76%). For analytical data of 2b, see section 4.20.

[(diphenylphosphino)methyl]ferroceneꢀborane (1/2), compound

10b

Reacting alcohol 9b (0.65 g,1.9 mmol) and NaI (0.82 g, 5.5 mmol)

in 40 mL of acetonitrile with ClSiMe₃(0.58 mL, 4.5 mmol), HPPh₂

(0.88 mL, 5.0 mmol) and, ﬁnally, BH₃$SMe₂(2.7 ml 2 M, 5.3 mmol)

as described above provided 11b (ﬁrst yellow band; 136 mg, 22%)

and adduct 10b (third orange band; 325 mg, 33%).

4.19. Synthesis of 2a from 13

Bromide 13 (0.463 g, 1.0 mmol) was dissolved in THF (10 mL) in

an oven-dried ﬂask equipped with a stirring bar, a rubber septum

and a gas inlet. The solution was cooled in a dry ice/ethanol bath to

ca. ꢀ78 ^ꢁC before adding a solution of n-butyllithium (0.44 mL

2.5 M, 1.1 mmol) dropwise. After the mixture was stirred, continu-

ously cooling for 30 min, neat chlorodicyclohexylphosphine

(0.25 mL, 1.2 mmol) was introduced continuously stirring at ꢀ78 ^ꢁC

for 30 min and then at room temperature for 90 min. Subsequently,

the reaction was terminated by adding brine (3 mL) and diethyl

ether (15 mL), both carefully degassed to avoid oxidation. The

aqueous layer was removed using a syringe, and the remaining

organic residue was dried by adding anhydrous magnesium sulfate,

ﬁltered and evaporated under reduced pressure. The residue was

Characterization data for 10b: yellow-orange microcrystalline

solid. ¹H NMR (399.95 MHz, CDCl₃):

d 0.26e0.98 (br m, 6 H, BH₃),

3

1.11 (dd, J_HH¼ 7.1 Hz, J_PH¼ 15.4 Hz, 6 H, CHMe₂), 1.15 (dd,

3

³J_HH¼ 7.1 Hz, J_PH¼ 16.5 Hz, 6 H, CHMe₂), 2.11 (d of sept,

3

2

²J_PH¼ 10.0 Hz, J_HH¼ 7.1 Hz, 2 H, CHMe₂), 3.53 (d, J_PH¼ 10.4 Hz,

2 H, CH₂PPh₂), 4.08 (s, 4 H, fc), 4.21 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.40 (d of

vt, J ¼ 0.9, 1.8 Hz, 2 H, fc), 7.39e7.50 (m, 6 H, Ph), 7.62e7.68 (m, 4 H,

Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d 17.10 (s, 2 C, CHMe₂), 17.33

1

2

(d, J_PC¼ 2 Hz, 2 C, CHMe₂), 22.42 (d, J_PC¼ 35 Hz, 2 C, CHMe₂),

1

28.47 (d, J_PC¼ 34 Hz, 1 C, CH₂PPh₂), 67.61 (d, J_PC¼ 56 Hz, 1 C,

ꢀ

P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

27

puriﬁed by ﬂash chromatography over silica gel using deoxygen-

4.22. Synthesis of 1⁰-(dicyclohexylphosphinoselenoyl)-1-

ated toluene as the eluent. The ﬁrst orange band containing mostly

FcCH₂PPh₂[41] was discarded, and the following band due to the

diphosphine 2a was collected and evaporated, affording the prod-

uct as an orange red gummy solid (300 mg, 52%).

[(diphenylphosphinoselenoyl)methyl]ferrocene (14a)

Diphosphine 2a (29 mg, 50 mmol) and KSeCN (16 mg, 0.11 mmol)

were reacted in anhydrous dichloromethane and methanol (2 mL

each) overnight. The resulting mixture was evaporated under

¹H NMR (399.95 MHz, CDCl₃):

d 0.98e1.34 (m, 10 H, Cy),

1.60e1.92 (m, 12 H, Cy), 3.16 (s, 2 H, CH₂PPh₂), 3.87 (vt, J⁰¼ 1.8 Hz,

2 H, fc), 3.95 (vt, J⁰¼ 1.8 Hz, 2 H, fc), 4.07 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.20

(vt, J⁰¼ 1.7 Hz, 2 H, fc), 7.29e7.33 (m, 6 H, Ph), 7.36e7.42 (m, 4 H,

vacuum, and the residue was dissolved in a minimum of

dichloromethane and puriﬁed by column chromatography on silica

gel using hexane-toluene-ethyl acetate (1:1:1) as the eluent. A

single orange band was collected and evaporated to afford the

phosphine selenide as an orange solid (35 mg, 95%). Additional

puriﬁcation was achieved by recrystallization from hot toluene-

heptane (ca. 1:4). Yield of crystalline 14a: 31 mg (84%).

Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

d 26.45 (s, 2 C, CH₂of Cy),

27.34 (d, J_PC¼ 9 Hz, 2 C, CH₂of Cy), 27.41 (d, J_PC¼ 11 Hz, 2 C, CH₂of

Cy), 30.00 (d, ¹J_PC¼ 15 Hz, 1 C, CH₂PPh₂), 30.30 (d, J_PC¼ 13 Hz, 2 C,

CH₂of Cy), 30.40 (d, J_PC¼ 11 Hz, 2 C, CH₂of Cy), 33.56 (d,

¹J_PC¼ 11 Hz, 2 C, CH of Cy), 69.00 (s, 2 C, CH of fc), 70.13 (d,

J_PC¼ 4 Hz, 2 C, CH of fc), 70.60 (d, J_PC¼ 3 Hz, 2 C, CH of fc), 72.25 (d,

¹H NMR (399.95 MHz, CDCl₃):

d 1.10e1.42 (m, 10 H, Cy),

1.63e2.04 (m, 12 H, Cy), 4.07 (vt, J⁰¼ 1.9 Hz, 2 H, fc), 4.14 (d,

²J_PH¼ 11.7 Hz, 2 H, CH₂P(Se)Ph₂), 4.19 (d of vt, J ¼ 1.1, 1.8 Hz, 2 H, fc),

4.25 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.42 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 7.40e7.49

(m, 6 H, Ph), 7.83e7.90 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz,

1

J_PC¼ 11 Hz, 2 C, CH of fc), 76.38 (d, J_PC¼ 16 Hz, 1 C, C_ipsoeP of fc),

84.62 (d, ²J_PC¼ 16 Hz, 1 C, C_ipsoeCH₂of fc), 128.27 (d, J_PC¼ 6 Hz, 4 C,

CH of Ph), 128.56 (s, 2 C, CH of Ph), 132.87 (d, J_PC¼ 19 Hz, 4 C, CH of

1

Ph), 138.62 (d, J_PC¼ 15 Hz, 2 C, C_ipsoeP of Ph). ³¹P{¹H} NMR

CDCl₃):

d

25.76 (d, J_PC¼ 2 Hz, 2 C, CH₂of Cy), 26.32 (d, J_PC¼ 2 Hz, 2 C,

(161.90 MHz, CDCl₃):

d

ꢀ11.5 (s, PPh₂), ꢀ7.1 (s, PCy₂). HR MS (ESIþ)

CH₂of Cy), 26.40 (d, J_PC¼ 2 Hz, 2 C, CH₂of Cy), 26.53 (d, J_PC¼ 1 Hz,

2 C, CH₂of Cy), 27.21 (d, J_PC¼ 3 Hz, 2 C, CH₂of Cy), 36.18 (d,

¹J_PC¼ 44 Hz, 1 C, CH₂P(Se)Ph₂), 37.15 (d, ¹J_PC¼ 45 Hz, 2 C, CH of Cy),

69.74 (s, 2 C, CH of fc), 70.96 (d, J_PC¼ 9 Hz, 2 C, CH of fc), 72.75 (d,

¹J_PC¼ 71 Hz, 1 C, C_ipsoeP of fc), 72.93 (d, J_PC¼ 2 Hz, 2 C, CH of fc),

73.26 (d, J_PC¼ 10 Hz, 2 C, CH of fc), 79.97 (s, 1 C, C_ipsoeCH₂of fc),

56

calc. for C H

35 43

FeP₂([MþH]^þ): 581.2184, found 581.2183.

4.20. Synthesis of 2b from 13

A similar reaction with chlorodiisopropylphosphine (0.20 mL,

1.2 mmol) furnished diphosphine 2b as an orange-red oil (354 mg,

1

128.41 (d, J_PC¼ 12 Hz, 4 C, CH of Ph), 130.99 (d, J_PC¼ 71 Hz, 2 C,

C

_ipsoeP of Ph), 131.41 (d, J_PC¼ 3 Hz, 2 C, CH of Ph), 132.23 (d,

71%).

J_PC¼ 10 Hz, 4 C, CH of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d 34.0

3

¹H NMR (399.95 MHz, CDCl₃):

d

3

1.05 (dd, J_HH¼ 7.0 Hz,

(s with ⁷⁷Se satellites, J_SeP¼ 729 Hz, PPh₂), 50.4 (s with ⁷⁷Se sat-

ellites, ¹J_SeP¼ 696 Hz, PCy₂). IR (Nujol): n_max1587 w, 1574 w, 1437 m,

1414 w, 1400 w, 1344 w, 1310 w, 1291 w, 1264 w, 1239 w, 1195 m,

1180 m, 1168 m, 1114 w, 1099 m, 1069 w, 1041 m, 1033 m, 1003 m,

924 m, 903 w, 886 w, 863 w, 849 m, 836 s, 830 m, 823 m, 756 m,

747 m, 738 s, 693 s, 628 m, 619 w, 606 m, 551 m, 531 m, 524 s, 509 w,

500 m, 490 m, 479 s, 456 m, 432 w, 418 w cm^ꢀ1. ESI þ MS: m/z 741

([MþH]^þ), 763 ([MþNa]^þ). Anal. Calc. for C₃₅H₄₂FeP₂Se₂(738.42): C

56.93, H 5.73%. Found: C 56.50, H 5.57%.

1

³J_PH¼ 12.1 Hz, 6 H, CHMe₂), 1.08 (dd, J_HH¼ 7.1 Hz, J_PH¼ 13.8 Hz,

3

2

3

6 H, CHMe₂), 1.90 (d of sept, J_PH¼ 2.7 Hz, J_HH¼ 7.0 Hz, 2 H,

CHMe₂), 3.17 (s, 2 H, CH₂PPh₂), 3.89 (vt, J⁰¼ 1.8 Hz, 2 H, fc), 3.96 (vt,

J⁰¼ 1.8 Hz, 2 H, fc), 4.10 (vq, J⁰¼ 1.8 Hz, 2 H, fc), 4.21 (vt, J⁰¼ 1.8 Hz,

2 H, fc), 7.30e7.42 (m, 10 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

2

d

19.98 (d, J_PC¼ 11 Hz, 2 C, CHMe₂), 20.14 (d, J_PC¼ 15 Hz, 2 C,

1

CHMe₂), 23.44 (d, J_PC¼ 11 Hz, 2 C, CHMe₂), 29.99 (d, J_PC¼ 15 Hz,

1 C, CH₂PPh₂), 69.08 (s, 2 C, CH of fc), 70.14 (d, J_PC¼ 4 Hz, 2 C, CH of

fc), 70.69 (d, J_PC¼ 2 Hz, 2 C, CH of fc), 71.98 (d, J_PC¼ 11 Hz, 2 C, CH of

1

2

fc), 76.01 (d, J_PC¼ 17 Hz, 1 C, C_ipsoeP of fc), 84.61 (d, J_PC¼ 16 Hz,

1 C, C_ipsoeCH₂of fc), 128.28 (d, J_PC¼ 6 Hz, 4 C, CH of Ph), 128.56 (s,

2 C, CH of Ph), 132.88 (d, J_PC¼ 19 Hz, 4 C, CH of Ph), 138.60 (d,

4.23. Synthesis of 1⁰-(diisopropylphosphinoselenoyl)-1-

[(diphenylphosphinoselenoyl)methyl]ferrocene (14b)

¹J_PC¼ 15 Hz, 2 C, C_ipsoeP of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

Starting with diphosphine 2b (25 mg, 50 mmol), the same pro-

cedure afforded compound 14b as orange crystalline solid (27 mg,

82%).

56

d

ꢀ11.5 (s, PPh₂), 0.9 (s, PiPr₂). HR MS (ESIþ) calc. for C₂₉

H FeP₂

35

([MþH]^þ): 501.1558, found 501.1555.

¹H NMR (399.95 MHz, CDCl₃):

d

1.14 (dd, J_HH¼ 7.0 Hz,

3

4.21. Synthesis of 1⁰-(di-tert-butylphosphino)-1-

[(diphenylphosphino)methyl]ferrocene (2c)

³J_PH¼ 17.5 Hz, 6 H, CHMe₂), 1.19 (dd, J_HH¼ 7.0 Hz, J_PH¼ 17.8 Hz,

2

3

6 H, CHMe₂), 2.26 (d of sept, J_PH¼ 8.3 Hz, J_HH¼ 7.0 Hz, 2 H,

2

CHMe₂), 4.09 (vt, J⁰¼ 1.9 Hz, 2 H, fc), 4.14 (d, J_PH¼ 11.7 Hz, 2 H,

Compound 2c was similarly prepared using chloro-di-tert-

butylphosphine (0.24 mL, 1.2 mmol), resulting in a red-orange oil

CH₂P(Se)Ph₂), 4.19 (d of vt, J ¼ 1.0, 1.8 Hz, 2 H, fc), 4.27 (vq,

J⁰¼ 1.7 Hz, 2 H, fc), 4.43 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 7.40e7.47 (m, 6 H,

(380 mg, 72%).

Ph), 7.83e7.90 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

3

2

¹H NMR (399.95 MHz, CDCl₃):

d

1.17 (d, J_PH¼ 11.2 Hz, 18 H,

d

16.80 (s, 2 C, CHMe₂), 17.45 (d, J_PC¼ 2 Hz, 2 C, CHMe₂), 27.63 (d,

1

CMe₃), 3.16 (s, 2 H, CH₂PPh₂), 3.90 (vt, J⁰¼ 1.7 Hz, 2 H, fc), 3.98 (vt,

J⁰¼ 1.8 Hz, 2 H, fc), 4.18 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.26 (vt, J⁰¼ 1.8 Hz,

2 H, fc), 7.29e7.42 (m, 10 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

¹J_PC¼ 45 Hz, 2 C, CHMe₂), 36.17 (d, J_PC¼ 44 Hz, 1 C, CH₂P(Se)Ph₂),

69.73 (s, 2 C, CH of fc), 71.03 (d, J_PC¼ 9 Hz, 2 C, CH of fc), 72.04 (d,

¹J_PC¼ 71 Hz, 1 C, C_ipsoeP of fc), 72.99 (d, J_PC¼ 2 Hz, 2 C, CH of fc),

73.18 (d, J_PC¼ 10 Hz, 2 C, CH of fc), 79.98 (s, 1 C, C_ipsoeCH₂of fc),

1

2

d

30.02 (d, J_PC¼ 15 Hz, 1 C, CH₂PPh₂), 30.80 (d, J_PC¼ 13 Hz, 6 C,

1

CMe₃), 32.62 (d, J_PC¼ 20 Hz, 2 C, CMe₃), 69.63 (s, 2 C, CH of fc),

70.34 (d, J_PC¼ 4 Hz, 2 C, CH of fc), 70.55 (d, J_PC¼ 3 Hz, 2 C, CH of fc),

73.70 (d, J_PC¼ 13 Hz, 2 C, CH of fc), 77.86 (d, ¹J_PC¼ 27 Hz, 1 C, C_ipsoeP

128.40 (d, J_PC¼ 12 Hz, 4 C, CH of Ph), 130.94 (d, J_PC¼ 71 Hz, 2 C,

C

_ipsoeP of Ph), 131.43 (d, J_PC¼ 3 Hz, 2 C, CH of Ph), 132.24 (d,

J_PC¼ 10 Hz, 4 C, CH of Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d 34.0

2

1

of fc), 84.53 (d, J_PC¼ 16 Hz, 1 C, C_ipsoeCH₂of fc), 128.29 (d,

(s with ⁷⁷Se satellites, J_SeP¼ 729 Hz, PPh₂), 58.8 (s with ⁷⁷Se sat-

ellites, ¹J_SeP¼ 702 Hz, PiPr₂). IR (Nujol): n_max1483 m, 1435 s, 1415 w,

1400 m, 1310 w, 1291 w, 1242 m, 1213 w, 1197 w, 1178 m, 1169 m,

1158 w, 1114 w, 1094 s, 1065 w, 1042 m, 1028 s, 997 w, 973 w, 929 m,

891 w, 885 w, 875 w, 842 m, 836 m, 827 m, 820 m, 806 m, 759 m,

749 m, 697 s, 675 m, 656 m, 627 w, 603 m, 563 m, 527 s, 513 m,

J_PC¼ 6 Hz, 4 C, CH of Ph), 128.59 (s, 2 C, CH of Ph), 132.87 (d,

J_PC¼ 19 Hz, 4 C, CH of Ph), 138.56 (d, ¹J_PC¼ 15 Hz, 2 C, C_ipsoeP of Ph).

³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d

ꢀ11.6 (s, PPh₂), 28.3 (s, PtBu₂).

56

HR MS (ESIþ) calc. for C

H

FeP₂([MþH]^þ): 529.1871, found

31 39

529.1862.

ꢀ

P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

28

505 m, 494 m, 483 m, 476 m, 441 w, 429 w, 418 w cm^ꢀ1. ESI þ MS: m/

z 683 ([MþNa]^þ). Anal. Calc. for C₂₉H₃₄FeP₂Se₂(658.29): C 52.91, H

5.21%. Found: C 52.67, H 5.05%.

described above furnished red crystalline product (22 mg) con-

taining the chelate complex 15b and dimer 16b. Single crystals of

16b were obtained from dichloromethane-diethyl ether. ESI þ MS:

m/z 605 ([MeCleHCl]^þ), 641 ([MeCl]^þ). Anal. Calc. for

4.24. Synthesis of 1⁰-(di-tert-butylphosphinoselenoyl)-1-

C₂₉H₃₄Cl₂FeP₂Pd$0.25CHCl₃(701.57): C 49.99, H 4.91%. Found: C

[(diphenylphosphinoselenoyl)methyl]ferrocene (14c)

49.86, H 4.75%.

Compound 15b. ¹H NMR (399.95 MHz, CDCl₃):

d 1.29 (dd,

3

Diphosphine 2c (53 mg, 0.10 mmol), KSeCN (32 mg, 0.22 mmol)

were reacted in a mixture of methanol (5 mL) and dichloromethane

(4 mL), as described above. Chromatography and crystallization

from hot heptane produced the target diselenide 14c as an orange

³J_HH¼ 7.0 Hz, J_PH¼ 16.3 Hz, 6 H, CHMe₂), 1.46 (dd, J_HH¼ 6.9 Hz,

³J_PH¼ 17.4 Hz, 6 H, CHMe₂), 3.05e3.16 (m, 2 H, CHMe₂), 3.28 (br s,

2

2 H, fc), 3.40 (d, J_PH¼ 10.7 Hz, 2 H, CH₂PPh₂), 4.06 (vt, J⁰¼ 1.9 Hz,

2 H, fc), 4.30 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 4.42 (vq, J⁰¼ 1.8 Hz, 2 H, fc),

crystalline solid. Yield: 40 mg (58%).

7.46e7.56 (m, 6 H, Ph), 7.94e8.02 (m, 4 H, Ph). ³¹P{¹H} NMR

3

¹H NMR (399.95 MHz, CDCl₃):

d

1.36 (d, J_PH¼ 15.5 Hz, 18 H,

(161.90 MHz, CDCl₃): d 29.6 (s, PPh₂), 35.7 (s, PiPr₂).

2

CMe₃), 4.08 (vt, J⁰¼ 1.9 Hz, 2 H, fc), 4.13 (d, J_PH¼ 11.6 Hz, 2 H,

CH₂P(Se)Ph₂), 4.16 (d of vt, J ¼ 1.1, 1.9 Hz, 2 H, fc), 4.42 (vq,

J⁰¼ 1.7 Hz, 2 H, fc), 4.45 (vq, J⁰¼ 1.7 Hz, 2 H, fc), 7.40e7.48 (m, 6 H,

Ph), 7.83e7.89 (m, 4 H, Ph). ¹³C{¹H} NMR (100.58 MHz, CDCl₃):

Compound 16b. ¹H NMR (399.95 MHz, CD₂Cl₂):

d 1.27 (dd,

3

³J_HH¼ 7.2 Hz, J_PH¼ 14.0 Hz, 6 H, CHMe₂), 1.42 (dd, J_HH¼ 7.2 Hz,

³J_PH¼ 15.7 Hz, 6 H, CHMe₂), 2.61e2.74 (m, 2 H, CHMe₂), 3.98 (dd,

4

²J_PH¼ 8.9 Hz, J_PH¼ 2.1 Hz, 2 H, CH₂PPh₂), 4.24 (br s, 2 H, fc), 4.27

2

1

d

28.77 (d, J_PC¼ 2 Hz, 6 C, CMe₃), 36.31 (d, J_PC¼ 44 Hz, 1 C,

(vt, J⁰¼ 1.8 Hz, 2 H, fc), 4.34 (d of vt, J ¼ 0.7, 1.7 Hz, 2 H, fc), 4.73 (vq,

J⁰¼ 1.6 Hz, 2 H, fc), 7.33e7.48 (m, 6 H, Ph), 7.59e7.65 (m, 4 H, Ph). ³¹P

CH₂P(Se)Ph₂), 38.17 (d, ¹J_PC¼ 36 Hz, 2 C, CMe₃), 70.03 (s, 2 C, CH of

fc), 70.71 (d, J_PC¼ 8 Hz, 2 C, CH of fc), 73.33 (d, J_PC¼ 2 Hz, 2 C, CH of

{¹H} NMR (161.90 MHz, CD₂Cl₂):

d

16.5 (d, ²J_PP¼ 541 Hz, PPh₂), 30.0

1

fc), 74.77 (d, J_PC¼ 9 Hz, 2 C, CH of fc), 75.00 (d, J_PC¼ 63 Hz, 1 C,

(d, ²J_PP¼ 541 Hz, PiPr₂).

C

_ipsoeP of fc), 79.90 (s, 1 C, C_ipsoeCH₂of fc), 128.40 (d, J_PC¼ 12 Hz,

4 C, CH of Ph), 130.95 (d, ¹J_PC¼ 71 Hz, 2 C, C_ipsoeP of Ph), 131.43 (d,

J_PC¼ 3 Hz, 2 C, CH of Ph), 132.24 (d, J_PC¼ 10 Hz, 4 C, CH of Ph). ³¹P

4.27. Synthesis of palladium complexes from diphosphine 2c

{¹H} NMR (161.90 MHz, CDCl₃):

d

33.8 (s with ⁷⁷Se satellites,

The same procedure using diphosphine 2c (26 mg, 50 mol) led

m

¹J_SeP¼ 728 Hz, PPh₂), 75.3 (s with ⁷⁷Se satellites, J_SeP¼ 699 Hz,

PtBu₂). IR (Nujol): n_max1435 s, 1398 m, 1311 w, 1242 w, 1181 m,

1160 m, 1112 w, 1095 s, 1066 w, 1043 w, 1029 m, 996 w, 972 w, 950

w, 931 m, 888 w, 869 w, 863 w, 849 w, 839 m, 828 m, 810 m, 758 m,

745 m, 697 s, 687 m, 631 w, 618 m, 603 m, 587 w, 567 m, 542 w,

to a mixture of the analogous products 15c and 16c. The mixture

was recrystallized as described above. ESIe MS: m/z 529

([MePdCl₂þH]^e). Anal. Calc. for C₃₁H₃₈Cl₂FeP₂Pd$0.6CH₂Cl₂

(756.71): C 50.16, H 5.22%. Found: C 50.14, H 5.07%.

1

Compound 15c. ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d 28.6 (d,

527 s, 512 m, 494 m, 480 s, 474 m, 450 w, 436 w, 423 w cm^ꢀ1

.

²J_PP¼ 7 Hz, PPh₂), 50.6 (d, J_PP¼ 7 Hz, PtBu₂). Compound 16c: ³¹P

2

ESI þ MS: m/z 711 ([MþNa]^þ). Anal. Calc. for C₃₁H₃₈FeP₂Se₂

{¹H} NMR (161.90 MHz, CDCl₃):

d

16.9 (d, ²J_PP¼ 538 Hz, PPh₂), 51.6

2

(686.35): C 54.25, H 5.58%. Found: C 54.21, H 5.53%.

(d, J_PP¼ 538 Hz, PtBu₂). The ¹H NMR spectra could not be unam-

biguously interpreted due to the poor solubility of the compounds

and to extensive signal broadening.

4.25. Synthesis of palladium complexes from diphosphine 2a

A solution of diphosphine 2a (29 mg, 50

(1.5 mL) was added to reaction vial containing solid

[PdCl₂(MeCN)₂] (13 mg, 50 mol). The resulting mixture was stirred

m

mol) in chloroform

4.28. X-ray crystallography

a

m

Full-set diffraction data ( h

k

l, q

_maxz 26.0 or 27.5^ꢁ,

for 10 min to dissolve the solid educt and then heated to 55 ^ꢁC

under argon for 12 h. Addition of methyl tert-butyl ether (ca. 8 mL)

and crystallization by liquid-phase diffusion over several days

afforded the product, which is a mixture of monopalladium chelate

complex 15a and of the dimeric complex 16a. Combined yield:

19.5 mg. Single crystals of 15a were obtained by crystallization from

completeness ꢃ 99.6%) were collected with a Nonius KappaCCD

diffractometer equipped with a Bruker ApexII detector and a

Cryostream Cooler (Oxford Cryosystems) or, alternatively, with a

Bruker D8 Venture Kappa Duo diffractometer equipped with a

PHOTON 100 detector, a I

mS 3.0 microfocus source (only for 14a,

14c, 16b and 16c) at 120(2) or 150(2) K. Mo K

a

radiation

dichloromethane-diethyl

ether.

Anal.

Calc.

for

(

l

¼ 0.71073 Å) was used throughout. The data were corrected for

C

₃₅H₄₂Cl₂FeP₂Pd$0.15CH₂Cl₂(770.56): C 54.79, H 5.53%. Found: C

absorption using routines incorporated in the diffractometer

software.

54.68, H 5.40%. ESI þ MS: m/z 685 ([MeCleHCl]^þ), 721 ([MeCl]^þ).

Compound 15a. ¹H NMR (399.95 MHz, CDCl₃):

d

1.12e1.56 (m,

The structures was solved by direct methods using SHELXS-97

[42] or SHELXT-2014 [43] and reﬁned by full-matrix least-squares

routine based on F²(SHELXL-97 [42] or SHELXL-2014 [44]). All non-

hydrogen atoms were reﬁned with anisotropic displacement pa-

rameters. The OH hydrogens in the structure of 9b were identiﬁed

on the difference density maps and reﬁned as riding atoms with

U_iso(H) assigned to 1.5U_eq(O) of its bonding oxygen atom. The

hydrogen atoms in the CH_ngroups were all placed in their theo-

retical positions and similarly reﬁned with U_iso(H) ¼ 1.5U_eq(C)

(methyl groups) or with 1.2U_eq(C) (all other hydrogen atoms).

Relevant crystallographic data and reﬁnement parameters are

presented in the Supporting Information (Table S1).

Geometric calculations were performed using a recent version

of the PLATON program [45], which was also used to prepare the

structural drawings. All geometric parameters of atoms in reﬁned

positions are indicated with their estimated standard deviations

(ESDs) rounded to one decimal place. The parameters involving

10 H, Cy), 1.70e1.92 (m, 6 H, Cy), 2.14e2.22 (m, 2 H, Cy), 2.38e2.45

(m, 2 H, Cy), 2.83e2.94 (m, 2 H, Cy), 3.23 (br s, 2 H, fc), 3.38 (d,

2

J_PH¼ 10.7 Hz, 2 H, CH₂PPh₂), 4.05 (vt, J⁰¼ 1.9 Hz, 2 H, fc), 4.27 (vq,

J⁰¼ 1.7 Hz, 2 H, fc), 4.40 (vq, J⁰¼ 1.6 Hz, 2 H, fc), 7.46e7.54 (m, 6 H,

Ph), 7.94e8.02 (m, 4 H, Ph). ³¹P{¹H} NMR (161.90 MHz, CDCl₃):

d

27.7 (s, PPh₂), 29.5 (s, PCy₂).

Compound 16a. ¹H NMR (399.95 MHz, CD₂Cl₂):

d 1.10e1.80 (m,

16 H, Cy), 2.04e2.18 (m, 4 H, Cy), 2.44e2.58 (m, 2 H, Cy), 4.07 (br s,

2

2 H, fc), 4.10 (vt, J⁰¼ 1.8 Hz, 2 H, fc), 4.12 (d, J_PH¼ 7.0 Hz, 2 H,

CH₂PPh₂), 4.36 (vt, J⁰¼ 1.6 Hz, 2 H, fc), 4.61 (br s, 2 H, fc), 7.35e7.50

(m, 6 H, Ph), 7.65e7.72 (m, 4 H, Ph). ³¹P{¹H} NMR (161.90 MHz,

CD₂Cl₂):

d

16.6 (d, ²J_PP¼ 528 Hz, PPh₂), 22.9 (d, ²J_PP¼ 528 Hz, PCy₂).

4.26. Synthesis of palladium complexes from diphosphine 2b

Using diphosphine 2b (25 mg, 50 mol), the procedure

m

ꢀ

P. Vosahlo et al. / Journal of Organometallic Chemistry 860 (2018) 14e29

29

Soc., Dalton Trans. (1996) 4633;

d) I.R. Butler, W.R. Cullen, T.J. Kim, S.J. Rettig, J. Trotter, Organometallics 4

(1985) 972;

atoms in constrained positions (hydrogen atoms) are given without

ESDs.

e) I.R. Butler, S.J. Coles, M.B. Hursthouse, D.J. Roberts, N. Fujimoto, Inorg. Chem.

Commun. 6 (2003) 760;

Acknowledgements

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Appendix A. Supplementary data

Supplementary data related to this article can be found at

https://doi.org/10.1016/j.jorganchem.2018.01.009.

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Article Doi

Comparing the asymmetric dppf-type ligands with their semi-homologous counterparts

DOI: 10.1016/j.jorganchem.2018.01.009

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