Reactivity of metal boryl complex
Literature Seminar #2
M1 Yuta Kasamoto

Contents
1. Introduction: Nucleophilic boryl
2. Contents: Factors of reactivity of metal boryl complex
2-1. Stabilization of neighboring atoms
2-2. Electronegativity of metal
2-3. d electrons of metal
3. Summary

Reaction of boron
Suzuki-Miyaura cross coupling

Hydroborylation
H

BHMe2
RB

R1 BY2＋R2

Pd, Ligand, BaseX

R

R1 R2

R1, R2= alkenyl, alkyl, aryl

Reaction of boron
Bvia

electrophilicNu

Petasis reaction

Matteson homologation

OHOH
R BY2LiCHCl2 ; R1-MgBr

R
BY2R1R1O

R2B

OH

R4HNOH
R3R2
R4R1N

R3

Reaction of boron
Suzuki-Miyaura cross coupling

Hydroborylation
R

BHMe2HBR1 BY2 ＋ R2

R

X

Pd, Ligand, Base

R1 R2

R1, R2= alkenyl, alkyl, aryl

Reaction of boron
Bviaelectrophilic

Nu

Petasis reaction

Matteson homologation
R BY2

LiCHCl2 ; R1-MgBr

R
R1OH
BY2O

HOH
N
B
R3R2OH R4R1Few observation of nucleophilic boryl

OH
R2R4N

R1R3

Early attempts of boryl anion
Attempt ①

rearrange

C. A. Kraus, et al. J. Am. Chem. Soc. 1952, 74, 3398.
K. Swaminathan, et al. J. Chem. Soc.,Dalton Trans. 1976, 2297.

Attempt ②
N. D.

D. P. Maier, et al. J. Am. Chem. Soc. 1967, 89, 5153–5157.

Early attempts of boryl anion
Attempt ③

L. Weber, et al. J. Chem. Soc. Dalton Trans. 2001, 3459.

Boryl lithium could not be isolated and structurally analyzed.

Boryl lithium
First example of isolated boryl anion

iPriPrNiPr

BLiN••••

X-ray crystallography
Bond length and angle
NMR
Reaction with several electrophiles

iPrM. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.

Boryl lithium
Boryl lithium can react with various electrophiles.

M. Yamashita, K. Nozaki, et al. J. Am. Chem. Soc. 2008, 130, 16069.

Boryl copper complex
Addition of boryl copper complex to alkenes and alkynes

Nucleophilicity of boron center in copper boryl complex wassuggested.
N. Miyaura, et al. Chem. Lett. 2000, 982.
N. Miyaura, et al. J. Organomet. Chem. 2001, 625, 47.

Boryl copper complex
First example of isolated boryl anion

iPrN

iPrO

Cu BN
iPriPrO••••

X-ray crystallography
Bond length and angle
NMRReaction with CO2 and aldehydes
as electrophiles

J. P. Sadighi, et al. J. Am. Chem. Soc. 2005, 127, 17196.
J. P. Sadighi, et al. J. Am. Chem. Soc. 2006, 128, 11036.

Boryl copper complex
Borylation of aldehydes

J. P. Sadighi, et al. J. Am. Chem. Soc. 2006, 128, 11036.

Boryl copper complex
Boryl copper complex can react with various electrophiles.
Borylation of ketone

H. Ito, et al. Angew. Chem. Int. Ed. 2017, 56, 6646.

Borylation of dialkyl ketimine

H. Ito, et al. ACS Catal. 2021, 11, 11, 6733.

Nucleophilic boryl
Application to nucleophilic boryl
Borylation of electrophiles
Boryl lithium

Boryl copper complex

J. P. Sadighi, et al. J. Am. Chem. Soc. 2006, 128, 11036.

K. Nozaki, et al. J. Am. Chem. Soc. 2008, 130, 16069.

H. Ito, et al. Angew. Chem. Int. Ed. 2017. 56, 6646.

Other metal boryl complex
Electrophilic boryl was also detected.

M. Srebnlik, et al. Organometallics. 2001, 20, 18, 3962.

Z. Lin, et al. Organometallics. 2012, 31, 3410.

Transition metal boryl complex
Difference of reactivity of transition metal boryl complex

Nucleophilicity

Electrophilicity

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Transition metal boryl complex
Reactiyity of metal boryl complex is affected by 3 factors below.
YLnM

BY

② Electronegativity① Neighboring atoms③ d electrons

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Contents
1. Introduction: Nucleophilic boryl
2. Contents: Factors of reactivity of metal boryl complex
2-1. Stabilization of neighboring atoms
2-2. Electronegativity of metal
2-3. d electrons of metal

YLnMBY

3. Summary② Electronegativity③ d electrons① Neighboring atoms

ModelNeighboring atom is O

Neighboring atom is C(NHC)Cu-Bpin(NHC)Cu-BPh2

NO

NO

N

Cu B
N

Isolated as(Icy)Cu-Bpin (J. P. Sadighi, 2005)

Cu B

Not isolated

Many application
to borylation of electrophiles

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

CCDFT calculation(NHC)Cu-Bpin(NHC)Cu-BPh2○ Nucleophilicity○ Nucleophilicity❌ Electrophilicity○ Electrophilicity

Neighboring atoms affect electrophilicity of boryl.
Z. Lin, et al. ACS Catal. 2021, 11, 5061.

FMO calculation
NHC

B center

LUMO is different.

HOMO is almost same.

Neighboring atoms affect electrophilicity of boryl.
Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Effects of neighboring atoms
Push π electronStabilization(Lose electrophilicity)Y
BY
Example of stabilization of boryl lithium

LiB

CH3CH3LiB

NH2NH2Boron pz occ
ー0.30(occ= occupancy of boron pz orbital)

LiB

OHOH

0.19

R. Schleyer, Inorg. Chem. 1995, 34 , 607.

LiB

FF

0.18

Stable boryl lithium
Early attempt to generate boryl anion

rearrange

C. A. Kraus, et al. J. Am. Chem. Soc. 1952, 74, 3398.
K. Swaminathan, et al. J. Chem. Soc.,Dalton Trans. 1976, 2297.
First example of isolated boryl lithium

Isolated
M. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.

Stable boryl lithium
Boryl lithium can react with various electrophiles.

M. Yamashita, K. Nozaki, et al. J. Am. Chem. Soc. 2008, 130, 16069.

Short summary
YLnM

BY

① Neighboring atoms
Y= N, O, FPush π electronYB
Y

Stabilized(Lose electrophilicity)

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Contents
1. Introduction: Nucleophilic boryl
2. Contents: Factors of reactivity of metal boryl complex
2-1. Stabilization of neighboring atoms
2-2. Electronegativity of metal
2-3. d electrons of metal
3. SummaryYLnMBY② Electronegativity③ d electrons① Neighboring atoms

ModelElectronegativity (Pauling)Cu: 1.90 B: 2.04 Au: 2.54Electropositive metal (Cu)Electronegative metal (Au)

(NHC)Cu-Bpin(NHC)Au-Bpin

ONCu B
NONAu B

ONO

Isolated as
Isolated as(Icy)Cu-Bpin (J. P. Sadighi, 2005) (IPr)Au-Bpin (S. P. Nolan, 2019)
Many application
to borylation of electrophiles

Low reactivity and high stability

DFT calculation(NHC)Cu-Bpin(NHC)Au-Bpin○ Nucleophilicity❌ Nucleophilicity❌ Electrophilicity❌ Electrophilicity

Transition metal affect nucleophilicity of boryl.
Z. Lin, et al. ACS Catal. 2021, 11, 5061.

FMO calculation

LUMO is almost same.

Energy of HOMO is lower.

Transition metal affect nucleophilicity of boryl.

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Electronegativity of metal
The charge population calculated by NBO analysis
B of electron population→ lower

PIO analysis
Due to Electronegativity
Cu: 1.90 B: 2.04 Au: 2.54(Pauling)
Electronegative metal loses
nucleophilicity of metal boryl
complex

B of Pop (Occupation number of electron)→ lowerZ. Lin, et al. ACS Catal. 2021, 11, 5061.

Au(NHC)Bpin complex
Reaction with electrophiles
ON
Cu B

⭕

ONElectrophiles
OEWGON❌

R

EWG
Bpin

Au B
NO

Lose nucleophilicity

S. P. Nolan, et al. Chem. Commun. 2019, 55, 6799.

OHRBpinShort summary
YLnM

BY

② Electronegativity
M<B (M: electropositive)→B gets nucleophilicity
M>B (M: electronegative)→B loses nucleophilicity
Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Contents
1. Introduction: Nucleophilic boryl
2. Contents: Factors of reactivity of metal boryl complex
2-1. Stabilization of neighboring atoms
2-2. Electronegativity of metalY

2-3. d electrons of metalLnMBY

3. Summary② Electronegativity③ d electrons① Neighboring atoms

ModelElectronegativity (Pauling)
B: 2.04 Rh: 2.28 Au: 2.54
(NHC)Au-Bpin(PH3)3Rh-Bpin

ON
Au B
NO

H 3P
O
H3P Rh BO
H 3P

Isolated as(IPr)Au-Bpin (S. P. Nolan, 2019)

Use as catalyze
Rh-Bpin (W. Zhao 2020)

Low reactivity and high stability

B exhibits electrophilicity

DFT calculation(NHC)Au-Bpin(PH3)3Rh-Bpin❌ Nucleophilicity❌ Nucleophilicity❌ Electrophilicity○ Electrophilicity

Transition metal affect electrophilicity of boryl.

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

FMO calculation
LUMO is almost same.
Au-B σ-bondRh dz2 orbital

HOMO is different.

Have nucleophilicity of d orbital in transition metal
depending on transition metals

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

8 d electrons metal complex
Pt(Ⅱ), Pd(Ⅱ), Ir(Ⅰ) , Rh(Ⅰ)(Tetracoordination complex of 8 d electrons metal)→Form square planar complex

https://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s27-05-crystal-field-theory.html

8 d electrons metal complex

LUMOHOMO

dz2 orbital of square planar complex (Pt(Ⅱ), Ir(Ⅰ)) has nucleophilicity
showed by natural atomic orbital analysis.
J. V. Burda, et al. Inorg. Chem. 2019, 58, 3616.

Nucleophilicity of transition metal(PH3)3Rh-Bpin
Rh dz2 orbital

Nucleophilicityof metal

Get electrophilicity
Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Rh boryl complex
Via Rh (Ⅰ) boryl complex (8 d electrons)

W. Zhao, et al. J. Am. Chem. Soc. 2020, 142, 42, 18118.

Rh boryl complex

Electrophilic boryl

W. Zhao, et al. J. Am. Chem. Soc. 2020, 142, 42, 18118.

Pt boryl complex
Via Pt (Ⅱ) boryl complex (8 d electrons)

M. Srebnlik, et al. Organometallics. 2001, 20, 18, 3962.

Z. Lin, et al. Organometallics. 2012, 31, 3410.

Short summary
YLnM

B
Y

③ d electrons

8 d electrons metal (square planar complex)

Z. Lin, et al. ACS Catal. 2021, 11, 5061.

Contents
1. Introduction: Nucleophilic boryl
2. Contents: Factors of reactivity of metal boryl complex
2-1. Stabilization of neighboring atoms
2-2. Electronegativity of metal
2-3. d electrons of metal
3. Summary

SummaryReavtivity of metal boryl complex① Neighboring atoms
Y= N, O, FY
LnM

Push π electronBYYBY② Electronegativity
M<B (M: electropositive)→B gets nucleophilicity
M>B (M: electronegative)→B loses nucleophilicity③ d electrons

Stabilized(Lose electrophilicity)

8 d electrons metal (square planar complex)

Appendix

Nucleophilic boryl
Example of nucleophilic boryl
Boryl lithium (K. Nozaki, 2006)

Boryl magnesium (K. Nozaki, 2007)

Ar N B N Ar

Ar N B N Ar

Li
Ar =Br

iPr

THF

iPr
iPr

Ar =

Boryl copper (J. P. Sadighi, 2005)
O

iPr

Carben stabulized π-boryl anion(H. Braunschweig, 2010)PhPh

Icy Cu B
O

PhN

Ph
MesN

B

ICy=N

Mg THF

MesN

Difficulty of boryl anion
Difficulty ①: 6e- structure

Difficulty ②: Low electronegativity→Lower stability for boryl anions
B: 2.04 C: 2.55 N: 3.04 O: 3.44 F: 3.98
M. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.

Difficulty of boryl anion
Difficulty ③: Synthesis (Can’t use base)Satisfy the octet rule

Reduction of halogen borane

M. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.

Design for boryl lithium
Design ①
Boryl lithium has a singlet grand state.

H

H B LiHSingletH
20.0 kcal/mol

B Li

TripletDesign ②
Boryl lithium is more stabilized by N than O, F.

NBO charges Y
NBO charges B
Boron pz occ

-0.99
0.19
ー-1.20
0.36
0.30

-1.00
0.50
0.19

R. Schleyer, Inorg. Chem. 1995, 34, 607.

-0.61
0.58
0.18

Design for boryl lithium
Stable carben

Stabilized

Ar N C N Ar

Ar N B N Ar
LiAr =iPr

iPr

Ar =iPr

SingletM. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.

iPr

Synthesis of boryl lithium

Reduction of halogen borane

M. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.

X-ray crystallography
Crystal structure of the boryl lithiumwith an included DME(1,2-dimethoxyethane) molecule.

∠ N1-B1-Li1 + ∠ N2-B1-Li1= 359.2°→ sp2 character of boron center of 3-DME

M. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.

X-ray crystallography

B-N length and N-B-N angle•

3-DME is closer to 6 than 4.

•

Structural change from 4 to 3-DME is similar to that from 8 to 5.
→ Anionic character of boron center of 3-DME
Reference
23: N. Metzler-Nolte, New J. Chem. 1998, 22, 793.
34: R. Schmutzler, et al, Tetrahedron. 1999, 55, 14523.
M. Yamashita, K. Nozaki, et al. Science. 2006, 314, 5796.