Coordination of Base-stabilized Diborenes to Transition Metals

(1)

Coordination of Base-stabilized Diborenes to Transition Metals

δ¹¹B = 18, yellow solid,

100% conversion (NMR)

B1–B2 = 164.8(2), Ag-B1 = 231.6(4), Ag–B2 = 236.3(3) pm δ ¹¹B = 26

Angew. Chem. Int. Ed.

2012, 51, 9931.

B1–B2 = 159.3(5) pm

B B H

NHC NHC

H

isoelectronic

_C _C H

H H

H

metal-to-ligandππππ-backbond

ligand-to-metalσσσσ-bond

ππππ-backbondinginto

B=B_ππππ*orbital

weakening of the B=B bond upon side-on coordination

B-B bond lengthens by 6 pm

C=C

_π_*

C=C

_π

(2)

Diborene Coordination to Platinum:

Implications for the DCD-Model

side-on coordination of E-E or E=E:

- σσσσ-donation from bonding MO

- ππππ -backdonation into antibonding MO weakening (ox. add.) of E-E bond activation according to DCD model

side-on coordination of B=B:

- σσσσ -donation from bonding MO - ππππ -backdonation into bonding MO

strengthening of B-B bond

(3)

Diborene Coordination to Platinum:

Implications for the DCD-Model

δ¹¹B = 132, purple solid

B1–B2 = 152.1(2),

Pt–B1 = Pt–B2 = 207.1(6) pm

ππππ-backbond into B=B bondingMO strengtheningof B=B-bond;

MBO B=B: free = 0.66, bound = 1.41 DFT @ OLYP/TZP

Coordination of Base-stabilized Diborenes to Transition Metals