Reactivity of Organoplatinum Complexes with C6H4O2B-BO2C6H4: Syntheses of a Platinum Diboryl Complex with, and without, Metathesis of Boron-Boron and Metal-Carbon Bonds

Metal-Catalyzed Reactions of Organoboronic Acids and Esters

“…The reaction between Pt(PPh 3 ) 4 or Pt(C 2 H 4 )(PPh 3 ) 2 and B 2 pin 2 or B 2 cat 2 provides a single crystal of 1 consisting of a distorted square-planar coordination geometry for the Pt atom containing two cis-boryl and phosphine ligands, which allows insertion of alkenes and alkynes into the Pt-B bond (Scheme 1). [20][21][22] This process has been used for catalyzed additions of B-B, B-Si, and B-Sn compounds to alkenes and alkynes with Pd 0 , Pt 0 , or Rh I complexes. 8,16,17 Reaction between rhodium(I) or iridium(I) complexes ([M]-X, X ¼ halogen, OAc, and OR) with HBcat, HBpin, or B 2 pin 2 yields species effective for catalyzed hydroboration of alkenes and alkynes 4, diboration and dehydrogenative coupling of alkenes 5 and 6 and C-H borylation of alkanes, arenes, and alkenes 7 (Scheme 2).…”

“…[20][21][22]38 The proposed catalytic cycle 8,20-22 involves oxidative addition, insertion and reductive elimination processes. The reaction is accelerated significantly with an unsaturated platinum(0) complex having a donating phosphine ligand and is slowed down in the presence of PPh 3 added to Pt(PPh 3 ) 4 , thus suggesting a rate-determining role of both oxidative addition and phosphine dissociation (34 to 35).…”

(μ2-Pinacolato-O,O')-bis(pinacolato-O,O')diboron

“…The compound B2pin2 is of interest with regard to the recently developed metalcatalysed diboration of alkynes (Ishiyama, Matsuda, Miyaura & Suzuki, 1993;Iverson & Smith, 1995Ishiyama et al, 1996;Lesley et al, 1996) and alkenes (Baker, Nguyen, Marder & Westcott, 1995) and the palladium-catalysed synthesis of (aryl)B(pin) compounds (Ishiyama, Murata & Miyaura, 1995). It appears that B2pin3 is also formed in reactions of pinacol with BH3.thf or BC13 (Herberich & Fischer, 1996).…”

The Product of Catalysed Diboration of Bis(4-methoxyphenyl)ethyne by Bis(pinacolato-O,O')diboron

“…We and others have recently reported the catalysed addition of B--B bonds to alkenes (Baker, Nguyen, Marder & Westcott, 1995) and alkynes (Ishiyama, Matsuda, Miyaura & Suzuki, 1993;Iverson & Smith, 1995;Lesley et al, 1996), and have prepared and structurally characterized several platinum(II)-bis(phosphine)-bis(boryl) complexes formed by oxidative addition of the B--B bonds to bisphosphine Pt(0) centres. Initial studies (Ishiyama et al, 1993) of the addition of bis-(pinacolato-O,O')diboron, B2pin2, to alkynes suggested that this results in cis-alkene-1,2-bis(boronate esters) on the basis of NMR measurements, and we have confirmed this stereochemistry by X-ray crystallography for the addition of bis(benzene-l,2-diolato)diboron [or bis-(catecholato-O,O')diboron, B2cat2] to internal and terminal alkynes as well as to 1,3-diynes (Lesley et al, 1996).…”

“…The addition of B--B bonds to alkynes is catalyzed by platinum bis(phosphine) complexes and leads to cis-alkene-l,2-bis(boronate esters) (Ishiyama, Matsuda, Miyaura & Suzuki, 1993;Iverson & Smith, 1995;Lesley et al, 1996;Ishiyama et al, 1996). We have reported previously the structure of one product of addition of bis(pinacolato-O,O')diboron, B2pin2, to a symmetrical alkyne (Clegg, Scott, Lesley, Marder & Norman, 1996) and of representative products of addition of bis-(catecholato-O, O')diboron, B2cat2, to an internal alkyne, a terminal alkyne, and a 1,3-diyne (Lesley et al, 1996).…”