Platinum Complexes of a Borane‐Appended Analogue of 1,1′‐Bis(diphenylphosphino)ferrocene: Flexible Borane Coordination Modes and in situ Vinylborane Formation

Abstract

A bis(phosphine)borane ambiphilic ligand, [Fe(η(5) -C5 H4 PPh2 )(η(5) -C5 H4 PtBu{C6 H4 (BPh2 )-ortho})] (FcPPB), in which the borane occupies a terminal position, was prepared. Reaction of FcPPB with tris(norbornene)platinum(0) provided [Pt(FcPPB)] (1) in which the arylborane is η(3) BCC-coordinated. Subsequent reaction with CO and CNXyl (Xyl=2,6-dimethylphenyl) afforded [PtL(FcPPB)] {L=CO (2) and CNXyl (3)} featuring η(2) BC- and η(1) B-arylborane coordination modes, respectively. Reaction of 1 or 2 with H2 yielded [PtH(μ-H)(FcPPB)] in which the borane is bound to a hydride ligand on platinum. Addition of PhC2 H to [Pt(FcPPB)] afforded [Pt(C2 Ph)(μ-H)(FcPPB)] (5), which rapidly converted to [Pt(FcPPB')] (6; FcPPB'=[Fe(η(5) -C5 H4 PPh2 )(η(5) -C5 H4 PtBu{C6 H4 (BPh-CPh=CHPh-Z)-ortho}]) in which the newly formed vinylborane is η(3) BCC-coordinated. Unlike arylborane complex 1, vinylborane complex 6 does not react with CO, CNXyl, H2 or HC2 Ph at room temperature.

Synthesis and Platinum Complexes of an Alane‐Appended 1,1′‐Bis(phosphino)ferrocene Ligand

“…FcPPAl is chiral at phosphorus, and was used as a racemic mixture. In the solid state, P(1) is engaged in adduct formation with the alane (Figure 2; P(1)-Al = 2.554(2) ), whereas recently reported FcPPB features a P(2)-B interaction; [18] presumably a P(1)-B interaction is disfavored by the B-phenyl substituents in FcPPB. In the 31 P NMR spectrum of FcPPAl, a 31 P-31 P coupling of 31 Hz ( Figure 2) is indicative of through-space coupling arising from a nonbonding interaction between the lone pair on P(2) and the bonding pair between P(1) and Al; [20] the P(1)-P(2) distance in FcPPAl is 3.601(2) .…”

“…[17] However, the Achilles heel of the TXPB ligand is the central thioether donor, which readily dissociates from the metal center. In response, a much more electron-donating borane-containing ambiphilic ligand, [Fe(h 5 from FeCp 2 and C 6 H 4 Br 2 -o) [18] and quenching with Me 2 AlCl (Scheme 1). FcPPAl is chiral at phosphorus, and was used as a racemic mixture.…”

Oxidative‐Insertion Reactivity Across a Geometrically Constrained Metal→Borane Interaction

“…[2,[19][20][21] Structurally authenticated complexes containing ad irect reverse-dative s-interaction between at ransition metal and ab orane were unknown prior to Hillss eminal report of the first metalloboratrane. [2,[19][20][21] However, despite the reactive nature of the M!BR 3 linkage,substrate activation reactions occurring across this bond have been limited almost exclusively to formal oxidative addition/ heterolytic bond cleavage, [4][5][6][7][8][9][10][11][12][13] with H 2 oxidative addition and hydride shuttling receiving much of the attention. [2,[19][20][21] However, despite the reactive nature of the M!BR 3 linkage,substrate activation reactions occurring across this bond have been limited almost exclusively to formal oxidative addition/ heterolytic bond cleavage, [4][5][6][7][8][9][10][11][12][13] with H 2 oxidative addition and hydride shuttling receiving much of the attention.…”

Nickel and Palladium Complexes of Ferrocene-Backbone Bisphosphine-Borane and Trisphosphine Ligands

“…The B−C ipso bonds in 2 and [Pt(FcPPB)] are also somewhat contracted, with B−C ipso distances of 1.563(6) and 1.551(5) Å, respectively (the remaining B−C aryl distances lie between 1.596(6) and 1.611(4) Å). 9 For comparison, the B−C α bond distances in the vinylborane and borataalkene complexes [Ni(PPh 3 [Cp 2 Ta(CO){η 2 BC-H 2 CB(C 6 F 5 ) 2 }], 50 and [Cp 2 Ta(CN t Bu)-{η 2 BC-H 2 CB(C 6 F 5 ) 2 }] 51 are 1.483(4), 1.517(6)/1.519 (7), 1.508(8), and 1.525 (7) Å, respectively. The coordinated Bphenyl ring in 1 also shows considerable bond alternation with C(33)−C(34), C(34)−C (35), C(35)−C(36), C(36)−C(37), C(37)−C (38), and C(33)−C(38) distances of 1.443(5), 1.423(6), 1.365(7), 1.412 (7), 1.354(6), and 1.449(6) Å, respectively.…”