TY - JOUR
T1 - Preparation, structure, and reactivity of dipalladium(I) complexes containing the carbanion 2-C 6F 4PPh 2
T2 - Coexistence of distinct, noninterconverting head-to-head [dipalladium(0/II)] and head-to-tail [dipalladium(I)] species
AU - Bhargava, Suresh K.
AU - Privér, Steven H.
AU - Willis, Anthony C.
AU - Bennett, Martin A.
PY - 2012/8/13
Y1 - 2012/8/13
N2 - Comproportionation of trans-[Pd(κ 2-2-C 6F 4PPh 2) 2] with [PdL 4] (L = PPh 3, AsPh 3) gives metal-metal-bonded dipalladium(I) complexes [Pd 2 I(μ-2-C 6F 4PPh 2) 2(L) 2] [L = PPh 3 (5), AsPh 3 (6)] in which the bridging ligands adopt a head-to-tail arrangement. The corresponding diplatinum(I) complex [Pt 2 I(μ-2-C 6F 4PPh 2) 2(PPh 3) 2] (9) is obtained similarly from [Pt(κ 2-2-C 6F 4PPh 2) 2] and [Pt(PPh 3) 3]. The separations between the metal atoms in the dipalladium(I) complexes [2.5740(3) Å (5), 2.5511(3) Å (6)] are slightly less than that in the diplatinum(I) complex 9 [2.61179(15) Å]. The axial triphenylarsine ligands of 6 are replaced by tert-butyl isocyanide to give the dipalladium(I) complex [Pd 2 I(μ-2-C 6F 4PPh 2) 2(CN tBu) 2] (7). However, treatment of trans-[Pd(κ 2-2-C 6F 4PPh 2) 2] with [Pd(CN tBu) 2], generated in situ from a mixture of tert-butyl isocyanide and [Pd(η 5-Cp) (η 3-allyl)], gives a formally mixed-valent palladium(0)- palladium(II) complex [Pd 2 0/II(μ-2-C 6F 4PPh 2) 2(CN tBu) 2] (8), in which the bridging ligands are arranged head-to-head. In contrast, comproportionation of [Pt(κ 2-2-C 6F 4PPh 2) 2] with [Pt 3(CN tBu) 6] gives the diplatinum(I) complex [Pt 2 I(μ-2-C 6F 4PPh 2) 2(CN tBu) 2] (10) analogous to 7; there was no evidence for the formation of a dinuclear mixed-valent species. Although complexes 7 and 8 are isomers, with similar Pd-Pd separations [2.5803(4) Å (7), 2.5580(2) Å (8)], they do not interconvert in solution. The diplatinum(I) complex 9 undergoes oxidative addition with iodine to give an A-frame cation, [Pt 2(μ-I)(μ-2-C 6F 4PPh 2) 2(PPh 3) 2] +, isolated as its PF 6 - salt (11). In contrast, the dipalladium(I) complex 5 eliminates one of the PPh 3 ligands when it undergoes oxidative addition with halogens and with methyl iodide, the products being A-frame dipalladium(II) complexes [Pd 2X(μ-Y)(μ- 2-C 6F 4PPh 2) 2(PPh 3)] [X = Y = I (12), Cl (13); X = Me, Y = I (14)]. The metal-metal distances in 11-14 [2.9478(5) Å (11), 2.8078(7) Å (12), 2.8241(3) Å (13), and 2.8013(5) Å (14)] are ca. 0.3 Å greater than in their dimetal(I) precursors, consistent with a weaker metal-metal interaction in the dimetal(II) complexes. Unexpectedly, reaction of 5 with iodobenzene gives a mononuclear palladium(II) complex, cis-[Pd(κ 2C,P-2-C 6F 4PPh 2)(κC-2-C 6F 4PPh 2)(PPh 3)] (15). This is suggested to be formed by a sequence of (a) oxidative addition of iodobenzene to 5 to give a σ-phenyl complex analogous to the σ-methyl complex 14, (b) a change in the binding mode of one of the 2-C 6F 4PPh 2 ligands from μ- to κ 2-, and (c) reductive elimination of tetraphenylphosphonium iodide and loss of Pd(0).
AB - Comproportionation of trans-[Pd(κ 2-2-C 6F 4PPh 2) 2] with [PdL 4] (L = PPh 3, AsPh 3) gives metal-metal-bonded dipalladium(I) complexes [Pd 2 I(μ-2-C 6F 4PPh 2) 2(L) 2] [L = PPh 3 (5), AsPh 3 (6)] in which the bridging ligands adopt a head-to-tail arrangement. The corresponding diplatinum(I) complex [Pt 2 I(μ-2-C 6F 4PPh 2) 2(PPh 3) 2] (9) is obtained similarly from [Pt(κ 2-2-C 6F 4PPh 2) 2] and [Pt(PPh 3) 3]. The separations between the metal atoms in the dipalladium(I) complexes [2.5740(3) Å (5), 2.5511(3) Å (6)] are slightly less than that in the diplatinum(I) complex 9 [2.61179(15) Å]. The axial triphenylarsine ligands of 6 are replaced by tert-butyl isocyanide to give the dipalladium(I) complex [Pd 2 I(μ-2-C 6F 4PPh 2) 2(CN tBu) 2] (7). However, treatment of trans-[Pd(κ 2-2-C 6F 4PPh 2) 2] with [Pd(CN tBu) 2], generated in situ from a mixture of tert-butyl isocyanide and [Pd(η 5-Cp) (η 3-allyl)], gives a formally mixed-valent palladium(0)- palladium(II) complex [Pd 2 0/II(μ-2-C 6F 4PPh 2) 2(CN tBu) 2] (8), in which the bridging ligands are arranged head-to-head. In contrast, comproportionation of [Pt(κ 2-2-C 6F 4PPh 2) 2] with [Pt 3(CN tBu) 6] gives the diplatinum(I) complex [Pt 2 I(μ-2-C 6F 4PPh 2) 2(CN tBu) 2] (10) analogous to 7; there was no evidence for the formation of a dinuclear mixed-valent species. Although complexes 7 and 8 are isomers, with similar Pd-Pd separations [2.5803(4) Å (7), 2.5580(2) Å (8)], they do not interconvert in solution. The diplatinum(I) complex 9 undergoes oxidative addition with iodine to give an A-frame cation, [Pt 2(μ-I)(μ-2-C 6F 4PPh 2) 2(PPh 3) 2] +, isolated as its PF 6 - salt (11). In contrast, the dipalladium(I) complex 5 eliminates one of the PPh 3 ligands when it undergoes oxidative addition with halogens and with methyl iodide, the products being A-frame dipalladium(II) complexes [Pd 2X(μ-Y)(μ- 2-C 6F 4PPh 2) 2(PPh 3)] [X = Y = I (12), Cl (13); X = Me, Y = I (14)]. The metal-metal distances in 11-14 [2.9478(5) Å (11), 2.8078(7) Å (12), 2.8241(3) Å (13), and 2.8013(5) Å (14)] are ca. 0.3 Å greater than in their dimetal(I) precursors, consistent with a weaker metal-metal interaction in the dimetal(II) complexes. Unexpectedly, reaction of 5 with iodobenzene gives a mononuclear palladium(II) complex, cis-[Pd(κ 2C,P-2-C 6F 4PPh 2)(κC-2-C 6F 4PPh 2)(PPh 3)] (15). This is suggested to be formed by a sequence of (a) oxidative addition of iodobenzene to 5 to give a σ-phenyl complex analogous to the σ-methyl complex 14, (b) a change in the binding mode of one of the 2-C 6F 4PPh 2 ligands from μ- to κ 2-, and (c) reductive elimination of tetraphenylphosphonium iodide and loss of Pd(0).
UR - http://www.scopus.com/inward/record.url?scp=84864984643&partnerID=8YFLogxK
U2 - 10.1021/om300525p
DO - 10.1021/om300525p
M3 - Article
SN - 0276-7333
VL - 31
SP - 5561
EP - 5572
JO - Organometallics
JF - Organometallics
IS - 15
ER -