Cyclohexyneplatinum(0) Complexes Containing Di-t-butylphenylphosphine, t-butyldiphenylphosphine or Trimethylphosphine

Abstract

Cyclohexyneplatinum (0) complexes Pt(C6H8)L2 [L = PBut2Ph(4), PbutPh2(5)] analogous to the known complex (3) (L=PPh3) have been prepared by reaction of the two-coordinate complexes PtL2 with 1,2-dibromocyclohexene and 1% sodium amalgam. The corresponding tricyclohexylphosphine complex is formed by a similar reaction but it could not be isolated in a pure state. Attempts to prepare analogues of (4) and (5) containing cycloheptyne or cyclooctyne were unsuccessful, possibly because the bulky t-butyl groups of the tertiary phosphines hinder coordination of the larger rings. Bulky tertiary phosphines do not displace PPh3 from (3) but trimethylphosphine reacts with (3) to give successively Pt(C6H8)(PMe3)2(PPh3) (10) and Pt(C6H8)(PMe3)2 (11), as shown by 31P{1H) n.m.r. spectroscopy. The tertiary phosphines in these complexes equilibrate rapidly at room temperature in benzene and only (10) can be isolated as a solid from the reaction. Complexes (4) and (5) react with HCl (1 molar proportion) to give n1-cyclohexen-l-yl complexes trans- PtCl (C6H9)L2 [L= PBut2Ph(6), PButPh2 (7)]. In the absence of air, (4) reacts with methanol at 65°C to give the hydrido complex trans- PtH (C6H9)(PBut2Ph)2 (8). In the presence of oxygen from the air, however, the main product is the dioxygen complex Pt(O2)(Pbut2Ph)2 (9). This represents an unusual example of complete displacement of cyclohexyne from a platinum(0) complex by a π-acceptor ligand.

Synthesis and Reactions of Nickel(0) η2-Cyclohexyne Complexes and X-ray Crystal Structure of Ni(η2-C6H8)((C6H11)2PCH2CH2P(C6H11)2)

“…80 Hz. Similar patterns have been observed in the 13 C NMR spectra of benzyne nickel(0) complexes, , cycloalkyne platinum(0) complexes, and alkyne complexes M(η 2 -RC 2 R)(PR‘ 3 ) 2 (M = Ni, Pt); , they confirm that rotation of the coordinated cyclohexyne is slow on the NMR time scale. The EI mass spectrum of 2 shows a parent ion at m / z 560, but parent ions were not observed for 1 and 3 .…”

“…Small cyclic alkynes such as cycloheptyne (C 7 H 10 ) and cyclohexyne (C 6 H 8 ) exist only transiently in the free state, but can be stabilized in the form of transition metal complexes of platinum(0), palladium(0), and zirconium(II), such as M(η 2 -C 7 H 10 )L 2 (M = Pt, Pd; L 2 = 2PPh 3 , dppe), − M(η 2 -C 6 H 8 )L 2 (M = Pt, L 2 = 2PPh 3 , − 2P- t -BuPh 2 , 2P- t -Bu 2 Ph, 2PMe 3 , dppe, , dppp, dmpe; M = Pd, L 2 = 2PPh 3 , dppe 4 ), and Zr(η 5 -C 5 H 5 ) 2 (η 2 -C 6 H 8 )(PMe 3 ) . Because complexes of nickel(0) are usually structurally similar to their palladium(0) and platinum(0) counterparts, but are often more air-sensitive and catalytically more active, , we were interested to determine whether cycloalkyne complexes of nickel(0) corresponding to the palladium(0) and platinum(0) complexes and to the η 2 -benzyne nickel(0) complexes Ni(η 2 -C 6 H 4 )L 2 (2L = 2PEt 3 , dcpe) 10,11 could be made.…”