Bis(isothiocyanato)bis(phosphine) complexes of group 10 metals: reactivity toward organic isocyanides

Abstract

Treatment of Ni(NCS)₂(PMe₂Ph)₂ with organic isocyanides CN–R gave five-coordinate isocyanide Ni(II) complexes, Ni(CN–R)(NCS)₂(PMe₂Ph)₂ (R = C₆H₃-2,6-Me₂ (1), t-Bu (2)). Interestingly, the corresponding reaction of Ni(NCS)₂(P(n-Pr)₃)₂ with 2 equiv. of CN-t-Bu gave an unusual compound, which exists as an ion pair of the trigonal bipyramidal cation [Ni(P(n-Pr)₃)₂(CN-t-Bu)₃]²⁺ (3) and the dinuclear NCS-bridged anion [Ni(1,3–µ-NCS)(NCS)₃]₂²⁻ (4). In contrast, Pd(NCS)₂(P(n-Pr)₃)₂ underwent substitution with 2 equiv. of CN-t-Bu to give the four-coordinate mono(isocyanide) Pd(II) complex Pd(NCS)(SCN)(CN-t-Bu)(P(n-Pr)₃) (5) via phosphine dissociation. Reactions of M(NCS)₂L₂ (M = Pd, Pt; L = PMe₃, PEt₃, PMePh₂, P(n-Pr)₃) with two equiv. of CN–R (R = t-Bu, i-Pr, C₆H₃-2,6-Me₂) gave the corresponding bis(isocyanide) complexes [M(CN–R)₂(PR₃)₂](SCN)₂ (7–13), except for Pd(NCS)₂(PEt₃)₂ that reacted with CN–R′ (R′ = i-Pr, C₆H₃-2,6-Me₂) and produced the mono(isocyanide) Pd(II) complexes [Pd(CN–R′)(SCN)(PEt₃)₂](SCN) (14 and 15). Finally, treatment of M(NCS)₂(PMe₃)₂ (M = Ni, Pd, Pt) with sterically bulky isocyanide CN–C₆H₃-2,6-i-Pr₂ gave various products, (16–18) depending on the identity of the metal.