HETEROMETALLIC BORIDE CLUSTERS - FORMATION OF OCTAHEDRAL [M2RU4(CO)16B]- (M=RH OR IR) AND GOLD(I) PHOSPHINE DERIVATIVES - CRYSTAL-STRUCTURES OF [N(PPH3)2][TRANS-IR2RU4-(CO)16B], TRANS-[RH2RU4(CO)16B(MU-3-AUP(C6H11)3)] AND CIS-[IR2RU4(CO)16B(MU-AUP(C6H11)3)]

The reaction of the butterfly cluster [Ru4H(CO)12BH]- with [Rh2(CO)4Cl2] led to the octahedral boride [Rh2Ru4(CO)16B]- 1. In solution, B-11 NMR spectroscopic evidence supports the presence of both cis- and trans-isomers of 1. The trans form is predominant. When treated with [AuCl{P(C6H11)3}], 1 yielded [Rh2Ru4(CO)16B{AuP(C6H11)3}] 3 in two isomeric forms 3a and 3b. Similar reactions occur with other phosphine gold(I) derivatives. The crystal structure of compound 3a has been determined and reveals a trans arrangement of Rh atoms and a face capping AuP(C6H11)3 unit. The anion [Ru4H(CO)12BH]- reacted with [Ir2L4Cl2] (L = cyclooctene or L2 = cycloocta-1,5-diene) under a stream of CO to give [Ir2Ru4(CO)16B]- 2; the crystal structure of 2 has been determined and confirms an octahedral metal framework with trans iridium atoms. Cluster 2 reacted with [AuCl{P(C6H11)3}] to yield [Ir2Ru4(CO)16B-{AuP(C6H11)3}] 4 and crystallographic data for 4 show that the Ir atoms are mutually cis in the octahedral Ir2Ru4 skeleton. The AuP(C6H11)3 unit bridges the Ir-Ir edge. In [Ru4H(CO)12BH]-, the four ruthenium atoms define a butterfly framework with the boron atom lying in a semi-interstitial position. The addition of two Group 9 metal atoms to close up the metal cage to an octahedral one with an M2Ru4 core should initially give a cis isomer. In fact the trans isomer is observed for both 1 and 2, although for 1 both cis and trans isomers are observed by B-11 NMR spectroscopy. Geometrical preferences which accompany the addition of a gold(I) phosphine fragment to anions 1 and 2 to give 3 and 4 respectively are discussed.